drive device

Abstract

This invention provides a technique for preventing excessive limitation of the output torque of a motor in a drive device equipped with an electric motor, even when the ambient pressure of the coil is relatively low. The drive device includes: an electric motor having a coil; a battery supplying power to the motor; an inverter disposed between the battery and the motor, converting the DC power supplied from the battery into AC power supplied to the motor; a pressure sensor; a voltage sensor; and a control device connected to the pressure sensor and the voltage sensor, controlling the operation of the inverter. The control device is configured to perform torque limiting processing, which limits the maximum output torque of the motor when the ambient pressure of the motor is below a predetermined pressure value. In the torque limiting processing, the lower the DC voltage supplied to the inverter, the less severe the limitation on the maximum output torque.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a drive device with an electric motor, for example, to a drive device for a vehicle. Background Technology

[0002] Patent Document 1 describes a drive system for a vehicle. This drive system includes: an electric motor having coils; a battery supplying power to the electric motor; a boost converter boosting the DC voltage supplied from the battery; an inverter converting the DC power supplied from the boost converter into AC power supplied to the electric motor; a pressure sensor detecting air pressure; and a control device connected to the pressure sensor, which performs a process to limit the output voltage of the boost converter when the air pressure is lower than a predetermined pressure value. This suppresses partial discharge in the coils of the electric motor.

[0003] Patent Document 1: Japanese Patent No. 6740892 Summary of the Invention

[0004] To prevent partial discharge in the motor coils, the voltage difference between the coil wires needs to be maintained below the voltage at which partial discharge can begin (hereinafter referred to as the partial discharge initiation voltage). It is known that the lower the ambient pressure of the motor (more precisely, the ambient pressure of the coils), the lower the partial discharge initiation voltage. Therefore, in the drive device described in Patent Document 1, a pressure sensor is installed on the vehicle to limit the output voltage of the boost converter when the air pressure is below a specified pressure value.

[0005] However, drive units sometimes lack a boost converter. In such cases, limiting the maximum output torque of the electric motor is considered instead of limiting the output voltage of the boost converter. The output torque of the electric motor can be controlled by an inverter, which does not necessarily require a boost converter. However, limiting the maximum output torque, for example in a vehicle, can degrade driving performance.

[0006] In view of the above, this specification provides a technique that, in a drive device equipped with an electric motor, can prevent the output torque of the electric motor from being excessively limited, even when the ambient pressure of the coil is relatively low.

[0007] The technology disclosed in this specification is embodied in a drive device. This drive device includes: an electric motor having coils; a battery supplying power to the electric motor; an inverter disposed between the battery and the electric motor, converting the DC power supplied from the battery into AC power supplied to the electric motor; a barometric pressure sensor detecting the ambient pressure of the electric motor or related parameters; a voltage sensor detecting the DC voltage supplied from the battery to the inverter or related parameters; and a control device connected to the barometric pressure sensor and the voltage sensor, controlling the operation of the inverter. The control device is capable of performing torque limiting processing, which limits the maximum output torque of the electric motor when the ambient pressure of the electric motor is lower than a specified pressure value. In the torque limiting processing, the lower the DC voltage supplied to the inverter, the less restrictive the maximum output torque is.

[0008] In the above structure, if the ambient pressure of the motor is lower than a specified pressure value, a torque limiting process is performed to restrict the maximum torque. In this torque limiting process, the lower the DC voltage supplied to the inverter (hereinafter, the supply voltage to the inverter), the less restrictive the maximum output torque becomes. For example, if the battery's SOC is relatively low, resulting in a lower supply voltage to the inverter, surge voltages generated in the coils are also suppressed relatively. In this case, since the voltage difference between the coil lines is also relatively low, partial discharge is relatively suppressed even if the ambient pressure of the coils is lower than the specified pressure value. Therefore, when the supply voltage to the inverter is low, by reducing the degree of restriction on the maximum output torque, excessive restriction on the motor's output torque can be prevented. The degree of restriction on the maximum output torque (e.g., the restriction rate or restriction width) can be changed periodically or continuously depending on the supply voltage to the inverter.

[0009] In one embodiment of this technology, the voltage sensor can be configured to detect the battery's State of Charge (SOC) as an indicator related to the DC voltage supplied to the inverter. The DC voltage supplied to the inverter is related to the battery's output voltage, which in turn is related to the battery's SOC. Therefore, by detecting the battery's SOC, the DC voltage supplied to the inverter can also be determined. Typically, the battery's SOC is monitored for purposes such as battery protection. By utilizing this information, the control device can easily detect the DC voltage supplied to the inverter.

