Technical Field
[0001] The present invention relates to a multi-type air conditioner in which a plurality
of indoor units are connected in parallel to an outdoor unit and to a control method
for the multi-type air conditioner.
Background Art
[0002] In a conventional multi-type air conditioner, an expansion valve is controlled so
as to be open-loop controlled for a predetermined period of time at a starting time
and so as to be zone controlled thereafter. Specifically, at the starting time, for
a predetermined period of time during which the state of the refrigerant becomes stable,
the air conditioner is operated with the degree of opening of the electronic expansion
valve being set in proportion to the rotational speed of the compressor by using the
outside air temperature, the discharge degree of superheat, and the suction degree
of superheat as parameters. After that, the degree of opening of the electronic expansion
valve is zone controlled to perform feedback control such that the degree of superheat
falls in a target zone. Thus, an appropriate operating point is maintained, and the
air conditioner is operated with high COP (coefficient of performance) (for example,
see PTL 1).
[0003] PTL 2 proposes a technique in which, at the starting time of a heating operation,
an initial degree of opening of an electronic expansion valve, which is uniformly
set based on the indoor temperature and the outdoor temperature, is corrected based
on the starting state of the air conditioner at the starting time to reduce the rising
time for the next starting time, thereby improving quick heating. Furthermore, PTL
3 proposes that, in an air conditioner in which the degree of opening of an electronic
expansion valve is zone controlled such that the discharge degree of superheat of
the refrigerant becomes a target degree of superheat, the target degree of superheat
be corrected so as to be reduced in a stepwise fashion as the discharge refrigerant
temperature is increased, thereby preventing the compressor from being superheated
and allowing the life of the compressor to be
EP-A-2 261 580 discloses a multi-type air conditioner according to the preamble of claim1.
Citation List
Patent Literature
[0004]
{PTL 1} Japanese Unexamined Patent Application, Publication No. 2005-291553
{PTL 2} Publication of Japanese Patent No. 3546544
{PTL 3} Publication of Japanese Patent No. 3495486
Summary of Invention
Technical Problem
[0005] However, in the above-described conventional techniques, depending on the number
of indoor units connected to the outdoor unit or the capacity of heat exchangers thereof,
the difference in the required refrigerant amount between cooling and heating operations
is increased. Therefore, only by throttling the expansion valve corresponding to each
room, it is difficult to perform appropriate distribution of the refrigerant and to
control the operation of the entire system at an appropriate operating point. During
the heating operation, surplus refrigerant is accumulated in the indoor heat exchangers
to increase the degree of supercooling. As a result, to satisfy the required performance,
it is necessary to increase the rotational frequency of the compressor, thus causing
an inefficient operation.
[0006] Furthermore, in open-loop control during the heating operation, the air conditioner
is operated with the degree of opening of the electronic expansion valve being set
at a certain degree of opening calculated based on particular parameters. Therefore,
operations in which the degree of opening is over-throttled and over-relaxed may be
repeated depending on the operating conditions, thus causing a delay in switching
over to an optimum operating point and making the operation of the compressor less
stable, in some cases, and undermining high-COP operation.
[0007] The present invention has been made in view of such circumstances, and an object
thereof is to provide a multi-type air conditioner and a control method therefor,
in which it is possible to swiftly reach an ideal zone-control region at the switchover
from open-loop control to zone control and to operate the air conditioner with high
COP while ensuring the stable operation of the compressor.
{Solution to Problem}
[0008] In order to solve the above-described problems, the multi-type air conditioner and
the control method therefor of the present invention employ the following solutions.
[0009] Specifically, a first aspect of the present invention provides a multi-type air conditioner
in which a plurality of indoor units are connected in parallel to a single outdoor
unit, and a closed-cycle refrigerant circuit is formed of a compressor, a four-way
switching valve, an outdoor heat exchanger, a first electronic expansion valve, a
receiver, a plurality of second electronic expansion valves connected in parallel
to a plurality of indoor heat exchangers, and the plurality of the indoor heat exchangers
connected in parallel to each other, in which the first electronic expansion valve
is open-loop controlled for a predetermined period of time at a degree of opening
calculated based on particular parameters at a starting time of a heating operation
and at a time of a change in the number of operated indoor units ; in which the first
electronic expansion valve is then switched over to zone control in which a discharge
degree of superheat is controlled so as to fall within a target zone; and in which
the first electronic expansion valve is provided with an expansion-valve control section
that corrects, when a temperature deviation of the discharge degree of superheat with
respect to the target zone and a time variation of the discharge degree of superheat
are large at the switchover to zone control, a degree of opening of the first electronic
expansion valve for the next open-loop control in response thereto.
