Inverter-integrated electric machine

Abstract

To provide an inverter-integrated electric machine in which the temperature of a switching element can be estimated with high precision.SOLUTION: An inverter-integrated electric machine includes an electric motor 11, an inverter 10, a switching unit 21, and an inverter housing. The inverter 10 includes a driver 24, the switching unit 21, a temperature detection unit 15 that detects a cooling water temperature for cooling a switching element Q, and a control unit 30 that controls the switching unit 21. The control unit 30 includes a loss identification unit 38 that identifies loss in the switching unit 21 on the basis of the cooling water temperature, a heat resistance identification unit 39 that identifies heat resistance of the switching element Q on the basis of the cooling water temperature, a temperature estimation unit 40 that estimates the temperature of the switching element Q on the basis of the loss and the heat resistance, and a PWM control unit 37 that, if the estimated temperature of the switching element Q is high, controls the driver 24 to suppress output of the switching element Q.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an inverter-integrated electric motor. [Background technology]

[0002] Conventionally, a technology has been known in which a temperature detection unit such as a thermistor is provided for each of a plurality of switching elements included in an inverter (see, for example, Patent Document 1). In this inverter, the purpose is to protect the switching elements by limiting the current flowing through the switching elements when the temperature of each switching element exceeds a predetermined threshold. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-261078 Summary of the Invention [Problem to be solved by the invention]

[0004] However, it may be difficult for a temperature detector provided near a switching element to accurately detect the internal temperature of the switching element. Therefore, with the technology disclosed in Patent Document 1, it is necessary to provide a margin for the threshold value of the switching element temperature based on the detection accuracy of the temperature detector, which may prevent the inverter from fully utilizing its performance. [Means for solving the problem]

[0005] An inverter-integrated electric motor that achieves the above-mentioned object comprises an electric motor having a rotor that rotates integrally with a rotating shaft and a cylindrical stator around which a coil is wound and the rotor is arranged on the inner circumference, an inverter that drives the electric motor, and a housing that accommodates the electric motor and the inverter and has a cooling water passage through which cooling water flows to cool the inverter, wherein the inverter comprises a driver, a switching unit having a switching element driven by the driver and not having a temperature detection function, a temperature detection unit that detects the temperature of the cooling water, and a control unit that controls the switching unit, and the control unit comprises a loss identification unit that identifies a loss in the switching unit based on the temperature of the cooling water, a thermal resistance identification unit that identifies the thermal resistance of the switching element based on the temperature of the cooling water, a temperature estimation unit that estimates the temperature of the switching element based on the loss and the thermal resistance, and an operation control unit that controls the driver to suppress the output of the switching element if the temperature of the switching element estimated by the temperature estimation unit is high.

[0006] According to this configuration, the temperature of the switching element can be estimated with high accuracy. In the inverter-integrated electric motor that achieves the above object, the loss identifying unit may identify the loss further based on a flow rate of the cooling water flowing through a cooling water passage.

[0007] According to this configuration, the temperature of the switching element can be estimated with even greater accuracy. An inverter-integrated electric motor that achieves the above-mentioned object may further include an element temperature detection unit that detects the temperature of the switching elements for each arm, and a phase loss identification unit that identifies a phase loss, which is a loss for each arm, based on the detection result of the element temperature detection unit and the loss, wherein the temperature estimation unit estimates the temperature of each switching element based on the phase loss and the thermal resistance of each switching element, and the operation control unit controls the driver to suppress the output of a switching element that has a higher temperature among the plurality of switching elements.

[0008] According to this configuration, the temperature of the switching elements can be estimated with higher accuracy, and the performance of each switching element can be fully utilized. [Effects of the Invention]

[0009] According to the present invention, the temperature of the switching element can be estimated with high accuracy. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram used to explain an electric compressor. [Figure 2] FIG. 2 is a diagram used to explain the electric compressor. [Figure 3] FIG. 3 is a diagram showing an example of a cooling water channel. [Figure 4] FIG. 4 is a flowchart illustrating an example of processing by the control unit. [Figure 5] FIG. 5 is a diagram used to explain a modified electric compressor. [Figure 6] FIG. 6 is a diagram used to explain the installation position of the element temperature detection unit. [Figure 7] FIG. 7 is a flowchart showing another example of the process of the control unit. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Embodiment] Hereinafter, embodiments of an electric motor and an electric compressor will be described with reference to the drawings. <Overall structure> The configuration of a vehicle air conditioner 100 will be described with reference to FIGS. 1 and 2. As shown in FIGS. 1 and 2, the vehicle air conditioner 100 of this embodiment includes an electric compressor 101 and a refrigerant circuit 103. The electric compressor 101 includes a compression unit 102 and an inverter-integrated electric motor M1. The electric compressor 101 compresses a refrigerant. The compression unit 102 and the inverter-integrated electric motor M1 are housed in a housing 104. The housing 104 includes a compression unit housing 105 that houses the compression unit 102, an inverter housing 106 that houses the inverter-integrated electric motor M1, and a motor housing 107. The refrigerant circuit 103 includes, for example, a heat exchanger and an expansion valve. The vehicle air conditioner 100 cools or heats the interior of the vehicle by compressing the refrigerant using the electric compressor 101 and exchanging heat and expanding the refrigerant using the refrigerant circuit 103. The electric compressor 101 discharges oil together with the compressed refrigerant.

