JP2000118376A - Antilock control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain excess slip of a wheel and vibration of a car body by regulating rising of a brake pressure of the other driving wheel synchronizing to depression mentioned below, when a slip occurs at one driving wheel in advance just after starting of control, and this caused depression of brake pressure of the driving wheel. SOLUTION: Calculation of an antilock control is performed in a control logic circuits 6, 7, and a hold valve HV and decay valve DV for each system are controlled ON/OFF. When, during this control, a slip occurs on a wheel running on the low μ road side and subsequently a slip occurs on a wheel running on the high μ road side, only before the wheel on the low μ road side starts second depression, and in a first control cycle of the antilock control of the wheel on the high μ road side, the wheel on the high μ road side is simultaneously forcibly depressed synchronizing to the wheel on the low μroad side depressed in advance. Occurrence of an excess slip of the wheel on the high μ road side is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-lock brake control device for independently controlling the brake pressure of the left and right wheels, wherein the left and right wheels enter a road surface (.mu. Split road surface) having a friction coefficient different from each other and have a low .mu. When the slip occurs first, the brake pressure on the wheels running on the road surface with a high friction coefficient is regulated to raise the brake pressure, causing a slip due to an excessive increase in the brake pressure on the wheels with the high friction coefficient. The present invention relates to an anti-lock control method that can prevent the lock operation.

[0002]

2. Description of the Related Art When a sudden braking is applied to a running vehicle, the frictional force between the road surface and the tires is limited, so that the wheels are locked and the wheels are slipped. As means for preventing the locking phenomenon, there is known an anti-lock control device that controls a slip ratio of a wheel to a road surface and controls a braking force so that a slip ratio between the road surface and the wheel is always set to a predetermined value.

[0003]

In the antilock control method for independently controlling the left and right driving wheels, only one wheel passes on a road surface having a low friction coefficient such as an icy road surface (hereinafter referred to as a low μ road). When the anti-lock control is started prior to the wheel, the rotational force is circulated to the other drive wheel traveling on the high μ road side due to the influence of the differential gear, and the wheel on the high μ road side is unlikely to slip. In other words, a situation arises in which the required hydraulic pressure on the braking road surface is greatly exceeded and an excessive brake is applied. In this state,
When the wheel slip on the low μ roadside is eliminated and the wheel speed recovers, the circulation of rotational force to the high μ roadside wheel stops,
There is a problem that an excessive slip occurs on the high μ road side wheels due to the influence of the above-mentioned large hydraulic pressure, and vibration of the vehicle body occurs. Especially for high μ roadside wheels, the first
Until the start of pressure reduction in the cycle, the brake fluid pressure rises quickly, the overshoot of the fluid pressure also increases, the wheel slip increases, and the stability of the running state decreases.

[0004] Accordingly, the present invention provides a brake system that operates while the left and right wheels are running on a road surface having a different coefficient of friction, and when a slip occurs before the wheels running on the low μ road side, the low μ road side Before the wheel becomes the second decompression start point, and
Only in the first control cycle of the anti-lock control of the wheels on the high μ roadside, the wheels on the high μ roadside are simultaneously switched to the forced depressurization mode or the gentle pressurization mode in synchronization with the depressurized low μ roadside wheels. An object of the present invention is to solve the above-described problem by preventing the occurrence of excessive slippage of roadside wheels. According to the present invention, since excessive brake pressure does not act on the braking road surface on the wheels on the high μ road side, excessive slip of the wheels and vehicle body vibration can be suppressed.

[0005]

Therefore, the technical solution adopted by the present invention is an antilock brake control method for independently controlling the brake pressures of the left and right wheels. When the brake pressure of the same drive wheel is reduced by this, a pressure increase of the brake pressure of the other drive wheel is regulated in synchronism with the reduced pressure. is there.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an antilock control device according to an embodiment of the present invention, and FIG. FIG. 3 is a flowchart of the lock control, and FIG. 3 is a diagram showing the relationship between the brake pressure and the wheel speed of the wheels traveling on the high μ road side and the low μ road side when performing the antilock control of the present embodiment. Note that this control can be applied to both hydraulic brake control and pneumatic brake control.

In FIG. 1, reference numeral 1 denotes a left driving wheel speed sensor,
Reference numeral 2 denotes a right driving wheel speed sensor. The outputs of the wheel speed sensors 1 and 2, which are frequency signals, are sent to arithmetic circuits 3 and 4 and calculated, and signals representing the wheel speeds Vw1 and Vw2 are obtained. Left drive wheel speed Vw1 and right drive wheel speed V
w2 is sent to the pseudo vehicle speed calculating circuit 5, where the fastest wheel speed among the left and right driving wheel speeds Vw1 and Vw2 is selected (high select), and the following limit of the fastest wheel speed is limited to ± 1G. The speed is calculated as pseudo vehicle speed Vv.

