Refrigerator, refrigeration system, and control method thereof

Abstract

To provide a refrigeration system that can eliminate liquid backflow into the compressor. [Solution] The refrigerator comprises an inverter that outputs a variable-frequency AC voltage for driving the compressor, a pressure detection means for detecting the refrigerant pressure on the low-pressure side of the piping between the refrigerator and the heat exchanger on the user side, and a controller that controls the output frequency of the inverter. The controller opens the on-off valve when the temperature of the load of the heat exchanger on the user side is above a target value, and closes the on-off valve when the temperature of the load is below the target value; in conjunction with the opening of the on-off valve, the controller controls the output frequency of the inverter so that the compressor is turned on and the detected pressure of the pressure detection means remains constant at a threshold; in conjunction with the closing of the on-off valve, the controller controls the output frequency of the inverter so that the output frequency of the inverter is kept above a set value, and the compressor is turned off when the detected pressure of the pressure detection means falls below a predetermined value.

Description

Technical Field

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[0001] Embodiments of the present invention relate to a refrigerator including a compressor, a refrigeration device including the refrigerator and a user-side device, and a control method for the refrigeration device.

Background Art

[0002] There is known a refrigeration device including a refrigerator including a compressor and an outdoor heat exchanger, and a user-side device including a user-side heat exchanger, pipe-connecting the refrigerator and the user-side device, providing an on-off valve in the pipe, controlling the opening and closing of the on-off valve according to the load of the user-side device, and controlling the operation of the compressor as the on-off valve opens and closes.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above refrigeration device, when the on-off valve is closed, refrigerant may remain and liquefy on the low-pressure side of the user-side heat exchanger or the pipe, and the liquid refrigerant may flow into the compressor when the next compressor is turned on, causing so-called liquid backflow. This liquid backflow has an adverse effect on the life of the compressor.

[0005] An object of the embodiment is to provide a refrigerator, a refrigeration device, and a control method for the refrigeration device that can eliminate liquid backflow to the compressor.

Means for Solving the Problems

[0006] The refrigerator according to claim 1 includes a compressor that sucks in, compresses, and discharges a refrigerant, and an outdoor heat exchanger, which passes the refrigerant discharged from the compressor through the outdoor heat exchanger and through an on-off valve, a pressure reducer, and a utilization-side heat exchanger connected to the outdoor heat exchanger by piping, and returns it to the compressor, and comprises an inverter that outputs a variable-frequency AC voltage for driving the compressor, pressure detection means for detecting the refrigerant pressure on the low-pressure side of the piping, and a controller that controls the output frequency of the inverter. The controller opens the on-off valve when the temperature of the load of the utilization-side heat exchanger is above a target value, and closes the on-off valve when the temperature of the load is below the target value; controls the output frequency of the inverter so that the compressor is turned on and the detected pressure of the pressure detection means is constant when the on-off valve is opened; and controls the output frequency of the inverter so that the output frequency of the inverter is kept above a set value when the on-off valve is closed, and the compressor is turned off when the detected pressure of the pressure detection means falls below a predetermined value. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a block diagram showing the configuration of one embodiment. [Figure 2] Figure 2 is a flowchart illustrating the control of one embodiment. [Figure 3] Figure 3 is a time chart showing the temporal changes in internal temperature, thermostat operation, on-off valve operation, operating frequency F, and low-pressure side pressure Ps in one embodiment. [Modes for carrying out the invention]

[0008] Hereinafter, one embodiment of this invention will be described with reference to the drawings. As shown in Figure 1, the refrigeration system is composed of refrigerator A and user-side equipment B.

[0009] Refrigeration unit A includes a compressor 1 that sucks in, compresses, and discharges refrigerant, an outdoor heat exchanger (condenser) 2 that releases the heat of the refrigerant discharged from the compressor 1 into the outside air, and an outdoor fan 3 that supplies outside air to the outdoor heat exchanger 2. It is connected to a three-phase AC power supply (first AC power supply) 10 and operates using the three-phase AC voltage of the three-phase AC power supply 10.

[0010] User-side equipment B is, for example, a freezer display case, a refrigerated display case, or a prefabricated storage unit, and includes an on / off valve (also called a two-way valve) 21, a pressure reducer such as an expansion valve 22, a user-side heat exchanger (evaporator) 23 that performs heat exchange between the storage unit air and the refrigerant, and a storage unit fan 24 that supplies storage unit air to the user-side heat exchanger 23. It is connected to a three-phase AC power supply (second AC power supply) 20 that is different from the three-phase AC power supply 10, and the storage unit fan 24 is operated by the three-phase AC voltage of the three-phase AC power supply 20.

