Drive unit

Abstract

In a drive system equipped with a motor, this technology can suppress excessive limitation of the motor's output torque, even when the ambient pressure of the coil is relatively low. [Solution] The drive device comprises a motor having a coil, a battery supplying power to the motor, an inverter provided between the battery and the motor which converts 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, which controls the operation of the inverter. The control device is configured to perform a torque limiting process that limits the maximum output torque of the motor when the ambient pressure of the motor falls below a predetermined pressure value. In the torque limiting process, the degree to which the maximum output torque is limited decreases as the DC voltage supplied to the inverter decreases.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a drive device including a motor, for example, a drive device for a vehicle.

Background Art

[0002] Patent Document 1 describes a drive device for a vehicle. This drive device includes a motor having a coil, a battery that supplies power to the motor, a boost converter that boosts the DC voltage supplied from the battery, an inverter that converts the DC power supplied from the boost converter into AC power to be supplied to the motor, a pressure sensor that detects air pressure, and a control device that is connected to the pressure sensor and executes a process of limiting the output voltage of the boost converter when the air pressure falls below a predetermined pressure value. Thereby, partial discharge occurring in the coil of the motor is suppressed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to avoid partial discharge occurring in the coil of the motor, it is necessary to maintain the voltage difference generated between the coil wires below the voltage at which partial discharge can start (hereinafter, partial discharge start voltage). It is known that the value of the partial discharge start voltage decreases as the ambient air pressure of the motor (accurately, the ambient air pressure of the coil) decreases. Therefore, in the drive device described in Patent Document 1, a pressure sensor is provided in the vehicle, and when the air pressure falls below a predetermined pressure value, the output voltage of the boost converter is configured to be limited.

[0005] However, the drive system may not have a boost converter. In this case, instead of limiting the output voltage of the boost converter, it is possible to limit the maximum output torque of the motor. The motor's output torque can be controlled by an inverter, and a boost converter is not necessarily required for this control. However, limiting the maximum output torque can worsen drivability, for example, in a vehicle.

[0006] In view of the above, this specification provides a technology that can suppress excessive limitation of the output torque of a motor in a drive device equipped with a motor, even when the ambient pressure of the coil is relatively low. [Means for solving the problem]

[0007] The technology disclosed herein is embodied in a drive device. This drive device includes a motor having coils, a battery supplying power to the motor, an inverter provided between the battery and the motor and converting the DC power supplied from the battery into AC power supplied to the motor, a pressure sensor for detecting the ambient pressure of the motor or an indicator correlated thereto, a voltage sensor for detecting the DC voltage supplied from the battery to the inverter or an indicator correlated thereto, and a control device connected to the pressure sensor and the voltage sensor and controlling the operation of the inverter. The control device is capable of performing a torque limiting process to limit the maximum output torque of the motor when the ambient pressure of the motor falls below a predetermined pressure value. In the torque limiting process, the degree to which the maximum output torque is limited decreases as the DC voltage supplied to the inverter decreases.

[0008] In the above configuration, when the ambient pressure of the motor falls below a predetermined pressure value, a torque limiting process is executed to limit the maximum torque. In this case, the degree to which the maximum output torque is limited can be reduced as the DC voltage supplied to the inverter (hereinafter referred to as the supply voltage to the inverter) decreases. For example, if the battery's SOC is relatively low, and as a result the supply voltage to the inverter is relatively low, the surge voltage generated in the coil can also be kept relatively low. In this case, the voltage difference between the coil wires will also be relatively low, so even if the ambient pressure of the coil falls below a predetermined pressure value, the occurrence of partial discharge will be relatively suppressed. Therefore, when the supply voltage to the inverter is low, the motor's output torque can be prevented from being excessively limited by reducing the degree to which the maximum output torque is limited. In this case, the degree to which the maximum output torque is limited (e.g., the limiting rate or limiting width) may be changed in stages or continuously according to the supply voltage to the inverter.

[0009] In one embodiment of this technology, the voltage sensor may be configured to detect the State of Charge (SOC) of the battery as an indicator correlated with the DC voltage supplied to the inverter. The DC voltage supplied to the inverter correlates with the output voltage of the battery, and the output voltage of the battery correlates with the SOC of the battery. Therefore, by detecting the SOC of the battery, the DC voltage supplied to the inverter can also be determined. Generally, the SOC of a battery 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 connected to the control device may further be provided, which detects the ambient temperature of the coil or an index correlated thereto. In this case, the torque limiting process may reduce the degree to which the maximum output torque is limited as the ambient temperature of the coil decreases.

