WO2020066184A1

WO2020066184A1 - Driving control device, driving device, and power steering device

Info

Publication number: WO2020066184A1
Application number: PCT/JP2019/025352
Authority: WO
Inventors: 知幸 ▲高▼田
Original assignee: 日本電産株式会社
Priority date: 2018-09-27
Filing date: 2019-06-26
Publication date: 2020-04-02
Also published as: JPWO2020066184A1

Abstract

One embodiment of this driving control device is a driving control device that controls the driving of a motor and comprises: at least two inverters that each supply power to the motor; and a control unit that selectively performs first driving control and second driving control, said first driving control causing both of the two inverters to operate to drive the motor, and said second driving control causing one of the two inverters to operate to drive the motor, wherein the control unit uses, as the operation of the one inverter during the second driving control, a first operation mode during a first temperature condition, and a second operation mode, which produces less heat than the first production mode, during a second temperature condition, in which there is less heat dissipation from the one inverter to the other inverter compared to during the first temperature condition.

Description

Drive control device, drive device, and power steering device

The present invention relates to a drive control device, a drive device, and a power steering device.

2. Description of the Related Art Conventionally, a configuration including a plurality of inverters as a redundant design in driving a motor is known. At this time, if one of the inverters fails, the drive can be continued by the other inverter. Thus, for example, if the motor is driven by a power steering device, power assist can be continued even when the inverter fails. Further, there is known a structure in which when the output of the inverter exceeds a certain current value, overheat protection control is performed to suppress overheating of the inverter due to heat generation of the element.

For example, Patent Document 1 discloses a structure in which overheating is suppressed by distributing an output to each system according to system temperature in a two-system configuration including two inverters.

JP 2016-152682 A

When one of the inverters fails and is driven by only one system, it is necessary to output twice as much current as during normal driving, so that the heat of the inverter tends to concentrate on one side. Therefore, when one system fails, overheat protection control by output restriction is conceivable.

However, if the output of the current is limited, the output of the motor is reduced. For example, when the motor is driven by a power steering device, the load of the steering force on the driver increases, and the driving performance deteriorates. Therefore, an object of the present invention is to suppress a decrease in output of a motor while suppressing overheating of an inverter when only one system is driven.

One aspect of the drive control device according to the present invention is a drive control device that controls driving of a motor, wherein at least two inverters each of which supplies power to the motor and both the two inverters are operated to operate the motor. And a control unit that selectively executes a second drive control that drives one of the two inverters and drives the motor by operating one of the two inverters. In the drive control, the operation of the one inverter uses the first operation method in the first temperature state, and the second temperature in which heat radiation from the one inverter to the other inverter is smaller than that in the first temperature state. In the state, the second operation mode that generates less heat than the first operation mode is used. In addition, one mode of the driving device according to the present invention includes the driving control device and a motor whose driving is controlled by the driving control device.

One embodiment of a power steering device according to the present invention includes the drive control device, a motor whose drive is controlled by the drive control device, and a power steering mechanism driven by the motor.

According to the present invention, when only one system is driven, it is possible to suppress a decrease in the output of the motor while suppressing overheating of the inverter.

FIG. 1 is an exploded perspective view of the motor drive unit according to the present embodiment. FIG. 2 is a diagram schematically illustrating a block configuration of one system of the motor drive unit. FIG. 3 is a diagram illustrating an example of a voltage waveform supplied from the inverter 100 to the motor 200. FIG. 4 is a diagram schematically showing a heat distribution when driving by two systems. FIG. 5 is a diagram schematically showing a heat distribution in the case of driving by one system. FIG. 6 is a flowchart illustrating the drive control according to the present embodiment. FIG. 7 is a diagram schematically showing a heat distribution when room for heat radiation is reduced by driving one system. FIG. 8 is a diagram illustrating a control change in the first specific example of the temperature condition. FIG. 9 is a diagram illustrating an example of a rise rate of the measured temperature. FIG. 10 is a diagram illustrating a first specific example of the “driving method with low heat generation”. FIG. 11 is a diagram illustrating a second specific example of the “driving method with low heat generation”. FIG. 12 is a diagram illustrating a third specific example of the “driving method with low heat generation”. FIG. 13 is a diagram illustrating a fourth specific example of the “driving method with low heat generation”. FIG. 14 is a diagram illustrating a fifth specific example of the “driving method with low heat generation”. FIG. 15 is a diagram schematically illustrating the configuration of the power steering device according to the present embodiment.

