Refrigeration machine for transport

Abstract

Refrigeration machine for transport (3) for cooling a cooling chamber (21) provided in a transport machine (100), characterized by: an internal heat exchanger (53) which carries out a heat exchange between air within the cooling chamber (21) and a first refrigerant, a first compressor (51) which compresses the first refrigerant and supplies it to the internal heat exchanger (53), a first inverter (55) driving the first compressor (51), an external heat exchanger (63) which carries out a heat exchange between outside air and a second refrigerant, a second compressor (61) which compresses the second refrigerant and supplies it to the external heat exchanger (63), a second inverter (65) driving the second compressor (61), an intermediate heat exchanger (7) which exchanges heat between the first refrigerant flowing from the first compressor (51) and the second refrigerant flowing from the external heat exchanger (63), and a control section (90) that sends a drive signal to the first inverter (55) and the second inverter (65) based on a temperature difference between the interior of the cooling chamber (21) and the outside air.

Description

Technical area

[0001] The present disclosure relates to a refrigeration machine for transportation. General state of the art

[0002] Transport vehicles such as refrigerated trucks, which transport goods in a cooled state using a refrigeration device, are widely used. For several years, a so-called cascade cycle type has been used as such a refrigeration device (see, for example, US 2020 / 0148038 A1). In a cascade cycle, different refrigerants are used inside and outside a cold storage room. Specifically, the cascade cycle comprises an internal circuit with an internal heat exchanger, an expansion valve, and an internal compressor; an external circuit with an external heat exchanger, an expansion valve, and an external compressor; and an intermediate heat exchanger. The internal and external circuits exchange heat between their respective refrigerants via the intermediate heat exchanger.As an example, carbon dioxide is used as refrigerant in the internal circuit and propane is used as refrigerant in the external circuit.

[0003] The compressor of a refrigeration circuit according to US 2020 / 0041184 A1 comprises a motor driven by power supplied by a motor generator to an inverter, as well as a refrigerant compression unit. A switch can be used to switch between a start / stop operating mode and a continuous operation mode. In the start / stop operating mode, a controller controls the inverter so that the target speed of the compressor is set to a high speed, which is higher than the speed according to the difference between the set temperature and the internal temperature.

[0004] DE 24 15 070 A1 describes a method for controlling the cooling capacity in air conditioning systems with a speed-controlled refrigerant compressor driven by an asynchronous motor or converter motor whose input voltage is continuously controlled by a frequency converter.

[0005] Further refrigeration machines are known from US 2019 / 0101313 A1 and US 2019 / 0009648 A1. Brief description of the inventionTask of the invention

[0006] When a cascade cycle is used in an environment with variable operating conditions, such as a refrigerated truck, the ratio of the refrigerant circulation volumes in the internal circuit and the external circuit is not constant. Therefore, it is desirable to be able to independently control the flow rate of the refrigerant passing through the internal compressor and the external compressor (i.e., the speed of each compressor). However, in current refrigerated trucks, the compressors are directly connected to the engine. Therefore, the speed of the compressors depends on the engine speed, and independent control is not feasible.

[0007] The object of the present disclosure is to solve the above-described problem and to provide a refrigeration machine for transportation with further improved efficiency. Means of solving the task

[0008] To achieve the above-described object, the transportation refrigeration machine of the present disclosure is a transportation refrigeration machine for cooling a cold storage space provided in a transportation machine, and includes an internal heat exchanger that performs heat exchange between air within the cold storage space and a first refrigerant, a first compressor that compresses the first refrigerant and supplies it to the internal heat exchanger, a first inverter that drives the first compressor, an external heat exchanger that performs heat exchange between outside air and a second refrigerant, a second compressor that compresses the second refrigerant and supplies it to the external heat exchanger, a second inverter that drives the second compressor, an intermediate heat exchanger,which performs heat exchange between the first refrigerant flowing from the first compressor and the second refrigerant flowing from the external heat exchanger, and a control section which sends a drive signal to the first inverter and the second inverter based on a temperature difference between the interior of the refrigerating chamber and the outside air. Effect of the invention

