Temperature measurement device, power conversion device, drive device, and diagnosis method

Abstract

A temperature measurement device for measuring the temperature of an object to be measured, the temperature measurement device being provided with: a temperature measurement element attached to the object to be measured; a switching unit that changes the amount of current flowing through the temperature measuring element; and a diagnosis unit that determines that an abnormality has occurred in the temperature measurement element when the amount of current flowing through the temperature measurement element is increased by the switching unit and the amount of change in the temperature measured by the temperature measurement element is out of a normal range that is a variable range corresponding to the value measured by the temperature measurement element.

Description

Technical Field

[0001] This invention relates to a temperature measuring device, a power conversion device, a driving device, and a diagnostic method. Background Technology

[0002] A power conversion device and drive unit convert DC power supplied from a DC power source into AC power to drive a motor. The motor's output torque varies according to the motor's magnetic flux, which in turn varies according to the motor's temperature. To maintain a constant output torque independent of motor temperature, the power conversion device and drive unit sometimes adjust the current flowing through the motor based on the motor temperature. In this case, if the motor temperature sensing unit malfunctions, the power conversion device and drive unit will incorrectly adjust the current flowing through the motor, resulting in undesirable fluctuations in the motor's output torque. Therefore, techniques for diagnosing malfunctions of the temperature sensing unit are known. Patent Document 1 discloses a battery pack control device, characterized by comprising: a detection unit that detects a physical quantity representing the battery state of a battery pack composed of multiple units; a diagnostic unit that diagnoses an abnormal state of the detection unit; an estimation unit that estimates the charging state of the battery pack based on the physical quantity detected by the detection unit; a setting unit that, when an abnormality is diagnosed by the diagnostic unit, sets an allowable charge / discharge range representing the range of charging states in which the battery pack can be used based on the abnormality; and a control unit that controls the charging and discharging of the battery pack in such a way that the charging state estimated by the estimation unit is within the allowable charge / discharge range.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2011-041422 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] In the invention described in Patent Document 1, there is room for improvement in dealing with situations where the temperature of the object being measured fluctuates significantly.

[0008] Methods for solving problems

[0009] A temperature measuring device according to a first aspect of the present invention measures the temperature of a temperature measuring object. The temperature measuring device includes: a switching unit that changes the amount of current flowing through a temperature measuring element mounted on the temperature measuring object; and a diagnostic unit that performs diagnostic processing, wherein if, when the amount of change in temperature measured by the temperature measuring element deviates from the normal range when the amount of current flowing through the temperature measuring element is increased by the switching unit, the temperature measuring element is determined to be malfunctioning, and the normal range refers to a variable range corresponding to the value measured by the temperature measuring element.

[0010] The second aspect of the power conversion device of the present invention is a power conversion device that includes the temperature measuring device described above, and has a power conversion circuit that supplies power to the object to be measured.

[0011] The third aspect of the present invention is a drive device that includes the temperature measuring device described above, and includes a motor as the object of the temperature measurement.

[0012] The fourth aspect of the present invention is a diagnostic method performed by a temperature measuring device for measuring the temperature of an object to be measured. The diagnostic method includes: a switching process to change the amount of current flowing through a temperature measuring element installed on the object to be measured; and a diagnostic process in which, when the amount of current flowing through the temperature measuring element is increased by the switching process, and the change in temperature measured by the temperature measuring element deviates from the normal range, it is determined that the temperature measuring element has malfunctioned. The normal range refers to a variable range corresponding to the value measured by the temperature measuring element.

[0013] The effects of the invention

[0014] According to the present invention, even in environments where the temperature of the object being measured fluctuates significantly, it is possible to accurately diagnose malfunctions of the temperature measuring element. Attached Figure Description

[0015] Figure 1 This is a diagram of a vehicle equipped with a drive unit.

[0016] Figure 2 This is a diagram of the drive unit.

[0017] Figure 3 It is a diagram of the power conversion circuit and the motor.

[0018] Figure 4 This is a schematic diagram of the motor temperature detection circuit.

[0019] Figure 5 This is a flowchart illustrating the processes handled by the diagnostic department.

[0020] Figure 6A diagram illustrating the concept of a normal range table.

[0021] Figure 7 This is a schematic diagram of the motor temperature detection circuit according to the second embodiment.

[0022] Figure 8 A flowchart illustrating the processing of the diagnostic unit in the second embodiment.

[0023] Figure 9 This is a configuration diagram of the drive device according to the third embodiment.

[0024] Figure 10 A flowchart illustrating the processing of the diagnostic unit in the third embodiment.

[0025] Figure 11 A flowchart illustrating the processing of the diagnostic unit in the fourth embodiment.

[0026] Figure 12 A graph showing the state of the switch and its voltage and temperature characteristics.

[0027] Figure 13 This is a flowchart illustrating the diagnostic process performed by the diagnostic department to check for switch adhesion.

[0028] Figure 14 This is a configuration diagram of the drive device according to the fifth embodiment. Detailed Implementation

[0029] —First Embodiment—

[0030] The following is for reference Figures 1-6 This describes the first embodiment of the power conversion device and drive device, also known as a temperature measuring device.

[0031] Figure 1 This is a configuration diagram of a vehicle 900 equipped with a drive unit 1. The drive unit 1 includes a power conversion device 2 (described later), a motor 3 (described later), and a reducer 4 (not shown). The drive unit 1 controls the power conversion device 2 and the motor 3 to generate driving force according to the driver's operation of the accelerator pedal, and transmits the driving force to the front wheel axle 902F via the reducer.

[0032] In addition, Figure 1 In this vehicle 900, a drive unit 1 is installed on the front axle 902F, but it can also be installed on the rear axle 902B. Alternatively, the drive unit 1 can be installed on both the front axle 902F and the rear axle 902B, or it can be installed independently on each of the left and right wheels instead of on the axles. Furthermore, the vehicle 900 may also possess a power source other than the drive unit 1, such as an engine.

[0033] Figure 2This is a configuration diagram of drive unit 1. A DC power supply 910, a control unit 920, and a fault notification device 930 are connected to drive unit 1. Control unit 920 sends data indicating the target torque C2 and operating mode C1 to drive unit 1. Control unit 920 receives a fault notification signal C3 output by drive unit 1. Although in Figure 2 Only one control device 920 is described, but multiple control devices 920 may exist. In this case, for example, different control devices 920 may output target torque C2 and operating mode C1, or multiple control devices 920 may receive fault notification signal C3.