Hereinafter, embodiments of a drive control device, a drive device, and a power steering device according to the present disclosure will be described in detail with reference to the accompanying drawings. However, in order to avoid the following description from being unnecessarily redundant and to make it easier for those skilled in the art to understand, a detailed description more than necessary may be omitted. For example, a detailed description of a well-known item or a redundant description of substantially the same configuration may be omitted.

In this specification, a drive control device that supplies electric power from a power supply to a three-phase motor having three-phase (U-phase, V-phase, and W-phase) windings (may be referred to as “coils”). As an example, an embodiment of the present disclosure will be described. However, a drive control device that supplies power from a power supply to an n-phase motor having windings of n-phase (n is an integer of 4 or more) such as four-phase or five-phase is also included in the scope of the present disclosure.

(Structure of motor drive unit 1000)

FIG. 1 is an exploded perspective view of a motor drive unit 1000 according to the present embodiment. The motor drive unit 1000 includes a motor 200, a heat sink 1001, a power board 1002, a control board 1003, and a cover 1004. The motor 200 includes two systems of three-phase (U-phase, V-phase, and W-phase) coils independently of each other. The heat sink 1001 is formed integrally with a bearing holder of the motor 200.

On the power board 1002 are mounted two systems of inverters 100 that supply power to each of the two systems of coils provided in the motor 200. The heat of each inverter 100 is radiated to a common heat sink 1001. (2) The control board 1003 is provided with two drive control circuits 300 for controlling the two inverters 100, respectively.

The cover 1004 covers the power board 1002 and the control board 1003, and is fixed to the heat sink 1001 and the motor 200. Thus, the motor drive unit 1000 is assembled as a so-called electromechanical integrated motor.

In this specification, a motor drive unit 1000 including a motor 200 as a component will be described. The motor drive unit 1000 including the motor 200 corresponds to an example of the drive device of the present invention. However, the motor drive unit 1000 may be a device for driving the motor 200 without the motor 200 as a component. The motor drive unit 1000 without the motor 200 corresponds to an example of the drive control device of the present invention. FIG. 2 is a diagram schematically showing a block configuration of one system of the motor drive unit 1000.

The motor drive unit 1000 includes an inverter 100, a control circuit 310, and a drive circuit 320 for each system. The control circuit 310 and the drive circuit 320 are included in the drive control circuit 300 described above.

The motor 200 is, for example, a three-phase AC motor, and includes U-phase, V-phase, and W-

phase coils

210, 220, and 230 for each system. The winding method of the coil is, for example, concentrated winding or distributed winding. In the present embodiment, the

coils

210, 220, and 230 of each phase of the motor 200 are connected to each other at a neutral point 240, and the neutral point 240 is also formed independently for each system. Then, a voltage or a current is supplied for driving from one end of each of the

coils

210, 220, 230 that is not connected to the neutral point 240. In this specification, “connection” between parts (components) means an electrical connection unless otherwise specified.

It should be noted that the motor according to the present invention may have the neutral point 240 connected to each other, or may have only one coil, and each of the two ends of the coil may be connected to one inverter at each end.

The motor drive unit 1000 can convert the electric power from the power supply 501 into the electric power to be supplied to the motor 200 by the inverter 100. For example, the inverter 100 can convert DC power into three-phase AC power that is a pseudo-sine wave of U-phase, V-phase, and W-phase.

As the power supply 501, for example, a DC power supply is used. However, the power supply 501 may be an AC-DC converter or a DC-DC converter, or may be a battery (rechargeable battery). Further, the motor drive unit 1000 may include a power supply inside.

A power supply separation switch 502 is provided between the power supply 501 and the inverter 100. The power supply separation switch 502 can switch connection / disconnection between the power supply 501 and the inverter 100.

A phase separation switch 610 is provided between the inverter 100 and the motor 200. The phase separation switch 610 can switch between connection and disconnection between the inverter 100 and the motor 200.

The power separation switch 502 and the phase separation switch 610 electrically disconnect the one system from the motor 200 and the power supply 501 when an abnormality occurs in one of the two inverters 100 and the like.

A capacitor 503 is connected to the power supply terminal via a power supply separation switch 502. The capacitor 503 is connected in parallel with the inverter 100 to a power supply 501 that supplies power to the inverter 100. The capacitor 503 is a so-called smoothing capacitor, and suppresses voltage ripple by absorbing a circulating current. The capacitor 503 is, for example, an electrolytic capacitor, and the capacity and the number of capacitors to be used are appropriately determined according to design specifications and the like.

The motor drive unit 1000 is provided with a thermistor 600, which is a type of temperature sensor, and the temperature of the inverter 100 is measured for each system and input to the control circuit 310. It should be noted that the control circuit 310 of each system receives not only the measured value from the own system but also the measured value from the other system.

