EP3264008A1

EP3264008A1 - Freezing device

Info

Publication number: EP3264008A1
Application number: EP15885373.9A
Authority: EP
Inventors: Takeshi Ito; Kazuyuki Tsukamoto; Masaaki Kamikawa
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2015-03-13
Filing date: 2015-03-13
Publication date: 2018-01-03
Anticipated expiration: 2035-03-13
Also published as: WO2016147275A1; EP3264008B1; TWI589821B; EP3264008A4; JPWO2016147275A1; JP6370470B2; TW201632813A

Abstract

A controller of a refrigeration apparatus includes a temperature determination unit configured to determine whether a heat radiating unit temperature is within a target temperature range, a superheat degree calculation unit configured to calculate a degree of superheat of refrigerant flowing through an economizer from a state of refrigerant detected in a state detection unit, and an opening degree control unit configured, when the temperature determination unit determines that the heat radiating unit temperature is within the target temperature range, to control an opening degree of a flow rate regulation device so that the degree of superheat calculated in the superheat degree calculation unit reaches a target degree of superheat, and configured, when the temperature determination unit determines that the heat radiating unit temperature is outside the target temperature range, to control an opening degree of the flow rate regulation device so that the heat radiating unit temperature falls within the target temperature range.

Description

Technical Field

The present invention relates to a refrigeration apparatus including an inverter heat radiating unit that cools an inverter device used for driving a compressor.

Background Art

In recent years, a refrigeration apparatus has been proposed in which an inverter controls an operating frequency of a compressor to enhance partial load efficiency. When alternating-current power supplied from a commercial power supply is converted and applied to the compressor, electrical losses in a rectifier circuit, a smoothing capacitor, and an inverter circuit, for example, are transformed into heat (hereinafter referred to as heat generated by the inverter).
As a method of dissipating the heat generated by an inverter, a method has been proposed in which an inverter heat radiating unit is cooled by using refrigerant (see Patent Literatures 1 and 2, for example). Patent Literature 1 discloses a refrigeration apparatus including a cooling refrigerant flow passage that branches off from a refrigerant circulation passage and communicates with a compressor body through an inverter. Patent Literature 2 discloses a method in which a bypass cooling circuit for cooling an inverter heat radiating unit is provided within a refrigerant circuit and in which the amount of refrigerant that passes through the inverter heat radiating unit is controlled based on the temperature of the inverter heat radiating unit.

Citation List

Patent Literature

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2003-21406
Patent Literature 2: Japanese Unexamined Patent Application Publication No. 2008-57875

Summary of Invention

Technical Problem

As in refrigeration apparatuses disclosed in Patent Literatures 1 and 2 described above, for example, when refrigerant having a temperature corresponding to a saturated gas temperature at a suction pressure is used for cooling an inverter heat radiating unit, or when an inverter is installed in an area that is likely to be affected by a suction gas temperature, such as in the proximity of a motor frame, condensation may occur on an inverter frame during operation at a low suction gas temperature (for example, 0 degrees C), thereby impairing a function of an inverter circuit in some cases.
Incidentally, a possible method is to cool the inverter heat radiating unit by using refrigerant gas having passed through an economizer (subcooler). In this case, the amount of refrigerant that passes through the economizer is controlled based on the temperature of the inverter heat radiating unit. Thus, when the amount of refrigerant that passes through the economizer and cools the inverter is small, the economizer is not able to be used effectively, thereby resulting in a reduction in capacity in some cases.
The present invention has been made to overcome such drawbacks and provides a refrigeration apparatus that prevents condensation from occurring in an inverter device and also controls a reduction in capacity due to the fact that an economizer is prevented from being used effectively.

Solution to Problem

A refrigeration apparatus according to one embodiment of the present invention A refrigeration apparatus comprising: a refrigerant circuit in which a compressor configured to compress refrigerant, a condenser configured to cause the refrigerant discharged from the compressor to reject heat and cool, an economizer configured to subcool the refrigerant having flowed out of the condenser, an expansion device configured to reduce pressure of and expand the refrigerant subcooled in the economizer, and an evaporator configured to cause the refrigerant reduced in pressure and expanded in the expansion device to receive heat and evaporate, are connected by a refrigerant pipe; an inverter device configured to drive the compressor; an inverter heat radiating unit configured to reject heat generated in the inverter device; an inverter cooling circuit including a subcooling circuit in which a refrigerant flow passage is formed that branches off from between the economizer and the expansion device, extends through the economizer and the inverter heat radiating unit, and then extends into the compressor; a flow rate regulation device provided in the inverter cooling circuit and configured to regulate a flow rate of refrigerant that is to flow into the inverter heat radiating unit; an inverter temperature detection device configured to detect a temperature of the inverter heat radiating unit as a heat radiating unit temperature; a state detection unit configured to detect a state of refrigerant flowing through the economizer; and a controller configured to, based on the heat radiating unit temperature detected in the inverter temperature detection device and the state of refrigerant flowing through the economizer detected by the state detection unit, control action of the flow rate regulation device, wherein the controller includes a temperature determination unit configured to determine whether the heat radiating unit temperature is within a target temperature range, a superheat degree calculation unit configured to calculate a degree of superheat of refrigerant flowing through the economizer from the state of refrigerant detected in the state detection unit, and an opening degree control unit configured to, when the temperature determination unit determines that the heat radiating unit temperature is within the target temperature range, control an opening degree of the flow rate regulation device so that the degree of superheat calculated in the superheat degree calculation unit reaches a target degree of superheat, and configured to, when the temperature determination unit determines that the heat radiating unit temperature is outside the target temperature range, control the opening degree of the flow rate regulation device so that the heat radiating unit temperature falls within the target temperature range.

