JP2965375B2 - Anti-skid control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-skid control device for controlling a braking force applied to wheels during braking of a vehicle to prevent locking of the wheels, and more particularly to independently controlling braking forces applied to both front wheels of the vehicle. At the same time, for the control of the braking force of each wheel on both sides behind the vehicle, an anti-skid control device that switches between each wheel independent control that controls each wheel independently and low-speed selection control according to the rotation state of the low-speed wheel Related.

[0002]

2. Description of the Related Art It is well known that, when wheels are locked during sudden braking of a vehicle, running may become unstable or steering characteristics may be impaired depending on road surface conditions. For this reason,
2. Description of the Related Art Anti-skid devices that control braking force by reducing, increasing, or maintaining brake fluid pressure on a wheel cylinder of each wheel so that the wheels do not lock during sudden braking are widely used. Anti-skid control of wheels includes rear wheel control and front and rear wheels, that is, four-wheel control. The former prevents the rear wheels from being locked, thereby ensuring running stability and shortening the braking distance. According to the latter, the front wheels can be further prevented from being locked, so that good steering characteristics can be maintained.

In the above-described four-wheel control anti-skid control device, braking force is applied to both rear wheels of the vehicle, that is, the rear two wheels at the same time. Low-speed selection control by a low-speed wheel that controls a braking force so that the wheel is not locked in accordance with the rotation state of the side wheel, that is, so-called low-select control is performed. Thereby, for example, even when one of the rear two wheels is on a road surface having a high friction coefficient and the other is on a road surface having a low friction coefficient, traveling stability can be ensured. Thus, the front wheels are controlled independently of each other by independently controlling the braking force on each wheel, and the rear wheels are controlled by the low speed selection control mode in which both wheels are simultaneously controlled by the braking force on the low speed wheel. Is controlled.

[0004] With respect to such an anti-skid control device, Japanese Patent Application Laid-Open No. Hei 1-301450 discloses that the anti-skid control device is mounted on a constantly all-wheel-drive vehicle having a viscous joint between a front wheel and a rear wheel and has a high road surface friction coefficient. When the sum of the rear wheel slips is small, the four wheels are independent, and when the sum of the rear wheel slips is large, the front wheels are independent regardless of the friction coefficient. A device has been proposed in which each device is controlled based on information from a computer.

[0005]

According to the anti-skid control in the apparatus described in the above publication, for example, when a vehicle turns on a road surface having a high coefficient of friction, as is well known, the wheel speed differs between the inner and outer wheels when the vehicle turns. Therefore, the sum of the rear wheel slip amounts becomes large, and the low-speed inner wheel braking force is selected by low selection. In this case, despite the road surface having a high friction coefficient, the braking force of the outer wheel cannot be sufficiently obtained, and the braking distance may be extended.

Accordingly, an object of the present invention is to appropriately switch between a low speed selection control mode and each wheel independent control mode for wheels on both rear sides of a vehicle according to a turning state of the vehicle, thereby shortening a braking distance.

[0007]

In order to achieve the above object, the present invention, as shown schematically in FIG. 1, shows that the braking force of each of the rear wheels RR and RL on the rear side of the vehicle is reduced by a lower speed wheel. Control mode switching means 105 that switches between a low speed selection control mode for controlling according to the rotation state of each wheel and an individual wheel independent control mode for independently controlling the braking force of each wheel RR, RL according to the rotation state of each wheel RR, RL. And the control mode switching means 105
The braking force of each wheel RR, RL on the rear side of the vehicle is controlled according to the output of the vehicle, and each wheel FR, FR on the front both sides of the vehicle.
Braking force control means 106 for independently controlling the braking force of FL
It has. Then, a steering angle detecting means 101 for detecting the steering angle of the vehicle, a yaw rate detecting means 102 for detecting the yaw rate of the vehicle, and a vehicle speed for detecting the speed of the vehicle
And detection means (not shown), the first comparison means 103 for comparing the detected steering angle of the steering angle detecting means 101 and the criteria angle,
Based on the vehicle speed detected by the vehicle speed detection means, the vehicle
Higher vehicle speeds are lower than lower vehicle speeds
It sets the reference value, the detection yaw rate of the yaw rate detecting means includes a second comparison means 104 for comparing with the reference value,
The control mode switching means 105 controls the low-speed selection control mode only when the detected steering angle is smaller than the reference angle and the detected yaw rate is equal to or larger than the reference value, according to the comparison result of the first comparison means 103 and the second comparison means 104. In other cases, each wheel is controlled independently.

In the anti-skid control device, the reference angle set by the first comparing means is also equal to the reference angle .
As with the reference value of the yaw rate, it may be variable according to the speed of the vehicle.