Inverter 100 includes switching elements 101 to 106 connected to coils (windings) {210, 220, 230} of motor 200, and supplies power to motor 200 by on / off operations of switching elements 101 to 106. More specifically, the inverter 100 includes, as switch elements, high-

side switch elements

101, 103, and 105 for switching connection / disconnection of a current path through which a current flows from the power supply 501 to the motor 200, and the motor 200 to ground. Low-

side switch elements

102, 104, and 106 for switching connection / disconnection of a current path through which current flows are provided.

Each of the switch elements 101 to 106 provided in the inverter 100 is turned on and off by the drive circuit 320, and as a result of the on / off operation, power is supplied to the motor 200 to generate an output. The control of the on / off operation is executed by PWM control by the control circuit 320. That is, the control circuit 320 controls the output of the motor 200 by controlling the on / off operation of each of the switch elements 101 to 106.

(Drive control of inverter 100)

FIG. 3 is a diagram illustrating an example of a voltage waveform supplied from the inverter 100 to the motor 200. The horizontal axis in FIG. 3 indicates the electrical angle, and the vertical axis indicates the voltage value.

The inverter 100 is driven by the PWM control to convert a DC voltage from the power supply 501 into an AC voltage having a curved waveform as shown in FIG. When the AC voltage having such a waveform is supplied to the motor 200, the motor 200 generates a smooth rotational output with little torque ripple.

As described above, the motor drive unit 1000 includes the two-system drive control circuit 300 (the control circuit 310 and the drive circuit 320) and the inverter 100. Therefore, even if an abnormality occurs in one system, one normal system Thus, the driving of the motor 200 can be continued. As described above, when the motor 200 is driven by one system, heat is biased to the inverter 100 of the one system. FIG. 4 is a diagram schematically showing the heat distribution when driven by two systems, and FIG. 5 is a diagram schematically showing the heat distribution when driven by one system.

The power board 1002 comes into contact with the heat sink 1001, and the heat of the inverter 100 is radiated to the heat sink 1001. When both of the two inverters 100 are driven, the temperatures of the inverters 100 measured by the thermistor 600 are almost the same as indicated by oblique lines in the figure, and the temperature difference is small.

When an abnormality occurs in one of the two inverters 100_NG, the drive of the one inverter 100_NG is stopped, and only the other normal inverter 100_OK is driven to supply power to the motor 200. As a result, heat is biased toward the normal inverter 100_OK, as indicated by hatching in the figure. However, such a heat bias may occur from the time of driving with two systems. In addition, in the case of a device such as a power steering device that requires the output of the motor 200 to be maintained, the normal inverter 100_OK supplies power for two systems, and the heat generated by the inverter 100_OK also increases. As a result, the temperature of the inverter 100_OK measured by the thermistor 600 is higher than the temperature when both of the two inverters 100 are driven.

If the temperature of the inverter 100 becomes too high, it causes a failure. Therefore, generally, overheat protection control is known as control of the inverter 100 at a high temperature, and heat generation of the inverter 100 is suppressed by limiting the current. . However, the power supply to the motor 200 is also limited by the current limitation, and there is a possibility that the output maintenance of the motor 200 is lost. Therefore, in the present embodiment, in order to suppress a decrease in the output of the motor 200 while suppressing overheating of the inverter 100, drive control as described below is executed. FIG. 6 is a flowchart showing drive control in the present embodiment.

In this drive control, first, in step S101, it is determined whether an abnormality has occurred in one of the two systems. As a method for determining the occurrence of an abnormality, any conventionally known arbitrary determination method is employed. In addition, the target of the abnormality determination may be the inverter 100, the drive circuit 320, or the control circuit 310.

If no abnormality has occurred in either of the two systems (both are normal) (step S101; NO), normal driving using both of the two systems is continued. If an abnormality has occurred in one of the two systems (step S101; YES), the process proceeds to step S102, and the control circuit 310, the drive circuit 320, and the inverter 100 are stopped for the system in which the abnormality has occurred. Then, the driving is continued by one normal system.

That is, in steps S101 to S102, the first drive control for driving the motor 200 by operating both of the two inverters 100 and the second drive control for driving the motor 200 by operating one of the two inverters 100 are performed. 2 drive control is selectively executed.