Advantageous Effects of Invention

According to the refrigeration apparatus of one embodiment of the present invention, the opening degree of the flow rate regulation device is controlled based on the degree of superheat when the heat radiating unit temperature is within the target temperature range, and the opening degree of the flow rate regulation device is controlled based on the heat radiating unit temperature when the heat radiating unit temperature is outside the target temperature range. This can control a reduction in capacity due to insufficiency in effective use of the economizer and also prevent condensation from occurring during cooling the inverter device. Brief Description of Drawings

[Fig. 1] Fig. 1 is a refrigerant circuit diagram of a refrigeration apparatus according to Embodiment 1 of the present invention.
[Fig. 2] Fig. 2 is a functional block diagram illustrating an example of a controller in the refrigeration apparatus of Fig. 1.
[Fig. 3] Fig. 3 is a flowchart illustrating an example of the action of the refrigeration apparatus of Fig. 1.
[Fig. 4] Fig. 4 is a refrigerant circuit diagram illustrating a refrigeration apparatus according to Embodiment 2 of the present invention.
[Fig. 5] Fig. 5 is a refrigerant circuit diagram illustrating a refrigeration apparatus according to Embodiment 3 of the present invention.
[Fig. 6] Fig. 6 is a flowchart illustrating an example of the action of the refrigeration apparatus of Fig. 5.

