JPH05106476A - Slip control device for vehicle - Google Patents

Abstract

PURPOSE:To prevent the degradation of driving force so as to improve drivability, by restricting the reductive correction at a speed higher than a specified car speed, in a controller controlling driving force depending upon slip ratio of drive wheels and correcting a control target value of driving force reductively depending upon transversal acceleration of the vehicle. CONSTITUTION:When a slip ratio of drive wheels to a road face exceeds a specified value, the driving force of the drive wheels is controlled with a drive wheel control means A so as to bring the slip ratio close to the specified slip ratio. The control of the driving force is carried out by restriction of engine output, application of braking force to drive wheels, or use of both functions of the engine and wheels together. And the control target value or threshold values of a control range of the driving force control means A are controlled reductively with a correction means B depending upon the increment of transversal acceleration of the vehicle. In such a slip control device, in a car speed region higher than a specified car speed, the reductive correction with a correction means B is restricted by a correction restricting means C to eliminate stall feeling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slip control device for a vehicle, and more particularly to a slip control device for controlling a driving force of a drive wheel when a slip ratio of the drive wheel with respect to a road surface exceeds a predetermined value.

[0002]

2. Description of the Related Art When a vehicle is accelerated, the driving wheels may slip due to an excessive driving force, which may deteriorate the acceleration performance. Therefore, conventionally, when the slip ratio of the drive wheel with respect to the road surface becomes equal to or greater than a predetermined value, a slip control device that performs so-called traction control that controls the driving force of the drive wheel so that the slip ratio approaches a predetermined target slip ratio. Is proposed.

Further, when the vehicle is turning, slippage is more likely to occur in the drive wheels than when it is straight ahead. Therefore, Japanese Patent Application Laid-Open No. 1-130019 detects that the vehicle is turning due to the lateral acceleration of the vehicle. However, a slip control device has been proposed in which the occurrence of a large slip is prevented in advance by correcting the control start threshold value in the traction control so as to decrease according to the increase in the lateral acceleration.

[0004]

However, the above-mentioned conventional slip control device has the following problems. That is, since the lateral acceleration of the vehicle increases in proportion to the square of the vehicle speed, when the vehicle speed increases, the lateral acceleration becomes a very large value even if the steering angle is small. For this reason,
Actually, even at a small steering angle where there is almost no risk of a large slip, the control start threshold in traction control is corrected to be reduced more than necessary, and as a result the driving force is reduced. It will give a feeling. Such a problem also occurs when the target control value is reduced and corrected instead of the control start threshold value.

The present invention has been made in view of the above circumstances, and provides a vehicle slip control device capable of performing appropriate traction control while preventing a reduction in driving force due to unnecessary reduction correction. It is intended to be provided.

[0006]

A vehicle slip control device according to the present invention limits the reduction correction of a control target value or a control start threshold value in traction control in a vehicle speed range equal to or higher than a predetermined set vehicle speed. It is designed to achieve the purpose.

That is, as described in claim 1 and as shown in FIG. 1, when the slip ratio of the drive wheels with respect to the road surface exceeds a predetermined value, the slip ratio is brought close to a predetermined target slip ratio. Drive force control means (A) for controlling the drive force of the drive wheels, and a correction for correcting the control target value or the control start threshold value of the drive force control means (A) in accordance with the increase of the lateral acceleration of the vehicle. In a vehicle slip control device including means (B), correction limiting means (C) for limiting the reduction correction by the correction means (B) is provided in a vehicle speed region equal to or higher than a predetermined set vehicle speed. It is what

The above-mentioned "driving force control means" is not limited to a specific control means. For example, by limiting the engine output (claim 4) or by applying a braking force to the driving wheels. (Claim 5), and further by both of them (Claim 6), the driving force can be controlled.

