TECHNICAL FIELD
[0001] The present invention relates to refrigeration cycle apparatuses. The present invention
particularly relates to a refrigeration cycle apparatus including a volume control
compressor.
BACKGROUND ART
[0002] Volume control compressors capable of varying the suction volume (displacement volume)
have been conventionally known. Although volume control techniques for compressors
had been vigorously studied before widespread use of inverters, the importance of
the volume control techniques was temporarily reduced after high-performance inverters
have become cheaply available. Nowadays, however, the volume control techniques for
compressors are beginning to receive renewed attention in an attempt to achieve further
energy saving. One example of the volume control techniques will be presented with
reference to FIG. 9.
[0003] FIG. 9 is a configuration diagram of an air conditioner described in Patent Literature
1. The air conditioner 600 includes a volume control compressor 622, a four-way valve
623, an outdoor heat exchanger 624, an expansion means 625, an indoor heat exchanger
641, an accumulator 621, a bypass pipe 688, a flow path switching valve 690, a suction
pipe 628, and a discharge pipe 630. A bypass discharge valve (not shown) is provided
at a connecting portion between the volume control compressor 622 and the bypass pipe
688.
[0004] When the air-conditioning load is small, the bypass pipe 688 is connected to the
suction pipe 628 by the flow path switching valve 690. Consequently, a part of the
drawn refrigerant is returned to the suction pipe 628 through the bypass pipe 688,
and a low-volume operation is enabled. On the other hand, when the air-conditioning
load is large, the bypass pipe 688 is connected to the discharge pipe 630 by the flow
path switching valve 690. At this time, the bypass discharge valve is closed by the
refrigerant having a discharge pressure.
CITATION LIST
Patent Literature
SUMMARY OF INVENTION
Technical Problem
[0006] In the case where the volume control described with reference to FIG. 9 is employed,
there is a risk that a large amount of oil flows out of the compressor.
[0007] The present invention is intended to solve such a problem, and aims to provide a
refrigeration cycle apparatus that allows reduction in the amount of an oil flowing
out of a volume control compressor and that can exhibit high machine efficiency (COP
(coefficient of performance) of the refrigeration cycle).
Solution to Problem
[0008] That is, the present disclosure provides a refrigeration cycle apparatus including:
a volume control compressor including a compression chamber, a bypass discharge port
opening into the compression chamber, and a bypass discharge valve that opens and
closes the bypass discharge port, the volume control compressor being capable of varying
a suction volume by discharging a refrigerant, which is drawn into the compression
chamber, from the compression chamber through the bypass discharge port while maintaining
the refrigerant at a suction pressure;
a radiator that cools the refrigerant compressed by the compressor;
an expansion mechanism that expands the refrigerant cooled by the radiator;
an evaporator that heats the refrigerant expanded by the expansion mechanism;
a suction path that directs the refrigerant to be compressed from the evaporator to
the compression chamber;
a discharge path that directs the compressed refrigerant from the compression chamber
to the radiator;
a volume control path connected to the bypass discharge port;
a flow path switching unit that supplies either a discharge pressure of the compressor
or the suction pressure of the compressor as a control pressure to the volume control
path;
a high-pressure introduction path having one end connected to the flow path switching
unit and another end connected to the discharge path;
a low-pressure introduction path having one end connected to the flow path switching
unit and another end connected to the suction path;
a controller that controls the flow path switching unit so as to connect the volume
control path to the low-pressure introduction path when a load on the refrigeration
cycle apparatus is small, and that controls the flow path switching unit so as to
connect the volume control path to the high-pressure introduction path when the load
is large; and
a check valve provided on the high-pressure introduction path, the check valve being
configured to permit a flow of the refrigerant in a direction from the discharge path
to the flow path switching unit and preclude a flow in an opposite direction.
Advantageous Effects of Invention
[0009] According to the refrigeration cycle apparatus of the present disclosure, the high-pressure
introduction path is provided with the check valve. Therefore, even when a high internal
pressure of the compression chamber acts on the bypass discharge port, the internal
pressure of the compression chamber is blocked by the check valve. Since the volume
control path is filled with the refrigerant having a pressure equal to the internal
pressure of the compression chamber, the bypass discharge valve is also closed. Therefore,
excessive discharge of an oil to the refrigeration circuit can be prevented. As a
result, heat transfer in the heat exchanger is improved, and the pressure loss which
occurs when the refrigerant passes through the pipes is reduced, so that the coefficient
of performance (COP) of the refrigeration cycle is increased.
BRIEF DESCRIPTION OF DRAWINGS
[0010]
FIG. 1 is a configuration diagram of a refrigeration cycle apparatus according to
an embodiment 1 of the present invention.
FIG. 2 is a schematic transverse cross-sectional view of a volume control compressor
used in the refrigeration cycle apparatus of FIG. 1.
FIG. 3 is a configuration diagram illustrating the operation of the refrigeration
cycle apparatus of FIG. 1 in a low volume mode.
FIG. 4 is a configuration diagram of a refrigeration cycle apparatus according to
a modification 1.
FIG. 5 is a configuration diagram of a refrigeration cycle apparatus according to
a modification 2.
FIG. 6 is a schematic longitudinal cross-sectional view of a volume control compressor
used in the refrigeration cycle apparatus of FIG. 5.
FIG. 7 is a configuration diagram of a refrigeration cycle apparatus according to
an embodiment 2 of the present invention.
FIG. 8 is a configuration diagram of a refrigeration cycle apparatus according to
a modification 3.
FIG. 9 is a configuration diagram of a conventional air conditioner.
DESCRIPTION OF EMBODIMENTS
[0011] Problems with the conventional volume control will be described in detail. It is
predicted that the problems as discussed below arise in the case where the volume
control described with reference to FIG. 9 is employed. For example, in the case where
the position of the bypass discharge valve is close to the discharge port of the compression
chamber, there is a possibility that the pressure acting on the bypass discharge valve
(the internal pressure of the compression chamber) exceeds the discharge pressure.
This is because a pressure loss occurs in the path from the compression chamber to
the discharge pipe. Therefore, the internal pressure of the compression chamber is
higher than the discharge pressure by the amount of the pressure loss. When the internal
pressure of the compression chamber which acts on the bypass discharge valve exceeds
the discharge pressure, the bypass discharge valve cannot be kept closed.
[0012] In the case where the bypass discharge valve cannot be kept closed, a large amount
of oil flows into the discharge pipe through the bypass pipe, and the amount of the
oil circulating in the refrigeration circuit is increased. The large amount of oil
having flowed out of the compressor inhibits heat transfer in the heat exchanger,
and increases the amount of the pressure loss which occurs when the refrigerant passes
through the pipes, leading to reduction in the efficiency of the refrigeration cycle.
This problem can be solved by the following disclosure.