Description of Embodiments

Embodiment 1

Embodiments of a refrigeration apparatus of the present invention will be described below with reference to the drawings. Fig. 1 is a refrigerant circuit diagram of a refrigeration apparatus according to Embodiment 1 of the present invention. As illustrated in Fig. 1, a refrigeration apparatus 1 includes a compressor 2, an oil separator 3, a condenser 4, an economizer 5, an expansion device 6, and an evaporator 7, and these are connected by a refrigerant pipe to constitute a refrigerant circuit 1A through which refrigerant circulates.
The compressor 2 is composed of a screw compressor, for example, and compresses and discharges refrigerant. The compressor 2 includes a mechanism unit 2a including a compressor element and an electric-powered element that are housed in an airtight container. The type of the compressor 2 is not limited to the screw compressor and may be a vane compressor, a rotary compressor, or a single-stage or multi-stage compressor, for example. The compressor 2 is driven by an inverter device 20. The oil separator 3 separates refrigerating machine oil contained in refrigerant discharged from the compressor 2, and the separated refrigerating machine oil returns to the compressor 2 again. The condenser 4 is a heat exchanger that causes the refrigerant that has been discharged from the compressor 2 and from which oil has been separated in the oil separator 3 to reject heat and cool.
The economizer 5 is an inter-refrigerant heat exchanger that subcools the refrigerant having flowed out of the condenser 4. The expansion device 6 is composed of an electronic expansion valve, for example, and reduces the pressure of and expands the refrigerant subcooled in the economizer 5. The evaporator 7 is a heat exchanger that causes the refrigerant reduced in pressure and expanded in the expansion device 6 to receive heat and evaporate.
The refrigeration apparatus 1 also includes the inverter device 20 that drives the compressor 2, and an inverter heat radiating unit 12 that transfers heat generated in the inverter device 20. The inverter device 20 and the inverter heat radiating unit 12 are integrally formed, and the inverter heat radiating unit 12 is provided so as to be integral with the compressor 2. For example, in the compressor 2, the inverter heat radiating unit 12 is formed on the outer surface of the airtight container of the mechanism unit 2a, and, on the inverter heat radiating unit 12, a heat-generating component, such as the inverter device 20, is placed together with a rectifier circuit and a smoothing capacitor. The inverter heat radiating unit 12 is composed of a heat sink in which a flow passage is formed, for example, and cools the inverter device 20 by causing refrigerant to flow therethrough.
The refrigeration apparatus 1 includes an inverter cooling circuit 10 that causes refrigerant to flow through the above-described inverter heat radiating unit 12, and a flow rate regulation device 11 that is provided in the inverter cooling circuit 10 and regulates a flow rate of refrigerant that is to flow into the inverter heat radiating unit 12. The inverter cooling circuit 10 includes a subcooling circuit 10A and a bypass cooling circuit 10B. In the subcooling circuit 10A, a refrigerant flow passage that branches off from between the economizer 5 and the expansion device 6, extends through the economizer 5 and the inverter heat radiating unit 12, and then extends into the compressor 2 is formed. Then, part of refrigerant flowing from the economizer 5 to the expansion device 6 is diverted and reduced in pressure by a first expansion valve 11A, and then flows into the inverter heat radiating unit 12. When heat exchange with the refrigerant is performed in the inverter heat radiating unit 12, the inverter heat radiating unit 12 is cooled, and refrigerant gas is supplied to an intermediate-pressure space in the compressor 2.
In the bypass cooling circuit 10B, a refrigerant flow passage that branches off from between the economizer 5 and the expansion device 6, extends through the inverter heat radiating unit 12, and then extends into the compressor 2 is formed. The bypass cooling circuit 10B diverts part of refrigerant flowing from the economizer 5 to the expansion device 6, reduces the pressure of the refrigerant by using a second expansion valve 11B, and then causes the refrigerant to flow into the inverter heat radiating unit 12. Then, the inverter heat radiating unit 12 is cooled by exchanging heat with the refrigerant, a flow of the refrigerant merges with a flow of the refrigerant gas having passed through the first expansion valve 11A, and refrigerant gas is supplied to the intermediate-pressure space in the compressor 2.
That is, the inverter cooling circuit 10 includes the subcooling circuit 10A and the bypass cooling circuit 10B that cause refrigerant to flow through the inverter heat radiating unit 12. Then, in cooling the inverter heat radiating unit 12, refrigerant (for example, refrigerant gas at 20 to 30 degrees C) that is to flow to the intermediate-pressure space is used to cool the inverter heat radiating unit 12, thereby making it possible to prevent condensation from occurring on the inverter heat radiating unit 12. Furthermore, when the inverter heat radiating unit 12 is insufficiently cooled by the subcooling circuit 10A, the inverter cooling circuit 10 causes liquid refrigerant to flow through a bypass cooling circuit 10B side and can thus solve the insufficient cooling.
The flow rate regulation device 11 is provided in the inverter cooling circuit 10 and regulates a flow rate of refrigerant that is to flow through the inverter heat radiating unit 12. The flow rate regulation device 11 includes the first expansion valve 11A provided on a subcooling circuit 10A side, and the second expansion valve 11B and an valve 11C that are provided on the bypass cooling circuit 10B side. The first expansion valve 11A is composed of an electronic expansion valve, for example, and is provided between a branch point between the economizer 5 and the expansion device 6, and the economizer 5. When the opening degree of the first expansion valve 11A is regulated, a flow rate of refrigerant that is to flow from the economizer 5 to the inverter heat radiating unit 12 is controlled on the subcooling circuit 10A side.
The second expansion valve 11B is composed of an electronic expansion valve, for example, and is provided between a branch point between the economizer 5 and the expansion device 6, and the inverter heat radiating unit 12. The valve 11C is provided between the branch point between the economizer 5 and the expansion device 6, and the second expansion valve 11B. The second expansion valve 11B and the valve 11C constitute a bypass flow rate regulation device that controls a flow rate of refrigerant in the bypass cooling circuit 10B. Although the case where the second expansion valve 11B and the valve 11C are provided is illustrated, an electronic expansion valve capable of being fully closed may be used as the second expansion valve 11B, and the valve 11C may be omitted. When the opening degree of the second expansion valve 11B is regulated, a flow rate of refrigerant that is to flow to the inverter heat radiating unit 12 is controlled on the bypass cooling circuit 10B side. Furthermore, when opening and closing of the valve 11C are controlled, the flow of refrigerant to the bypass cooling circuit 10B is controlled.
An example of the action of the refrigeration apparatus 1 will be described with reference to Fig. 1. Refrigerant compressed in the compressor 2 is discharged from the compressor 2 and separated into refrigerant gas and oil in the oil separator 3, and the refrigerant gas flows into the condenser 4. The refrigerant gas having flowed into the condenser 4 is condensed into liquid refrigerant and subcooled through heat exchange in the economizer 5. The subcooled refrigerant is reduced in pressure in the expansion device 6 and then transferred to the evaporator 7. The refrigerant transferred to the evaporator 7 exchanges heat with air, for example, to turn into refrigerant gas and flows into the compressor 2.
Meanwhile, part of refrigerant flowing from the economizer 5 to the expansion device 6 is diverted to the inverter cooling circuit 10. Refrigerant diverted to the subcooling circuit 10A side of the inverter cooling circuit 10 is reduced in pressure in the first expansion valve 11A and turns into refrigerant gas through heat exchange between refrigerant and refrigerant in the economizer 5. Subsequently, the refrigerant cools the inverter device 20 in the inverter heat radiating unit 12 and then flows into the intermediate-pressure space in the compressor 2. Furthermore, refrigerant diverted to the bypass cooling circuit 10B side of the inverter cooling circuit 10 passes through the second expansion valve 11B and the valve 11C and cools the inverter heat radiating unit 12. Subsequently, a flow of the refrigerant merges with a flow of the refrigerant gas flowing through the subcooling circuit 10A, and the refrigerant is injected into the intermediate-pressure space in the compressor 2.
The above-described action of the refrigeration apparatus 1 is controlled by a controller 40, and the controller 40 performs control based on pieces of information detected by various sensors. Specifically, the refrigeration apparatus 1 includes a heat radiating unit temperature detection device 31, a state detection device (refrigerant temperature detection device 32a, intermediate-pressure detection device 32b), a suction temperature detection device 33, and a suction pressure detection device 34, for example.
The heat radiating unit temperature detection device 31 detects a temperature of the inverter heat radiating unit 12. The refrigerant temperature detection device 32a and the intermediate-pressure detection device 32b function as a state detection device that detects the state of refrigerant flowing through the inverter cooling circuit 10. The refrigerant temperature detection device 32a detects a temperature of refrigerant flowing through the economizer 5, that is, a temperature of refrigerant before flowing into the inverter heat radiating unit 12. The intermediate-pressure detection device 32b detects a pressure of an intermediate-pressure chamber space in the middle of a compression process in the compressor 2. The suction temperature detection device 33 detects a temperature of refrigerant gas to be sucked into the compressor 2. The suction pressure detection device 34 detects a pressure of refrigerant gas to be sucked into the compressor 2. Detection values detected in these detection devices are output to the controller 40.
Fig. 2 is a functional block diagram illustrating an example of the controller in the refrigeration apparatus of Fig. 1. The controller 40 of Fig. 2 is constituted by hardware, such as a circuit device that implements functions thereof, or an arithmetic unit, such as a microprocessor or CPU, and software run thereon. The controller 40 controls a flow rate of refrigerant that is to flow to the inverter cooling circuit 10 based on detection values detected in the heat radiating unit temperature detection device 31, the refrigerant temperature detection device 32a, and the intermediate-pressure detection device 32b, and includes a temperature determination unit 41, a superheat degree calculation unit 42, and an opening degree control unit 43.
The temperature determination unit 41 determines whether a heat radiating unit temperature Tr detected in the heat radiating unit temperature detection device 31 is within a target temperature range. In the target temperature range, for example, a lower limit Trl is set at 25 degrees C, and an upper limit Tru is set at 40 degrees C. The temperature determination unit 41 determines whether the heat radiating unit temperature Tr is within the target temperature range, above the upper limit Tru of the target temperature range, or below the lower limit Trl of the target temperature range. The superheat degree calculation unit 42 calculates a degree of superheat SH of refrigerant gas flowing through the economizer 5 from a temperature detected by the refrigerant temperature detection device 32a and a pressure detected in the intermediate-pressure detection device 32b.
The opening degree control unit 43 controls the action of the flow rate regulation device 11 based on a determination result obtained in the temperature determination unit 41. When the temperature determination unit 41 determines that the heat radiating unit temperature Tr is within the target temperature range, the opening degree control unit 43 controls an opening degree of the flow rate regulation device 11 so that the degree of superheat SH reaches a target degree of superheat. At this time, the opening degree control unit 43 permits the flow of refrigerant on the subcooling circuit 10A side of the inverter cooling circuit 10 and puts the valve 11C on the bypass cooling circuit 10B side into a closed state to stop the flow of refrigerant into the bypass cooling circuit 10B. Then, the opening degree control unit 43 controls the opening degree of the first expansion valve 11A on the subcooling circuit 10A side so that the degree of superheat SH reaches the target degree of superheat.
On the other hand, when the temperature determination unit 41 determines that the heat radiating unit temperature Tr is less than the lower limit Trl (for example, 25 degrees C) of the target temperature range, this determination means that cooling of the inverter heat radiating unit 12 is excessive. The opening degree control unit 43 switches a control target from the degree of superheat SH to the heat radiating unit temperature Tr and controls the opening degree of the first expansion valve 11A so that the heat radiating unit temperature Tr reaches or exceeds the lower limit Trl of the target temperature range.
Furthermore, when the temperature determination unit 41 determines that the heat radiating unit temperature Tr is greater than the upper limit Tru of the target temperature range, the opening degree control unit 43 determines that insufficient cooling of the inverter heat radiating unit 12 has occurred. The opening degree control unit 43 switches the control target from the degree of superheat SH to the heat radiating unit temperature Tr and controls an opening degree of the flow rate regulation device 11 so that the heat radiating unit temperature Tr falls within the target temperature range. At this time, the opening degree control unit 43 opens the valve 11C and causes refrigerant to flow through both the subcooling circuit 10A and the bypass cooling circuit 10B of the inverter cooling circuit 10. In this case, the temperature determination unit 41 changes the initially-set upper limit Tru of the target temperature range to a second upper limit Trus (for example, 35 degrees C) lower than the upper limit Tru.
Then, when the temperature determination unit 41 determines that the heat radiating unit temperature Tr is above the changed second upper limit Trus, the opening degree control unit 43 performs control so that the opening degree of the second expansion valve 11B is increased until the heat radiating unit temperature Tr reaches or falls below the second upper limit Trus. Subsequently, even when the heat radiating unit temperature Tr reaches or falls below the second upper limit Trus, the opening degree control unit 43 performs control so that the opening degree of the second expansion valve 11B is maintained until the heat radiating unit temperature Tr falls below the lower limit Trl of the target temperature range. Subsequently, when the heat radiating unit temperature Tr falls below the lower limit Trl of the target temperature range, the opening degree control unit 43 reduces the opening degree of the second expansion valve 11B. Then, when the opening degree of the second expansion valve 11B reaches a minimum opening degree, the opening degree control unit 43 closes the valve 11C to stop the flow of refrigerant through the bypass cooling circuit 10B.
Fig. 3 is a flowchart illustrating an example of the action of the refrigeration apparatus of Fig. 1. Processes illustrated in the flowchart of Fig. 3 are implemented at certain set control time intervals. First, based on a temperature detected by the refrigerant temperature detection device 32a and an intermediate pressure detected in the intermediate-pressure detection device 32b, a degree of superheat SH of refrigerant gas at a gas temperature detection area in the economizer 5 is calculated. The opening degree of the first expansion valve 11A is controlled so that the degree of superheat SH reaches a target degree of superheat (step ST11).
Here, the temperature determination unit 41 determines whether a heat radiating unit temperature Tr of the inverter heat radiating unit 12 is less than or equal to an upper limit Tru of a target temperature range (step ST12). When the heat radiating unit temperature Tr is less than or equal to the upper limit Tru of the target temperature range, it is determined that an operation state is a steady operation state in which the temperature of the inverter device 20 is appropriate. When the heat radiating unit temperature Tr is above the upper limit Tru of the target temperature range, it is determined that the inverter device 20 is in a superheat operation state.