When the drive is switched from the drive by both the two systems, the drive of one system is, for example, the drive by the voltage waveform shown in FIG. 3, and the power supply for two systems is performed by one system. As a result, the output of the motor 200 is also maintained. Further, when the motor 200 is driven by only one normal system, the heat generated by the one system is higher than the heat generated by one system when driven by both the two systems, and as shown in FIG. Heat is biased to inverter 100_OK. The unbalanced heat is radiated to the heat sink 1001, but when the abnormal inverter 100_NG is stopped, a function of radiating heat from the normal inverter 100_OK to the abnormal inverter 100_NG occurs. That is, the stopped inverter 100_NG side functions as an additional heat radiating unit.

When the high heat generation motor 200 is driven by one system, it is then determined whether a temperature condition requiring a control change has been reached (step S103). Here, the temperature condition requiring a control change is a temperature condition under which heat radiation to the stopped inverter 100_NG side is reduced. Specific conditions will be described later.

While the temperature condition requiring the control change is not reached (Step S103; NO), the drive of one system that generates high heat is continued, and when the temperature condition requiring the control change is reached (Step S103; YES), Step S104 is performed. And the driving method is changed to a driving method with low heat generation. That is, in steps S103 to S104, the first operation (driving) method is used in the first temperature state, and the second temperature in which heat dissipation from one inverter to the other inverter is smaller than that in the first temperature state. In the state, a second operation (drive) method that generates less heat than the first operation (drive) method is used.

As will be described later in detail for a specific driving method, the driving method with low heat generation performed in step S104 maintains the output of the motor 200 while suppressing generation of torque ripple by suppressing heat generation. It is a driving method. After shifting to such a driving method in which heat generation is low, it is determined whether or not a temperature condition that requires overheating protection has been reached (step S105). The temperature condition that requires overheating protection is, for example, a temperature that exceeds a threshold temperature at which overheating protection starts.

While the temperature condition that requires overheat protection is not reached (step S105; NO), the above-described drive method with low heat generation is continued, and when the temperature condition that requires overheat protection is reached (step S105; YES), the process proceeds to step S106. Then, the current is limited by the overheat protection, so that the heat generation of the inverter 100 is suppressed. As described above, in the overheat protection, the heat generation is suppressed and the output of the motor 200 is also suppressed. That is, in steps S105 to S106, the power supply to the motor 200 is limited in the third temperature state in which heat radiation from one inverter to the other inverter is smaller than in the second temperature state described above. As described above, in the drive control according to the present embodiment, the output of the motor 200 is maintained as much as possible by using the drive system with low heat generation before the overheat protection is performed. Hereinafter, a specific example of the above-mentioned “temperature condition requiring control change” will be described.

In the first specific example, the second operation method is used in the second temperature state in which the temperature difference between the two inverters is smaller than the first temperature state. That is, when the difference between the temperatures measured by the thermistor 600 for each of the two systems falls below a predetermined threshold, a driving method that generates less heat is used.

As shown in FIG. 5, when heat is biased in the driving inverter 100_OK, the difference between the measured values of the two thermistors 600 (that is, the temperature difference) is large. Then, the stopped inverter 100_NG functions as a heat radiator due to such a temperature difference, so that the driven inverter 100_OK has room for heat radiation and can continue the driving method of generating high heat. However, if high heat generation by the inverter 100_OK during driving continues, there is a possibility that room for heat radiation may decrease depending on the environmental temperature and the like. FIG. 7 is a diagram schematically showing a heat distribution when room for heat radiation is reduced by driving one system.

If the high heat generated by the driven inverter 100_OK continues, for example, when the environmental temperature is high, the temperature of the heat sink 1001 increases and the temperature of the stopped inverter 100_NG also increases. As a result, the difference between the measured values of the two thermistors 600 (that is, the temperature difference) decreases, and the function of the stopped inverter 100_NG as a heat radiating unit also decreases. Therefore, room for heat radiation is lost as a whole, and the temperature of the inverter 100_OK during driving may be further increased. When such a temperature state (temperature condition) is reached, the driving method of the driving inverter 100_OK is changed to the driving method of low heat generation.

(Specific examples of temperature conditions)

FIG. 8 is a diagram illustrating a control change in the first specific example of the temperature condition. The horizontal axis of FIG. 8 indicates the passage of time, and the vertical axis indicates the temperature difference.

If the drive of high heat generation is continued in a certain high-temperature environment or the like, the temperature difference between the two systems decreases over time. When the temperature difference falls below the threshold value TV1, the driving method is changed to a low heat generation driving method and driving is continued. By changing the driving method and reducing heat generation, the temperature difference also stops decreasing, and there is room for heat radiation, so that the output can be maintained.

