JP2012224106A - Vehicle brake control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicle brake control device that early detects and suppresses a change in attitude of a vehicle body during turning, to enhance traveling stability of the vehicle.SOLUTION: The vehicle brake control device (ECU 16) performs stability control where oversteer is determined when the deviation between a target yaw rate calculated on the basis of speeds of wheels 5L, 5R, 6L, 6R detected by a wheel speed sensor 17 and a steering angle detected by a steering angle sensor 21 and an actual yaw rate detected by a yaw rate sensor 20 exceeds a threshold, and active brake is applied to the drive wheels (front 5L, 5R) located outside to suppress the change in attitude of the vehicle body during turning. When floating of the non-drive wheels (rear 6L, 6R) located inside is detected, the threshold for the deviation between the target yaw rate and the actual yaw rate to start the stability control is reduced.

Description

  The present invention relates to a vehicle brake control device that performs stability control that suppresses a change in posture of a vehicle body during turning by applying an active brake to driving wheels outside the turning when oversteer occurs during vehicle turning.

  A vehicle having a high center of gravity or a vehicle not provided with a stabilizer tends to have a large roll of the vehicle body when turning.

  Therefore, if the deviation between the target yaw rate calculated based on the speed of each wheel detected by the wheel speed sensor and the steering angle detected by the steering angle sensor and the actual yaw rate detected by the yaw rate sensor exceeds a threshold, oversteer Therefore, the stability control is performed to suppress the change in the posture of the vehicle body during turning by applying an active brake to the driving wheel outside the turning.

  In Patent Document 1, it is detected that the idling tendency has occurred in the driving wheels on the inner side of the turning from the speed change of the left and right driving wheels at the time of a sudden turning of the vehicle. Has been proposed to determine the rollover tendency of vehicles.

JP 11-254992 A

  However, even with a vehicle that performs stability control, the start of stability control may be delayed or the active braking force may be insufficient in a sudden oversteer state, and the vehicle body posture change cannot be effectively suppressed. There is sex.

  The present invention has been made in view of the above problems, and its object is to improve the running stability of the vehicle by detecting the posture change of the vehicle body at the time of turning the vehicle and suppressing the posture change early. An object of the present invention is to provide a brake control device for a vehicle.

  In order to achieve the above object, the invention described in claim 1 is detected by a target yaw rate and a yaw rate sensor calculated based on the speed of each wheel detected by the wheel speed sensor and the steering angle detected by the steering angle sensor. When the deviation from the actual yaw rate exceeds a threshold value, the vehicle brake control device performs stability control that suppresses the change in the posture of the vehicle body during turning by determining that it is oversteering and applying an active brake to the driving wheel outside the turning In this case, when the lift of the non-driving wheel inside the turn is detected, the threshold value of the deviation between the target yaw rate for starting the stability control and the actual yaw rate is changed to a small value.

  According to a second aspect of the present invention, in the first aspect of the present invention, the speed change of the non-driven wheel inside the turn detected by the wheel speed sensor is compared with the speed change of other wheels, and the difference between the two is a threshold value. At this time, it is determined that the non-driving wheel inside the turning has been lifted.

  The invention according to claim 3 is the invention according to claim 1 or 2, characterized in that the rear wheel is a non-driving wheel.

  According to a fourth aspect of the present invention, when the threshold value of the deviation between the target yaw rate at which the stability control is started and the actual yaw rate is changed to a small value in the invention according to any one of the first to third aspects, This is characterized in that an active brake force (braking force) larger than the active brake in the ability control is applied to the driving wheels on the outside of the turn.

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the vehicle speed calculated from the detection value of the wheel speed sensor, the lateral G detected by the lateral G sensor, and the steering angle sensor. When the detected steering angle exceeds each set value and the accelerator opening detected by the accelerator opening sensor is 0, when the lift of the non-driven wheel inside the turn is detected, the stability control is started. The threshold value of the deviation between the target yaw rate and the actual yaw rate is changed to a small value.

  According to the first aspect of the present invention, when the lift of the non-driven wheel inside the turn is detected, the threshold value of the deviation between the target yaw rate for starting the stability control and the actual yaw rate is changed to a small value, and the stability control is performed. Since the vehicle is started at an early stage, a change in the posture of the vehicle body can be suppressed at an early stage even in a sudden oversteer state, and the running stability of the vehicle can be improved. Such effects can be obtained simply by changing the deviation threshold value between the target yaw rate and the actual yaw rate at which stability control is started, and there is little change in control and no additional parts are required, resulting in increased costs. Is not invited.