[0012] <Electric compressor> As described above, the compression section 102 is accommodated in the compression section housing 105. The compression section housing 105 is fixed to the motor housing 107. The motor housing 107 has an intake port 50. The intake port 50 is connected to the refrigerant circuit 103. The compression section housing 105 has a discharge port 51. The discharge port 51 is connected to the refrigerant circuit 103.

[0013] The compression section 102 compresses the refrigerant drawn into the housing 104 from the suction port 50. The compressed refrigerant is discharged from the discharge port 51 to the refrigerant circuit 103. The compression section 102 may be of any type, such as a centrifugal type, a scroll type, a piston type, or a vane type. The motor 28 drives the compression section 102.

[0014] <Inverter-integrated electric motor> The inverter-integrated electric motor M1 includes an electric motor 11. The electric motor 11 is housed in a cylindrical motor housing 107. The electric motor 11 has a rotor 12 and a stator 13 around which three-phase coils U, V, and W are wound. The electric motor 11 is a three-phase motor equipped with three coils U, V, and W. The rotor 12 rotates integrally with the rotating shaft. The stator 13 is fixed to the inner circumferential surface of the peripheral wall 114 of the motor housing 107. The stator 13 is, for example, cylindrical. The rotor 12 is disposed on the inner circumferential side of the stator 13. The rotor 12 rotates when current is applied to the coils U, V, and W. The compression unit 102 is driven by the rotation of the rotor 12. As a result, the compression unit 102 compresses the fluid.

[0015] The inverter-integrated electric motor M1 includes an inverter 10. The inverter 10 is accommodated in an inverter housing 106. Specifically, the inverter housing 106 is fixed to the motor housing 107 and is provided on the outer circumferential surface of a peripheral wall 114 of the motor housing 107. The inverter housing 106 is provided on the motor housing 107 to define an accommodation space A1. That is, the inverter 10 is provided in the accommodation space A1 between the outer circumferential surface of the peripheral wall 114 of the motor housing 107 and the inverter housing 106. Accordingly, the inverter 10 is provided on the outer circumferential surface of the peripheral wall 114 of the motor housing 107 and is covered by the inverter housing 106.

[0016] The inverter 10 includes a circuit board BD. The circuit board BD is plate-shaped. A filter circuit FT, a smoothing capacitor C, a temperature detection unit 15, a switching unit 21, a phase current detection unit 22, an input voltage detection unit 23, a control unit 30, and a storage unit 80 are electrically connected to the circuit board BD.

[0017] The inverter-integrated electric motor M1 includes a cooling water passage 14 through which cooling water flows to cool the stator 13 and the inverter 10. The cooling water passage 14 is formed in a peripheral wall 114 of the motor housing 107. The cooling water passage 14 is formed between the stator 13 and heat-generating elements that constitute the inverter 10. The heat-generating elements are provided between the peripheral wall 114 of the motor housing 107, in which the cooling water passage 14 is formed, and the circuit board BD. The heat-generating elements include, for example, elements that constitute the filter circuit FT, a smoothing capacitor C, and a switching unit 21. The cooling water passage 14 is defined inside the peripheral wall 114 of the motor housing 107. Cooling water cooled by a cooling unit (not shown) circulates through the cooling water passage 14 by the operation of a pump (not shown) or the like, thereby cooling the heat-generating elements. The temperature detection unit 15 detects the temperature of the cooling water flowing through the cooling water passage 14.

[0018] The switching unit 21 has arms the number of which corresponds to the phases of the power to be converted. In this embodiment, the switching unit 21 has three-phase legs, i.e., u-phase, v-phase, and w-phase of the electric motor 11, and each leg has two arms, an upper arm and a lower arm. Therefore, the switching unit 21 of this embodiment has six arms. The switching unit 21 also has a plurality of switching elements Q, the number of which corresponds to each arm. The switching unit 21 of this embodiment has two switching elements Q for each arm. In other words, the switching unit 21 has 12 switching elements Q. The switching unit 21 also has diodes D the number of which corresponds to the switching elements Q. Specifically, the switching unit 21 has switching elements Q1u to Q4u associated with the u-phase, switching elements Q1v to Q4v associated with the v-phase, and switching elements Q1w to Q4w associated with the w-phase. The switching unit 21 also has diodes D1u to D4u, diodes D1v to D4v, and diodes D1w to D4w. In the following description, when the switching elements Q1u to Q4u, Q1v to Q4v, and Q1w to Q4w are collectively referred to, they will simply be referred to as switching elements Q. Furthermore, when there is no need to distinguish between the u-phase, v-phase, and w-phase configurations of the switching elements Q1u to Q4u, Q1v to Q4v, and Q1w to Q4w, diodes D1u to D4u, diodes D1v to D4v, and diodes D1w to D4w, the suffixes u, v, and w will be omitted from the reference numerals.