[0034] The DC power supply 910 is a power source for driving the motor 3 built into the drive unit 1, such as a battery. When the fault notification device 930 receives a fault notification signal C3 from the drive unit 1, it notifies the occupants of the vehicle 900 of the occurrence of the fault. The fault notification device 930 notifies the occupants of the fault by means of methods such as illuminating lights, generating a warning sound, or providing audible notification.

[0035] The drive unit 1 includes a power conversion device 2, a motor 3, and a reducer (not shown). The reducer amplifies the driving force of the motor 3 and transmits it to the axle or wheel. The motor 3 is a three-phase electric motor with three windings inside, such as a synchronous motor using permanent magnets or an induction motor without permanent magnets. The motor 3 includes a motor angle sensor 31 for measuring the angle of the motor 3, and a temperature measuring element 32 for measuring the temperature of the motor 3.

[0036] The motor angle sensor 31 outputs the measured angle as the motor angle sensor value to the power conversion device 2. The temperature measuring element 32 is, for example, a thermistor or a diode. In this embodiment, an example of using an NTC (Negative Temperature Coefficient) thermistor as the temperature measuring element is described.

[0037] The power conversion device 2 converts the DC power obtained from the DC power supply 910 into AC power to drive the motor 3. In addition, the power conversion device 2 also has the function of converting the power from the motor 3 into DC power to charge the DC power supply 910. Internally, the power conversion device 2 includes a control circuit 21, a drive circuit 22, a power conversion circuit 23, a DC voltage sensor 24, an AC current sensor 25, and a motor temperature detection circuit 26. The power conversion circuit 23 receives the drive signal C5 from the drive circuit 22, drives the internal power semiconductor, and controls the current flowing through the motor 3. (Refer to...) Figure 3 Explain the internal structure of the power conversion circuit 23.

[0038] Figure 3This is a schematic diagram of the power conversion circuit 23 and the motor 3. The power conversion circuit 23 includes a smoothing capacitor 231 and six power semiconductors 232. The power semiconductors switch the six power semiconductors 232 on and off according to the drive signal C5 input from the drive circuit 22, thereby converting DC power to AC power. The power semiconductors 232 are, for example, power MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) or IGBTs (Insulated Gate Bipolar Transistors).

[0039] The smoothing capacitor 231 is used to smooth the current generated by the switching of the power semiconductor 232 on and off, and to suppress the ripple of the DC current supplied from the DC power supply 910 to the power conversion circuit 23. This smoothing capacitor 231 is, for example, an electrolytic capacitor or a film capacitor. In this embodiment, the motor neutral point 3C is in a floating state, but it can also be connected to a ground (not shown). Methods for connecting the motor neutral point to ground include direct grounding, resistor grounding, compensation reactor grounding, and arc suppression reactor grounding.

[0040] Back Figure 2 The DC voltage sensor 24 measures the output voltage of the DC power supply 910 and outputs the measured voltage value to the control circuit 21. The AC current sensor 25 measures the AC current flowing through each phase (U phase, V phase, W phase) of the motor 3 and outputs the measured AC current value to the control circuit 21. In this embodiment, one AC current sensor 25 is provided for each phase, for a total of three, but only two phases of AC current sensors 25 may be provided. Since the sum of the U phase current, V phase current, and W phase current is zero, this relationship and the output of two AC current sensors 25 can be used to calculate the current of the remaining phase. In this case, the control circuit 21 calculates the AC current sensor value of the remaining phase.

[0041] The drive circuit 22 receives the PWM (Pulse Width Modulation) signal C4 output by the control circuit 21 and outputs a drive signal C5 to switch the power semiconductor 232 on and off. The motor temperature detection circuit 26 applies a voltage to the temperature measuring element 32 mounted on the motor 3 and outputs the voltage value to the control circuit 21. Furthermore, the motor temperature detection circuit 26 switches its internal circuitry based on the signal output from the control circuit 21. This internal circuitry is the switch SW1, described later.

[0042] The control circuit 21 communicates with the external control device 920, receiving the operating mode C1 and target torque C2 from the control device 920. Based on the operating mode C1 and target torque C2, the control circuit 21 controls the PWM signal to control the current of each phase output from the power conversion device 2 to a predetermined value, driving the power conversion circuit 23 via the drive circuit 22. Furthermore, if the control circuit 21 determines that an internal fault has occurred, it outputs a fault notification signal C3 to the control device 920 and the fault notification device 930.

[0043] The control circuit 21 internally includes a CPU, RAM, ROM, and communication circuitry (not shown). The control circuit 21 may use an electrically rewritable EEROM (Electrically Erasable Programmable ROM) or flash memory ROM instead of a traditional ROM. The control circuit 21 includes a status control unit 211, a target current calculation unit 212, a current control unit 213, a PWM signal generation unit 214, a motor speed calculation unit 215, a motor temperature calculation unit 216, and a diagnostic unit 217. The status control unit 211, target current calculation unit 212, current control unit 213, PWM signal generation unit 214, motor speed calculation unit 215, motor temperature calculation unit 216, and diagnostic unit 217 are implemented by the CPU loading and executing a program stored in the ROM into the RAM.

[0044] The control circuit 21 can also be implemented by a microcomputer, an FPGA (Field Programmable Gate Array) as a rewritable logic circuit, or an ASIC (Application Specific Integrated Circuit). Alternatively, it can be implemented by a combination of two or more of the following: CPU, ROM, RAM, microcomputer, FPGA, and ASIC.

[0045] The motor speed calculation unit 215 calculates the motor rotation speed based on the change in the value of the motor angle sensor and outputs the calculated motor speed value to the target current calculation unit 212. The motor temperature calculation unit 216 calculates the motor temperature based on the voltage value output from the motor temperature detection circuit and outputs the calculated motor temperature value to the target current calculation unit 212 and the diagnostic unit 217. The status control unit 211 uses the operation mode C1 and the fault notification signal C3 output by the diagnostic unit 217 to change the operation state of the power conversion device 2 and outputs the current operation state to the PWM signal generation unit 214. The operation state may be, for example, PWM state, 3-phase short circuit state, 3-phase open circuit state, etc.

