JPH0539020A - Anti-skid brake device for vehicle - Google Patents

Abstract

PURPOSE:To shorten a braking distance while surely preventing a wheel lock by detecting reducing deceleration of a vehicle and finishing control of braking force reduction in the anti-skid control when a sign of the reducing deceleration detected is judged just inverted. CONSTITUTION:In an anti-skid brake device for vehicle, pressure increase, holding and decompression of brake fluid pressure generated by a master cylinder 21 and supplied to brake devices 7FR-7RL at the time of applying brakes are switched by opening/closing-controlling first and second shut-off valves 22, 23 to solve the wheel lock. That is, when a tendency to the wheel lock is detected, the brake fluid pressure is reduced by closing the first shut-off valve 22 and opening the second shut-off valve 23 and the fluid pressure is held by closing both shut-off valves 22, 23. In this case, a control unit U to which output signals from wheel speed sensors S1-S4 are input detects reducing deceleration of a wheel and judges whether a sign of the reducing deceleration is inverted or not. When the sign of the reducing deceleration is judged just inverted, the decompression control is finished.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle anti-skid brake device.

[0003]

2. Description of the Related Art Recently, as is well known by the name of ABS device, many vehicles are equipped with an anti-skid brake device for preventing the wheels from locking during braking. In this ABS control, there are at least two types of control modes, that is, a control for decreasing the braking force and a control for increasing the braking force, and in addition to this, there is also a control mode for holding the braking force. On the other hand, whether or not the wheels are locked can be usually judged by the slip value obtained from the theoretical vehicle speed theoretically calculated and the actual wheel speed, but the pseudo vehicle speed and therefore the slip value is not so accurate. Since it is not good, it is difficult to adopt the determination as to whether or not the control for reducing the braking force is ended depending only on the slip value, because of the control accuracy required for the recent ABS control. On the other hand, the wheel deceleration is easily and accurately obtained by differentiating the wheel speed detected by the wheel speed sensor, while the deceleration shows the wheel behavior fairly accurately. Becomes From such a point of view, in Japanese Patent Publication No. 61-22220, it is determined whether or not the control for reducing the braking force is ended depending on whether or not the deceleration of the wheels has passed a predetermined threshold value. What has been proposed is proposed.

However, as described in the above publication, when the control for reducing the braking force is ended at the time when the deceleration of the wheels passes a predetermined threshold value, the following inconvenience occurs. That is, the deceleration of the wheels starts to gradually increase from the beginning of the application of the braking force, and the deceleration is gradually decreased by the control of the braking force reduction to recover the vehicle speed. The same value of deceleration will appear twice in the initial period and the latter period. This means that when the braking force reduction control is terminated depending on the deceleration, the braking force reduction control is mistakenly terminated based on the deceleration at the initial stage of deceleration. It will be easy to lock.

[0007]

By the way, recent AB
In S control, there is an extremely strong demand for shortening the braking distance. From this point of view, it is desired to minimize the opportunity to control the braking force reduction, but to reduce the opportunity to control the braking force reduction more than necessary will easily cause wheel locking. Therefore, when to end the control of the braking force reduction is important for improving the controllability of the ABS control. Therefore, an object of the present invention is to appropriately set the ending time point of the control for reducing the braking force so that the locking of the wheels can be reliably prevented and the braking distance can be shortened. To provide.

[0009]

In order to achieve the above object,
The present invention is as follows. That is, in an anti-skid brake device for a vehicle, which controls the reduction of braking force so that the wheels do not lock during braking, the deceleration / deceleration detection means for detecting the deceleration / deceleration of the wheels, and the deceleration / deceleration. After determining that the sign of the deceleration and deceleration detected by the speed detecting unit is inverted, and after determining that the sign of the deceleration and deceleration is inverted by the determining unit,
And a terminating means for terminating the control of the braking force reduction.

The deceleration of the wheel accurately indicates in which direction the deceleration of the wheel is going to change its behavior, that is, whether the wheel is trying to decelerate or accelerate. Then, the time when the sign of the deceleration is reversed during the control of the braking force decrease means the time when the sign changes from − to + and the rotational speed of the wheel starts to recover. Therefore, after this sign reversal, even if the control for reducing the braking force is ended, there is no problem in preventing the wheel lock. After the sign reversal that ensures this lock prevention, the control of the braking force decrease can be ended at an appropriate time, and if the braking distance is to be shortened most, the braking force is reduced at this sign change time. It is also possible to end the control of reduction.