[0009] According to the present disclosure, it is possible to provide a refrigeration machine for transportation with further improved efficiency. Short description of the characters Fig. 1 is a side view showing the structure of a transport machine according to a first embodiment of the present disclosure. Fig. 2 is a circuit diagram showing the structure of the transportation refrigeration machine according to the first embodiment of the present disclosure. Fig. 3 is a flowchart showing the operation of a control section according to a second embodiment of the present disclosure. Embodiments of the inventionFirst embodiment

[0010] In the following, with reference to Fig. 1 to 3, a transport machine 100 and a refrigeration machine for transport 3 according to a first embodiment of the present disclosure are described. Structure of the transport machine

[0011] As in Fig. As shown in Figure 1, the transport machine 100 includes a tractor 1 and a trailer 2. The tractor 1 includes a cab 1C, an engine 11, and an alternator 13. The cab 1C provides accommodation for the driver's compartment and the like. The engine 11 is a drive device for providing driving power to the tractor 1 itself and is housed in the lower portion of the cab 1C. Specific examples of the engine 11 include a diesel engine or a hybrid engine.

[0012] An alternator 13 is connected to the output shaft of the motor 11. The alternator 13 generates electrical power by rotating together with the output shaft of the motor 11. The electrical power generated by the alternator 13 is used to drive the transport refrigeration machine 3 described below and to charge a battery 4. Furthermore, the electrical power of the battery 4 can be used to drive the transport refrigeration machine 3.

[0013] The trailer 2 is a vehicle pulled by the tractor 1. The trailer 2 has a refrigerated compartment 21, the transport refrigeration unit 3, and the battery 4. The refrigerated compartment 21 is a space formed inside the trailer 2 and stores goods that require refrigeration / freezing. The transport refrigeration unit 3 is provided to lower the temperature in the refrigerated compartment 21. Construction of the refrigeration machine for transport

[0014] Next, with reference to Fig. 2 the structure of the refrigeration machine for transport 3 is described. As in Fig. As shown in Figure 2, the refrigeration machine for transport 3 comprises an internal circuit 31, an external circuit 32, an intermediate heat exchanger 7 and a control section 90.

[0015] The internal circuit 31 includes internal lines P1, a first compressor 51, a first expansion valve 52, an internal heat exchanger 53, an indoor fan 54, and a first inverter 55. The internal lines P1 include a first line P11, a second line P12, a third line P13, and a fourth line P14. The first line P11 connects the first compressor 51 and the intermediate heat exchanger 7. The second line P12 connects the intermediate heat exchanger 7 and the first expansion valve 52. The third line P13 connects the first expansion valve 52 and the internal heat exchanger 53. The fourth line P14 connects the internal heat exchanger 53 and the first compressor 51. These internal lines P1 are filled with carbon dioxide as the first refrigerant.

[0016] The first compressor 51 compresses low-pressure gaseous refrigerant drawn in from the fourth line P14 and generates high-temperature, high-pressure gaseous refrigerant. This high-temperature, high-pressure gaseous refrigerant flows through the first line P11 into the intermediate heat exchanger 7. The intermediate heat exchanger 7 performs heat exchange between the second refrigerant flowing through the external circuit 32 described below and the first refrigerant. As a result, the gaseous refrigerant in the intermediate heat exchanger 7 is compressed, producing high-pressure liquid refrigerant.

[0017] The high-pressure liquid refrigerant is passed through the second line P12 to the first expansion valve 52. The high-pressure liquid refrigerant loses pressure by passing through the first expansion valve 52 and becomes low-temperature, low-pressure liquid refrigerant.

[0018] The liquid refrigerant, which has become low-temperature, low-pressure refrigerant by passing through the first expansion valve 52, flows through the third pipe P13 into the internal heat exchanger 53. The internal heat exchanger 53 is provided inside the refrigerating chamber 21. In the internal heat exchanger 53, heat exchange occurs between the air in the refrigerating chamber 21 and the first refrigerant. The indoor fan 54 is provided to direct air in the refrigerating chamber 21 to the internal heat exchanger 53. By absorbing the heat in the refrigerating chamber 21 by the low-temperature liquid refrigerant, the temperature in the refrigerating chamber 21 changes toward lowering it. Thus, the interior of the refrigerating chamber 21 is cooled. As a result, the temperature of the liquid refrigerant rises, and it changes from the liquid phase to the gas phase.