[0019] The switching elements Q1 to Q4 may be, for example, IGBTs (Insulated Gate Bipolar Transistors) or MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) in which the switching elements Q1 to Q4 and the diodes D1 to D4 are integrated. The switching elements Q1 and Q2 are connected in parallel. The switching elements Q3 and Q4 are connected in parallel. The switching elements Q1 and Q2, and the switching elements Q3 and Q4 are connected in series between the positive and negative terminals of a battery BA. Diodes D1 to D4 are connected in parallel to the switching elements Q1 to Q4, respectively. Furthermore, a smoothing capacitor C and a filter circuit FT are connected in parallel to the battery BA between the battery BA and the switching elements Q1 to Q4.

[0020] The connection lines between the switching elements Q1u, Q2u and the switching elements Q3u, Q4u branch off midway and are connected to the coil U. The connection lines between the switching elements Q1v, Q2v and the switching elements Q3v, Q4v branch off midway and are connected to the coil V. The connection lines between the switching elements Q1w, Q2w and the switching elements Q3w, Q4w branch off midway and are connected to the coil W.

[0021] The switching unit 21 includes a driver 24. The driver 24 drives the switching elements Q1u to Q4u, Q1v to Q4v, and Q1w to Q4w under the control of the control unit 30. This drives the electric motor 11. The battery BA is a chargeable and dischargeable power storage device. The rated voltage of the battery BA is, for example, 800 V. The filter circuit FT removes noise superimposed on the power supplied by the battery BA.

[0022] 3 shows a schematic diagram of an example of the cooling water passage 14. As described above, the cooling water passage 14 is provided in the peripheral wall 114 of the motor housing 107. In addition to the various components described above, the circuit board BD also includes an internal power supply circuit, a communication circuit, and the like. The internal power supply circuit converts the voltage of the power supplied by the battery BA into various voltages used by the control unit 30 and supplies them. The communication circuit is a circuit used for communication between the control unit 30 and other devices, such as a vehicle in which the electric compressor is installed.

[0023] As shown in FIG. 3, the cooling water channel 14 is disposed below the packages PK1 to PK6 so that the packages PK1 to PK6 are cooled by the cooling water flowing through the cooling water channel 14. The package PK1 configures circuit components corresponding to the upper arm of the u-phase in the circuit related to the switching unit 21. Specifically, the package PK1 configures switching elements Q1u to Q2u and diodes D1u to D2u. The package PK2 configures circuit components corresponding to the lower arm of the u-phase in the circuit related to the switching unit 21. Specifically, the package PK2 configures switching elements Q3u to Q4u and diodes D3u to D4u. The package PK3 configures circuit components corresponding to the upper arm of the v-phase in the circuit related to the switching unit 21. Specifically, the package PK3 configures switching elements Q1v to Q2v and diodes D1v to D2v. The package PK4 configures circuit components corresponding to the lower arm of the v-phase in the circuit related to the switching unit 21. Specifically, package PK4 contains switching elements Q3v-Q4v and diodes D3v-D4v. Package PK5 contains circuit components corresponding to the upper arm of the w-phase in the circuit related to switching unit 21. Specifically, package PK5 contains switching elements Q1w-Q2w and diodes D1w-D2w. Package PK6 contains circuit components corresponding to the lower arm of the w-phase in the circuit related to switching unit 21. Specifically, package PK6 contains switching elements Q3w-Q4w and diodes D3w-D4w. Packages PK1-PK6 do not include a functional unit with a temperature detection function. Furthermore, packages PK1-PK6 are realized by, for example, discrete components.

[0024] As a result, the cooling water channel 14 cools the switching element Q with the cooling water flowing therethrough. In the example shown in FIG. 3, the cooling water channel 14 cools not only the switching element Q but also the driver 24 and the control unit 30. The driver 24 and the control unit 30 are provided downstream of the cooling water channel 14 relative to the switching element Q. The temperature detection unit 15 is provided, for example, at a position in the cooling water channel 14 that is downstream of positions corresponding to the packages PK1 to PK6 and upstream of positions corresponding to the driver 24 and the control unit 30, so as to detect the temperature of the cooling water. As a result, the temperature detection unit 15 detects the temperature of the cooling water after cooling only the switching element Q among the various components of the switching unit 21.

[0025] Returning to FIG. 1 , the phase current detection unit 22 detects the phase currents flowing through the electric motor 11. The phase current detection unit 22 detects the phase currents for at least two phases. In this embodiment, the phase current detection unit 22 detects a u-phase current Iu, a v-phase current Iv, and a w-phase current Iw. It is also possible to detect the phase currents for two of the three phases, and calculate the phase current for the remaining phase from the phase currents for the two phases. The u-phase current Iu, the v-phase current Iv, and the w-phase current Iw are actual currents flowing through the respective phases of the electric motor 11.

[0026] The input voltage detection unit 23 detects the input voltage Vi input to the switching unit 21 from the battery BA. <Control unit> The control unit 30 is realized by, for example, a hardware processor such as a CPU (Central Processing Unit) executing a program (software). Some or all of these components may be realized by hardware (including circuitry) such as an LSI (Large Scale Integration), an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a GPU (Graphics Processing Unit), or may be realized by a combination of software and hardware. The program may be stored in advance in a storage device (not shown) that includes a non-transitory storage medium such as an HDD (Hard Disk Drive) or flash memory provided in the storage unit 80.

[0027] The storage unit 80 may be realized by the various storage devices described above, or an EEPROM (Electrically Erasable Programmable Read Only Memory), a ROM (Read Only Memory), a RAM (Random Access Memory), or the like.

