JPH06144066A - Differential limiting controller for vehicle - Google Patents

Abstract

PURPOSE:To reconcile accelerability on a high mu road and car stability on a low mu road. CONSTITUTION:A vehicle differential limiting controller, which controls a differential limiting force by a differential limiter 3 limiting the differential rotation of symmetrical wheels 1 and 2, is provided with a road surface friction factor detecting mrans 4 detecting a friction factor on a road surface, a revolution difference detecting means 5 detecting a revolition difference between both right and left wheels 1 and 2, an engine power detecting means 6 detecting the extent of engine power, a differential limiting force setting means 7 setting a differential limiting force according to the engine power mainly when the friction factor on the road surface is large enough, and when this factor is small, setting the differential limiting force mainly according to the revolution difference between both these right and left wheels respectively, and an output means 8 outputting an indication signal to the differential limiter 3 so as to achieve the differential limiting force det by the differential limiting force setting means 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a differential limiting device for limiting the differential rotation of left and right wheels, and more particularly to a differential limiting control device for controlling the differential limiting force.

[0002]

2. Description of the Related Art Drive wheels such as left and right rear wheels to which power is transmitted are connected to a propeller shaft via a differential device in order to enable smooth turning. If the differential action of this differential device is limited by a limiting means such as a friction clutch, the distribution state of the torque to the left and right wheels changes according to the degree of the limitation, and it becomes easy to escape from a mud road or the like. In addition, the turning performance and acceleration performance change. That is, the behavior stability of the vehicle can be improved depending on the method of limiting the differential. Therefore, for example, in the device disclosed in Japanese Patent Laid-Open No. 3-86633, differential operation is performed according to the difference in the rotational speeds of the left and right wheels. There is described a device for increasing the limiting force and correcting the decrease according to the vehicle speed and the steering angle. According to this device, when the vehicle is turning or traveling at a high speed, the differential limiting force is weakened even if differential rotation of the left and right wheels occurs, so that it is said that the turning performance and the straight running stability are improved.

[0003]

However, in the above-mentioned conventional device, since the differential limiting torque is basically increased by the occurrence of the differential rotation of the left and right wheels, the differential rotation is prevented. Until the occurrence, the differential limitation is not performed, or the differential limitation is kept low. Therefore, even if the driver depresses the accelerator pedal to obtain high acceleration, the differential limitation is not particularly performed in the state where the differential rotation of the left and right wheels does not occur, and as a result, the difference between the left and right wheels Since the torque distribution according to the friction coefficient is not performed, there is a disadvantage in that the acceleration performance intended by the driver cannot be obtained.

In order to eliminate such an inconvenience, it is conceivable to increase the throttle opening and simultaneously increase the differential limitation. However, such control is performed with a low μ having a small road surface friction coefficient.
If it is performed on a road, slipping of the wheels is likely to occur and the behavior of the vehicle may become unstable.

Further, it is conceivable to control the differential limitation in accordance with the slip ratio of the wheels. Although such control stabilizes the behavior of the vehicle, the sporty traveling in which the slip ratio is ignored and the vehicle is controlled. In such a case, there is a problem that the turning performance is deteriorated and the driver cannot travel as intended.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a differential limiting control device capable of achieving both acceleration and running stability on a low μ road. is there.

[0007]

The present invention is characterized in that it has the structure shown in FIG. 1 in order to achieve the above object. That is, the present invention is a vehicle differential limiting control device for controlling the differential limiting force by the differential limiting device 3 that limits the differential rotation of the left and right wheels 1 and 2, and detects a road surface friction coefficient for detecting a road surface friction coefficient. Means 4 and left and right wheels 1,
The rotational speed difference detecting means 5 for detecting the rotational speed difference of No. 2, the engine output detecting means 6 for detecting the magnitude of the output of the engine, and the differential depending on the engine output when the friction coefficient of the road surface is large. When the limiting force is determined and the road surface friction coefficient is small, it is determined by the differential limiting force determining means 7 and the differential limiting force determining means 7, which mainly determines the differential limiting force according to the rotational speed difference between the left and right wheels. Output means 8 for outputting an instruction signal to the differential limiting device 3 so as to achieve the differential limiting force.

