JPH05116612A - Slip control device for vehicle - Google Patents

Abstract

PURPOSE:To perform optimum slip control according to the degree of unevenness of a road surface without deterioration of control responsiveness or burden on a control unit by changing a start condition so as to hardly start the slip control when the degree of unevenness of the road surface is large. CONSTITUTION:Respective detected signals from respective sensors S1-S4 to detect rotating speed of respective wheels, an accelerator switch S5, and respective brake switches S6, S7 are respectively input to a control unit U. The control unit U outputs respective control signals to hydraulic pressure adjusting valves 15R, 15L of front wheels namely drive wheels, opening/closing valves 16R, 16L of rear wheels, a three-way electromagnetic changeover valve 38, and a torque adjusting means 9 for an engine. In this case, when a prescribed condition is satisfied, the control unit U start slip control to reduce given torque to the drive wheels. Further, the degree of unevenness of a road surface is detected. When the degree of unevenness of the road surface is large, the start condition is changed so as to hardly start the slip control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle slip control device for preventing excessive slip of driving wheels on a road surface.

[0002]

2. Description of the Related Art Various slip control devices (traction control devices) have been proposed to prevent excessive slippage of driving wheels on a road surface during acceleration of a vehicle and to satisfy acceleration and vehicle stability. ing.

The above slip control is performed by reducing the torque applied to the drive wheels. Therefore, the brake control that applies a brake force to the drive wheels and the engine that reduces the torque (output) generated by the engine are performed. Control is performed. It has been proposed that the slip control be performed by both the brake control and the engine control, or by the brake control alone or the engine control alone. And
In both the brake control and the engine control, the feedback control is generally performed so that the actual slip value of the driving wheel on the road surface becomes a predetermined target value.

By the way, the actual slip value of the drive wheel with respect to the road surface is greatly changed according to the degree of unevenness of the road surface. That is, when trying to run in the same state, the actual slip values of the drive wheels are considerably different between when running on a flat road and when running on a rough road with severe unevenness. More specifically, on a bad road, contact and separation of the drive wheels with respect to the road surface are performed considerably violently, so that the slip value becomes large when the drive wheels are separated from the road surface. Therefore, if the slip control is performed on the good road and the bad road under the same conditions, even if the good slip control is performed on the good road, the temporary occurrence that occurs when the drive wheels are separated from the road surface on the bad road is achieved. Due to such a large slip value, the slip control is such that the torque applied to the drive wheels is excessively reduced.

Japanese Unexamined Patent Publication No. 64-106762 discloses a method for filtering the detected value of the driving wheel speed in order to perform an appropriate slip control according to the degree of unevenness of the road surface, that is, the degree of bad road. More specifically, while performing a kind of smoothing process on the drive wheel speed used for slip control by filtering, the greater the degree of unevenness of the road surface, the greater the degree of this smoothing, and the temporary unevenness caused by the unevenness of the road surface. Such a large change in the slip value of the drive wheel is not directly reflected in the slip control.

[0006]

However, performing the slip control by filtering the driving wheel speed is not preferable in order to perform the slip control with good response. In addition to this, there is a problem in that the load on the control unit is increased due to the filtering.

Therefore, an object of the present invention is to provide a slip control for a vehicle which is capable of performing an appropriate slip control according to the degree of unevenness of the road surface without deteriorating the responsiveness of the slip control and imposing a heavy load on the control unit. To provide a device.

[0008]

To achieve the above object, the present invention has the following configuration. That is, in a vehicle slip control device that prevents the slip value of the drive wheel from becoming excessive on the road surface by reducing the torque applied to the drive wheel, when the drive wheel meets a predetermined start condition, The starting means for starting the slip control for reducing the torque applied to the road surface, the rough road degree detecting means for detecting the rough road degree indicating the unevenness of the road surface, and the rough surface degree for the road surface detected by the rough road degree detecting means When it is large, as compared with when it is small, the starting condition changing means for changing the starting condition is set so that the slip control is less likely to be started.

[0009]

According to the present invention, the start condition of the slip control is set according to the degree of unevenness of the road surface so that when the degree of unevenness of the road surface is large, the slip control is less likely to be started than when it is small. To be This prevents a situation in which the slip control is unnecessarily started due to a temporary large slip of the drive wheels caused by the large unevenness of the road surface, and the drivability on a rough road is improved. In addition, when the degree of unevenness of the road surface is small and it is difficult to cause a large temporary slip of the drive wheels, slip control can be easily started to prevent excessive slip of the drive wheels while improving acceleration and vehicle body. The stability of can be sufficiently secured.