[0019] The refrigerant which has entered the gas phase by passing through the internal heat exchanger 53 is sucked back into the first compressor 51 via the fourth line P14.

[0020] The rotational speed of the first compressor 51 is controlled by the first inverter 55. The first inverter 55 converts the electric power supplied by the aforementioned alternator 13 or the battery 4 and generates an electric power optimal for driving the first compressor 51. The operation of the first inverter 55 is controlled by the control section 90 described below.

[0021] The external circuit 32 has external lines P2, a second compressor 61, a second expansion valve 62, an external heat exchanger 63, an external fan 64, and a second inverter 65. The external lines P2 have a first line P21, a second line P22, a third line P23, and a fourth line P24. The first line P21 connects the second compressor 61 and the external heat exchanger 63. The second line P22 connects the external heat exchanger 63 and the second expansion valve 62. The third line P23 connects the second expansion valve 62 and the intermediate heat exchanger 7. The fourth line P24 connects the intermediate heat exchanger 7 and the second compressor 61. These external lines P2 are filled, for example, with propane as the second refrigerant.

[0022] The second compressor 61 compresses low-pressure gaseous refrigerant drawn in from the fourth line P24 and generates high-temperature, high-pressure gaseous refrigerant. This high-temperature, high-pressure gaseous refrigerant flows through the first line P21 into the external heat exchanger 63. The external heat exchanger 63 is provided outside the above-described cold storage space 21. The external heat exchanger 63 performs heat exchange between the outside air and the second refrigerant. The external fan 64 is provided to direct outside air to the external heat exchanger 63. As a result, the gaseous refrigerant in the external heat exchanger 63 is compressed, producing high-pressure liquid refrigerant.

[0023] The high-pressure liquid refrigerant is supplied to the second expansion valve 62 via the second line P22. The high-pressure liquid refrigerant loses pressure as it passes through the second expansion valve 62 and becomes low-temperature, low-pressure liquid refrigerant.

[0024] The liquid refrigerant, which has become low-temperature, low-pressure refrigerant by passing through the second expansion valve 62, flows through the third line P23 into the intermediate heat exchanger 7. The intermediate heat exchanger 7 performs heat exchange between the first refrigerant flowing through the above-described internal circuit 31 and the second refrigerant. Specifically, heat exchange occurs between the high-temperature, high-pressure gas refrigerant (the first refrigerant) flowing through the first line P11 of the internal circuit 31 and the low-temperature, low-pressure liquid refrigerant (the second refrigerant) flowing through the third line P23 of the external circuit 32. As a result, in the external circuit 32, the temperature of the liquid refrigerant flowing in the third line P23 rises, and it changes from the liquid phase to the gas phase.

[0025] The refrigerant, which has entered the gas phase by passing through the intermediate heat exchanger 7, is sucked back into the second compressor 61 via the fourth line P24. By continuously performing such a cycle, the temperature of the cooling chamber 21 is regulated to a desired value.

[0026] The rotational speed of the second compressor 61 is controlled by the second inverter 65. The second inverter 65 converts the electric power supplied by the aforementioned alternator 13 or the battery 4 and generates an optimal electric power for driving the second compressor 61. The operation of the second inverter 65 is controlled by the control section 90 described below.

[0027] The control section 90 sends a drive signal to the first inverter 55 and the second inverter 65 based on the operating state of the transportation refrigeration machine 3. More specifically, the control section 90 sends a drive signal to the first inverter 55 and the second inverter 65 based on a temperature difference between the interior of the refrigerating room 21 and the outside air.

[0028] The control section 90 first determines an optimal range for the speed ratio of the first compressor 51 and the second compressor 61 based on the temperature difference between the refrigerating chamber 21 and the outside air. Then, the control section 90 sends a drive signal to the first inverter 55 and the second inverter 65 to bring the actual speed ratio of the compressors into the optimal range. Mode of action, effect

[0029] According to the above configuration, it is possible to operate the first compressor 51 and the second compressor 61 at their own speeds and maintain their speed ratio within an optimal range. Therefore, for example, when the temperature difference between the refrigerating chamber 21 and the outside air is large, or the like, and a flow rate difference between the first refrigerant and the second refrigerant is required, a speed difference can be established between the first compressor 51 and the second compressor 61, and the optimal operating point can be approached.