[0010] In the multi-type air conditioner according to the first aspect of the present invention,
which includes the first electronic expansion valve that is zone controlled such that
the discharge degree of superheat of the refrigerant falls within a target zone, in
addition to the plurality of second electronic expansion valves that individually
control the volumes of the refrigerant for the plurality of the indoor heat exchangers,
the first electronic expansion valve is open-loop controlled for the predetermined
period of time at the degree of opening calculated based on particular parameters
at the starting time of a heating operation and at the time of a change in the number
of operated indoor units; the first electronic expansion valve is then switched over
to zone control in which the discharge degree of superheat is controlled so as to
fall within the target zone; and the first electronic expansion valve is provided
with the expansion-valve control section, which, when a temperature deviation of the
discharge degree of superheat with respect to the target zone and a time variation
of the discharge degree of superheat are large at the switchover to zone control,
corrects the degree of opening of the heating electronic expansion valve for the next
open-loop control in response thereto. In open-loop control during the heating operation,
the air conditioner is operated with the degree of opening of the first electronic
expansion valve being set at a certain degree of opening calculated based on particular
parameters; therefore, operations in which the degree of opening is over-throttled
and over-relaxed may be repeated depending on the operating conditions, thus causing
a delay in switching over to an optimum operating point, in some cases. However, when
the temperature deviation of the discharge degree of superheat with respect to the
target zone and the time variation of the discharge degree of superheat are large
at the switchover to zone control after a predetermined period of time has elapsed,
the degree of opening for the next open-loop control is corrected in response thereto.
Thus, if a similar operating point appears in the operation thereafter, it is possible
to correct the degree of opening of the first electronic expansion valve in open-loop
control to an appropriate degree of opening. Therefore, it is possible to swiftly
reach the optimum operating point, that is, the ideal zone-control region, at the
switchover from open-loop control to zone control and to operate the air conditioner
with high COP while ensuring the stable operation of the compressor.
[0011] Furthermore, in the multi-type air conditioner according to the first aspect of the
present invention, in the expansion-valve control section, the degree of opening of
the first electronic expansion valve in the open-loop control is calculated by using
at least an outside air temperature and a capacity of the plurality of the indoor
heat exchangers, as the parameters.
[0012] In the multi-type air conditioner, the difference in the required refrigerant amount
between cooling and heating operations is increased. However, according to the first
aspect of the present invention, in the expansion-valve control section, the degree
of opening of the first electronic expansion valve in open-loop control is calculated
by using at least the outside air temperature and the capacity of the plurality of
the indoor heat exchangers as the parameters. Therefore, during the heating operation,
the operating point of the entire system is adjusted by the first electronic expansion
valve, and the surplus refrigerant produced during the heating operation is held in
the receiver, thereby making it possible to ensure appropriate degrees of supercooling
at the respective indoor heat exchangers, and the degree of opening of the first electronic
expansion valve is controlled by using at least the outside air temperature and the
capacity of the plurality of the indoor heat exchangers as the parameters, thereby
making it possible to set the degree of opening of the first electronic expansion
valve in open-loop control to a more appropriate degree of opening. Therefore, even
when the capacity of the indoor heat exchangers is changed depending on the connected
indoor units, it is possible to swiftly attain the optimum operating point at the
switchover to zone control to reduce the time to reach the ideal zone-control region,
and it is possible to operate the air conditioner with high COP while ensuring the
stable operation of the compressor.
[0013] Furthermore, in the multi-type air conditioner according to the first aspect of the
present invention, in the expansion-valve control section, a correction coefficient
for the degree of opening of the first electronic expansion valve is determined according
to an outside air temperature and a capacity of the plurality of the indoor heat exchangers
of the indoor units connected to the outdoor unit.
[0014] According to the first aspect of the present invention, in the expansion-valve control
section, the correction coefficient for the degree of opening of the first electronic
expansion valve is determined based on the outside air temperature and the capacity
of the plurality of the indoor heat exchangers of the indoor units connected to the
outdoor unit. Therefore, when the temperature deviation of the discharge degree of
superheat with respect to the target zone and the time variation of the discharge
degree of superheat are large at the switchover to zone control, the correction coefficient
that is changed based on the outside air temperature and the capacity of the plurality
of the indoor heat exchangers is accordingly updated, thereby making it possible to
reflect the updated correction coefficient in calculating the degree of opening of
the first electronic expansion valve for the next open-loop control. Therefore, if
a similar operating point appears in the operation thereafter, it is possible to correct
the degree of opening of the first electronic expansion valve to an appropriate operating
point with this correction coefficient to swiftly reach the ideal zone-control region
at the switchover to zone control, and to operate the air conditioner with high COP
while ensuring the stable operation of the compressor.
[0015] Furthermore, in the multi-type air conditioner according to the first aspect of the
present invention, in the expansion-valve control section, a correction coefficient
for the degree of opening of the first electronic expansion valve is increased or
decreased when a percentage at which the temperature deviation of the discharge degree
of superheat with respect to the target zone and the time variation of the discharge
degree of superheat, calculated at sampling intervals, are equal to or higher than
a predetermined value or are equal to or lower than a predetermined value that exceeds
a predetermined percentage, at the switchover to zone control.
[0016] According to the first aspect of the present invention, in the expansion-valve control
section, the correction coefficient for the degree of opening of the first electronic
expansion valve is increased or decreased when the percentage at which the temperature
deviation of the discharge degree of superheat with respect to the target zone and
the time variation of the discharge degree of superheat, calculated at sampling intervals,
are equal to or higher than a predetermined value or are equal to or lower than a
predetermined value that exceeds a predetermined percentage, at the switchover to
zone control. Thus, by increasing or decreasing this correction coefficient, it is
possible to prevent a situation in which, at the switchover to zone control, the degree
of opening of the first electronic expansion valve is over-throttled, thus making
the discharge degree of superheat overshoot the target zone and causing hunting, or
is over-relaxed, thus causing a delay in reaching the target zone. Therefore, it is
possible to set the degree of opening of the first electronic expansion valve in open-loop
control to an appropriate degree of opening to swiftly reach the ideal zone-control
region at the switchover to zone control, and to ensure the stable operation of the
compressor.