  According to the second aspect of the present invention, it is possible to easily lift the non-driven wheel inside the turn by comparing the speed change of the non-driven wheel inside the turn detected by the wheel speed sensor with the speed change of the other wheels. And it can detect reliably.

  According to the third aspect of the present invention, the lift of the rear wheel inside the turning is easily and reliably detected by the difference in the speed of the rear wheel where the difference in speed appears between the inside and outside of the turning because it is not connected to the drive shaft. can do.

  According to the fourth aspect of the present invention, when the threshold value of the deviation between the target yaw rate for starting the stability control and the actual yaw rate is changed to a small value and the stability control is started early, the active in the normal stability control Since an active braking force (braking force) larger than that of the brake is applied to the driving wheel outside the turning, a large force in the direction opposite to the turning direction acts on the vehicle body to return the behavior of the vehicle. As a result, the change in the posture of the vehicle body when turning is more reliably suppressed.

  According to the fifth aspect of the present invention, the vehicle speed, the lateral G, and the lateral speed are set as conditions for changing the threshold value of the deviation between the target yaw rate for starting the stability control and the actual yaw rate to a small value and performing the stability control early. Since the steering angle exceeds each set value and the accelerator opening is 0 (accelerator operation is not performed), that is, the condition that the roll of the vehicle is likely to become large is added. It is possible to reliably suppress an increase in the roll of the vehicle.

1 is a configuration diagram of a brake system of a vehicle including a brake control device according to the present invention. It is a circuit diagram of a hydraulic control unit controlled by a brake control device according to the present invention. It is a top view which shows the driving | running track of the vehicle which is turning left. It is a top view of the vehicle which is turning left. It is a flowchart which shows the stability control procedure by the brake control apparatus which concerns on this invention.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a configuration diagram of a vehicle brake system including a brake control device according to the present invention. The illustrated brake device 1 includes a brake pedal 2 that swings in the vehicle front-rear direction around the upper end. The pedal 2 is connected to the master cylinder 4 via a brake booster 3 for reducing the driver's depression force at the time of brake operation, and the master cylinder 4 is braked according to the depression amount of the brake pedal 2 by the driver. Generate hydraulic pressure.

  By the way, the vehicle according to the present embodiment is a front wheel drive vehicle (FF vehicle), the left and right front wheels 5L and 5R are drive wheels, and the left and right rear wheels 6L and 6R are non-drive wheels (driven wheels), Each front wheel 5L, 5R and each rear wheel 6L, 6R is provided with a disc brake 7, and each disc brake 7 is constituted by a disc rotor 7a and a caliper 7b that can hold both sides of the disc rotor 7a. Yes. Each caliper 7 b of each disc brake 7 is connected to the master cylinder 4 via the brake piping lines 8, 9, 10, 11, the hydraulic pressure control unit 12, and the brake piping 13, 14 extending from the hydraulic pressure control unit 12. It is connected.

  The hydraulic pressure control unit 12 can generate a brake hydraulic pressure and activate a desired disc brake 7 (active braking) regardless of the brake operation by the driver depressing the brake pedal 2, This is provided with various valves v1 to v12 to be described later and pumps 23 and 24 (see FIG. 2) for generating hydraulic pressure. The pump motor 15 for driving the various valves v1 to v12 and the pumps 23 and 24 is a control unit ( Hereinafter, it is controlled by 16). Details of the configuration of the hydraulic pressure control unit 12 will be described later.

  The ECU 16 constitutes a brake control device according to the present invention. The ECU 16 includes a wheel speed sensor 17 provided on each of the front wheels 5L and 5R and the rear wheels 6L and 6R, and an external air temperature sensor. Air temperature sensor 18, lateral G sensor 19 that detects lateral G acting on the vehicle body, yaw rate sensor 20 that detects the yaw rate of the vehicle body, steering angle sensor 21 that detects the steering angle of the steering wheel, and pressure that detects the pressure of the master cylinder 4 The sensor 22 and the like are electrically connected.

  Next, details of the configuration of the hydraulic pressure control unit 12 will be described with reference to FIG.