[0009]

In the anti-skid control device having the above structure, when the vehicle turns, the turning state at that time is detected by the steering angle detecting means 101 and the yaw rate detecting means 102, and the first comparing means 103 and the second comparing means respectively. It is input to the means 104. In the first comparing means 103, the output of the steering angle detecting means 101 is compared with the reference angle, and the comparison result is output to the control mode switching means 105. In the second comparing means 104, a vehicle speed detecting means (not shown)
If the vehicle speed is high based on the detected vehicle speed
A lower reference value is set as compared to the case where both speeds are low, and the output of the yaw rate detection means 102 is compared with this reference value,
The comparison result of the yaw rate detecting means is the control mode switching means 1
05 is input. According to these comparison results, the control mode switching means 105 switches between the low speed selection control mode and the individual wheel independent control mode, and the wheels R on both rear sides of the vehicle are switched.
The braking forces of R and RL are controlled. That is, according to the comparison result of the first comparing means 103 and the second comparing means 104, the low speed selection control mode is set only when the detected steering angle is smaller than the reference angle and the detected yaw rate is equal to or more than the reference value. In this case, each wheel is controlled independently. In the former control mode, the braking force on the wheels RR and RL is simultaneously controlled by the braking force control means 106 in accordance with the rotation state of the low-speed wheels, so that the stability of the vehicle on a so-called split road is maintained. In the latter control mode at the time of turning the vehicle, the braking force on the wheels RR and RL is controlled independently of each wheel, and sufficient braking force is secured also on the outer wheels, so that the braking is lower than in the low speed selection control mode. The distance is reduced.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows an anti-skid control device according to one embodiment of the present invention, which includes a master cylinder 2a and a booster 2b.
And a hydraulic pressure passage connecting the hydraulic pressure generating device 2 driven by the brake pedal 3 and the wheel cylinders 51 to 54 disposed on the wheels FR, FL, RR, RL. The reservoirs 23 and 24 and the solenoid valves 31 to 34 are interposed. The wheel FR indicates the front right wheel as viewed from the driver's seat, the wheel FL indicates the front left wheel, the wheel RR indicates the rear right wheel, and the wheel RL indicates the rear left wheel. As is apparent from FIG. Piping is configured.

Electromagnetic valves 31 and 34 are interposed in a hydraulic passage connecting one output port of the master cylinder 2a and the wheel cylinders 51 and 54, respectively, and a pump 21 is interposed between the two. Similarly, solenoid valves 32 and 33 are interposed in hydraulic passages connecting the other output port of the master cylinder 2a and the wheel cylinders 52 and 53, respectively.
2 are interposed. Pumps 21 and 22 are electric motor 2
0, and the brake fluid is supplied to these fluid pressure paths to a predetermined pressure. Thus, these hydraulic paths are the supply sides of the brake hydraulic pressure to the solenoid valves 31 to 34. The discharge-side hydraulic passages of the solenoid valves 31 and 34 are connected to the pump 21 via the reservoir 23,
The discharge hydraulic passages 2 and 33 are connected to the pump 22 via the reservoir 24. The reservoirs 23 and 24 are provided with pistons and springs, respectively, and contain brake fluid that is recirculated from the solenoid valves 31 to 34 via a discharge-side hydraulic pressure path, and supply the brake fluid to the pumps 21 and 22 when the pumps 21 and 22 operate. Is what you do.

The solenoid valves 31 to 34 are three-port two-position solenoid switching valves, each of which is shown in FIG.
, Each wheel cylinder 51 to 54 is in communication with the hydraulic pressure generator 2 and the pump 21 or 22. When the solenoid coil is energized, it is in the second position, and each of the wheel cylinders 51 to 54 is
And the pumps 21 and 22 are shut off and communicate with the reservoir 23 or 24. Note that the check valve in FIG. 2 allows return from the wheel cylinders 51 to 54 and the reservoirs 23 and 24 to the hydraulic pressure generator 2 side, and shuts off the flow in the reverse direction.

The brake fluid pressure in the wheel cylinders 51 to 54 can be increased or decreased by controlling energization and non-energization of the solenoid coils of the solenoid valves 31 to 34. That is, when the solenoid coil is not energized, the hydraulic pressure generating device 2 is connected to the wheel cylinders 51 to 54.
In addition, the brake fluid pressure is supplied from the pump 21 or 22 to increase the pressure. It should be noted that a three-port, three-position electromagnetic switching valve may be used as the electromagnetic valves 31 to 34 so as to switch between three states of pressure reduction, pressure increase, and pressure holding, or the output hydraulic pressure may be linearly proportional to the flowing current. The same control may be performed using a proportional pressure control solenoid valve proportional to.

