JP2009190419A - Brake control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brake control device capable of achieving both noise reduction and heating suppression while providing a necessary braking force. <P>SOLUTION: This brake control device comprises a frequency control part for changing a frequency for PWM control. The frequency control part sets the PWM frequency above an audible zone at least during automatic brake control, and sets the PWM frequency lower than the present value when performing the PWM control continuously at the frequency above the audible zone and predetermined requirements are satisfied during automatic brake control. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to heat generation and noise reduction of an electric motor in a vehicle brake control device.

Conventionally, in a brake control device that obtains braking force by driving a pump with an electric motor, the PWM frequency of the electric motor control is set to be higher than the audible frequency according to the vehicle situation, and the heat generation of the drive element and the electric motor Noise is reduced. During normal braking where quietness is required, the frequency is set to be higher than the audible frequency to reduce noise, and during sudden braking where quietness is not required, the frequency is reduced to the audible range, thereby preventing heat generation of the drive element.
JP 2000-168545 A

  However, in the above prior art, when the braking force is generated by suppressing the frequency within the audible range, the longer the operation time of the electric motor, the longer the noise is generated, which causes the driver to feel uncomfortable. It was. On the other hand, when the electric motor drive time is extended in a state where the frequency is set to be higher than the audible range, there is a problem that the amount of heat generated by the drive element increases.

  In particular, in recent ACC (adaptive cruise control) control, there is a situation in which normal braking, which is not sudden braking, is continued for a long time and the vehicle is stopped while slowly decelerating, which may increase the amount of heat generation. Therefore, it has been a problem to achieve both noise reduction and heat generation suppression while obtaining a necessary braking force.

  The present invention has been made paying attention to the above problems, and an object of the present invention is to provide a brake control device that achieves both noise reduction and heat generation suppression while obtaining a necessary braking force.

  In order to achieve the above-described object, the present invention includes a frequency control unit that changes a frequency of PWM control, and the frequency control unit sets the PWM frequency to an audible range or more at least during automatic brake control, and When the PWM control is continuously performed at a frequency equal to or higher than the audible range at the time of brake control, when a predetermined condition is satisfied, the PWM frequency is changed to be lower than the current value.

  Therefore, it is possible to provide a brake control device that achieves both noise reduction and heat generation suppression while obtaining a necessary braking force.

  Hereinafter, the best mode for realizing the brake control device of the present invention will be described based on the embodiments shown in the drawings.

[Brake control system configuration]
FIG. 1 is a system configuration diagram of the brake control device of the present application. The brake control device includes a control unit 1, a brake unit 2, a G sensor 3, a wheel speed sensor 4, a yaw rate sensor 5, a temperature monitor 6, and a current monitor 7. The temperature monitor 6 and the current monitor 7 monitor the temperature and current of the drive element 14 (see FIG. 2) of the electric motor M provided in the brake unit 2.

  The control unit 1 outputs a control command to the brake unit 2 based on the wheel speed VW (FL to RR), the longitudinal acceleration G, the yaw rate Y, the temperature monitor value, the current monitor value, and the command from the adaptive cruise controller 10. Based on this command, the brake unit 2 optimally controls the braking force of each wheel FL, FR, RL, RR. The longitudinal acceleration G may be a differential value of the vehicle speed.

[Control block diagram]
FIG. 2 is a control block diagram of the control unit 1. The control unit 1 includes an electric motor control determination unit 11, a temperature calculation unit 12, a frequency control unit 13, and a drive element 14.

  The electric motor control determination unit 11 performs ACC (adaptive cruise control) control based on the longitudinal acceleration G, the wheel speed VW (FL to RR), the yaw rate Y, and the command from the adaptive cruise controller 10, or normal ABS. (Anti-lock brake control) and VDC (vehicle behavior control) are determined.

  The temperature calculation unit 12 monitors the temperature of the drive element 14 based on the detection value of the temperature monitor 6 or the current monitor 7. Current-based monitoring is performed using the current integration amount-temperature map of FIG.

