JPH1016745A - Wheel slip control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To securely start on a low μ uphill slope by providing a braking control means for allowing a vehicle backward movement within a range that it does not exceed an upper limit value previously set speed of backward movement when the driving back of the vehicle is detected when driver's intention of forward movement operation is detected. SOLUTION: In a wheel slip control device, when backward movement of a vehicle is detected by a backward movement detecting means when driver's intention of frontward movement operation is detected by a frontward operation detecting means, backward movement of the vehicle is allowed within a range that backward speed by a speed detecting means does not exceed an upper limit value previously set. Whereby, braking of the vehicle is controlled so as to move backward smoothly when the vehicle fails to start on as low μuphill slope and when the vehicle fails to drive approaching the low μ uphill slope while traveling. Thereby, when the vehicle approaches a part relatively high road friction coefficient while moving backward, frontward speed is caused by appropriate drive force by the wheel slip control device and the vehicle can securely go up hill.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wheel slip control device, and more particularly, to a wheel slip control device which suppresses a wheel slip generated at the time of starting or running on a low .mu.

[0002]

2. Description of the Related Art Conventionally, there has been known a wheel slip control device which detects a slip state of a driving wheel and controls a driving force of the driving wheel so as to make a desired slip state. With such a wheel slip control device, the occurrence of wheel slip can be prevented, and the stability during traveling on a road surface (low μ road) having a particularly low friction coefficient can be improved. However,
When a vehicle is started on an ascending road having a low friction coefficient, such as a snowy road, it may be difficult to start the vehicle properly with the conventional wheel slip control.

The reasons for this are as follows. First, in the conventional wheel slip control device, failure to start on a low μ uphill road,
That is, it was impossible to detect the backward movement of the vehicle due to the stall while traveling on the low μ uphill road. This is because the conventional wheel speed sensor does not know the direction of rotation of the wheels, and cannot detect the slippage of the drive wheels, but cannot determine the backward movement of the vehicle.

Another reason is that in the conventional wheel slip control device, when a drive wheel slip occurs when starting on a low μ uphill road, control is performed to suppress the drive wheel slip itself. Sometimes, it did not provide the necessary driving force. Therefore, since the slip is suppressed, the driving force is suppressed below the necessary driving force at that time. Sometimes, I could not start. Therefore, there is a case where the starting ability is higher when the wheel slip control is not performed.

On the other hand, in the wheel slip control device disclosed in Japanese Patent Application Laid-Open No. Hei 7-125622, each wheel is provided with a sensor capable of detecting the rotational direction of the wheel, and the rotational directions of the driven wheel and the driven wheel are different. In such a case, the reverse of the vehicle is detected. Then, when the vehicle is detected to retreat at the time of starting on a low μ uphill road, the vehicle is temporarily stopped.

[0006]

However, the above-mentioned publication has a function as an emergency avoidance when starting on a low μ uphill road fails, but does not have a function to assist starting. Was. Therefore, when the vehicle retreats on a low μ uphill road, there is a problem that it is not always possible to restart from the stop position even if the vehicle is once stopped.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a wheel slip control device capable of surely starting on a low μ uphill road.

[0008]

As shown in FIG. 1, the present invention provides a wheel slip control device for detecting the slip state of a drive wheel and controlling the driving force of the drive wheel so as to obtain a desired slip state. A forward operation detecting means for detecting a driver's intention to move forward, a reverse detecting means for detecting backward movement of the vehicle, a vehicle speed detecting means for detecting a speed of the vehicle, and when a driver's intention to move forward is detected And a braking control means for allowing the vehicle to retreat within a range where the reversing speed does not exceed a preset upper limit value when the vehicle retreat is detected. Is solved.

