JPH03118263A - Antilock control method of vehicle - Google Patents

Abstract

PURPOSE:To obtain an efficient braking force and to suppress the generation of a car body vibration by preparing a map to display the values of the acceleration and the deceleration of the control object car wheel speed, and the relation of the difference of the object speed and the control object car wheel speed, and carrying out the increase and reduction of the braking fluid pressure by reading out the map. CONSTITUTION:While the system speed Vs is calculated 12 from the outputs of car wheel rotation speed sensors 1 in a control unit 2 in the operation of a vehicle, a dummy car body speed Vv is calculated 13 by selecting the highest car wheel speed of the four car wheel speeds. And, while an object speed VT following the dummy car body speed Vv with a specific speed difference is calculated 14, the difference E between the system speed Vs and the object speed VT is calculated 15. And by a control device 18 having a memory to store a control map 18a in which the difference E is made as the axis of abscissas and the acceleration/deceleration dVs/dt of the system speed Vs is made as the axis of ordinates, a control value is read out to control a hold valve 6 and a decay valve 7, and the increase maintenance and reduction of the brake fluid pressure is carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an anti-lock control method for preventing wheels from locking during braking of a traveling vehicle.

(Prior art) In general, anti-lock control devices for vehicles convert wheel speeds detected by wheel speed sensors into electric signals for the purpose of ensuring vehicle steering performance and running stability and shortening braking distance during braking. Based on this, the brake fluid pressure control mode is determined, and a hold valve consisting of a normally open solenoid valve and a decay valve consisting of a normally closed solenoid valve are opened and closed to increase, maintain, or reduce the brake fluid pressure. It is controlled by a control unit containing a microcomputer.

By the way, in the conventional anti-lock control method, the controlled wheel speed (
A reference speed for determining pressure reduction is set based on the system speed (hereinafter referred to as system speed Vs). In addition, a speed with a predetermined hU speed/deceleration follow-up limit set for the fastest wheel speed among the four wheel speeds is set as the pseudo vehicle speed Vv, and a certain speed is lower than this pseudo vehicle speed VV. A threshold speed is set for tracking with a speed difference. Then, each status of depressurization, holding, and pressurization is determined based on the comparison between the system speed Vs and the reference speed or threshold speed, and also based on the detection of the high peak point and low peak point of the system speed Vs. settings, and predetermined restrictions 2 set for each of these statuses.
'BB's multiple hydraulic control valves made of electromagnetic solenoid valves are turned off to reduce, maintain, and increase pressure.

However, when performing such control, when a sudden change in wheel speed occurs due to a change in the road surface, the control mode remains fixed and does not change until the status changes, resulting in a delay in response. be. This is particularly a problem when the wheels lock up due to sudden braking. In addition, since pressurization is applied when the wheel speed has recovered to near the vehicle body speed, the wheel speed repeatedly accelerates and decelerates around a speed with a certain slip ratio in response to changes in the vehicle body, and as a result, the brake fluid pressure increases. There was a problem in that vibrations were generated in the vehicle body because the pressurization and depressurization were performed.

(Object of the Invention) Therefore, an object of the present invention is to provide an anti-lock control method that can solve the various problems in the conventional anti-lock control 2B method described above all at once.

(Structure of the Invention) In the present invention, a target speed VT is set to follow the pseudo vehicle speed VV, which is calculated based on the fastest wheel speed among the four wheel speeds during braking, in a predetermined relationship. Then, the pressure application region and pressure reduction region of the brake fluid pressure, and the magnitude of the pressure application gradient and pressure reduction gradient in the above-mentioned pressure application region and pressure reduction region, respectively, are determined by the control target wheel speed V
A map is prepared that expresses the relationship between the acceleration and deceleration values of s and the difference between the target speed VT and the control target wheel attainment Vs, and by reading this map, it is possible to increase or decrease the brake fluid pressure. I try to do this.

(Example) Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram of a control system applied to a first embodiment of the present invention. In FIG. 1, 1 is a wheel rotation speed sensor attached to each of the four wheels, 2 is a control unit consisting of a computer, 3 is a mask cylinder operated by a brake pedal 4, and 5 is a normally open Nm valve. A modulator includes a hold valve (HV) 6 and a decay valve (DV) 7 which is a normally closed solenoid valve. 8 is a reservoir, and brake fluid is pumped up from this reservoir 8 by a pump 9 to an accumulator 1.
It is configured to store 0.

4a is a brake switch that is turned on when the brake pedal 4 is depressed, and II is a wheel cylinder of a wheel brake device.

