JP2863293B2 - Anti-skid brake system for vehicles - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an anti-skid brake device for a vehicle.

(Prior Art) An anti-skid brake device is basically designed so that a wheel speed is reduced with a predetermined deceleration (control threshold) as a target or a wheel slip ratio is set to a target slip ratio (control threshold). By controlling the increase / decrease of the braking pressure applied to the wheels (hereinafter simply referred to as ABS control as necessary), it is possible to prevent wheel lock or skid from occurring during control, and to maintain directional stability. The vehicle is stopped at a short braking distance without losing the vehicle.

There are various proposals for the control of the braking pressure. For example, Japanese Patent Application Laid-Open No. 62-253560 discloses that the target slip ratio is changed according to the rotation angle of the steering wheel to achieve both the braking effect and the controllability. There is a disclosure about a technology for achieving the above. In other words, this system improves the maneuverability by controlling the braking pressure with the target of a low slip ratio when the rotation angle of the steering wheel is large, and increases the braking pressure with the target of a high slip ratio when the rotation angle of the steering wheel is small. By performing the control, the braking effect is enhanced.

(Problems to be Solved by the Invention) By the way, in driving a vehicle, braking may be applied to the wheels in a state where the driver temporarily panics. For example, when the vehicle suddenly jumps from the side of the road to the front of the vehicle while the vehicle is running, in such a case, the driver instinctively turns the steering wheel to the right and left while stepping on the brake pedal strongly to avoid danger. In some cases, the operation of cutting into large pieces may be performed.

In such a situation, danger avoidance by the driver's steering cannot be expected so much, and it is more desirable to stop the vehicle as soon as possible. However, when the anti-skid brake device operates in the same manner as during normal braking, a predetermined lateral drag (reaction force from the road surface) is obtained in consideration of the fact that the device itself performs turning motion even during braking. The vehicle is not always provided with the highest possible braking effect because the braking pressure is controlled to increase or decrease. Of course, it is not preferable in this case to perform an ABS control picture aiming at a low slip ratio as in the prior art.

That is, an object of the present invention is to make it possible to quickly stop a vehicle at a short braking distance while utilizing the characteristics of the anti-skid brake device even in the above-mentioned panic state.

(Means for Solving the Problems) In order to solve such a problem, the present invention detects a steering amount by a driver, and when the steering amount is excessively large, sets a threshold value of a braking pressure control to a high braking efficiency. Is to be changed.

That is, as shown in FIG. 1, a specific means for this is a wheel speed detecting means 1 for detecting a rotational speed of a wheel.
A braking pressure adjusting means 2 for adjusting a braking pressure of a wheel; and controlling the braking pressure adjusting means 2 to increase or decrease the braking pressure in accordance with a predetermined control threshold based on a wheel speed detected by the wheel speed detecting means 1. A turning amount detecting means 4 for detecting a turning amount, and a turning amount detected by the turning amount detecting means 4 being equal to or more than a predetermined value. Control threshold value changing means 5 for changing the control threshold value so as to increase the braking efficiency of the wheel at the time of (1).

In this case, the control threshold value changing means 5 determines that the larger the value obtained by subtracting the limit turning amount from the turning amount when the turning amount detected by the turning amount detecting means exceeds the predetermined limit turning amount, the larger the value of the wheel. The control threshold value may be changed so as to increase the braking efficiency.

Further, the control threshold value changing means 5 may change the control threshold value such that the higher the vehicle speed, the higher the braking efficiency of the wheels when the steering amount is equal to or more than a predetermined value.

Further, when the steering speed is equal to or less than a predetermined value, or when one of the stepping speed and the amount of depression of the brake pedal is equal to or less than a predetermined value, the control threshold value changing means 5 is prohibited from changing the control threshold value. Control threshold change prohibiting means 6 can be provided.

(Operation) The anti-skid brake device includes a means for changing the threshold value for the braking pressure control so that the braking efficiency is increased when the steering amount is equal to or more than a predetermined value. When the steering wheel is turned sharply and the wheel is turned sharply, by changing the control threshold value so that the braking pressure acts on the wheels slightly more than usual, that is, the braking efficiency of the wheels is increased, the vehicle is more than normal. Can also be stopped at a short braking distance.