[0046] The target current calculation unit 212 calculates the current value that should flow through the motor 3 and outputs this current value as the target current value to the current control unit 213. When calculating the current value that should flow through the motor 3, the target torque C2, the DC voltage sensor value, the motor speed value, and the motor temperature value are used. The calculated current value that should flow through the motor 3 is the current value that should flow through the motor 3 so that the motor 3 outputs the same torque as the target torque C2. The target current value is expressed, for example, as a d-axis target current value and a q-axis target current value.

[0047] The output torque T of the synchronous motor can be calculated using the following formula 1. In formula 1, the number of pole pairs of motor 3 is set as Pp, the magnetic flux of motor 3 is set as Φ, the d-axis inductance of motor 3 is set as Ld, the q-axis inductance of motor 3 is set as Lq, the d-axis current flowing through motor 3 is set as Id, and the q-axis current flowing through motor 3 is set as Iq.

[0048] T=Pp{ΦIq+(Ld-Lq)IdIq}…(Formula 1)

[0049] Here, as the motor temperature rises, the motor flux Φ decreases. Therefore, in order to keep the output torque T constant regardless of the motor temperature, it is necessary to increase or decrease the values ​​of the d-axis target current and the q-axis target current according to the motor temperature. The target current calculation unit 212 corrects the target current according to the motor temperature.

[0050] The current control unit 213 performs feedback control by having the AC current flowing through the motor follow the target current value, and calculates the duty cycle value of the three phases. Then, the current control unit 213 outputs the duty cycle value to the PWM signal generation unit 214. In the above feedback control of the current control unit 213, the target current value, the AC current sensor value, the motor angle sensor value, and the DC voltage sensor value are used.

[0051] The PWM signal generation unit 214 switches the signal output to the drive circuit 22 according to the operating state output from the state control unit 211. The PWM signal generation unit 214 has an internal timer (not shown). When the operating state is PWM state, the PWM signal generation unit 214 uses the timer value and the duty cycle of each phase output by the current control unit 213 to generate the PWM signal C4. When the operating state is a 3-phase open circuit state, the PWM signal generation unit 214 generates the PWM signal C4 that disconnects all six power semiconductors built into the power conversion circuit 23.

[0052] When the operation is in a three-phase short-circuit state, the PWM signal generation unit 214 generates a PWM signal C4 that either disconnects the upper arms and connects the lower arms of all six power semiconductors built into the power conversion circuit 23, or connects the upper arms and disconnects the lower arms. The PWM signal generation unit 214 outputs the generated PWM signal C4 to the drive circuit 22.

[0053] The diagnostic unit 217 diagnoses faults in the temperature sensing element 32 mounted on the motor 3 or the motor temperature detection circuit 26 inside the power conversion device 2. If a fault is detected, the diagnostic unit 217 outputs the fault location as a fault notification signal C3 to the status control unit 211 and the fault notification device 930. The diagnostic unit 217 includes a normal range table 2171 (described later) for diagnosing the motor temperature detection circuit 26.

[0054] Since the power conversion device 2 has a built-in motor temperature detection circuit 26 and a motor temperature calculation unit 216, it can be called a "temperature measuring device". In addition, the drive device 1 that includes the power conversion device 2 can also be called a "temperature measuring device".

[0055] Figure 4 This is a schematic diagram of the motor temperature detection circuit 26. The motor temperature detection circuit 26 internally includes an internal power supply 26P1, resistors R1 and R2, and a switch SW1. The state of switch SW1 is controlled by the diagnostic unit 217 within the control circuit 21. The resistance value of resistor R2 is smaller than that of resistor R1. When switch SW1 is open, the voltage of the internal power supply 26P1 is divided by resistor R1 and the temperature measuring element 32. Normally, switch SW1 is open when measuring temperature. Furthermore, switch SW1 will sometimes be referred to as a "switching unit" below.

[0056] When switch SW1 is closed, the voltage of the internal power supply 26P1 is divided by the parallel resistor R1 and resistor R2 combined with the temperature measuring element 32. Since the resistance of the parallel resistor R1 and resistor R2 is smaller than the resistance of resistor R1, a larger current flows through the temperature measuring element 32 when switch SW1 is closed compared to when switch SW1 is open. This current causes the temperature measuring element 32 to generate more heat.

[0057] Figure 5This is a flowchart illustrating the diagnostic process of the diagnostic unit 217. This diagnostic process is performed by the diagnostic unit 217 at least once during startup of the power conversion device 2 and for a certain time period after startup. In step S301, the diagnostic unit 217 measures the temperature of the temperature measuring element 32. Hereinafter, the temperature measured in this step will be referred to as the "steady-state temperature". In the next step S302, the diagnostic unit 217 turns on the switch SW1 built into the motor temperature detection circuit 26. In the next step S303, the diagnostic unit 217 remains in standby mode for a predetermined period of time.

[0058] In the next step S304, the diagnostic unit 217 turns the switch SW1 built into the motor temperature detection circuit 26 to the open state. In the next step S305, the diagnostic unit 217 measures the temperature of the temperature measuring element 32. Hereinafter, the temperature measured in step S305 will be referred to as the "temperature after current increase". In the next step S306, the diagnostic unit 217 determines the normal range of temperature change corresponding to the stable temperature.

[0059] Figure 6 This is a diagram illustrating the concept of Normal Range Table 2171. Normal Range Table 2171 is pre-generated. Normal Range Table 2171 contains data showing the correspondence between stable temperature and normal ranges of temperature variation. Figure 6 In the diagram, the horizontal axis represents the steady-state temperature, and the vertical axis represents the temperature change. Figure 6 The vertical distance between the two solid lines shown represents the normal temperature range. Dashed lines and single-dot lines will be explained later. Furthermore, a temperature change exceeding the normal range indicates an abnormality of low resistance in the temperature measuring element 32, while a temperature change below the normal range indicates an abnormality of high resistance in the temperature measuring element 32.

[0060] Specifically, based on the resistance values ​​of the temperature measuring element 32 at various temperatures, the temperature change when switch SW1 is turned on can be calculated in advance, and a value that includes the measurement error added to the normal temperature change is set as the normal temperature change range. Furthermore, the measurement error can be set as a certain percentage of the normal temperature change, such as 5% or 10%, or it can be set as a fixed value such as 1°C or 3°C, independent of the normal temperature change. Additionally, in Figure 6 The normal range table 2171 is represented by a curve graph, but it can also be represented in tabular form or by formulas such as polynomials. Return Figure 5 Let me continue explaining.