[0013] A first aspect of the present disclosure provides a refrigeration cycle apparatus
including:
a volume control compressor including a compression chamber, a bypass discharge port
opening into the compression chamber, and a bypass discharge valve that opens and
closes the bypass discharge port, the volume control compressor being capable of varying
a suction volume by discharging a refrigerant, which is drawn into the compression
chamber, from the compression chamber through the bypass discharge port while maintaining
the refrigerant at a suction pressure;
a radiator that cools the refrigerant compressed by the compressor;
an expansion mechanism that expands the refrigerant cooled by the radiator;
an evaporator that heats the refrigerant expanded by the expansion mechanism;
a suction path that directs the refrigerant to be compressed from the evaporator to
the compression chamber;
a discharge path that directs the compressed refrigerant from the compression chamber
to the radiator;
a volume control path connected to the bypass discharge port;
a flow path switching unit that supplies either a discharge pressure of the compressor
or the suction pressure of the compressor as a control pressure to the volume control
path;
a high-pressure introduction path having one end connected to the flow path switching
unit and another end connected to the discharge path;
a low-pressure introduction path having one end connected to the flow path switching
unit and another end connected to the suction path;
a controller that controls the flow path switching unit so as to connect the volume
control path to the low-pressure introduction path when a load on the refrigeration
cycle apparatus is small, and that controls the flow path switching unit so as to
connect the volume control path to the high-pressure introduction path when the load
is large; and
a check valve provided on the high-pressure introduction path, the check valve being
configured to permit a flow of the refrigerant in a direction from the discharge path
to the flow path switching unit and preclude a flow in an opposite direction.
[0014] A second aspect provides the refrigeration cycle apparatus as set forth in the first
aspect, wherein the compressor may further include a suction port and a discharge
port. When the load is small, a part of the refrigerant drawn into the compression
chamber through the suction port can be discharged from the compression chamber through
the bypass discharge port while maintaining the suction pressure, and a remaining
part of the refrigerant drawn into the compression chamber through the suction port
can be compressed in the compression chamber, and then discharged from the compression
chamber through the discharge port. The refrigerant discharged from the compression
chamber through the bypass discharge port is returned to the suction path. Therefore,
unnecessary compression work is not performed by the compressor.
[0015] A third aspect provides the refrigeration cycle apparatus as set forth in the first
or second aspect, wherein the refrigeration cycle apparatus may further include a
relief valve circuit. The high-pressure introduction path may have a first portion
between the check valve and the flow path switching unit, and a second portion between
the check valve and the discharge path. The relief valve circuit may have one end
connected to the first portion and another end connected to the second portion or
the discharge path. With the relief valve circuit, excessive increase in pressure
in the volume control path, the flow path switching unit, and the first portion of
the high-pressure introduction path, can be prevented by diverting the pressure to
the second portion or the discharge path.
[0016] A fourth aspect provides the refrigeration cycle apparatus as set forth in the first
aspect, wherein the compressor may be a hermetic multicylinder compressor further
including: a first compression chamber as the compression chamber and a second compression
chamber; a closed casing having an internal space capable of retaining the refrigerant
compressed in the first compression chamber and the refrigerant compressed in the
second compression chamber; an intermediate chamber that receives the refrigerant
discharged from the first compression chamber through the bypass discharge port; a
first discharge port that allows communication between the intermediate chamber and
the internal space of the closed casing; and a first discharge valve that opens and
closes the first discharge port. The volume control path can be connected to the bypass
discharge port via the intermediate chamber. When the load is small, the refrigerant
drawn into the first compression chamber can be discharged from the first compression
chamber through the bypass discharge port while maintaining the suction pressure,
and can be returned to the suction path through the intermediate chamber, the volume
control path, and the low-pressure introduction path. When the load is large, the
refrigerant drawn into the first compression chamber can be compressed in the first
compression chamber to a pressure higher than the discharge pressure, push and open
the bypass discharge valve and the first discharge valve, and be discharged from the
first compression chamber to the internal space of the closed casing through the bypass
discharge port, the intermediate chamber, and the first discharge port. According
to the fourth aspect, a volume control compressor of the so-called cylinder-selective
type can be provided.
[0017] A fifth aspect provides the refrigeration cycle apparatus as set forth in any one
of the first to fourth aspects, wherein the controller can control the flow path switching
unit so as to connect the volume control path to the low-pressure introduction path
at start-up of the refrigeration cycle apparatus, and can control the flow path switching
unit so as to connect the volume control path to the high-pressure introduction path
after elapse of a predetermined time from the start-up. Carrying out such control
allows the liquid refrigerant to be quickly returned to the suction path even when
the liquid refrigerant has been accumulated in the volume control path. As a result,
generation of abnormal pressure caused by confinement of the liquid refrigerant in
the volume control path can be prevented. That is, it is possible to prevent a situation
where the liquid refrigerant expands due to increase in the temperature of the liquid
refrigerant after the start-up, and thus causes excessive increase in pressure in
the volume control path.
[0018] A sixth aspect provides the refrigeration cycle apparatus as set forth in any one
of the first to fifth aspects, wherein the controller can control the flow path switching
unit so as to connect the volume control path to the low-pressure introduction path
when operation of the refrigeration cycle apparatus is stopped. With this feature,
generation of abnormal pressure caused by confinement of the liquid refrigerant in
the volume control path can be prevented. That is, it is possible to prevent a situation
where the liquid refrigerant expands due to increase in the temperature of the liquid
refrigerant after the start-up, and thus causes excessive increase in pressure in
the volume control path.
[0019] A seventh aspect of the present disclosure provides a refrigeration cycle apparatus
including:
a volume control compressor including a compression chamber, a bypass discharge port
opening into the compression chamber, and a bypass discharge valve that opens and
closes the bypass discharge port, the volume control compressor being capable of varying
a suction volume by discharging a refrigerant, which is drawn into the compression
chamber, from the compression chamber through the bypass discharge port while maintaining
the refrigerant at a suction pressure;
a radiator that cools the refrigerant compressed by the compressor;
an expansion mechanism that expands the refrigerant cooled by the radiator;
an evaporator that heats the refrigerant expanded by the expansion mechanism;
a suction path that directs the refrigerant to be compressed from the evaporator to
the compression chamber;
a discharge path that directs the compressed refrigerant from the compression chamber
to the radiator;
a volume control path connected to the bypass discharge port;
a low-pressure introduction path connected to the suction path;
an on-off valve provided so as to make connection between the low-pressure introduction
path and the volume control path;
a controller that controls the on-off valve so as to connect the volume control path
to the low-pressure introduction path when a load on the refrigeration cycle apparatus
is small, and that controls the on-off valve so as to disconnect the volume control
path from the low-pressure introduction path when the load is large; and
a relief valve circuit having one end connected to the volume control path and another
end connected to the discharge path.
[0020] According to the seventh aspect, the volume control path is connected to the low-pressure
introduction path via the on-off valve. Therefore, it is possible to avoid a situation
where the refrigerant containing a large amount of oil directly flows into the discharge
path of the compressor through the bypass discharge port and the volume control path.
Furthermore, since the relief valve circuit is provided, even when the liquid refrigerant
accumulated temporarily in the volume control path expands due to increase in the
temperature of the liquid refrigerant, and thus causes increase in pressure in the
volume control path, the pressure can be diverted to the discharge path through the
relief valve circuit.