In the present invention, since it is not necessary to perform the smoothing process on the driving wheel speed itself to control the slip,
There is no problem in the responsiveness of the slip control, and the burden on the control unit is reduced because the smoothing process does not need to be performed unnecessarily. Preferred aspects of the invention and advantages thereof will become apparent from the description of the examples below.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, 1FL is a left front wheel, 1FR is a right front wheel, 1RL is a left rear wheel, and 1RR is a right rear wheel. The engine 2 is horizontally mounted on the front part of the vehicle body, and the torque generated by the engine 2 is transmitted to the clutch 3, the transmission 4, and the differential gear 5, and then the left front wheel is passed through the left drive shaft 6L. 1FL and is transmitted to the right front wheel 1FR via the right drive shaft 6R. In this way, the vehicle has front wheels 1F.
L and 1FR are the driving wheels, and the rear wheels 1RL and 1RR are the driven wheels, which are the driven wheels.

Brake 7FR to 7R mounted on each wheel
R is a hydraulic disc brake.
In addition, the master cylinder 8 as a source of brake fluid pressure is generated.
Is a tandem type having two discharge ports 8a and 8b. The break pipe 13 extending from one discharge port 8a of the master cylinder 8 is branched into two in the middle,
The branch pipe 13F is connected to the left front wheel brake 7FL (the wheel cylinder mounted in the caliper), and the branch pipe 13R is connected to the right rear wheel brake 7RR.
The branch pipe 14 extending from the other discharge port 8b of the master cylinder 8 is also branched into two, the branch pipe 14F is connected to the right front wheel brake 7FR, and the branch pipe 14R is connected to the left rear wheel brake 7RL. It is connected.

Branch pipe 13 for front wheels, that is, for drive wheels
Electromagnetic hydraulic pressure adjusting valve 15L or 1 is provided on F and 14F.
5R is connected, and an electromagnetic opening / closing valve 16L or 16R is connected to the branch pipes 13R and 14R for the rear wheels. The hydraulic pressure adjusting valves 15L and 15R are the brake 7FL,
The brake fluid pressure supply from the master cylinder 8 to the 7FR and the brake fluid pressures of the brakes 7FL and 7FR are provided in the pipe 2
The mode of switching to the reservoir tanks 22L and 22R via 1L and 21R is switched. The brake liquid in the reservoir tank 21L is returned by the pump 23L to the pipe 13 through the pipe 25L to which the check valve 24L is connected. Similarly, the brake liquid in the reservoir tank 22R is pumped by the pump 23L.
By R, the check valve 24R is returned to the pipe 14 via the pipe 25R to which the check valve 24R is connected.

The stepping force on the brake pedal 12 is
It is transmitted to the master cylinder 8 via a booster or brake booster 11. This booster 11 is basically the same as a known vacuum booster, but during slip control, as will be described later, even if the brake pedal is not stepped on, a boosting action is exerted. Is configured to do.

The booster 11 has a case 31 fixed to the vehicle body and the master cylinder 8, and the inside of the case 31 is formed by a diaphragm 32 and a valve body 33 fixed thereto. A chamber 34 and a second chamber 35 are defined. Negative pressure (for example, intake negative pressure of the engine 2) is constantly supplied to the first chamber 34, and when the brake pedal is not depressed, the second chamber 35 is communicated with the first chamber 34, and -The operation of the star 11 is stopped. Then, when the brake pedal 12 is depressed,
The communication between both chambers 34 and 35 is cut off, and the second chamber 35
Atmospheric pressure is supplied to the diaphragm 32, whereby the diaphragm 32 is displaced forward together with the valve body 33 to perform a boosting function.

The switching between the negative pressure supply and the atmospheric pressure supply to the second chamber 35 is basically performed by the valve device provided in the valve body 33. This valve body 33
The part will be described with reference to FIG.

First, the valve body 33 has a power piston 41 fixed to the diaphragm 32, and a recess 41a formed in the power piston 41 has a reaction disk 42 and a base end portion of the output shaft 43. And are fitted. The output shaft 43 serves as an input shaft of the master cylinder 8. Further, a valve plunger 45 is attached inside the valve body 33 at the tip of the input shaft 44 connected to the brake pedal 12. A vacuum valve 46 is arranged behind the valve plunger 45.