In this case, since the wheels tend to be locked, it is not possible to sufficiently secure the lateral drag required for turning. However, in the above-mentioned panic state, the turning of the vehicle by the operation of the steering wheel is usually not very useful for avoiding danger. Therefore, even if the turning performance is somewhat sacrificed, the vehicle is stopped as quickly as possible with a sufficient braking force.

Further, in the change of the control threshold, when the turning amount exceeds the limit turning amount, the control threshold becomes higher as the value obtained by subtracting the limit turning amount from the turning amount becomes higher, so that the control efficiency of the wheel becomes higher. In other words, if the lock is changed so as to be deep, the braking efficiency can be adjusted according to the degree of the panic state of the driver.

Further, as described above, when the braking threshold value is changed based on the steering amount, if the braking efficiency of the wheels is increased as the vehicle speed increases, the turning traveling performance is excessively secured when the vehicle speed is low, When the vehicle speed is high, the braking efficiency can be increased and the vehicle can be stopped quickly.

Further, even when the steering amount is equal to or more than a predetermined value, if the steering threshold, the stepping speed of the brake pedal, and the stepping amount are determined to determine whether to change the control threshold, Only when the driver is truly panicked can the danger be avoided by controlling the lock.

That is, when the steering speed is equal to or less than a predetermined value, or when one of the stepping speed and the amount of depression of the brake pedal is equal to or less than the predetermined value, the steering is performed according to the driver's normal intention, or the braking is performed. Since the driver is not panicked as a result of depression of the pedal, the change of the control threshold value by the control threshold value changing means is prohibited, so that danger can be avoided by turning. .

(Effects of the Invention) Therefore, according to the present invention, in the anti-skid brake device for a vehicle, the threshold value for the braking pressure control is changed so that the braking efficiency is increased when the steering amount is equal to or more than a predetermined value. When the driver turns the steering wheel sharply (for example, when the driver is panicked)
The situation where the driver or the vehicle is located, such as controlling the braking pressure so that it tends to be locked to ensure braking performance, otherwise performing normal ABS control to ensure the steering stability of the vehicle Can be controlled according to.

Also, when the turning amount exceeds the limit turning amount, if the change amount of the control threshold is determined according to the exceeded amount, the degree of panic of the driver can be grasped more practically. ABS control can be performed.

When the control threshold value is changed based on the steering amount, if the braking efficiency of the wheels increases as the vehicle speed increases, the ABS control according to the actual situation of the vehicle can be performed.

Also, when the control threshold value is changed, whether or not the above change is performed is determined based on the steering speed or the depressed state of the brake pedal. The control can be performed by grasping in accordance with the above.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

As shown in FIG. 2, in the vehicle according to this embodiment, the left and right front wheels 11, 12 are driven wheels, the left and right rear wheels 13, 14 are drive wheels, and the output torque of the engine 15 is It is configured to be transmitted to left and right rear wheels 13 and 14 via a propeller shaft 17, a differential device 18 and left and right drive wheels 19 and 20.

Each of the wheels 11 to 14 has a brake device including disks 21 a to 24 a that rotate integrally with the wheels and calipers 21 b to 24 b that brake the rotation of the disks 21 a to 24 a by receiving a supply of braking pressure. 21 to 24 are provided.

A brake control system for operating the brake devices 21 to 24 includes a booster 27 that increases the depression force of a brake pedal 26 by a driver, and a braking pressure according to the force increased by the booster 27. And a master cylinder 28 for generating. The brake pressure supply line 29 for the front wheels extending from the master cylinder 28 branches into a brake pressure supply line 29a for the left front wheel and a brake pressure supply line 29b for the right front wheel, and the calipers 21a and 22b of the brake devices 21 and 22 respectively. It is connected. The left front wheel braking pressure supply line 29a is provided with a first valve unit 30 including an electromagnetic on-off valve 30a and an electromagnetic relief valve 30b.
In b, a second bubble unit 31 including an electromagnetic on-off valve 31a and an electromagnetic relief valve 31b is provided.