[0028] The control unit 30 calculates a plurality of command values. The control unit 30 controls the switching element Q based on the plurality of command values. The control unit 30 controls the switching unit 21 by sensorless control. Sensorless control is a method of controlling the switching unit 21 without using a hardware position sensor that detects the position of the rotor 12 of the electric motor 11. As the sensorless control, the control unit 30 performs position estimation using an induced voltage method. The induced voltage method is a method of estimating the position of the rotor 12 based on the induced voltage generated in the three-phase coils U, V, and W. The electric motor 11 is driven by controlling the switching unit 21.

[0029] The control unit 30 includes a current coordinate conversion unit 31, a position estimation unit 32, a subtraction unit 33, a speed command control unit 34, a subtraction unit 35, a current command control unit 36, a PWM control unit 37, a loss identification unit 38, a thermal resistance identification unit 39, and a temperature estimation unit 40.

[0030] The current coordinate conversion unit 31 acquires the position of the rotor 12 from the position estimation unit 32. The current coordinate conversion unit 31 converts the phase currents Iu, Iv, and Iw into a d-axis current Id and a q-axis current Iq based on the position of the rotor 12. The d-axis and q-axis are coordinate axes of a dq coordinate system. The dq coordinate system is a coordinate system that rotates together with the rotor 12 of the electric motor 11.

[0031] The position estimation unit 32 acquires the d-axis current Id and the q-axis current Iq from the current coordinate conversion unit 31. The position estimation unit 32 acquires the d-axis voltage command value Vd and the q-axis voltage command value Vq from the current command control unit 36. The position estimation unit 32 calculates the induced voltages generated in the coils U, V, and W based on the d-axis current Id and the q-axis current Iq, the d-axis voltage command value Vd and the q-axis voltage command value Vq, and constants determined by the electric motor 11. The position estimation unit 32 then estimates the position of the rotor 12 based on the induced voltages. The position estimation unit 32 estimates the rotational speed of the rotor 12 based on the induced voltages. The rotational speed of the rotor 12 estimated by the position estimation unit 32 is the detected speed value ω.

[0032] The subtraction unit 33 calculates a speed deviation Δω, which is the difference between the speed command value ω* and the detected speed value ω estimated by the position estimation unit 32. The speed command value ω* is a target value for the rotational speed of the rotor 12. The speed command value ω* is input from an external device. For example, the speed command value ω* is input to the control unit 30 from a higher-level control device of the vehicle.

[0033] The speed command control unit 34 calculates a motor current command value Iα, which is a target current value, based on the speed deviation Δω. For example, the speed command control unit 34 calculates a d-axis current command value IdRef and a q-axis current command value IqRef using feedback control so that the speed deviation Δω converges to 0. The feedback control is, for example, proportional-integral control.

[0034] The subtraction unit 35 calculates the difference ΔId between the d-axis current command value IdRef and the d-axis current Id, and calculates the difference ΔIq between the q-axis current command value IqRef and the q-axis current Iq. The current command control unit 36 ​​calculates a d-axis voltage command value Vd based on the difference ΔId. The current command control unit 36 ​​calculates a q-axis voltage command value Vq based on the difference ΔIq. The current command control unit 36 ​​calculates the d-axis voltage command value Vd and the q-axis voltage command value Vq by using, for example, feedback control so that the differences ΔId and ΔIq converge to 0. As the feedback control, for example, proportional-integral control can be used.

[0035] The PWM control unit 37 converts the d-axis voltage command value Vd and the q-axis voltage command value Vq into a u-phase voltage command value Vu, a v-phase voltage command value Vv, and a w-phase voltage command value Vw based on the position of the rotor 12 estimated by the position estimator 32, the input voltage Vi, and the temperature of the switching element Q identified by the temperature estimator 40. Details of the process by which the PWM control unit 37 converts into the u-phase voltage command value Vu, the v-phase voltage command value Vv, and the w-phase voltage command value Vw based on the temperature of the switching element Q identified by the temperature estimator 40 will be described later.

[0036] The driver 24 drives the switching elements Q1u to Q4u, Q1v to Q4v, and Q1w to Q4w based on the u-phase voltage command value Vu, v-phase voltage command value Vv, and w-phase voltage command value Vw output by the PWM control unit 37. The PWM control unit 37 corresponds to an operation control unit.

[0037] The switching unit 21 is controlled based on the voltage command values ​​Vu, Vv, and Vw. More specifically, the PWM control unit 37 generates a PWM signal based on the voltage command values ​​Vu, Vv, and Vw and a carrier frequency, and controls the switching element Q by the PWM signal.

[0038] The loss identifying unit 38 identifies the loss of the switching unit 21 based on the coolant temperature detected by the temperature detecting unit 15. The loss identifying unit 38 identifies the loss of the switching unit 21 at room temperature based on, for example, the carrier frequency associated with the control of the PWM control unit 37, the u-phase current Iu, the v-phase current Iv, and the w-phase current Iw detected by the phase current detecting unit 22, and the input voltage Vi detected by the input voltage detecting unit 23. The loss identifying unit 38 then corrects the identified loss of the switching unit 21 at room temperature to a greater extent as the coolant temperature detected by the temperature detecting unit 15 is higher than a reference temperature, and corrects the identified loss of the switching unit 21 at room temperature to a smaller extent as the coolant temperature is lower than the reference temperature.