The power piston 41 has a pressure introducing passage 50.
The pressure introducing passage 50 is always communicated with the space X formed around the valve plunger 45. This space X is always communicated with the second chamber 35. A valve seat 47, on which the vacuum valve 46 is seated, is formed at the end of the pressure introducing passage 50 that opens toward the space X. In addition, the vacuum valve 46 is a valve plunger 45.
The valve seat 45a formed at the rear end is also seated on and off.

In the above structure, it is assumed that a negative pressure is being introduced into the pressure introducing passage 50. In this state, when the brake pedal 12 is not depressed, the vacuum valve 46 is seated on the valve seat 45a by the urging force of the springs 48 and 49 in the state of FIG. 2, but is separated from the valve seat 47. ing. Therefore, the pressure introducing passage 5
The negative pressure from 0 is introduced into the second chamber 35 through the space X, and the boosting action is not performed.

When the brake pedal 12 is depressed,
The input shaft 44 and hence the valve plunger 45 are moved forward (moved leftward in the drawing). During this forward movement, the vacuum valve 46
Is first seated on the valve seat 47, and the space X and the pressure introducing passage 50 are
Communication with the vacuum valve 46 and then the valve seat 45
a is separated. By separating the vacuum valve 46 and the valve seat 45a, the atmospheric pressure from the rear of the valve body 33 is introduced into the space X, and the second chamber 35 becomes the atmospheric pressure. As a result, the diaphragm 32 is displaced forward together with the valve body 33, and as a result, the output shaft 43 moves forward and a boosting action is performed. The brake reaction force from the master cylinder 8 is transmitted to the valve plunger 45 and thus the brake pedal 12 via the reaction disc 42.
When the stepping operation force of the brake pedal 12 is released, the return spring 36 (see FIG. 1) returns to the state of FIG. 2 to prepare for the next boosting action.

The part described above is the same as the known vacuum booster, but in this embodiment, the negative pressure of the first chamber 34 is introduced into the pressure introducing passage 50 for slip control. The state and the state where atmospheric pressure is introduced are switched. That is, the first chamber 34 and the pressure introducing passage 5
0 is connected via a pipe 37, and a three-way electromagnetic switching valve 38 (see FIG. 1) is connected to the pipe 37. The switching valve 38 communicates the pressure introducing passage 50 with the first chamber 34 during demagnetization, and introduces atmospheric pressure into the pressure introducing passage 50 during excitation. When the switching valve 38 is excited and atmospheric pressure is introduced into the pressure introducing passage 50, the space X, and thus the second chamber 35.
Becomes atmospheric pressure even when the brake pedal 12 is not depressed, and as a result, a boosting action is performed to generate a brake hydraulic pressure in the master cylinder 8.

FIG. 3 shows a control system in a simplified manner. In the figure, U is a control unit constructed by using a microcomputer.
The signals from the sensors or switches S1 to S7 are input. The sensors S1 to S4 detect the rotation speeds of the wheels 1FL to 1RR. The switch S5 is an accelerator switch that is turned on when the accelerator pedal 10 is fully closed. Switches S6 and S7 are not
It is operated when the key pedal 12 is depressed, for example, one switch is a normally open type and the other is a normally closed type. Further, although output from the control unit U to each device shown in FIG. 3, reference numeral 9 is a torque adjusting means for adjusting the torque generated by the engine 2. The torque adjusting means 9 adjusts the intake air amount,
Alternatively, the generated torque is adjusted by the combination of the number of fuel cut cylinders and the ignition timing adjustment.

Next, the outline of the slip control will be explained. In the embodiment, the slip value of the driving wheels is set as "slip value = driving wheel speed-vehicle speed", and the vehicle speed is the average value of the left and right driven wheel speeds. Is used.

Engine Control First, engine control starts with the left and right front wheels 1FL, 1FR.
The larger slip value among the respective slip values of 1 is satisfied when a predetermined start condition described later is satisfied. The engine control controls the torque adjusting means 9 so that the actual slip value becomes the engine target value (first target value) STE.
It is performed by controlling the feedback. Engine control is stopped when the accelerator is fully closed.

Break control The break control is started when all of the following conditions are satisfied. The first start condition is that the engine is being controlled. The second start condition is that the vehicle speed is a predetermined first vehicle speed V.
It is 1 or less. The third start condition is that a predetermined delay time described below has elapsed.