[0017] Furthermore, a second aspect of the present invention provides a control method for
a multi-type air conditioner in which a plurality of indoor units are connected in
parallel to a single outdoor unit, and a closed-cycle refrigerant circuit is formed
of a compressor, a four-way switching valve, an outdoor heat exchanger, a first electronic
expansion valve, a receiver, a plurality of second electronic expansion valves connected
in parallel to a plurality of indoor heat exchangers, and the plurality of the indoor
heat exchangers connected in parallel to each other, the control method including:
performing open-loop control for the first electronic expansion valve for a predetermined
period of time at a degree of opening calculated based on particular parameters, at
a starting time of a heating operation and at a time of a change in the number of
operated indoor units; switching over to zone control in which a discharge degree
of superheat is controlled so as to fall within a target zone; and correcting, when
a temperature deviation of the discharge degree of superheat with respect to the target
zone and a time variation of the discharge degree of superheat are large at the switchover
to zone control, the degree of opening of the first electronic expansion valve for
the next open-loop control in response thereto.
[0018] In the multi-type air conditioner according to the second aspect of the present
invention, which includes the first electronic expansion valve that is zone controlled
such that the discharge degree of superheat of the refrigerant falls within a target
zone, in addition to the plurality of second electronic expansion valves that individually
control the volumes of the refrigerant for the plurality of the indoor heat exchangers,
the first electronic expansion valve is open-loop controlled for the predetermined
period of time at the degree of opening calculated based on particular parameters
at the starting time of a heating operation and at the time of a change in the number
of operated indoor units; and the first electronic expansion valve is then switched
over to zone control in which the discharge degree of superheat is controlled so as
to fall within the target zone; and, when the temperature deviation of the discharge
degree of superheat with respect to the target zone and the time variation of the
discharge degree of superheat are large at the switchover to zone control, the degree
of opening of the first electronic expansion valve for the next open-loop control
is corrected in response thereto. In open-loop control during the heating operation,
the air conditioner is operated with the degree of opening of the first electronic
expansion valve being set at a certain degree of opening calculated based on particular
parameters; therefore, operations in which the degree of opening is over-throttled
and over-relaxed may be repeated depending on the operating conditions, thus causing
a delay in switching over to an optimum operating point, in some cases. However, when
the temperature deviation of the discharge degree of superheat with respect to the
target zone and the time variation of the discharge degree of superheat are large
at the switchover to zone control after a predetermined period of time has elapsed,
the degree of opening for the next open-loop control is corrected in response thereto.
Thus, if a similar operating point appears in the operation thereafter, it is possible
to correct the degree of opening of the first electronic expansion valve in open-loop
control to an appropriate degree of opening. Therefore, it is possible to swiftly
reach the optimum operating point, that is, the ideal zone-control region, at the
switchover from open-loop control to zone control and to operate the air conditioner
with high COP while ensuring the stable operation of the compressor.
Advantageous Effects of Invention
[0019] According to the multi-type air conditioner and the control method therefor of the
present invention, in open-loop control during the heating operation, the air conditioner
is operated with the degree of opening of the first electronic expansion valve being
set at a certain degree of opening calculated based on particular parameters; therefore,
operations in which the degree of opening is over-throttled and over-relaxed may be
repeated depending on the operating conditions, thus causing a delay in switching
over to an optimum operating point, in some cases. However, when the temperature deviation
of the discharge degree of superheat with respect to the target zone and the time
variation of the discharge degree of superheat are large at the switchover to zone
control after a predetermined period of time has elapsed, the degree of opening for
the next open-loop control is corrected in response thereto. Thus, if a similar operating
point appears in the operation thereafter, it is possible to correct the degree of
opening of the first electronic expansion valve in open-loop control to an appropriate
degree of opening. Therefore, it is possible to swiftly reach the optimum operating
point, that is, the ideal zone-control region, at the switchover from open-loop control
to zone control and to operate the air conditioner with high COP while ensuring the
stable operation of the compressor.
Brief Description of Drawings
[0020]
Fig. 1 is a configuration diagram (refrigerant circuit diagram) of a multi-type air
conditioner according to one embodiment of the present invention.
Fig. 2 is a diagram for explaining the operation of a heating electronic expansion
valve of the multi-type air conditioner shown in Fig. 1.
Fig. 3 is a diagram for explaining the operation of the heating electronic expansion
valve of the multi-type air conditioner shown in Fig. 1, at a switchover from open-loop
control to zone control.
Fig. 4 is a table showing an example correction coefficient a used in open-loop control
for the heating electronic expansion valve of the multi-type air conditioner shown
in Fig. 1.
Fig. 5 is a table showing an example correction coefficient b used in open-loop control
for the heating electronic expansion valve of the multi-type air conditioner shown
in Fig. 1.