[0011] According to the above configuration, in the torque limiting process, the degree to which the maximum output torque is limited can be reduced as the ambient temperature of the coil decreases. It is known that the value of the partial discharge initiation voltage increases as the ambient temperature of the coil decreases. Therefore, when the ambient temperature of the coil is low, the degree to which the maximum output torque is limited can be reduced to prevent the motor's output torque from being excessively limited. In this case, the degree to which the maximum output torque is limited (e.g., the limiting rate or limiting width) may be changed in steps or continuously depending on the ambient temperature of the coil.

[0012] In the above embodiment, the temperature sensor may be configured to detect the coil temperature as an indicator correlated with the ambient temperature of the coil. The ambient temperature of the coil correlates with the coil temperature. Therefore, by detecting the coil temperature, the ambient temperature of the coil can also be determined. In general, the coil temperature is monitored for purposes such as preventing the coil from overheating. By utilizing this information, the control device can easily detect the ambient temperature of the coil.

[0013] The technology disclosed herein is also embodied in the following drive device. This drive device comprises a motor having a coil, a battery supplying power to the motor, an inverter located between the battery and the motor that converts the DC power supplied from the battery into AC power supplied to the motor, a pressure sensor that detects the ambient pressure of the motor or an indicator correlated thereto, a temperature sensor that detects the ambient temperature of the coil or an indicator correlated thereto, and a control device connected to the pressure sensor and the temperature sensor, which controls the operation of the inverter. The control device is configured to perform a torque limiting process that limits the maximum output torque of the motor when the ambient pressure of the motor falls below a predetermined pressure value. In the torque limiting process, the degree to which the maximum output torque is limited decreases as the ambient temperature of the coil decreases.

[0014] In the above configuration, when the ambient pressure of the motor falls below a predetermined pressure value, a torque limiting process is executed to limit the maximum output torque. In this torque limiting process, the lower the ambient temperature of the coil, the more the maximum output torque is limited. As mentioned above, when the ambient temperature of the coil is low, reducing the degree to which the maximum output torque is limited can prevent the motor's output torque from being excessively limited. In this case, the degree to which the maximum output torque is limited (e.g., the limiting rate or limiting width) may be changed in steps or continuously depending on the ambient temperature of the coil. [Brief explanation of the drawing]

[0015] [Figure 1] This is a block diagram showing the configuration of the drive unit 10. [Figure 2] This flowchart shows an example of a series of first torque limiting processes performed by the drive unit 10 in the first embodiment. [Figure 3] This graph shows a torque limit map corresponding to the supply voltage used in the first torque limiting process. [Figure 4] This flowchart shows an example of a series of second torque limiting processes performed by the drive unit in the second embodiment. [Figure 5] This graph shows the torque limit map according to ambient temperature used in the second torque limiting process. [Modes for carrying out the invention]

[0016] (First embodiment) The drive unit 10 of the first embodiment will be described with reference to the drawings. The drive unit 10 is a drive unit for driving that is mounted on the electric vehicle 2. Although this is just one example, the electric vehicle 2 is a so-called battery electric vehicle (BEV). The configuration described in the first embodiment is not limited to battery electric vehicles and can be similarly adopted for other types of electric vehicles. Here, the term "electric vehicle" broadly refers to a vehicle that drives its wheels with a motor, and includes, for example, battery electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and fuel cell electric vehicles.

[0017] As shown in Figure 1, the electric vehicle 2 has a plurality of mechanical components (not shown) including a drive unit 10. The drive unit 10 comprises a motor 20, a battery 30, an inverter 40, and a control device 60. The battery 30 is a high-voltage battery. Here, high voltage means an operating voltage exceeding 60V DC. The battery 30 contains a plurality of secondary battery cells. The secondary battery cells may be, for example, lithium-ion cells or all-solid-state battery cells. The drive unit 10 also comprises a pressure sensor 50, a temperature sensor 52, a battery ECU (Electronic Control Unit) 32, and a control device 60.