[0011] A compressor 1, an outdoor heat exchanger 2, an on-off valve 21, an expansion valve 22, and a utilization-side heat exchanger 23 are connected by piping, and a refrigeration cycle is configured in which the refrigerant discharged from the compressor 1 is passed through the outdoor heat exchanger 2, the on-off valve 21, the expansion valve 22, and the utilization-side heat exchanger 23 as shown by the arrows in the figure, and returned to the compressor 1.

[0012] The refrigerant (liquid refrigerant) that has condensed after releasing heat to the outside air in the outdoor heat exchanger 2 flows through the liquid-side piping (also called the liquid-side refrigerant piping) 4 to the on / off valve 21, and the refrigerant (gas refrigerant) that has evaporated after absorbing heat from the air inside the chamber in the utilization-side heat exchanger 23 flows through the gas-side piping (also called the gas-side refrigerant piping) 5 to the intake port of the compressor 1.

[0013] The on-off valve 21 is an electromagnetic on-off valve, connected to the controller 15 of the outdoor unit A (described later) via a signal line L1. It operates and opens when an operating voltage is supplied from the controller 15 via the signal line L1, and closes when that operating voltage is interrupted.

[0014] The refrigerator A further includes a DC power supply circuit (rectifier circuit) 11 that converts the three-phase AC voltage of the three-phase AC power supply 10 into a DC voltage, an inverter 12 that converts the output voltage of the DC power supply circuit 11 into a frequency-variable AC voltage and outputs it for driving the motor 1M of the compressor 1, an inverter 13 that converts the output voltage of the DC power supply circuit 11 into a frequency-variable AC voltage and outputs it for driving the motor of the outdoor fan 3, a pressure detector (pressure detection means) 14 that detects the refrigerant pressure Ps on the low-pressure side of the gas-side piping 5, and a controller 15.

[0015] The frequency of the AC voltage output from the inverter 12 is called the output frequency F. By changing this output frequency F, the capacity of the compressor 1 changes.

[0016] The user-side equipment B further includes a power supply circuit 25 that converts the three-phase AC voltage of the three-phase AC power supply 20 into a voltage for driving the internal fan 24 and outputs it, and a thermostat 26. The thermostat 26 is a mechanical contact that turns on when the internal temperature (load temperature) Ta, which is the load of the user-side heat exchanger 23, is above a target value and turns off when the internal temperature Ta is below the target value, and is connected to the controller 15 of the outdoor unit A via a signal line L2.

[0017] The controller 15 controls the opening and closing of the on-off valve 21 of the user-side equipment B according to the operating state of the thermostat 26 corresponding to the internal temperature Ta of the user-side equipment B, and also controls the output frequency F of the inverter 12 according to the opening and closing of the on-off valve 21 and the pressure Ps detected by the pressure sensor 14, and its main functions include the following control means (1) to (3).

[0018] (1) A first control means that opens the on-off valve 21 when the thermostat 26 is ON (internal temperature Ta is above the target value) and closes the on-off valve 21 when the thermostat 26 is OFF (internal temperature Ta is below the target value).

[0019] (2) Second control means for controlling the output frequency F of the inverter 12 such that the compressor 1 is turned on as the on-off valve 21 is opened and the detected pressure Ps of the pressure detector 14 becomes constant at the threshold value Ps2. Specifically, the second control means controls the output frequency F of the inverter 12 such that the compressor 1 is turned on when the detected pressure Ps of the pressure detector 14 rises above the threshold value Ps2 (or when a predetermined time t has elapsed) after the on-off valve 21 is opened and the detected pressure Ps of the pressure detector 14 becomes constant at the threshold value Ps2.

[0020] (3) Third control means for controlling the output frequency F of the inverter 12 to keep the output frequency F of the inverter 12 above a predetermined set value Fs as the on-off valve 21 is closed and turning off the compressor 1 when the detected pressure Ps of the pressure detector 14 drops below a predetermined value Ps1.

[0021] Next, the control executed by the controller 15 will be described while referring to the flowchart of FIG. 2 and the time chart of FIG. 3.

[0022] When the thermostat 26 is turned off (the temperature Ta inside the storage is lower than the target value) (YES in S1 of thermo-off), the controller 15 closes the on-off valve 21 (S2). By closing this on-off valve 21, the flow of refrigerant from the refrigerator A to the utilization-side device B stops.

[0023] As the on-off valve 21 is closed, the controller 15 keeps the output frequency F of the inverter 12 above the set value Fs (S3). That is, if the output frequency F of the inverter 12 when the on-off valve 21 is closed is in a state where it is above the set value Fs, the output frequency F is maintained as it is. If the output frequency F of the inverter 12 when the on-off valve 21 is closed is in a state where it is below the set value Fs, the output frequency F is maintained at the set value Fs.