[0061] In the next step S307, the diagnostic unit 217 calculates the temperature change, which is the difference between the steady-state temperature and the temperature after the current increase, and determines whether the temperature change falls within the normal range determined in step S306. If the diagnostic unit 217 determines that the temperature change falls within the normal temperature change range, it proceeds to step S308; if it determines that the temperature change does not fall within the normal temperature change range, it proceeds to step S309. In step S308, the diagnostic unit 217 determines that the temperature measuring element 32 is normal, i.e., no abnormality is detected, and ends the process. Figure 5 The process is as shown. In step S309, the diagnostic unit 217 outputs information indicating a malfunction of the temperature measuring element 32 as a fault notification signal C3 to the status control unit 211 and the fault notification device 930, thus ending the process. Figure 5 The processing is shown.

[0062] The effects of this implementation method are as follows. Figure 6 In the diagram, dashed lines represent the temperature change when the resistance of temperature sensing element 32 decreases, and dotted lines represent the temperature change when the resistance of temperature sensing element 32 increases. If the resistance of temperature sensing element 32 decreases, the current flowing through it increases, the heat generated by temperature sensing element 32 increases, and therefore the temperature change also increases. Conversely, when the resistance of temperature sensing element 32 increases, the current flowing through it decreases, the heat generated by temperature sensing element 32 decreases, and therefore the temperature change also decreases. Therefore, it is possible to detect faults where the resistance of temperature sensing element 32 decreases or increases by a certain amount due to temperature changes.

[0063] Furthermore, as in this embodiment, by varying the normal temperature range according to the stable temperature, the temperature measuring element 32 can be appropriately diagnosed regardless of the temperature of the object being measured. In this embodiment, the object being measured is the motor 3, whose temperature is affected by the current driving conditions. For example, if the motor 3 has not been driven for a long time, its temperature becomes approximately equal to the ambient temperature; if the motor 3 has just been driven, its temperature becomes high. The temperature of the temperature measuring element 32 is close to the temperature of the motor 3, which is the object being measured, and the resistance value of the temperature measuring element 32 changes according to its temperature.

[0064] Furthermore, since the temperature change during diagnosis is affected by the resistance value of the temperature measuring element 32, the normal temperature variation range varies depending on the temperature of the object being measured. When the object being measured is always at a constant temperature, even if the normal temperature variation range is fixed, a fault in the temperature measuring element 32 can be accurately diagnosed. However, if a fixed normal temperature variation range is used when the temperature of the object being measured changes drastically, as in this embodiment, problems may arise where the temperature measuring element 32 is functioning normally but is still misdiagnosed as faulty, or where the temperature measuring element 32 is faulty but is still misdiagnosed as normal.

[0065] According to the first embodiment described above, the following effects can be obtained.

[0066] (1) The power conversion device 2, also known as a temperature measuring device, measures the temperature of the motor 3, which is the object of temperature measurement. It includes: a switch SW1 that changes the amount of current flowing through the temperature measuring element 32 mounted on the motor 3; and a diagnostic unit 217 that, when the amount of current flowing through the temperature measuring element 32 is increased by the switch SW1, and the change in temperature measured by the temperature measuring element 32 deviates from the normal range (…). Figure 5 S307: No), indicating that the temperature measuring element 32 has malfunctioned. The normal range refers to the variable range corresponding to the value measured by the temperature measuring element 32, as determined by referring to the normal range table 2171. Figure 5 (S306). Therefore, even in environments where the temperature of the object being measured fluctuates significantly, it is possible to accurately diagnose faults in the temperature measuring element.

[0067] (2) The power conversion device 2 is equipped with a power conversion circuit 23 that supplies power to the motor 3, which is the object of temperature measurement.

[0068] (3) The drive device 1 includes a motor 3, which is the object of temperature measurement.

[0069] (Variation Example 1)

[0070] In this embodiment, a diagnosis is described for the temperature measuring element 32 used to measure the temperature of the motor, but the object of temperature measurement is not limited to the motor 3. For example, when using the same temperature detection circuit and temperature measuring element 32 as in this embodiment as the circuit for measuring the temperature of the power semiconductor and control circuit 21, the method described in this embodiment can be used to detect faults in the temperature measuring element 32.

[0071] —Second Implementation—

[0072] Reference Figures 7-8This describes a second embodiment of the power conversion device and drive device, also known as a temperature measuring device. In the following description, the same reference numerals are used for components identical to those in the first embodiment; the main differences are explained. For points not specifically described, the process is the same as in the first embodiment. The main difference in this embodiment compared to the first embodiment lies in the handling of the temperature when it is below a predetermined threshold during stable operation.

[0073] Figure 7 This is a configuration diagram of the motor temperature detection circuit 26A according to the second embodiment. In addition to the configuration of the motor temperature detection circuit 26 in the first embodiment, the motor temperature detection circuit 26A also includes a second internal power supply 26P2 and a second switch SW2. The voltage of the second internal power supply 26P2 is higher than the voltage of the internal power supply 26P1. The state of the second switch SW2 is controlled by the diagnostic unit 217 within the control circuit 21. In this embodiment, both the switch SW1 and the second switch SW2 are referred to as "switching units". The operation of the switching units is controlled by the diagnostic unit 217 in the same manner as in the first embodiment.

[0074] Figure 8 This is a flowchart illustrating the processing of the diagnostic unit 217 in the second embodiment. In step S301, the diagnostic unit 217 measures the temperature of the temperature measuring element 32, i.e., the stable temperature. In the next step S312, the diagnostic unit 217 determines whether the stable temperature exceeds a second threshold, which is a predetermined threshold. If the diagnostic unit 217 determines that the stable temperature exceeds the first threshold, it performs the processing of steps S302 to S304 in the same manner as in the first embodiment.

[0075] If the diagnostic unit 217 determines that the stable temperature does not exceed the first threshold, it proceeds to step S314. In steps S314 to S316, the diagnostic unit 217 turns on the second switch SW2 and turns it off after a certain standby time. Furthermore, the "certain time" in step S315 is the same length as the "certain time" in step S303. When either step S304 or S316 is completed, the diagnostic unit 217 performs the processing of steps S305 to S309 in the same way as in the first embodiment. Additionally, the normal range table 2171 in this embodiment differs from that in the first embodiment. When the stable temperature is below the first threshold, the second switch SW2 is turned on, and the temperature measuring element 32 is warmer than in the first embodiment; therefore, the normal range table 2171 is generated taking this effect into account.