Fig. 6 is a table showing an example correction coefficient c used in open-loop control
for the heating electronic expansion valve of the multi-type air conditioner shown
in Fig. 1.
Fig. 7 is a table showing an example correction coefficient d used in open-loop control
for the heating electronic expansion valve of the multi-type air conditioner shown
in Fig. 1.
Fig. 8 is a table showing an example correction coefficient Z4 used in open-loop control for the heating electronic expansion valve of the multi-type
air conditioner shown in Fig. 1.
Fig. 9 is a table showing a calculation example of condenser performance (heat exchanger
capacity) of a plurality of indoor heat exchangers connected to the multi-type air
conditioner shown in Fig. 1.
Fig. 10 is an outside-air-temperature setting diagram used to obtain a correction
coefficient used in open-loop control for the heating electronic expansion valve of
the multi-type air conditioner shown in Fig. 1.
Fig. 11 is a table showing an example case where a control pulse is given in zone
control to the heating electronic expansion valve of the multi-type air conditioner
shown in Fig. 1.
Description of Embodiments
[0021] One embodiment of the present invention will be described below with reference to
Fig. 1 to Fig. 11.
[0022] Fig. 1 is a configuration diagram (refrigerant circuit diagram) of a multi-type air
conditioner according to the embodiment of the present invention. Fig. 2 is a diagram
for explaining the operation of a heating electronic expansion valve of the multi-type
air conditioner. Fig. 3 is a diagram for explaining the operation of the heating electronic
expansion valve at a switchover from open-loop control to zone control.
[0023] A multi-type air conditioner 1 has a configuration in which a plurality of (six in
this example, but the number of indoor units is not limited thereto) indoor units
3A to 3F are connected in parallel to a single outdoor unit 2.
[0024] In the outdoor unit 2, a compressor 4; an oil separator 5; a four-way switching valve
6; an outdoor heat exchanger 7; a first electronic expansion valve (EEVH) 8; a receiver
9; individual-room second electronic expansion valves (EEVs) 10A to 10F connected
in parallel to each other, corresponding to the indoor units 3A to 3F; sound-damping
capillary tubes 11A to 11F; strainers 12A to 12F; liquid-side actuating valves 13A
to 13F; gas-side actuating valves 14A to 14F; a header 15; a first accumulator 16;
and a second accumulator 17 are provided and are sequentially connected with refrigerant
pipes, thus forming an outdoor-side refrigerant circuit 18, as is well known.
[0025] With respect to the above-described outdoor unit 2, indoor heat exchangers 19A to
19F of the plurality of the indoor units 3A to 3F are connected to the liquid-side
actuating valves 13A to 13F and the gas-side actuating valves 14A to 14F via piping
joints 20A to 20F and piping joints 21A to 21F, respectively, thereby forming a single-system
closed-cycle refrigerant circuit 22 serving as the multi-type air conditioner 1. Blower
fans (not shown) are provided for the outdoor heat exchanger 7 and the indoor heat
exchangers 19A to 19F to make outside air and air in the rooms circulate to the respective
heat exchangers.
[0026] In the multi-type air conditioner 1, during a cooling operation, a refrigerant compressed
in the compressor 4 is circulated via the oil separator 5, the four-way switching
valve 6, the outdoor heat exchanger 7, the first electronic expansion valve 8, the
receiver 9, the second electronic expansion valves 10A to 10F, the sound-damping capillary
tubes 11A to 11F, the strainers 12A to 12F, the liquid-side actuating valves 13A to
13F, the indoor heat exchangers 19A to 19F, the gas-side actuating valves 14A to 14F,
the header 15, the four-way switching valve 6, the first accumulator 16, and the second
accumulator 17. While circulating, the refrigerant is condensed in the outdoor heat
exchanger 7, is reduced in pressure in the first electronic expansion valve 8 and
the second electronic expansion valves 10A to 10F, and is then evaporated by absorbing
heat in the indoor heat exchangers 19A to 19F, thereby cooling indoor air at the indoor
heat exchangers 19A to 19F and using the cooled air for indoor cooling.
[0027] On the other hand, during a heating operation, the circulation direction of the refrigerant
is switched by the four-way switching valve 6. The refrigerant compressed in the compressor
4 is circulated via the oil separator 5, the four-way switching valve 6, the header
15, the gas-side actuating valves 14A to 14F, the indoor heat exchangers 19A to 19F,
the liquid-side actuating valves 13A to 13F, the strainers 12A to 12F, the sound-damping
capillary tubes 11A to 11F, the second electronic expansion valves 10A to 10F, the
receiver 9, the first electronic expansion valve 8, the outdoor heat exchanger 7,
the four-way switching valve 6, the first accumulator 16, and the second accumulator
17. While circulating, the refrigerant is condensed by releasing heat in the outdoor
heat exchanger 7, is reduced in pressure in the second electronic expansion valves
10A to 10F and the first electronic expansion valve 8, and is then evaporated in the
outdoor heat exchanger 7, thereby heating indoor air at the indoor heat exchangers
19A to 19F and using the heated air for indoor heating.
[0028] In the above-described multi-type air conditioner 1, the first electronic expansion
valve 8 and the second electronic expansion valves 10A to 10F are controlled by an
expansion-valve control section 24 of an outdoor controller 23, as described below.
