Refrigerator with less ice on evaporator

Abstract

Described is, among other things, a refrigerator. The refrigerator comprises a cooling arrangement comprising a compressor, a condenser and an evaporator connected in a closed loop wherein a refrigerant is circulated to provide cooling in the refrigerator. The refrigerator further comprises a controller and at least one cooled compartment. The refrigerator has a compartment temperature sensor for providing a temperature for the at least one cooled compartment, and an evaporator temperature sensor connected to the evaporator for providing an evaporator temperature. The controller is configured to control the operation of the compressor based on a set temperature for said at least one cooled compartment, and the controller is further configured to adjust the operation control of the compressor speed or the compressor run time based on the evaporator temperature.

Description

[0001] Refrigerator with less ice on evaporator

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a refrigerator. In particular, the present disclosure relates to a refrigerator allowing for reduced ice formation on the evaporator.

[0004] BACKGROUND

[0005] In a refrigerator cooling is provided by a cooling circuit where an evaporator is cooled to provide cooling for the refrigerator. The evaporator typically becomes very cold and ice can form on the evaporator.

[0006] Forming of ice on the evaporator is generally not desired and can for example lead to energy losses in the cooling system. It is therefore desired to reduce the risk for ice forming on the evaporator.

[0007] Also, there is a constant desire to improve the performance in a refrigerator and to provide more efficient refrigerator. Hence, there is a need for an improved a refrigerator.

[0008] SUMMARY

[0009] It is an object of the present invention to provide an improved refrigerator.

[0010] This object and / or others are obtained by the refrigerator as set out in the appended claims.

[0011] As has been realized by the inventors, a common problem in at least some types of refrigerators is overcooling of the evaporator. This problem can typically occur in refrigerators having both a refrigerator compartment and a freezer compartment where only one compartment is dynamically controlled, but also in other types of refrigerators.

[0012] In order to solve this problem, the output from a temperature sensor of the evaporator can be used to the limit the maximum speed of the compressor or the compressor run time to ensure that the evaporator is not overcooled and thereby reduce the risk for ice formation on the evaporator. Thus, to solve the problem of ice formation on the evaporator that typically can occur when the compartment is warm and the evaporator is cold, the operation control of the compressor (run time, speed etc.) that is normally controlled based on the temperature sensor output from the cooled compartment can be supplemented to be also based on the output from a temperature sensor of the evaporator.

[0013] In accordance with the invention, a refrigerator is provided. The refrigerator comprises a cooling arrangement comprising a compressor, a condenser and an evaporator connected in a closed loop wherein a refrigerant is circulated to provide cooling in the refrigerator. The refrigerator further comprises a controller and at least one cooled compartment. The refrigerator has a compartment temperature sensor for providing a temperature for the at least one cooled compartment, and an evaporator temperature sensor connected to the evaporator for providing an evaporator temperature. The controller is configured to control the operation of the compressor based on a set temperature for said at least one cooled compartment, and the controller is further configured to adjust the operation control of the compressor speed or the compressor run time based on the evaporator temperature. Hereby, the operation of the compressor can be adjusted to deliver less cooling in the event that the evaporator risks getting too cold so that there is a risk of ice forming on the evaporator. By eliminating or at least reducing the risk of ice formation on the evaporator, the performance of the refrigerator can be improved.

[0014] For example, when the compressor is a variable speed compressor, the controller can be configured to adjust the control of the compressor speed by reducing the compressor speed based on the evaporator temperature. For example, the controller can be configured to set a maximum compressor speed or reduce the compressor speed based on the evaporator temperature.

[0015] In another example, when the compressor is a fixed speed compressor, the controller can be configured to adjust the control of the compressor by reducing the compressor run time based on the evaporator temperature. For example, the controller can be configured to adjust the operation control of the compressor by setting a maximum compressor run time based on the evaporator temperature.

[0016] In accordance with one embodiment, the controller is configured to adjust the operation control of the compressor speed or run time to limit the minimum temperature of the evaporator to a set evaporator minimum temperature. Hereby a control scheme can be obtained that strives to keep the evaporator temperature above a temperature that does not risk that ice is formed on the evaporator. The set evaporator minimum temperature can in some embodiments be dependent on some parameters. For example, the set evaporator minimum temperature can be based on the ambient temperature, and / or the cooled compartment temperature. The ambient temperature can be obtained in various ways. For example, the refrigerator can comprise an ambient temperature sensor for providing the ambient temperature. Also, the refrigerator can comprise an interface for receiving the ambient temperature from another entity or the refrigerator can be configured to determine the ambient temperature based on an internal measured parameter.