The specific configuration for "limiting the reduction correction" of the "correction limiting means" is not particularly limited, but for example, the configuration for canceling the reduction correction, the reduction correction according to the increase in the vehicle speed. A structure for reducing the amount, a structure for permitting the correction correction by the correction means only when the lateral acceleration of the vehicle is a predetermined value or less (claim 2), a decrease by the correction means only when the steering angle of the vehicle is a predetermined value or more It is possible to adopt a configuration that allows correction (claim 3), or a combination thereof.

[0010]

As described above, according to the first aspect of the present invention, the control target value or the control start threshold value of the driving force control means is adjusted by the correction means in accordance with the increase of the lateral acceleration of the vehicle. Since it is designed to be reduced,
It is possible to prevent a large slip from occurring when the vehicle is turning, and this reduction correction is limited by the correction limiting means in the vehicle speed region above the predetermined set vehicle speed. Therefore, it is possible to prevent the correction from being reduced more than necessary at the time of a small steering angle where there is almost no possibility of slippage.

Therefore, according to the present invention, it is possible to prevent the reduction of the driving force due to unnecessary reduction correction and to perform the appropriate traction control, thereby preventing the driver from feeling stall. You can

[0012]

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

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

As shown in FIG. 2, in a vehicle provided with this slip control device, the left and right front wheels 1 and 2 are driven wheels, and the left and right rear wheels 3 and 4 are drive wheels. From transmission 6 to propeller shaft 7 and differential 8
And the left and right rear wheels 3, 4 via the left and right drive wheels 9, 10.
To be transmitted to.

The wheels 1 to 4 are provided with disks 11a to 14a which rotate integrally with the wheels 1 to 4, respectively.
In response to the supply of the braking pressure, these disks 11a-14
and brake devices 11 to 14 including calipers 11b to 14b for braking the rotation of a, respectively.
Further, a brake control system 15 is provided for performing a braking operation on these brake devices 11-14.

The brake control system 15 includes a booster device 17 for increasing the depression force of a brake pedal 16 by a driver and a master cylinder 18 for generating a braking pressure according to the depression force increased by the booster device 17. And have. The front wheel braking pressure supply lines 19 and 20 guided from the master cylinder 18 are the calipers 11b and 12 of the brake devices 11 and 12 on the left and right front wheels 1 and 2.
b respectively. Then, the braking pressure corresponding to the depression force of the brake pedal 16 generated in the master cylinder 18 is applied to the braking devices 11, 1 on the left and right front wheels 1, 2 via the braking pressure supply lines 19, 20 for the front wheels.
The front wheels 1 and 2 are respectively braked by the braking force corresponding to these braking pressures.

The booster 17 is connected to a working pressure supply line 22 for supplying a working pressure from a pump 21 and a return line 23 for returning excess brake oil generated in the booster 17 to a reservoir tank. And a first braking pressure supply line 24 led from the booster 17,
Electromagnetic first and second on-off valves 26 and 27 are respectively installed in the second braking pressure supply line 25 branched from the pump discharge side of the operating pressure supply line 22. A check valve 28 for preventing backflow is installed in the first braking pressure supply line 24 in parallel with the first opening / closing valve 26. Also,
The first and second braking pressure supply lines 24 and 25 are joined at a point X, and the braking pressure for the rear wheels is applied to the calipers 13b and 14b of the braking devices 13 and 14 on the left and right rear wheels 3 and 4 from the joining point X. Supply lines 29, 30 are led. Electromagnetic on-off valves 31, 32 and relief valves 33, 34 are installed on the braking pressure supply lines 29, 30, respectively.

On the other hand, in the intake passage 35 of the engine 5, a main throttle valve 37 connected to an accelerator pedal 36 operated by a driver and a sub-throttle valve 39 connected to a throttle opening adjusting actuator 38 are installed. The intake air amount of the engine 5 is variably controlled and the engine output is adjusted by adjusting the opening amounts of the throttle valves 37 and 39.