[0021] An eighth aspect of the present disclosure provides a refrigeration cycle apparatus
including:
a volume control compressor including: a first compression chamber; a second compression
chamber; a closed casing having an internal space capable of retaining a refrigerant
compressed in the first compression chamber and the refrigerant compressed in the
second compression chamber; a bypass discharge port opening into the first compression
chamber; a bypass discharge valve that opens and closes the bypass discharge port;
an intermediate chamber that receives the refrigerant discharged from the first compression
chamber through the bypass discharge port; a first discharge port that allows communication
between the intermediate chamber and the internal space of the closed casing; and
a first discharge valve that opens and closes the first discharge port;
a radiator that cools the refrigerant compressed by the compressor;
an expansion mechanism that expands the refrigerant cooled by the radiator;
an evaporator that heats the refrigerant expanded by the expansion mechanism;
a suction path that directs the refrigerant to be compressed from the evaporator to
the first compression chamber and the second compression chamber;
a discharge path that directs the compressed refrigerant from the first compression
chamber and the second compression chamber to the radiator;
a volume control path connected to the bypass discharge port via the intermediate
chamber;
a low-pressure introduction path connected to the suction path;
an on-off valve provided so as to make connection between the low-pressure introduction
path and the volume control path; and
a controller that controls the on-off valve in such a manner that:
- (i) when a load on the refrigeration cycle apparatus is small, the volume control
path is connected to the low-pressure introduction path so that the refrigerant drawn
into the first compression chamber is discharged from the first compression chamber
through the bypass discharge port while maintaining a suction pressure, and is returned
to the suction path through the intermediate chamber, the volume control path, and
the low-pressure introduction path; and
- (ii) when the load is large, the volume control path is disconnected from the low-pressure
introduction path so that the refrigerant drawn into the first compression chamber
is compressed in the first compression chamber to a pressure higher than a discharge
pressure of the compressor, pushes and opens the bypass discharge valve and the first
discharge valve, and is discharged from the first compression chamber to the internal
space of the closed casing through the bypass discharge port, the intermediate chamber,
and the first discharge port.
[0022] According to the eighth aspect, the volume control path is connected to the low-pressure
introduction path via the on-off valve. Therefore, it is possible to avoid a situation
where the refrigerant containing a large amount of oil directly flows into the discharge
path of the compressor through the bypass discharge port and the volume control path.
Furthermore, according to the eighth aspect, formation of a closed space in the refrigeration
circuit can be avoided. Therefore, the pressure in the volume control path cannot
be increased excessively even when the liquid refrigerant fills the volume control
path, and then expands due to increase in the temperature of the liquid refrigerant.
This is because when the pressure in the volume control path is increased, the first
discharge valve is opened, and thus the pressure can be diverted to the internal space
of the closed casing.
[0023] A ninth aspect provides the refrigeration cycle apparatus as set forth in the seventh
or eighth aspect, wherein the controller controls the on-off valve so as to connect
the volume control path to the low-pressure introduction path at start-up of the refrigeration
cycle apparatus, and controls the on-off valve so as to disconnect the volume control
path from the low-pressure introduction path after elapse of a predetermined time
from the start-up. According to the ninth aspect, the same effect as in the sixth
aspect can be obtained.
[0024] A tenth aspect provides the refrigeration cycle apparatus as set forth in any one
of the seventh to ninth aspects, wherein the controller controls the on-off valve
so as to connect the volume control path to the low-pressure introduction path when
operation of the refrigeration cycle apparatus is stopped. With this feature, generation
of abnormal pressure caused by confinement of the liquid refrigerant in the volume
control path can be prevented. That is, it is possible to prevent a situation where
the liquid refrigerant expands due to increase in the temperature of the liquid refrigerant
after the start-up, and thus causes excessive increase in pressure in the volume control
path.
[0025] Hereinafter, embodiments of the present invention will be described with reference
to the drawings. The present invention is not limited by the embodiments described
below.
(Embodiment 1)
[0026] As shown in FIG. 1, a refrigeration cycle apparatus 100 of the present embodiment
includes a volume control compressor 101, a first four-way valve 102, a first heat
exchanger 103, an expansion mechanism 104, a second heat exchanger 105, and an accumulator
106. These components are connected to each other by flow paths 10a to 10f so as to
form a refrigeration circuit. The flow paths 10a to 10f are respectively constituted
by refrigerant pipes.
[0027] The first heat exchanger 103 is a radiator that cools a refrigerant compressed by
the compressor 101 or an evaporator that heats the refrigerant expanded by the expansion
mechanism 104. When the first heat exchanger 103 functions as a radiator, the second
heat exchanger 105 functions as an evaporator. When the first heat exchanger 103 functions
as an evaporator, the second heat exchanger 105 functions as a radiator. The expansion
mechanism 104 has the function of expanding the refrigerant cooled by the radiator,
and is typically constituted by an expansion valve. The expansion mechanism 104 may
be constituted by a positive-displacement expander capable of recovering the expansion
energy of the refrigerant.
[0028] The compressor 101 is a hermetic compressor, and includes a closed casing 1, a motor
2, and a compression mechanism 3. The motor 2 and the compression mechanism 3 are
disposed in the closed casing 1. The closed casing 1 has an internal space 28 capable
of retaining the refrigerant compressed by the compression mechanism 3. That is, the
compressor 101 is a compressor of the so-called high-pressure shell type. The compression
mechanism 3 is connected to the motor 2 by a shaft 4. The compression mechanism 3
is a positive-displacement fluid mechanism, and is driven by the motor 2 so as to
compress the refrigerant.
[0029] As shown in FIG. 2, the compression mechanism 3 includes a suction port 27, a discharge
port 29, a compression chamber 25, a bypass discharge port 16 opening into the compression
chamber 25, and a bypass discharge valve 35 that opens and closes the bypass discharge
port 16. When the compressor 101 is operated in a high volume mode, all of the refrigerant
drawn into the compression chamber 25 through the suction port 27 is compressed in
the compression chamber 25, and is discharged to the internal space 28 of the closed
casing 1 through the discharge port 29. On the other hand, when the compressor 101
is operated in a low volume mode, a part of the refrigerant drawn into the compression
chamber 25 through the suction port 27 pushes and opens the bypass discharge valve
35, and is discharged from the compression chamber 25 through the bypass discharge
port 16. The suction volume of the compressor 101 is varied by switching between the
high volume mode and the low volume mode.
[0030] Specifically, when the compressor 101 is operated in the low volume mode, a part
of the refrigerant drawn into the compression chamber 25 through the suction port
27 is discharged from the compression chamber 25 through the bypass discharge port
16 while maintaining the suction pressure (without being substantially compressed).
The remaining part of the refrigerant drawn into the compression chamber 25 through
the suction port 27 is compressed in the compression chamber 25, and is discharged
from the compression chamber 25 through the discharge port 29. As described later,
the refrigerant discharged from the compression chamber 25 through the bypass discharge
port 16 is returned to the flow path 10e serving as a suction path. Therefore, unnecessary
compression work is not performed by the compressor 101.
[0031] The bypass discharge valve 35 is constituted by a reed valve including a reed 36
and a valve seat 37. The reed 36 and the valve seat 37 are fixed to a cylinder 5 by
a fixing component 38 such as a screw and a bolt. The bypass discharge valve 35 is
opened and closed depending on the pressure difference between the front and back
surfaces of the reed 36. Any of the several discharge valves described in the present
specification can be constituted by a reed valve.