[0009] According to the present invention, even when the driver is performing a forward operation, such as when the vehicle fails to start on a low μ climbing road or when the vehicle approaches the low μ climbing road and stalls while traveling. When the backward movement of the vehicle is detected, the braking control is performed so that the vehicle slowly moves backward within a range where the backward speed does not exceed a preset upper limit value. Accordingly, when the vehicle approaches a portion having a relatively high road surface friction coefficient during the retreat, a forward speed is generated by an appropriate driving force by the wheel slip control device, and a reliable uphill can be performed.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 2 is a schematic configuration diagram of a vehicle equipped with a wheel slip control device according to an embodiment of the present invention. In the present embodiment, a rear-wheel drive vehicle is taken as an example.

In FIG. 2, a front left wheel 10 and a front right wheel 12 are shown.
Are driven wheels, and the left rear wheel 14 and the right rear wheel 16 are drive wheels. The driving force of the engine 18 is the propeller shaft 20
a, each rear wheel 1 via a differential gear 20b, etc.
4 and 16 are transmitted. Further, a transmission (not shown) is connected to the engine 18, and an electronic control unit (ECU) 22 knows in which gear the gear is set in this transmission. Accordingly, the fact that the gear is engaged in the forward gear is detected by the electronic control unit 22 (forward operation detecting means).

The wheels 10 to 16 are provided with brakes 24 to 30, respectively. Each brake 24-30
Have brake pipes 24a-30 connected to an ABS (anti-skid brake system) actuator 32
a is connected. The ABS actuator 32 receives signals from the electronic control unit 22 to control the brakes 24 to 3
The brake hydraulic pressure supplied to 0 is controlled, thereby controlling the braking force of each of the brakes 24 to 30.

The ABS actuator 32 has a TRC
(Traction control) The TRC actuator 34 is connected to an actuator 34 (braking control means) and supplies a brake oil pressure to the ABS actuator 32 according to a signal from the electronic control unit 22. At this time, a signal is also supplied from the electronic control unit 22 to the TRC pump 36, and the TRC pump 36 operates a pump motor (not shown) to change the brake fluid to the TRC actuator 34.
To generate TRC control hydraulic pressure.

The brake pedal 38 is a brake booster 4
0 is connected to the master cylinder 42 through the brake cylinder 38, and the pedaling force generated when the driver depresses the brake pedal 38 is amplified by the brake booster 40 and the master cylinder 4
In step 2, it is converted to brake hydraulic pressure. A reservoir tank 44 in which brake fluid is stored is provided above the master cylinder 42. The TRC pump 3
6 operates, the brake fluid stored in the reservoir tank 44 is pressure-fed to the TRC actuator 34, and a TRC control hydraulic pressure is generated.

Further, a brake switch 46 is provided on the brake pedal 38.

Each of the wheels 10 to 16 has a
Wheel speed sensors 48 to 54 for detecting 16 wheel speeds are provided. The wheel speeds of the wheels 10 to 16 are individually detected by the wheel speed sensors 48 to 54.
The detected wheel speed is transmitted to the electronic control unit 22, and the electronic control unit 22 (vehicle speed detecting means) calculates the vehicle speed and the drive wheel slip ratio.

The engine 18 draws in intake air from an intake passage 56 and a surge tank 58 and is supplied with fuel from a fuel injection valve 60. The intake passage 56 is provided with a main throttle valve 62 for controlling the amount of intake air. ing. The main throttle valve 62 is connected to an accelerator pedal 64 and rotates in response to depression of the accelerator pedal 64.

The fuel injection valve 60 has a valve opening timing and a valve opening time controlled by a control signal from the electronic control unit 22.
An amount of fuel corresponding to the valve opening time is injected and supplied to the engine 18. The fuel injection amount control by the electronic control unit 22
Basically, the adjustment is performed in accordance with the intake air amount or the intake air amount per process determined by the intake pipe pressure and the engine speed.