  FIG. 2 is a circuit diagram of the hydraulic pressure control unit 12. The illustrated hydraulic pressure control unit 12 includes two pumps 23 and 24 driven by the pump motor 15. A hydraulic line 26 extending from the reservoir 25 is connected, and one brake pipe 13 extending from the master cylinder 4 is connected to the discharge side of the pump 23. The hydraulic line 26 is provided with a check valve 27 that allows only the flow toward the pump 23, and the brake pipe 13 includes a check valve 28 that allows only the flow from the pump 23 and the first cut valve v1. Is provided. Further, a return check valve 30 that allows only flow to the master cylinder 4 side is provided in a bypass line 29 that is connected to the brake pipe 13 by bypassing the first cut valve v1.

  The pressure sensor 22 is connected to the hydraulic pressure line 31 branched from the master cylinder 4 of the brake pipe 13 and the first cut valve v1, and the hydraulic pressure line 32 branched from the hydraulic pressure line 31 is hydraulic pressure. The line 26 is connected between the check valve 27 and the reservoir 25, and the hydraulic pressure line 32 is provided with a first pressure accumulation valve v2.

Further, an FL holding valve v3 and an FL pressure reducing valve v4 are provided in series on a hydraulic pressure line 33 branched from the first cut valve v1 and the check valve 28 of the brake pipe 13 and connected to the reservoir 25. The hydraulic pressure line 34 connected in parallel to the hydraulic pressure line 33 is provided with an RR holding valve v5 and an RR pressure reducing valve v6 in series. The brake pipe 8 (see FIG. 1) is branched from the FL holding valve v3 and the FL pressure reducing valve v4 of the hydraulic pressure line 33. The brake pipe 8 is connected to the disc brake 7 of the left front wheel (FL) 5L. Are connected to the caliper 7b (see FIG. 1).
With these configurations, the brake fluid pressure generated by the pump 23 is applied to the disc brake 7 of the left front wheel (FL) 5L, and is also applied to the left front wheel (FL) 5L by the FL holding valve v3 and the FL pressure reducing valve v4. The brake fluid pressure can be adjusted. Further, the brake pipe 11 (see FIG. 1) branches from between the RR holding valve v5 and the RR pressure reducing valve v6 of the hydraulic pressure line 34. This brake pipe 11 is a disc brake of the right rear wheel (RR) 6R. 7 caliper 7b (see FIG. 1). With these configurations, the brake fluid pressure generated by the pump 23 is applied to the disc brake 7 of the right rear wheel (RR) 6R, and is applied to the right rear wheel (RR) 6R by the RR holding valve v5 and the RR pressure reducing valve v6. The applied brake fluid pressure can be adjusted.

  On the other hand, a hydraulic pressure line 36 extending from the reservoir 35 is connected to the suction side of the other pump 24, and the other brake pipe 14 extending from the master cylinder 4 is connected to the discharge side of the pump 24. The hydraulic pressure line 36 is provided with a check valve 37 that allows only flow to the pump 24 side, and the brake pipe 14 has a check valve 38 that allows only flow from the pump 24 side and a second cut valve v7. Is provided. Further, a return check valve 40 that allows only flow to the master cylinder 4 side is provided in a bypass line 39 that is connected to the brake pipe 14 by bypassing the second cut valve v7.

  A hydraulic pressure line 41 branched from between the master cylinder 4 of the brake pipe 14 and the second cut valve v7 is connected between the check valve 37 of the hydraulic pressure line 36 and the reservoir 35. The hydraulic pressure line 41 Is provided with a second pressure accumulation valve v8.

  Further, an FR holding valve v9 and an FR pressure reducing valve v10 are provided in series on the hydraulic pressure line 42 branched from the second cut valve v7 and the check valve 38 of the brake pipe 14 and connected to the reservoir 35. An RL holding valve v11 and an RL pressure reducing valve v12 are provided in series on a hydraulic pressure line 43 connected in parallel to the hydraulic pressure line. The brake pipe 9 (see FIG. 1) is branched from the FR holding valve v9 and the FR pressure reducing valve v10 of the hydraulic pressure line 42. The brake pipe 9 is a disc brake 7 of the right front wheel (FR) 5R. Are connected to the caliper 7b (see FIG. 1). With these configurations, the brake fluid pressure generated by the pump 24 is applied to the disc brake 7 of the right front wheel (FR) 5R, and is also applied to the right front wheel (FR) 5R by the FR holding valve v9 and the FR pressure reducing valve v10. The brake fluid pressure can be adjusted. Further, the brake pipe 10 (see FIG. 1) is branched from the RL holding valve v11 and the RL pressure reducing valve v12 of the hydraulic pressure line 43. This brake pipe 10 is a disc brake of the left rear wheel (RL) 6L. 7 caliper 7b (see FIG. 1). With these configurations, the brake fluid pressure generated by the pump 24 is applied to the disc brake 7 of the left rear wheel (RL) 6L, and the RL holding valve v11 and the RL pressure reducing valve v12 are applied to the right front wheel (FR) 5R. The brake fluid pressure can be adjusted.