The control unit 2 includes a speed calculation means 12 that calculates the system speed Vs from the output of each wheel rotation speed sensor l;
A pseudo vehicle speed calculating means 13 which selects (select high) the fastest wheel speed among the four wheel speeds Vw and obtains a pseudo vehicle speed Vv through a filter of acceleration/deceleration ±IG; A target speed calculation means 14 calculates a target speed VT to be followed with a constant speed difference, and a difference E (=V
s-VT). Furthermore, the control unit 2 includes acceleration/deceleration calculation means 16 for calculating acceleration/deceleration dVs/dt of the system speed Vs. Reference numeral 18 denotes a control unit, and the memory of this control unit 18 stores a control map as shown in FIG.
The difference E between the target speed VT and the system speed Vs obtained from 5.
The horizontal axis represents the acceleration/deceleration dVs/dL of the system speed Vs obtained from the acceleration/deceleration calculation means 16, and the vertical axis represents the pressurization area, holding area, and depressurization area of the brake fluid pressure. Furthermore, the magnitude of the pressure gradient and the pressure reduction gradient in the pressure region and the pressure reduction region are shown as control values.

The pressure gradient determines the duty ratio of the pressure signal applied to the hold valve, and the pressure reduction gradient determines the duty ratio of the pressure reduction signal applied to the decay valve. The control unit I8 is configured to perform control from the control map (by reading the direct value) to ON/OFF control the hold valve 6 and the decay valve 7 to pressurize, maintain, and reduce the brake fluid pressure in the wheel cylinder 11. There is.

Next, an example of the anti-lock control according to this embodiment will be described with reference to FIG. 3 showing a control time chart and FIG. 4 showing a control flow chart.

First, to explain each status shown in Fig. 3, [Status 0] The brake switch 4 is turned OFF by pressing the brake pedal.
The deceleration of system speed dVs/dt from the time it reaches N
A time point B when it is determined that has reached a predetermined deceleration -Gmay,
Or until the time when it is read out from the above map that it is in the holding area. The bold pulp 6 is in a closed state, the decay valve 7 is in a closed state, and the brake fluid in the wheel cylinder 11 rises due to the brake fluid sent from the mask cylinder 3.

(Status I) -C; wax: II! From fixed point B until the point in time when the pressure reduction value is input to the control value from the map, the hold valve 6 closes at point B, and the brake fluid pressure is maintained. .

[Status 2] From the time when the depressurization value is input as the control value from the map until the time when the pressurization value is continuously input as the control value for a predetermined period of time. In this status, the brake fluid pressure is reduced, maintained, or increased based on the control value read from the map.

Next, the flowchart shown in FIG. 4 will be explained.

First, in step S1, the acceleration/deceleration of the system speed dVs/
dt is calculated, and in the next step s2, the difference E (=Vs - VT) between the system speed Vs and the target speed VT is calculated.In the first step s3, the acceleration obtained in the above steps S1 and S2 is calculated. - Based on the value of the deceleration dVs/dt and the speed difference E, the control value is read out from the control map (FIG. 2). In step S4, it is determined whether the status is 2 or not. That is, it is determined whether a pressure reduction value has been input as a control value from the map. Since the current determination result in step S4 is "NO", the process proceeds to step s5, where it is determined whether the deceleration dVs/dt of the system speed has reached the predetermined deceleration - Glla. If the determination result here is rNOJ, the status is set to 0 in step S6, and if rYEsJ, the status is set to 1 in step S7, and the process proceeds to the next step S8.In step S8, the control value from the map is set. Determine whether or not the decompression value was manually set.

If it is determined to be rYEsJ, set status 2 (step s9) and check the system read from the map.
■Determine the control mode based on the value, determine the duty ratio of the pressurization signal applied to the hold valve HV or the duty ratio of the pressure reduction signal applied to the decay valve DV, and open/close the bold valve HV and decay valve DV. Step 310), in which the brake fluid pressure is pressurized, maintained, or depressurized, in the 0th step Sll, it is determined whether the pressurization value has been continuously input for a predetermined period of time as a control value from the map. While the determination result is rNOJ, the process returns to step s1, but if the determination result is rYEsJ, the bold pulp HV and decay valve DV are returned to the normal braking state B (non-anti-lock control state).

That is, the hold valve HV is set to 0FF (open) and the decay valve DV is set to 0FF (closed) (step 512).
The status is set to 0 (step 513).

Next, a second embodiment of the present invention will be described.

FIG. 5 is a block diagram of a control system applied to the second embodiment of the present invention. In the configuration shown in FIG. 5, the control section 18
The configuration is the same as that shown in FIG. 1 described above, except for the control map stored in the control map and the speed calculating means 17, so common parts are given the same reference numerals and redundant explanations will be omitted.

The speed difference calculation means 17 is a means for calculating the difference ΔV (-Vv-VT) between the pseudo vehicle speed Vv obtained from the calculation means 13 and the target speed VT obtained from the calculation means 14. In the case of this embodiment, as shown in FIG.
T is set to follow the Iu simulated vehicle speed Vv at a constant ratio, and therefore the difference ΔV (-VvVT) between the two speeds is a variable amount that changes depending on the simulated vehicle speed Vv. . Further, a control map as shown in FIG. 7 is stored in the memory of the control unit 18 shown in FIG. 5, and this control map, like the map in FIG. The horizontal axis is the difference E from Vs, and the system speed V
The vertical axis represents the acceleration/deceleration dVs/dt of s, and shows the pressurization area, holding area, and depressurization area of brake fluid pressure, and also shows the magnitude of the pressurization gradient and pressure reduction gradient in the pressurization area and depressurization area. is shown as a control value. However, in the control map shown in FIG. 7, the scale of the horizontal axis is changed according to the value of the speed difference ΔV when reading the map. It is different from That is, for the pseudo vehicle speed Vv, the formula VT=VvXl ((however,
O < K < 1) The difference ΔV (= Vv - VT) between the target speed VT and the virtual vehicle body speed Vv is calculated, and the value of this ΔV is taken as the full scale of the horizontal axis centered on zero. .