[0010] In one embodiment of this technology, a temperature sensor may be further included, connected to the control device, to detect the ambient temperature of the coil or related parameters. In this case, during torque limiting processing, the lower the ambient temperature of the coil, the less restrictive the maximum output torque can be.

[0011] Based on the above structure, in torque limiting processing, the lower the ambient temperature of the coil, the less restrictive the maximum output torque can be. It is known that the partial discharge initiation voltage increases with lower ambient temperature of the coil. Therefore, when the ambient temperature of the coil is low, by reducing the restriction on the maximum output torque, excessive restriction on the motor's output torque can be suppressed. In this case, the restriction on the maximum output torque (e.g., the restriction rate or restriction width) can be changed periodically or continuously according to the ambient temperature of the coil.

[0012] In the above embodiment, the temperature sensor can be configured to detect the temperature of the coil as an indicator related to the ambient temperature of the coil. The ambient temperature of the coil is related to the temperature of the coil. Therefore, by detecting the temperature of the coil, the ambient temperature of the coil can also be determined. Typically, the temperature of the coil is monitored, for example, to prevent the coil from overheating. By utilizing this information, the control device can easily detect the ambient temperature of the coil.

[0013] The technology disclosed in this specification is also embodied in the following drive device. This drive device includes: an electric motor having a coil; a battery supplying power to the electric motor; an inverter disposed between the battery and the electric motor, converting the DC power supplied from the battery into AC power supplied to the electric motor; a pressure sensor detecting the ambient pressure of the electric motor or related parameters; a temperature sensor detecting the ambient temperature of the coil or related parameters; and a control device connected to the pressure sensor and the temperature sensor, controlling the operation of the inverter. The control device is configured to perform torque limiting processing that limits the maximum output torque of the electric motor when the ambient pressure of the electric motor is lower than a specified pressure value. In the torque limiting processing, the lower the ambient temperature of the coil, the less restrictive the maximum output torque becomes.

[0014] In the above structure, if the ambient pressure of the motor is lower than a specified pressure value, a torque limiting process is performed to restrict the maximum output torque. In this torque limiting process, the lower the ambient temperature of the coil, the less restrictive the maximum output torque can be. As described above, when the ambient temperature of the coil is low, by reducing the restriction on the maximum output torque, excessive restriction on the motor's output torque can be prevented. The restriction level (e.g., restriction rate or restriction width) on the maximum output torque can be changed periodically or continuously according to the ambient temperature of the coil. Attached Figure Description

[0015] Figure 1 This is a block diagram showing the structure of the drive device 10.

[0016] Figure 2 This is a flowchart illustrating an example of a series of first torque limiting processes performed by the drive device 10 in the first embodiment.

[0017] Figure 3 It is a graph showing the torque limit mapping corresponding to the supply voltage used in the first torque limit process.

[0018] Figure 4 This is a flowchart illustrating an example of a series of second torque limiting processes performed by the drive device in the second embodiment.

[0019] Figure 5 It is a graph showing the torque limit mapping corresponding to the ambient temperature used in the second torque limit process. Detailed Implementation

[0020] (First embodiment)

[0021] Referring to the accompanying drawings, the drive unit 10 of the first embodiment will be described. The drive unit 10 is a driving drive unit mounted on the electric vehicle 2. Although it is an example, the electric vehicle 2 is a so-called battery electric vehicle (BEV). In addition, the structure described in the first embodiment is not limited to battery electric vehicles, and can also be used in the same way for other types of electric vehicles. The term "electric vehicle" here refers broadly to a vehicle that drives its wheels by an electric motor, including, for example, battery electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and fuel cell electric vehicles.

[0022] like Figure 1 As shown, the electric vehicle 2 has multiple mechanical structures including a drive unit 10 (illustrations omitted). The drive unit 10 includes an electric motor 20, a battery 30, an inverter 40, and a control unit 60. The battery 30 is a high-voltage battery. Here, "high voltage" refers to an operating voltage exceeding 60V DC. The battery 30 contains multiple secondary battery cells. These secondary battery cells can be, for example, lithium-ion cells or all-solid-state battery cells. Furthermore, the drive unit 10 includes a pressure sensor 50, a temperature sensor 52, a battery electronic control unit (ECU) 32, and the control unit 60.