The main throttle valve 6 in the intake passage 56
2, a sub-throttle valve 66 is provided on the upstream side when viewed from the intake flow. The sub throttle valve 66 is
The motor is opened and closed by a step motor (not shown), and the step motor controls the opening of the sub-throttle valve 66 in accordance with a control signal from the electronic control unit 22 that performs wheel slip control.

Information on the opening of the main throttle valve 62 is taken into the electronic control unit 22 by the main throttle idle switch 68.

The electronic control unit 22 also includes a G sensor 7
0 and the signal from the ground speed sensor 72 are fetched. The G sensor 70 detects the inclination of the vehicle body, thereby detecting that the road surface is a slope. The ground speed sensor 72 (reverse detection means) transmits ultrasonic waves toward the road surface behind the vehicle, receives reflected waves from the road surface, and determines the traveling direction of the vehicle based on the principle of the Doppler effect. That is, if the frequency of the received wave is higher than the frequency of the transmitted wave, the vehicle is moving backward.

The operation of this embodiment will be described below.

FIG. 3 is a flowchart showing the control in this embodiment.

In step 100 of FIG. 3, conditions for starting the control of this embodiment are determined. The control is started when all of the following five conditions are satisfied.

(1) The slip ratio of the drive wheels is greater than or equal to a threshold value. (2) The gear of the transmission is in the forward gear. (3) The detected value of the G sensor is greater than or equal to the threshold value. Brake switch off

The control start condition is for predicting a failure to start on a slope or a stall during traveling on a slope. When the above condition is satisfied, the following control is performed until the failure of the driver is detected and the operation returns to the normal operation again.

The slip ratio of the drive wheels is calculated by the electronic control unit 22 based on the wheel speeds obtained by the wheel speed sensors 48 to 54. The fact that the slip ratio of the drive wheels is equal to or greater than the threshold value indicates that the road surface is a low μ road. The fact that the detection value of the G sensor 70 is equal to or greater than the threshold value indicates that the road surface is an uphill road. Turning off the main throttle idle switch 68 means turning on the accelerator. Therefore, the fact that the gear is in the forward gear, the brake is not depressed, and the accelerator is depressed means that the driver is driving the vehicle with an intention to move forward.

Therefore, the satisfaction of all the above five conditions means that the driver is performing the forward operation on the low μ climbing road, and there is a possibility that the start of the slope may fail or the vehicle may stall.

If the control start condition in step 100 is satisfied, that is, if all of the above conditions (1) to (5) are satisfied, control C is performed in the next step 110.

The control C includes the following three contents.

First, the valve opening characteristics of the electronic throttle are shown in FIG.
As shown in (1), the “resolution” is changed so as to increase. That is, as shown in FIG. 4, the region where the engine torque is low can be adjusted with a wider accelerator pedal stroke. As a result, the delicate operation of the accelerator pedal 64 according to the vehicle behavior becomes possible.

Second, the control LSD is set to 100% (or the interlock differential lock is fixed). As a result, the left and right rear wheels (drive wheels) 14 and 16 are directly connected and driven integrally, so that a greater driving force can be obtained.

Third, the load on the right and left rear wheels (drive wheels) 14 and 16 is increased by adjusting the vehicle height by height control.

If the control start condition is not satisfied in step 100, the control immediately returns without performing the control.

Next, in step 120, a condition for entering the control A is determined. Control A is to prevent the vehicle from stalling.

When all of the following six conditions are satisfied,
It is assumed that the control A start condition is satisfied.

(1) The rate of increase of the main throttle opening is 0
(2) Transmission gear is in forward gear (3) Brake switch is off (4) Vehicle acceleration is below threshold (5) Vehicle speed is 0 or above (6) Drive wheel slip ratio is above threshold

When the rate of increase of the main throttle opening is 0 or more, it means that the main throttle valve 62 is being kept constant or open, that is, the driver is depressing the accelerator pedal 64.