[0076] The effects of this embodiment are as follows. In the first embodiment... Figure 6In the example where the temperature is low during stable operation, the temperature change during normal operation and during a fault is not significantly different, making it difficult to accurately determine the fault of the temperature measuring element 32. This is because if the temperature measuring element 32 is low, its resistance is high, so even if the resistance of the temperature measuring element 32 increases or decreases due to a fault, the temperature change will not differ significantly. To solve this problem, in the second embodiment, when the temperature is low during stable operation, by turning on the second switch SW2, a second internal power supply 26P2 with a voltage higher than that of the internal power supply 26P1 is applied to the resistor R2 and the temperature measuring element 32. The current flowing through the temperature measuring element 32 is greater than when switch SW1 is turned on. As a result, the temperature change of the temperature measuring element 32 is greater than when switch SW1 is turned on, thus enabling a more accurate determination of the fault of the temperature measuring element 32.

[0077] According to the second embodiment described above, the following effects can be obtained.

[0078] (4) When the value measured by the temperature measuring element is less than the first threshold, the diagnostic unit 217 ( Figure 8 In case S312: No), the value measured by the temperature measuring element is greater than the first threshold. Figure 8 Compared to S312, the current supplied to the temperature sensing element 32 based on switch SW is increased. Therefore, even at low temperatures, the fault of the temperature sensing element 32 can be determined more accurately.

[0079] (A variation of the second embodiment)

[0080] In the second embodiment described above, when the stable temperature is below the first threshold, the second switch SW2 is turned on. Since the voltage of the second internal power supply 26P2 is higher than that of the internal power supply 26P1, more current flows per unit time when the second switch SW2 is turned on compared to when the switch SW1 is turned on. However, the current per unit time can remain unchanged while the application time is varied. That is, the energizing time can be extended instead of increasing the energizing current.

[0081] —Third Implementation—

[0082] Reference Figures 9-10 This describes a third embodiment of the power conversion device and drive device, also known as a temperature measuring device. In the following description, the same reference numerals are used for components identical to those in the first embodiment, and the main differences are explained. Points not specifically described are the same as in the first embodiment. The main difference in this embodiment compared to the first embodiment is that the diagnosis is performed after heating the motor at low temperatures.

[0083] Figure 9This is a configuration diagram of the drive device 1B according to the third embodiment. The diagnostic unit 217 of the third embodiment outputs a motor drive request signal to the state control unit 211 and the target current calculation unit 212. The state control unit 211 changes its current operating state based on the motor drive request signal from the diagnostic unit 217. The target current calculation unit 212 changes the value of the target current based on the motor drive request signal from the diagnostic unit 217.

[0084] Figure 10 This is a flowchart illustrating the processing of the diagnostic unit 217 in the third embodiment. In step S331, the diagnostic unit 217 measures the temperature of the temperature measuring element 32, i.e., the stable temperature. However, in this embodiment, this step is sometimes performed multiple times, as described later. In this case, the last measured temperature is taken as the stable temperature. In other words, the stable temperature is updated each time step S331 is performed.

[0085] In the next step S332, the diagnostic unit 217 determines whether the temperature measured in step S331 is greater than the second threshold. If the diagnostic unit 217 determines in step S331 that the measured temperature is greater than the second threshold, it proceeds to step S334; if it determines in step S331 that the measured temperature is less than the second threshold, it proceeds to step S333. In step S333, the diagnostic unit 217 applies current to the motor 3 and returns to step S331. Upon returning from step S333 to step S331, current continues to be applied to the motor until the measured temperature exceeds the second threshold. Furthermore, the second threshold may be the same as the first threshold in the second embodiment, or it may be a different value.

[0086] Step S333 will be described in detail below. The diagnostic unit 217 outputs a motor drive request signal to the status control unit 211 and the target current calculation unit 212. The status control unit 211 receives the motor drive request signal from the diagnostic unit 217 and, if the current operating state is a 3-phase short circuit or a 3-phase open circuit, switches the operating state to PWM mode. The target current calculation unit 212 receives the motor drive request signal from the diagnostic unit 217 and increases the total target current within a certain range, provided the change in motor output torque is within a certain value. For example, if motor 3 is in a stopped state and the motor output torque is 0 Nm, and only d-axis current flows through motor 3, then according to the formula in Formula 1, the total target current can be increased even when the motor output torque is 0 Nm.

[0087] Furthermore, according to Formula 1, the q-axis current affects both the torque generated by the motor flux and the torque generated by the inductance, while the d-axis current only affects the torque generated by the inductance. Therefore, the output torque of the synchronous motor is more significantly affected by the q-axis current, while the effect of the d-axis current is less. Thus, when motor 3 is in a driving state and both d-axis and q-axis currents flow through it, increasing the d-axis current while decreasing the q-axis current, while maintaining the output torque of motor 3, can increase the total target current while reducing the change in output torque. Additionally, if the output torque of motor 3 changes drastically by altering the target current, it will affect the operation of the vehicle. Therefore, in this embodiment, the target current is varied within a range where the change in motor output torque will not affect operation.

[0088] In step S334, the diagnostic unit 217 stops applying current to the motor 3, which began in step S333, and executes the processing after step S302. The processing after step S302 is the same as in the first embodiment, so its description is omitted. In addition, the normal range table 2171 in this embodiment can be the same as in the first embodiment. This is because, when the temperature is low at the beginning of the processing of the diagnostic unit 217, the stable temperature is forced to be higher than the second threshold through the processing of steps S331 to S333, so it is not necessary to consider the situation of low stable temperature as in the second embodiment.

[0089] The effects of this embodiment are as follows. As described in the second embodiment, in the method of the first embodiment, when the temperature of the temperature measuring element 32 is low at the start of the operation of the diagnostic unit 217, it is difficult to accurately determine the fault of the temperature measuring element 32. As a solution to this problem, in the third embodiment, when the temperature is low at stable conditions, the current flowing through the motor 3 is increased to heat up the motor 3, and the diagnosis is performed after the temperature at stable conditions exceeds the second threshold, thereby enabling a more accurate determination of the fault of the temperature measuring element 32.

[0090] According to the third embodiment described above, the following effects can be obtained.

