Refrigeration cycle device

Abstract

To provide a refrigeration cycle device for suppressing an excessive rise in the temperature of a compressor and an excessive increase in the rotating speed of a motor of a compressor when operating the compressor in an inefficient drive mode.SOLUTION: The refrigeration cycle device includes a refrigeration cycle where the compressor, a condenser, a first expansion valve, and a vaporizer are sequentially provided in a first flow path for refrigerant to flow therein, a bypass system where a second expansion valve is provided in a second flow path which is branched from between the compressor and the condenser in the first flow path and joined between the compressor and the vaporizer in the first flow path, and a control device. When a heating demand for the compressor is performed, the control device controls the motor so that a d-axis current in the motor is greater and controls the second expansion valve so that the flow amount of the refrigerant in the second flow path is larger, than when the heating demand for the compressor is not performed.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a refrigeration cycle device. [Background technology]

[0002] Conventionally, as this type of technology, a heat exchange system has been proposed that is applied to a vehicle that uses an electric motor driven by power supplied from a battery as a driving power source, and that includes an air-conditioning heat pump that includes a compressor that is driven by the battery power to compress a refrigerant (see, for example, Patent Document 1). This heat exchange system includes a heat exchange unit that exchanges heat between the refrigerant and lubricating oil that lubricates the power transmission device mounted on the vehicle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-51872 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned heat exchange system, in order to heat the object to be heated more sufficiently by increasing the heat generation amount of the compressor, it is considered to drive the compressor in an inefficient drive mode. In this case, if the flow rate of the refrigerant flowing through the compressor is small, there is a concern that the temperature of the compressor may rise too high or the rotation speed of the compressor motor may rise too high.

[0005] The refrigeration cycle device of the present disclosure has a primary objective to suppress the occurrence of an excessive increase in compressor temperature, an excessive increase in the rotation speed of the compressor motor, etc., when the compressor is driven in an inefficient drive mode. [Means for solving the problem]

[0006] The refrigeration cycle device of the present disclosure employs the following means to achieve the above-mentioned main object. The refrigeration cycle device of the present disclosure includes a refrigeration cycle in which a compressor, a condenser, a first expansion valve, and an evaporator are provided in this order in a first flow path through which a refrigerant flows, a bypass system in which a second expansion valve is provided in a second flow path that branches off from between the compressor and the condenser in the first flow path and joins the first flow path between the compressor and the evaporator, and a control device, wherein the control device controls the motor so that a d-axis current of the motor is larger and controls the second expansion valve so that a flow rate of the refrigerant in the second flow path is larger when a heat generation request is made by the compressor, compared to when a heat generation request is not made by the compressor.

[0007] In the refrigeration cycle device of the present disclosure, when a request for heat generation from the compressor is made, the motor is controlled so that the d-axis current of the motor is larger (the motor is driven in an inefficient drive mode) and the second expansion valve is controlled so that the flow rate of the refrigerant in the second flow path is increased, compared to when a request for heat generation from the compressor is not made. This makes it possible to increase the amount of heat generated by the compressor and to increase the flow rate of the refrigerant flowing through the compressor, thereby suppressing the occurrence of an excessive rise in the temperature of the compressor and an excessive rise in the rotation speed of the motor of the compressor. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic configuration diagram of a refrigeration cycle device 10 according to an embodiment of the present disclosure. [Diagram 2] 2 is an explanatory diagram showing an example of the relationship between specific enthalpy and pressure in the refrigeration cycle device 10. FIG. [Diagram 3] 10 is a flowchart illustrating an example of a processing routine. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] An embodiment of the present disclosure will be described with reference to the drawings. Fig. 1 is a schematic configuration diagram of a refrigeration cycle device 10 according to an embodiment of the present disclosure. The refrigeration cycle device 10 according to the embodiment is mounted, for example, in an electric vehicle (electric vehicle, hybrid vehicle, or fuel cell vehicle) equipped with a battery that exchanges power with a driving motor, and is used to cool or heat the battery. As shown in the figure, the refrigeration cycle device 10 includes a refrigeration cycle 20, a bypass system 40, and an electronic control unit (hereinafter referred to as "ECU") 50.