[0023] The electric motor 20 is a device that drives the wheels (not shown) of the electric vehicle 2 by means of power supplied from the battery 30. The electric motor 20 is electrically connected to the battery 30 and mechanically connected to the wheels. The electric motor 20 has multiple coils 22. Although not particularly limited, the electric motor 20 is a three-phase AC motor with a U-phase coil 22U, a V-phase coil 22V, and a W-phase coil 22W. The wheels driven by the electric motor 20 can be either the front wheels or the rear wheels. Although one example, in this embodiment of the electric vehicle 2, the electric motor 20 is connected to a pair of front wheels via a reducer and a differential device. Alternatively, as another embodiment, the electric motor 20 can be a so-called hub motor. In this case, the electric vehicle 2 can have multiple electric motors 20 depending on the number of drive wheels.

[0024] Inverter 40 is positioned between battery 30 and motor 20, and is electrically connected to both. Inverter 40 converts the DC power supplied from battery 30 into AC power supplied to motor 20. Inverter 40 can control the magnitude and direction of the output torque of motor 20.

[0025] A pressure sensor 50 is installed inside the electric vehicle 2. The specific structure of the pressure sensor 50 is not particularly limited. For example, the pressure sensor 50 can be installed outside the electric vehicle 2 and configured to communicate with it. The pressure sensor 50 detects the ambient pressure of the electric motor 20. Specifically, the pressure sensor 50 detects the air pressure around the electric motor 20. The control device 60 can calculate the approximate elevation of the position where the electric vehicle 2 is traveling based on the pressure value detected by the pressure sensor 50.

[0026] Temperature sensor 52 is disposed adjacent to a portion (not shown) of the coil ends of the plurality of coils 22 of motor 20. Temperature sensor 52 detects the ambient temperature of the plurality of coils 22. Specifically, temperature sensor 52 detects the temperature of a portion of the coil ends of the plurality of coils 22. When motor 20 is driven, the overall temperature of the plurality of coils 22 rises relatively uniformly. Therefore, control device 60 can monitor the overall temperature of the plurality of coils 22 by detecting the temperature of a portion of the coil ends of the plurality of coils 22.

[0027] The battery ECU 32 is configured adjacent to the battery 30. The battery ECU 32 monitors the voltage, current, and temperature of the battery 30. The battery ECU 32 can calculate the state of charge (SOC) of the battery 30 based on the current (charging current and discharging current) of the battery 30. If the temperature of the battery 30 rises above a predetermined temperature, the battery ECU 32 can suppress overheating of the battery 30 by limiting the current of the battery 30. In this embodiment, the battery ECU 32 functions as a voltage sensor for the drive device 10 and monitors the SOC and voltage of the battery 30.

[0028] A control device 60 is disposed inside the electric vehicle 2. The control device 60 is electrically connected to the pressure sensor 50, temperature sensor 52, and battery ECU 32, and controls the operation of the inverter 40. The control device 60 controls the power supplied from the inverter 40 to the motor 20 based on the output torque command from a higher-level ECU (not shown). In this embodiment, the control device 60 is configured to perform a first torque limiting process that limits the maximum output torque of the motor 20 when the ambient pressure of the motor 20 is lower than a specified pressure value. For details of the first torque limiting process, please refer to [reference needed]. Figure 2 , 3 The following explanation will be provided.

[0029] If power is supplied to electric vehicle 2, the process will be repeated. Figure 2 The process described is as follows: First, the control device 60 determines whether the pressure value indicated by the pressure sensor 50 (the ambient pressure of the motor 20) is less than a specified pressure value (S10). If the pressure value indicated by the pressure sensor 50 is less than the specified pressure value (S10: Yes), the control device 60 begins the first torque limiting process (S12). If the pressure value indicated by the pressure sensor 50 is greater than or equal to the specified pressure value (S10: No), the control device 60 returns to the process in S10. That is, the control device 60 is configured to repeatedly execute the determination in S10, and begin the first torque limiting process when the pressure value indicated by the pressure sensor 50 is less than the specified pressure value.

[0030] If the first torque limiting process is initiated (S12), the control device 60 detects the DC voltage (supply voltage) supplied from the battery 30 to the inverter 40 (S14). In this embodiment, the supply voltage from the battery 30 to the inverter 40 is equal to the voltage of the battery 30 detected by the battery ECU 32. Therefore, the control device 60 obtains the voltage of the battery 30 detected by the battery ECU 32 as the supply voltage from the battery 30 to the inverter 40. Next, the control device 60 selects a torque limiting map based on the detected supply voltage value to the inverter 40 (S16). Figure 3As shown, in the torque limitation map selected in step S16, torque limitation is set above an elevation of 2000m, and the torque limitation rate is set to be greater the higher the supply voltage value. That is, the higher the supply voltage value, the greater the torque limitation rate is set, thereby maintaining the voltage difference generated between the lines of the multiple coils 22 below the partial discharge initiation voltage. In other words, the lower the supply voltage supplied to the inverter 40, the less the limitation on the maximum value of the output torque of the motor 20 can be. Then, the control device 60 controls the output torque of the motor 20 with a limitation rate corresponding to the torque limitation map selected in step S16 and the ambient pressure (elevation) detected in step S10 (S18). After performing this process, the control device 60 proceeds to the process of step S20.