Prior to the start of the brake control, a response delay is expected, and at the same time when the engine control is started, the switching valve 38 is started.
Is boosted, the booster 11 is put into a boosting action state, the hydraulic pressure adjusting valves 15L and 15R are in the relief position, and the opening / closing valves 16L and 16R are closed. When a predetermined delay time elapses after exciting the switching valve 38, the
Control is started.

For the brake control, the left and right drive wheels 1FL, 1F are used.
By independently controlling the feedback of the hydraulic pressure adjusting valves 15L and 15R so that the actual slip value becomes the brake target value (second target value) STB (> STE). Performed (duty control).

The break control is stopped when any one of the following conditions is satisfied. The first stop condition is when the engine control is stopped. The second stop condition is when the vehicle speed becomes a high vehicle speed equal to or higher than a predetermined second vehicle speed V2 (V2> V1). The third stop condition is that the brake pedal 12 is depressed and the switch S
6 or S7 is detected (when it is detected by the switches S6 and S7 that the brake pedal 12 is depressed, the start of the brake control is prohibited).

When the brake control is stopped, the switching valve 38 is operated as long as the engine control is performed, the hydraulic pressure adjusting valves 15L and 15R are in the relief position, and the opening / closing valve 1
6L and 16R are closed (the same state as the standby state until the start of the brake control). Then, the switching valve 38 is demagnetized when the engine control is stopped or when the brake pedal 12 is depressed.

The engine control or slip control start condition is set as follows. That is, basically, it is assumed that the state where the slip value of the left and right drive wheels 1FL, 1FR, whichever has the larger slip value, is equal to or higher than the predetermined start threshold value continues for a predetermined time or longer. In the embodiment, the predetermined time is an integrated value obtained by integrating the deviation between the actual slip value of the driving wheels and the start threshold value for a predetermined integration time. More specifically, in FIG.
The predetermined integration time is indicated by T2. This integration time T2
Among them, between t5 and t6 and between t7 and t8, the actual slip value is larger than the start threshold value and the integral value becomes large. In addition, since the actual slip value is smaller than the start threshold value between t6 and t7, the integral value is reduced. Note that the integration may be performed such that the integrated value between t6 and t7 is 0.

The engine control, that is, the slip control is started when the integrated value becomes equal to or more than a predetermined reference integrated value. The reference integrated value is increased as the degree of unevenness on the road surface increases. That is, the greater the degree of unevenness on the road surface, the more difficult it becomes to start slip control.

The bad road degree, which indicates the degree of unevenness of the road surface, is set based on, for example, the acceleration / deceleration of the drive wheel speed. That is, as shown in FIG. 4, the number of times when the acceleration becomes equal to or higher than the predetermined acceleration AC and the predetermined deceleration D during the predetermined time T1.
The larger the total number of times when it becomes C or less and the total number of times (total number of times is 5 in FIG. 3), the greater the degree of bad road. Then, the degree of rough road is set to, for example, five levels,
The greater the degree of rough road (the greater the total number above),
The reference integrated value is increased.

Next, a control example of the present invention will be described with reference to the flow chart of FIG. 6. In the following description, P represents a step. First, after signals from the respective sensors are input at P1, it is determined at P2 whether the flag is 1 or not. When this flag is 1, the slip control is being performed, and since this flag has been initialized to 0, the determination in P2 is initially NO and the routine moves to P3.

At P3, the rough road degree AN is set by the method described in the figure, and then at P4, the reference integrated value IO corresponding to this rough road degree AN is set. P5
Then, the actual integrated value IA is calculated as described with reference to FIG. In addition, the count of the number of times when a predetermined acceleration or deceleration for setting the rough road degree in P3 is exceeded, P5
The actual calculation of the integrated value in
This is performed by interrupt processing for the chart.

At P6, it is judged if the actual integrated value IA is greater than or equal to the reference integrated value IO. When the determination in P6 is NO, the slip control start condition is not satisfied, and therefore the routine is returned as it is. YE in the judgment of P6
In the case of S, the flag is set to 1 in P7, and then the slip control is started in P8 (as described above, the slip control may be performed only by the engine control).

At P9, it is judged if the accelerator is fully closed. If the judgment at P9 is NO, the judgment at P2 becomes YES and the slip control at P8 is continued. If YES in the determination in P9, the flag is reset to 0 in P10, and then the slip control is stopped in P11.