A third valve unit 33 including an electromagnetic on-off valve 33a and an electromagnetic relief valve 33b is provided on the rear wheel braking pressure supply line 32 extending from the master cylinder 28. The rear wheel braking pressure supply line 32 branches into a left rear wheel braking pressure supply line 32a and a right rear wheel braking pressure supply line 32b downstream of the third valve unit 33. , 24 are connected to calipers 23a, 24b.

That is, in the present embodiment, the first channel for adjusting the braking pressure of the brake device 21 of the left front wheel 11 by the operation of the first valve unit 30 and the brake device 22 of the right front wheel 12 by the operation of the second valve unit 31 A second channel for adjusting the braking pressure of the left and right rear wheels 13, 14 by operating the third valve unit 33, and a third channel for adjusting the braking pressure of the braking devices 23, 24 of the left and right rear wheels 13, 14. They are controlled independently of each other. The first to third valve units 30, 31, 33 constitute the braking pressure adjusting means 3.

The control unit 34 for controlling the first to third channels includes a brake signal from a brake sensor 35 for detecting whether or not the brake pedal 26 is depressed, a stepping speed and a stepping amount of the brake pedal 26, 11-14
The wheel speed signals from the wheel speed sensors 37 to 40 as the wheel speed detecting means 1 for detecting the rotation speed of the vehicle and the steering angle signals (steering amount, steering speed) from the steering angle sensor 41 are input, and ABS Control is performed in parallel for each channel.

That is, the control unit 34
Control means 3 for controlling the increase and decrease of the braking pressure of each of the wheels 11 to 14 by the valve units 30, 31, 33 in accordance with a predetermined control threshold based on the wheel speeds of 〜14, control threshold change means 5, and control threshold change Prohibiting means 6, wherein the opening / closing valves 30 a, 31 a, 33 a and the relief valve 3 of the first to third valve units 30, 31, 33 are provided.
0b, 31b, and 33b are controlled to open and close by duty control. The brake oil discharged from the relief valves 30b, 31b, 33b is returned to the reservoir tank 28a of the master cylinder 28 by a drain line (not shown).

Hereinafter, the control unit 34 will be specifically described.

The control means 3 includes a pseudo vehicle speed setting section and a control threshold setting section. The control section 3 compares the control threshold value with the wheel acceleration / deceleration and the slip ratio to determine the phase 0 (ABS non-control state), the phase I
(Depressurized braking pressure during ABS control), Phase II
(Holding state after pressure reduction), phase III (rapid pressure increase state after pressure reduction holding), and phase IV (slow pressure increase state after rapid pressure increase), and a braking pressure control signal corresponding to each phase is set to the first. To the third valve units 30, 31, 33.

<Pseudo-vehicle speed setting> The above-described pseudo-vehicle speed Vr is set as a convenient vehicle speed based on the wheel speed since the vehicle speed when the wheels 11 to 14 are slipping cannot be accurately detected. Yes, the maximum wheel speed of the four wheels 11 to 14 is the pseudo vehicle speed Vr
On the other hand, according to the road surface friction coefficient, the speed change amount is changed from 1.2G · Δt at the high friction coefficient to 0.3G at the low friction coefficient.
-It is set up to Δt and corrected as follows. Note that Δt is a sampling period (for example, 7 ms) of the control unit 34.

Vr ← Vr− (1.2 G · Δt to 0.3 G · Δt) <Setting of control threshold> The control threshold is set independently for each channel. First wheel deceleration threshold value G1 for determining transition from phase 0 (when ABS is not controlled) to phase I (decompression), and second wheel deceleration threshold value for determining transition from phase I to phase II (holding)
G2, a first slip ratio threshold value S1 for determining a transition from phase II to phase III (sudden pressure increase), and a wheel acceleration threshold value G3 for determining a transition from phase III to phase IV (slow pressure increase)
And a second slip ratio threshold S2 for determining transition from phase IV to phase I. The above control threshold is the pseudo vehicle speed.
It is set appropriately according to Vr and the friction coefficient of the road surface.

Regarding the wheel speeds of the rear wheels 13, 14, the smaller one of the two wheel speeds is selected as the rear wheel speed. Also,
The slip ratio is calculated according to the following equation.