  The frequency control unit 13 determines the PWM frequency f of the electric motor M corresponding to each control of ACC, ABS, and VDC. At that time, the PWM frequency f is changed based on the temperature of the drive element 14 monitored by the temperature calculation unit 12. If the temperature is high, the frequency f is lowered below the audible range, and if the temperature is not high, the frequency f is set above the audible range.

  The drive element 14 drives the electric motor M based on the determined PWM frequency f.

[Hydraulic circuit]
FIG. 4 is a hydraulic circuit diagram of the brake unit 2. The brake unit 2 is a tandem hydraulic circuit having P and S systems. The pump P is a one-way pump and is driven by an electric motor M. The suction side of the pump P is connected to the master cylinder 20 through oil passages 51 and 52 and in-side gate valves 21 and 22, and the discharge side is connected to each wheel cylinder W / through oil passages 53 to 56 and in-valves 25 to 28. Connect to C (FL to RR).

  The oil passages 53 to 56 are connected to the reservoirs 41 and 42 through the out valves 29 to 32 and the oil passages 57 and 58, respectively, and are connected to the suction side of the pump P together with the oil passages 51 and 52. Further, the pump P side of the in valves 25 to 28 is connected to the master cylinder 20 via the oil passages 61 and 62 and the out side gate valves 23 and 24.

  The out-side gate valves 23 and 24 are provided in parallel with check valves 33 and 34 that prevent backflow to the master cylinder 20. In addition, check valves 35 to 38 for preventing backflow to the wheel cylinders W / C (FL to RR) are provided in parallel to the in valves 25 to 28, respectively.

(When ACC is increased)
When the pressure is increased, the in-side gate valves 21 and 22 and the in-valves 25 to 28 are opened, the out valves 29 to 32 and the out-side gate valves 23 and 24 are closed, and the pump P is driven. The hydraulic oil is pumped from the master cylinder 20 by the pump drive, and is introduced into each wheel cylinder W / C (FL to RR) through the oil passages 51 and 52 and the oil passages 53 to 56 to increase the pressure.

(When ACC is decompressed)
During decompression, the out-side gate valves 23 and 24 are opened.

[Electric motor control flow]
(Main flow)
FIG. 5 is a main flow of electric motor frequency control.

  In step S101, it is determined whether or not there is a drive request for each control of the electric motor M in ABS, VDC, and ACC. If YES, the process proceeds to step S1-3, and if NO, the process proceeds to step S102.

  In step S102, since there is no drive request for the electric motor M, the electric motor M is turned off and the control is terminated.

  In step S103, it is determined whether or not there is an ACC control signal. If YES, the process proceeds to step S200, and if NO, the process proceeds to step S104.

In step S104, PWM frequency f a normal rather than ACC ABS of the electric motor M, and set to a frequency _{f L} of the VDC, the control is ended. Note that the frequency f _{L at} this time is set below the audible range.

  In step S200, frequency control in ACC is executed and the control is terminated.

(PWM frequency control flow in ACC)
FIG. 6 is a flow of electric motor PWM frequency control in ACC (adaptive cruise control). Here, each threshold value is set to a relationship of T1 <T2 <T3.

  In step S201, the monitored monitor temperature T is read, and the process proceeds to step S202.

  In step S202, it is determined whether monitor temperature T <first threshold value T1. If YES, the process proceeds to step S203, and if NO, the process proceeds to step S204.

In step S203, since the temperature of the drive element 14 is low, the PWM frequency f of the electric motor M is set to a high frequency f _H that is the audible range limit or higher, and the control is terminated.

  In step S204, it is determined whether or not first threshold value T1 ≦ monitoring temperature T <second threshold value T2. If YES, the process proceeds to step S205, and if NO, the process proceeds to step S206.

In step S205, since the temperature of the drive element 14 is slightly high, the PWM frequency f of the electric motor M is gradually decreased from the current value according to the following equation (1), and the control is terminated.
f = high frequency f _H −k1 · monitor temperature T (1)
Note that k1 is a constant.

  In step S206, it is determined whether or not second threshold value T2 ≦ monitoring temperature T <third threshold value T3. If YES, the process proceeds to step S207, and if NO, the process proceeds to step S208. The third threshold value T3 is the temperature of the driving element 14 that can continue driving the electric motor M.