[0029] The first electronic expansion valve 8 and the second electronic expansion valves
10A to 10F are put under normal control or transient control. The transient control
is control performed within a predetermined period of time (for example, three minutes)
after the compressor 4 is turned on from the OFF state or within a predetermined period
of time (for example, three minutes) after the number of operated units among the
plurality of the indoor units 3A to 3F is changed. The normal control is control performed
when the transient control is not performed.
[0030] During the cooling operation, in the transient control, the second electronic expansion
valves 10A to 10F are set at degrees of opening corresponding to the indoor target
rotational speeds for the respective rooms, to control the volumes of circulating
refrigerant for the respective indoor heat exchangers 19A to 19F. The first electronic
expansion valve 8 is open-loop controlled at the degree of opening calculated by Formula
(1), in which the actual rotational speed of the compressor 4 is corrected based on
the outside air temperature, the suction degree of superheat, and the discharge degree
of superheat. Furthermore, in the normal control, the first electronic expansion valve
8 is zone controlled such that a discharge degree of superheat TDSH obtained from
the difference between the detected value from a discharge temperature sensor 25 and
the detected value from an outdoor heat-exchanger sensor 26 falls within a target
zone.

wherein
a, b: correction coefficients determined based on the outside air temperature;
Z2: a correction coefficient used to maintain an appropriate value of the suction degree
of superheat of the entire system and aimed at stabilizing the open-loop control during
the transient time;
Z3: a correction coefficient used to maintain an appropriate value of the discharge
degree of superheat of the entire system; and
N: the actual rotational speed of the compressor 4.
[0031] Similarly, during the heating operation, in the transient control, the second electronic
expansion valves 10A to 10F are set at degrees of opening corresponding to the indoor
target rotational speeds for the respective rooms, to control the volumes of circulating
refrigerant for the respective indoor heat exchangers 19A to 19F. The first electronic
expansion valve 8 is open-loop controlled at the degree of opening calculated by Formula
(2), in which the actual rotational speed of the compressor 4 is corrected based on
the outside air temperature, the capacity of the plurality of the indoor heat exchangers,
the number of stopped units, the presence or absence of a large wall-type unit that
includes a high-capacity indoor heat exchanger, the suction degree of superheat, and
the discharge degree of superheat. Furthermore, during the heating operation, in the
normal control, the first electronic expansion valve 8 is zone controlled such that
the discharge degree of superheat TDSH of the refrigerant obtained from the detected
value from the discharge temperature sensor 25 and the detected value from a high-pressure
pressure sensor 27 falls within a target zone.

wherein
a, b: correction coefficients determined based on the outside air temperature and
the capacity of the indoor heat exchangers;
c: the sum of α pulses corresponding to the number of stopped units;
d: a correction coefficient determined based on the temperature deviation of the discharge
degree of superheat with respect to the target zone and the time variation of the
discharge degree of superheat at the switchover from open-loop control to zone control;
Z2: a correction coefficient used to maintain an appropriate value of the suction degree
of superheat of the entire system and aimed at stabilizing the open-loop control during
the transient time;
Z3: a correction coefficient used to maintain an appropriate value of the discharge
degree of superheat of the entire system;
Z4: a correction coefficient determined based on the presence or absence of a large
wall-type unit that includes a high-capacity indoor heat exchanger; and
N: the actual rotational speed of the compressor 4.
[0032] Fig. 2 is the diagram for explaining the operation, in which the first electronic
expansion valve (EEVH) 8 is open-loop controlled in transient control, which is performed
when the compressor 4 is turned on from the OFF state or when the number of operated
units among the indoor units 3A to 3F is changed, and is zone controlled in the normal
control, which is performed when the transient control is not performed. The degree
of opening of the first electronic expansion valve 8 in zone control is obtained by
adding the degree of opening set in the zone control to the degree of opening set
in the open-loop control.
[0033] Here, during the heating operation, in the open-loop control, the degree of opening
of the first electronic expansion valve (EEVH) 8 is controlled by using the capacity
of the plurality of the indoor heat exchangers as a parameter. In conventional multi-type
air conditioners, control for reaching an appropriate operating point and control
for distributing the refrigerant to the rooms have been carried out by throttling
the second electronic expansion valves 10A to 10F corresponding to the rooms. However,
when the number of indoor units 3A to 3F is increased, since the difference in the
required refrigerant amount between cooling and heating operations is increased, surplus
refrigerant produced during the heating operation cannot be handled, and the refrigerant
is accumulated in the condensers (indoor heat exchangers), thus increasing the degree
of supercooling. As a result, to satisfy the required performance, it is necessary
to increase the rotational frequency of the compressor 4, thus causing an inefficient
operation.
[0034] Therefore, the first electronic expansion valve (EEVH) 8, which is used to adjust
the operating point of the entire system, is provided, and the receiver 9 is disposed
immediately before the first electronic expansion valve 8, thereby making it possible
to hold the surplus refrigerant and ensure an appropriate degree of supercooling.
