Control of refrigerator having multiple evaporators

Abstract

A refrigerator (10) is described that includes a freezing compartment (16) and a refrigerating compartment (12). The refrigerator has a cooling system (30) including a variable speed compressor (32), a condenser (34), and at least a first freeze evaporator (37) and a second cold storage evaporator (38). The freeze evaporator (37) is connected in series with the second cold storage evaporator (38) such that the outlet of the freeze evaporator (37) is connected to the inlet of the cold storage evaporator (38). The controller (50) is configured to control the cooling system (30) by periodically switching the variable-speed compressor (32) between an on-phase and an off-phase, where the controller (50) is configured to control the variable-speed compressor (32) to a high-speed state during the on-phase and then to a low-speed state during the off-phase. Wherein the speed of the variable-speed compressor (32) in the low-speed state is lower than the speed in the high-speed state.

Description

Technical Field

[0001] The present disclosure relates to a refrigerator having at least two evaporators. Specifically, the present disclosure relates to a refrigerator including a variable speed compressor and two evaporators connected in series. Background Art

[0002] In today's domestic refrigerators, a compressor cooling system is typically used. Furthermore, many of these cooling systems do not run continuously, but are switched on and off periodically. There is then a compressor on phase and a subsequent compressor off phase. This can also apply to variable speed compressors.

[0003] DE 102017003523 describes a refrigerator with an evaporator (including evaporator parts connected in series) and a variable speed compressor. The compressor is controlled to operate with a variable on-time and / or a variable speed based on the cooling demand.

[0004] There is a constant desire to improve the performance of refrigeration systems and to provide more efficient refrigeration systems. Therefore, there is a need for an improved refrigeration device and a cooling system for use as a multi-evaporator cooling system in a refrigerator. Summary of the invention

[0005] The object of the present invention is to provide an improved refrigerator having at least two evaporators.

[0006] This object and / or other objects are achieved by a refrigerator as described in the accompanying claims.

[0007] As the inventors have realized, efficient control of a two-chamber refrigerator can be achieved without using fans and / or electric valves. Alternatively, independent temperature control of the freezer and refrigerator compartments of a refrigerator having two evaporators in series can be achieved by providing a control scheme for a variable speed compressor.

[0008] According to the present invention, a refrigerator including a freezing chamber and a cold storage chamber is provided. The refrigerator has a cooling system, which includes a variable speed compressor, a condenser, and at least a first freezing evaporator and a second cold storage evaporator. The freezing evaporator and the second cold storage evaporator are connected in series so that the outlet of the freezing evaporator is connected to the inlet of the cold storage evaporator. The controller is configured to control the cooling system by periodically switching the variable speed compressor between the on phase and the off phase. The controller is configured to control the variable speed compressor to a high speed state during the on phase, and then to a low speed state, wherein the speed of the variable speed compressor in the low speed state is lower than the speed in the high speed state. Thus, the cooling amount between the two chambers can be distributed to the corresponding refrigerator chambers without using an electric valve or a fan, so the complexity and cost of cooling amount control can be reduced.

[0009] According to one embodiment, the duration of each cycle having an on phase and an off phase is constant. Thus, an efficient implementation can be obtained.

[0010] According to one embodiment, the speed of the variable speed compressor in the high speed state and the low speed state is a constant predetermined speed, respectively. Therefore, a simple and robust implementation can be obtained.

[0011] According to one embodiment, the controller is configured to deviate the speed of the variable speed compressor in the high speed state from the constant speed based on a triggering event. Thereby, additional control possibilities may be provided.

[0012] According to one embodiment, a fan is provided in at least one of the freezer compartment and the refrigeration compartment, and wherein the controller is configured to control the speed of the fan. Thus, improved control can be obtained when the refrigerator is provided with a fan.

[0013] According to one embodiment, the controller (50) is configured to control the speed of the fan based on a weighted linear combination of the temperature errors of the refrigerating chamber and the freezing chamber. Thus, efficient control of the fan can be achieved.

[0014] According to one embodiment, the controller is configured to calculate the cooling capacity set point of the compressor based on a weighted combination of the temperature errors of the refrigerating chamber and the freezing chamber. Thus, efficient control of the cooling capacity delivered by the refrigerator compressor can be achieved.