As a time point when the control of the braking force reduction control is actually ended, in addition to the condition after the sign reversal, another condition that the deceleration of the wheel becomes less than a predetermined value is added. preferable. In this case, by looking at the sign reversal time, it is possible to reliably prevent a situation in which the control of the braking force reduction is erroneously ended at the initial stage of the deceleration reduction such as that described in the publication. Moreover, since the braking force reduction control is terminated by the double check of the wheel deceleration and the deceleration, the ending point of the braking force reduction control can be made more optimal. In addition,
The deceleration of the wheel is easily and accurately obtained by differentiating the detection value of the wheel speed sensor for detecting the rotational speed of the wheel, and the deceleration of the wheel is further differentiated from the deceleration obtained by the differentiation. Can be obtained.

[0015]

EXAMPLE Explanation of FIG . 1 FR is the right front wheel, 1FL is the left front wheel, 1RR is the right rear wheel, 1R
L is the left rear wheel. Reference numeral 2 denotes an engine, and after the torque generated by the engine 2 is transmitted to the clutch 3, the transmission 4, the propeller shaft 5, and the actuating device 6, the right rear wheel 1RR is driven again via the drive shaft 6R. Shaft 6L
Is transmitted to the left rear wheel 1RL via. Each wheel 1FR ~ 1
The break devices 7FR to 7RL are respectively provided in the RL. Each of the breaking devices 7FR to 7RL includes a disk 8 that rotates integrally with a wheel, and a caliper 9 that incorporates a wheel cylinder.

Reference numeral 11 denotes a master cylinder as a brake fluid pressure generating means, and the driver's stepping force on the brake pedal 12 is input through a known booster 13 to produce a brake corresponding to the stepping force. Liquid pressure is generated. This master cylinder 11 is of a tandem type having two discharge ports. The brake pipe 14 extending from one discharge port of the master cylinder 11 is branched into two in the middle, and one branch pipe 14FR is connected to the brake device 7FR (wheel cylinder) for the right front wheel, The other branch pipe 14FL
Is connected to (the wheel cylinder of) the braking device 7FL for the left front wheel. The brake pipe 15 extending from the other discharge port of the master cylinder 11 is branched into two in the middle, and one branch pipe 15RR is connected to (the wheel cylinder of) the brake device 7RR for the right front wheel. The other branch pipe 15RL is a brake device 7RL (for the left rear wheel)
Connected to the cylinder).

A hydraulic pressure adjusting mechanism 21FR is provided for the branch pipe 14FR for the right front wheel, a hydraulic pressure adjusting mechanism 21FL is provided for the branch pipe 14FL for the left front wheel, and a hydraulic pressure adjusting mechanism 21R is provided for the pipe 15 commonly used for the left and right rear wheels. Are connected. Each hydraulic pressure adjustment mechanism 2
1FR, 21FL and 21R are the first on-off valve 2 respectively.
2 and the second opening / closing valve 23. Each open / close valve 22, 2
3 are electromagnetic type, and the first opening / closing valve 22 is the pipe 1
Open and close 4FR, 14FL or 15 to open the second opening / closing valve 2
Reference numeral 3 connects and disconnects each pipe and the reservoir tank. As a result, when the brake fluid pressure is generated in the master cylinder 21, the brake device 7 is operated.
The pressure increase, the pressure retention, and the pressure reduction of the brake hydraulic pressure supplied to FR to 7RL are switched. That is, the pressure is reduced by closing the first opening / closing valve 22 and opening the second opening / closing valve 23, and held by closing both opening / closing valves 22 and 23,
The pressure is increased by opening the first opening / closing valve 22 and closing the second opening / closing valve 23. Then, in the embodiment, the pressure is initially increased rapidly, and then gradually increased.
This is performed by, for example, duty-controlling the opening speed (opening) of the first opening / closing valve 22.

In FIG. 1, U is a control unit constructed by using a microcomputer, and the signals of the respective sensors or switches S1 to S5 or R are input to the control unit U. The sensors S1 to S4 are used for the wheels 1FR to 1R.
The rotation speed of L is detected. The switch S5 is
The brake switch is turned on when the brake pedal 12 is depressed. In addition, the control unit U
The hydraulic pressure adjusting mechanisms 21FR, 21FL, 21R are controlled, but as is clear from the above description, the left and right front wheels 1FR, 1FL are individually and individually ABS controlled, and the left and right rear wheels 1RR, 1RL are controlled. Are integrated and ABS control is performed. The ABS control is performed on the assumption that the break switch S5 is ON.