Furthermore, in order to reach the appropriate operating point as soon as possible,
the throttle level of the first electronic expansion valve (EEVH) 8 is controlled
by using, as parameters, not only the outside air temperature, the suction degree
of superheat, and the discharge degree of superheat but also the capacity of the plurality
of the indoor heat exchangers, the number of stopped units, and the presence or absence
of a large wall-type unit that includes a high-capacity indoor heat exchanger, and
the distribution of the refrigerant to the indoor units 3A to 3F is controlled according
to the demand rotational speeds for the rooms via the second electronic expansion
valves (EEVs) 10A to 10F corresponding to the rooms, thereby making it possible to
swiftly attain the optimum operating point.
[0035] Specifically, during the heating operation, in the transient control, the degree
of opening OP of the first electronic expansion valve 8 is calculated by Formula (2).
Parameters used in the calculation include not only the outside air temperature, the
suction degree of superheat, and the discharge degree of superheat but also the correction
coefficients a and b, determined based on the outside air temperature and the capacity
of the indoor heat exchangers, the correction coefficient c, determined based on the
number of stopped units, the correction coefficient d, determined based on the temperature
deviation of the discharge degree of superheat with respect to the target zone and
the time variation of the discharge degree of superheat at the switchover from open-loop
control to zone control, and the correction coefficient Z
4, determined based on the presence or absence of a large wall-type unit that includes
a high-capacity indoor heat exchanger.
[0036] In the table shown in Fig. 4, the correction coefficient a is determined based on
the total capacity of the plurality of the indoor heat exchangers 19A to 19F connected
to the multi-type air conditioner 1 and the values A to D of the outside air temperature
detected by an outside air temperature sensor 28. In the table shown in Fig. 5, the
correction coefficient b is determined based on the total capacity of the plurality
of the indoor heat exchangers 19A to 19F connected to the multi-type air conditioner
1 and the values A to D of the outside air temperature detected by the outside air
temperature sensor 28. For example, in the multi-type air conditioner 1, if the total
capacity of the plurality of the indoor heat exchangers falls within a range from
301 to 400, when the outside air temperature is set to the value C, the correction
coefficient a is set to 0.6, and the correction coefficient b is set to 55.
[0037] The total capacity of the plurality of the indoor heat exchangers in the tables shown
in Figs. 4 and 5 is obtained by summing the capacities of the heat exchangers of the
plurality of the indoor units connected to the multi-type air conditioner 1, from
the table shown in Fig. 9 indicating, for example, the percentages of the capacities
of the heat exchangers of the other indoor units, where the capacity of the heat exchanger
of a medium wall-type indoor unit is set to 100.
[0038] Furthermore, as shown in Fig. 10, the outside air temperature is set to the value
A when the outside air temperature detected by the outside air temperature sensor
28 has a difference of +12 °C or greater from the reference value; the outside air
temperature is set to the value B when it has a difference that falls in a range from
-1 °C to +11 °C from the reference value; the outside air temperature is set to the
value C when it has a difference that falls in a range from -1 °C to -9 °C from the
reference value; and the outside air temperature is set to the value D when it has
a difference smaller than -9 °C from the reference value.
[0039] Furthermore, in the table shown in Fig. 6, the correction coefficient c is the sum
of α pulses determined according to the value of the total capacity of the indoor
heat exchangers of stopped units among the indoor units 3A to 3F. For example, if
the total capacity of the indoor heat exchangers of stopped units is smaller than
90, the correction coefficient c is set to 3. If the total capacity thereof is 111
or greater, the correction coefficient c is set to 10. Furthermore, in particular,
if a large wall-type unit that includes a high-capacity indoor heat exchanger (large
wall type shown in Fig. 9) is included in the plurality of the indoor units 3A to
3F, the correction coefficient Z
4 is used as a multiplicative factor. As shown in Fig. 8, the correction coefficient
Z
4 is set to 1.1 when the total capacity of the indoor heat exchangers is 399 or smaller
and is set to 1.5 when the total capacity of the indoor heat exchangers is 400 or
greater.
[0040] Furthermore, in the open-loop control, the correction coefficients Z
2 and Z
3, which are used to maintain appropriate values of the suction degree of superheat
and the discharge degree of superheat, respectively, are selected as follows. A preset
coefficient Z
2 is selected based on the suction degree of superheat calculated from the difference
between the detected value from a suction temperature sensor 29 and the average value
of the detected values from the indoor heat-exchanger sensors 30A to 30F, during the
cooling operation, or the difference between the detected value from the suction temperature
sensor 29 and the detected value from the outdoor heat-exchanger sensor 26, during
the heating operation. Furthermore, a preset coefficient Z
3 is selected based on the discharge degree of superheat calculated from the difference
between the detected value from the discharge temperature sensor 25 and the detected
value from the outdoor heat-exchanger sensor 26, during the cooling operation, or
the difference between the detected value from the discharge temperature sensor 25
and the maximum value among the detected values from the indoor heat-exchanger sensors
30A to 30F, during the heating operation.
[0041] As described above, the actual rotational speed of the compressor 4 is corrected
by using the correction coefficients a, b, c, Z
2, Z
3, and Z
4, as parameters, to calculate the degree of opening OP of the first electronic expansion
valve 8, thereby making it possible to swiftly attain the optimum operating point.