It should be noted that it is difficult to discriminate between a case where both the inverters 100_OK and 100_NG are at low temperature and a case where there is little room for heat radiation, based on the judgment based on only the temperature difference, because the heat generated by the inverter 100_OK during driving is small. Therefore, in the first specific example, desirably, in the second temperature state in which the temperature of one of the driven inverters exceeds a predetermined temperature and the temperature difference between the two inverters is smaller than the first temperature state. A second mode of operation is used. That is, when the measured temperature of the thermistor 600 in the system being driven exceeds a predetermined threshold value and the difference between the temperatures measured by the thermistor 600 for each of the two systems falls below the predetermined threshold value, a low heat generation driving method Is preferably used.

In the second specific example of the “temperature condition requiring control change”, the temperature of one of the driven inverters exceeds a predetermined temperature, and the temperature rise of the one inverter is higher than the first temperature state. In the second temperature state, the second operation mode is used. That is, when the measured temperature of the thermistor 600 exceeds a predetermined threshold value and the rate of increase of the measured temperature exceeds the predetermined threshold value, a low heat generation driving method is used. According to the second specific example, since the temperature state is determined only by the temperature on the driving side, wiring and the like for obtaining a measured value of the system on the other side become unnecessary, and cost reduction is expected. FIG. 9 is a diagram showing an example of the rate of rise of the measured temperature.横 The horizontal axis in FIG. 9 indicates the passage of time, and the vertical axis indicates the temperature measured by the thermistor 600 on the drive side.

The graph of FIG. 9 shows a line L1 representing an example with a large temperature rise rate and a line L2 representing an example with a small temperature rise rate. If the rate of temperature rise is large, the same temperature rise occurs in a short time. For this reason, if the driving method of high heat generation is continued, there is a possibility that the temperature may reach the threshold temperature TV2 for overheating protection and the current may be limited. Therefore, it is desirable to change to a drive system that generates less heat before reaching overheat protection.

On the other hand, if the rate of temperature rise is small, it takes a long time for the same temperature rise to occur, during which time heat dissipation proceeds to the heat sink 1001 and the stopped inverter 100_NG. For this reason, it is expected that even if the driving method of high heat generation is continued, the temperature will not reach the threshold temperature TV2 for overheating protection and the rise in temperature will level off. As described above, the state of heat radiation can be determined based on the temperature rise rate, and the drive system can be appropriately changed.

(Specific example of drive system)

Hereinafter, a specific example of the “driving method with low heat generation” will be described.

The two-system inverter 100 includes switch elements 101 to 106 in each of the inverters 100, and supplies power to the motor 200 by turning on and off the switch elements 101 to 106. In the second operation (driving) method with low heat generation, the switching elements 101 to 106 are turned on and off less frequently than in the first operation (driving) method. Since the switch elements 101 to 106 generate heat with the on / off operation (switching), the frequency of the on / off operation of the switch elements 101 to 106 is reduced, so that the heat generation of the inverter 100 is reduced. Further, as described below, the output of the motor 200 can be maintained even if the frequency of the on / off operation is reduced. FIG. 10 is a diagram showing a first specific example of the “driving method with low heat generation”.

In the first operation (drive) method, on / off operations are performed in parallel for each of n phases (for example, three phases), whereas in the second operation (drive) method shown in FIG. Is stopped at any one time.

The driving method that generates the voltage waveform shown in FIG. 3 is called a three-phase modulation method, and the driving method shown in FIG. 10 is called a two-phase modulation method. That is, in the driving method shown in FIG. 10, the V-phase is maintained at the voltage 0 from the electrical angle of 0 ° to 90 °, and the V-phase switch element is fixed to the on / off state indicating the voltage of 0. Therefore, the on / off operation of the PWM control is stopped for the V-phase switch element from the electrical angle of 0 ° to 90 °. (4) The voltage of the W-phase is maintained at 0 from the electrical angle of 90 ° to 210 °, and the ON / OFF operation of the PWM control is stopped for the W-phase switch element. Furthermore, the U phase is maintained at the voltage 0 from 210 ° to 330 ° of the electrical angle, and the ON / OFF operation of the PWM control is stopped for the U phase switch element. Furthermore, the V phase is maintained at the voltage 0 from the electrical angle of 330 ° to 360 ° (0 °), and the ON / OFF operation of the PWM control is stopped for the V phase switch element.

As described above, in the driving method shown in FIG. 10, the on / off operation is performed only in two phases at a time among the three phases of the motor 200, and the on / off operation is always stopped in any one phase. As a result, in the two-phase modulation method, the on-off operation of the switch element is reduced by about one third in the two-phase modulation method as compared with the three-phase modulation method shown in FIG.