The temperature of step S207 in the drive element 14 is further increased, forcing to reduce the PWM frequency f of the electric motor M to a constant value f _L, the control is ended.

  In step S208, since the temperature of the drive element 14 exceeds the drive continuation possible temperature T3, the electric motor M is stopped and the process proceeds to step S209.

  In step S209, the fail lamp is turned on, and the process proceeds to step S210.

  In step S210, the monitor temperature T is read again, and the process proceeds to step S211.

  In step S211, it is determined whether monitor temperature T ≦ electric motor drive allowable temperature Ton. If YES, the process proceeds to step S213 assuming that the temperature of the drive element 14 has sufficiently decreased, and if NO, the process proceeds to step S212. To do.

In step S212, since the temperature of the drive element 14 has not yet decreased sufficiently, it is determined whether or not the ACC control signal is output at this time.
If YES, it is expected that the drive command for the electric motor M is output by ACC, but the monitor temperature T is still high, so the process returns to step S208 and waits for the temperature to decrease again.
If NO, the drive command for the electric motor M by ACC is not output, and the process proceeds to step S213.

  In step S213, the fail lamp is turned off and the control is terminated.

[Time-dependent change of PWM frequency control in ACC]
FIG. 7 is a time chart of electric motor PWM frequency control in ACC.

(Time t1)
At time t1, a drive command for the electric motor M by ACC is output, and the monitor temperature T is equal to or lower than the first threshold value T1, so the electric motor drive frequency f is set to f _H (steps S202 → S203). Note that the audible area is generally 5 or 10 Hz to 15 or 20 kHz, and f _H = 20 kHz. In addition, the monitor temperature T rises as the drive element 14 is driven.

(Time t2)
At time t2, the monitor temperature T becomes the first threshold value T1, and the PWM frequency f is decreased from the current value (steps S204 → S205).

(Time t3)
Monitoring the temperature T = second threshold T2 next at time t3, PWM frequency f is forcibly reduced to _{f L} (step S206 → S207). The frequency f _{L at} this time is 4 or 5 Hz below the audible range.

(Time t4)
At time t4, monitor temperature T = third threshold value T3 (temperature at which electric motor M can continue to be driven), and electric motor M is stopped (steps S206 → S208). For this reason, the PWM frequency f is also zero.

(Time t5)
At time t5, the monitor temperature T becomes equal to or lower than the electric motor drive allowable temperature Ton, and the drive of the electric motor M is resumed.

[Effect of Example 1]
(1) A frequency control unit 13 that changes the frequency f of the PWM control is provided, and at least during automatic brake control, the PWM frequency f is set to an audible range or higher (f _H = 20 kHz),
During automatic brake control, when PWM control is continuously performed at a frequency above the audible range, when a predetermined condition is satisfied, the PWM frequency f is changed to be lower than the current value.

  Accordingly, it is possible to provide a brake control device that achieves both noise reduction and heat generation suppression while obtaining a necessary braking force. In addition, the necessity of providing other members as a heat dissipation measure is reduced, and an increase in the size of the apparatus can be avoided.

  (2) During automatic brake control, when PWM control is continuously performed at a frequency higher than the audible range, if a predetermined condition (monitor temperature T ≧ third threshold value T3) is satisfied, The drive of the motor M was stopped.

  Thereby, the malfunction by heat_generation | fever can be prevented reliably.

  (3) A temperature calculation unit 12 that calculates the temperature (monitor temperature T) of the electric motor M or the drive element 14 is provided, and the predetermined condition is that the calculated monitor temperature T is a predetermined threshold value (first to third). The threshold values T1 to T3 and the electric motor drive allowable temperature Ton) were exceeded.

  By using the preset temperature threshold values T1 to T3 and Ton, the determination condition can be reliably detected.

(4) When the predetermined condition is canceled (monitor temperature T <first threshold value T1 or monitor temperature T ≦ electric motor drive allowable temperature Ton), the frequency control unit 13 sets the PWM frequency f to an audible range or more ( f _H = 20 kHz).

  Thereby, the control which ensured silence can be continued.