[0015] According to one embodiment, the controller is configured to calculate the relative duration of the high speed phase and the low speed phase based on a weighted combination of the temperature errors of the refrigerating chamber and the freezing chamber. Thus, the duration of the high speed phase and the duration of the low speed phase during the compressor on time can be determined in an efficient manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The invention will now be described in more detail by way of non-limiting examples and with reference to the accompanying drawings, in which:

[0017] - Figure 1 The refrigerator is shown.

[0018] - Figure 2 Demonstrated cooling system for refrigerators,

[0019] - Figure 3 Demonstrates a cooling cycle for a variable speed compressor,

[0020] - Figure 4 and Figure 5 Different cooling scenarios are shown.

[0021] - Figure 6 is a flow chart showing some of the steps used to control a variable speed compressor.

[0022] - Figure 7 and Figure 8 The calculations for different parameters are shown.

[0023] - Fig. 9 and Fig.10 Demonstrates the calculation of fan speed, and

[0024] - Fig.11 The controller is shown. DETAILED DESCRIPTION

[0025] The present invention will now be described more fully below with reference to the accompanying drawings, in which certain embodiments of the invention are shown. However, the present invention can be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that the present disclosure will be thorough and complete and will fully convey the scope of the invention to those skilled in the art. For example, the same or similar components of different embodiments may be exchanged between different embodiments. Some components may be omitted in different embodiments. Throughout the specification, the same reference numerals refer to the same elements.

[0026] exist Figure 1 In the embodiment of the present invention, a typical household refrigerator 10 includes a refrigerator (FF) compartment 12 and a freezer (FZ) compartment 16. Figure 1 The type of exemplary refrigerator 10 in FIG. 1 is referred to as a side-by-side refrigerator. However, the cooling system described herein may be used with any type of refrigerator, such as a French door refrigerator, a top freezer refrigerator, a bottom freezer refrigerator, or any other type of refrigerator. Figure 1 The door 14, shown as open in FIG. 1 , is hingedly mounted to the refrigerator body and serves to close the front of the refrigerator compartment 12 and provide access to the interior of the refrigerator compartment. Figure 1 The door 18 shown as open in the figure is also mounted to the refrigerator body by hinges and is used to close the front of the freezer compartment 16 and provide access to the interior of the freezer compartment. The refrigerator and freezer compartments may include a variety of shelves 20, closed drawers 22, and basket drawers 24 for storing food, etc. In addition, other configurations of the domestic refrigerator 10 can be envisioned to meet different needs depending on the type of refrigerator. In order to cool the refrigerator, a cooling system 30 is provided. The cooling system 30 can typically be a multi-evaporator cooling system. The evaporator can be arranged to cool different chambers. For example, one evaporator can cool the refrigerator compartment, while another evaporator can cool the freezer compartment. Additional evaporators can be arranged to cool other chambers.

[0027] Now combine Figure 2 The exemplary cooling system 30 is described in more detail below. Figure 2A cooling system 30 is shown in FIG. The cooling system 30 has a variable speed compressor (VSC) 32. The variable speed compressor drives the flow of refrigerant in a cooling circuit formed by a condenser 34 and some kind of expansion valve 36 (such as a capillary tube) located downstream thereof. Figure 2 In the illustrated configuration, downstream of the expansion valve 36 are two evaporators 37 and 38 arranged in series. The first evaporator 37 may be the evaporator arranged to cool the freezer compartment 16. The second evaporator 38 may be arranged to cool the refrigerator compartment 12. According to some embodiments, fans 43, 44 may be positioned in the freezer compartment 16 or in the refrigerator compartment 12 or in both compartments 12, 16. Further, air temperature sensors 41, 42 may be arranged in the freezer compartment 16 and in the refrigerator compartment 12. The cooling arrangement may be controlled by a controller 50, which may be operably connected to the various sensors and the compressor 32 for controlling the speed of the compressor 32.