When it is determined that an operation state is the steady operation state in which the heat radiating unit temperature Tr is less than or equal to the upper limit Tru of the target temperature range (YES in step ST12), the valve 11C is closed and the flow of refrigerant in the bypass cooling circuit 10B is stopped (step ST13). When the operation state has already been the steady operation state, the operation state is maintained. Subsequently, the controller 40 determines whether the heat radiating unit temperature Tr is greater than or equal to a lower limit Trl of the target temperature range (step ST14).
When the heat radiating unit temperature Tr is greater than or equal to the lower limit Trl of the target temperature range (YES in step ST14), it is determined that the heat radiating unit temperature Tr is within the target temperature range and is in an appropriate state, and the operation state is maintained. On the other hand, when the heat radiating unit temperature Tr is less than the lower limit Trl of the target temperature range (NO in step ST14), it is determined that the inverter device 20 has been excessively cooled and condensation can occur. In this case, a control target of the first expansion valve 11A is changed from the degree of superheat SH to the heat radiating unit temperature Tr (step ST15). Then, control is performed so that the opening degree of the first expansion valve 11A is reduced until the heat radiating unit temperature Tr reaches or exceeds the lower limit Trl of the target temperature range (steps ST14 to ST16). Thus, when the heat radiating unit temperature Tr is less than the upper limit Tru of the target temperature range, the control target is switched from the degree of superheat SH to the heat radiating unit temperature Tr, thereby enabling the inverter heat radiating unit 12 to be appropriately cooled so that it is not excessively cooled.