However, at the switchover from open-loop control to zone control after a predetermined
period of time (for example, three minutes) has elapsed, if a deviation from the appropriate
degree of opening in open-loop control is large, as shown in Fig. 3, when the discharge
degree of superheat TDSH of the refrigerant calculated from the detected value from
the discharge temperature sensor 25 and the detected value from the high-pressure
pressure sensor 27 is controlled so as to fall within the target zone, operations
in which the degree of opening of the first electronic expansion valve 8 is over-throttled
and over-relaxed may be repeated depending on the operating conditions, thus causing
a delay in switching over to the target zone (optimum operating point), in some cases.
[0042] In order to solve this problem, in this embodiment, the correction coefficient d,
which is determined in consideration of a temperature deviation E(n) of the discharge
degree of superheat TDSH with respect to the target zone and a time variation DE of
the discharge degree of superheat TDSH at the switchover from open-loop control to
zone control, is added to the above-described parameters. In the table shown in Fig.
7, the correction coefficient d is determined from the total capacity of the plurality
of the indoor heat exchangers 19A to 19F connected to the multi-type air conditioner
1 and the values A to D of the outside air temperature detected by the outside air
temperature sensor 28, and is set to a value that is sequentially updated according
to the past operating conditions. Specifically, if the total capacity of the plurality
of the indoor heat exchangers 19A to 19F connected to the multi-type air conditioner
1 falls within a range from 301 to 400, the correction coefficient d is increased
or decreased according to the past operating conditions and is sequentially updated.
[0043] The correction coefficient d is used to prevent a situation in which, during the
heating operation, at the switchover from open-loop control to zone control, a deviation
from the appropriate operating point in the open-loop control becomes large, and the
degree of opening of the first electronic expansion valve 8 is over-throttled, thus
overshooting the target zone and causing hunting, as indicated by curve X in Fig.
3, or the degree of opening is over-relaxed, thus casing a delay in reaching the target
zone, as indicated by curve Y. In the case of the curve X, the high pressure is increased,
and the oil level of the compressor 4 is reduced. In the case of the curve Y, the
oil temperature cannot be ensured. Therefore, it is difficult to stably operate the
compressor 4.
[0044] Furthermore, the correction coefficient d is sequentially rewritten in the table
shown in Fig. 7, as follows. When the above-described situations occur in certain
operating conditions, the temperature deviation E(n) of the discharge degree of superheat
TDSH with respect to the target zone and the time variation DE of the discharge degree
of superheat TDSH are calculated at sampling intervals (for example, every 40 seconds).
In the table in Fig. 11 showing the relationship between the temperature deviation
E(n) and the time variation DE, for example, when the percentage of the calculated
values of the time variation DE and the temperature deviation E(n) satisfying 1 <
DE and 2 < E(n), respectively, exceeds a predetermined percentage, it is judged that
the degree of opening of the first electronic expansion valve 8 is over-throttled,
and the correction coefficient d is increased by +1. When the percentage of the calculated
values of the time variation DE and the temperature deviation E(n) satisfying DE <
-1 and E(n) < -2, respectively, exceeds a predetermined percentage, it is judged that
the degree of opening of the first electronic expansion valve 8 is over-relaxed, and
the correction coefficient d is decreased by -1.
[0045] Therefore, if a similar operating point appears in the operation thereafter, it is
possible to correct the degree of opening of the first electronic expansion valve
8 in open-loop control to an appropriate degree of opening, to resolve a delay in
reaching the target zone, which is caused when the degree of opening of the first
electronic expansion valve 8 is over-throttled or over-relaxed, and to swiftly reach
the optimum operating point, that is, the ideal zone-control region, as indicated
by curve Z shown in Fig. 3.
[0046] Therefore, according to this embodiment, the following advantageous effects are afforded.
In the multi-type air conditioner 1, the first electronic expansion valve (EEVH) 8,
which is used to adjust the operating point of the entire system, is provided separately
from the individual-room second electronic expansion valves (EEVs) 10A to 10F, which
are used to adjust the volumes of refrigerant to be supplied to the indoor heat exchangers
19A to 19F of the indoor units 3A to 3F, and the receiver 9 is disposed between the
first electronic expansion valve (EEVH) 8 and the second electronic expansion valves
(EEVs) 10A to 10F. Therefore, during the heating operation, the surplus refrigerant
can be held in the receiver 9. As a result, accumulation of the refrigerant in the
indoor heat exchangers 19A to 19F can be eliminated to ensure an appropriate degree
of supercooling.
[0047] Therefore, while suppressing the rotational speed of the compressor 4, efficient
operation satisfying the required performance can be realized. Furthermore, during
this operation, the degree of opening of the first electronic expansion valve (EEVH)
8 is corrected by using, as parameters, the outside air temperature, the indoor-heat-exchanger
capacity, the number of stopped units (indoor units), the suction degree of superheat,
and the discharge degree of superheat, so as to swiftly reach the optimum operating
point, that is, the ideal zone-control region. Therefore, it is possible to operate
the multi-type air conditioner 1 with high COP while ensuring the stable operation
of the compressor 4.