[0017] The invention allows for controlling the compressor using a SISO (Single input / single output) control technique. It can be applied to a regular PID control algorithm. The SISO can use as target (or set point) the minimum evaporator temperature and the output of the control can be the maximum compressor speed directly or a speed reduction value. Alternatively, the output can be a maximum compressor run time directly or a run time reduction value. When evaporator temperature drops below the target, the controller is enabled to reduce the maximum speed (run time) limit or return a speed (run time) reduction parameter, affecting the final compressor speed (run time) as calculated by some control algorithm.

[0018] BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will now be described in more detail by way of non-limiting examples and with reference to the accompanying drawings, in which:

[0020] - Fig. 1 illustrates a refrigerator,

[0021] - Fig. 2 is a flow chart illustrating some steps performed when controlling a compressor of a refrigerator, and

[0022] - Fig. 3 illustrates a controller.

[0023] DETAILED DESCRIPTION

[0024] In Fig. 1, a schematic view of a typical household refrigerator 10 comprising a cooled compartment 12 is shown. The exemplary refrigerator 10 in Fig. 1 is only shown with a single cooled compartment 12. However, the refrigerator 10 can be any type of refrigerator. For example, the refrigerator 10 can have a refrigerator compartment and a freezer compartment. The refrigerator can also have any other type of configuration with multiple cooled compartments or only a single freezer compartment. The refrigerator 10 is shown in a schematic way and some components are omitted and some components are shown in a simplified manner for better understanding of how the invention can be implemented. To cool the refrigerator a cooling system is provided.

[0025] The cooling system comprises a compressor 32, a condenser 34 and an evaporator 36. The cooling system is controlled by a controller 42 of the refrigerator 10. The cooling system also comprises a capillary tube or a similar device such as an expansion valve 38. In the cooling system of Fig. 1 only one evaporator 36 is shown. The cooling system can in some embodiments have multiple evaporators. The controller 42 can control different functions in the refrigerator. In particular, the controller 42 can be configured to control the compressor 32. The control of the compressor 32 can be based on various input signals. In the exemplary embodiment of Fig. 1, the refrigerator 10 has a cooled compartment temperature sensor 44 and also an evaporator temperature sensor 46. The output from the cooled compartment temperature sensor 44 and also an evaporator temperature sensor 46 can be provided to the controller 42 to be used as control signals for controlling the compressor as will described in more detail below.

[0026] It is understood that other components (not shown) conventionally present in a refrigerator also can be present in the refrigerator 10. Thus, the refrigerator 10 can also comprise other components not shown in Fig. 1 such as an ambient temperature sensor, an evaporator fan and other components.

[0027] The compressor 32 drives a refrigerant in a cycle whereby the condenser 34 becomes hot and the evaporator 36 becomes cold. Depending on the type of compressor 32, different control schemes can be applied to the controller 42. The controller 42 can, based on some input signals, determine how the compressor 32 is to be run. As set out above, the input signal to the controller can comprise a temperature sensor signal from the temperature sensor 44 indicative of the temperature in the refrigerator 10. For example, for a fixed speed compressor, the compressor can be in an ON state until the temperature reaches a target temperature, the CUT-OUT temperature, then the compressor stops and temperature rises up to a CUT-IN temperature at which the compressor starts again, bringing down the temperature and restarting the compressor cycle. In variable speed compressor refrigerators, the compressor speed is changed (controlled) by the controller42 to keep a temperature that balances the thermal loss from the refrigerator so that the temperature set for the cooled compartment is held within some pre-determined temperature range. The higher the speed of the compressor 32, the higher the cooling capacity. However, as set out above, when controlling the refrigerator temperature, there is a risk of ice forming on the evaporator 36. In order to eliminate, or at least reduce, the problem of ice forming on the evaporator 36, the controller can be configured to base the control of the compressor 32 also on the evaporator temperature.