The slip control device comprises an electronically controlled control unit (hereinafter referred to as "ECU") 40, and the ECU 40 is adapted to perform traction control. In the traction control, when the slip ratios of the rear wheels 3 and 4 which are the driving wheels with respect to the road surface become equal to or more than a predetermined value, the driving force of each of the rear wheels 3 and 4 is set so that the slip ratio approaches a predetermined target slip ratio. Specifically, the control of the driving force is performed by limiting the engine output (engine control) and applying a braking force to the rear wheels 3 and 4 (brake control). It has become.

The ECU 40 receives signals from wheel speed sensors 41 to 44 for detecting the rotational speeds of the wheels 1 to 4,
A signal from an engine speed sensor 45 that detects the engine speed and a brake pressure supply line 29 for the rear wheel that communicates with the brake device 13 for the left rear wheel 3 are installed on the downstream side of the on-off valve 31 and installed in the brake device 13. The first pressure sensor 46 for detecting the supplied braking pressure and the brake device 14 installed downstream of the on-off valve 32 in the rear wheel braking pressure supply line 30 communicating with the brake device 14 for the right rear wheel 4 are supplied. The second pressure sensor 47 that detects the braking pressure, the signal from the accelerator position sensor 48 that detects the depression amount of the accelerator pedal 36, and the signal from the steering angle sensor 49 that detects the steering steering angle are input. Based on these signals, the ECU 40 opens and closes the opening / closing valves 26, 27, and 27 in the brake control system 15.
The operation of the valves 31, 32 and the relief valves 33, 34 and the operation of the throttle opening adjustment actuator 38 for adjusting the opening of the sub-throttle valve 29 are controlled.

The control signal from the ECU 40 causes the first opening / closing valve 26 on the first braking pressure supply line 24 to open and the second opening / closing valve 27 on the second braking pressure supply line 25 to close, as shown in the figure. Further, when the on-off valves 31, 32 on the rear wheel braking pressure supply lines 29, 30 are opened, the braking pressure according to the stepping force of the brake pedal 16 generated by the booster 17 becomes the first pressure. It is supplied to the brake devices 13 and 14 on the left and right rear wheels 3 and 4 via the braking pressure supply line 24,
The rear wheels 3 and 4 are respectively braked by the braking force according to these braking pressures. On the other hand, when performing traction control by brake control, the ECU 40 closes the first opening / closing valve 26 and opens the second opening / closing valve 27. Therefore, the operating pressure generated by the pump 21 does not pass through the booster 17 and is used as a braking force as the rear wheel braking pressure supply line 2.
9 and 30 are supplied.

Then, for example, when the spin state of the left rear wheel 3 is detected from the signals from the wheel speed sensors 41 to 44, that is, the average front wheel speed V obtained by averaging the rotational speeds of the front wheels 1 and 2 which are driven wheels. When it is detected that the rotational speed of the rear wheel 3 which is a driving wheel is high with _F as a reference, the on-off valve 31 and the relief valve 33 on the one rear wheel braking pressure supply line 29 are opened and closed by duty control, A braking force is applied to the rear wheel 3 with a braking pressure according to the slip state. When the spin state of the right rear wheel 4 is detected, the opening / closing valve 32 and the relief valve 34 on the other rear wheel braking pressure supply line 30 are opened / closed by duty control to perform braking according to the slip state. The braking force is applied to the rear wheel 4 by the pressure. That is, in this embodiment, the braking force applied to the left and right rear wheels 3 and 4 is independently controlled.

The ECU 40 is also adapted to perform a friction coefficient estimation process necessary for determining a control target value and a control start threshold value in traction control.

An outline of the friction coefficient estimation process will be described. For example, the left rear wheel 3 is performed as follows. That is, the ECU 40 uses the wheel speed sensor 41,
The average front wheel speed V _F obtained from the rotational speeds of the left and right front wheels 1 and 2 indicated by the signal from the reference numeral 42 is a predetermined lower limit value V _O (for example, 5 k
m / h), and when the average front wheel speed V _F is equal to or higher than the lower limit value V _O , the road surface friction coefficient μ _L is determined by the average front wheel speed V _F and the front wheel acceleration _AF obtained from the average front wheel speed V _F.
To estimate.