[0008]

The differential limiting force in the present invention is determined based on the engine output or the difference in rotational speed between the left and right wheels 1, 2,
Which of them depends on the friction coefficient of the road surface. That is, when the road surface friction coefficient is large, the differential limiting force is determined mainly in accordance with the increase of the engine output. On the contrary, when the road surface friction coefficient is small, the left and right wheels 1, 2 are mainly used.
The differential limiting force is determined according to the differential rotation speed of. In addition,
The road surface friction coefficient, the rotational speed difference between the left and right wheels 1 and 2, or the engine output is detected by the respective detection means 4, 5, and 6. Therefore, when the engine output is increased by depressing the accelerator pedal or the like on a high μ road, the differential limiting force is increased at the same time, and as a result, acceleration with good response can be performed. Further, on a low μ road, the differential limiting force is increased by increasing the rotational speed difference between the left and right wheels 1 and 2 rather than by increasing the engine output, and thus the slip ratio of one wheel is increased. When a situation arises, the differential limitation is strongly performed and the behavior of the vehicle is stabilized.

[0009]

EXAMPLES Next, the present invention will be described more specifically based on examples. FIG. 2 is a block diagram showing an embodiment of the present invention. In the example shown here, an F in which the left and right rear wheels 10, 11 are driven by an engine 12 mounted on the front side
This is an example in which the present invention is applied to an R (front engine / rear drive) vehicle, in which a propeller shaft 13 is provided with a differential gear 14 having a built-in differential limiting mechanism so that the left and right rear wheel axles 1 can be driven.
5, 16 are connected.

A conventionally known differential device can be used as the differential device 14, and an example thereof is shown in FIG. 3 and is for transmitting power from the propeller shaft 13. A pinion gear 19 having its axis oriented in a direction orthogonal to the axis of the ring gear 17 is held inside a differential case 18 to which the ring gear 17 is attached. (Only one side gear is shown) 20 is provided. One end of a shaft 21 is spline-fitted to the side gear 20, and a sleeve 22 is spline-fitted to the other end of the shaft 21.
A plurality of friction plates 23 are spline-fitted.

On the other hand, a transmission member 24 is relatively rotatably fitted to the outer periphery of the shaft 21, and the transmission member 2 is provided therewith.
One end of 4 is spline-fitted to the differential case 18, and the other end is formed in a cylindrical shape having a diameter larger than that of the friction plate 23, and another friction plate arranged alternately with respect to the friction plate 23. 25 is spline-fitted to the inner peripheral surface of the large-diameter cylindrical portion. Further, these friction plates 23, 2
5, the piston 26 is arranged on the same axis, and by supplying the differential limiting hydraulic pressure to the hydraulic chamber 27 on the back side of the piston 26, the friction plates 23 and 25 are pressed to make frictional contact. The torque is transmitted between the differential case 18 and the side gear 20 to limit the differential. That is, the differential limiting clutch 28 is formed here.

A hydraulic device 29 for supplying / discharging the differential limited hydraulic pressure to the hydraulic chamber 27 and a hydraulic control device 30 for controlling the hydraulic pressure are provided. FIG. 4 shows a hydraulic system 2
9, a relief valve 33 is connected to a discharge port of a pump 32 that pumps and pressurizes oil from a reservoir tank 31. A current control pressure reducing valve 35 is connected to the discharge port via a check valve 34, and an accumulator 36 is connected between the check valve 34 and the current control pressure reducing valve 35. Therefore, the relief valve 33
The constant hydraulic pressure determined by the accumulator 36 and the accumulator 36 is supplied to the current control pressure reducing valve 35.

The current control pressure reducing valve 35 changes the output pressure according to the current value, and is configured to increase the output pressure in proportion to the current value, and its output port is located in the hydraulic chamber 27. It is connected. Therefore, the additional hydraulic pressure of the differential limiting clutch 28 is proportional to the control current I, and an example of the characteristic is shown in FIG. The hydraulic control device 30 controls the current of the current control pressure reducing valve 35, and is mainly composed of a central processing unit (CPU), a storage device (ROM, RAM), and an input / output interface. The hydraulic control device 30 is connected to the left and right wheel rotation speed sensors 37, the throttle opening sensor 38, the vehicle speed sensor 39, the acceleration sensor 40, and the like. The hydraulic control device 30 calculates the additional hydraulic pressure P to be set based on the data input from these sensors, etc., and obtains the current value that is the hydraulic pressure P from the characteristic line of FIG. 5 which is stored as a map. The pressure is output to the current control pressure reducing valve 35 described above.