The vehicle acceleration and the vehicle speed are calculated by the electronic control unit 22 based on signals from the wheel speed sensors 48 and 50 of the left and right front wheels (driven wheels) 10 and 12. If the vehicle speed is 0 or more, it means that the vehicle is not moving backward.

When all of the above six conditions are satisfied,
In the next step 130, control A is executed.

The control A in step 130 changes the slip ratio control of the left and right rear wheels (drive wheels) 14 and 16 to traction emphasis. That is, the slip ratio of the left and right rear wheels (drive wheels) 14 and 16 is set to (driven wheels) 10 and 12.
Is controlled to be higher by 10 to 20% than the slip ratio of. This control includes wheel slip control by braking force control for controlling the braking force of the brakes 28 and 30 of the left and right rear wheels (drive wheels) 14 and 16 by the TRC actuator 34 and the opening and closing of the sub-throttle valve 66 to a predetermined opening. This is performed by using one or both of wheel slip control by engine output control for controlling the driving force of the left and right rear wheels (drive wheels) 14 and 16 by controlling the output of the engine 18.

In the next step 140, a condition for terminating the control is determined.

If the condition for starting the control A is not satisfied in step 120, the process proceeds to step 150, where the control B is performed.

The control B allows a slow retreat of the vehicle within a range where the retreat speed of the vehicle does not exceed a preset upper limit value when the vehicle retreats unintentionally by the driver. A portion having a high coefficient of friction is obtained to recover the climbing force.

The contents of the control B are shown in the flowchart of FIG.

In step 200 of FIG. 5, a condition for starting control B is determined.

Control B is started when all of the following five conditions are satisfied.

(1) The value detected by the ground speed sensor is negative (2) The driven wheel speed is positive (3) The transmission gear is in the forward gear (4) The main throttle idle switch is off (5) Brake Switch off

When the ground speed sensor is negative and the driven wheel speed is positive, it means that the vehicle is moving backward at a certain speed. Also, the fact that the transmission gear is in the forward gear, the main throttle idle switch is off and the brake switch is off means that the driver puts the gear in the forward gear and depresses the accelerator, and performs the forward operation with the intention of forward. Means you are. Therefore, if all of the above five conditions are satisfied, it means that the vehicle is moving backward against the driver's intention to move forward.

If the above condition is not satisfied, control B
Exits this routine without performing.

When the control B start condition is satisfied,
In the next step 210, control is performed to change the slip ratio of the left and right rear wheels (drive wheels) 14, 16 to traction as in step 130 of FIG.

In the next step 220, the wheel cylinder oil pressure of the brakes 24, 26 of the left and right front wheels (driven wheels) 10, 12 is increased. This pressure increase is performed by increasing the pulses in the duty control. As a result, a braking force is applied to the left and right front wheels (driven wheels) 10 and 12, and the retreat speed of the vehicle is suppressed.

In the next step 230, the driven wheel speed is greater than a predetermined value a (a preset upper limit value).
And it is determined whether or not the detection value of the ground speed sensor 72 is negative.

As a result, when this condition is satisfied,
The left and right rear wheels (drive wheels) 14 and 16 are rotating in the forward direction, but slip and the vehicle retreats at a speed exceeding a preset upper limit, and the left and right front wheels (driven wheels) 10 and 12 are in opposite directions. Is rotating. At this time, in the next step 240, the pulse interval of the duty control is narrowed to increase the number of pulses, and the process returns to step 200.

If the condition in step 230 is not satisfied, the routine proceeds to the next step 250, in which it is determined whether the driven wheel speed is 0 and the value detected by the ground speed sensor 72 is negative.

As a result, when this condition is satisfied,
The vehicle is still retreating and the left and right front wheels (driven wheels) 10,
12 is too braking and does not rotate. Then, the process proceeds to step 260, in order to reduce the wheel cylinder oil pressure of the left and right front wheels (driven wheels) 10, 12, the pulse interval of the duty control is widened and the number of pulses is reduced.
Return to 00.