[0031] In step S20, the control device 60 determines whether the pressure value indicated by the pressure sensor 50 is above a predetermined pressure value. If the pressure value indicated by the pressure sensor 50 is above the predetermined pressure value (S20: Yes), the control device 60 terminates the first torque limiting process. That is, during the execution of the first torque limiting process, if the pressure value indicated by the pressure sensor 50 (ambient pressure of the motor 20) becomes above the predetermined pressure value, the control device 60 determines that the elevation of the position where the electric vehicle 2 is traveling has become relatively low, thereby terminating the execution of the first torque limiting process (S22).

[0032] In the process of step S20, if the pressure value indicated by the pressure sensor 50 is less than the specified pressure value (S20: No), the control device 60 returns to the process of S12 and continues to execute the first torque limiting process.

[0033] As described above, in the drive device 10 of this embodiment, if the ambient pressure of the motor 20 is lower than a specified pressure value, a torque limiting process is performed to limit the maximum value of the torque. In this torque limiting process, the lower the DC voltage supplied to the inverter 40 (hereinafter, the supply voltage to the inverter), the smaller the degree of limitation on the maximum value of the output torque (here, the torque limiting rate).

[0034] For example, if the SOC of battery 30 is relatively low, resulting in a relatively low supply voltage to inverter 40, surge voltages generated in coil 22 are also relatively suppressed. In this case, since the voltage difference between the coil lines also becomes relatively low, partial discharge is relatively suppressed even if the ambient pressure of coil 22 is lower than a specified pressure value. Therefore, when the supply voltage to inverter 40 is low, excessive restriction on the output torque of motor 20 can be prevented by reducing the degree of restriction on the maximum output torque. At this time, the degree of restriction on the maximum output torque (e.g., restriction rate or restriction width) can be changed in stages or continuously depending on the supply voltage to inverter 40.

[0035] (Second Embodiment)

[0036] refer to Figure 4 , Figure 5 The drive device of the second embodiment will now be described. Compared with the drive device 10 of the first embodiment, the torque limiting process performed by the control device 60 in this embodiment has been changed. That is, the control device 60 in this embodiment is configured to perform... Figure 4 The series of processes shown replace Figure 2 The series of processes shown. Regarding other points, the drive device of this embodiment has the same... Figure 1 The drive device 10 shown in the first embodiment has the same structure. That is, the drive device in this embodiment also includes a motor 20, a battery 30, an inverter 40, and a control device 60 (see reference). Figure 1 Regarding these structures and functions, as described in the first embodiment, we will avoid repeating them here.

[0037] In the drive device of this embodiment, if power is supplied to the electric vehicle 2, the control device 60 repeats the operation. Figure 4 The process described is as follows: First, the control device 60 determines whether the pressure value indicated by the pressure sensor 50 (the ambient pressure of the motor 20) is less than a specified pressure value (S30). If the pressure value indicated by the pressure sensor 50 is less than the specified pressure value (S30: Yes), the control device 60 begins the second torque limiting process (S32). If the pressure value indicated by the pressure sensor 50 is greater than or equal to the specified pressure value (S30: No), the control device 60 returns to the process in S30. That is, the control device 60 is configured to repeatedly execute the determination in S30, and begin the second torque limiting process when the pressure value indicated by the pressure sensor 50 is less than the specified pressure value.

[0038] If the second torque limiting process is initiated (S32), the control device 60 acquires the detected values ​​of the ambient temperature of the multiple coils 22 from the temperature sensor 52 (S34). Next, the control device 60 selects an output torque limiting map corresponding to the ambient temperature of the multiple coils 22 (S36). Figure 5 As shown, in the torque limitation map selected in step S36, torque limitations are set above an elevation of 2000m, and the torque limitation rate is set to increase with higher ambient temperature. In other words, the lower the ambient temperature of the multiple coils 22, the less restrictive the maximum output torque of the motor 20. Then, the control device 60 controls the output torque of the motor 20 with a limitation rate corresponding to the torque limitation map selected in step S36 and the ambient pressure (elevation) detected in step S30 (S38). After executing the processing in step S38, the control device 60 proceeds to the processing in step S40.