  Thus, the hydraulic pressure control unit 12 having the circuit configuration as described above is controlled by the ECU 16. Hereinafter, as an example of the control, the stability control when the vehicle turns to the left will be described with reference to FIGS. This will be described below with reference.

  FIG. 3 is a plan view showing a traveling track of a vehicle turning left, FIG. 4 is a plan view of the vehicle turning left, and FIG. 5 is a flowchart showing a stability control procedure by the brake control device according to the present invention.

  When the driver steers the steering handle 50 (see FIG. 4) to the left to turn the left curve (step S1 in FIG. 5), the ECU 16 detects the front wheels 5L and 5R and the rear wheels 6L detected by the respective wheel speed sensors 17. The target yaw rate (acceleration in the rotational direction) intended by the driver is calculated from the rotational speeds of 6R and the steering angle of the steering wheel 50 detected by the steering angle sensor 21. Then, the ECU 16 determines the actual yaw rate detected by the yaw rate sensor 20 (the speed at which the rotation angle changes in the turning direction generated in the actual vehicle) and the target yaw rate (estimated from the driver's operation or the like). Compared with the desired speed of change of the rotation angle of the vehicle in the turning direction), the state where the front part of the vehicle W enters the inside of the curve on the left curve as shown by the broken line in FIG. State) or when the rear portion of the vehicle W starts to flow outward (right side), the relationship of actual yaw rate> target yaw rate is established.

  Therefore, the ECU 16 determines whether or not the deviation between the actual yaw rate and the target yaw rate has exceeded a predetermined threshold (threshold that is smaller than the threshold for starting normal stability control) separately from the normal stability control. When the determination is made (step S2) and the deviation exceeds the threshold value (when the determination result at step S2 is Yes), it is determined that the state of the vehicle W tends to be left-turn oversteer, and then the inside of the turn (left side) ) Is determined whether or not the left rear wheel 6L, which is a non-driving wheel, is lifted (step S3). Here, in the determination of the lift of the left rear wheel 6L inside the turn, the speed change of the left rear wheel 6L detected by the wheel speed sensor 17 is compared with the speed change of the right rear wheel 6R, and the difference between the two is a threshold value. It is assumed that the left rear wheel 6L is lifted at the above time. In this case, since the rear wheels 6L and 6R, which are non-drive wheels, are not connected to the drive shaft, the speed difference between the two appears remarkably, and the lift of the left rear wheel 6L is easily and reliably detected by the speed difference between the two. be able to. In FIG. 5, “normal stability control” (step S10) is shown for convenience of explanation, but “normal stability control” is a control different from the control of the present invention described in FIG. Is controlled and operated.

  If the left rear wheel 6L has not lifted up (if the determination result in step S3 is No), it is determined that it is not necessary to start the stability control of the present invention, and normal stability is maintained. The control is left as it is (step S10), the process is terminated to perform normal stability control using a normal threshold value, and the process returns to step S2 to repeat the control of the invention (step S11). That is, when the normal rearward threshold is reached without raising the left rear wheel 6L thereafter, the ECU 16 closes the second cut valve v7 and the RL holding valve v11FR as shown in FIG. Open v8 and FR holding valve v9. Then, the hydraulic pressure generated by driving the pump 24 by the pump motor 15 is supplied to the caliper 7b of the disc brake 7 of the right front wheel 5R via the path indicated by the thick line in FIG. 2, and therefore an active brake is applied to the right front wheel 5R. As shown in FIG. 4, since an outward moment (a moment in the direction opposite to the turning direction) is generated in the vehicle W, the actual yaw rate is reduced and the front portion of the vehicle W enters the inside of the curve (so-called overshoot). Steer state) or the trajectory through which the rear part of the vehicle W flows outward is corrected, and the vehicle W can stably turn on the left curve without causing a large change in posture as shown by the solid line in FIG.