When it is determined that an operation state is such a superheat operation state that the heat radiating unit temperature Tr is above the upper limit Tru of the target temperature range (NO in step ST12), the control target is changed from the degree of superheat SH to the heat radiating unit temperature Tr. Furthermore, the upper limit Tru of the target temperature range is set to a second upper limit Trus (for example, 35 degrees C) less than the initially-set value thereof (step ST21). Then, the valve 11C is opened (step ST22), thereby resulting in the flow of refrigerant through both the subcooling circuit 10A and the bypass cooling circuit 10B. Then, control is performed so that the opening degree of the second expansion valve 11B is increased (step ST23). It is determined whether the heat radiating unit temperature Tr is less than or equal to the second upper limit Trus (step ST24), and the opening degree of the second expansion valve 11B is increased until the heat radiating unit temperature Tr reaches or falls below the second upper limit Trus (steps ST23 and ST24).
On the other hand, when the heat radiating unit temperature Tr reaches or falls below the second upper limit Trus (YES in step ST24), it is determined whether the heat radiating unit temperature Tr is greater than or equal to the lower limit Trl of the target temperature range (step ST25). When it is determined that the heat radiating unit temperature Tr is less than the lower limit Trl of the target temperature range (NO in step ST25), the inverter heat radiating unit 12 has been excessively cooled, and the opening degree of the second expansion valve 11B is thus reduced (steps ST25 and ST29).
When the heat radiating unit temperature Tr is greater than or equal to the lower limit Trl of the target temperature range (YES in steps ST25), the opening degree of the second expansion valve 11B is maintained (step ST26). At this time, it is determined whether the opening degree of the second expansion valve 11B is a minimum opening degree (step ST27). When the opening degree of the second expansion valve 11B is not the minimum opening degree, the opening degree of the second expansion valve 11B is regulated as described above (step ST25 to step ST27). When the opening degree of the electronic expansion valve reaches the minimum opening degree (YES in step ST27), it is determined that a state has been entered in which the heat radiating unit temperature Tr does not exceed the upper limit Tru of the target temperature range even when the valve 11C is closed so that refrigerant does not flow to the bypass cooling circuit 10B side, and the valve 11C is closed (step ST28). The above-described processes of step ST21 to step ST29 are implemented at control time intervals. Although the case where the opening degree of the second expansion valve 11B is regulated in the superheat operation state is illustrated, not only the opening degree of the second expansion valve 11B but also an opening degree of the first expansion valve 11A may be regulated.
According to Embodiment 1 described above, when the heat radiating unit temperature Tr is within the target temperature range, an opening degree of the flow rate regulation device 11 is controlled based on the degree of superheat SH, and, when the heat radiating unit temperature Tr is outside the target temperature range, an opening degree of the flow rate regulation device 11 is controlled based on the heat radiating unit temperature Tr. This can control a reduction in capacity due to insufficiency in effective use of the economizer 5 and also prevent condensation from occurring during cooling the inverter device 20. Furthermore, the use of refrigerant that is to flow to the intermediate-pressure space for cooling the inverter heat radiating unit 12 can prevent refrigerant having cooled the inverter device 20 from adversely affecting suction gas and enhance performance.
In the steady operation state, when the inverter heat radiating unit 12 is cooled by using refrigerant gas having passed through the economizer 5 that is to flow into the intermediate-pressure space, the difference in temperature between outdoor air and the inverter heat radiating unit 12 is reduced, thereby making it possible to prevent the occurrence of condensation. In the superheat operation state, when the temperature of the inverter heat radiating unit 12 is controlled to be close to the upper limit Tru of the target temperature range, the inverter heat radiating unit 12 is cooled without being subcooled, and the difference in temperature between outdoor air and the inverter heat radiating unit 12 is reduced, thereby making it possible to prevent the occurrence of condensation.
Furthermore, in the case of such a superheat operation state that the heat radiating unit temperature Tr is above the upper limit Tru of the target temperature range, the inverter heat radiating unit 12 is further cooled by using liquid refrigerant on the bypass cooling circuit 10B side, thereby enabling the heat radiating unit temperature Tr to be less than or equal to the upper limit Tru of the target temperature range and be close to the upper limit Tru of the target temperature range. Thus, excessive cooling of the inverter heat radiating unit 12 is prevented, and the difference in temperature between the inverter heat radiating unit 12 and outdoor air is reduced, thereby making it possible to prevent the occurrence of condensation.
Even when the heat radiating unit temperature Tr falls below the lower limit Trl of the target temperature range and an excessive cooling state is entered, control based on the degree of superheat SH is switched to control based on the heat radiating unit temperature Tr, thereby making it possible to avoid a state in which condensation is likely to occur.
Furthermore, when the inverter cooling circuit 10 includes not only the subcooling circuit 10A but also the bypass cooling circuit 10B, the heat radiating unit temperature Tr can be reduced to a temperature within the target temperature range earlier in the superheat operation state.