[0024] When the shut-off valve 21 is closed, refrigerant remains in the user-side heat exchanger 23 and gas piping 5. However, since the output frequency F of the inverter 12 is kept above the set value Fs, the remaining refrigerant can be reliably recovered into the compressor 1. Consequently, liquid backflow into the compressor 1 when it is turned on again can be avoided.

[0025] In this way, while maintaining the output frequency F of the inverter 12 at or above the set value Fs, the controller 15 determines whether or not the detected pressure Ps of the pressure sensor 14 has fallen to or below a predetermined value Ps1 (S4).

[0026] When the pressure Ps detected by the pressure sensor 14 drops to a predetermined value Ps1 or less (YES in S4), the controller 15 sets the output frequency F of the inverter 12 to zero so that the compressor 1 is turned off (S5).

[0027] Subsequently, when the internal temperature Ta rises above the target value and the thermostat 26 turns on (thermo-on; NO in S1), the controller 15 opens the shut-off valve 21 (S6). Opening this shut-off valve 21 resumes the flow of refrigerant from the refrigerator A to the user equipment B.

[0028] After the on-off valve 21 is opened, the controller 15 determines whether the pressure Ps detected by the pressure sensor 14 has risen to or above the threshold Ps2 (S7). If the pressure Ps detected by the pressure sensor 14 is less than the threshold Ps2 (NO in S7), the controller 15 repeats the determination in S7 (standby).

[0029] When the pressure Ps detected by the pressure sensor 14 rises above the threshold Ps2 (YES in S7), the controller 15 increases the output frequency F of the inverter 12 to turn on the compressor 1 (S8), and controls the output frequency F of the inverter 12 so that the pressure Ps detected by the pressure sensor 14 remains constant at the threshold Ps2 (S9). This constant control allows the capacity of the compressor 1 to be set to an optimal state corresponding to the load of the user-side equipment B (the load of the user-side heat exchanger 23), thereby improving energy efficiency.

[0030] In this way, the compressor 1 is not turned on at the same time as the opening of the shut-off valve 21. Instead, the flow of refrigerant to the user-side heat exchanger 23 begins when the shut-off valve 21 opens, and the compressor 1 is turned on when the low-pressure side pressure Ps of the refrigerant in the gas piping 5 rises above the threshold Ps2. This eliminates the problem of refrigerant rapidly flowing into the suction port of the compressor 1. It does not adversely affect the lifespan of the compressor 1.

[0031] Since the on-off valve 21 of user-side equipment B is connected to the controller 15 of refrigerator A via a signal line, and the operating voltage for the on-off valve 21 is supplied directly from the controller 15 of refrigerator A, there is no need to provide a drive circuit for the on-off valve 21 in user-side equipment B, thus simplifying the configuration of user-side equipment B and reducing costs accordingly.

[0032] Since the thermostat 26 of user-side equipment B is connected via a signal line to the controller 15 of chiller A, and the status of the thermostat 26 is directly monitored by the controller 15 of chiller A, there is no need to provide a monitoring function for the thermostat 26 in user-side equipment B, which simplifies the configuration of user-side equipment B and reduces costs accordingly.

[0033] In the above embodiment, the compressor 1 is turned on when the low-pressure side pressure Ps rises to or above the threshold Ps2 after the on-off valve 21 is opened. However, the compressor 1 may be turned on after a predetermined time t has elapsed after the on-off valve 21 is opened.

[0034] Furthermore, the above embodiments and modifications are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments and modifications can be implemented in a variety of other forms, and various omissions, rewrites, and changes can be made without departing from the spirit of the invention. These embodiments and variations are included in the spirit of the invention and are included in the scope of the invention and its equivalents as described in the claims. [Explanation of symbols]

[0035] 1... Compressor, 2... Outdoor heat exchanger, 4... Liquid side piping, 5... Gas side piping, 12... Inverter, 14... Pressure sensor, 15... Controller, 21... On / off valve, 22... Expansion valve (pressure reducer), 23... Utilization side heat exchanger, 26... Thermostat.