Here, the road surface friction coefficient μ is extremely low μ
Any one of the numerical values divided into 5 stages from 1 indicating a road to 5 indicating a high μ road is selected.

On the other hand, when the ECU 40 determines that the average front wheel speed V _F is smaller than the lower limit value V _O, the rear wheel acceleration A _RL obtained from the left rear wheel speed V _RL indicated by the signal from the sensor 43 is obtained. it is determined whether it exceeds a predetermined reference value a _O (eg 2G), when it is determined as exceeding the left rear wheel 3 in accordance with the engine speed N indicated by the signal from the engine speed sensor 45 Road friction coefficient for
It is designed to estimate _L. On the other hand, rear wheel acceleration A _RL
When it is determined that is smaller than the reference value A _O , a fixed value (for example, 3) is selected as the road surface friction coefficient μ _L.

The road surface friction coefficient μ _R is similarly estimated for the right rear wheel 4.

The traction control by the ECU 40 is independently performed for each of the left and right rear wheels 3, 4, and for example, the left rear wheel 3 is performed as follows.

That is, first, the ECU 40 uses the table in which the road surface friction coefficient μ _L is set as a parameter in advance, to determine the engine control start threshold S _EO , the engine control target value S _E , the brake control start threshold S _BO, and the brake control target. Read the value S _B and.

Table 1 shows the relationship between the road surface friction coefficient μ, the engine control start threshold value S _EO and the target value S _E , the brake control start threshold value S _BO and the target value S _B. .. In this embodiment, the engine control start threshold value S _EO is set to the same value as the engine control target value S _E , and the brake control start threshold value S _BO is set to the same value as the brake control target value S _B. Has been done.

[0031]

[Table 1]

In Table 1 above, each control start threshold value S _EO ,
S _BO and the respective control target values S _E and S _B are set as values corresponding to the slip ratio of the left rear wheel 3 with respect to the road surface.

The ECU 40 controls the left rear wheel speed V _RL and the wheel speed sensors 41, 4 indicated by the signal from the wheel speed sensor 43.
From the average front wheel speed V _F indicated by the signal from 2, the first slip ratio S ₁ for the left rear wheel 3 is calculated by the following equation (1).

S ₁ = (V _RL −V _F ) / V _RL (1) The ECU 40 determines when the first slip ratio S ₁ exceeds the engine control start threshold value S _EO as shown in FIG. (T
_The engine control is started in ₁ ) and the engine control target value S _E
Throttle opening adjustment actuator 3 so that
The sub throttle valve 39 is feedback-controlled via 8. As a result, the output torque of the engine 5 is controlled so as to converge to the engine control target value S _E.

When the left rear wheel speed V _RL continues to increase without the slip condition being eliminated by this engine control, the time point when the first slip ratio S ₁ exceeds the brake control start threshold value S _BO ( At t ₂ ), the braking pressure is supplied to the brake device 13 of the rear wheel 3, and the control using both the engine control and the brake control is performed. The braking pressure is feedback-controlled so that the first slip ratio S ₁ becomes the brake control target value S _B.

Then, when the first slip ratio S ₁ has decreased to the brake control target value S _B (t ₃ ), the brake control is stopped and the braking pressure is reduced. The engine control is performed until a predetermined ending condition is satisfied.

The above-mentioned control is similarly performed for the right rear wheel 4. That is, the ECU 40 subtracts the average front wheel speed V _F from the right rear wheel speed V _RR indicated by the signal from the wheel speed sensor 44 and divides this by the right rear wheel speed V _RR to obtain the second slip for the right rear wheel 4. Calculate the rate S ₂ . Then, when the second slip ratio S ₂ exceeds the engine control start threshold value S _EO set in the same manner as described above, engine control is started and the throttle opening is performed so that the engine control target value S _E is obtained. The sub throttle valve 39 is feedback-controlled via the degree adjusting actuator 38. Even with this engine control, the slip state is not resolved and the right rear wheel speed V
_RR continues to increase, and when the second slip ratio S ₂ exceeds the brake control start threshold value S _BO as described above, control using both engine control and brake control is performed. Then, when the second slip ratio S ₂ decreases to the brake control target value S _B , the brake control is stopped and the braking pressure is reduced.