If the condition in step 250 is not satisfied, in step 270 the driven wheel speed is between 0 and the predetermined value a and the ground speed sensor 72
It is determined whether the detection value of is negative.

When this condition is satisfied, the vehicle is moving gently backward as long as the speed of retreat does not exceed the preset upper limit. Therefore, the process returns to step 200, and the above control is repeated. In the meantime, a portion having a slightly high road surface friction coefficient is captured to obtain a forward speed.

If the condition in step 270 is not satisfied, the process proceeds to step 280, where an erroneous detection process such as issuing a warning to the driver is performed.

After executing the above control B, the process proceeds to step 140 in FIG. 3, and a control end condition is determined.

The end of the control is determined based on whether or not the detected value of the ground speed sensor 72 is positive and the driven wheel speed is equal to or higher than a predetermined value.

If the value detected by the ground speed sensor 72 is positive, it means that the vehicle is moving forward. At this time, if the driven wheel speed is equal to or higher than a predetermined value, it is assumed that the vehicle is surely climbing a slope at a stable speed. Is determined.

If this condition is not satisfied and the control has not been completed yet, the routine returns to step 120, where control A or control B is executed according to the situation.

When it is determined that the control has been completed, the routine proceeds to the next step 170, where the control is terminated. This control termination processing corresponds to control C in step 110. That is, the valve opening characteristic of the electronic throttle is restored, the lock ratio of the control LSD is restored (or the interlocking differential lock is released), and the height control is released to return to the state before the control was started. It is.

As described above, according to the present embodiment, when the vehicle is unintentionally moved backward, the vehicle is slowly moved backward. When approaching a portion with a high friction coefficient, it becomes possible to generate a forward speed by an appropriate driving force by the wheel slip control.

In this embodiment, the present invention is applied to a rear-wheel drive vehicle. However, the present invention is not limited to this, and is applicable to a front-wheel drive vehicle. obtain.

[0068]

As described above, according to the present invention,
Even when the vehicle fails to start on a low μ uphill road, or when the vehicle stalls during running, etc., the vehicle is gently moved backward to obtain the driving force from the relatively high coefficient of road surface friction, and the vehicle is reliably advanced. It became possible.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the gist of the present invention.

FIG. 2 is a schematic configuration diagram of a vehicle equipped with a wheel slip control device according to an embodiment of the present invention.

FIG. 3 is a flowchart illustrating control according to the embodiment;

FIG. 4 is a diagram showing a relationship between an accelerator pedal stroke and an engine torque.

FIG. 5 is a flowchart showing control for retreating the vehicle unintentionally by the driver according to the embodiment;

[Explanation of symbols]

10, 12 ... left and right front wheels (driven wheels) 14, 16 ... left and right rear wheels (driving wheels) 18 ... engine 22 ... electronic control unit (forward operation detecting means, vehicle speed detecting means) 24-30 ... brake 32 ... ABS actuator 34 ... TRC actuator (braking control means) 36 ... TRC pump 38 ... Brake pedal 40 ... Brake booster 42 ... Master cylinder 44 ... Reservoir tank 46 ... Brake switch 48-54 ... Wheel speed sensor 62 ... Main throttle valve 64 ... Accelerator pedal 66 ... Sub throttle valve 68 Main throttle idle switch 70 G sensor 72 Ground speed sensor (reverse detection means)

Claims (1)

[Claims] 1. A wheel slip control device for detecting a slip state of a driving wheel and controlling a driving force of the driving wheel so as to make a desired slip state, forward operation detecting means for detecting a driver's intention to perform a forward operation, and a vehicle. Reverse detection means for detecting the reverse of the vehicle, vehicle speed detecting means for detecting the speed of the vehicle, and the speed of the reverse when the driver's intention to move forward is detected and when the vehicle is detected to reverse. And a braking control means for allowing the vehicle to retreat within a range not exceeding a preset upper limit value.