[0001] The present invention relates to a refrigerant circuit for domestic refrigerating
apparatus operating at two different temperatures, in particular for a so-called "no
frost" refrigerating apparatus of the automatic defrosting type including a rotary
compressor.
[0002] As generally known, the refrigerant circuit of refrigerating apparatus of this type
comprises a compressor (formerly of the reciprocating type exclusively), a condenser,
at least one capillary and two evaporators disposed respectively in a storage compartment
and a freezer compartment. The two compartments are disposed separately from one another
in a cupboard housing and closed by separate doors. The evaporators are preferably
interconnected in series, and the refrigerant circuit normally includes a thermostatically
controlled valve permitting the flow of the refrigerant to be selectively directed
to both evaporators or to the evaporator of the freezer compartment only.
[0003] Recent developments provide the employ of compressors of the rotary type in domestic
refrigerating apparatus having only a single compartment for the cold storage of foods
and thus only a single evaporator. The employ of rotary compressors is advantageous
from the viewpoint of energy consumption which is reduced by about 5% by comparison
to that of corresponding reciprocating compressors. On the other hand the rotary compressor
has the shortcoming of requiring a longer period of time than a reciprocating compressor
for attaining the proper operation pressure when the circuit operates under thermostatic
control. This is because during inoperative periods of the rotary compressor the refrigerant
fluid remaining in the compressor body at a high temperature and high pressure tends
to escape towards the evaporator with the resultant equilibration of the pressure
in the entire circuit.
[0004] The elimination of this disadvantage requires the insertion 4.:ito the circuit of
two interceptor valves, upstream and downstream, respectively, of the compressor;
the considerable pressure difference (6-8 bar) existing between the inlet and the
outlet of the compressor when it is started does not represent a problem in the case
of a rotary compressor thanks to its high starting torque. The employ of the two valves,
however, envolves a complicated construction, particularly at their welded connections,
as the weld seams constitute critical points in the refrigerant circuit. For further
reducing the energy consumption in a refrigerating apparatus having a single evaporator,
it has also been proposed to employ a special valve having a high-pressure inlet connected
to the condenser, a high-pressure outlet connecetd to the capillary and to the evaporator,
a low-pressure inlet connected to the evaporator, and a low-pressure outlet connected
to the compressor. A valve of this type is thus rather complicated, expensive, and
above all cannot be adapted to refrigerating apparatus operating at two temperatures,
that is, having two evaporators to be supplied in series or selectively.
[0005] It is therefore an object of the present invention to provide a refrigerant circuit
with a single rotary compressor for refrigerating apparatus operating at two temperatures,
preferably with automatic defrosting, such circuit to be of simple construction and
to operate at reduced energy consumption and with improved reliability.
[0006] This object is attained in a refrigerant circuit for domestic refrigerating apparatus
operating at two temperatures, and in particular with automatic defrosting, said circuit
comprising a compressor, a condenser, two evaporators preferably connected in series,
and at least one valve for selectively directing the refrigerant fluid to said evaporators,
said valve having one inlet and two outlets and being inserted between said condenser
and said evaporators, said circuit being characterized in that said compressor is
of the rotary type, and said valve comprises two closure members adapted to close
both outlets when said compressor is inoperative, and to selectively open one of said
two outlets when said compressor is in operation.
[0007] The advantages and characteristics of the invention will become more clearly evident
from the following description, given by way of example with reference to the accompanying
drawings, wherein:
fig. 1 shows a diagram of a refrigerant circuit according to the invention for a refrigerating
apparatus operating at two temperatures, and
figs. 2 - 4 show diagrammatic illustrations of different operating positions of a
valve inserted into the circuit shown in fig. 1.
[0008] The refrigerant circuit shown in fig. 1 comprises a compressor 5 which according
to the invention is of the rotary type. The outlet of compressor 5 is connected to
a condenser 6, the outlet of which is connected to the inlet 8 of a three-way solenoid
valve 7. The two outlets 9 and 10 of solenoid valve 7 are connected respectively to
two parallel branches of the circuit. In particular, a branch connected to outlet
9 comprises a capillary 11 and an evaporator 12 disposed in the cold-storage compartment
of the refrigerating apparatus. This compartment is usually to be kept at a temperature
of about +5 °C. Another branch connected to outlet 10 comprises a capillary 13 and
is connected to the first branch downstream of evaporator 12. Downstream of this connection
the circuit includes another evaporator 14 disposed in the freezer compartment of
the refrigerating apparatus, which is usually to be kept at a temperature of about
-24 °C.