On the other hand, the output of the motor 200 is determined by the power supplied by the voltage waveform shown in FIG. 10, but the supplied power is substantially equal to the power supplied by the voltage waveform shown in FIG. Therefore, the output of the motor 200 is almost maintained even when the three-phase modulation method is changed to the two-phase modulation method. FIG. 11 is a diagram showing a second specific example of the “driving method with low heat generation”.

In the example shown in FIG. 11, the inverter 100 turns on and off the switching elements 101 to 106 at the set carrier frequency, and the second operation (drive) method has a carrier frequency higher than that of the first operation (drive) method. Low. The left side of FIG. 11 illustrates an example of the carrier frequency in the first operation mode, and the right side of FIG. 11 illustrates the example of the carrier frequency in the second operation mode.

That is, the drive circuit 320 is set to, for example, 20 kHz as a carrier frequency in the PWM control by the control circuit 310, and the drive circuit 320 is set to 20 kHz at the set 20 kHz when driving with two systems or in a drive system with high heat generation by one system. The switch elements 101 to 106 of the inverter 100 are turned on and off.

On the other hand, in the drive system with low heat generation, the drive circuit 320 sets a carrier frequency of, for example, 16 kHz by the control circuit 310, and the drive circuit 320 turns on and off the switch elements 101 to 106 of the inverter 100 at 16 kHz.

By changing the carrier frequency to a low frequency in this manner, the frequency of the on / off operation of the switch elements 101 to 106 is easily reduced, and the heat generation of the inverter 100 is also suppressed. Note that the carrier frequency can be changed independently of the power waveform by the inverter 100. Therefore, for example, the voltage waveform shown in FIG. 3 may be used in both the high heat generation drive method and the low heat generation drive method. That is, in the second specific example shown in FIG. 11, the heat generation of the inverter 100 is suppressed even if the voltage waveform is not changed between the high heat generation drive method and the low heat generation drive method.

The second specific example shown in FIG. 11 may be employed in combination with the first specific example shown in FIG. That is, in the driving method of high heat generation, for example, the voltage waveform shown in FIG. 3 and the carrier frequency of 20 kHz are used, and in the driving method of low heat generation, the voltage waveform shown in FIG. 10 and the carrier frequency of 16 kHz are used. Similarly, the second specific example shown in FIG. 11 may be employed in combination with another specific example described later. FIG. 12 is a diagram showing a third specific example of the “driving method with low heat generation”.

In the example shown in FIG. 12, in the first operation (drive) method of high heat generation, a sine wave power waveform is formed by the on / off operation of the switch element, and in the second operation (drive) method of low heat generation, the switch element is used. A trapezoidal wave is formed by the on / off operation of. The left side of FIG. 12 shows a sine wave which is a power waveform in the first operation mode, and the right side of FIG. 12 shows a trapezoidal wave which is a power waveform in the second operation mode.

In the case of a sine wave whose power waveform is a smooth curve, the waveform is formed by the on / off operation of the switch element being constantly performed by PWM control, but in the case of a trapezoidal wave, the on / off operation is stopped in a section where the amplitude is constant. It becomes possible. Therefore, in the trapezoidal wave, the on / off operation is stopped in some sections, thereby suppressing the heat generation of the inverter. FIG. 13 is a diagram showing a fourth specific example of the “driving method with low heat generation”.

In the example shown in FIG. 13, in the first operation (drive) method of high heat generation, a sine wave power waveform is formed by the on / off operation of the switch element, and in the second operation (drive) method of low heat generation, the switch element A rectangular wave is formed by the on / off operation of. The left side of FIG. 13 shows a sine wave which is a power waveform in the first operation mode, and the right side of FIG. 13 shows a rectangular wave which is a power waveform in the second operation mode.

In the case of a sine wave whose power waveform is a smooth curve, the waveform is formed by the on / off operation of the switch element constantly performed by PWM control, but in the case of a rectangular wave, the polarity is reversed because the amplitude is constant. Excluding the point, the on / off operation can be stopped in an arbitrary section. Therefore, in the case of the rectangular wave, the on / off operation is stopped in an arbitrary section, so that heat generation of the inverter is suppressed. FIG. 14 is a diagram showing a fifth specific example of the “driving method with low heat generation”.

In the example shown in FIG. 14, in the first operation (drive) method, both the high-side switch element and the low-side switch element perform on / off operations in parallel, and in the second operation (drive) method, the high-side switch element And the low-side switch element has a lower on / off frequency than the other. More specifically, in FIG. 14, a solid-on operation (that is, an operation fixed to an ON state in a partial section) is used as an on-off operation in the high-side switch element, and an on-off operation of PWM control is used in the low-side switch element. An example is shown.