The solenoid valves 31 to 34 are connected to the electronic control unit 1
0, energizing each solenoid coil,
De-energization is controlled. The electric motor 20 is also the electronic control unit 1
0, which controls the drive. Further, wheel speed sensors 41 to 44 are provided for the wheels FR, FL, RR, RL, respectively, and these are connected to the electronic control unit 10, and the rotation speed of each wheel, that is, the wheel speed signal is transmitted to the electronic control unit. 10 is input. The wheel speed sensors 41 to 44 are well-known electromagnetic induction type sensors including a toothed rotor that rotates with the rotation of each wheel and a pickup provided to face the tooth portion of the rotor. It outputs a voltage having a frequency proportional to the speed. Note that a Hall IC, an optical sensor, or the like may be used instead.

The electronic control unit 10, as shown in FIG.
A one-chip microcomputer 11 having a CPU 14, a ROM 15, a RAM 16, and the like is connected to an input port 12 and an output port 13 via a common bus and performs input / output with the outside. The detection signals of the wheel speed sensors 41 to 44 are input to the CPU 14 from the input ports 12a to 12d via the amplification circuits 17a to 17d, respectively. In addition, a control signal is output from the output port 13 to the electric motor 20 via the drive circuit 18a, and the electromagnetic valves 31 to 34 are provided via the drive circuits 18b to 18e, respectively.
The control signal is output to

Further, the microcomputer 11 is configured such that the detection signals of the steering angle sensor 45 and the yaw rate sensor 46 are also inputted to the CPU 14 from the input port 12 via the amplifier circuits 17e and 17f, respectively. The steering angle sensor 45 is, for example, a well-known rotation angle sensor connected to a steering shaft of a vehicle, and outputs an electric signal corresponding to the steering angle θs. As the yaw rate sensor 46, for example, a yaw rate gyro (not shown) is used.
It is located near the center of gravity of the vehicle. Here, the yaw rate is a rotational movement about a vertical axis passing through the center of gravity of the vehicle, that is, an angular velocity of yawing, and is also referred to as a yaw angular velocity. The yaw rate gyro is a gyrometer for measuring the yaw rate.As is well-known, a high-speed rotating body that always keeps a rotating axis in a fixed direction is rotated around an axis perpendicular to the axis when an external force is applied. This is a device that measures the movement around the reference axis by utilizing the fact that a rotational movement occurs.

The electronic control unit 10 performs a series of processes for anti-skid control, which will be described below with reference to FIG. FIG. 4 is a flowchart showing the control of one embodiment of the anti-skid control device of the present invention, which is repeatedly executed at predetermined time intervals. Step 1
When the power is turned on at 10 and the routine is started,
First, it is initialized in step 111, and the estimated vehicle speed Vs
And the wheel speed Vw of each wheel is set to 0. Step 11
In 2, the wheel speeds Vw of the respective wheels detected by the wheel speed sensors 41 to 44 are read. Note that the estimated vehicle speed Vs is set as a vehicle speed based on the assumption that the vehicle is decelerated at a predetermined deceleration based on the wheel speed at the time of braking. The value when the vehicle is decelerated at the predetermined deceleration again from the value is set as the vehicle body speed, and is calculated in step 124 described later.

Next, in steps 113 and 114, the control mode of the anti-skid control is sequentially calculated for each of the front wheels FR and FL for each wheel. In the anti-skid control, the solenoid valves 31 and 32 are controlled in accordance with the slip ratio S obtained from the estimated vehicle speed Vs and the wheel speed Vw and the wheel acceleration of each of the wheels FR and FL. The control is performed so that the coefficient μ and the lateral drag fall within the optimum range.

When the calculation of the control mode of the front wheels FR and FL is completed, at step 115, the steering angle θs is compared with the reference angle Ka. This reference angle Ka is set according to the vehicle speed, that is, the vehicle speed, as shown in FIG. Steering angle θs
Is greater than or equal to the reference angle Ka, steps 116 and 1
Proceed to 17.

On the other hand, if the steering angle θs is smaller than the reference angle Ka at step 115, the routine proceeds to step 118, where the yaw rate Ys is compared with the reference value Kb. The reference value Kb is set according to the vehicle speed as shown in FIG. When it is determined that the yaw rate Ys is smaller than the reference value Kb, the process proceeds to steps 116 and 117, and the control mode is sequentially calculated for the wheels RR and RL independently for each wheel. When the yaw rate Ys is equal to or greater than the reference value Kb, the process proceeds to step 119, where the value of the wheel speed VwRR of the right wheel RR and the value of the wheel speed VwRL of the left wheel RL are compared. The control mode of both wheels RR and RL is calculated based on the latter, that is, the wheel speed VwRL on the low speed side. Also, the wheel speed Vw of the right wheel RR
When RR is lower than the left wheel speed VwRL, in step 121, the control mode of both wheels RR and RL is calculated based on the former wheel speed VwRR. That is, when the steering angle θs is smaller than the reference angle Ka and the yaw rate Ys is equal to or larger than the reference value Kb, the low speed selection control mode is set.