Slip ratio = (1−wheel speed ÷ pseudo vehicle speed) × 100 In this case, the setting of the control threshold value in the normal ABS control is performed by setting the lateral drag coefficient μL of the wheel to the road surface excessively as shown in FIG. It is set so that the friction coefficient μ between the road surface and the wheels can be increased without lowering, that is, the characteristic in the range of Ss can be obtained. That is, a high coefficient of friction μ means high braking efficiency, and a high coefficient of lateral drag μL means good stability or steering performance in cornering. Turning performance is, as can be seen from FIG. 3, difficult to achieve both. In the ordinary ABS control, a control threshold value is set so that the two are compatible as much as possible.

The deceleration and acceleration of the wheel are obtained by dividing the difference between the previous value and the current value of the wheel speed by the sampling period Δt, and converting the result to a gravitational acceleration.

When detecting the friction coefficient of the road surface, when the ABS is not controlled, it is determined uniformly as a high friction road surface, and after entering the ABS control, the friction coefficient of the road surface is detected based on the wheel deceleration and the wheel acceleration It is. That is, when the wheel deceleration is large and the wheel acceleration is small, it is determined that the road surface is low friction. When the wheel deceleration is small and the wheel acceleration is large, it is determined that the road surface is high friction.

<Normal ABS Control> Accordingly, normally, a control for increasing or decreasing the braking pressure as shown in FIG. 4 is performed.

That is, when the brake pedal 26 is depressed from the constant speed running state, the braking pressure generated in the master cylinder 28 increases, and the wheel speed decreases accordingly.

When the wheel deceleration becomes larger than the first wheel deceleration threshold value G1, the process proceeds to the ABS control, phase I is selected, and the braking pressure is reduced according to a predetermined pressure reduction mode.

When the wheel deceleration becomes smaller than the second wheel deceleration threshold value G2, phase II is selected and the braking pressure is maintained in a reduced pressure state.

When the slip ratio decreases along with the above-described pressure reduction and exceeds the first slip ratio threshold value S1, phase III is selected, and the braking pressure is rapidly increased.

When the wheel acceleration decreases due to the rapid pressure increase and becomes equal to or less than the wheel acceleration threshold value G3, the phase IV is selected, and the braking pressure is gradually increased.

Due to the above-described slow pressure increase, the slip ratio becomes the second slip ratio threshold value.
Beyond S2, phase I is selected.

As described above, for each of the first to third channels,
By controlling the increase and decrease of the braking pressure independently of each other, the occurrence of the lock or skid state of each wheel is prevented, and the vehicle is stopped at a short braking distance without losing directional stability.

<Change of Control Threshold> -Basic Control- The change of the control threshold is basically performed based on the turning amount θH obtained by the steering angle sensor 41. That is, when the turning amount θH is equal to or larger than the predetermined value θHo, the control threshold value is changed to a direction in which the braking efficiency of the wheel is increased (lock is deepened).

In this case, the turning amount equal to or more than the predetermined value θHo is, for example, a sudden jump from the side of the road to the front of the vehicle during running of the vehicle, the driver temporarily falls into a panic state, and the driver avoids danger. This is the amount of steering when the steering wheel is turned sharply by accident. Then, the control threshold value is changed so that the slip ratio threshold value is increased and the gradient of the pseudo vehicle speed Vr is increased to the negative side.

Specifically, when information equal to or greater than the steering amount θHo is obtained,
The first wheel deceleration threshold G1 for determining transition from phase 0 (when ABS is not controlled) to phase I (decompression) and the deceleration threshold G2 for determining transition from phase I to phase II (hold) are high. The first slip ratio threshold value S for determining the transition from phase II (reducing pressure) to phase III (rapid pressure increase).
2 and the second for determining the transition from Phase IV to Phase I
The slip ratio threshold value S2 is high, that is, it becomes deeper when viewed from the pseudo vehicle speed Vr.
A predetermined change is made to each of the threshold values so as to lower the wheel acceleration threshold value G3 for determining transition to (slow pressure increase).

The change of the control threshold will be described with reference to FIG. 3. If the change is performed, the slip ratio Sμ at which the highest friction coefficient μ (maximum braking efficiency) is obtained even at the expense of the lateral drag coefficient μL,
Or a higher slip ratio (deeper lock).