Although the embodiments have been described above, the present invention is not limited to this, and includes, for example, the following cases. The slip value of the driving wheel is, for example, “driving wheel speed /
Vehicle speed "or" (driving wheel speed-vehicle speed) / vehicle speed)]. The slip control may be engine control only or brake control only. A pump for generating a brake fluid pressure may be separately used as is generally done without using the star 11. To determine the degree of rough road, for example, see suspension stroke. Therefore, or by observing the vertical acceleration acting on the vehicle body, various conventionally proposed methods can be adopted.

In order to make it more difficult to start the slip control as the degree of unevenness of the road surface increases, the following can be performed, for example. First, the integration time T2 shown in FIG. 5 may be shortened as the degree of unevenness of the road surface increases.
Further, the start threshold value in FIG. 5 may be increased as the degree of unevenness on the road surface increases. In these cases, the reference integral value can be set as a certain constant value. Of course, it is also possible to appropriately combine a plurality of changes of the reference integration value, the integration time T2, and the start threshold value shown in the embodiment. Instead of performing the integration shown in FIG. 5, the slip control may be started only when the state in which the start threshold value is exceeded continues for a predetermined time or longer. In this case, the degree of unevenness of the road surface is reduced. At least one of increasing the predetermined time and increasing the starting threshold value may be performed.

[Brief description of drawings]

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

FIG. 2 is an enlarged cross-sectional view of a main part of a brake booster.

FIG. 3 is a diagram showing a control system of the present invention.

FIG. 4 is a diagram showing an example of determining the degree of rough road.

FIG. 5 is a diagram showing how to obtain an integral value.

FIG. 6 is a flow chart showing a control example of the present invention.

[Explanation of symbols]

 1FR, 1FL: Drive wheel 1RR, 1RL: Driven wheel 2: Engine 9: Generated torque adjusting means 7FR to 7FL: Break 11: Break booster 15R, 15L: Break hydraulic pressure adjusting means U: Control unit S1 to S4: Wheel speed sensor

Claims (6)

[Claims] 1. A vehicle slip control device for preventing an excessive slip value of a drive wheel from a road surface by reducing a torque applied to the drive wheel, when a predetermined start condition is satisfied. Starting means for starting the slip control for reducing the torque applied to the drive wheels, a bad road degree detecting means for detecting a bad road degree indicating the degree of unevenness of the road surface, and a road surface detected by the bad road degree detecting means. A slip control device for a vehicle, comprising: a start condition changing unit that changes the start condition so that slip control is less likely to be started when the degree of unevenness is smaller than when the degree of unevenness is small. 2. The slip detection means for detecting a slip value of a drive wheel with respect to a road surface according to claim 1, wherein the disclosure condition is that the actual slip value of the drive wheel detected by the slip detection means starts to a predetermined start. It is set when the state of being equal to or more than the threshold value continues for a predetermined time or more, and the start condition changing means increases the predetermined time when the degree of unevenness of the road surface is large compared to when it is small. 3. The slip detection means for detecting a slip value of a drive wheel with respect to a road surface according to claim 1, wherein the disclosure condition is that the actual slip value of the drive wheel detected by the slip detection means starts to a predetermined start. It is set when the state of being equal to or more than the threshold value continues for a predetermined time or more, and the start condition changing means increases the start threshold value when the degree of unevenness of the road surface is large compared to when it is small. 4. A slip detecting means for detecting a slip value of a drive wheel with respect to a road surface according to claim 1, wherein a deviation between an actual slip value of the drive wheel and a predetermined start threshold value is integrated for a predetermined integration time. The starting condition changing means sets a reference integral value that becomes larger as the degree of unevenness of the road surface detected by the rough road degree detecting means is larger, and the starting condition is It is set when the integrated value integrated by the integrating means is equal to or more than the reference integrated value. 5. The slip detection means for detecting a slip value of a drive wheel relative to a road surface according to claim 1, wherein a deviation between an actual slip value of the drive wheel and a predetermined start threshold value is integrated for a predetermined integration time. The starting condition changing means sets the predetermined integration time to be shorter as the degree of unevenness of the road surface detected by the rough road degree detecting means is set to be shorter, and the starting condition is the integration. It is set when the integrated value integrated by the means becomes equal to or larger than a preset reference integrated value. 6. The integration device according to claim 1, further comprising integration means for integrating a deviation between an actual slip value of a driving wheel and the start threshold value for a predetermined integration time, wherein the start condition changing means comprises the rough road degree. The larger the degree of unevenness of the road surface detected by the detection means, the larger the start threshold value is set, and the start means sets the integrated value integrated by the integrating means to a predetermined reference integrated value or more. What is sometimes set.