In the present embodiment, in view of the fact that the rear wheels 3, 4 which are the driving wheels are more likely to slip when the vehicle is turning, as compared to when it is straight ahead, the ECU 40 is
It is detected that the vehicle is turning by the lateral acceleration G and the degree thereof, and the control start threshold values S _EO and S _BO and the control target values S _E and S _B in the traction control are decreased according to the increase of the lateral acceleration G. The correction is performed to prevent the occurrence of a large slip.

The lateral acceleration G is calculated by the following equation (2) in the ECU 40.

G = V ² × (1 / R) × (1/127) (2) Here, V is a vehicle speed (vehicle body speed), and the average front wheel speed V _F is used as the value. R is the turning radius of the vehicle and is a value calculated by the following equation (3).

R = Min (V _FL , V _FR ) × T ÷ | V _FL −V _FR │ + T / 2 (3) where Min (V _FL , V _FR ) is the front wheel 1, which is a driven wheel,
2 means the smaller wheel speed of the wheel speeds V _FL and V _FR , and | V _FL −V _FR | is the absolute value of the difference between the two wheel speeds V _FL and V _FR , and T is Vehicle tread (eg
1.7 m).

In the correction correction of the control start threshold values S _EO and S _BO and the control target values S _E and S _B , a correction coefficient k set so as to decrease as the lateral acceleration G increases is calculated, and this correction is performed. This is performed by multiplying the control start threshold values S _EO and S _BO and the control target values S _E and S _B by the coefficient k. At that time, the ECU 40 has a correction coefficient table as shown in Table 2 in which the lateral acceleration G of the vehicle is set as a parameter, and the correction coefficient k is calculated based on this table.

[0043]

[Table 2]

When the above-mentioned reduction correction is carried out indefinitely, the following problems occur. That is, the lateral acceleration G of the vehicle increases in proportion to the square of the vehicle speed V, as is clear from the above equation (1). Therefore, when the vehicle speed V increases, for example, the lateral steering angle θH decreases even when the steering angle θH decreases. The acceleration G has a very large value. For this reason, the control start threshold values S _EO and S _BO and the control target values S _E and S _B in the traction control are reduced more than necessary even at a small steering angle at which there is almost no possibility that a large slip will actually occur. This is corrected, and as a result, the driving force is reduced, which gives the driver a feeling of stall.

Therefore, in this embodiment, the EC
U also has a predetermined set vehicle speed V _T (eg V _T = 60).
In the vehicle speed range equal to or higher than km / h), the above-mentioned reduction correction is limited, so that the reduction of the driving force due to unnecessary reduction correction can be prevented and appropriate traction control can be performed. ing.

In this embodiment, the lateral acceleration G of the vehicle is a predetermined value G as a specific structure for limiting the above-described reduction correction.
_The reduction correction is allowed only when _T (for example, G _T = 0.2 G) or less, and when it exceeds the predetermined value G _T , the correction coefficient k for the reduction correction is set to the correction coefficient k corresponding to the predetermined value G _T.
It is designed to be fixed at _T (eg, k _T = 0.85).

Next, the operation of this embodiment will be described.

When the slip ratios S ₁ and S ₂ of the rear wheels 3 and 4 with respect to the road surface become equal to or higher than the engine control start threshold value S _EO , the ECU 40 brings the slip ratios S ₁ and S ₂ close to the engine control target value S _E. When the slip ratios S ₁ and S ₂ become equal to or higher than the brake control start threshold value S _BO , the brake control is performed to bring the slip ratios S ₁ and S ₂ closer to the brake control target value S _B. ..

Further, the ECU 40 performs the following correction control and correction limit control while performing such traction control.