[0091] (5) The temperature measurement object of the motor temperature detection circuit 26 is the motor 3. The diagnostic unit 217 detects when the value measured by the temperature measuring element 32 is less than the second threshold. Figure 10 If S332: No), current flows through motor 3 (S333). If the value measured by temperature measuring element 32 exceeds the second threshold (S332: Yes), an abnormality judgment is made on temperature measuring element 32 (S302~S309). Therefore, even at low temperatures, the fault of temperature measuring element 32 can be determined more accurately.

[0092] (6) The diagnostic unit 217 controls the current to be the maximum when the torque output by the motor 3 is within a certain range from the target value (S333).

[0093] —Fourth Implementation—

[0094] Reference Figures 11-13 This describes a fourth embodiment of the power conversion device and drive device, also known as a temperature measuring device. In the following description, the same reference numerals are used for components identical to those in the first embodiment; the main differences are explained. Points not specifically described are the same as in the first embodiment. The main difference in this embodiment compared to the first embodiment lies in detecting the sticking of the switch built into the motor temperature sensing circuit 26.

[0095] In the first embodiment, the switch SW1 built into the motor temperature detection circuit 26 is switched to determine the fault of the temperature measuring element 32. However, if the switch SW1 malfunctions, correct temperature measurement and fault determination cannot be performed. For example, if a fault occurs (disconnection and sticking fault) when the switch SW1 is turned on, the current flowing through the temperature measuring element 32 does not increase, and the temperature measuring element 32 cannot heat up. As a result, the temperature difference between the current-increased temperature and the stable temperature disappears, and in the diagnosis of the temperature measuring element 32, it is possible that the temperature measuring element 32 is not faulty but is incorrectly determined to be faulty.

[0096] Furthermore, if a fault occurs during the process of controlling switch SW1 to the open state, causing switch SW1 to become closed (closed sticking fault), the temperature of switch SW1 in the open state cannot be measured. Therefore, when diagnosing the temperature measuring element 32, it is possible that the temperature measuring element 32 is not faulty but is incorrectly identified as faulty. Therefore, it is necessary to determine whether the switch SW1 is experiencing open sticking faults or closed sticking faults.

[0097] Figure 11 This is a flowchart illustrating the processing of the diagnostic unit 217 in the fourth embodiment. Figure 11 It is in the first embodiment Figure 5 A diagram for diagnosing the disconnection and sticking fault of switch SW1 has been added. Figure 5 The same processing is omitted. Figure 11 In the process shown, steps S301 and S302 are performed in the same manner as in the first embodiment. Then, immediately after the switch SW1 is turned on, the diagnostic unit 217 measures the temperature again in step S351.

[0098] In the next step S352, the diagnostic unit 217 calculates the temperature change, which is the difference between the stable temperature and the temperature in step S351, and determines whether the temperature change is greater than or equal to a third threshold. If the temperature change is determined to be greater than or equal to the third threshold, the diagnostic unit 217 performs the same processing as in the first embodiment after step S303. If the temperature change is determined to be less than the third threshold, the diagnostic unit 217 proceeds to step S353, outputting information indicating that the switch SW1 has disconnected and stuck as a fault notification signal C3 to the status control unit 211 and the fault notification device 930, and then ends the process. Figure 5 The processing is shown.

[0099] Furthermore, in the event of a disconnection and sticking fault in switch SW1, the temperature measuring element 32 cannot be correctly diagnosed. Therefore, after detecting a disconnection and sticking fault in switch SW1, diagnostic processing for the temperature measuring element 32 is not performed.

[0100] Figure 12 This is a graph showing the voltage and temperature characteristics when switch SW1 is open (hereinafter referred to as "open state") and closed (hereinafter referred to as "closed state"). Figure 12 In the diagram, solid lines represent the ON state and dashed lines represent the OFF state. Since the resistance of resistor R2 is smaller than that of resistor R1, when switch SW1 changes from OFF to OFF, resistors R1 and R2 become connected in parallel, with R2's resistance being only smaller than that of resistor R1. As a result, the voltage measured by diagnostic unit 217 increases as switch SW1 changes from OFF to OFF.

[0101] For example, when the current measured temperature is Ta, the measured voltage in the off state is Va, and when the control is on state, the measured voltage changes to Vb. When the motor temperature calculation unit 216 converts the measured voltage into temperature based on the voltage-temperature characteristic of the switch SW1 in the off state, since the measured temperature is Tb when the measured voltage is Vb, the measured temperature changes from Ta to Tb when the switch SW1 changes from the off state to the on state.

[0102] Assuming a disconnection / adhesion fault occurs in switch SW1, even if the diagnostic unit 217 controls switch SW1 to be on, switch SW1 remains in the off state. In this case, the voltage measured by the diagnostic unit 217 remains constant Va, and the measured temperature also remains constant Ta. Therefore, if the difference between the measured temperature when switch SW1 is off and the measured temperature when switch SW1 is on is less than the third threshold, it can be determined that switch SW1 has a disconnection / adhesion fault.

[0103] As the third threshold, for example, the temperature change when switching switch SW1 from open to closed can be pre-calculated for each measured temperature and used based on the current measured temperature. Alternatively, as the third threshold, the minimum value among the pre-calculated temperature changes for each measured temperature when switching switch SW1 can be used, as described above. Furthermore, in this embodiment, the difference in measured temperatures is used to determine the open / sticky fault of switch SW1, but the difference in measured voltage can also be used for the same fault determination.

[0104] Figure 13 This is a flowchart illustrating the diagnostic process for switch SW1's connection adhesion performed by the diagnostic unit 217. This process is implemented by the diagnostic unit 217 at regular intervals after the power conversion device 2 is started. First, in step S371, the diagnostic unit 217 measures the temperature of the temperature measuring element 32. In the next step S372, the diagnostic unit 217 calculates the temperature difference between the temperature measured in step S371 and the previously measured temperature, and determines whether the temperature difference is above a fourth threshold. However, if step S372 is executed for the first time after the power conversion device 2 is started, since the previously measured temperature is not available, the process proceeds from step S371 to step S375, ending the process. Figure 13 The processing is shown.