[0032] In addition, the compression mechanism 3 includes the cylinder 5, a piston 8, a vane
9, and a spring 10. An upper bearing and a lower bearing (which are not shown) are
respectively disposed on and under the cylinder 5 so as to close the cylinder 5. The
piston 8 fitted to an eccentric portion 4a of the shaft 4 is disposed inside the cylinder
5 so as to form the compression chamber 25 inside the cylinder 5. A vane groove 24
is formed in the cylinder 5. The vane 9 having one end contacting the outer circumferential
surface of the piston 8 is placed in the vane groove 24. The spring 10 is disposed
in the vane groove 24 so as to push the vane 9 toward the piston 8. The compression
chamber 25 between the cylinder 5 and the piston 8 is divided by the vane 9, and thus
a suction chamber 25a and a compression-discharge chamber 25b are formed. The refrigerant
to be compressed is introduced to the compression chamber 25 (suction chamber 25a)
through the flow path 10f and the suction port 27. The refrigerant having been compressed
is introduced to the internal space 28 of the closed casing 1 from the compression
chamber 25 (compression-discharge chamber 25b) through the discharge port 29. A discharge
valve, which is not shown, is provided on the discharge port 29. The vane 9 may be
integrated with the piston 8. That is, the piston 8 and the vane 9 may be constituted
by a so-called swing piston.
[0033] In the present embodiment, the position of the bypass discharge port 16 is set so
that the suction volume in the low volume mode is 1/2 of the suction volume in the
high volume mode. However, the position of the bypass discharge port 16 is not limited,
and may be set according to the suction volume required in the low volume mode. In
addition, two or more bypass discharge ports 16 may be provided. In this case, the
compressor 101 can be operated at a suction volume selected from a plurality of suction
volumes.
[0034] In the present embodiment, the compressor 101 is a rotary compressor. However, the
type of the compressor 101 is not particularly limited as long as the suction volume
can be varied. Another type of compressor, such as a reciprocating compressor and
a scroll compressor described in Patent Literature 1 (
JP 2008-240699 A), can be used.
[0035] As shown in FIG. 1, the flow path 10a forms a discharge path that directs the refrigerant
compressed by the compressor 101 from the compression chamber 25 to the radiator (the
first heat exchanger 103 or the second heat exchanger 105). The flow path 10e, the
accumulator 106, and the flow path 10f form a suction path that directs the refrigerant
to be compressed from the evaporator (the first heat exchanger 103 or the second heat
exchanger 105) to the compression chamber 25.
[0036] The refrigeration cycle apparatus 100 further includes a volume control path 111,
a second four-way valve 112, a high-pressure introduction path 114, a low-pressure
introduction path 116, a check valve 120, and a controller 117.
[0037] The volume control path 111 is connected to the bypass discharge port 16 of the compressor
101. The second four-way valve 112 is a flow path switching unit that supplies either
the discharge pressure of the compressor 101 or the suction pressure of the compressor
101 as a control pressure to the volume control path 111. The high-pressure introduction
path 114 has one end connected to the second four-way valve 112 and the other end
connected to the flow path 10a. The low-pressure introduction path 116 has one end
connected to the second four-way valve 112 and the other end connected to the flow
path 10e. The check valve 120 is provided on the high-pressure introduction path 114
so as to permit a flow of the refrigerant in a direction from the flow path 10a to
the second four-way valve 112, and preclude a flow in the opposite direction. The
paths 111, 114, and 116 can be respectively constituted by refrigerant pipes.
[0038] In the present embodiment, the second four-way valve 112 having one connection port
closed is used as the flow path switching unit. However, the structure of the flow
path switching unit is not limited as long as either the discharge pressure of the
compressor 101 or the suction pressure of the compressor 101 can be supplied as a
control pressure to the volume control path 111. The other end of the low-pressure
introduction path 116 may be connected to the accumulator 106 or to the flow path
10f.
[0039] The controller 117 controls the second four-way valve 112 so that the suction volume
of the compressor 101 is increased or decreased in accordance with the load on the
refrigeration cycle apparatus 100. Specifically, when the load is small, the controller
117 controls the second four-way valve 112 so as to connect the volume control path
111 to the low-pressure introduction path 116, and when the load is large, the controller
117 controls the second four-way valve 112 so as to connect the volume control path
111 to the high-pressure introduction path 114. The controller 117 can be constituted
by a DSP (Digital Signal Processor) including an A/D conversion circuit, an input/output
circuit, an arithmetic circuit, a storage device, etc. The controller 117 may include
a drive circuit that controls the motor 2 of the compressor 101.
[0040] Next, the operation of the refrigeration cycle apparatus 100 will be described.
[0041] When the motor 2 of the compressor 101 is activated, the compressor 101 draws a low-pressure
gas refrigerant thorough the flow path 10f (suction path), and compresses the refrigerant.
The high-pressure gas refrigerant is discharged to the internal space 28 of the closed
casing 1, and is introduced to the first heat exchanger 103 (radiator) through the
internal space 28 of the closed casing 1, the flow path 10a, the first four-way valve
102, and the flow path 10b. In the first heat exchanger 103, the refrigerant is cooled
and condensed. The high-pressure liquid refrigerant is introduced to the expansion
mechanism 104 from the first heat exchanger 103, and is reduced in pressure by the
function of the expansion mechanism 104. The gas-liquid two-phase refrigerant is introduced
to the second heat exchanger 105 (evaporator) from the expansion mechanism 104, and
is heated and evaporated in the second heat exchanger 105. The gas refrigerant is
drawn into the compressor 101 again through the accumulator 106.
[0042] The compressor 101 is configured to vary the suction volume using the discharge pressure
and the suction pressure. When the second four-way valve 112 is kept in the state
shown in FIG. 1, the discharge pressure of the compressor 101 is supplied to the volume
control path 111. In this case, the bypass discharge valve 35 is closed, and thus
the compressor 101 is operated at a relatively large suction volume (high volume mode).
[0043] When the load on the refrigeration cycle apparatus 100 is decreased, the rotational
speed of the motor 2 of the compressor 101 is reduced by an inverter. Consequently,
the power of the refrigeration cycle apparatus 100 is decreased, and efficient operation
is performed. However, when the load is further decreased, the rotational speed of
the motor 2 reaches the lower limit value, and further follow-up control of the power
becomes difficult.
[0044] When the operation needs to be performed with a lower power, the controller 117 switches
the state of the second four-way valve 112 from the state shown in FIG. 1 to the state
shown in FIG. 3. Accordingly, the volume control path 111 is disconnected from the
high-pressure introduction path 114, and is connected to the low-pressure introduction
path 116. As a result, the suction pressure of the compressor 101 is supplied to the
volume control path 111. The suction pressure of the compressor 101 acts on the bypass
discharge valve 35. In this case, when the volume of the compression chamber 25 is
reduced, the refrigerant in the compression chamber 25 is pushed away by the piston
8, and the bypass discharge valve 35 is accordingly opened. During the period in which
the bypass discharge valve 35 is open, and the bypass discharge port 16 and the compression
chamber 25 communicate with each other, the refrigerant drawn into the compression
chamber 25 is returned to the flow path 10e through the volume control path 111, the
second four-way valve 112, and the low-pressure introduction path 116. That is, the
compressor 101 is operated at a relatively small suction volume (low volume mode).