Embodiment 2

Fig. 4 is a refrigerant circuit diagram illustrating a refrigeration apparatus according to Embodiment 2 of the present invention. A refrigeration apparatus 100 will be described with reference to Fig. 4. In the refrigeration apparatus 100 of Fig. 4, components that have the same configurations as those in the refrigeration apparatus 1 of Fig. 1 are denoted by the same reference numerals, and description thereof is omitted. The refrigeration apparatus 100 of Fig. 4 differs from the refrigeration apparatus 1 of Fig. 1 in the position where a refrigerant temperature detection device 132a is installed.
In the refrigeration apparatus 100 of Fig. 3, the refrigerant temperature detection device 132a is installed in a position where a temperature of refrigerant having flowed out of the inverter heat radiating unit 12 is detected. The outflow temperature sensor is provided in a position in front of the junction with the bypass cooling circuit 10B. Then, the superheat degree calculation unit 42 calculates a degree of superheat SH of refrigerant gas by using a refrigerant temperature detected by the refrigerant temperature detection device 132a. The opening degree control unit 43 controls the first expansion valve 11A so that the degree of superheat SH reaches the target degree of superheat during steady operation.
According to Embodiment 2, as in Embodiment 1, a reduction in capacity due to insufficiency in effective use of the economizer 5 can be controlled, and condensation can also be prevented from occurring during cooling the inverter device 20. Furthermore, the first expansion valve 11A is controlled based on a temperature of refrigerant having cooled the inverter heat radiating unit 12, and an operable range in control during steady operation can thus be expanded further. Additionally, the amount of refrigerant injected in liquid form during superheat operation is reduced, and a reduction in performance in the superheat operation state can thus be suppressed.