FIG. 5 is a flowchart showing the control for changing the control threshold, in which a steering angle signal and each wheel speed signal signal are input, and the steering amount θH
Is larger than the predetermined value θHo, the control threshold is changed to the lock deepening direction to perform the ABS control (steps S1 to S1).
3). When the steering amount θH is less than the predetermined value θHo, normal ABS control is performed without changing the control threshold (step S4).

Therefore, for example, when the vehicle suddenly jumps from the side of the road to the front of the vehicle while the vehicle is running and the driver temporarily panics and turns the steering wheel involuntarily, the lock is deeper than usual. By performing the ABS control, the braking efficiency of the wheels is increased, and the vehicle can be stopped at a short braking distance. On the other hand, when the steering wheel is turned by the driver's intention, the steering amount does not become excessively large, and the normal ABS control is performed, so that the wheels can appropriately reduce the lateral drag required for turning. Therefore, the stability or the steering performance of the cornering can be improved.

—Change Based on Steering Amount and Vehicle Speed— The control threshold is changed in consideration of the vehicle speed in addition to the above-described steering amount. That is, when the steering amount θH is larger than the predetermined value θHo, the control threshold is changed so that the lock becomes deeper as the vehicle speed increases.

FIG. 6 shows the flow of the change control. When the steering amount θH is larger than the predetermined value θHo in step S2, the control threshold change amount β is calculated from the map based on the vehicle speed v, and the control threshold is changed. (Steps S2 to S6).

—Change Based on Limit Steering Amount and Vehicle Speed— This change in the control threshold is performed in consideration of the limit steering amount. That is, when the actual turning amount θH exceeds the limit turning amount θHm, the control threshold is changed in a direction in which the lock becomes deeper as the value a obtained by subtracting the limit turning amount θHm from the actual turning amount θH increases. In addition, the vehicle speed v is also taken into account in determining the final change amount.

In this case, the limit turning amount is a turning amount that makes it impossible to perform a turning operation corresponding to the steering angle (for example, causes over-steering), and is based on the vehicle speed v and the friction coefficient μ of the road surface. And is calculated from the map shown in FIG.

FIG. 8 is a flowchart of the change control. If the value a obtained by subtracting the limit turning amount θHm from the actual turning amount θH in step S2 is equal to or less than zero, the control ABS is not changed and the normal ABS is not changed.
Control is performed (step S7). The value a is larger than zero, that is, the actual turning amount θH is equal to the limit turning amount θHm.
Is exceeded, the control threshold change amount α is calculated from the map based on this a, and the control threshold is changed (steps S5 to S5).
S7).

The magnitude of the value a can be considered to represent the degree to which the driver is panicked. Therefore, in this example in which the amount of change of the control threshold is changed according to the value a, the ABS control can be performed according to the panic state of the driver.

-Control threshold change prohibition-The parameters for prohibiting the change of the control threshold include the stepping speed, the stepping amount, and the turning speed of the brake pedal 26.

More specifically, the brake sensor 35 determines that the brake pedal depression speed Bv is less than a predetermined value Bvo or the depression amount Bt.
Is smaller than the predetermined value Bto, the steering angle sensor 4
When the information that the turning speed dθH / dt is less than the predetermined value A is obtained from the control command, the control threshold changing means 5 issues an operation prohibition command so that the control threshold is not changed.

In other words, even when the steering wheel is greatly turned, when the brake pedal 26 is depressed or steered by the driver's normal intention, the depressed speed, depressed amount, or turning speed of the brake pedal 26 is equal to or less than a predetermined value. Normally, in such a case, normal ABS control is executed, and the stepping speed, the stepping amount,
Alternatively, the control threshold is changed when the steering speed exceeds a predetermined value.

FIG. 9. Is a flow showing a control threshold change prohibition control. In this example, the control threshold value is changed in consideration of not only the predetermined turning amount θHo but also the limit turning amount θHm and the vehicle speed v.