[0045] Assuming that the rotational speed of the compressor 101 is constant, the amount
of the refrigerant discharged from the compressor 101 in the low volume mode is smaller
than the amount of the refrigerant discharged in the high volume mode. Therefore,
switching of the operation mode between the high volume mode and the low volume mode
can widen the range within which follow-up control of the power is possible, and particularly
can lower the lower limit value.
[0046] In the present embodiment, the high-pressure introduction path 114 is provided with
the check valve 120. In the high volume mode shown in FIG. 1, even when the internal
pressure of the compression chamber 25 exceeds the discharge pressure, and the high-pressure
refrigerant is discharged from the compression chamber 25 through the bypass discharge
port 16, the high-pressure refrigerant is blocked by the check valve 120. The check
valve 120 does not permit a flow from the volume control path 111 to the flow path
10a, and obstructs the high-pressure introduction path 114. Therefore, it is possible
to prevent a situation where the refrigerant containing a large amount of oil is discharged
from the compressor 101, and the large amount of oil circulates in the refrigeration
circuit. As a result, heat transfer in the heat exchangers 103 and 105 is improved,
and the pressure loss which occurs when the refrigerant passes through the flow paths
10a to 10f is reduced, so that the coefficient of performance (COP) of the refrigeration
cycle is increased. The volume control path 111, the second four-way valve 112, and
a portion of the high-pressure introduction path 114, are filled with the refrigerant
compressed in the compression chamber 25 to the maximum pressure. Accordingly, the
bypass discharge valve 35 can also be kept closed.
[0047] In addition, at the start-up of the refrigeration cycle apparatus 100, the controller
117 controls the second four-way valve 112 so as to connect the volume control path
111 to the low-pressure introduction path 116. Then, after elapse of a predetermined
time (e.g., 1 to 5 minutes), the controller 117 controls the second four-way valve
112 so as to connect the volume control path 111 to the high-pressure introduction
path 114. Specifically, when the predetermined time has elapsed after activation of
the motor 2, it is determined whether the operation should be performed in the low
volume mode or in the high volume mode, based on the magnitude of the power required
for the refrigeration cycle apparatus 100. When the operation should be performed
in the high volume mode, the volume control path 111 is connected to the high-pressure
introduction path 114. When the operation should be performed in the low volume mode,
the connection between the volume control path 111 and the low-pressure introduction
path 116 is maintained. That is, at the start-up, preliminary operation is performed
in the low volume mode.
[0048] When the ambient temperature is low, such as in winter, there is a possibility that
the liquid refrigerant is accumulated in the volume control path 111. Even when the
liquid refrigerant is accumulated in the volume control path 111, performing the above
preliminary operation allows the liquid refrigerant to be quickly returned to the
flow path 10e. As a result, generation of abnormal pressure caused by confinement
of the liquid refrigerant in the volume control path 111 can be prevented. That is,
it is possible to prevent a situation where the liquid refrigerant expands due to
increase in the temperature of the liquid refrigerant after the start-up, and thus
causes excessive increase in pressure in the volume control path 111. In addition,
in view of the preliminary operation, the low-pressure introduction path 116 is preferably
connected to the flow path 10e or the accumulator 106. In this case, supply of the
liquid refrigerant to the compressor 101 at the start-up can be prevented.
[0049] The preliminary operation is performed at the start-up of the refrigeration cycle
apparatus 100. The "start-up of the refrigeration cycle apparatus 100" may encompass
restart after a temporary stop. In addition, the preliminary operation can be applied
also to other embodiments and modifications described in the present specification.
[0050] In addition, when the operation of the refrigeration cycle apparatus 100 is stopped,
the controller 117 may control the second four-way valve 112 so as to connect the
volume control path 111 to the low-pressure introduction path 116. Specifically, the
operation of the refrigeration cycle apparatus 100 is desirably stopped in a state
where the volume control path 111 is connected to the low-pressure introduction path
116. In this case, generation of abnormal pressure caused by confinement of the liquid
refrigerant in the volume control path 111 can be prevented. That is, it is possible
to prevent a situation where the liquid refrigerant expands due to increase in the
temperature of the liquid refrigerant after the start-up, and thus causes excessive
increase in pressure in the volume control path 111.
(Modification 1)
[0051] As shown in FIG. 4, a refrigeration cycle apparatus 200 according to a modification
1 is different from the refrigeration cycle apparatus 100 of the embodiment 1 in that
the refrigeration cycle apparatus 200 further includes a relief valve circuit 221.
Hereinafter, common components between the embodiments or modifications described
earlier and the embodiments or modifications described later are denoted by the same
reference characters, and the description thereof is omitted.
[0052] The high-pressure introduction path 114 has a first portion 114a between the check
valve 120 and the second four-way valve 112 (flow path switching unit), and a second
portion 114b between the check valve 120 and the flow path 10a (discharge path). The
relief valve circuit 221 has one end connected to the first portion 114a, and has
the other end connected to the second portion 114b or the flow path 10a so that the
check valve 120 is bypassed. When the difference between the pressure in the first
portion 114a and the pressure in the second portion 114b exceeds a certain value,
the relief valve circuit 221 allows the refrigerant to flow out of the first portion
114a into the flow path 10a (or the second portion 114b), and thus reduces the pressure
in the first portion 114a.
[0053] With the refrigeration cycle apparatus 200, the same effect as provided by the preliminary
operation described in the embodiment 1 is obtained. That is, generation of abnormal
pressure caused by confinement of the liquid refrigerant in the volume control path
111 or the like can be prevented. When the ambient temperature is low, such as in
winter, there is a possibility that the liquid refrigerant is accumulated in the volume
control path 111, the four-way valve 112, and the first portion 114a of the high-pressure
introduction path 114. It is predicted that the phenomenon of accumulation of the
liquid refrigerant in the volume control path 111 or the like occurs when the path
from the bypass discharge valve 35 to the check valve 120 is cooled. There is also
a possibility that the liquid refrigerant is accumulated in the volume control path
111 or the like while the compressor 101 is not in operation. In the presence of the
liquid refrigerant accumulated in a closed space such as the volume control path 111,
there is a possibility that the liquid refrigerant expands due to increase in the
temperature of the liquid refrigerant, and thus causes excessive increase in pressure
in the closed space such as the volume control path 111. With the relief valve circuit
221, excessive increase in pressure in the volume control path 111, the four-way valve
112, and the first portion 114a of the high-pressure introduction path 114, can be
prevented by diverting the pressure to the flow path 10a.
(Modification 2)
[0054] As shown in FIG. 5, a refrigeration cycle apparatus 300 according to a modification
2 is different from the embodiment 1 in that the refrigeration cycle apparatus 300
includes a compressor 301 having a structure different from that of the compressor
101 of the embodiment 1.
[0055] As shown in FIG. 6, the compressor 301 includes the closed casing 1, the motor 2,
and a compression mechanism 30, and is configured as a multicylinder rotary compressor
(two-cylinder compressor in the case of the present modification). The refrigerant
compressed by the compression mechanism 30 is introduced to the flow path 10a thorough
the internal space 28 of the closed casing 1. The compression mechanism 30 has a first
compression chamber 40, a second compression chamber 42, an intermediate chamber 69,
a first discharge port 67, a first discharge valve 63, a second discharge port 71,
a second discharge valve 73, a bypass discharge port 65, and a bypass discharge valve
61.