[0039] The reference temperature is, for example, a temperature that matches the coolant temperature detected by the temperature detection unit 15 during normal operation of the switching unit 21. When the coolant temperature detected by the temperature detection unit 15 is higher than the reference temperature, the switching unit 21 is operating under high load, and the loss of the switching unit 21 is larger than during normal operation. On the other hand, when the coolant temperature detected by the temperature detection unit 15 is lower than the reference temperature, the switching unit 21 is operating under low load, and the loss of the switching unit 21 is smaller than during normal operation. The loss determination unit 38 corrects the loss of the switching unit 21 at normal temperature based on this characteristic.

[0040] The thermal resistance specifying unit 39 specifies the thermal resistance of the switching element Q based on the coolant temperature detected by the temperature detecting unit 15. Here, the temperature of the coolant flowing through the cooling water passage 14 and the thermal resistance of the switching element Q are correlated. The higher the coolant temperature, the smaller the thermal resistance of the switching element Q, and the lower the coolant temperature, the larger the thermal resistance of the switching element Q. The thermal resistance specifying unit 39 specifies the thermal resistance of the switching element Q based on, for example, thermal resistance information indicating the correspondence between the coolant temperature and the thermal resistance of the switching element Q. In this embodiment, the thermal resistance specifying unit 39 specifies that all of the switching elements Q1u to Q4u, Q1v to Q4v, and Q1w to Q4w have the same thermal resistance.

[0041] The temperature estimator 40 estimates the temperature of the switching element Q based on the loss of the switching unit 21 identified by the loss identifyr 38, the thermal resistance of the switching element Q identified by the thermal resistance identifyr 39, and the coolant temperature detected by the temperature detector 15. Specifically, the temperature estimator 40 estimates the junction temperature of the switching element Q as the sum of the coolant temperature and a value obtained by multiplying the loss of the switching unit 21 by the thermal resistance. The temperature estimator 40 of this embodiment estimates the junction temperature of the switching elements Q1u to Q4u, Q1v to Q4v, and Q1w to Q4w as being the same.

[0042] When the junction temperature of switching element Q estimated by temperature estimation unit 40 is high, PWM control unit 37 controls switching unit 21 to suppress the output of switching element Q. For example, when the estimated junction temperature of switching element Q is higher than a reference junction temperature, PWM control unit 37 determines that the junction temperature of switching element Q is high and suppresses the output of switching element Q. The reference junction temperature is, for example, a temperature that is predetermined as a recommended operating temperature of switching element Q. As described above, PWM control unit 37 converts the d-axis voltage command value Vd and the q-axis voltage command value Vq into a u-phase voltage command value Vu, a v-phase voltage command value Vv, and a w-phase voltage command value Vw. On the other hand, when the estimated junction temperature of the switching element Q is high, the PWM control unit 37 performs conversion processing so that the u-phase voltage command value Vu, the v-phase voltage command value Vv, and the w-phase voltage command value Vw become smaller than the u-phase voltage command value Vu, the v-phase voltage command value Vv, and the w-phase voltage command value Vw that are based on the d-axis voltage command value Vd and the q-axis voltage command value Vq, thereby suppressing the output of the switching element Q.

[0043] <Processing executed in the control unit> A series of processes executed by the control unit 30 will be described with reference to Fig. 4. The processes of the flowchart shown in Fig. 4 are repeatedly executed at predetermined time intervals. In parallel with the flowchart shown in Fig. 4, basic processes are executed until the PWM control unit 37 derives the u-phase voltage command value Vu, the v-phase voltage command value Vv, and the w-phase voltage command value Vw.

[0044] First, the control unit 30 acquires information indicating the temperature of the coolant flowing through the cooling water passage 14 from the temperature detection unit 15 (step S100). Next, the loss identification unit 38 identifies the loss of the switching unit 21 based on the coolant temperature detected by the temperature detection unit 15 (step S102). The higher the coolant temperature detected by the temperature detection unit 15 is relative to a reference temperature, the greater the loss is corrected relative to the loss of the switching unit 21 in normal operation, and the lower the coolant temperature is relative to the reference temperature, the smaller the loss is corrected relative to the loss of the switching unit 21 in normal operation.

[0045] Next, the thermal resistance specifying unit 39 specifies the thermal resistance of the switching element Q based on the coolant temperature detected by the temperature detecting unit 15 (step S106). The thermal resistance specifying unit 39 specifies the thermal resistance of the switching element Q based on, for example, thermal resistance information indicating the correspondence between the coolant temperature and the thermal resistance of the switching element Q.

[0046] Next, the temperature estimation unit 40 estimates the temperature of the switching element Q based on the loss of the switching unit 21 identified by the loss identification unit 38, the thermal resistance of the switching element Q identified by the thermal resistance identification unit 39, and the coolant temperature detected by the temperature detection unit 15 (step S108). The temperature estimation unit 40 estimates, for example, the sum of the coolant temperature and a value obtained by multiplying the loss of the switching unit 21 by the thermal resistance, as the junction temperature of the switching element Q.