[0010] The refrigeration cycle 20 has a first flow path 22, a compressor 24, a condenser 28, a first expansion valve 30, and an evaporator 32. The first flow path 22 is a flow path through which a refrigerant flows, and the compressor 24, the condenser 28, the first expansion valve 30, and the evaporator 32 are provided in this order in the first flow path 22. The compressor 24 has a compression section 25, a motor 26, and an inverter 27. The compression section 25 compresses the low-temperature, low-pressure gas refrigerant from the evaporator 32 by the operation of the motor 26 driven by the inverter 27, turns it into a high-temperature, high-pressure gas refrigerant, and pressure-feeds it. The motor 26 is configured as a three-phase AC motor. The inverter converts DC power from a battery into three-phase AC power and supplies it to the motor to rotate and drive the motor. The condenser 28 turns the high-temperature, high-pressure gas refrigerant from the compressor 24 into a normal-temperature, high-pressure liquid refrigerant. The first expansion valve 30 expands the normal temperature, high pressure liquid refrigerant from the condenser 28 to produce a low temperature, low pressure gas-liquid mixed refrigerant. The evaporator 32 produces a low temperature, low pressure gas-liquid mixed refrigerant from the first expansion valve 30 to produce a low temperature, low pressure gas refrigerant. In the embodiment, a cooling device that circulates coolant between the battery and a selected one of the evaporator 32 and the condenser 28 by an electric pump is used, and the coolant cooled by heat exchange with the evaporator 32 or the coolant heated by heat exchange with the condenser 28 is selectively supplied to the battery side to cool or heat the battery.

[0011] The bypass system 40 has a second flow path 42 and a second expansion valve 44. The second flow path 42 branches off from the first flow path 22 at a position P1 between the compressor 24 and the condenser 28 of the first flow path 22, and merges with the first flow path 22 at a position P2 between the compressor 24 and the evaporator 32 of the first flow path 22. When the second expansion valve 44 is open, it expands the high-temperature, high-pressure gaseous refrigerant from the compressor 24 to produce a low-temperature, low-pressure gaseous refrigerant.

[0012] FIG. 2 is an explanatory diagram showing an example of the relationship between the specific enthalpy and the pressure in the refrigeration cycle device 10. FIG. 2(a) shows an example of the relationship when the second expansion valve 44 is closed, and FIG. 2(b) shows an example of the relationship when the second expansion valve 44 is open. In FIG. 2(a) and FIG. 2(b), the solid arrows indicate the flow of the refrigerant in the refrigeration cycle 20, and the dashed arrows indicate the flow of the refrigerant in the bypass system 40. In addition, (1) indicates the change when flowing through the compressor 24, (2) indicates the change when flowing through the condenser 28, (3) indicates the change when flowing through the first expansion valve 30, (4) indicates the change when flowing through the evaporator 32, and (5) indicates the change when flowing through the second expansion valve 44.

[0013] The ECU 50 includes a microcomputer having a CPU, a ROM, a RAM, a flash memory, and an input / output port. The ECU 50 receives the temperature Tin and pressure Pin from the temperature sensor 34 and pressure sensor attached near the inlet of the compressor 24 in the first flow path 22, and the temperature Tout and pressure Pout from the temperature sensor 36 and pressure sensor attached near the outlet of the compressor 24 in the first flow path 22. The ECU 50 also receives the rotational position θm of the rotor of the motor 26 from a rotational position sensor (e.g., a resolver) and the phase currents Iu, Iv, and Iw flowing through each phase of the motor 26 from a current sensor. The battery temperature Tb is also input. The ECU 50 outputs a control signal to the inverter 27, a control signal to the first expansion valve 30, and a control signal to the second expansion valve 44. The ECU 50 calculates the electrical angle θe and the rotation speed Nm of the motor 26 based on the rotational position θm of the rotor of the motor 26.

[0014] Next, the operation of the refrigeration cycle device 10 of the embodiment will be described. Fig. 2 is a flowchart showing an example of a processing routine executed by the ECU 50. This routine is repeatedly executed when a request to heat or cool the battery is made. In the embodiment, it is determined that a request to heat the battery is made when the battery temperature Tb is lower than a threshold value Tblo, and that a request to cool the battery is made when the battery temperature Tb is higher than a threshold value Tbhi that is higher than the threshold value Tblo.

[0015] 2, the ECU 50 first determines whether or not a heat generation request for the compressor 24 has been made (step S100). In the embodiment, when a cooling request for the battery has been made, it is determined that a heat generation request for the compressor 24 has not been made, and when a heating request for the battery has been made, it is determined that a heat generation request for the compressor 24 has been made.

[0016] When it is determined in step S100 that a heat generation request for the compressor 24 has not been made, the inverter 27 is controlled so that the motor 26 is driven in the efficient drive mode (step S110), the second expansion valve 44 is closed or kept closed (step S120), and this routine is terminated. On the other hand, when it is determined in step S100 that a heat generation request for the compressor 24 has been made, the inverter 27 is controlled so that the motor 26 is driven in the inefficient drive mode (step S130), the second expansion valve 44 is opened or kept open (step S140), and this routine is terminated.