Example 2 will be described. The basic configuration is the same as that of the first embodiment. Define the second threshold value T2 in the first embodiment, when a third threshold value T3> monitoring the temperature T ≧ second threshold T2 was forcibly reduced to f _L the PWM frequency f (Steps S206 and S207).

  On the other hand, the second embodiment is different in that steps S206 and S207 in the first embodiment are omitted, and the PWM frequency f is always decreased when the first threshold value T1 <the monitor temperature T <the third threshold value T3.

[PWM Frequency Control Flow in Embodiment 2]
FIG. 8 is a flowchart of electric motor PWM frequency control in the second embodiment. If steps S206 and S207 of the first embodiment are omitted and NO is determined in step S204 ′, the process directly proceeds to step S208. Accordingly, there is no change in the control around the second threshold value T2. Since others are the same as those of the first embodiment, a description thereof is omitted.

[Time-dependent change of PWM frequency control in Embodiment 2]
FIG. 9 is a time chart of the electric motor PWM frequency control in the second embodiment.

(Time t11)
This is similar to the time t1 in the first embodiment.

(Time t12)
At time t12, the monitor temperature T becomes the first threshold value T1, and the PWM frequency f is decreased (steps S204 → S205).
In the second embodiment, the decreasing gradient when gradually decreasing is set smaller than that in the first embodiment. The decreasing slope of the PWM frequency f at T1 ≦ monitoring value T <T2 is expressed as f = f _H −k1 · T (1) as in the expression (1) of the first embodiment.
However, the decreasing gradient is changed by changing the coefficient k.
That is, in Example 2, a coefficient k2 smaller than the coefficient of Example 1 is set,
f = f _H −k1 · T (2)
The PWM frequency f is gradually decreased using equation (2). Thereby, the decreasing gradient of the PWM frequency f is reduced.

(Time t13)
At the time t13, the monitor temperature T becomes the second threshold value T2, but in the second embodiment, the PWM frequency f is continuously decreased according to the equation (2).

(Time t14, t15)
This is similar to the times t4 and t5 of the first embodiment.

[Effect of Example 2]
In the second embodiment, the same effects as in the first embodiment can be obtained with a simple control configuration. Further, since the change of the PWM frequency f becomes smooth, the quietness is further improved.

Example 3 will be described. The basic configuration is the same as that of the first embodiment. In the second embodiment, steps S206 and S207 are omitted, but in the third embodiment, steps S204 and S205 are omitted. Step S204, S205 of with the omission, decreasing the PWM frequency f is not performed, it reduces the PWM frequency f to forcibly _{f L} at the stage of reaching the first threshold T1.

[PWM Frequency Control Flow in Embodiment 3]
FIG. 10 is a flowchart of electric motor PWM frequency control in the third embodiment. Steps S204 and S205 of the first embodiment are omitted, and if NO is determined in step S202, the process directly proceeds to step S206 ′. Therefore, as in the second embodiment, there is no change in the control around the second threshold value T2. Since others are the same as those of the first embodiment, a description thereof is omitted.

[Time-dependent change of PWM frequency control in Embodiment 3]
FIG. 11 is a time chart of the electric motor PWM frequency control in the third embodiment.

(Time t21)
This is similar to the time t1 in the first embodiment.

(Time t22)
At time t22, the monitor temperature T becomes the first threshold value T1, and the PWM frequency f is forcibly lowered to f _L (4 to 6 Hz below the audible range).

(Time t23)
At the time t23, the monitor temperature T = the second threshold value T2, but in the third embodiment, f = f _L is maintained.

(Time t24, t15)
This is similar to the times t4 and t5 of the first embodiment.

[Effect of Example 3]
In the third embodiment, the same effect as that of the first embodiment can be obtained with a simple control configuration.

  Example 4 will be described. In the second embodiment, steps S206 and S207 are omitted, but in the fourth embodiment, steps S204 to S207 are omitted. Therefore, the rotation of the electric motor M is stopped when the first threshold value T1 is reached.

[PWM Frequency Control Flow in Embodiment 4]
FIG. 12 is a flowchart of electric motor PWM frequency control in the fourth embodiment. As in the second and third embodiments, there is no change in the control around the second threshold value T2. Further, since the electric motor M is stopped when the first threshold value T1 is exceeded, the control does not change before and after the third threshold value T3. Since others are the same as those of the first embodiment, a description thereof is omitted.