[0030] A first embodiment of the present disclosure has been described above. Various changes and modifications can be made to the above configuration as long as the gist of the present disclosure is not deviated from. For example, in the first embodiment, an example of operation was described in which the control section 90 determines an optimal range for the speed ratio of the first compressor 51 and the second compressor 61 and maintains the actual speed ratio within this optimal range. However, it is also possible to adopt a configuration in which the control section 90 sets a specific speed ratio instead of such a numerical range and changes the actual speed ratio to achieve this value. Second embodiment

[0031] In the following, with reference to Fig. 3, a second embodiment of the present disclosure is described. The same reference numerals are used for the same structure as in the first embodiment described above, and a detailed description is omitted. As shown in Fig. 3, in the present embodiment, the control section 90 sends a drive signal to the first inverter 55 and the second inverter 65 so that the first compressor 51 and the second compressor 61 do not reach a mutual resonance speed assigned in advance.

[0032] Specifically, this control flow is executed for each of the first compressor 51 and the second compressor 61. The following is a description of the control flow for the first compressor 51 as an example. This flow includes an operating point setting step S1, a compressor speed setting step S2, a first judgment step S3, a first readjustment step S4, a second judgment step S5, and a second readjustment step S6.

[0033] In the operating point setting step S1, an operating point (i.e., a flow rate of the first refrigerant) of the first compressor 51 is set based on the temperature difference between the outside air and the refrigerating chamber 21 or the like. In the compressor speed setting step S2, the speed of the first compressor 51 is set based on the operating point. Next, in the first judgment step S3, it is judged whether the speed of the first compressor 51 is within the optimal range of the speed ratio to the second compressor 61 described above in the first embodiment. If it is judged in the first judgment step S3 that the speed is not within the optimal range (S3: No), the speed is increased or decreased by a predetermined amount (Δrps) by executing the first readjustment step S4. Then, the first judgment step S3 is executed again.

[0034] If the first judgment step S3 judges that the rotational speed is within the optimum range (S3: Yes), the second judgment step S5 judges whether the rotational speed is identical to a pre-assigned resonance rotational speed. If the second judgment step S5 judges that the rotational speed is identical to the resonance rotational speed (S5: No), the second readjustment step S6 increases or decreases the rotational speed by a predetermined amount (Δrps). Subsequently, the second judgment step S5 is executed again. If the second judgment step S5 judges that the rotational speed is within the optimum range (S5: Yes), the operation of the first compressor 51 continues at the rotational speed at that time.

[0035] According to the above configuration, resonance of the first compressor 51 and the second compressor 61 can be avoided, and the transportation refrigeration machine 3 can be operated more stably. Thus, the operating range of the transportation refrigeration machine 3 can be further expanded.

[0036] A second embodiment of the present disclosure has been described above. Various changes and modifications may be made to the above embodiment without departing from the spirit of the present disclosure. Addendum

[0037] The contents of the refrigeration machine for transportation 3 mentioned in the above embodiments can be captured, for example, as follows.

[0038] (1) A refrigeration machine for transportation 3 according to a first aspect is a refrigeration machine for transportation 3 for cooling a cold storage space 21 provided in a transportation machine 100, and includes an internal heat exchanger 53 that performs heat exchange between air within the cold storage space 21 and a first refrigerant, a first compressor 51 that compresses the first refrigerant and supplies it to the internal heat exchanger 53, a first inverter 55 that drives the first compressor 51, an external heat exchanger 63 that performs heat exchange between outside air and a second refrigerant, a second compressor 61 that compresses the second refrigerant and supplies it to the external heat exchanger 63, a second inverter 65 that drives the second compressor 61, an intermediate heat exchanger 7,which performs heat exchange between the first refrigerant flowing from the first compressor 51 and the second refrigerant flowing from the external heat exchanger 63, and a control section 90 which sends a drive signal to the first inverter 55 and the second inverter 65 based on a temperature difference between the interior of the refrigerating chamber 21 and the outside air.

[0039] According to the above configuration, the first compressor 51 and the second compressor 61 can be operated independently of each other by the first inverter 55 and the second inverter 65. Therefore, for example, when the temperature difference between the refrigerating chamber 21 and the outside air is large, or the like, and a flow difference between the first refrigerant and the second refrigerant is required, a speed difference between the first compressor 51 and the second compressor 61 can be achieved, and the optimal operating point can be approached.