[0047] Next, the PWM control unit 37 controls the operation of the switching unit 21 based on the junction temperature of the switching element Q estimated by the temperature estimator 40 (step S110). Specifically, if the estimated junction temperature of the switching element Q is high, the PWM control unit 37 controls the switching unit 21 to suppress the output of the switching element Q. More specifically, if the estimated junction temperature of the switching element Q is high, the PWM control unit 37 performs conversion processing so that the u-phase voltage command value Vu, the v-phase voltage command value Vv, and the w-phase voltage command value Vw are smaller than the u-phase voltage command value Vu, the v-phase voltage command value Vv, and the w-phase voltage command value Vw, which are based on the d-axis voltage command value Vd and the q-axis voltage command value Vq. This suppresses the output of the switching element Q. On the other hand, if the estimated junction temperature of the switching element Q is not high, the PWM control unit 37 controls the driver 24 in the normal manner without suppressing the output of the switching element Q.

[0048] [Effects of the embodiment] According to the above embodiment, the following effects can be obtained. (1) The control unit 30 includes a PWM control unit 37, a loss identification unit 38, a thermal resistance identification unit 39, and a temperature estimation unit 40. The loss identification unit 38 identifies the loss of the switching unit 21 based on the coolant temperature detected by the temperature detection unit 15. The thermal resistance identification unit 39 identifies the thermal resistance of the switching element Q based on the coolant temperature detected by the temperature detection unit 15. The temperature estimation unit 40 estimates the junction temperature of the switching element Q based on the identified loss and thermal resistance. If the junction temperature of the switching element Q estimated by the temperature estimation unit 40 is high, the PWM control unit 37 controls the switching unit 21 to suppress the output of the switching element Q.

[0049] As described above, the packages PK1 to PK6 do not include a functional unit with a temperature detection function. Accordingly, a commonly known method for identifying the junction temperature of the switching element Q involves providing a temperature detection unit near the switching element Q and estimating the junction temperature from the detection result of the temperature detection unit. However, this method does not allow for accurate detection of the temperature of the switching element Q, and there are cases where the output of the switching element Q is suppressed even if the switching element Q still has operating capacity. Therefore, this method makes it difficult to fully utilize the performance of the inverter 10.

[0050] As described above, the temperature estimation unit 40 estimates the junction temperature of the switching element Q based on the coolant temperature of the coolant that cools the switching element Q. Here, the coolant temperature correlates with the junction temperature of the switching element Q, but does not change suddenly. Therefore, the coolant temperature can be used as a stable variable when estimating the junction temperature of the switching element Q. With this configuration, the junction temperature of the switching element Q can be accurately detected based on the coolant temperature. Therefore, the inverter 10 can fully utilize its performance.

[0051] The above-described embodiments may be modified as follows: The above-described embodiments and the following modifications may be combined with each other within the scope of technical compatibility. [Variations] In the above-described embodiment, the case where the temperature estimator 40 estimates that all of the switching elements Q1u to Q4u, Q1v to Q4v, and Q1w to Q4w have the same junction temperature has been described. In the modified example, a case where the junction temperature is estimated for the switching element Q of each arm of the switching unit 21 will be described. Note that the same reference numerals are used for the same components as in the above-described embodiment, and descriptions thereof will be omitted.

[0052] As shown in Fig. 5, the inverter 10 of the modified example includes an element temperature detection unit 16 and a control unit 30a. The element temperature detection unit 16 is provided near the switching element Q of each arm of the switching unit 21, and detects the temperature of the switching element Q for each arm. As described above, the switching unit 21 includes three legs of the u-phase, v-phase, and w-phase of the electric motor 11, and each leg includes two arms, an upper arm and a lower arm. Therefore, the inverter 10 of the modified example includes six element temperature detection units 16, namely, element temperature detection units 16a to 16f.

[0053] As shown in FIG. 6, element temperature detectors 16a-16f are provided, for example, near each package PK. Specifically, element temperature detector 16a is provided near package PK1 and detects the temperature of switching elements Q1u-Q2u in the u-phase upper arm. Element temperature detector 16b is provided near package PK2 and detects the temperature of switching elements Q3u-Q4u in the u-phase lower arm. Element temperature detector 16c is provided near package PK3 and detects the temperature of switching elements Q1v-Q2v in the v-phase upper arm. Element temperature detector 16d is provided near package PK4 and detects the temperature of switching elements Q3v-Q4v in the v-phase lower arm. Element temperature detector 16e is provided near package PK5 and detects the temperature of switching elements Q1w-Q2w in the w-phase upper arm. Element temperature detector 16f is provided near package PK6 and detects the temperature of switching elements Q3w-Q4w in the w-phase lower arm.

[0054] Returning to FIG. 5 , the inverter 10 of this modified example includes a control unit 30a instead of the control unit 30. The control unit 30a includes a phase loss identification unit 41 in addition to the components included in the control unit 30. The phase loss identification unit 41 identifies the phase loss, which is the loss for each arm, based on the detection results of the element temperature detection units 16a to 16f and the loss of the switching unit 21 identified by the loss identification unit 38. Specifically, the phase loss identification unit 41 allocates the loss of the switching unit 21 identified by the loss identification unit 38 based on the ratio of the temperatures detected by the element temperature detection units 16a to 16f. For example, the phase loss identification unit 41 allocates a high loss value to an arm in which a high temperature is detected as the phase loss of that arm, and allocates a low loss value to an arm in which a low temperature is detected as the phase loss of that arm. The phase loss identification unit 41 also allocates the phase losses so that the sum of the phase losses allocated to each arm matches the loss identified by the loss identification unit 38.