The wheel speeds (control speeds) Vw1 and Vw2 from the operation circuits 3 and 4 and the pseudo vehicle speed Vv obtained from the pseudo vehicle speed operation circuit 5 are input to control logic circuits 6 and 7. In the control logic circuits 6 and 7, antilock control calculation is performed, and ON / OFF control of the hold valve HV and the decay valve DV of each system is performed. During this control, when a slip occurs on a wheel traveling on a low μ road side and subsequently a slip occurs on a wheel traveling on a high μ road side, the wheel on the low μ road side starts the second decompression start point. Before and only in the first control cycle of the anti-lock control of the wheels on the high μ road side, the wheels on the high μ road side are simultaneously forcibly depressurized in synchronization with the wheels on the low μ road side which have been previously depressurized. , A control (to be described in detail later) for preventing the occurrence of excessive slip of the wheels on the high μ road side.

Hereinafter, the antilock control will be described in detail with reference to the flowchart of FIG. When the present brake pressure control program is started, first, when the present program is started in step S1, it is determined in step S2 whether or not the left and right driving wheels are under forced synchronous pressure reduction. When the pressure is not the forced synchronous pressure reduction, the process proceeds to step S3 to determine whether the gear of the transmission is engaged (that is, whether the vehicle is in the driving state).
When the gear is engaged, it is determined in step S4 whether or not the present control is being executed. When the gear is not engaged, the power is not transmitted to the driving wheels, so that there is no excessive slippage of the wheels on the other side due to the action of the differential, so that this control is not necessary.

When the vehicle is not controlled in step S4, the process proceeds to step S5 to determine whether or not the right and left opposite wheels are in a pressure reduction mode. To start. That is, in this step, the forced synchronous pressure reduction is started before the wheels on the high μ road side are in the holding mode immediately before the antilock control is started or immediately after the start of the antilock control. The decompression amount of the forced decompression can be set to the same decompression amount as that of one wheel, or to a decompression amount set at a predetermined ratio. Also, when the forced synchronous pressure reduction is already being performed in step S2,
Proceeding to step S7, it is determined whether the left and right opposite wheels are in the holding or pressurizing mode. When one of the wheels is in the holding or pressurizing mode, the process proceeds to step S10, and the other wheel is set in the pressurizing mode, and the forced synchronous decompression is ended in step S11.

When the left and right opposite wheels are not in the holding or pressurizing mode in step S7, the process proceeds to step S8, and a predetermined time (this time is determined by an actual vehicle test but set to, for example, 50 ms) has elapsed from the start of synchronous pressure reduction. In this case, the process proceeds to step S10, and the pressure mode is set.
At 11, the forced synchronous pressure reduction is completed. If the predetermined time has not elapsed since the start of the synchronous pressure reduction in step S8, it is determined in step S9 whether or not the apparatus is in the self-pressure reduction mode. The forced synchronous decompression is ended, and if not, the process returns to step S1.

FIG. 3 shows the state of the wheel speed and the brake pressure on the μ split road described above. In FIG. 3, the brake is activated during traveling, the brake pressure is increased, and a slip phenomenon occurs on the driving wheels traveling on the low μ road side ahead of time, and the speed of the low μ road side wheel RR) decreases by ΔV1 and becomes a threshold. When the value falls below the value VT (point A), the pressure reduction of the brake pressure on the low μ road side is started. After the start of depressurization, decompression is continued until the wheel speed reaches a low peak (point B), and the wheel speed recovers due to the reduction of the brake pressure, passes the low peak (point B), and brakes until the high peak (point C). The pressure is maintained, and after the high peak (point C), the brake pressure is again increased, and the same brake pressure control is repeated thereafter.

On the other hand, in the high μ roadside wheel (RL), when the pressure reduction in the first cycle of the control of the low μ roadside wheel is started (point A), as shown by the dotted line in FIG. Synchronously, the brake pressure is reduced, and the low μ roadside wheels (R
When the wheel speed of R) reaches a low peak (point B), the mode is switched to the pressurizing mode, the brake pressure is increased, and the normal brake pressure control is repeated thereafter.