[0009] The return branch of the circuit leading from evaporator 14 to compressor 5 is provided
with a non-return valve 15. In the inoperative state of compressor 5, valves 7 and
15 are effective to divide the circuit into a high-pressure portion comprising compressor
5 and condenser 6, and a low- pressure portion including the two evaporators 12 and
14.
[0010] The described circuit is typical for a refrigerating apparatus operating at two temperatures,
with the exception of non-return valve 15, the employ of which is required by the
employ of the rotary compressor. In the particular case of a so-called "no frost"
refrigerating apparatus with automatic defrosting, a fan (not shown in the drawing)
is provided to cooperate in a known manner with evaporator 14 for creating a forced
air circulation in the freezer compartment. Valve 7 in accordance with the invention
comprises a tubular body formed with the two outlets 9 and 10 facing in opposite directions,
and inlet 8 extending at right angles to outlets 9 and 10. Disposed in the tubular
body are two closure members 16 and 17 cooperating with outlets 9 and 10, respectively,
and a compression spring 18 inserted therebetween. Associated to each closure member
16, 17 is a respective electromagnetic coil 19, 20. The control of solenoid valve
7 and the resultant operation of the entire refrigerant circuit proceeds as follows:
When the compartments of the refrigerating apparatus are not in need of refrigeration,
compressor 5 is inoperative, valve 15 is closed, and both outlets 9 and 10 of valve
7 are likewise closed (fig. 2). To this purpose coils 19 and 20 are deenergized, and
spring 18 acts to hold closure members 16 and 17 in the closure position.
[0011] Under these conditions the portion of the circuit extending beteen valve 15 and valve
7 and including compressor 5 and condenser 6 contains the refrigerant fluid at relatively
high temperature and pressure.
[0012] In the remaining portion of the circuit the refrigerant fluid is at relatively low
pressure and temperature. The two portions of the circuit are thus completely separated
from one another. When both compartments of the refrigerating apparatus are in need
of refrigeration, compressor 5 is started and valve 15 is opened. At the saem time
coil 19 is energized to retract closure member 16 against the action of spring 18
for opening outlet 9 of vlave 7 (fi
g.3). As a result the refrigerant fluid is permitted to flow through both evaporators
12 and 14.
[0013] The same situation arises when only the cold-storage compartment is in need of refrigeration.
Also'in this case the refrigerant fluid flows through both evaporators 12 and 14.
The resultant additional refrigeration of the freezer compartment, although not required,
cannot do any harm. When on the other hand only the freezer compartment is in need
of refrigeration, compressor 5 is started, valve 15 is opened, and coil 20 - instead
of coil 19 - is energized to retract closure member 17 against the action of spring
18. In this manner outlet 10 of valve 7 is opened, so that the refrigerant fluid flows
only through evaporator 14.
[0014] The advantages of the proposed solution, namely, reduced cost and improved reliability,
are evident, in that a single valve is required for establishing the various operating
modes of a refrigerator-freezer, to thereby simplify the construction of the circuit
by providing a reduced number of welds therein. The energy consumption is reduced
by the employ of a single rotary compressor and by reducing the time the coils are
to be energized for actuating solenoid valve 7.
[0015] In contrast to the case of the refrigerant circuit of a refrigerator-freezer having
a single reciprocating compressor in combination with a solenoid valve, there is no
need of a device for retarding the re-starting of the compressor. While a reciprocating
compressor due to its lower starting torque requires the pressures in the circuit
to be substantially in equilibrium, a rotary compressor encounters no starting problems
in the presence of substantial pressure differences in the refrigerant circuit.
[0016] The described construction of solenoid valve 7 is of course solely given by way of
example. The control of the valve may in fact be accomplished by an electronic device
(e.
g. PTC or the like) instead of by electromechanical means, it being understood that
such valve be capable of controlling the different operating modes described, and
in particular of simultaneously closing both of its outlets.
1. Refrigerant circuit for a domestic refrigerating apparatus operating at two temperatures,
and in particular with automatic defrosting capability, comprising a compressor, a
condenser, two evaporators preferably connected in series, and at least one valve
for selectively directing the refrigerant fluid to said evaporators, said valve having
an inlet and two outlets and being disposed between said condenser and said evaporators,
characterized in that said compressor (5) is of the rotary type, and said valve (7)
comprises two closure members (16, 17) adapted to close both said outlets (9, 10)
when said compressor (5) is inoperative, and to selectively open one of said outlets
(9, 10) when said compressor (5) is in operation.
2. A refrigerant circuit according to claim 1, characterized in that said closure
members (16, 17) of said valve (7) are disposed opposite one another with a compression
spring (18) interposed therebetween, each closure member (16, 17) being operable by
means of a respective electromagnetic coil (19, 20) so as to open the corresponding
outlet of said valve (7) when the respectibe coil is energized.