That is, after the input of various data, when the turning amount θH is larger than the predetermined value θHo, it is determined whether the value a obtained by subtracting the limit threshold amount θHm from the turning amount θH is larger than zero. Then, the control threshold change amount α corresponding to a is obtained (steps S1 to S4). Next, the control threshold change amount β according to the vehicle speed v is obtained (step S5).

Then, the stepping speed Bv of the brake pedal is equal to or higher than a predetermined value Bvo, the stepping amount Bt is equal to or higher than a predetermined value Bto, and the turning speed dθH / dt.
Is determined to be equal to or greater than the predetermined value A, the above α + β is calculated, the control threshold is changed based on this, ABS control is performed with the changed control threshold, and if any one is less than the predetermined value, Normal ABS without changing control threshold
Control is performed (steps S6 to S11).

In this example, the control threshold value is changed when all of the brake pedal depression speed, the depression amount, and the turning speed are equal to or higher than a predetermined value. In such a case, the control threshold value may be changed.

Further, in a vehicle having a four-wheel steering system in which the rear wheels are also steered when the front wheels are steered, when the control threshold value is changed to a lock deeper, the steering ratio of the rear wheels to the front wheels is simultaneously increased. May be corrected to the same phase to improve the running stability of the vehicle. This correction of the steering ratio is particularly useful during high-speed running.

[Brief description of the drawings]

FIG. 1 is a block diagram of the present invention, FIG. 2 and subsequent figures show an embodiment of the present invention, FIG. 2 is a diagram showing the overall configuration of an anti-skid brake device, and FIG. FIG. 4 is a time chart of normal ABS control, FIGS. 5, 6, 8, and 9 are flow charts of control threshold value change control, and FIG. FIG. 7 is a limit turning amount characteristic diagram. DESCRIPTION OF SYMBOLS 1 ... Wheel speed detection means 2 ... Braking pressure adjustment means 3 ... Control means 5 ... Control threshold value change means 6 ... Control threshold value change prohibition means 11-14 ... Wheels 21-24 ... Brake device 26 ... Brake pedals 30, 31, 33: Valve unit (braking pressure adjusting means) 35: Brake sensor (pedal depressing speed and depressing amount detecting means) 41: Steering angle sensor (steering amount and turning speed detecting means)

Claims (5)

(57) [Claims] A wheel speed detecting means for detecting a rotational speed of the wheel; a braking pressure adjusting means for adjusting a braking pressure of the wheel; and a predetermined control threshold value based on the wheel speed detected by the wheel speed detecting means. An anti-skid brake device for a vehicle, comprising: control means for controlling the braking pressure adjusting means so as to increase or decrease the braking pressure, wherein the steering amount detecting means detects a steering amount; An anti-skid brake device for a vehicle, comprising: control threshold changing means for changing the control threshold so as to increase the braking efficiency of the wheel when the detected steering amount is equal to or more than a predetermined value. 2. The control threshold changing means according to claim 1, wherein, when the turning amount detected by the turning amount detecting means exceeds a predetermined limit turning amount, a value obtained by subtracting the limit turning amount from the detected turning amount. 2. The anti-skid brake device for a vehicle according to claim 1, wherein the control threshold value is changed such that the larger the value of the braking force, the higher the braking efficiency of the wheels. 3. A vehicle speed detecting means for detecting a vehicle speed, wherein the control threshold value changing means increases the wheel braking efficiency as the vehicle speed detected by the vehicle speed detecting means increases when the turning speed is equal to or higher than a predetermined value. The anti-skid brake device for a vehicle according to claim 1 or 2, wherein the control threshold value is changed as described above. 4. A turning speed detecting means for detecting a turning speed,
A control threshold value change prohibiting means for prohibiting a change of the control threshold value by the control threshold value changing means when the turning speed detected by the turning speed detecting means is equal to or less than a predetermined value. The anti-skid brake device for a vehicle according to the above item. 5. A brake pedal depressing speed detecting means for detecting a depressing speed of a brake pedal, a brake pedal depressing amount detecting means for detecting a depressing amount of the brake pedal, and a brake pedal depressing speed detected by the two detecting means. And a control threshold change prohibiting means for prohibiting a change of the control threshold value by the control threshold value changing means when one of the stepping amount is equal to or less than a predetermined value. Anti-skid brake device.