[0028] In Fig. 2, some steps that can be performed in an exemplary control procedure for controlling the compressor 32 are shown. First in a step 200, the procedure is initiated. Next in a step 201, some parameter values are obtained. For example, the controller 42 can obtain the set temperature for a cooled compartment of the refrigerator, and the actual temperature of the cooled compartment. The set temperature can typically be set by a user via some interface. The actual temperature can typically be obtained from a temperature sensor 44 located inside or adjacent to the cooled compartment. In addition, the temperature of the evaporator 36 can be obtained. For example, the temperature from the evaporator temperature sensor 46 can be provided to the controller 42. The controller 42 is configured to control the operation of the compressor 32 based on the set temperature for the cooled compartment, and also configured to adjust the operation control of the compressor speed or the compressor run time based on the evaporator temperature. Thus, the controller 42 can control the temperature to the set temperature. Controlling the temperature to the set temperature can be based on the temperature signal from the temperature sensor 44 for the cooled compartment. This can form a main control loop of the controller 42 where the speed of a variable speed compressor or the run time length of a fixed speed compressor is controlled to deliver cooling in the refrigerator such that the temperature of the cooled compartment is controlled to the set temperature. In addition, the controller 42 can adjust the speed of a variable speed compressor or the run time length of a fixed speed compressor based on the evaporator temperature. Hereby ice formation on the evaporator can be avoided or reduced in that the cooling can be limited based on the temperature of the evaporator. This can be performed in a step 203. Thus, when running the compressor 32, the evaporator 36 risks becoming too cold such that there is a risk that ice is formed on the evaporator 36. The control of the compressor can be adjusted to avoid that the evaporator 36 becomes too cool. In accordance with one exemplary embodiment, the adjustment of the operation of the compressor is performed such that the speed of the compressor or the run time of the compressor is limited to a maximum speed or a maximum run time based on the temperature of the evaporator. Hereby cooling provided by running the compressor can be limited and the evaporator does not risk getting cooled to a temperature where ice is formed of the evaporator.

[0029] In accordance with another exemplary embodiment, the speed of the compressor or the run time of the compressor is reduced based on the evaporator temperature. Thus, when the main control loop of the controller is set to a speed target or a run length target, this target is adjusted based on the temperature of the evaporator 36. The effect of such an operation is that the temperature of the evaporator can be controlled by adjusting (reducing) the speed target or a run length target when the evaporator risks getting too cold.

[0030] Thus, in step 203, the control of the operation of the compressor is adjusted based on the evaporator temperature. The adjustment can be performed in different manners that can depend on the implementation. For example, depending of the type of compressor different adjustments can be performed by the controller. In accordance with one embodiment when the controlled compressor is a variable speed compressor the controller can be configured to adjust the control of the compressor speed by reducing the compressor speed based on the evaporator temperature. For example, the controller can be configured to adjust the control of the compressor speed by setting a maximum compressor speed based on the evaporator temperature or the compressor speed can be reduced by a speed reduction parameter that is based on the temperature of the evaporator. Regardless of the control method, the controller is enabled to adjust the speed of the variable speed compressor such that the evaporator does not become too cold. Similarly, when the compressor is a fixed speed compressor, the controller can be configured to adjust the operation control of the compressor by reducing the compressor run time based on the evaporator temperature. For example, the controller can be configured to adjust the operation control of the compressor by setting a maximum compressor run time based on the evaporator temperature or the run time can be reduced by a run time reduction parameter that is based on the temperature of the evaporator. Again, regardless of the control method, the controller is enabled to adjust the run time of the fixed speed speed compressor such that the evaporator does not become too cold.

[0031] In accordance with one embodiment, the controller is configured to adjust the operation control of the compressor speed or run time to limit the minimum temperature of the evaporator to a set evaporator minimum temperature. Thus, by ensuring that the evaporator never has a temperature that is below some set threshold temperature, ice formation on the evaporator can be avoided or at least reduced.

[0032] The set evaporator minimum temperature can in accordance with some embodiments be based on some relevant parameter such as ambient temperature and / or compartment temperature. By allowing the minimum temperature to be set in response to such parameters, the minimum temperature can take into account the current operation conditions of the refrigerator. Hereby it is enabled that the evaporator can become cold to ensure good refrigerator properties and at the same time not too cold so that ice can form on the evaporator which would negatively affect the refrigerator properties in terms of energy efficiency and so forth.

[0033] When the set evaporator minimum temperature is based on the ambient temperature, the controller can obtain the ambient temperature in some suitable manner. For example, the refrigerator can comprise an ambient temperature sensor for providing the ambient temperature to the controller. In accordance with another embodiment, the refrigerator can comprise an interface for receiving an ambient temperature from another entity such that the controller can receive the ambient temperature via the refrigerator interface. The refrigerator interface can for example be part of the controller itself. The ambient temperature can also be indirectly determined by the controller based on one or more internal parameters of the refrigerator. For example, the ambient temperature can be determined as an estimate based on the thermal mass, or the compressor duty cycle or some other known method whereby the ambient temperature can be indirectly determined.

