Refrigeration appliance with a plurality of storage compartments

Abstract

Refrigeration appliance comprising at least two storage compartments (10, 11) and a refrigerating circuit comprising a compressor (14), a condenser (15), valve means (18, 19) and two evaporators (12, 13). The compressor (14) is a variable-capacity compressor, and said valve means are constituted by a unidirectional valve (18) and a flow-diverting valve (19) to selectively feed said evaporators via respective throttle means (16, 17). The result is a sensible energy saving effect in the operation of the appliance.

Description

DESCRIPTION

[0001] The present invention refers to a refrigeration appliance, in particular of the household type, comprising at least two storage compartments intended to hold and preserve food products at different temperatures.

[0002] Refrigeration appliances provided with a cold storage, ie. refrigerated compartment and a freezer compartment are largely known in the art. These appliances are practically provided with either two separated refrigerating circuits, ie. a circuit for each compartment, or a single refrigerating circuit comprising two evaporators that are adapted to be fed selectively through a valve that diverts the flow of the refrigerant medium so as to appropriately respond to the demands for cold in the two compartments of the appliance. The first one of these solutions is of course the most expensive one, owing to the duplication of the circuits and, as a result, the component parts associated therewith. The second solution, on the contrary, has a lower efficiency, as well as an unsatisfactory behaviour in terms of effectiveness.

[0003] The patent publication EP 0 246 465 describes a refrigerating circuit for household refrigeration appliances that essentially comprises a compressor, a condenser and two evaporators arranged in series in a cold storage compartment and a freezing compartment, respectively. The compressor is of the rotary type, featuring a high starting torque. As a result, in view of preventing the pressures from getting balanced throughout the circuit during the switch-off periods of the compressor, the addition to such a circuit of a thermostatically controlled electromagnetic valve is proposed, which is provided with an inlet from the condenser and two outlets towards the evaporators. The two outlets of the electromagnetic valve may be both closed when the compressor is switched off, and may be selectively opened when the compressor is on the contrary switched on and operating. The solution described in this patent has however turned out to be just a theoretical, ie. practically unfeasible one, since an electromagnetic valve arrangement of such a kind is quite difficult to implement and would in any case involve an additional energy usage for the actuation and operation thereof,

[0004] The much more recent patent specification WO 00/49344 proposes again a solution similar to the one disclosed in the above cited publication EP 0 246 465, however without defining the type of compressor used, while on the other hand describing a valve solely in terms of operation and not construction.

[0005] In particular, when the evaporators are arranged in series (FIG. 4), it is practically impossible to understand how the valve 1 in its position S3 may be able to solely feed the evaporator 5B. In such a position of the valve, in fact, it seems practically unavoidable for almost all of the refrigerant medium to also flow through the evaporator 5A, thereby feeding both evaporators. Actually, the solution disclosed in this patent still represents just a further, albeit merely theoretical attempt towards achieving a refrigeration appliance ensuring a reduced energy usage through the optimisation of the refrigerating circuit thereof.

[0006] Such an aim can on the contrary be reached according to the present invention by making use of the combination of a new type of variable-capacity compressor (ie. a compressor with variable refrigeration power or capacity) and a new valve solution, as defined in the appended claims.

[0007] Features and advantages of the present invention will anyway be more readily understood from the description that is given below by way of non-limiting example with reference to the accompanying drawings, in which:

[0008] FIG. 1 is a schematical view of the most recent prior-art solution according to WO 00/49344;

[0009] FIG. 2 is a schematical cross-sectional view of a refrigeration appliance provided with a refrigerating circuit according to the present invention;

[0010] FIG. 3 is a diagrammatical view of the pattern of cold demand versus temperature changes in the cold storage and freezing compartments of the refrigeration appliance illustrated in FIG. 1.

[0011] As already stated above, the most recent prior art is represented is FIG. 1, which illustrates a refrigerating circuit with a compressor 2, a condenser 3 and two evaporators 5a and 5b arranged in series. Between the condenser 3 and the evaporators 5a and 5b there is provided a three-way valve 1. When in its position S1, this valve shuts the passage of refrigerant medium towards both evaporators. When in its position S2, the valve then allows the refrigerant medium to flow first through the evaporator 5a and then through the evaporator 5b. Finally, when in its position S3, the valve should close the passage P2 towards the evaporator 5a, while allowing the refrigerant medium to only flow through the evaporator 5b. This last situation, however, is frankly incomprehensible, since the valve 1, so as illustrated, cannot close the passage P2. In addition, even considering that a different type of valve might be capable of implementing such an operating condition of the circuit, the refrigerating circuit would certainly prove impossible to balance in a correct manner, owing to the two evaporators requiring considerably different amounts of cold.

[0012] The solution according to the present invention is illustrated schematically in FIG. 2, which shows a refrigeration appliance comprising a cold storage or refrigerating compartment 10 and a freezing compartment 11, each one of them being provided with a respective evaporator 12 and 13. The two evaporators are connected in series in the refrigerating circuit, which also comprises a compressor 14 and a condenser 15. Each evaporator is furthermore associated to a respective throttle, or capillary tube, 16 and 17.