[0018] The motor 20 is a device that drives the wheels (not shown) of the electric vehicle 2 using power supplied from the battery 30. The motor 20 is electrically connected to the battery 30 and mechanically connected to the wheels. The motor 20 comprises a plurality of coils 22. Although not particularly limited, the motor 20 is a three-phase AC motor and has a U-phase coil 22U, a V-phase coil 22V, and a W-phase coil 22W. The wheels driven by the motor 20 may be front wheels or rear wheels. In one example, in the electric vehicle 2 of this embodiment, the motor 20 is connected to a pair of front wheels via a reduction gear and a differential. In another embodiment, the motor 20 may be a so-called in-wheel motor. In this case, the electric vehicle 2 can be equipped with a plurality of motors 20 depending on the number of drive wheels.

[0019] The inverter 40 is installed between the battery 30 and the motor 20 and is electrically connected to each of the battery 30 and the motor 20. The inverter 40 converts the DC power supplied from the battery 30 into AC power supplied to the motor 20. The inverter 40 can control the magnitude and direction of the output torque of the motor 20.

[0020] The air pressure sensor 50 is installed inside the electric vehicle 2. The specific configuration of the air pressure sensor 50 is not particularly limited. For example, the air pressure sensor 50 may be installed outside the electric vehicle 2 and configured to be communicable with the electric vehicle 2. The air pressure sensor 50 detects the atmospheric pressure of the motor 20. Specifically, the air pressure sensor 50 detects the air pressure around the motor 20. The control device 60 can calculate the approximate altitude of the location where the electric vehicle 2 is traveling based on the pressure value detected by the air pressure sensor 50.

[0021] The temperature sensor 52 is installed adjacent to a part (not shown) of the coil ends of the plurality of coils 22 of the motor 20. The temperature sensor 52 detects the ambient temperature of the plurality of coils 22. Specifically, the temperature sensor 52 detects the temperature of a part of the coil ends of the plurality of coils 22. When the motor 20 is driven, the temperature of the entire plurality of coils 22 rises relatively uniformly. Therefore, the control device 60 can monitor the temperature of the entire plurality of coils 22 by detecting the temperature of a part of the coil ends of the plurality of coils 22.

[0022] The battery ECU 32 is arranged 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 SOC (State Of Charge) of the battery 30 based on the current of the battery 30 (charging current and discharging current). When the temperature of the battery 30 rises above a predetermined temperature, the battery ECU 32 can suppress the 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 of the drive device 10 and monitors the SOC and voltage of the battery 30.

[0023] The control device 60 is arranged inside the electric vehicle 2. The control device 60 is electrically connected to the pressure sensor 50, the temperature sensor 52, and the 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 an output torque command from a higher-level ECU (not shown). The control device 60 in this embodiment is configured to be able to execute a first torque limit process for limiting the maximum value of the output torque of the motor 20 when the atmospheric pressure of the motor 20 falls below a predetermined pressure value. The specific content of the first torque limit process will be described below with reference to FIGS. 2 and 3.

[0024] When the electric vehicle 2 is powered on, it repeatedly executes a series of processes shown in FIG. 2. First, the control device 60 determines whether the pressure value taught by the pressure sensor 50 (the atmospheric pressure of the motor 20) is less than a predetermined pressure value (S10). If the pressure value taught by the pressure sensor 50 is less than the predetermined pressure value (S10: Yes), the control device 60 starts the first torque limit process (S12). If the pressure value taught by the pressure sensor 50 is greater than or equal to the predetermined pressure value (S10: No), the control device 60 returns to the process of S10. That is, the control device 60 repeatedly executes the determination of S10 and is configured to start the first torque limit process when the pressure value taught by the pressure sensor 50 becomes less than the predetermined pressure value.

[0025] When 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. Subsequently, the control device 60 selects a torque limiting map according to the detected supply voltage value to the inverter 40 (S16). As shown in Figure 3, in the torque limiting map selected in this step S16, a torque limit is set at altitudes of 2000m or higher, and the torque limiting rate is set to increase as the supply voltage value increases. That is, by setting a larger torque limiting rate when the supply voltage value is high, the voltage difference between the wires of the multiple coils 22 can be kept below the partial discharge start voltage. In other words, the smaller the supply voltage to the inverter 40, the less the limit on the maximum output torque of the motor 20 can be reduced. Then, the control device 60 controls the output torque of the motor 20 with a limiting ratio corresponding to the torque limiting map selected in step S16 and the ambient pressure (altitude) detected in step S10 (S18). After performing this process, the control device 60 proceeds to the process in step S20.