[0105] In step S372, if the diagnostic unit 217 determines that the temperature difference is above the fourth threshold, it proceeds to step S373; if it determines that the temperature difference is below the fourth threshold, it proceeds to step S374. In step S373, the diagnostic unit 217 outputs information indicating that switch SW1 has a connection sticking fault as a fault notification signal C3 to the status control unit 211 and the fault notification device 930, and proceeds to step S375. In step S374, the diagnostic unit 217 determines that the condition is normal, i.e., there is no connection sticking in switch SW1, and proceeds to step S375. In step S375, the diagnostic unit 217 saves the data for use in the next diagnostic test, based on the temperature measured in step S371, and then ends the process. Figure 13 The processing is shown.

[0106] If a fault of switch SW1 being stuck on during operation is detected, the temperature of switch SW1 when it is off cannot be measured, therefore the diagnosis of temperature measuring element 32 cannot be performed correctly. Therefore, after a fault of switch SW1 being stuck on during operation is detected, the diagnosis of temperature measuring element 32 is not performed. In other words, in this embodiment, the diagnosis of temperature measuring element 32 is performed only when neither a fault of switch SW1 being stuck on during operation nor a fault of switch SW1 being stuck on when it is off is detected.

[0107] Because the thermal time constant of the motor 3, which is the object of temperature measurement in this embodiment, is large, large temperature changes will not occur in a short period of time. On the other hand, as Figure 12 As described in the instructions, a significant temperature change is measured when switch SW1 changes from open to closed. This can be utilized if a short cycle is executed... Figure 13 The shown troubleshooting procedure for the on-off sticking fault can detect the fault because a large temperature change only occurs when switch SW1 becomes stuck in the on-off state.

[0108] As the fourth threshold, for example, the temperature change when switching switch SW1 from off to on can be pre-calculated for each measured temperature, and used according to the current measured temperature. Alternatively, as the fourth threshold, the minimum value among the pre-calculated temperature changes for each measured temperature when switching switch SW1 is switched can always be used. Furthermore, in this embodiment, the difference in measured temperatures is used to determine the on / off sticking fault of switch SW1, but the difference in measured voltage can also be used for the same fault determination.

[0109] The effects of this embodiment are as follows. As described above, if an open / closed fault or a closed / closed fault occurs in switch SW1, the temperature sensing element 32 may be mistakenly identified as faulty even though it is not faulty. In this embodiment, by diagnosing whether there is an open / closed fault or a closed / closed fault in switch SW1, and in the event that a fault is detected, the diagnostic process of the temperature sensing element 32 can be stopped afterward, thus preventing the temperature sensing element 32 from being mistakenly identified as faulty.

[0110] According to the fourth embodiment described above, the following effects can be obtained.

[0111] (7) When the temperature difference measured before and after switching the current through the switching unit is less than the third threshold, the diagnostic unit 217 ( Figure 11 If S352: No), it is determined that an abnormality of disconnection and adhesion has occurred in switch SW1. Therefore, the abnormality of disconnection and adhesion of switch SW1 can be detected.

[0112] (8) When the temperature difference measured by the diagnostic unit 217 within a certain period of time is greater than or equal to the 4th threshold, Figure 13 S372: Yes), indicating that an abnormality of connection sticking has occurred in switch SW1. Therefore, the abnormality of connection sticking in switch SW1 can be detected.

[0113] (9) The diagnostic unit 217 performs abnormality determination processing of the temperature measuring element 32 only if it determines that no abnormality has occurred in the switching unit (S302~S309). Therefore, it is possible to detect abnormalities in the temperature measuring element 32 after confirming that no abnormality of disconnection or connection of switch SW1 has occurred.

[0114] (A variation of the fourth embodiment)

[0115] In the fourth embodiment described above, the diagnostic unit 217 detects both the disconnection adhesion abnormality and the connection adhesion abnormality of the switch SW1. However, the diagnostic unit 217 may also detect only one of the disconnection adhesion abnormality and the connection adhesion abnormality of the switch SW1. In this case, the diagnostic unit 217 performs the abnormality determination processing of the temperature measuring element 32 (S302 to S309) only if no abnormality is detected in the detection of either the disconnection adhesion abnormality or the connection adhesion abnormality.

[0116] —Fifth Implementation—

[0117] Reference Figure 14 This describes a fifth embodiment of a power conversion device and drive device, also known as a temperature measuring device. In the following description, the same reference numerals are used for components identical to those in the first embodiment; the main differences are explained. Points not specifically described are the same as in the first embodiment. The main difference from the first embodiment lies in the correction of temperature during the diagnosis of the temperature measuring element 32.

[0118] Figure 14 This is a configuration diagram of the drive device 1 according to the fifth embodiment. In this embodiment, a diagnostic implementation signal from the diagnostic unit 217, a target current from the target current calculation unit 212, and a motor speed from the motor speed calculation unit 215 are further input to the motor temperature calculation unit 216. The motor temperature calculation unit 216 uses the diagnostic implementation signal, the target current, and the motor speed to correct the motor temperature. In this embodiment, the diagnostic unit 217 outputs a diagnostic implementation signal to the motor temperature calculation unit 216 during the diagnosis of the temperature measuring element 32.

[0119] When the diagnostic unit 217 does not perform a diagnostic test on the temperature measuring element 32, i.e., when no diagnostic test signal is received, the motor temperature calculation unit 216 outputs the measured temperature as is. When the diagnostic unit 217 performs a diagnostic test on the temperature measuring element 32, i.e., when a diagnostic test signal is received, the motor temperature calculation unit 216 adds a temperature correction value to the last measured motor temperature before the diagnostic test began and outputs it. The motor temperature calculation unit 216 calculates motor losses using the current target current and motor speed, and calculates the temperature correction value based on the motor losses.

[0120] The losses of motor 3 are divided into copper losses and iron losses. Copper losses can be calculated based on the winding resistance within motor 3 and the current flowing through motor 3. Iron losses vary depending on the current flowing through motor 3 and the motor speed. Since the current flowing through motor 3 follows a target current, the motor temperature calculation unit 216 calculates the copper losses of motor 3 based on pre-recorded winding resistance values ​​and the target current. Furthermore, information on iron losses corresponding to the current flowing through motor 3 and the motor speed is also pre-recorded. The motor temperature calculation unit 216 calculates the iron losses of motor 3 based on the iron loss information, the current target current, and the current motor speed. Then, the motor speed calculation unit 215 calculates the temperature rise of motor 3 due to the current motor operating conditions based on the copper losses, iron losses, and the pre-recorded thermal time constant of motor 3, as a temperature correction value. This example demonstrates using the target current as the current flowing through motor 3, but the AC current sensor value can also be used as the current flowing through motor 3.