[0034] In accordance with one embodiment, when the compressor 32 is a fixed speed compressor and the refrigerator 10 comprises a fan that can be controlled by the controller, a variable speed fan can be advantageous. Thus, because the evaporator temperature increases with a higher fan speed, when there is a need to reduce the run time for a fixed speed compressor to not let the evaporator become too cold, the controller can instead or as a supplement be configured to override the speed of the variable speed fan to a higher speed. In such an implementation, the controller 42 connected to the evaporator would override the fan speed controller, increasing the speed of the variable speed fan to warm up the evaporator such that ice is less likely to be formed on the evaporator.

[0035] Finally, in a step 205, the operation of the compressor is performed based on the control settings calculated in step 203. Thus, the speed of the compressor or the run time for the compressor is set based on the demand for cooling capacity. The speed or the run time for the compressor is also potentially adjusted or limited if needed to avoid or reduce ice formation on the evaporator. The procedure of Fig. 2 can then be repeated. For example, new parameter values can be repeatedly obtained and the procedure can then be re-started.

[0036] Further, the controller 42 can be implemented using suitable hardware and or software. An exemplary controller is depicted in Fig. 3. The hardware can comprise one or many processors 301 that can be arranged to execute software stored in a readable storage media 302. The processor(s) can be implemented by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared or distributed. Moreover, a processor or may include, without limitation, digital signal processor (DSP) hardware, ASIC hardware, read only memory (ROM), random access memory (RAM), and / or other storage media. The processor 42 is adapted to send and receive signals from other entities such as the compressor 32, the cooled compartment temperature sensor, the evaporator temperature sensor, and different external sensors or other units using an interface 303. The controller 42 can in particular be configured to implement the control procedures as described herein.

[0037] Using the methods and apparatuses as set out herein provides a more efficient refrigerator in that ice formation on the evaporator can be avoided or reduced. This will in turn reduce the energy losses in the refrigerator.

Claims

CLAIMS1. A refrigerator (10) comprising: a cooling arrangement comprising a compressor (32), a condenser (34) and an evaporator (36) connected in a closed loop wherein a refrigerant is circulated to provide cooling in the refrigerator,- a controller (42),- at least one cooled compartment (12),- a compartment temperature sensor (44) for providing a temperature for said at least one cooled compartment,- an evaporator temperature sensor (46) connected to the evaporator for providing an evaporator temperature, wherein- the controller is configured to control the operation of the compressor based on a set temperature for said at least one cooled compartment,- the controller being further configured to adjust the operation control of the compressor speed or the compressor run time based on the evaporator temperature.

2. The refrigerator (10) according to claim 1, wherein the controller (42) is configured to adjust the control of the compressor by reducing the compressor speed based on the evaporator temperature.

3. The refrigerator (10) according to claim 2, wherein the controller (42) is configured to adjust the control of the compressor by setting a maximum compressor speed based on the evaporator temperature.

4. The refrigerator (10) according to claim 1, wherein the controller (42) is configured to adjust the operation control of the compressor by reducing the compressor run time based on the evaporator temperature.

5. The refrigerator (10) according to claim 4, wherein the controller (42) is configured to adjust the operation control of the compressor by setting a maximum compressor run time based on the evaporator temperature.

6. The refrigerator (10) according to any one of claims 1 - 5, wherein the controller (42) is configured to adjust the operation control of the compressor speed or run time to limit the minimum temperature of the evaporator to a set evaporator minimum temperature.7 The refrigerator (10) according to claim 6, wherein the set evaporator minimum temperature is based on one or more of the following parameters: ambient temperature, and cooled compartment temperature.

8. The refrigerator (10) according to claim 7, when the set evaporator minimum temperature is based on the ambient temperature, the refrigerator further comprising an ambient temperature sensor for providing the ambient temperature.

9. The refrigerator (10) according to claim 7, when the set evaporator minimum temperature is based on the ambient temperature, the refrigerator further comprising an interface for receiving the ambient temperature from another entity.

10. The refrigerator (10) according to claim 7, when the set evaporator minimum temperature is based on the ambient temperature, the refrigerator is configured to determine the ambient temperature based on an internal measured parameter.

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