[0013] According to the invention, the compressor 14 is a variable-capacity compressor, ie. a compressor with a variable refrigerating capacity, and the regulation of the refrigerant medium flow in the circuit is carried out with the aid of valve means provided between the condenser 15 and the capillary tubes 16 and 17. More precisely, such valve means can be constituted by a unidirectional valve 18 and a flow-diverting valve 19, both of them controlled by two thermostats (not shown) arranged in the compartments 10 and 11, respectively. The valve 18 enables the passage of refrigerant medium to the evaporators to be opened or closed. The valve 19, in turn, actually enables either both evaporators to be fed in series or the refrigerant medium to be only delivered to the evaporator 13 of the freezing compartment. It will of course be appreciated that the two valves 18 and 19 might well be replaced by a single three-way valve in the assumption that a valve of such a kind, capable of ensuring a reliable operation and a low energy usage, could actually be provided.

[0014] A correct equalization, or balance, of the refrigerating circuit is then obtained by appropriately sizing the capillary tubes 16 and 17 and, in particular, by having the capillary tube 16 ensuring a greater flow rate than the one of the capillary tube 17.

[0015] The actual energy saving effect, which by the way is the real and main purpose of the proposed solution, is therefore obtained through the combination of various elements.

[0016] The main one among these elements is constituted by the use of a variable-capacity compressor 14, which is provided with its own automatic control logic system capable of autonomously selecting the operating speed (and, therefore, the required refrigerating capacity) thereof on the basis of a combination (eg. the arithmetical mean value) of the percentages of operation, or running time, of the two compartments of the refrigeration appliance and the ON-periods (or operating periods) of the same compartments, by privileging the one that requires the longest operating time.

[0017] FIG. 3 illustrates a diagram showing the demand of cold, ie. heat-extraction requirement versus temperature variations in the cold storage compartment and the freezing compartment (as indicated in abscissas and ordinates, respectively). The letters A-H indicate the operating ranges at the various speeds of the compressor (A indicates the slowest speed, H the fastest speed). The rectangles represent the adjustment or setting areas of the refrigeration appliance at different room temperatures (Ta). The algorithm of the automatic control logic of the compressor 14 may for instance be based on following operation data: 1 OP. LEVELS SPEED RT (%) ON (min) A 1600  0 < 50 <90 B 1800 50 < 55 <90 C 2000 50 < 60 <90 D 2200 60 < 65 <90 E 2400 65 < 70 <90 F 2700 70 < 75 <180 G 3000 75 < 85 <180 H 3600  85 < 100 <180

[0018] where:

[0019] RT is the percentage of running time of the refrigeration appliance, and

[0020] ON is the operating time of the same appliance.

[0021] A further element that enables a real energy saving effect to be obtained is constituted by the utilization of the pulse-controlled valves 18 and 19. The actuation of these valves enables the circuit to be closed in the OFF periods of the refrigeration appliance, thereby preventing hot refrigerant medium from passing from the condenser 15 to the evaporators 12 and 13. In addition, the valve 19 really enables the evaporators to be fed in a selective manner, in accordance with the demand for cold, ie. the heat-extraction requirements of the respective compartments of the refrigeration appliance.

[0022] Finally, the differentiation in the flow-rate capacity of the capillary tubes 16 and 17 enhances the flexibility of the refrigerating circuit in view of delivering a refrigerating capacity that actually meets the thermal load of the appliance in connection with both the independent utilization of the two compartments and the different conditions of the same compartments (room temperature, thermostat settings, door openings, and the like).

Claims

1. Refrigeration appliance, in particular of the household type, comprising at least two storage compartments (10, 11) adapted to hold and preserve food products at different temperatures, as well as a refrigerating circuit comprising a compressor (14), a condenser (15), valve means (18, 19) for diverting the flow of refrigerant medium, and an evaporator (12, 13) arranged in each one of said compartments, in which said evaporators are connected in series with each other, characterized in that said compressor (14) is a variable-capacity compressor, and that said valve means are constituted by a unidirectional valve (18) and a flow-diverting valve (19) to selectively feed said evaporators via respective throttle means (16, 17).

2. Refrigeration appliance according to claim 1, characterized in that said throttle means (16, 17) are capillary tubes ensuring different flow rates, in which the capillary tube (16) associated to the evaporator (12) of the cold storage compartment has a greater flow rate than the capillary tube (17) associated to the evaporator (13) of the freezing compartment.

3. Refrigeration appliance according to claim 1 or 2, characterized in that the compressor (14) is provided with its own automatic control logic arrangement adapted to autonomously select the operating speed thereof on the basis of a combination of the working percentages of the two compartments (10, 11) of the refrigeration appliance and the ON-periods of the same compartments, while privileging the one that requires the longest operating time.