[0056] The flow path 10a forms a discharge path that directs the refrigerant compressed
by the compressor 301 from the first compression chamber 40 and the second compression
chamber 42 to the radiator (the first heat exchanger 103 or the second heat exchanger
105). The flow path 10e, the accumulator 106, and the flow path 10f, form a suction
path that directs the refrigerant to be compressed from the evaporator (the first
heat exchanger 103 or the second heat exchanger 105) to the first compression chamber
40 and the second compression chamber 42.
[0057] The bypass discharge port 65 opens into the first compression chamber 40. The bypass
discharge valve 61 is provided so as to open and close the bypass discharge port 65.
The intermediate chamber 69 is a space that receives the refrigerant discharged from
the first compression chamber 40 through the bypass discharge port 65. The intermediate
chamber 69 and the internal space 28 of the closed casing 1 can communicate with each
other via the first discharge port 67. The first discharge valve 63 is provided so
as to open and close the first discharge port 67. The volume control path 111 is connected
to the bypass discharge port 65 via the intermediate chamber 69. Thus, in the compressor
301, two discharge valves 61 and 63 are provided on the path from the first compression
chamber 40 to the internal space 28 of the closed casing 1. The volume control path
111 is connected to the space (intermediate chamber 69) between the discharge valve
61 and the discharge valve 63.
[0058] In addition, the compression mechanism 30 has a first cylinder 41, an intermediate
plate 71, a second cylinder 43, a first piston 51, a second piston 53, an upper bearing
46, a lower bearing 48, a muffler 77, and a muffler 75. The first piston 51 is fitted
to a first eccentric portion 4a of the shaft 4 inside the first cylinder 41. The first
compression chamber 40 is formed between the outer circumferential surface of the
first piston 51 and the inner circumferential surface of the first cylinder 41. The
second cylinder 43 is disposed concentrically with the first cylinder 41. The second
piston 53 is fitted to a second eccentric portion 4b of the shaft 4 inside the second
cylinder 43. The second compression chamber 42 is formed between the outer circumferential
surface of the second piston 53 and the inner circumferential surface of the second
cylinder 43.
[0059] The upper bearing 46 and the lower bearing 48 are respectively disposed on the first
cylinder 41 and under the second cylinder 43. The intermediate plate 71 is disposed
between the first cylinder 41 and the second cylinder 43. The first cylinder 41 is
closed by the upper bearing 46 and the intermediate plate 71, and the second cylinder
43 is closed by the intermediate plate 71 and the lower bearing 48. The bypass discharge
port 65, the intermediate chamber 69, and the first discharge port 67 form a path
extending through the upper bearing 46 along the axial direction of the shaft 4. The
muffler 77 is disposed on the upper bearing 46. In the high volume mode, the refrigerant
compressed in the first compression chamber 40 is introduced to the internal space
28 of the closed casing 1 through the bypass discharge port 65, the intermediate chamber
69, the first discharge port 67, and the internal space of the muffler 77. The second
discharge port 71 is formed in the lower bearing 48 in such a manner that a path extending
thorough the lower bearing 48 along the axial direction of the shaft 4 is formed.
The muffler 75 is disposed under the lower bearing 48. The internal space of the muffler
75 communicates with the internal space of the muffler 77 via a vertical path which
is not shown. The refrigerant compressed in the second compression chamber 42 is introduced
to the internal space 28 of the closed casing 1 through the second discharge port
71, the internal space of the muffler 75, the vertical path, and the internal space
of the muffler 77.
[0060] The first compression chamber 40 and the second compression chamber 42 function as
compression chambers that are independent from each other. In the high volume mode,
the refrigerant is compressed in each of the first compression chamber 40 and the
second compression chamber 42. In the low volume mode, the refrigerant is compressed
in the second compression chamber 42, but is not compressed in the first compression
chamber 40. In the low volume mode, since the suction pressure is supplied to the
intermediate chamber 69, the refrigerant drawn into the first compression chamber
40 pushes and opens the bypass discharge valve 61 without being compressed, and is
introduced to the volume control path 111 through the bypass discharge port 65 and
the intermediate chamber 69. Thus, the compressor 301 is configured as a volume control
compressor of the so-called cylinder-selective type.
[0061] Next, the operation of the refrigeration cycle apparatus 300 will be described.
[0062] When the motor 2 is activated, the compressor 301 draws a low-pressure gas refrigerant
through the flow path 10f (suction path), and compresses the refrigerant. The high-pressure
gas refrigerant is discharged to the internal space 28 of the closed casing 1. Specifically,
the refrigerant compressed in the first compression chamber 40 is discharged to the
internal space 28 of the closed casing 1 through the bypass discharge port 65, the
intermediate chamber 69, the first discharge port 67, and the muffler 77. The refrigerant
compressed in the second compression chamber 42 is discharged to the internal space
28 of the closed casing 1 through the second discharge port 71 and the muffler 75.
In the internal space 28, the refrigerant compressed in the first compression chamber
40 merges with the refrigerant compressed in the second compression chamber 42. The
subsequent refrigerant flow is as described in the embodiment 1.
[0063] When the second four-way valve 112 is kept in the state shown in FIG. 5, the discharge
pressure of the compressor 301 is supplied to the volume control path 111 and the
intermediate chamber 69. In this case, the refrigerant drawn into the first compression
chamber 40 is compressed in the first compression chamber 40 to a pressure higher
than the discharge pressure, pushes and opens the bypass discharge valve 61 and the
first discharge valve 63, and is discharged from the first compression chamber 40
to the internal space 28 of the closed casing 1 through the bypass discharge port
65, the intermediate chamber 69, and the first discharge port 67. Since the work of
compressing the refrigerant is performed in both the first compression chamber 40
and the second compression chamber 42, the compressor 301 is operated at a relatively
large suction volume (high volume mode).
[0064] When the load on the refrigeration cycle apparatus 300 is decreased, the rotational
speed of the motor 2 of the compressor 301 is reduced by an inverter. Consequently,
the power of the refrigeration cycle apparatus 300 is decreased, and efficient operation
is performed. However, when the load is further decreased, the rotational speed of
the motor 2 reaches the lower limit value, and further follow-up control of the power
becomes difficult.
[0065] When the operation needs to be performed with a lower power, the controller 117 switches
the state of the second four-way valve 112 from the state shown in FIG. 5 to the state
shown in FIG. 3. Consequently, the volume control path 111 is disconnected from the
high-pressure introduction path 114, and is connected to the low-pressure introduction
path 116. The suction pressure of the compressor 301 is supplied to the volume control
path 111 and the intermediate chamber 69. In this case, the compressor 301 is operated
at a relatively small suction volume (low volume mode).
[0066] In the low volume mode, the bypass discharge valve 61 is constantly open since the
pressure in the intermediate chamber 69 is equal to the suction pressure. Therefore,
the refrigerant drawn into the first compression chamber 40 is discharged from the
first compression chamber 40 to the intermediate chamber 69 through the bypass discharge
port 65 while maintaining the suction pressure (without being substantially compressed).