[0048] Specifically, during the heating operation, in open-loop control, the degree of opening
of the first electronic expansion valve (EEVH) 8 is controlled by using, as parameters,
at least the outside air temperature and the capacity of the plurality of the indoor
heat exchangers, thereby making it possible to set the degree of opening of the first
electronic expansion valve 8 in open-loop control to a more appropriate degree of
opening. Thus, even when the total capacity of the indoor heat exchangers 19A to 19F
is changed depending on the plurality of connected indoor units 3A to 3F, at the switchover
to zone control, it is possible to swiftly attain the optimum operating point to reduce
the time to reach the ideal zone-control region, and it is possible to operate the
multi-type air conditioner 1 with high COP while ensuring the stable operation of
the compressor 4.
[0049] Furthermore, since the air conditioner 1 is operated with the degree of opening of
the first electronic expansion valve (EEVH) 8 in the open-loop control during the
heating operation being set at a certain degree of opening calculated based on the
above-described various parameters, operations in which the degree of opening is over-throttled
and over-relaxed may be repeated depending on the operating conditions, thus causing
a delay in switching over to the optimum operating point, in some cases. However,
according to this embodiment, at the switchover to zone control, the temperature deviation
E(n) of the discharge degree of superheat TDSH with respect to the target zone and
the time variation DE of the discharge degree of superheat TDSH are calculated, and,
when the temperature deviation E(n) with respect to the target zone and the time variation
DE of the discharge degree of superheat TDSH are large, the degree of opening of the
first electronic expansion valve 8 for the next open-loop control is corrected in
response thereto.
[0050] Thus, if a similar operating point appears in the operation thereafter, it is possible
to correct the degree of opening of the first electronic expansion valve (EEVH) 8
in the open-loop control to an appropriate degree of opening. Therefore, at the switchover
from open-loop control to zone control, it is possible to make the degree of opening
of the first electronic expansion valve (EEVH) 8 swiftly reach the optimum operating
point, that is, the ideal zone-control region, and to realize high-COP operation of
the multi-type air conditioner 1 while ensuring the stable operation of the compressor
4.
[0051] Furthermore, in this embodiment, the correction coefficient d, which is used to correct
the degree of opening of the first electronic expansion valve (EEVH) 8, is determined
based on the outside air temperature and the total capacity of the plurality of the
indoor heat exchangers 19A to 19F. Thus, when the temperature deviation E(n) of the
discharge degree of superheat TDSH with respect to the target zone and the time variation
DE of the discharge degree of superheat TDSH are large at the switchover to zone control,
the correction coefficient d, which is changed according to the outside air temperature
and the capacity of the plurality of connected indoor heat exchangers 19A to 19F,
can be accordingly updated sequentially in the table and reflected in calculating
the degree of opening of the first electronic expansion valve 8 for the next open-loop
control. Therefore, if a similar operating point appears in the operation thereafter,
it is possible to correct the degree of opening of the first electronic expansion
valve 8 to an appropriate operating point by using the correction coefficient d and
to swiftly reach the ideal zone-control region at the switchover to zone control.
[0052] Furthermore, the correction coefficient d is increased or decreased when the percentage
at which the temperature deviation E(n) of the discharge degree of superheat TDSH
with respect to the target zone and the time variation DE of the discharge degree
of superheat TDSH, calculated at sampling intervals, are equal to or higher than a
predetermined value or are equal to or lower than a predetermined value exceeds a
predetermined percentage, at the switchover to zone control. Thus, by increasing or
decreasing the correction coefficient d, it is possible to prevent a situation in
which, at the switchover to zone control, the degree of opening of the first electronic
expansion valve 8 is over-throttled, thus making the discharge degree of superheat
TDSH overshoot the target zone and causing hunting, or is over-relaxed, thus causing
a delay in reaching the target zone. Therefore, it is possible to set the degree of
opening of the first electronic expansion valve 8 in open-loop control to an appropriate
degree of opening to swiftly reach the ideal zone-control region at the switchover
to zone control, and to ensure the stable operation of the compressor 4.
[0053] The present invention is not limited to the invention according to the above-described
embodiment, and appropriate modifications can be made without departing from the scope
thereof. For example, although a description has been given of an example in which
six indoor units 3A to 3F are connected in the above-described embodiment, the number
of the indoor units 3A to 3F may be higher than or lower than six. Furthermore, the
refrigerant circuit 22 can be modified to various types of circuits as long as it
has the first electronic expansion valve (EEVH) 8, the second electronic expansion
valves (EEVs) 10A to 10F corresponding to the indoor units 3A to 3F, and the receiver
9 disposed between the first electronic expansion valve (EEVH) 8 and the second electronic
expansion valves (EEVs) 10A to 10F.
[0054] Furthermore, in the above-described embodiment, a description has been given of an
example in which the second electronic expansion valves (EEVs) 10A to 10F are disposed
closer to the outdoor unit 2; however, as a matter of course, the second electronic
expansion valves (EEVs) 10A to 10F corresponding to the indoor units 3A to 3F can
be disposed closer to the indoor units 3A to 3F.
{Reference Signs List}
[0055]
1 multi-type air conditioner
2 outdoor unit
3A to 3F indoor units
4 compressor
6 four-way switching valve
7 outdoor heat exchanger
8 first electronic expansion valve (EEVH)
9 receiver
10A to 10F second electronic expansion valves (EEVs)
19A to 19F indoor heat exchangers
23 outdoor controller
24 expansion-valve control section
25 discharge temperature sensor
27 high-pressure pressure sensor
28 outside air temperature sensor