[Time-dependent change of PWM frequency control in Embodiment 4]
FIG. 13 is a time chart of the electric motor PWM frequency control in the fourth embodiment.

(Time t31)
This is similar to the time t1 in the first embodiment.

(Time t32)
At time t32, the monitor temperature T becomes the first threshold value T1, and the electric motor M is stopped. For this reason, the PWM frequency f is also zero.

(Time t33, t34)
At the time t33, the monitor temperature T becomes the second threshold value T2, but in the fourth embodiment, since the electric motor M is stopped, f remains zero. The same applies to time t34.

(Time t35)
This is similar to the time t5 in the first embodiment.

[Effect of Example 4]
In the fourth embodiment, the same effect as that of the first embodiment can be obtained with a simple control configuration. In particular, the fourth embodiment can be simplified most in each embodiment.

[Other embodiments]
The best mode for carrying out the present invention has been described based on each embodiment, but the specific configuration of the present invention is not limited to each embodiment and does not depart from the gist of the invention. Such design changes are included in the present invention.

It is a system configuration figure of a brake control device. 3 is a control block diagram of the control unit 1. FIG. It is an electric current integration amount-temperature map. 3 is a hydraulic circuit diagram of the brake unit 2. FIG. It is a main flow of electric motor frequency control. It is a flow of electric motor PWM frequency control in ACC. It is a time chart of the electric motor PWM frequency control in ACC. It is a flow of the electric motor PWM frequency control in the second embodiment. 6 is a time chart of electric motor PWM frequency control in Embodiment 2. 10 is a flow of electric motor PWM frequency control in the third embodiment. 12 is a time chart of electric motor PWM frequency control in Embodiment 3. It is a flow of the electric motor PWM frequency control in the fourth embodiment. 10 is a time chart of electric motor PWM frequency control in Embodiment 4.

Explanation of symbols

1 control unit 12 the temperature calculating unit 13 a frequency control unit 14 drive element f PWM frequency _{f H} High Frequency (audible range frequencies above)
M Electric motor P Pump T Monitor temperature (temperature)
T1 to T3 First to third threshold values (predetermined threshold values)
Ton Electric motor drive allowable temperature (predetermined threshold)
VW (FL to RR) Wheel speed (vehicle environment)
G Front and rear G (vehicle environment)
Y Yaw rate (vehicle environment)
W / C (FL to RR) Wheel cylinder

Claims (4)

A pump that increases the hydraulic pressure of the wheel cylinder;
An electric motor for driving the pump;
A driving element for driving the electric motor;
A control unit that drives the drive element by PWM control, controls the electric motor, and performs automatic brake control based on the surrounding environment of the host vehicle;
Have
The control unit includes a frequency control unit that changes a frequency of the PWM control,
The frequency control unit
At least during the automatic brake control, the PWM frequency is set to an audible range or higher,
When the PWM control is continuously performed at a frequency of the audible range or higher during the automatic brake control, and the predetermined condition is satisfied, the PWM frequency is changed to be lower than the current value. Brake control device. A pump that increases the hydraulic pressure of the wheel cylinder;
An electric motor for driving the pump;
A driving element for driving the electric motor;
A control unit that drives the drive element by PWM control, controls the electric motor, and performs automatic brake control based on the surrounding environment of the host vehicle;
Have
The control unit includes a frequency control unit that changes a frequency of the PWM control,
The frequency control unit
At least during the automatic brake control, the PWM frequency is set to an audible range or higher,
When the automatic brake control is performed and the PWM control is continuously performed at a frequency equal to or higher than the audible range, the drive of the electric motor is stopped when a predetermined condition is satisfied. Brake control device. The brake control device according to claim 1 or 2,
A temperature calculation unit for calculating the temperature of the electric motor or the drive element;
The predetermined condition is a case where the calculated temperature exceeds a predetermined threshold value. The brake control device according to any one of claims 1 to 3,
The said frequency control part sets the said PWM frequency more than the said audible area | region, when the said predetermined conditions are cancelled | released. The brake control apparatus characterized by the above-mentioned.

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