[0121] The advantages of this embodiment are as follows. In the first embodiment, since the temperature measuring element 32 generates heat when current flows through it during diagnosis, the temperature of the motor 3, which is the object of temperature measurement, cannot be accurately measured. In this embodiment, during the diagnosis of the temperature measuring element 32, the measured temperature is added to a temperature correction value corresponding to the current motor operating condition to obtain the measured temperature just before diagnosis, and this value is used as the output temperature. Therefore, the temperature of the motor 3 can be measured more accurately even during diagnosis.

[0122] According to the fifth embodiment described above, the following effects can be obtained.

[0123] (10) The power conversion device 2 includes: a target current calculation unit 212 and a motor speed calculation unit 215, which acquire the rotational speed of the motor 3 and the current flowing through the motor 3; and a motor temperature calculation unit 216, which calculates a temperature correction value using the rotational speed and current value during the diagnostic process performed by the diagnostic unit 217, and outputs the measured temperature as the value obtained by adding the temperature correction value to the measured temperature just before the diagnostic process begins. Therefore, the temperature of the motor 3 can be measured more accurately even during diagnostics.

[0124] Furthermore, the present invention is not limited to the above embodiments and includes various modifications. For example, the above embodiments have been described in detail for ease of understanding and illustration of the present invention, and are not necessarily limited to having all the described configurations. In addition, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Furthermore, for a part of the configuration of each embodiment, other configurations can be added, deleted, or replaced.

[0125] Furthermore, the aforementioned components, functions, processing units, and processing organizations can also be implemented in hardware, for example, by designing some or all of them using integrated circuits. Alternatively, the aforementioned components and functions can be implemented in software by a processor interpreting and executing programs that perform their respective functions. The programs, tables, files, and other information implementing these functions can be stored in recording devices such as memory, hard disks, SSDs (Solid State Drives), or recording media such as IC cards, SD cards, and DVDs.

[0126] In the above embodiments and variations, the configuration of the functional blocks is merely one example. Several functional configurations represented by different functional blocks can be configured as a single unit, or the configuration represented by a single functional block diagram can be divided into two or more functions. Alternatively, other functional blocks can be configured to possess a portion of the functions of each functional block.

[0127] The above-described embodiments and modifications can also be combined separately. Various embodiments and modifications have been described above, but the present invention is not limited to these. Other methods that can be considered within the scope of the technical concept of the present invention are also included within the scope of the present invention.

[0128] Symbol Explanation

[0129] 1: Drive unit

[0130] 2: Power conversion device

[0131] 3: Motor

[0132] 21: Control Circuit

[0133] 22: Drive circuit

[0134] 23: Power Conversion Circuit

[0135] 26: Motor temperature detection circuit

[0136] 31: Motor Angle Sensor

[0137] 32: Temperature measuring element

[0138] 212: Target Current Calculation Section

[0139] 216: Motor Temperature Calculation Department

[0140] 217: Diagnostic Department

[0141] 2171: Normal Range Table.

Claims

1. A temperature measuring device for measuring the temperature of an object to be measured. The temperature measuring device is characterized by having: The switching unit changes the amount of current flowing through the temperature measuring element mounted on the object to be measured; and The diagnostic unit performs diagnostic processing, which determines that if, when the current flowing through the temperature measuring element is increased via the switching unit, the change in temperature measured by the temperature measuring element deviates from the normal range, the temperature measuring element is deemed to have malfunctioned. The normal range refers to the variable range corresponding to the value measured by the temperature measuring element.

2. The temperature measuring device according to claim 1, characterized in that, When the value measured by the temperature measuring element is less than the first threshold, the diagnostic unit controls the switching unit by increasing the current or the duration of the current applied to the temperature measuring element, compared to when the value measured by the temperature measuring element is greater than the first threshold.

3. The temperature measuring device according to claim 1, characterized in that, The object being measured is a motor. When the value measured by the temperature measuring element is less than the second threshold, the diagnostic unit allows current to flow through the motor; when the value measured by the temperature measuring element exceeds the second threshold, it determines the abnormality of the temperature measuring element.

4. The temperature measuring device according to claim 3, characterized in that, The diagnostic unit controls the current to be maximized when the torque output by the motor is within a certain range from the target value.

5. The temperature measuring device according to claim 1, characterized in that, If the difference between the values ​​measured by the temperature measuring element before and after the switching unit changes the current flowing through the temperature measuring element is less than a third threshold, the diagnostic unit determines that the switching unit has malfunctioned.

6. The temperature measuring device according to claim 1, characterized in that, If the temperature difference measured by the diagnostic unit within a certain period of time is above the fourth threshold, it is determined that the switching unit has malfunctioned.

7. The temperature measuring device according to claim 5, characterized in that, The diagnostic unit performs the diagnostic process only if it determines that no abnormality has occurred in the switching unit.

8. The temperature measuring device according to claim 6, characterized in that, The diagnostic unit performs the diagnostic process only if it determines that no abnormality has occurred in the switching unit.

9. The temperature measuring device according to claim 1, characterized in that, The object being measured is a motor. It also includes: a unit for acquiring the rotational speed of the motor and the current flowing through the motor; and The temperature calculation unit calculates a temperature correction value using the rotation speed and the current value during the diagnostic process performed by the diagnostic unit, and outputs the measured temperature obtained by adding the temperature correction value to the measured temperature just before the diagnostic process begins as the measured temperature.

10. A power conversion device, characterized in that... ， Includes the temperature measuring device as described in claim 1. It has a power conversion circuit that supplies power to the object being measured for temperature.

11. A driving device, characterized in that... ， Includes the temperature measuring device as described in claim 1. It includes a motor, which is the object of the temperature measurement.

12. A diagnostic method, performed by a temperature measuring device that measures the temperature of the object being measured. The diagnostic method is characterized by comprising: Switching processing changes the current flowing through the temperature-measuring element installed on the object being measured; and In the diagnostic process, if the change in temperature measured by the temperature measuring element deviates from the normal range when the current flowing through the temperature measuring element is increased through the switching process, the temperature measuring element is determined to be malfunctioning. The normal range refers to the variable range corresponding to the value measured by the temperature measuring element.

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