The high-side switch element that performed the PWM control on / off operation in parallel with the low-side switch element in the drive system with high heat generation stops almost on-off operation by the solid-on operation in the drive system with low heat generation. Therefore, in the drive system with low heat generation, the on / off operation of the switch element is reduced by almost half as a whole, and the heat generation of the inverter 100 is suppressed.

Note that, even in the PWM control of only one of the high-side switch element and the low-side switch element, an arbitrary power waveform can be formed as the power waveform. Therefore, the fifth specific example shown in FIG. 14 can be combined with the third and fourth specific examples described above.

Further, even in the PWM control of only one of the high-side switch element and the low-side switch element, any frequency can be adopted as the carrier frequency. Therefore, the fifth specific example shown in FIG. 14 may be combined with the second specific example described above. Further, the fifth specific example shown in FIG. 14 may be combined with the above-described first, third, and fourth specific examples and also with the above-described second specific example.

(Embodiment of power steering device)

Vehicles such as automobiles generally include a power steering device. The power steering device generates an assist torque for assisting a steering torque of a steering system generated by a driver operating a steering handle. The auxiliary torque is generated by the auxiliary torque mechanism, and can reduce the burden of the driver's operation.

The motor drive unit 1000 of the above embodiment is suitably used for a power steering device. FIG. 15 is a diagram schematically illustrating a configuration of a power steering device 2000 according to the present embodiment. The electric power steering apparatus 2000 includes a steering system 520 and an auxiliary torque mechanism 540.

The steering system 520 is, for example, a steering handle 521, a steering shaft 522 (also referred to as a “steering column”), a universal joint 523A, 523B, and a rotating shaft 524 (also referred to as a “pinion shaft” or “input shaft”). ).

The steering system 520 includes, for example, a rack and pinion mechanism 525, a rack shaft 526, left and right ball joints 552A and 552B,

tie rods

527A and 527B,

knuckles

528A and 528B, and left and right steering wheels (for example, left and right front wheels) 529A. 529B.

The steering handle 521 is connected to a rotating shaft 524 via a steering shaft 522 and

universal shaft joints

523A and 523B. A rack shaft 526 is connected to the rotation shaft 524 via a rack and pinion mechanism 525. The rack and pinion mechanism 525 has a pinion 531 provided on the rotation shaft 524 and a rack 532 provided on the rack shaft 526. The right steering wheel 529A is connected to the right end of the rack shaft 526 via a ball joint 552A, a tie rod 527A, and a knuckle 528A in this order. Similarly to the right side, the left steering wheel 529B is connected to the left end of the rack shaft 526 via a ball joint 552B, a tie rod 527B, and a knuckle 528B in this order. Here, the right side and the left side respectively correspond to the right side and the left side viewed from the driver sitting on the seat.

According to the steering system 520, when the driver operates the steering handle 521, a steering torque is generated and transmitted to the left and right steering wheels 529A and 529B via the rack and pinion mechanism 525. Thus, the driver can operate the left and right steering wheels 529A, 529B.

The auxiliary torque mechanism 540 includes, for example, a steering torque sensor 541, a mechanical and electric integrated motor 543, and a speed reduction mechanism 544. The auxiliary torque mechanism 540 applies an auxiliary torque to a steering system 520 from the steering handle 521 to the left and right steering wheels 529A, 529B. Note that the auxiliary torque may be referred to as “additional torque”. For example, the motor drive unit 1000 shown in FIG. 1 is preferably used as the electromechanical integrated motor 543.

A mechanism constituted by elements other than the steering torque sensor 541 and the electric and mechanical integrated motor 543 among the elements shown in FIG. 15 corresponds to an example of a power steering mechanism driven by the motor 200.

The steering torque sensor 541 detects the steering torque of the steering system 520 given by the steering handle 521. A detection signal (hereinafter, referred to as “torque signal”) from the steering torque sensor 541 is input to the electromechanical integrated motor 543, and a control circuit in the electromechanical integrated motor 543 calculates an auxiliary torque, and the auxiliary torque is calculated. Is generated. The electromechanical integrated motor 543 generates an auxiliary torque corresponding to the steering torque based on the drive signal. The assist torque is transmitted to the rotation shaft 524 of the steering system 520 via the speed reduction mechanism 544. The reduction mechanism 544 is, for example, a worm gear mechanism. The auxiliary torque is further transmitted from the rotation shaft 524 to the rack and pinion mechanism 525.