[0028] It has been recognized that for two compartments of a refrigerator having evaporators in series (such as Figure 2 It is difficult to balance temperature and control temperature independently with a refrigerator (configuration shown in FIG. 3 ), especially without an electric valve that can divert the refrigerant flow to the refrigerated evaporator 38 or the frozen evaporator 37, or exclude one of the two evaporators from the circuit. One way to improve performance may be to use an evaporator fan to promote heat exchange in a single chamber to allow a certain degree of controllability. However, it is difficult to achieve independent control of the two chambers without an electric valve and a fan. In order to balance the cooling capacity between the two chambers, compromises are typically required in the design (such as making the temperature of the freezer lower than the required temperature) to achieve correct operation, which reduces the efficiency of the system. In other cases, a heater (also called a balancing heater) can be positioned in the cold storage room and turned on when needed to make the cold storage room warmer and avoid ice formation, while allowing the compressor speed to be increased to cool the freezer. Obviously, such an approach is not energy-efficient.

[0029] In order to more efficiently control the evaporators connected in series (where the outlet of the first evaporator is connected to the inlet of the second evaporator), the variable speed compressor can be controlled to allow better independent operation of the two evaporators for different cooling chambers. The control can be intended to allow a certain degree of independence in the temperature control of the two chambers 12, 16. This control can be done without evaporator fans in the freezer and refrigerator compartments, but it can also be controlled with a variable speed compressor with evaporator fans.

[0030] To achieve improved control, the variable speed compressor can be operated periodically with alternating on-off phases. During operation, the length (duration) of the on phase can be varied according to different operating conditions (typically room air temperature feedback and user settings). Typically, the longer the compressor is in the on phase, the greater the cooling capacity delivered to the refrigerator.

[0031] In each cycle, during the compressor on time, the speed of the compressor is applied according to a speed pattern having two phases of different speed and duration, a high speed phase followed by a low speed phase; in this order. The relative duration of the two phases is determined so as to distribute the cooling capacity among the chambers, and during operation, the relative duration of the two phases may vary according to different operating conditions (such as chamber air temperature feedback and user settings).

[0032] The total cooling capacity delivered by the compressor in one cycle is the sum of the cooling capacities delivered to the two chambers, represented by the compressor on-time and the speed of the compressor during the on-time. Figures 3 to 5 The area under the velocity pattern curve is shown.

[0033] This control is based on the following: at compressor startup, when the compressor operates at the highest speed (high-speed phase), the cold refrigerant first reaches the freezing evaporator, and due to the delivery delay, the relatively warm refrigerant that previously stayed in the freezing evaporator is still flowing through the refrigeration evaporator. In the subsequent low-speed phase, the lower compressor throughput causes the freezing evaporator to be filled with warmer refrigerant than in the previous phase. Therefore, in order to provide greater cooling capacity to the freezer rather than the refrigeration chamber, the relative length (duration) of the high-speed phase can be made longer than the relative length of the low-speed phase. Conversely, in order to reduce the cooling capacity of the freezer, the duration of the high-speed phase can be made shorter than the duration of the low-speed phase.

[0034] Figure 3 The compressor according to the above exemplary embodiment is shown to operate cyclically in a dual speed mode. The duration of the cycle can typically be a constant parameter named CYCLE_LENGTH. In addition, in normal operation, the high speed and low speed (named HIGH_SPEED and LOW_SPEED) values ​​of the compressor can be set to be constant, where LOW_SPEED<=HIGH_SPEED<=MAX_SPEED, where MAX_SPEED is the upper limit of the compressor speed determined based on the data table, noise limitation considerations or other limitations. The value of the LOW_SPEED constant parameter is determined based on data table considerations, or can be set to be higher than the lowest operating speed of the compressor to achieve on-off operation under all operating conditions.

[0035] During operation, HIGH_SPEED may deviate from its constant predetermined value. This may occur, for example, when a user-selectable function is triggered. For example, in Ultra Freeze mode, HIGH_SPEED may be set to the maximum speed of the compressor. HIGH_SPEED may also deviate based on other triggering events. In one cycle, the area under the speed curve corresponds to the total cooling capacity delivered by the compressor in both chambers. Therefore, the total cooling is

[0036] K_TOT=HIGH_SPEED*HS_LENGTH+LOW_SPEED*LS_LENGTH

[0037] Among them, K_TOT is the total cooling capacity, HIGH_SPEED is the cooling power of the compressor at high speed, HS_LENGTH is the duration of the high speed stage, LOW_SPEED is the cooling power of the low speed stage, and LS_LENGTH is the duration of the low speed stage.