In step 122, the wheels FR, F
A drive signal is output to the solenoid valves 31 to 34 of each wheel according to each control mode of L, RR, and RL, and energization and non-energization of the solenoid coil are controlled. That is, the wheels FR, F
The brake fluid pressure supplied to the wheel cylinders 51 to 54 is controlled according to a control mode of selecting each wheel independently for L and for each wheel RR and RL in accordance with each wheel independent or low speed selection control mode. Proceeding to step 123, if a predetermined time Tc, for example, 10 msec has elapsed, the estimated vehicle speed Vs is calculated in step 124. If not, the process returns to step 112 and the destination operation is repeated.
The predetermined time is set according to the resolution of the vehicle speed in consideration of the function of the microcomputer 11.

[0022]

The present invention has the following effects because it is configured as described above. That is, the anti-skid control device of the present invention is controlled independently for each wheel on the front both sides of the vehicle, and controls the low speed selection control mode for the wheels on the rear both sides of the vehicle according to the turning state of the vehicle. The mode is switched to the wheel independent control mode. Thus, on the split road, the low speed selection control mode is set to maintain the stability of the vehicle, and when turning the vehicle, each wheel is set to the independent control mode without being set to the low speed selection control mode, so that an effective braking force is secured. The braking distance can be reduced as compared with the related art. In particular, the second comparison
If the reference value of the vehicle is variable and the vehicle speed is high,
If the vehicle speed is low, a lower reference value is set.
Low speed selection control mode at high speed compared to low speed
And stability of the vehicle is easily maintained. this
On the other hand, at low speed, each wheel has an independent control mode
Therefore, it is easy to secure the braking force.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an outline of an anti-skid control device of the present invention.

FIG. 2 is an overall configuration diagram of an embodiment of an anti-skid control device of the present invention.

FIG. 3 is a block diagram illustrating a configuration of the electronic control device of FIG. 2;

FIG. 4 is a flowchart illustrating a process for controlling a braking force according to an embodiment of the present invention.

FIG. 5 is a characteristic diagram of a reference angle Ka of a steering angle.

FIG. 6 is a characteristic diagram of a yaw rate reference value Kb.

[Explanation of symbols]

 2 Hydraulic pressure generator 2a Master cylinder 2b Booster 3 Brake pedal 10 Electronic control device 17a-17f Amplification circuit 18a-18e Drive circuit 20 Electric motor 21,22 Pump 23,24 Reservoir 31-34 Solenoid valve 41-44 Wheel speed sensor 45 Steering angle sensor (steering angle detecting means) 46 Yaw rate sensor (yaw rate detecting means) 51-54 Wheel cylinder FR, FL, RR, RL Wheel

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masaaki Komazawa 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Tatsuo Sugitani 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation ( 56) References JP-A-63-87356 (JP, A) JP-A-61-232952 (JP, A) JP-A-3-42361 (JP, A) JP-A-1-182156 (JP, A) (58) ) Surveyed field (Int.Cl. ⁶ , DB name) B60T 8/32-8/96

Claims (1)

(57) [Claims] 1. A low-speed selection control mode for controlling the braking force of each wheel on both rear sides of a vehicle in accordance with the rotation state of a low-speed wheel, and each wheel independent control mode for independently controlling the braking force of each wheel. Control mode switching means for switching according to the rotation state of each wheel, and controlling the braking force of each wheel on both rear sides of the vehicle according to the output of the control mode switching means,
In an anti-skid control device including a braking force control unit that independently controls a braking force of each wheel on both front sides of the vehicle, a steering angle detection unit that detects a steering angle of the vehicle,
A yaw rate detecting means for detecting a yaw rate of the vehicle, and a vehicle speed detecting means for detecting a speed of said vehicle, a first comparison means for comparing the detected steering angle of the steering angle detection means and criteria angle, the vehicle The speed detection means detects
Based on the speed of the vehicle, if the speed of said vehicle is high,
Serial set the lower reference value than when the vehicle speed is low, the detection yaw rate of the yaw rate detecting means comprises a second comparator means for comparing said reference value, said control mode switching means, said first According to the comparison result of the comparison unit and the second comparison unit, the low-speed selection control mode is set only when the detected steering angle is smaller than the reference angle and the detected yaw rate is equal to or larger than the reference value. The anti-skid control device, wherein each of the wheels is in the independent control mode.