The power steering apparatus 2000 is classified into a pinion assist type, a rack assist type, a column assist type, and the like, depending on a position where the assist torque is applied to the steering system 520. FIG. 15 shows a column assist type power steering device 2000. However, the power steering device 2000 is also applied to a rack assist type, a pinion assist type, and the like.

According to the power steering apparatus 2000, the left and right steering wheels 529A and 529B can be operated by the rack shaft 526 using a combined torque obtained by adding the assisting torque of the electric and mechanical integrated motor 543 to the steering torque of the driver. In particular, by using the motor drive unit 1000 of the above-described embodiment for the electromechanical motor 543, even if an abnormality occurs in one of the two systems, heat generation is suppressed and the assist torque is maintained.

Note that, here, a power steering device is exemplified as an example of a method of using the drive control device and the drive device of the present invention. However, a method of using the drive control device and the drive device of the present invention is not limited to the above. It can be used widely.

The embodiments described above are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the embodiments described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

100:

inverters

101, 103, 105: high-

side switch elements

102, 104, 106: low-side switch elements 200:

motors

210, 220, 230: coil 310: control circuit 320: drive circuit 501: power supply 503: capacitor 600: thermistor 1000 : Motor drive unit 1001 #: Heat sink 1002 #: Power board 1003 #: Control board 2000 #: Power steering device

Claims

In a drive control device that controls the drive of the motor,

At least two inverters each supplying power to the motor;

A first drive control for driving the motor by operating both of the two inverters and a second drive control for driving the motor by operating one of the two inverters are selectively performed. A control unit;

With

The control unit operates as the operation of the one inverter in the second drive control,

In the first temperature state, the first operation mode is used,

A drive control device that uses a second operation mode in which heat generation is lower than the first operation mode in a second temperature state in which heat radiation from one inverter to the other inverter is smaller than in the first temperature state. .
The drive control device according to claim 1, wherein the second operation mode is used in the second temperature state in which the temperature difference between the two inverters is smaller than the first temperature state.
2. The second operation mode is used in the second temperature state in which the temperature of the one inverter exceeds a predetermined temperature and the temperature difference between the two inverters is smaller than the first temperature state. 3. Or the drive control device according to 2.
2. The second operation mode is used in the second temperature state where the temperature of the one inverter exceeds a predetermined temperature and the temperature rise of the one inverter is higher than the first temperature state. 3. 3. The drive control device according to claim 1.
The control unit includes:

The power supply to the motor according to any one of claims 1 to 4, wherein a power supply to the motor is limited in a third temperature state in which heat radiation from the one inverter to the other inverter is further smaller than in the second temperature state. The drive control device according to any one of the preceding claims.
The inverter includes a switch element in each inverter, and supplies power to the motor by an on / off operation of the switch element,

The drive control device according to any one of claims 1 to 5, wherein the second operation mode has a lower on / off frequency of the switch element than the first operation mode.
The inverter turns on and off the switch element at a set carrier frequency,

The drive control device according to claim 6, wherein the second operation mode has a lower carrier frequency than the first operation mode.
The motor has three or more n-phase windings;

In the first operation mode, on / off operations are performed in parallel for each of the n phases,

8. The drive control device according to claim 6, wherein in the second operation mode, at least one phase of the n phases at which on / off operation is stopped exists at any one time. 9.
The control unit includes:

In the first operation method, a power waveform of a sine wave is formed by an on / off operation of the switch element,

The drive control device according to any one of claims 6 to 8, wherein in the second operation method, a rectangular wave or a trapezoidal wave is formed by an on / off operation of the switch element.
The inverter includes, as the switch element, a power supply side switch element that switches connection / disconnection of a current path through which a current flows from a power supply to the motor, and connection / disconnection of a current path through which a current flows from the motor to the ground. And a switching element on the ground side for switching.

In the first operation mode, both the power supply-side switch element and the ground-side switch element perform on / off operations in parallel,

The drive control device according to any one of claims 5 to 9, wherein in the second operation mode, one of the power supply-side switch element and the ground-side switch element has a lower on / off frequency than the other.
The drive control device according to any one of claims 1 to 10, further comprising a heat sink that the two inverters dissipate heat in common.
The drive control device according to any one of claims 1 to 11, further comprising two temperature sensors that detect the temperatures of the two inverters, respectively.
A drive control device according to any one of claims 1 to 12,

A motor whose drive is controlled by the drive control device;

A driving device comprising:
A drive control device according to any one of claims 1 to 12,

A motor whose drive is controlled by the drive control device;

A power steering mechanism driven by the motor;

A power steering device comprising: