JP2015047019A - Motor control apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a motor control apparatus capable of reducing generation of noise while reducing cost rise even when a wire harness length from a motor driving part up to a motor is long.SOLUTION: Since an inductance component increases when a length A of a vehicle wire harness 315 is extended, conduction noise may be increased. The higher the PWM frequency of a signal for driving a motor 200, the conduction noise is increased. Thereby when the vehicle wire harness 315 is extended and the PWM frequency is set to a high value, large conduction noise is generated. In the invention, when the length A of the vehicle wire harness is long, the PWM frequency of the signal for driving the motor 200 is reduced to suppress generation of the conduction noise.

Description

  The present invention relates to a motor control device such as a motor control device for a seat belt retractor for a vehicle.

  Noise may be generated by driving a switching element in an auxiliary device such as a radio mounted on a vehicle. For this reason, conventionally, techniques for reducing this noise are known.

  Japanese Patent Application Laid-Open No. 2004-228561 describes a technique for changing the frequency of a PWM signal for turning on and off a plurality of MOSD-FET elements used as switching elements of a DC-DC converter circuit within a predetermined range.

  The frequency of the PWM signal is made variable within a predetermined range, and the frequencies of the plurality of PWM signals generated at the same time are made different to reduce the generation of noise.

JP 2012-70527 A

  By the way, for example, the seat belt retractor motor control device (ECU (Electrical Control Unit)) mounted on the vehicle is mounted on both the driver's seat and the passenger seat, but the mounting position differs depending on the vehicle. The distance to the motor for the belt retractor may be different between the ECU of the driver seat and the ECU of the passenger seat, and the wire harness (electric line) length may be different from each other.

  Therefore, when the wire harness length is long, there is a problem that radio noise is generated due to the inductance component of the wire harness even if the frequency of the PWM signal is simply changed.

  In that case, it is conceivable to take countermeasures with noise countermeasure components such as a noise removal filter, but this is not a good idea because it leads to an increase in cost.

  An object of the present invention is to realize a motor control device capable of reducing the generation of noise while reducing the cost increase even when the wire harness length from the motor drive unit to the motor is long.

  In order to achieve the above object, the present invention is configured as follows.

  The motor control device of the present invention has a plurality of switching elements, is connected between a motor driving unit that drives a motor that operates a movable part of a vehicle, and the motor and the motor driving unit. A power line for supplying electric power for driving the motor, a motor drive driver unit for supplying a signal for controlling the plurality of switching elements to the motor drive unit, and a PWM signal for controlling the plurality of switching elements are generated. And a PWM signal generation unit that supplies the motor drive driver unit.

  And a PWM signal generation part sets the center frequency of a PWM signal according to the inductance value of the said electric wire path.

  ADVANTAGE OF THE INVENTION According to this invention, even if it is a case where the wire harness length from a motor drive part to a motor is long, the motor control apparatus which can reduce generation | occurrence | production of noise can be implement | achieved, reducing cost increase.

It is an arrangement block diagram of a collision judging means and a seat belt device in a vehicle to which the present invention is applied. It is explanatory drawing of the seatbelt apparatus for vehicles. It is a schematic block diagram of the control apparatus for seatbelt retractors of the retractor in Example 1 of this invention. It is a circuit diagram explaining the motor drive part shown in FIG. 3 in detail. It is a figure which shows an example of the waveform of the PWM frequency used for Example 1 of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

(Example 1)
FIG. 1 is an arrangement configuration diagram of collision determination means and a seat belt device in a vehicle to which the present invention is applied.

  In FIG. 1, a vehicle 112 includes various sensors such as an obstacle sensor 102 and a wheel speed sensor 104, and a collision determination controller (vehicle collision determination unit) 106 as a collision determination unit.

  An obstacle sensor 102 that outputs a signal corresponding to the distance to the obstacle is attached to the front portion of the vehicle 112. The output signal of the obstacle sensor 102 is transmitted to the collision determination controller 106 that is electrically connected to the obstacle sensor 102.

  A signal from the wheel speed sensor 104 that outputs a signal corresponding to the speed of the vehicle 112 is also transmitted to the collision determination controller 106 that is electrically connected to the wheel speed sensor 104.

  The collision determination controller 106 determines whether or not the vehicle 112 collides with an obstacle based on signals from the obstacle sensor 102 and the wheel speed sensor 104. For example, when the distance to the obstacle obtained from the output signal of the obstacle sensor 102 is shorter than a predetermined value and the vehicle speed obtained from the output signal of the wheel speed sensor 104 is higher than the predetermined value, The collision determination controller 106 determines that the vehicle 112 collides with an obstacle.

  Then, before the vehicle 112 collides with an obstacle, a command signal is output to the brake assist device 108 and the retractor 100 (driver's seat side).

  The brake assist device 108 and the seat belt drive controller 110 (driver's seat side) are electrically connected to the collision determination controller 106 and execute predetermined operations based on command signals from the collision determination controller 106, respectively. To do.

  Further, the seat belt drive controller 114 (passenger seat side) and the retractor 116 (passenger seat side) have the same configuration as the seat belt drive controller 110 (driver seat side) and the retractor 100 (driver seat side). Perform the action.

  FIG. 2 is an explanatory diagram of a vehicle seat belt device. FIG. 2 shows the seat belt device on the driver's seat side, but the passenger seat side has the same configuration. In the following description, the seat belt device on the driver's seat side will be described.

  In FIG. 2, the retractor 100 includes a motor 200, and the seat belt 206 can be wound by rotating the motor 200. Here, the motor 200 may be a DC motor or a brushless motor. For example, consider a case where the occupant 202 is driving the vehicle 112 and the occupant 202 moves to the front of the vehicle although it is minute, and a gap is generated between the occupant 202 and the seat 204.

  In such a situation, when the vehicle 112 collides with an obstacle, the occupant 202 is not restrained by the seat 204 and may be strongly hit against the seat 204.

  However, the seat belt device can wind up the seat belt 206 before the vehicle 112 and the obstacle collide with each other by the motor 200 included in the retractor 100, thereby eliminating the gap between the occupant 202 and the seat 204. .

  Therefore, when the vehicle 112 and the obstacle collide, the occupant 202 is already in a state of being restrained by the seat 204, so that the impact on the occupant 202 can be reduced.

  By driving the motor 200 controlled by the seat belt drive controller 110, the retractor 100 performs a pre-crash operation of the occupant 202, automatic fitting for the purpose of improving comfort or automatic storage of the seat belt 206, and a warning operation to call the occupant 202 for attention. Etc. are to be wound up.

  FIG. 3 is a schematic configuration diagram of the seat belt retractor control device (ECU) 302 of the retractor 100 according to the first embodiment of the present invention.

  In FIG. 3, when a power source (VB) 300 supplied from a vehicle battery and an alternator driven by an engine is supplied to a custom IC 304 inside a seat belt retractor control device (ECU) 302, The vehicle battery voltage is supplied to the power supply circuit 306.

  The power supply circuit 306 generates a positive power supply voltage (VCC = 5 V) to be supplied to signal-related elements such as a central control unit (CPU) 308 that controls signal processing. The power supply circuit 306 has a function of receiving a periodic signal from the CPU 308 and monitoring the operation of the CPU 308 and a function of resetting the CPU 308.

  The ECU 302 has a motor drive unit 310 for driving the motor 200. The motor driving unit 310 is configured by an H bridge circuit using a MOSFET, for example. In addition, the custom IC 304 includes a motor drive driver unit 312, and the CPU 308 includes a PWM signal generation unit 318 that generates a PWM frequency and a duty ratio.

  The PWM signal generation unit 318 generates a PWM signal that drives the motor drive unit 310. The PWM signal from the PWM signal generation unit 318 is supplied to the motor drive driver unit 312.

  Then, the motor drive driver unit 312 drives the motor drive unit 310 according to the PMW signal, and electric power is supplied from the motor drive unit 310 to the motor 200 via the vehicle wire harness (electric line) 315. The frequency of the PWM signal is controlled by the CPU 308.

  The current detection unit 314 is connected to the motor drive unit 310, detects the current flowing through the motor 200, converts the voltage, and amplifies it. Then, an output signal from the current detection unit 314 is input to the A / D converter 316 inside the custom IC 304. The A / D converter 316 is connected to the CPU 308, and an output signal from the current detection unit 314 is supplied to the CPU 308 via the A / D converter 316.

  Here, the power supply circuit 306, the motor drive driver unit 312 and the like in the custom IC 304 may be configured with external components.

  FIG. 4 is a circuit diagram illustrating in detail the motor driving unit 310 shown in FIG.

  In FIG. 4, the motor driving unit 310 is configured by an H bridge using four MOSFETs (400a, 400b, 400c, 400d).

  That is, the source of the MOSFET 400a is connected to the power supply 300, and the drain of the MOSFET 400a is connected to the drain of the MOSFET 400c. Further, the source of the MOSFET 400b is connected to the power supply 300, and the drain of the MOSFET 400b is connected to the drain of the MOSFET 400d.

  The source of the MOSFET 400c and the source of the MOSFET 400d are connected to each other and to the current detection unit 314.

  The motor 200 is connected between the drain of the MOSFET 400a, the drain of the MOSFET 400b, and the connection point, and the drain of the MOSFET 400b, the drain of the MOSFET 400d, and the connection point.

  In order to drive the motor 200, the CPU 308 gives a signal to the motor drive driver unit 312 according to the drive mode. The motor drive driver unit 312 generates a PWM signal, controls the respective gate voltages of the MOSFETs (400a, 400b, 400c, 400d), switches the MOSFETs (400a, 400b, 400c, 400d), and supplies power to the motor 200. Supply.

  Here, the Pch MOSFET connected to the high side can be replaced by an Nch MOSFET depending on, for example, a drive circuit having a booster circuit.

  ECU 302 and motor 200 are connected via vehicle wire harness 315, but the length (A) of vehicle wire harness 315 between ECU 302 and motor 200 differs for each vehicle.

  When the MOSFETs (400a, 400b, 400c, 400d) are PWM-driven, conduction noise generated by switching propagates to the vehicle wire harness 315. The magnitude Vn of the conduction noise at this time is expressed by the following formula (1).

Vn = L × (di / dt) (1)
Here, in the above formula (1), L is an inductance component, and di / dt represents a change amount of current per unit time.

  When the vehicle wire harness length A shown in FIG. 4 is increased, the inductance component L is increased, and thus the conduction noise Vn is increased by the above equation (1). In addition, di / dt increases as the PWM frequency increases.

  As described above, as the vehicle wire harness A becomes longer and the PWM frequency is set to a higher value, a large conduction noise is generated.

  In the present invention, when the vehicle wire harness is long, the PWM frequency is lowered to suppress the generation of conduction noise.

  FIG. 5 is a diagram illustrating an example of a waveform of a PWM frequency used in Embodiment 1 of the present invention. In the example shown in FIG. 5, a case is considered in which the vehicle wire harness length A ′ on the passenger side is longer than the vehicle wire harness length A on the driver side (A <A ′).

  The frequency of the PWM signal supplied to the motor 200 on the driver seat side is represented by a solid line, the center frequency of the PWM signal frequency is represented by fA, the frequency of the PWM signal supplied to the motor 200 on the passenger seat side is represented by a broken line, and the PWM The center frequency of the signal frequency is assumed to be fA ′.

  In this case, when the magnitude of the conduction noise Vn generated on the driver's seat side and the magnitude of the conduction noise Vn ′ generated on the passenger side are compared, the vehicle wire on the passenger's seat side is longer than the vehicle wire harness length A on the driver's seat side. Since the harness length A ′ is longer, Vn <Vn ′.

  In the prior art, for example, noise is reduced by shifting the PWM frequency by a center frequency of about ± 15% using dither control or the like. On the other hand, in the first embodiment of the present invention, in addition to the above-described conventional technique, by reducing the center frequency fA ′ on the passenger seat side where the vehicle wire harness length A is long (state of FIG. 5), the conduction noise is reduced. Vn ′ having a large value can be reduced, and noise can be further reduced as a whole.

  For example, when the center frequency fA is 18 kHz, the center frequency fA ′ is 14 kHz and the frequency difference is 4 kHz. However, for each vehicle, it is possible to appropriately set a reduction value of the center frequency fA ′ on the passenger seat side having a long vehicle wire harness length.

  That is, the setting of the center frequency of the PWM frequency can be selected and set in a shipping test of the motor control device, and can be configured easily. The center frequency setting may be stored in a nonvolatile memory (EEPROM) or the like.

  Generally, if the PWM frequency is too low, it will enter the human audible range. In addition, if the frequency is too high, heat generation due to switching loss increases, so that expensive parts are required and the cost is increased.

  In addition, the seat belt retractor motor control device has an emergency operation mode that operates in the event of a vehicle collision and a normal operation mode that operates in a normal state such as normal belt winding and storage. In the normal operation mode, the current to be used is relatively small, but in the emergency operation mode, it is necessary to restrain the occupant safely, so a high current is required.

  Therefore, in the emergency operation mode, the PWM frequency is set low (for example, 14 kHz and 10 kHz) while maintaining the center frequency difference between the driver seat side and the passenger seat side, and in the normal operation mode, the driver seat side is set. By setting the PWM frequency high (for example, 18 kHz and 14 kHz) while maintaining the center frequency difference between the passenger side and the passenger seat side, both comfort and safety can be achieved.

  As described above, according to the first embodiment of the present invention, the wire harness between the driver for the seatbelt retractor on the driver's seat side and the control device for the seatbelt retractor, the motor for the seatbelt retractor on the passenger seat side, and the seat The center frequency of the motor drive PWM signal connected to the longer wire harness of the wire harness between the belt retractor control device and the motor drive PWM signal connected to the shorter wire harness. Since the motor is driven by setting it lower than the center frequency, it is possible to reduce the occurrence of conduction noise even when the wire harness is long.