[0026] In step S20, the control device 60 determines whether the pressure value indicated by the barometric pressure sensor 50 is equal to or greater than a predetermined pressure value. If the pressure value indicated by the barometric pressure sensor 50 is equal to or greater than the predetermined pressure value (S20: Yes), the control device 60 terminates the first torque limiting process. That is, if the pressure value indicated by the barometric pressure sensor 50 (ambient pressure of the motor 20) becomes equal to or greater than the predetermined pressure value while the first torque limiting process is being executed, the control device 60 determines that the altitude of the location where the electric vehicle 2 is traveling has become relatively low and terminates the execution of the first torque limiting process.

[0027] In step S20, if the pressure value taught by the pressure sensor 50 is less than a predetermined pressure value (S20: No), the control device 60 returns to step S12 and continues to execute the first torque limiting process.

[0028] As described above, in the drive unit 10 of this embodiment, when the ambient pressure of the motor 20 falls below a predetermined pressure value, a torque limiting process is performed to limit the maximum torque. In this case, the torque limiting process can reduce the degree to which the maximum output torque is limited (here, the torque limiting rate) as the DC voltage supplied to the inverter 40 (hereinafter referred to as the supply voltage to the inverter) decreases.

[0029] For example, if the State of Charge (SOC) of the battery 30 is relatively low, and as a result the supply voltage to the inverter 40 is relatively low, the surge voltage generated in the coil 22 will also be kept relatively low. In this case, the voltage difference between the coil wires will also be relatively low, so even if the ambient pressure of the coil 22 falls below a predetermined pressure value, the occurrence of partial discharge will be relatively suppressed. Therefore, when the supply voltage to the inverter 40 is low, the output torque of the motor 20 can be prevented from being excessively limited by reducing the degree to which the maximum output torque is limited. At this time, the degree to which the maximum output torque is limited (for example, the limiting rate or limiting width) may be changed in steps or continuously according to the supply voltage to the inverter 40.

[0030] (Second example) The drive unit of the second embodiment will be described with reference to Figures 4 and 5. Compared to the drive unit 10 of the first embodiment, the drive unit of this embodiment has a modified content for the torque limiting process performed by the control device 60. That is, the control device 60 in this embodiment is configured to perform the series of processes shown in Figure 4 instead of the series of processes shown in Figure 2. In other respects, the drive unit of this embodiment has the same configuration as the drive unit 10 of the first embodiment shown in Figure 1. That is, the drive unit of this embodiment also comprises a motor 20, a battery 30, an inverter 40, and a control device 60 (see Figure 1). The configuration and functions of these are as described in the first embodiment, and will not be described again here.

[0031] In the drive system of this embodiment, when the power to the electric vehicle 2 is turned on, the control device 60 repeatedly executes the series of processes shown in Figure 4. First, the control device 60 determines whether the pressure value (ambient pressure of the motor 20) indicated by the barometric pressure sensor 50 is less than a predetermined pressure value (S30). If the pressure value indicated by the barometric pressure sensor 50 is less than the predetermined pressure value (S30: Yes), the control device 60 starts the second torque limiting process (S32). If the pressure value indicated by the barometric pressure sensor 50 is equal to or greater than the predetermined pressure value (S30: No), the control device 60 returns to the process of S30. In other words, the control device 60 is configured to repeatedly execute the determination in S30 and start the second torque limiting process when the pressure value indicated by the barometric pressure sensor 50 falls below the predetermined pressure value.

[0032] When the second torque limiting process is initiated (S32), the control device 60 obtains the detected ambient temperature of the multiple coils 22 from the temperature sensor 52 (S34). Subsequently, the control device 60 selects an output torque limiting map corresponding to the ambient temperature of the multiple coils 22 (S36). As shown in Figure 5, in the torque limiting map selected in step S36, a torque limit is set at altitudes of 2000m or higher, and the torque limiting rate increases as the ambient temperature increases. In other words, the lower the ambient temperature of the multiple coils 22, the less the maximum output torque of the motor 20 is limited. Then, the control device 60 controls the output torque of the motor 20 with a limiting rate corresponding to the torque limiting map selected in step S36 and the ambient pressure (altitude) detected in step S30 (S38). After executing the process in step S38, the control device 60 proceeds to the process in step S40.