Claims

1. A refrigerator comprising a compressor that draws in, compresses, and discharges a refrigerant, and an outdoor heat exchanger, wherein the refrigerant discharged from the compressor is passed through the outdoor heat exchanger and returned to the compressor via an on-off valve, a pressure reducer, and a utilization-side heat exchanger connected to the outdoor heat exchanger via piping, An inverter that outputs a frequency-variable AC voltage for driving the compressor, A pressure detection means for detecting the refrigerant pressure on the low-pressure side of the aforementioned piping, A controller that controls the output frequency of the inverter, Equipped with, The aforementioned controller, The valve is opened when the temperature of the load on the user-side heat exchanger is above the target value, and the valve is closed when the temperature of the load is below the target value. Upon opening the aforementioned valve, the compressor is turned on and the output frequency of the inverter is controlled so that the pressure detected by the pressure detection means becomes constant. When the on / off valve is closed, the output frequency of the inverter is maintained above a set value, and the output frequency of the inverter is controlled so that the compressor turns off when the pressure detected by the pressure detection means falls below a predetermined value. Refrigeration unit.

2. The controller controls the output frequency of the inverter so that the compressor is turned on and the detected pressure of the pressure detection means remains constant at the threshold after the opening of the on / off valve, after the detected pressure of the pressure detection means rises above the threshold, or after a predetermined time has elapsed. The refrigerator according to claim 1.

3. The aforementioned heat exchanger on the user side is included in the user-side equipment connected via a signal line to the controller of the refrigerator. The user-side equipment includes a thermostat that turns on when the temperature of the load on the user-side heat exchanger is equal to or greater than the target value, and turns off when the temperature of the load is less than the target value. The refrigerator according to claim 1.

4. The connection of the aforementioned piping constitutes a refrigeration cycle in which the refrigerant discharged from the compressor is passed through the outdoor heat exchanger, the on / off valve, and the utilization-side heat exchanger and returned to the compressor. The refrigerator according to claim 1.

5. The aforementioned heat exchanger on the user side is included in the user-side equipment connected via a signal line to the controller of the refrigerator. The aforementioned refrigerator is connected to a first AC power supply and operates using the AC voltage of the first AC power supply. The user-side equipment is connected to a second AC power source different from the first AC power source and operates using the AC voltage of the second AC power source. The refrigerator according to claim 1.

6. The aforementioned on-off valve is connected to the controller of the refrigerator via a signal line, and opens when it receives an operating voltage from the controller via the signal line, and closes when the operating voltage is interrupted. The refrigerator according to claim 5.

7. A refrigerator including a compressor that sucks in, compresses, and discharges refrigerant, and an outdoor heat exchanger, User-side equipment including on-off valves and user-side heat exchangers, A refrigeration cycle is provided in which the compressor, the outdoor heat exchanger, the on-off valve, and the utilization-side heat exchanger are connected by piping, and the refrigerant discharged from the compressor is passed through the outdoor heat exchanger, the on-off valve, and the utilization-side heat exchanger and returned to the compressor. An inverter that outputs a frequency-variable AC voltage for driving the compressor, A pressure detection means for detecting the refrigerant pressure on the low-pressure side of the aforementioned piping, A controller that controls the output frequency of the inverter, Equipped with, The aforementioned controller, The valve is opened when the temperature of the load on the user-side heat exchanger is above the target value, and the valve is closed when the temperature of the load is below the target value. Upon opening the aforementioned valve, the compressor is turned on and the output frequency of the inverter is controlled so that the pressure detected by the pressure detection means becomes constant. When the on / off valve is closed, the output frequency of the inverter is maintained above a set value, and the output frequency of the inverter is controlled so that the compressor turns off when the pressure detected by the pressure detection means falls below a predetermined value. Refrigeration equipment.

8. A refrigerator including a compressor that sucks in, compresses, and discharges refrigerant, and an outdoor heat exchanger, User-side equipment including on-off valves and user-side heat exchangers, A refrigeration cycle is provided in which the compressor, the outdoor heat exchanger, the on-off valve, and the utilization-side heat exchanger are connected by piping, and the refrigerant discharged from the compressor is passed through the outdoor heat exchanger, the on-off valve, and the utilization-side heat exchanger and returned to the compressor. An inverter that outputs a frequency-variable AC voltage for driving the compressor, A pressure detection means for detecting the refrigerant pressure on the low-pressure side of the aforementioned piping, A controller that controls the output frequency of the inverter, A control method for a refrigeration system, comprising: The valve is opened when the temperature of the load on the user-side heat exchanger is above the target value, and the valve is closed when the temperature of the load is below the target value. Upon opening the aforementioned valve, the compressor is turned on and the output frequency of the inverter is controlled so that the pressure detected by the pressure detection means becomes constant. When the on / off valve is closed, the output frequency of the inverter is maintained above a set value, and the output frequency of the inverter is controlled so that the compressor turns off when the pressure detected by the pressure detection means falls below a predetermined value. A method for controlling a refrigeration system.

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