For example, if ΔV=I□km/hour, the full scale of the horizontal scale of the control map above is ±l with the center at zero.
Qk@/hour, and ΔV = 5 km At 7 o'clock, the full scale of the scale on the horizontal axis is ± around zero.
The speed will be 5km/hour. Therefore, even with one control map, it is possible to effectively use the entire area of the map regardless of the magnitude of the speed difference ΔV, and this makes it possible to converge the system speed Vs to the target speed VT faster, and to Efficient control can be performed.

Next, FIG. 8 is a flowchart of control when executing the second embodiment of the present invention. This flowchart shows the fourth
Step S14 and step 515 are added between steps S2 and 83 in the flowchart shown in the figure.

That is, in FIG. 8, steps S1 and S2
After calculating dVs/dt and speed difference E,
Proceeding to the next step S14, the difference ΔV (-Vv-VT) (7) between the pseudo vehicle speed VV and the target speed VT is calculated, and in the next step S15, the full scale of the axis indicating the speed difference E on the control map is calculated. , is set to the value of the speed difference Δ■ obtained in step 514, and the process proceeds to the next step S3.

According to the second embodiment of the present invention, as described above, the scale of the axis representing the difference between the target speed VT and the system speed Vs of the control map is changed in accordance with the value of the speed difference Δ■. Therefore, even if the difference ΔV between the target speed VT and the pseudo vehicle speed Vv changes, the entire area of the control map can be used. Therefore, the system speed Vs converges quickly with respect to the target speed VT, and more efficient control can be performed.

(Effects of the Invention) As is clear from the above description, the present invention provides a target that follows a pseudo vehicle speed VV in a predetermined relationship, which is calculated based on the fastest wheel speed among the four wheel speeds during braking. Speed VT is set. Then, the pressure increase region and pressure decrease region of the brake fluid pressure and the magnitude of the pressure increase gradient and pressure decrease gradient in each of these regions are determined based on the acceleration and deceleration values of the system speed Vs, and the target speed VT and system speed Vs. A control map as shown in FIG. 2 is prepared in relation to the difference, and the brake fluid pressure is increased and decreased by reading this map. Therefore, unlike anti-lock control in conventional methods, the adoption of a control map not only determines the control modes of pressurization, holding, and depressurization and their periods, but also determines the pressurization gradient in the pressurization mode or the depressurization gradient in the depressurization mode. In order to perform control that also sets the magnitude of the system speed Vs
It becomes possible to converge to the target speed V'r.

In this case, the brake fluid pressure is maintained near the required level, and the amplitude of fluctuations in the system speed Vs is also reduced, ensuring efficient braking force and suppressing the occurrence of vehicle body vibration.

In addition, for sudden changes in the system speed Vs due to changes in road surface conditions (for example, when entering from a high μ road to a low μ road), even if the system speed Vs exceeds the target speed VT, the system speed Vs If the vehicle is decelerating, the brake fluid pressure can be reduced, so the starting point for pressure reduction can be obtained quickly, allowing for quick response.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a control system applied to a first embodiment of the anti-lock control method according to the present invention, FIG. 2 is a control map thereof, and FIG. 3 is a timing chart of the control.
Fig. 4 is a flowchart, Fig. 5 is a block diagram of a control system applied to the second embodiment of the present invention, Fig. 6 is a diagram showing its target speed, Fig. 7 is its control map, and Fig. 8 is a flowchart. 1-Wheel rotation speed sensor 2-Control unit 3--Mask cylinder 4-Brake beta 5-
Modulator 6-hold normal valve 7-decay valve 8. Lizer/519-Pump 1
0-accumulator 18-control section

Claims (1)

[Scope of Claims] A vehicle in which brake fluid pressure is alternately increased or decreased based on the detection of controlled wheel speed Vs in each brake control system, thereby preventing wheels from locking during braking. In the anti-lock control method, a target speed VT is set to follow a pseudo vehicle speed Vv calculated based on the fastest wheel speed among the four wheel speeds during braking in a predetermined relationship, and the brake fluid pressure is increased. The area and depressurization area, and the magnitude of the pressurization gradient and the depressurization gradient in each of the pressurization area and the pressure reduction area, the acceleration and deceleration values of the control target wheel speed Vs, the target speed VT, and the control target An anti-lock control method for a vehicle, characterized in that a map is prepared that expresses the relationship between the brake fluid pressure and the wheel speed Vs, and the brake fluid pressure is increased or decreased by reading this map.