Embodiment 3

Fig. 5 is a refrigerant circuit diagram illustrating a refrigeration apparatus according to Embodiment 3 of the present invention. A refrigeration apparatus 200 will be described with reference to Fig. 5. In the refrigeration apparatus 200 of Fig. 5, components that have the same configurations as those in the refrigeration apparatus 1 of Fig. 1 are denoted by the same reference numerals, and description thereof is omitted. The refrigeration apparatus 200 of Fig. 5 differs from the refrigeration apparatus 1 of Fig. 1 in the configuration of the inverter cooling circuit.
An inverter cooling circuit 210 of Fig. 5 is constituted by the subcooling circuit 10A without the bypass cooling circuit 10B. Thus, the opening degree control unit 43 of the controller 40 controls the opening degree of the first expansion valve 11A serving as the flow rate regulation device 11.
Fig. 6 is a flowchart illustrating an example of the control of the refrigeration apparatus according to Embodiment 1 of the present invention. Processes illustrated in the flowchart of Fig. 6 are implemented at certain set control time intervals. In the flowchart of Fig. 6, steps that are the same as those in the flowchart of Fig. 3 are denoted by the same reference numerals, and description thereof is omitted. In the steady operation state, the same control is performed except that step ST13 is not included. As control in the superheat operation state, steps ST31 to ST37 will be described below.

In the opening degree control unit 43 of the controller 40, the control target of the first expansion valve 11A is changed from the degree of superheat SH to the heat radiating unit temperature Tr (step ST31). The heat radiating unit temperature Tr is higher than the upper limit Tru of the target temperature range, and control is thus performed so that the opening degree of the first expansion valve 11A is increased (step ST32). Subsequently, it is determined whether the heat radiating unit temperature Tr is less than or equal to the upper limit Tru of the target temperature range (step ST33). When it is determined that the heat radiating unit temperature Tr is above the upper limit Tru of the target temperature range (NO in step ST33), the inverter heat radiating unit 12 is in an insufficient cooling state, and control is thus performed so that the opening degree of the first expansion valve 11A is increased until the heat radiating unit temperature Tr reaches or falls below the upper limit Tru of the target temperature range (steps ST32 and ST33).
On the other hand, when it is determined that the heat radiating unit temperature Tr is less than or equal to the upper limit Tru of the target temperature range (YES in step ST33), it is determined whether the heat radiating unit temperature Tr is greater than or equal to the lower limit Trl of the target temperature range (step ST34). When it is determined that the heat radiating unit temperature Tr is less than the lower limit Trl of the target temperature range (NO in step ST34), the inverter heat radiating unit 12 has been excessively cooled, and control is thus performed so that the opening degree of the first expansion valve 11A becomes smaller than the current opening degree (step ST37). Then, control is performed so that the opening degree of the first expansion valve 11A is reduced until the heat radiating unit temperature Tr reaches or exceeds the lower limit Trl of the target temperature range (steps ST34 and ST37).
On the other hand, when the heat radiating unit temperature Tr is greater than or equal to the lower limit Trl of the target temperature range (YES in step ST34), it is determined whether the degree of superheat SH is greater than the target degree of superheat in the steady operation state to determine whether to perform control in the steady operation state (step ST35). When the degree of superheat SH is greater than the target degree of superheat (YES in step ST35), it is determined that the economizer 5 has not been used effectively, and the control target of the first expansion valve 11A is thus changed from the heat radiating unit temperature Tr to the degree of superheat SH in the steady operation state (step ST36). On the other hand, when the degree of superheat SH is less than the control target degree of superheat, control based on the heat radiating unit temperature Tr is continued (steps ST33 to ST35).
According to Embodiment 3, as in Embodiment 1, in the superheat operation state, that is, in the case where the temperature of the inverter heat radiating unit 12 is above the upper limit Tru of the target temperature range, the control target of the first expansion valve 11A is changed, thereby enabling the temperature of the inverter heat radiating unit 12 to be less than or equal to the upper limit Tru of the target temperature range but be close to the upper limit Tru of the target temperature range. Thus, excessive cooling of the inverter heat radiating unit 12 is prevented, and the difference in temperature between the inverter heat radiating unit 12 and outdoor air can be reduced. Furthermore, there is no cooling circuit using liquid injection, thus enabling simplification of the refrigerant circuit and control.