[0040] (2) In a refrigeration machine for transportation 3 according to a second aspect, the control section 90 sets an optimal range for a speed ratio of the first compressor 51 and the second compressor 61 based on a temperature difference between the inside of the refrigerating room 21 and the outside air, and sends a drive signal to the first inverter 55 and the second inverter 65, which causes the speed ratio to be brought into the optimal range.

[0041] According to the above configuration, when the temperature difference between the refrigerating chamber 21 and the outside air is large or the like and a flow difference for the first refrigerant and the second refrigerant is required, a speed difference of the first compressor 51 and the second compressor 61 can be induced and the optimum operating point can be approached.

[0042] (3) In a refrigeration machine for transportation 3 according to a third aspect, the control section 90 sets an optimal speed ratio of the first compressor 51 and the second compressor 61 based on a temperature difference between the inside of the refrigerating chamber 21 and the outside air, and sends a drive signal to the first inverter 55 and the second inverter 65, causing the speeds to be brought to the optimal ratio.

[0043] According to the above configuration, when the temperature difference between the refrigerating chamber 21 and the outside air is large or the like and a flow difference for the first refrigerant and the second refrigerant is required, a speed difference of the first compressor 51 and the second compressor 61 can be induced and the optimum operating point can be approached.

[0044] (4) In a refrigeration machine for transportation 3 according to a fourth aspect, the control section 90 sends a drive signal to the first inverter 55 and the second inverter 65 so that the first compressor 51 and the second compressor 61 do not reach a mutual resonance speed assigned in advance.

[0045] According to the above configuration, resonance of the first compressor 51 and the second compressor 61 can be avoided and the refrigeration machine for transportation 3 can be operated more stably. Description of reference symbols 100 transport machines 1 tractor 1C cab 2 trailers 3 Refrigeration machine for transport 4 Battery 7 intermediate heat exchangers 11 Engine 13 Alternating current machine 21 Cold room 31 internal circuit 32 external circuit 51 first compressor 52 first expansion valve 53 internal heat exchanger 54 Interior fan 55 first inverter 61 second compressor 62 second expansion valve 63 external heat exchanger 64 outdoor fan 65 second inverter 90 tax section P1 internal lines P2 external lines P11, P21 first line P12, P22 second line P13, P23 third line P14, P24 fourth line

Claims

[1] Refrigeration machine for transport (3) for cooling a cooling chamber (21) provided in a transport machine (100), characterized by : an internal heat exchanger (53) which carries out a heat exchange between air within the cooling chamber (21) and a first refrigerant, a first compressor (51) which compresses the first refrigerant and supplies it to the internal heat exchanger (53), a first inverter (55) driving the first compressor (51), an external heat exchanger (63) which carries out a heat exchange between outside air and a second refrigerant, a second compressor (61) which compresses the second refrigerant and supplies it to the external heat exchanger (63), a second inverter (65) driving the second compressor (61), an intermediate heat exchanger (7) which exchanges heat between the first refrigerant flowing from the first compressor (51) and the second refrigerant flowing from the external heat exchanger (63), and a control section (90) that sends a drive signal to the first inverter (55) and the second inverter (65) based on a temperature difference between the interior of the cooling chamber (21) and the outside air. [2] The transportation refrigeration machine (3) according to claim 1, wherein the control section (90) sets an optimal range for a speed ratio of the first compressor (51) and the second compressor (61) based on a temperature difference between the inside of the refrigerating chamber (21) and the outside air, and sends a drive signal to the first inverter (55) and the second inverter (65) that causes the speed ratio to be brought into the optimal range. [3] The transportation refrigeration machine (3) according to claim 1, wherein the control section (90) sets an optimal speed ratio of the first compressor (51) and the second compressor (61) based on a temperature difference between the inside of the refrigerating chamber (21) and the outside air, and sends a drive signal to the first inverter (55) and the second inverter (65) that causes the speeds to be brought to the optimal ratio. [4] The transportation refrigeration machine (3) according to any one of claims 1 to 3, wherein the control section (90) sends a drive signal to the first inverter (55) and the second inverter (65) so that the first compressor (51) and the second compressor (61) do not reach a mutual resonance speed assigned in advance.

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