Description of FIG . 2 The content of the ABS control by the control unit U will be described with reference to FIG. In this ABS control, Phase 0, Phase 1, Phase 2, Phase 3, Phase 5
Is used, and its meaning is as follows. Phase 0: Means that non-ABS control is in progress. Phase 1: means increasing pressure (increasing braking force). Phase 2: means holding (holding braking force) after non-ABS control or after pressure increase. Phase 3: means decompression (reduction of braking force). Phase 5: Retaining after depressurization. The slip value indicating the locking tendency of the wheels is determined by, for example, the following equation, and the estimation of the pseudo vehicle body speed will be described later. Slip value = (wheel speed / pseudo vehicle speed) x 100%

On the premise of the above, it is a time when the ABS control is not performed until the time t1.
As the hydraulic pressure increases, the wheel speed gradually decreases from the pseudo vehicle speed. Due to the decrease in the wheel speed, the deceleration of the wheel speed decreases to a predetermined value as the ABS control start condition at time t1, that is, time A. The ABS control is started from the time point A, but it is performed by first maintaining the brake hydraulic pressure. Even during this holding, the wheel speed decreases, and when the slip value decreases to a predetermined threshold value as shown at time B, the pressure is reduced. Due to this pressure reduction, the degree of decrease of the wheel speed is weakened, and the deceleration becomes near 0 at the time C. At the time point C when the deceleration is near 0, the holding is performed, whereby the wheel speed gradually increases, and the slip value returns to the predetermined threshold value at the time point D. From the time point D, the pressure is increased, but the pressure is rapidly increased in the initial stage and then gradually increased. Due to the pressure increase, the deceleration of the wheel speed is reduced again to the predetermined value set as the ABS control start condition at the time point E. As a result, after the brake fluid pressure is maintained, the pressure is reduced when the slip value decreases to a predetermined threshold value at time F. And
The brake fluid pressure is maintained from time G corresponding to time C.

The above is the outline of the ABS control, and the period from the end of the phase 5 (starting pressure increase), which is the holding after depressurization, to the end of the next phase 5, is one control cycle. However, this 1 cycle is a failure only when the ABS control is started.
From the start of holding Phase 2 until the end of Phase 5 (because the ABS control is started from Phase 2). The threshold value when the phase is changed is changed according to the road surface μ (friction coefficient), and a specific setting example of the threshold value according to the road surface μ is shown in the following table.

[0029]

[Table 1]

Description of FIG. 3 FIG. 3 is a flow chart showing a control example of the present invention.
In the following description, P indicates a step. First, after signals from sensors S1 to S5 are input at P100, P110
At μ, the road surface μ is estimated. At P120, the pseudo vehicle speed is estimated, and at P130, the slip value for ABS control described above is calculated. Then, at P140, the ABS control as described in FIG. 2 is performed. The details of P110, P120, and P140 will be described later.

Description of FIG. 4 FIG. 4 is for estimating the road surface μ, and is indicated by P in FIG.
The contents of 110 are shown. The control of FIG. 4 is performed independently for each wheel. First, P1
At, it is determined whether or not ABS control is currently being performed. When the determination in P1 is NO, the road surface μ is set to 3 in P2, which means that the road surface μ is high (the friction coefficient is large). In this way, the road surface μ is forcibly set to a high μ when the ABS control is not being executed, so that the brake fluid pressure is suppressed from being reduced at the beginning of the ABS control, and the braking distance is reduced. Be done. When the determination in P1 is YES, the acceleration / deceleration WG of the wheel is calculated by differentiating the wheel speed in P3. This WG
When calculating, the maximum value within a predetermined period is stored as the acceleration, and the minimum value is stored as the deceleration. P
After 3, the determination is made in P4 as to whether or not the deceleration of the WG is smaller than a predetermined threshold value of -20G.
It should be noted that -20G as the threshold value means a value corresponding to -20G in a predetermined sampling period (the same applies hereinafter).

When the determination in P4 is YES, it means that the road surface μ may be low. At this time, first, at P5, it is judged if the acceleration of the WG is greater than 10G. If NO in this determination in P5, μ = 1 is set in P8, which means low μ. If YES in the determination of P5, and the above P
If the result of the determination in No. 4 is NO, in each P6, WG
It is determined whether or not the acceleration is greater than 20G. If YES in P6, μ in P9
Is set to 3 and when the determination in P6 is NO, μ is set to 2 (medium μ) in P7.

Description of FIGS . 5 and 6 FIG. 5 is for estimating the pseudo vehicle speed.
Corresponds to the contents of P120 of. In P21 of FIG.
Of the wheels 1FR to 1RL, the wheel with the highest wheel speed is W.
It is set as M. After that, in P22, the maximum wheel speed WM is differentiated to calculate the amount of change, that is, the acceleration / deceleration WM · G for the maximum wheel speed. P
3, the reference deceleration -GO according to the road surface μ is determined, and this reference deceleration -GO is the maximum wheel deceleration that is expected to occur according to the road surface μ at the time of braking. Yes, and the corresponding relationship is shown in FIG. In this case, the smaller the road surface μ, the smaller the reference deceleration-GO is set (the absolute value of GO is larger as the road surface μ is smaller).
However, in the embodiment, since the road surface μ is determined in three stages, −
GO is also decided in three stages.