Reference Signs List

1, 100, 200 refrigeration apparatus 1A refrigerant circuit 2 compressor 2a mechanism unit 3 oil separator 4 condenser 5 economizer 6 expansion device 7 evaporator 10, 210 inverter cooling circuit 10A subcooling circuit 10B bypass cooling circuit 11 flow rate regulation device 11A first expansion valve 11B second expansion valve 11C on-off valve 12 inverter heat radiating unit 20 inverter device 31 heat radiating unit temperature detection device 32a, 132a refrigerant temperature detection device 32b intermediate-pressure detection device 33 suction temperature detection device 34 suction pressure detection device 40 controller 41 temperature determination unit 42 superheat degree calculation unit 43 opening degree control unit SH degree of superheat Tr heat radiating unit temperature Trl lower limit Tru upper limit Trus second upper limit

Claims

A refrigeration apparatus comprising:
a refrigerant circuit in which a compressor configured to compress refrigerant, a condenser configured to cause the refrigerant discharged from the compressor to reject heat and cool, an economizer configured to subcool the refrigerant having flowed out of the condenser, an expansion device configured to reduce pressure of and expand the refrigerant subcooled in the economizer, and an evaporator configured to cause the refrigerant reduced in pressure and expanded in the expansion device to receive heat and evaporate, are connected by a refrigerant pipe;

an inverter device configured to drive the compressor;

an inverter heat radiating unit configured to reject heat generated in the inverter device;

an inverter cooling circuit including a subcooling circuit in which a refrigerant flow passage is formed that branches off from between the economizer and the expansion device, extends through the economizer and the inverter heat radiating unit, and then extends into the compressor;

a flow rate regulation device provided in the inverter cooling circuit and configured to regulate a flow rate of refrigerant that is to flow into the inverter heat radiating unit;

an inverter temperature detection device configured to detect a temperature of the inverter heat radiating unit as a heat radiating unit temperature;

a state detection unit configured to detect a state of refrigerant flowing through the economizer; and

a controller configured to, based on the heat radiating unit temperature detected in the inverter temperature detection device and the state of refrigerant flowing through the economizer detected by the state detection unit, control action of the flow rate regulation device,

wherein the controller includes

a temperature determination unit configured to determine whether the heat radiating unit temperature is within a target temperature range,

a superheat degree calculation unit configured to calculate a degree of superheat of refrigerant flowing through the economizer from the state of refrigerant detected in the state detection unit, and

an opening degree control unit configured to, when the temperature determination unit determines that the heat radiating unit temperature is within the target temperature range, control an opening degree of the flow rate regulation device so that the degree of superheat calculated in the superheat degree calculation unit reaches a target degree of superheat, and configured to, when the temperature determination unit determines that the heat radiating unit temperature is outside the target temperature range, control the opening degree of the flow rate regulation device so that the heat radiating unit temperature falls within the target temperature range.
The refrigeration apparatus of claim 1, wherein the state detection unit includes an intermediate-pressure detection device configured to detect an intermediate pressure in the compressor, and a refrigerant temperature detection device configured to detect a temperature of refrigerant that is to flow into the inverter heat radiating unit.
The refrigeration apparatus of claim 1, wherein the state detection unit includes an intermediate-pressure detection device configured to detect an intermediate pressure, and a refrigerant temperature detection device configured to detect a temperature of refrigerant having flowed out of the inverter heat radiating unit.
The refrigeration apparatus of any one of claims 1 to 3, wherein, the controller is configured to reduce, when it is determined that the heat radiating unit temperature is less than a lower limit of the target temperature range, an opening degree of the flow rate regulation device.
The refrigeration apparatus of any one of claims 1 to 4, wherein, when it is determined that the heat radiating unit temperature is greater than an upper limit of the target temperature range, the opening degree control unit increases an opening degree of the flow rate regulation device.
The refrigeration apparatus of claim 5, wherein, after the opening degree control unit increases the opening degree of the flow rate regulation device, when the heat radiating unit temperature is less than the upper limit of the target temperature range and the degree of superheat is greater than the target degree of superheat, the opening degree control unit changes a control target from the heat radiating unit temperature to the degree of superheat.
The refrigeration apparatus of any one of claims 1 to 5, wherein
the inverter cooling circuit includes a bypass cooling circuit branching off from between the economizer and the expansion device and connected to the compressor through the economizer,
the flow rate regulation device includes a bypass flow rate regulation device provided to the bypass cooling circuit and configured to regulate a flow rate of refrigerant that flows through the bypass cooling circuit, and
the opening degree control unit is configured to perform, when the heat radiating unit temperature is greater than an upper limit of the target temperature range, control to put the bypass flow rate regulation device into a fully-closed state, and, when the heat radiating unit temperature is less than or equal to the upper limit of the target temperature range, the opening degree control unit puts the bypass flow rate regulation device into an open state to regulate a flow rate.
The refrigeration apparatus of claim 7, wherein, after the opening degree control unit puts the bypass flow rate regulation device into the open state to regulate the flow rate, when the heat radiating unit temperature is less than the lower limit of the target temperature range, the opening degree control unit puts the bypass flow rate regulation device into a closed state.
The refrigeration apparatus of any one of claims 1 to 8, wherein the inverter device and the inverter heat radiating unit are placed in a casing of the compressor.