[0039] In step S40, the control device 60 determines whether the pressure value indicated by the pressure sensor 50 is above a predetermined pressure value. If the pressure value indicated by the pressure sensor 50 is above the predetermined pressure value (S40: Yes), the control device 60 terminates the second torque limiting process. That is, during the execution of the second torque limiting process, if the pressure value indicated by the pressure sensor 50 (ambient pressure of the motor 20) becomes above the predetermined pressure value, the control device 60 determines that the elevation of the position where the electric vehicle 2 is traveling has become relatively low, thereby terminating the execution of the second torque limiting process (S42).

[0040] In the process of step S40, if the pressure value indicated by the pressure sensor 50 is less than the specified pressure value (S40: No), the control device 60 returns to the process of S32 and continues to execute the second torque limiting process.

[0041] As described above, in the drive device of this embodiment, if the ambient pressure of the motor 20 is lower than a specified pressure value, a torque limiting process is performed to limit the maximum value of the output torque. In this torque limiting process, the lower the ambient temperature of the coil, the smaller the degree of limitation on the maximum value of the output torque (here, the torque limiting rate).

[0042] It is known that the lower the ambient temperature of coil 22, the higher its value. Therefore, when the ambient temperature of coil 22 is low, by reducing the degree of restriction on the maximum value of the output torque, it is possible to suppress excessive restriction on the output torque of motor 20. At this time, the degree of restriction on the maximum value of the output torque (e.g., restriction rate or restriction width) can be changed in stages or continuously according to the ambient temperature of coil 22.

[0043] Furthermore, the torque limiting process described in the second embodiment can also be combined with the torque limiting process described in the first embodiment. That is, as a third embodiment, the control device 60 can simultaneously possess... Figure 3 The torque limiting map shown and Figure 5 The torque limiting mapping diagram is shown.

[0044] Furthermore, as a further embodiment of this invention, a boost converter can be connected between the battery 30 and the inverter 40. In this configuration, the control device 60 can be configured to detect the boost value of the boost converter. Thus, the control device 60 can monitor the power supply to the motor 20 based on the boost value of the boost converter.

[0045] The above provides a detailed description of specific examples of the technology disclosed in this specification. However, these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples illustrated above. The technical elements described in this specification or drawings exert their technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of application. Furthermore, the technology illustrated in this specification or drawings can achieve multiple objectives simultaneously, wherein achieving one objective is itself technically useful.

[0046] Symbol Explanation

[0047] 2-Electric vehicle, 10-Drive unit, 20-Motor, 22-Multiple coils, 30-Battery, 32-Battery ECU, 40-Inverter, 50-Pressure sensor, 52-Temperature sensor, 60-Control device.

Claims

1. A driving device, characterized in that, have: An electric motor, which has a coil; A battery that supplies power to the electric motor; An inverter is disposed between the battery and the motor, and converts the DC power supplied from the battery into AC power supplied to the motor; A barometric pressure sensor that detects the ambient pressure of the electric motor or related indicators; A voltage sensor that detects the DC voltage supplied from the battery to the inverter or related parameters; and A control device, connected to the pressure sensor and the voltage sensor, controls the operation of the inverter. The control device is configured to perform torque limiting processing that limits the maximum output torque of the motor when the ambient pressure of the motor is lower than a specified pressure value. In the torque limiting process, the lower the DC voltage supplied to the inverter, the less restrictive the maximum value of the output torque.

2. The driving device according to claim 1, characterized in that, The voltage sensor is configured to detect the state of charge (SOC) of the battery as an indicator related to the DC voltage supplied to the inverter.

3. The driving device according to claim 1, characterized in that, It also has: A temperature sensor, connected to the control device, detects the ambient temperature of the coil or related parameters. In the torque limiting process, the lower the ambient temperature of the coil, the less restrictive the maximum value of the output torque.

4. The driving device according to claim 3, characterized in that, The temperature sensor is configured to detect the temperature of the coil as an indicator related to the ambient temperature of the coil.

5. A driving device, characterized in that, have: An electric motor, which has a coil; A battery that supplies power to the electric motor; An inverter is disposed between the battery and the motor, and converts the DC power supplied from the battery into AC power supplied to the motor; A barometric pressure sensor that detects the ambient pressure of the electric motor or related indicators; A temperature sensor that detects the ambient temperature of the coil or related parameters; and A control device, connected to the pressure sensor and the temperature sensor, controls the operation of the inverter. The control device is configured to perform torque limiting processing that limits the maximum output torque of the motor when the ambient pressure of the motor is lower than a specified pressure value. In the torque limiting process, the lower the ambient temperature of the coil, the less restrictive the maximum value of the output torque.

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