  On the other hand, if the left rear wheel 6L is lifted (if the determination result in step S3 is Yes), the following determination process is performed to confirm the state of the vehicle W. That is, whether the vehicle speed is 75 km / h or more (step S4), whether the lateral G (lateral acceleration of the vehicle) is 0.6 G or more (step S5), and the steering angle is 90 ° or more. Whether or not there is (step S6) and whether or not the accelerator opening is 0% or more (step S7) is determined, and if all of them are satisfied (the determination results of steps S4 to S7 are all Yes) If it is determined that there is a high possibility that stability control is required for the vehicle W, the threshold value of the deviation between the target yaw rate for starting the stability control and the actual yaw rate is changed to a value smaller than usual. (Step S8), stability control is started earlier than usual (execution of early stability control) (Step S9), and the process ends. Here, when the threshold value of the deviation between the target yaw rate at which the stability control is started and the actual yaw rate is changed to a small value and the stability control is started early, the active braking force is larger than the active braking in the normal stability control. (Braking force) is applied to the right front wheel 5R outside the turn. For this reason, a large force in a direction opposite to the turning direction acts on the vehicle body to increase the moment for returning the behavior of the vehicle W, and the change in the posture of the vehicle body during the turning is further reliably suppressed.

  On the other hand, when at least one of the determinations in steps S4 to S7 is No, normal stability control is performed on the assumption that the vehicle W is unlikely to require stability control. (Step S10), the process ends to perform normal stability control using a normal threshold (Step S11).

  As described above, in the present embodiment, when the lift of the left rear wheel 6L or the right rear wheel 6R that is the non-drive wheel inside the turning is detected when the vehicle W is turning, the target yaw rate for starting the stability control is Since the stability threshold control is started early by changing the threshold value of deviation from the actual yaw rate to a small value, the vehicle W The running stability of can be improved. Such effects can be obtained simply by changing the deviation threshold value between the target yaw rate and the actual yaw rate at which stability control is started, and there is little change in control and no additional parts are required, resulting in increased costs. Is not invited.

1 Brake Device 2 Brake Pedal 3 Brake Booster 4 Master Cylinder 5L, 5R Front Wheel (Drive Wheel)
6L, 6R Rear wheel (non-drive wheel)
7 Disc brake 8-11 Brake piping 12 Hydraulic control unit 13, 14 Brake piping 15 Pump motor 16 ECU (brake control device)
17 Wheel speed sensor 19 Lateral G sensor 20 Yaw rate sensor 21 Steering angle sensor 23, 24 Pump 50 Steering wheel W Vehicle

Claims (5)

When the deviation between the target yaw rate calculated based on the speed of each wheel detected by the wheel speed sensor and the steering angle detected by the steering angle sensor and the actual yaw rate detected by the yaw rate sensor exceeds a threshold, it is determined as oversteer. In a vehicle brake control device that performs stability control that suppresses a change in posture of the vehicle body during turning by applying an active brake to the driving wheel outside the turning,
A brake control device for a vehicle, wherein when a lift of a non-driving wheel inside a turn is detected, a threshold value of a deviation between a target yaw rate for starting the stability control and an actual yaw rate is changed to a small value.   Comparison between the speed change of the non-driven wheel inside the turn detected by the wheel speed sensor and the speed change of other wheels, and when the difference between the two is equal to or greater than the threshold value, the non-drive wheel inside the turn is lifted The vehicle brake control device according to claim 1, wherein:   3. The vehicle brake control device according to claim 1, wherein the rear wheel is a non-driving wheel.   When the deviation threshold value between the target yaw rate for starting the stability control and the actual yaw rate is changed to a small value, an active brake larger than the active brake in the normal stability control is applied to the driving wheel outside the turn, The vehicle brake control device according to any one of claims 1 to 3. The vehicle speed calculated by the detection value of the wheel speed sensor, the lateral G detected by the lateral G sensor, and the steering angle detected by the steering angle sensor exceed the set values, and are detected by the accelerator opening sensor. If the lift of the non-driven wheel inside the turn is detected when the accelerator opening is 0, the deviation threshold value between the target yaw rate for starting the stability control and the actual yaw rate is changed to a small value. Item 5. The vehicle brake control device according to any one of Items 1 to 4.

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