[0033] In step S40, the control device 60 determines whether the pressure value indicated by the barometric pressure sensor 50 is equal to or greater than a predetermined pressure value. If the pressure value indicated by the barometric pressure sensor 50 is equal to or greater than the predetermined pressure value (S40: Yes), the control device 60 terminates the second torque limiting process. That is, if the pressure value indicated by the barometric pressure sensor 50 (ambient pressure of the motor 20) becomes equal to or greater than the predetermined pressure value while the control device 60 is executing the second torque limiting process, it determines that the altitude of the location where the electric vehicle 2 is traveling has become relatively low and terminates the execution of the second torque limiting process.

[0034] In step S40, if the pressure value taught by the pressure sensor 50 is less than a predetermined pressure value (S20: No), the control device 60 returns to step S32 and continues to execute the second torque limiting process.

[0035] As described above, in the drive device of this embodiment, when the ambient pressure of the motor 20 falls below a predetermined pressure value, a torque limiting process is performed to limit the maximum output torque. In this case, the lower the ambient temperature of the coil, the more the torque limiting process can be reduced to limit the maximum output torque (in this case, the torque limiting rate).

[0036] It is known that the partial discharge initiation voltage increases as the ambient temperature of the coil 22 decreases. Therefore, when the ambient temperature of the coil 22 is low, the output torque of the motor 20 can be prevented from being excessively limited by reducing the degree to which the maximum output torque is limited. In this case, the degree to which the maximum output torque is limited (e.g., the limiting rate or limiting width) may be changed in steps or continuously depending on the ambient temperature of the coil 22.

[0037] Furthermore, the torque limiting process described in the second embodiment can be used in combination with the torque limiting process described in the first embodiment. That is, in the third embodiment, the control device 60 may have both the torque limiting map shown in Figure 3 and the torque limiting map shown in Figure 5.

[0038] Furthermore, in a further embodiment of this design, a boost converter may be connected between the battery 30 and the inverter 40. In such a configuration, the control device 60 may be configured to detect the boosted value of the boost converter. This allows the control device 60 to monitor the power supplied to the motor 20 based on the boosted value of the boost converter.

[0039] The specific examples of the technology disclosed in this specification have been described in detail above, but these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples described above. The technical elements described in this specification or drawings exhibit technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving even one of these objectives itself constitutes technical usefulness. [Explanation of Symbols]

[0040] 2: Electric vehicle, 10: Drive unit, 20: Motor, 22: Multiple coils, 30: Battery, 32: Battery ECU, 40: Inverter, 50: Barometric pressure sensor, 52: Temperature sensor, 60: Control unit

Claims

1. A motor having a coil, A battery that supplies power to the motor, An inverter is provided between the battery and the motor, which converts the DC power supplied from the battery into AC power supplied to the motor. A pressure sensor for detecting the ambient pressure of the motor or an indicator correlated thereto, A voltage sensor that detects the DC voltage supplied from the battery to the inverter or an indicator correlated thereto, A control device connected to the aforementioned pressure sensor and voltage sensor, which controls the operation of the inverter, Equipped with, The control device is configured to perform torque limiting processing to limit the maximum output torque of the motor when the ambient pressure of the motor falls below a predetermined pressure value. In the torque limiting process, the degree to which the maximum value of the output torque is limited decreases as the DC voltage supplied to the inverter decreases. Drive unit.

2. The drive device according to claim 1, wherein the voltage sensor is configured to detect the State of Charge (SOC) of the battery as an indicator correlated with the DC voltage supplied to the inverter.

3. The control device is connected to a temperature sensor that detects the ambient temperature of the coil or an index correlated thereto, The drive device according to claim 1, wherein the torque limiting process reduces the degree to which the maximum value of the output torque is limited as the ambient temperature of the coil decreases.

4. The drive device according to claim 3, wherein the temperature sensor is configured to detect the temperature of the coil as an index correlated with the ambient temperature of the coil.

5. A motor having a coil, A battery that supplies power to the motor, An inverter is provided between the battery and the motor, which converts the DC power supplied from the battery into AC power supplied to the motor. A pressure sensor for detecting the ambient pressure of the motor or an indicator correlated thereto, A temperature sensor for detecting the ambient temperature of the coil or an index correlated thereto, A control device connected to the aforementioned pressure sensor and temperature sensor, which controls the operation of the inverter, Equipped with, The control device is configured to perform torque limiting processing to limit the maximum output torque of the motor when the ambient pressure of the motor falls below a predetermined pressure value. In the torque limiting process, the degree to which the maximum value of the output torque is limited is reduced as the ambient temperature of the coil decreases. Drive unit.

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