[0038] In addition, the normalized total cooling capacity is

[0039] Q_TOT=K_TOT / (MAX_SPEED*CYCLE_LENGTH)

[0040] Where MAX_SPEED is the cooling power of the compressor at maximum speed and CYCLE_LENGTH is the total length of the compressor cycle.

[0041] In other words, this is the ratio between the cooling capacity delivered in the cycle and the maximum cooling capacity that can be delivered by the compressor if it runs continuously at maximum speed. Further, the normalized relative duration of the low speed phase with respect to the high speed phase can be defined as:

[0042] Q_REL=LS_LENGTH / (HS_LENGTH+LS_LENGTH)

[0043] Among them, LS_LENGTH and HS_LENGTH are the duration of the low-speed stage and the duration of the high-speed stage respectively.

[0044] exist Figure 4 and Figure 5 In both cases, the total cooling capacity K_TOT is the same, but the cooling capacity distribution between the freezer and refrigerator compartments is different. It should be noted that in one cycle, the area under the speed curve is the same.

[0045] exist Figure 4 In the depicted scenario, the low-speed phase of greater relative length (duration) corresponds to a much higher cooling capacity delivered to the cold storage compartment. Figure 5The scenario depicted in represents a situation where the cooling capacity is allocated more to the freezer compartment.

[0046] A control algorithm is implemented in the appliance controller 50 (microprocessor) so that sensor feedback is collected, user set points for the rooms are received, and the speed of the compressor and fan (if present) is controlled.

[0047] exist Figure 6 The flowchart of FIG. 6 shows some steps performed by the controller 50 when controlling the cooling of the refrigerator. First, in step 601, the relative length Q_REL of the low speed phase and the high speed phase is determined. This can be performed based on a feedback regulator that uses a weighted difference in the temperature errors of the two chambers, possibly using a time-varying weight W_REL_FZ for the freezer and a time-varying weight W_REL_FF for the refrigerator.

[0048] Next, in step 603, a normalized total cooling capacity requirement Q_TOT is determined. This can be achieved based on a feedback regulator using a weighted sum of the two compartment temperature errors, possibly using a time-varying weight W_TOT_FZ for the freezer compartment and a time-varying weight W_TOT_FF for the refrigerator compartment.

[0049] Next, in step 605, the duration of the compressor on time in each cycle is determined. In addition, the duration of the high speed phase HS_LENGTH and the duration of the low speed phase LS_LENGTH are determined. The duration of the high speed phase and the duration of the low speed phase can be determined by the values ​​of Q_TOT and Q_REL calculated in the previous step.

[0050] Finally, in step 607, the compressor is operated according to the determined parameter values ​​of the durations of the high speed phase and the low speed phase.

[0051] The regulator used in steps 601 and 603 may be a PI or PID type regulator, an observer-based regulator, an adaptive controller, a model predictive controller, or any kind of suitable feedback regulator.

[0052] Can be used Figure 7Q_REL is determined by the feedback control scheme depicted in . Here, the chamber error is determined by subtracting the chamber sensor feedback from the chamber set points, which can be user-selectable constants or determined by some functional program. The weights W_REL_FZ and W_REL_FF can be changed dynamically to give more importance to one error or the other. Under some conditions, one weight can be set to 0 to force the regulator to adjust the error of only one of the chambers. Typical values ​​are W_REL_FZ=1 and W_REL_FF=0.5 to give higher priority to the freezer chamber regulation, as the freezer chamber may be more susceptible to changes in the relative duration of high speed phases and low speed phases.

[0053] Can be used Figure 8 The feedback control scheme shown in determines Q_REL.

[0054] The weights W_TOT_FZ and W_TOT_FF can be changed dynamically to give more importance to one error or the other. Under some conditions, one weight can be set to 0 to force the regulator to adjust the error of only one of the chambers. Typical values ​​are W_TOT_FZ = 0.5 and W_TOT_FF = 0.5 to balance the effects of the regulators.

[0055] Using the values ​​of Q_TOT and Q_REL calculated by the feedback regulator, the duration of the low speed phase and the duration of the high speed phase can then be calculated according to the following formula:

[0056]

[0057] Furthermore, if fans are provided in one or both chambers, dedicated control loops may be used to improve temperature regulation in the chambers.