[0017] The inverter 27 is controlled by the ECU 50 through pulse width modulation (PWM) control. In the PWM control, the ECU 50 first sets d-axis and q-axis current commands Id* and Iq* based on the torque command Tm* of the motor 26. Then, the ECU 50 performs coordinate conversion (three-phase to two-phase conversion) of the phase currents Iu, Iv, and Iw of each phase to the d-axis and q-axis currents Id and Iq using the electrical angle θe of the motor 26. Then, the ECU 50 sets the d-axis and q-axis voltage commands Vd* and Vq* through current feedback control for canceling the difference between the d-axis and q-axis current commands Id* and Iq* and the currents Id and Iq. Furthermore, the ECU 50 performs coordinate conversion (two-phase to three-phase conversion) of the d-axis and q-axis voltage commands Vd* and Vq* to the voltage commands Vu*, Vv*, and Vw* of each phase. In addition, PWM signals for multiple switching elements of inverter 27 are generated by comparing the voltage commands Vu*, Vv*, Vw* of each phase with a carrier wave (triangular wave), and the switching of the multiple switching elements is controlled using the generated PWM signals.

[0018] Here, the torque command Tm* of the motor 26 is set, for example, so that it increases as the required refrigerant pumping amount Qw* of the compressor 24 increases. For example, when the battery temperature Tb is lower than a threshold value Tblo, the required refrigerant pumping amount Qw* is set so that it increases as the battery temperature Tb decreases, and when the battery temperature Tb is higher than a threshold value Tbhi, the required refrigerant pumping amount Qw* is set so that it increases as the battery temperature Tb increases. Note that the torque command Tm* may be set to a constant value.

[0019] The d-axis and q-axis current commands Id*, Iq* when driving the motor 26 in the efficient drive mode can be set, for example, by applying the torque command Tm* of the motor 26 to an efficient drive map that is predetermined by experiment, analysis, machine learning, etc. as the relationship between the torque command Tm* of the motor 26 and the d-axis and q-axis current commands Id*, Iq* for efficiently driving the motor 26, and deriving the d-axis and q-axis current commands Id*, Iq*.

[0020] When there is no request for the compressor 24 to generate heat, the motor 26 is driven in the efficient drive mode, thereby improving energy efficiency. Furthermore, by closing the second expansion valve 44, the refrigerant does not circulate in the bypass system 40, but circulates only in the refrigeration cycle 20. This allows the refrigeration cycle 20 to function more satisfactorily compared to when the second expansion valve 44 is open. As a result, the battery can be cooled more satisfactorily when the coolant cooled by heat exchange with the evaporator 32 is supplied to the battery side.

[0021] The d-axis and q-axis current commands Id*, Iq* when the motor 26 is in the inefficient drive mode can be set by applying the torque command Tm* of the motor 26 to an inefficient drive map that is determined in advance by experiment, analysis, machine learning, etc. as a relationship between the torque command Tm* of the motor 26 and the d-axis and q-axis current commands Id*, Iq* to reduce the efficiency of the motor 26 (increase the amount of heat generated (heat loss) of the motor 26, the inverter 27, and ultimately the compressor 24) compared to when the motor 26 is driven in the efficient drive mode, to derive the d-axis and q-axis current commands Id*, Iq*. The inefficient drive map is set so that the absolute value of the d-axis current command Id* is larger than that of the efficient drive map.

[0022] When a heat generation request for the compressor 24 is made, the motor 26 is driven in the inefficient drive mode, so that the amount of heat generated by the motor 26, the inverter 27, and the compressor 24 can be increased compared to when the motor 26 is driven in the efficient drive mode. This allows the battery to be heated more sufficiently when the cooling water heated by heat exchange with the condenser 28 is supplied to the battery. At this time, the second expansion valve 44 is opened and the refrigerant is circulated not only through the refrigeration cycle 20 but also through the bypass system 40, so that the flow rate of the refrigerant flowing through the compressor 24 can be increased. This is because, in the refrigeration cycle 20, the refrigerant needs to pass through the condenser 28, the first expansion valve 30, and the evaporator 32 from when it flows out of the compressor 24 until it then flows into the compressor 24, so that the path is long, whereas in the bypass system 40, the refrigerant only passes through the second expansion valve 44, so that the path is short. By increasing the flow rate of the refrigerant flowing through the compressor 24, it is possible to suppress an excessive rise in the temperature of the compressor 24 and an excessive rise in the rotation speed of the motor 26. That is, the battery can be warmed more sufficiently while providing thermal protection for the motor 26 and the inverter 27. If too much refrigerant flows through the second flow path 42 of the bypass system 40, the amount of heat dissipated (heat exchanged) in the condenser 28 of the refrigeration cycle 20 decreases, and the refrigerant tends to become hot. Therefore, it is preferable to set an upper limit on the opening degree of the second expansion valve 44.