At P24, WM · G is the reference deceleration-GO
Is less than or equal to. If the determination in P24 is YES, the pseudo vehicle body speed VR is set to a value based on the reference deceleration-GO in P25. That is, at this time, when the wheel speed suddenly decreases, the speed corresponding to the reference deceleration-GO from the previously determined pseudo vehicle speed is suppressed in order to suppress the sudden decrease in the pseudo vehicle speed. The value obtained by subtracting is set as the pseudo vehicle body speed VR this time. If NO in P24, in P26,
It is determined whether or not the value obtained by subtracting the maximum wheel speed WM from the previous pseudo vehicle speed VR is greater than or equal to a predetermined value. This P26
Even if the determination is YES, it means that the wheel speed has decreased considerably rapidly. Therefore, at this time as well, the processing shifts to P25 described above in order to suppress the rapid decrease in pseudo vehicle speed. If NO in P26, the maximum wheel speed WM is set as it is as the pseudo vehicle speed in P27. Of course, the pseudo vehicle body speed determined in P25 or P27 is used as the previous pseudo vehicle body speed in P26.

Description of FIG. 7 FIG. 7 shows phase 3 of the control contents of P140 of FIG.
That is, the control content is shown until the control for decreasing the braking force is completed and the process shifts to the phase 5, that is, the control for maintaining the braking force. First, in P31, it is judged whether or not the state is currently in phase 3, but if the judgment in P31 is NO, the routine is returned as it is. YES in P31
In this case, in P32, the wheel reference deceleration GB is determined as a threshold value when the phase 3 shifts to the phase 5 in accordance with the road surface μ determined as described above (Table). 1). In P33, the deceleration G is calculated by differentiating the wheel speed, and subsequently in P34, the wheel deceleration SG is calculated by further differentiating the calculated deceleration G.

At P35, it is judged if the flag is 1. This flag is set to 1 when the sign of the deceleration SG is reversed (reversal from − to plus), but since it is initially set to 0, the routine moves from P35 to P36. In this P36, it is judged whether or not the sign of the deceleration SG is reversed, and if the judgment in P36 is NO, it means that the wheel speed has not yet shown a tendency to recover, so the recovery is continued. Will be YE in the judgment of P36
When S, the flag is set to 1 in P37, and then in P38, it is determined whether or not the wheel deceleration G is equal to or lower than the reference deceleration GB, that is, the deceleration is in a sufficiently small state near 0. It is determined whether or not (the G with a minus sign has a larger deceleration as its absolute value is larger, and at P38, it is determined whether or not this absolute value is sufficiently small).

If NO in P38, again in P35
When it comes to, the determination is YES, the determination of P38 is repeated, and the determination of P38 is eventually YES with the progress of the control of Phase 3, that is, the braking force reduction. P38
If the determination is YES, the flag is reset to 0 in P39, then the phase 3 is ended in P40, and the phase shifts to phase 5 (control of holding braking force).

[Brief description of drawings]

FIG. 1 is an overall system diagram showing an embodiment of the present invention.

FIG. 2 is a time chart showing an example of ABS control.

FIG. 3 is a flowchart showing a control example according to the present invention.

FIG. 4 is a flow chart showing a control example according to the present invention.

FIG. 5 is a flowchart showing a control example according to the present invention.

FIG. 6 is a graph showing the relationship between road surface μ and reference deceleration.

FIG. 7 is a flow chart showing a control example according to the present invention.

[Explanation of symbols]

 1FR to 1RL Wheels 7FR to 7RL Brake Device 11 Master Cylinder 12 Brake Pedal 14, 15 Brake Pipe 14FR, 14FL Branch Pipe 15RR, 15RL Branch Pipe 21FR, 21FL, 21R Hydraulic Pressure Adjustment Mechanism U Control Unit S1 to S4 Wheel speed sensor

Claims (2)

[Claims] 1. An anti-skid brake device for a vehicle, wherein a braking force reduction control is performed so that the wheels do not lock during braking, and deceleration / deceleration detection means for detecting deceleration / deceleration of the wheels. After determining that the sign of the deceleration detected by the deceleration detecting unit is reversed, and determining that the sign of the deceleration is reversed by the determining unit, the braking force reduction control is performed. An anti-skid brake device for a vehicle, comprising: an ending means for ending. 2. The deceleration detecting means according to claim 1, further comprising deceleration detecting means for detecting deceleration of the wheel, wherein the ending means detects the deceleration by the sign of the deceleration and the deceleration detecting means. When the deceleration rate becomes less than a predetermined value, the control to reduce the braking force is terminated.