[0058] In particular, the speed regulator of the refrigerator compartment may operate not only taking into account the error of the refrigerator compartment, but also combining the errors of both the refrigerator compartment and the freezer compartment according to the freezer compartment weight W_FAN_FZ and the refrigerator compartment weight W_FAN_FF. In fact, due to the thermodynamic setting of the series evaporator system, the increase of evaporation in the refrigerator compartment due to the higher fan speed may have a negative impact on the evaporation of the freezer evaporator, thereby reducing its cooling capacity.

[0059] therefore, Fig. 9 An exemplary control scheme is shown for using the combined temperature errors from both chambers to determine the speed of the refrigeration fan (if present).

[0060] Fig.10 An exemplary control scheme is shown for using the temperature error from the chamber to determine the speed of the refrigeration fan (if present).

[0061] Further, the controller 50 may be implemented using suitable hardware and / or software. Fig.11 An exemplary controller is depicted in . The hardware may include one or more processors 501 that may be arranged to execute software stored in a readable storage medium 502. The processor may be implemented by a single dedicated processor, a single shared processor, or multiple separate processors (some of which may be shared or distributed). In addition, the processor may include, but is not limited to, digital signal processor (DSP) hardware, ASIC hardware, read-only memory (ROM), random access memory (RAM), and / or other storage media. The controller 50 is suitable for sending and receiving signals from other entities (such as temperature sensors 41, 42) and other different internal and / or external sensors or other units in some embodiments using an interface 503.

[0062] Temperature control for a dual-chamber refrigerator (freezer and refrigerator) can be achieved using a refrigerator as described herein, which is equipped with a variable speed compressor, a condenser heat exchanger and two evaporators in series, wherein the outlet of the freezer evaporator is connected to the inlet of the refrigerator evaporator. The refrigerator can be used in both static rooms and in rooms with additional evaporators or recirculation fans. Both rooms can be provided with air temperature sensors. No atmospheric temperature sensor is required.

Claims

1. A refrigerator (10), comprising: - a freezer compartment (16), - cold storage room (12), - a cooling system (30) comprising a variable speed compressor (32), a condenser (34), and at least a first freezing evaporator (37) and a second refrigerating evaporator (38), wherein the freezing evaporator (37) and the second refrigerating evaporator (38) are connected in series so that the outlet of the freezing evaporator (37) is connected to the inlet of the refrigerating evaporator (38), The refrigerator further comprises - A controller (50) configured to control the cooling system (30) by periodically switching the variable speed compressor (32) between an on phase and an off phase, wherein the controller (50) is configured to control the variable speed compressor (32) to a high speed state during the on phase and then to a low speed state, wherein the speed of the variable speed compressor (32) in the low speed state is lower than the speed in the high speed state.

2. The refrigerator (10) according to claim 1, wherein: The duration of each cycle having an on phase and an off phase is constant.

3. The refrigerator (10) according to claim 1 or 2, wherein: The speeds of the variable speed compressor in the high speed state and the low speed state are respectively constant predetermined speeds.

4. The refrigerator (10) according to claim 3, wherein: The controller is configured to deviate a speed of the variable speed compressor in the high speed state from the constant speed based on a triggering event.

5. The refrigerator (10) according to any one of claims 1 to 4, wherein: A fan (43, 44) is provided in at least one of the freezing chamber (16) and the refrigerating chamber (12), and wherein the controller (50) is configured to control the speed of the fan (43, 44).

6. The refrigerator (10) according to claim 5, wherein: The controller (50) is configured to control the speed of the fans (43, 44) based on a weighted linear combination of temperature errors of the refrigerator compartment and the freezer compartment.

7. The refrigerator (10) according to any one of claims 1 to 6, wherein: The controller is configured to calculate a cooling capacity set point of the compressor based on a weighted combination of temperature errors of the refrigerating compartment and the freezing compartment.

8. The refrigerator (10) according to any one of claims 1 to 7, wherein: The controller is configured to calculate relative durations of the high speed phase and the low speed phase based on a weighted combination of temperature errors of the refrigerating chamber and the freezing chamber.

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