A high pressure of the internal space 28 of the closed casing 1 is applied to one
surface of the first discharge valve 63, and therefore, the first discharge valve
63 is not opened. As a result, the refrigerant discharged to the intermediate chamber
69 is returned to the flow path 10e (suction path) through the volume control path
111, the second four-way valve 112, and the low-pressure introduction path 116.
[0067] In the high volume mode, the volume control path 111 is connected to the high-pressure
introduction path 114 as shown in FIG. 5. Consequently, the pressure in the intermediate
chamber 69 is made equal to the discharge pressure. However, due to the influence
of inevitable pressure loss, the pressure in the flow path 10a is slightly lower than
the pressure in the internal space 28 of the closed casing 1. In the case where the
pressure in the intermediate chamber 69 is lower than the pressure in the internal
space 28 of the closed casing 1, the first discharge valve 63 is not opened. The refrigerant
discharged to the intermediate chamber 69 fills the volume control path 111, the second
four-way valve 112, and a portion of the high-pressure introduction pipe 114, and
is blocked by the check valve 120. Since the check valve 120 does not permit a flow
from the volume control path 111 to the flow path 10a, the pressures in the volume
control path 111 and the intermediate chamber 69 gradually increase, and exceed the
pressure in the internal space 28 of the closed casing 1. As a result, the first discharge
valve 63 is opened. Thus, in the high volume mode, compression work is performed not
only in the second compression chamber 42 but also in the first compression chamber
40. In addition, it is possible to prevent a situation where the refrigerant containing
a large amount of oil is discharged from the compressor 301, and the large amount
of oil circulates in the refrigeration circuit.
[0068] Furthermore, according to the present modification, any closed space is not formed
in the refrigeration circuit. Therefore, the pressure in the volume control path 111
cannot be increased excessively even when the liquid refrigerant fills the volume
control path 111, the second four-way valve 112, and a portion of the high-pressure
introduction path 114, and then expands due to increase in the temperature of the
liquid refrigerant. When the pressure in the volume control path 111 is increased,
the first discharge valve 63 is opened, ant thus the pressure can be diverted to the
internal space 28 of the closed casing 1.
[0069] According to the present modification, the first compression chamber 40 is located
relatively near the motor 2. Therefore, the bypass path from the first compression
chamber 40 to the volume control path 111 is shortened, and the pressure loss in the
low volume mode can be reduced. However, the bypass discharge port 65 may be provided
in the second compression chamber 42. That is, the compressor 301 may be configured
to selectively disables the second compression chamber 42, instead of the first compression
chamber 40.
(Embodiment 2)
[0070] As shown in FIG. 7, a refrigeration cycle apparatus 400 of the present embodiment
is different from the refrigeration cycle apparatus 100 of the embodiment 1 in that
the refrigeration cycle apparatus 400 includes the relief valve circuit 221 and an
on-off valve 420 serving as means for switching the control pressure. The function
and the effect of the relief valve circuit 221 are as described in the modification
1.
[0071] The on-off valve 420 is provided so as to make connection between the low-pressure
introduction path 116 and the volume control path 111. An electromagnetic valve can
be used as the on-off valve 420. The on-off valve 420 is closed in the high volume
mode, and is opened in the low volume mode. That is, when the load on the refrigeration
cycle apparatus 400 is small, the on-off valve 420 is controlled so as to connect
the volume control path 111 to the low-pressure introduction path 116, and when the
load is large, the on-off valve 420 is controlled so as to disconnect the volume control
path 111 from the low-pressure introduction path 116.
[0072] According to the present embodiment, the volume control path 111 is connected to
the low-pressure introduction path 116 via the on-off valve 420. Therefore, it is
possible to avoid a situation where the refrigerant containing a large amount of oil
directly flows into the discharge path of the compressor 101 through the bypass discharge
port 16 and the volume control path 111.
[0073] Furthermore, also in the refrigeration cycle apparatus 400 of the present embodiment,
there is a possibility that the liquid refrigerant is accumulated in the volume control
path 111 for the reason described in the modification 2. However, even when the liquid
refrigerant expands due to increase in the temperature of the liquid refrigerant,
and thus causes increase in pressure in the volume control path 111, the pressure
can be diverted to the discharge path (flow path 10a) through the relief valve circuit
221.
[0074] In the high volume mode, even when the internal pressure of the compression chamber
25 exceeds the discharge pressure, and the high-pressure refrigerant is discharged
from the compression chamber 25 through the bypass discharge port 16, the high-pressure
refrigerant is blocked by the on-off valve 420. Since the volume control path 111
is filled with the refrigerant compressed in the compression chamber 25 to the maximum
pressure, the bypass discharge valve 35 can be kept closed. Therefore, it is possible
to prevent a situation where the refrigerant containing a large amount of oil is discharged
from the compressor 101, and the large amount of oil circulates in the refrigeration
circuit.
(Modification 3)
[0075] As shown in FIG. 8, a refrigeration cycle apparatus 500 of a modification 3 is different
from the refrigeration cycle apparatus 300 of the modification 2 in that the refrigeration
cycle apparatus 500 includes the on-off valve 420 serving as means for switching the
control pressure. That is, the refrigeration cycle apparatus 500 of the present modification
corresponds to a refrigeration cycle apparatus of the embodiment 2 in which the compressor
101 is replaced by the compressor 301 of the modification 2 and from which the relief
valve circuit 221 is omitted.
[0076] The on-off valve 420 is closed in the high volume mode, and is opened in the low
volume mode. The function of the on-off valve 420 is as described in the embodiment
2. With the refrigeration cycle apparatus 500 of the present modification, both the
advantage of the modification 2 and the advantage of the embodiment 2 can be obtained.
[0077] Also in the embodiment 2 and the modification 3, the preliminary operation as in
the embodiment 1 may be performed. That is, the on-off valve 420 may be controlled
so as to connect the volume control path 111 to the low-pressure introduction path
116 at the start-up of the refrigeration cycle apparatus 400 (or 500), and may then
be controlled so as to disconnect the volume control path 111 from the low-pressure
introduction path 116 after elapse of a predetermined time. That is, the on-off valve
420 is opened at the start-up. In addition, when the operation of the refrigeration
cycle apparatus 400 (or 500) is stopped, the on-off valve 420 may be controlled so
as to connect the volume control path 111 to the low-pressure introduction path 116.
That is, the operation of the refrigeration cycle apparatus 400 (or 500) may be stopped
in a state where the on-off valve 420 is open and where the volume control path 111
is connected to the low-pressure introduction path 116.
INDUSTRIAL APPLICABILITY
[0078] The refrigeration cycle apparatus of the present invention is useful for air conditioners,
refrigerating machines, heaters, hot water dispensers, etc.