[0023] In the refrigeration cycle device 10 of the present embodiment described above, when a heat generation request is made to the compressor 24, the absolute value of the d-axis current command Id* of the motor 26 is made larger than when a heat generation request is not made to the compressor 24, so that the motor 26 is driven in the inefficient drive mode and the second expansion valve 44 is opened. This makes it possible to increase the amount of heat generated by the motor 26, the inverter 27, and ultimately the compressor 24, and also to prevent an excessive rise in the temperature of the compressor 24 and an excessive rise in the rotation speed of the motor 26.

[0024] In the above-described embodiment, when a request for heat generation from the compressor 24 is made (when a request for heating the battery is made), the absolute value of the d-axis current command Id* of the motor 26 is made larger than when a request for heat generation from the compressor 24 is not made, but the degree of this may be constant or may be set based on the degree of the request for heating the battery (the difference between the battery temperature Tb and the threshold value Tbhi).

[0025] In the above-described embodiment, when a request to generate heat from the compressor 24 is made, the second expansion valve 44 is opened or kept open. In this case, the opening degree of the second expansion valve 44 may be constant or may be set based on the degree of the request to heat the battery.

[0026] In the above-described embodiment, the second expansion valve 44 is closed when there is no request for the compressor 24 to generate heat, and is opened when there is a request for the compressor 24 to generate heat. However, this is not limited to this, and it is sufficient that the opening degree of the second expansion valve 44 is increased (the flow rate of the refrigerant in the second flow path 42 is increased) when there is a request for the compressor 24 to generate heat compared to when there is no request for the compressor 24 to generate heat.

[0027] In the above-described embodiment, the battery is cooled or heated by selectively supplying to the battery cooling water cooled by heat exchange with the evaporator 32 or cooling water heated by heat exchange with the condenser 28. However, the battery may be cooled or heated by selectively blowing to the battery air cooled by heat exchange with the evaporator 32 or air heated by heat exchange with the condenser 28.

[0028] In the above-described embodiment, the refrigeration cycle device 10 is mounted on an electric vehicle (electric vehicle, hybrid vehicle, or fuel cell vehicle) equipped with a battery and used to cool or heat the battery, but is not limited thereto. For example, the refrigeration cycle device 10 may be mounted on a vehicle and used as an air conditioner for conditioning the interior of the vehicle. In this case, when a request for cooling the interior of the vehicle is made, it may be determined that a request for heat generation from the compressor 24 is not made, the inverter 27 is controlled so that the motor 26 is driven in the efficient drive mode, the second expansion valve 44 is closed or kept closed, and air cooled by heat exchange with the evaporator 32 may be blown into the vehicle interior. Also, when a request for heating the interior of the vehicle is made, it may be determined that a request for heat generation from the compressor 24 is made, the inverter 27 is controlled so that the motor 26 is driven in the inefficient drive mode, the second expansion valve 44 is opened or kept open, and air heated by heat exchange with the condenser 28 may be blown into the vehicle interior.

[0029] The correspondence between the main elements of the embodiment and the main elements of the invention described in the section on Means for Solving the Problems will be described below. In the embodiment, the refrigeration cycle 20 corresponds to the "refrigeration cycle", the bypass system 40 corresponds to the "bypass system", and the ECU 50 corresponds to the "control device".

[0030] Note that the correspondence between the main elements of the embodiment and the main elements of the invention described in the Means for Solving the Problem column does not limit the elements of the invention described in the Means for Solving the Problem column, since the embodiment is an example for specifically explaining the form for implementing the invention described in the Means for Solving the Problem column. In other words, the interpretation of the invention described in the Means for Solving the Problem column should be made based on the description in that column, and the embodiment is merely a specific example of the invention described in the Means for Solving the Problem column.

[0031] The above describes embodiments for implementing the present disclosure, but the present disclosure is not limited to these embodiments, and it goes without saying that the present disclosure can be implemented in various forms without departing from the gist of the present disclosure. [Industrial Applicability]

[0032] The present disclosure can be used in the refrigeration cycle device manufacturing industry and the like. [Explanation of symbols]

[0033] 10 refrigeration cycle device, 20 refrigeration cycle, 22 first flow path, 24 compressor, 25 compression section, 26 motor, 27 inverter, 28 condenser, 30 first expansion valve, 32 evaporator, 40 bypass system, 42 second flow path, 44 second expansion valve, 50 ECU.

Claims

[Claim 1] A refrigeration cycle device comprising: a refrigeration cycle in which a compressor, a condenser, a first expansion valve, and an evaporator are provided in this order in a first flow path through which a refrigerant flows; a bypass system in which a second expansion valve is provided in a second flow path that branches off from between the compressor and the condenser of the first flow path and joins the first flow path between the compressor and the evaporator; and a control device, When a request for heat generation by the compressor is made, the control device controls the motor so that a d-axis current of the motor is increased and controls the second expansion valve so that a flow rate of the refrigerant in the second flow path is increased, compared to when a request for heat generation by the compressor is not made. Refrigeration cycle equipment.

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