[0055] The temperature estimator 40 of the modified example estimates the temperature of each switching element Q based on the phase loss of each arm identified by the phase loss identifier 41, the thermal resistance of the switching element Q identified by the thermal resistance identifier 39, and the coolant temperature detected by the temperature detector 15. Specifically, the temperature estimator 40 estimates the junction temperature of the switching element Q by the sum of the phase loss of the arm corresponding to the switching element Q multiplied by the thermal resistance of the switching element Q and the coolant temperature. The temperature estimator 40 estimates the junction temperature for each switching element Q. The processing of the PWM controller 37 is similar to that of the above-described embodiment, and therefore description thereof will be omitted.

[0056] <Processing executed in the control unit> A series of processes executed by the control unit 30a will be described with reference to Fig. 7. In the processes of the flowchart shown in Fig. 7, the same processes as those in the flowchart shown in Fig. 4 are denoted by the same reference numerals, and description thereof will be omitted.

[0057] After the process of step S102, the phase loss identifying unit 41 acquires the detection results of the temperatures of the switching elements Q for each arm from the element temperature detecting units 16a to 16f (step S200). Next, the phase loss identifying unit 41 identifies the phase loss, which is the loss for each arm, based on the detection results of the element temperature detecting units 16a to 16f and the loss of the switching unit 21 identified by the loss identifying unit 38 (step S202). For example, the phase loss identifying unit 41 assigns a high loss value to an arm in which a high temperature is detected as the phase loss of that arm, and assigns a low loss value to an arm in which a low temperature is detected as the phase loss of that arm. Furthermore, the phase loss identifying unit 41 assigns the phase losses so that the sum of the phase losses assigned to each arm matches the loss identified by the loss identifying unit 38.

[0058] In step S108 of the modified example, the temperature estimation unit 40 estimates the temperature of each switching element Q based on the phase loss of each arm identified by the thermal resistance identification unit 39, the thermal resistance of each switching element Q identified by the thermal resistance identification unit 39, and the coolant temperature detected by the temperature detection unit 15.

[0059] [Effects of the modified version] The inverter 10 of the modified example includes element temperature detectors 16a to 16f. The element temperature detectors 16a to 16f detect the temperature of the switching element Q for each arm. The inverter 10 of the modified example includes a control unit 30a. The control unit 30a includes a phase loss identifier 41. The phase loss identifier 41 identifies a phase loss, which is a loss for each arm, based on the detection results of the element temperature detectors 16a to 16f and the loss identified by the loss identifier 38. The thermal resistance identifier 39 of the modified example identifies the thermal resistance of each switching element Q based on the coolant temperature detected by the temperature detector 15 and the phase loss identified by the phase loss identifier 41. The temperature estimator 40 of the modified example estimates the temperature of each switching element Q based on the phase loss for each arm identified by the thermal resistance identifier 39, the thermal resistance of each switching element Q identified by the thermal resistance identifier 39, and the coolant temperature detected by the temperature detector 15. The PWM control unit 37 of the modified example controls the switching unit 21 so as to suppress the output of the switching element Q having a high temperature among the plurality of switching elements Q estimated by the temperature estimation unit 40.

[0060] With this configuration, the inverter 10 can accurately estimate the junction temperature of each switching element Q based on the temperature of each switching element Q detected by the element temperature detection unit 16. Therefore, the inverter 10 can fully utilize its own performance.

[0061] Furthermore, the inverter 10 includes a smaller number (six in the modified example) of element temperature detectors 16a-16f than when each of the 12 switching elements Q has a temperature detection function, which makes it possible to suppress the increase in cost of the inverter 10 due to the inclusion of a temperature detection function.

[0062] The loss identifying unit 38 may identify the loss of the switching unit 21 further based on the flow rate of the coolant flowing through the cooling water passage 14. The loss identifying unit 38 identifies the loss of the switching unit 21 when the flow rate of the coolant is normal, for example, based on the carrier frequency associated with the control of the PWM control unit 37, the u-phase current Iu, the v-phase current Iv, and the w-phase current Iw detected by the phase current detection unit 22, and the input voltage Vi detected by the input voltage detection unit 23. The loss identifying unit 38 then corrects the identified loss of the switching unit 21 when the flow rate of the coolant is normal by a larger amount as the flow rate of the coolant is smaller than the reference flow rate, and corrects the identified loss of the switching unit 21 when the flow rate of the coolant is greater than the reference flow rate.

[0063] The reference flow rate is, for example, the flow rate of cooling water flowing through the cooling water passage 14 when the switching unit 21 is operating normally. When the flow rate of cooling water is lower than the reference flow rate, the switching unit 21 is operating under high load, and the loss of the switching unit 21 is larger than during normal operation. When the flow rate of cooling water is higher than the reference flow rate, the switching unit 21 is operating under low load, and the loss of the switching unit 21 is smaller than during normal operation. The loss identifying unit 38 corrects the loss of the switching unit 21 during normal operation based on this characteristic.