1. A refrigeration cycle apparatus comprising:
a volume control compressor comprising a compression chamber, a bypass discharge port
opening into the compression chamber, and a bypass discharge valve that opens and
closes the bypass discharge port, the volume control compressor being capable of varying
a suction volume by discharging a refrigerant, which is drawn into the compression
chamber, from the compression chamber through the bypass discharge port while maintaining
the refrigerant at a suction pressure;
a radiator that cools the refrigerant compressed by the compressor;
an expansion mechanism that expands the refrigerant cooled by the radiator;
an evaporator that heats the refrigerant expanded by the expansion mechanism;
a suction path that directs the refrigerant to be compressed from the evaporator to
the compression chamber;
a discharge path that directs the compressed refrigerant from the compression chamber
to the radiator;
a volume control path connected to the bypass discharge port;
a flow path switching unit that supplies either a discharge pressure of the compressor
or the suction pressure of the compressor as a control pressure to the volume control
path;
a high-pressure introduction path having one end connected to the flow path switching
unit and another end connected to the discharge path;
a low-pressure introduction path having one end connected to the flow path switching
unit and another end connected to the suction path;
a controller that controls the flow path switching unit so as to connect the volume
control path to the low-pressure introduction path when a load on the refrigeration
cycle apparatus is small, and that controls the flow path switching unit so as to
connect the volume control path to the high-pressure introduction path when the load
is large; and
a check valve provided on the high-pressure introduction path, the check valve being
configured to permit a flow of the refrigerant in a direction from the discharge path
to the flow path switching unit and preclude a flow in an opposite direction.
2. The refrigeration cycle apparatus according to claim 1, wherein
the compressor further comprises a suction port and a discharge port, and
when the load is small, a part of the refrigerant drawn into the compression chamber
through the suction port is discharged from the compression chamber through the bypass
discharge port while maintaining the suction pressure, and a remaining part of the
refrigerant drawn into the compression chamber through the suction port is compressed
in the compression chamber, and is discharged from the compression chamber through
the discharge port.
3. The refrigeration cycle apparatus according to claim 1, further comprising a relief
valve circuit, wherein
the high-pressure introduction path has a first portion between the check valve and
the flow path switching unit, and a second portion between the check valve and the
discharge path, and
the relief valve circuit has one end connected to the first portion and another end
connected to the second portion or the discharge path.
4. The refrigeration cycle apparatus according to claim 1, wherein
the compressor is a hermetic multicylinder compressor further comprising: a first
compression chamber as the compression chamber and a second compression chamber; a
closed casing having an internal space capable of retaining the refrigerant compressed
in the first compression chamber and the refrigerant compressed in the second compression
chamber; an intermediate chamber that receives the refrigerant discharged from the
first compression chamber through the bypass discharge port; a first discharge port
that allows communication between the intermediate chamber and the internal space
of the closed casing; and a first discharge valve that opens and closes the first
discharge port,
the volume control path is connected to the bypass discharge port via the intermediate
chamber,
when the load is small, the refrigerant drawn into the first compression chamber is
discharged from the first compression chamber through the bypass discharge port while
maintaining the suction pressure, and is returned to the suction path through the
intermediate chamber, the volume control path, and the low-pressure introduction path,
and
when the load is large, the refrigerant drawn into the first compression chamber is
compressed in the first compression chamber to a pressure higher than the discharge
pressure, pushes and opens the bypass discharge valve and the first discharge valve,
and is discharged from the first compression chamber to the internal space of the
closed casing through the bypass discharge port, the intermediate chamber, and the
first discharge port.
5. The refrigeration cycle apparatus according to claim 1, wherein the controller controls
the flow path switching unit so as to connect the volume control path to the low-pressure
introduction path at start-up of the refrigeration cycle apparatus, and controls the
flow path switching unit so as to connect the volume control path to the high-pressure
introduction path after elapse of a predetermined time from the start-up.
6. The refrigeration cycle apparatus according to claim 1, wherein the controller controls
the flow path switching unit so as to connect the volume control path to the low-pressure
introduction path when operation of the refrigeration cycle apparatus is stopped.
7. A refrigeration cycle apparatus comprising:
a volume control compressor comprising a compression chamber, a bypass discharge port
opening into the compression chamber, and a bypass discharge valve that opens and
closes the bypass discharge port, the volume control compressor being capable of varying
a suction volume by discharging a refrigerant, which is drawn into the compression
chamber, from the compression chamber through the bypass discharge port while maintaining
the refrigerant at a suction pressure;
a radiator that cools the refrigerant compressed by the compressor;
an expansion mechanism that expands the refrigerant cooled by the radiator;
an evaporator that heats the refrigerant expanded by the expansion mechanism;
a suction path that directs the refrigerant to be compressed from the evaporator to
the compression chamber;
a discharge path that directs the compressed refrigerant from the compression chamber
to the radiator;
a volume control path connected to the bypass discharge port;
a low-pressure introduction path connected to the suction path;
an on-off valve provided so as to make connection between the low-pressure introduction
path and the volume control path;
a controller that controls the on-off valve so as to connect the volume control path
to the low-pressure introduction path when a load on the refrigeration cycle apparatus
is small, and that controls the on-off valve so as to disconnect the volume control
path from the low-pressure introduction path when the load is large; and
a relief valve circuit having one end connected to the volume control path and another
end connected to the discharge path.
8. A refrigeration cycle apparatus comprising:
a volume control compressor comprising: a first compression chamber; a second compression
chamber; a closed casing having an internal space capable of retaining a refrigerant
compressed in the first compression chamber and the refrigerant compressed in the
second compression chamber; a bypass discharge port opening into the first compression
chamber; a bypass discharge valve that opens and closes the bypass discharge port;
an intermediate chamber that receives the refrigerant discharged from the first compression
chamber through the bypass discharge port; a first discharge port that allows communication
between the intermediate chamber and the internal space of the closed casing; and
a first discharge valve that opens and closes the first discharge port;
a radiator that cools the refrigerant compressed by the compressor;
an expansion mechanism that expands the refrigerant cooled by the radiator;
an evaporator that heats the refrigerant expanded by the expansion mechanism;
a suction path that directs the refrigerant to be compressed from the evaporator to
the first compression chamber and the second compression chamber;
a discharge path that directs the compressed refrigerant from the first compression
chamber and the second compression chamber to the radiator;
a volume control path connected to the bypass discharge port via the intermediate
chamber;
a low-pressure introduction path connected to the suction path;
an on-off valve provided so as to make connection between the low-pressure introduction
path and the volume control path; and
a controller that controls the on-off valve in such a manner that:
(i) when a load on the refrigeration cycle apparatus is small, the volume control
path is connected to the low-pressure introduction path so that the refrigerant drawn
into the first compression chamber is discharged from the first compression chamber
through the bypass discharge port while maintaining a suction pressure, and is returned
to the suction path through the intermediate chamber, the volume control path, and
the low-pressure introduction path; and
(ii) when the load is large, the volume control path is disconnected from the low-pressure
introduction path so that the refrigerant drawn into the first compression chamber
is compressed in the first compression chamber to a pressure higher than a discharge
pressure of the compressor, pushes and opens the bypass discharge valve and the first
discharge valve, and is discharged from the first compression chamber to the internal
space of the closed casing through the bypass discharge port, the intermediate chamber,
and the first discharge port.
9. The refrigeration cycle apparatus according to claim 7, wherein the controller controls
the on-off valve so as to connect the volume control path to the low-pressure introduction
path at start-up of the refrigeration cycle apparatus, and controls the on-off valve
so as to disconnect the volume control path from the low-pressure introduction path
after elapse of a predetermined time from the start-up.
10. The refrigeration cycle apparatus according to claim 7, wherein the controller controls
the on-off valve so as to connect the volume control path to the low-pressure introduction
path when operation of the refrigeration cycle apparatus is stopped.