  Further, according to the first embodiment of the present invention, since the PWM frequency is changed between the emergency operation mode and the normal operation mode, both comfort and safety can be achieved. .

(Example 2)
Next, a second embodiment of the present invention will be described.

  In the first embodiment, the wire harness (electric wire path) on the driver's seat side and the wire harness (electric wire path) on the passenger seat side are connected to the longer one (the one with the longer track length). In this configuration, the center frequency of the motor driving PWM signal is set low.

  In the second embodiment of the present invention, the inductance of the wire harness between the driver for the seat belt retractor on the driver's seat side and the control device for the seat belt retractor, and the control for the seat belt retractor motor and the seat belt retractor on the passenger seat side are provided. The inductor of the wire harness between the devices is measured, and the center frequency of the PWM signal for driving the motor connected to the wire harness having a large inductance is set low.

  By measuring the inductance value of both wire harnesses and setting the center frequency of the PWM signal based on the measured inductance value, it is possible to more reliably reduce conduction noise.

  Since other configurations are the same as those in the first embodiment and the second embodiment, the illustration and description thereof are omitted.

  In the second embodiment, similarly to the first embodiment, the PWM frequency can be changed between the emergency operation mode and the normal operation mode.

  The above-described example is an example in the case where the present invention is applied to a motor control device for a seat belt retractor. However, the present invention is not limited to a motor control device for a seat belt retractor, but for driving a power window of a vehicle door. The present invention can also be applied to a motor control device that operates a movable part of a vehicle such as a motor control device for driving a side mirror or a motor control device for driving a side mirror.

  That is, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the gist of the present invention.

  DESCRIPTION OF SYMBOLS 100 ... Retractor (driver's seat), 102 ... Obstacle sensor, 104 ... Wheel speed sensor, 106 ... Collision judgment controller, 108 ... Brake assist device, 110 ... Seat belt drive controller (Driver's seat), 112 ... vehicle, 114 ... seat belt drive controller (passenger seat), 116 ... retractor (passenger seat), 200 ... motor, 202 ... passenger, 204 ... Seat, 206 ... Seat belt, 300 ... Power supply, 302 ... ECU, 304 ... Custom IC, 306 ... Power supply circuit, 308 ... CPU, 310 ... Motor drive unit, 312 ... Motor drive driver unit, 314 ... Current detection unit, 315 ... Vehicle wire harness, 316 ... A / D Converter, 318... PWM signal generator, 400a, 400b, 400c, 400d... MOSFET

Claims (5)

A motor drive unit that has a plurality of switching elements and drives a motor that operates a movable part of the vehicle;
An electric wire connected between the motor and the motor drive unit and supplying electric power for driving the motor from the motor drive unit;
A motor drive driver section for supplying a signal for controlling the plurality of switching elements to the motor drive section;
A PWM signal generation unit that generates a PWM signal for controlling the plurality of switching elements and supplies the PWM signal to the motor drive driver unit, and sets the center frequency of the PWM signal according to the inductance value of the electric line A PWM signal generator;
A motor control device for a vehicle movable part. The motor control device according to claim 1,
The motor includes a first motor and a second motor, and for each of the first motor and the second motor, the motor driving unit, the electric wire path, the motor driving driver unit, and the PWM signal generating unit, The center of the PWM signal supplied to the motor drive driver unit on the motor side connected to the electric line having a large inductance value among the electric line connected to the first motor and the electric line connected to the second motor A motor control device for a vehicle movable part, characterized in that the frequency is set lower than a center frequency of a PWM signal supplied to a motor drive driver part on a motor side connected to an electric line having a small inductance value. The motor control device according to claim 2,
The center frequency of the PWM signal supplied to the motor drive driver unit on the motor side connected to the long wire length of the wire route connected to the first motor and the wire route connected to the second motor, A motor control device for a vehicle movable unit, characterized in that the motor control unit is set lower than a center frequency of a PWM signal supplied to a motor drive driver unit on a motor side connected to an electric wire with a short line length. The motor control device according to claim 3,
The movable portion of the vehicle is a seat belt disposed on the driver's seat side and the passenger seat side, and the first motor and the second motor are motors for a seat belt retractor. Motor control device. The motor control device according to claim 4,
A vehicle collision determination unit for determining a vehicle collision, wherein the PWM signal generation unit operates in an emergency operation mode that is activated when the vehicle collision determination unit determines that the vehicle has collided; The normal operation mode that operates at normal time, such as storage, has two operation modes, and in the emergency operation mode, the central frequency of the PWM signal is maintained while maintaining the difference in the central frequency of the PWM signal. A motor control device for a vehicle movable portion, wherein the motor control device is set lower than the center frequency of the PWM signal in the normal operation mode.

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