Next, a second embodiment of the present invention will be described. In the second embodiment, a slip occurs prior to a wheel traveling on a low μ road side, and the first cycle of control of the low μ road side wheel is performed. At the time when the eye pressure reduction is started, the brake pressure of the high μ road side wheel is gradually increased as shown by the two-dot chain line in FIG. 3 to prevent the occurrence of excessive slip of the high μ road side wheel. is there. The second embodiment will be described with reference to the flowchart shown in FIG. When this program relating to the forced synchronous pressure reduction of the drive wheels is started in step SS1,
In step SS2, it is determined whether the left and right driving wheels are in the forced gentle pressurization mode or the forced hold mode. If not in the forced gentle pressurizing mode or the forced holding mode, step SS3
Then, it is determined whether or not the gear of the transmission is engaged (i.e., whether or not the vehicle is in a drive state). If the transmission is in the gear engaged state, it is determined in step SS4 whether or not the present control is being executed. When the gear is not engaged, the power is not transmitted to the driving wheels, so that there is no excessive slippage of the wheels on the other side due to the action of the differential, so that this control is not necessary.

When the vehicle is not controlled in step SS4, the process proceeds to step SS5 to determine whether or not the left and right opposite wheels are in a pressure reduction mode.
At S6, the forced loose pressure mode or the forced holding mode of the other wheel is executed. The ratio of the gentle pressurization is set by a test using an actual vehicle or the like. When the left and right driving wheels are already in the forced gently pressurizing mode or the forced holding mode in step SS2, it is determined in step SS7 whether a predetermined time has elapsed from the start of the forced gently pressurizing or forced holding, and the lapse of the predetermined time has elapsed. If so, the process proceeds to step SS9 to set the pressure mode, and further proceeds to step SS10 to end the forced gentle pressure mode or the forced holding mode.
If it is determined in step SS7 that the predetermined time has not elapsed, the process proceeds to step SS8, in which it is determined whether or not the pressure reduction mode is set by self-pressure reduction.
Returning to 1 (or terminating), and in the pressure reducing mode, the process proceeds to step SS10 to terminate the forced gentle pressurizing mode or the forced holding mode.

Next, the state of the wheel speed and the brake pressure in the second embodiment will be described with reference to FIG. In FIG.
When the brake is operated during traveling and the brake pressure increases, the speed of the low μ roadside wheel (RR) decreases by ΔV1 and falls below the threshold value VT (point A), the brake pressure of the low μ roadside wheel (RR) is reduced. Be started. After the start of decompression, the decompression is continued until the wheel speed exceeds the low peak (point B), and after the wheel speed recovers due to the reduction of the brake pressure, after passing the low peak (point B), until the high peak (point C). The brake pressure is maintained, and after the high peak (point C), the brake pressure is again increased, and the same brake pressure control is repeated thereafter.

On the other hand, in the high μ roadside wheel (RL), when the pressure reduction in the first control cycle of the low μ roadside wheel is started (point A), as shown by a two-dot chain line in FIG. At this point, the brake pressure is switched to the gentle pressurization mode, and the gentle pressurization of the brake pressure is started.

Thus, in this embodiment, when the left and right wheels operate the brakes on the road surface having different friction coefficients and the slip occurs prior to the wheels traveling on the low μ road side, the high μ road side The brake pressure of the wheels is forcibly reduced at the same time. As a result, excessive brake pressure does not act on the braking road surface on the high μ road side wheel, and excessive slip of the wheel and vehicle body vibration can be suppressed. Further, the present control is effective not only for the right and left μ split roads but also for the same phenomenon due to a difference in braking effect in which a braking force difference occurs between the left and right wheels.

[0019]

As described in detail above, according to the present invention,
Since the forced pressure reduction on the high μ road side performed in synchronization with the low μ road side does not depend on the slip time of the low μ road side wheels, insufficient deceleration due to excessive forced pressure reduction on the high μ road side can be avoided. Since excessive brake pressure does not act on the braking road surface on the wheels on the high μ road side, excessive slip of the wheels and vehicle body vibration can be suppressed. For this reason, the braking force of the wheels can be effectively used in any road condition, and an excellent effect that stable vehicle traveling can be achieved can be achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram of an antilock control device according to a first embodiment of the present invention.

FIG. 2 is a flowchart of antilock control according to the first embodiment.

FIG. 3 is a diagram illustrating a relationship between brake pressure and wheel speed of a wheel on a low μ road side and a wheel on a high μ road side.

FIG. 4 is a flowchart of antilock control according to a second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Left drive wheel speed sensor 2 Right drive wheel speed sensor 3, 4 Operation circuit 5 Pseudo vehicle speed operation circuit 6, 7 Control logic circuit

Claims (2)

[Claims] An anti-lock brake control method for independently controlling the brake pressures of the left and right wheels.
When a slip occurs prior to one of the drive wheels and the brake pressure of the drive wheel is reduced by this, the increase in the brake pressure of the other drive wheel is regulated in synchronization with this reduction. Antilock control method. 2. The anti-lock control method according to claim 1, wherein the anti-lock control is performed when the transmission gear is in a driving state.