[0064] The temperature detection unit 15 may be provided at a position other than the above-described position. Here, among the components of the switching unit 21, the temperature change caused to the cooling water by the driver 24 and the control unit 30 is sufficiently smaller than the temperature change caused by the switching element Q. Therefore, the temperature detection unit 15 may be provided at any position in the cooling water channel 14.

[0065] The thermal resistance specifying unit 39 may specify the thermal resistance of the switching element Q further based on the flow rate of the cooling water flowing through the cooling water passage 14. In this case, the thermal resistance specifying unit 39 specifies the thermal resistance of the switching element Q based on thermal resistance information indicating the correspondence between the cooling water temperature, the flow rate of the cooling water, and the thermal resistance of the switching element Q.

[0066] The temperature of the switching element Q estimated by the temperature estimator 40 may be the internal temperature of the package PK instead of the junction temperature of the switching element Q. The cooling water passage 14 may be designed to cool only the switching element Q. In this case, the cooling water passage 14 does not have a portion for cooling the driver 24 or the control units 30 and 30a.

[0067] The control unit 30 may estimate the position of the rotor 12 using a harmonic superposition method instead of (or in addition to) the induced voltage method. The circuit board BD that constitutes the switching unit 21 does not necessarily have to include an internal power supply circuit, a communication circuit, and the like.

[0068] The inverter 10 does not need to include the filter circuit FT if an appropriate power is supplied from the battery BA. The process of step S102 and the process of step S200 shown in FIG. 7 may be executed in the reverse order.

[0069] As described above, the switching unit 21 may include a plurality of switching elements Q, the number of which corresponds to each arm. Therefore, the switching unit 21 may include, for example, one switching element Q in each arm, or may include three or more switching elements Q connected in parallel in each arm. In this case, the package PK may include a switching element Q provided in each arm and diodes D in a number corresponding to the number of switching elements Q.

[0070] The compression unit 102 used in the vehicle air conditioner 100 of this embodiment may be an air compressor that is mounted on a fuel cell vehicle and compresses atmospheric air to supply the compressed air to the fuel cell. Alternatively, the compression unit 102 may be a pump, such as a hydrogen pump that is mounted on a fuel cell vehicle and circulates hydrogen to the fuel cell. [Explanation of symbols]

[0071] 10... inverter, 11... electric motor, 12... rotor, 13... stator, 14... cooling water channel, 15... temperature detection unit, 16, 16a, 16b, 16c, 16d, 16e, 16f... element temperature detection unit, 21... switching unit, 22... phase current detection unit, 23... input voltage detection unit, 24... driver, 30, 30a... control unit, 31... current coordinate conversion unit, 32... position estimation unit, 33, 35... subtraction unit, 34... speed command control unit, 36... current command control unit, 37... PWM control unit, 38... loss identification unit, 39... thermal resistance identification unit, 40... temperature estimation unit, 41... phase loss identification unit, 80... memory unit, 100... vehicle air conditioning device, 101... electric compression a compressor, 102...compression section, 103...refrigerant circuit, 104...housing, BA...battery, BD...circuit board, C...smoothing capacitor, D, D1, D1u, D1v, D1w, D2, D2u, D2v, D2w, D3, D3u, D3v, D3w, D4, D4u, D4v, D4w...diodes, FT...filter circuit, M1...inverter-integrated motor, PK, PK1, PK2, PK3, PK4, PK5, PK6...package, Q, Q1, Q1u, Q1v, Q1w, Q2, Q2u, Q2v, Q2w, Q3, Q3u, Q3v, Q3w, Q4, Q4u, Q4v, Q4w...switching elements, and U, V, W...coil.

Claims

1. an electric motor having a rotor that rotates integrally with a rotary shaft, and a cylindrical stator around which a coil is wound and the rotor is disposed on the inner periphery thereof; an inverter that drives the electric motor; a housing that accommodates the electric motor and the inverter and has a cooling water passage through which cooling water flows to cool the inverter, The inverter is With the driver, a switching unit including a switching element driven by the driver, the switching element having no temperature detection function; a temperature detection unit that detects the temperature of the cooling water; a control unit that controls the switching unit, The control unit a loss specifying unit that specifies a loss in the switching unit based on the temperature of the cooling water; a thermal resistance specifying unit that specifies the thermal resistance of the switching element based on the temperature of the cooling water; a temperature estimator that estimates a temperature of the switching element based on the loss and the thermal resistance; an operation control unit that controls the driver to suppress an output of the switching element when the temperature of the switching element estimated by the temperature estimating unit is high; An inverter-integrated electric motor equipped with

2. the loss identifying unit identifies the loss further based on a flow rate of the cooling water flowing through a cooling water passage. The inverter-integrated electric motor according to claim 1 .

3. the switching unit has arms, the number of which corresponds to the phases of the power to be converted, and a plurality of the switching elements, the number of which corresponds to the arms; an element temperature detection unit that detects the temperature of the switching element for each arm; a phase loss specifying unit that specifies a phase loss, which is a loss for each arm, based on a detection result of the element temperature detecting unit and the loss, the temperature estimator estimates a temperature of each of the switching elements based on the phase loss and the thermal resistance of each of the switching elements; the operation control unit controls the driver to suppress the output of the switching element having a high temperature among the plurality of switching elements.

3. The inverter-integrated electric motor according to claim 1 or 2.

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