[0050] That is, as shown in the flowchart in FIG. 4, the vehicle speed V is a judgment of whether or not equal to or higher than a predetermined vehicle speed V _T at step S1, if more predetermined vehicle speed V _T, the vehicle in step S2 It is determined whether the lateral acceleration G is equal to or greater than a predetermined value G _T. In the case of NO in either the determination result of step S1 or the determination result of step S2, the correction coefficient k is calculated based on the correction coefficient table (see Table 2) in step S3. That is, when the lateral acceleration G of the vehicle is not so large, the control start threshold values S _EO and S _BO and the control target values S _E and S _B are decreased and corrected according to the increase of the lateral acceleration G regardless of the magnitude of the vehicle speed V. To do. On the other hand, the determination results of steps S1 and S2 are both Y
In the case of ES, the correction coefficient k is fixed to k _T (that is, the correction coefficient set corresponding to the lateral acceleration G _T in the correction coefficient table). That is, when the vehicle speed V is high and the lateral acceleration G is also high, the reduction correction is limited.

As described in detail above, according to this embodiment,
By performing the above reduction correction, it is possible to prevent a large slip from occurring when the vehicle turns.
Moreover, under certain conditions, by limiting the above-mentioned reduction correction, the reduction of the driving force is caused by the reduction correction being performed more than necessary at the time of a small steering angle where there is little possibility that a large slip actually occurs. Can be prevented.

Although the lateral acceleration G of the vehicle is calculated from the vehicle specifications in the above embodiment (see the equations (2) and (3)), the lateral acceleration G is attached to the vehicle body by the acceleration sensor. Needless to say, it may be possible to detect directly.

In the above embodiment, the lateral acceleration G of the vehicle is
Is reduced to a predetermined value G _T or more, the reduction correction is limited, but instead of this, as shown in FIG. 5, whether the steering steering angle θH is a predetermined value θH _T or more is determined. The determination may be performed (step S2), and when the determination result is NO (that is, at the small steering angle), the reduction correction may be limited.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a vehicle slip control device according to the present invention.

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

FIG. 3 is a time chart showing the operation of the above embodiment (basic control of traction control).

FIG. 4 is a flowchart showing the operation (correction control and correction limit control) of the above embodiment.

5 is a view similar to FIG. 4, showing another embodiment of the vehicle slip control device according to the present invention.

[Explanation of symbols]

1, 2 front wheels 3, 4 rear wheels (driving wheels) 5 engine 8 differential device 13, 14 brake device 15 brake control system 36 accelerator pedal 38 throttle opening adjustment actuator 39 sub-throttle valve 40 ECU (driving force control means, correction) Means, correction limiting means) 41-44 Wheel speed sensor 46 First pressure sensor 47 Second pressure sensor 48 Accelerator position sensor 49 Steering angle sensor

Claims (5)

[Claims] 1. A drive force control means for controlling the drive force of the drive wheels so that the slip ratio approaches a predetermined target slip ratio when the slip ratio of the drive wheels with respect to the road surface becomes a predetermined value or more, and A slip control device for a vehicle, comprising: a correction unit that decreases and corrects a control target value or a control start threshold of the driving force control unit according to an increase in lateral acceleration, wherein the correction is performed in a vehicle speed region equal to or higher than a predetermined set vehicle speed. A slip control device for a vehicle, comprising a correction limiting means for limiting the reduction correction by the means. 2. The correction limiting means is configured to allow the reduction correction by the correction means only when the lateral acceleration of the vehicle is equal to or less than a predetermined value. Vehicle slip control device. 3. The correction limiting means is configured to allow the reduction correction by the correction means only when the steering angle of the vehicle is a predetermined value or more. 2. The vehicle slip control device according to 2. 4. The vehicle slip according to claim 1, 2 or 3, wherein the driving force control means is configured to control the driving force by limiting an engine output. Control device. 5. The driving force control means is configured to control the driving force by applying a braking force to the driving wheels. Vehicle slip control device. 5. The driving force control means is configured to control the driving force by limiting an engine output and applying a braking force to the driving wheels. The slip control device for a vehicle according to claim 1, 2 or 3.