Next, the operation of the above-mentioned device will be described with reference to the flowchart of FIG. First, the longitudinal acceleration (Gx) is read (step 100), and it is determined whether the value is a positive value (step 101). That is, it is determined whether to accelerate or decelerate, and in the case of acceleration (when the determination result of step 101 is "yes"), a value obtained by doubling the value is adopted (step 102). This is intended for a vehicle in which the rear two wheels are drive wheels, and in the case of acceleration is doubled compared with the case of deceleration so as to match the acceleration obtained from the friction coefficient between the wheel and the road surface. . If the determination result of step 101 is "NO" or after the process of step 102 is performed, the lateral acceleration (Gy) is read (step 10).
3). Then, the vector sum Gxy of the longitudinal acceleration Gx and the lateral acceleration Gy is calculated (step 104). This vector sum Gxy is a value smaller than the road surface friction coefficient, but since it is a value that increases or decreases in accordance with the road surface friction coefficient, the road surface friction coefficient μ can be estimated by this vector sum Gxy.

At step 105, the rotational speeds of the two rear wheels, which are the driving wheels, are read, and subsequently, at step 1
At 06, the rotation speed difference Δω is calculated. This finds the absolute value of the difference between the rotational speed omega _RR rotation speed omega _RL and the right wheel of the left wheel. Subsequently, the throttle opening θ corresponding to the magnitude of the engine output is read (step 107), and at the same time, the correction coefficient Kω for the rotational speed difference Δω and the correction coefficient K _{θ for the} throttle opening θ are calculated as described above. Acceleration vector sum G
Obtained from a map with xy as a parameter.

The map for obtaining the correction coefficient Kω for the rotational speed difference Δω is as shown in FIG. 7, and its value is set to a larger value as the acceleration vector sum Gxy is smaller.
It decreases as the vector sum Gxy increases, and the vector sum Gxy
Is set to be a constant value when is a predetermined value or more. The correction coefficient K _theta throttle opening theta Further, contrary to this, in the vector sum Gxy is than the predetermined value, while being set to a constant value, vector sum Gxy at higher
Is set to a large value in accordance with the increase of, and the maximum value is specified.

The additional hydraulic pressure P supplied to the differential limiting clutch 28 is the product of the rotational speed difference Δω and its correction coefficient Kω,
It is calculated as the sum of the product of the throttle opening θ and its correction coefficient K _θ (step 109), and the control current I for achieving the additional hydraulic pressure P thus calculated is obtained from the map shown in FIG. , Output this (step 11
0).

Therefore, when the vehicle runs on a high μ road where the acceleration vector sum Gxy appears as a large value, the value of the latter correction coefficient K _θ of the throttle opening θ is large among the correction coefficients Kω and K _θ. Since the former correction coefficient Kω for the rotational speed difference Δω has a small value, the increase in the throttle opening θ largely acts as a factor for increasing the additional hydraulic pressure P, that is, the differential limiting force. That is, on the high μ road, the differential limitation is performed by increasing the throttle opening θ rather than increasing the rotational speed difference ω between the left and right wheels. Therefore, for example, when the driver attempts to accelerate by depressing the accelerator pedal, the differential limiting force increases as the throttle opening θ increases, so that the left and right wheels generate drive torque according to the road surface μ and Acceleration can be obtained.

[0019] When the vehicle runs a low μ road is appearing as Betokuru sum Gxy a small value of acceleration with respect to this, the correction coefficient K?, Large correction coefficient K? Of the former rotational speed difference ω of K _theta , Correction coefficient K for the latter throttle opening θ
_Since the value of _θ becomes a small value, the increase of the rotation speed difference Δω largely works as a factor for increasing the additional hydraulic pressure P, that is, the differential limiting force. That is, on the low μ road, the differential limitation is performed by increasing the rotational speed difference Δω between the left and right wheels rather than increasing the throttle opening θ. Therefore, when traveling on a low μ road, the differential limitation does not become particularly strong even when the accelerator pedal is depressed, and the differential limitation becomes stronger due to the change in the rotational speed difference Δω between the left and right wheels, so that one wheel slips, etc. It is possible to suppress the situation and secure the stability of the vehicle.

It should be noted that the present invention is not limited to the above-described embodiments, and applicable vehicle drive types, structures of differential devices, etc. are other than those shown in the above-mentioned embodiments. It may be. Further, instead of detecting the engine output based on the throttle opening θ, the engine output may be detected based on other parameters such as the intake pipe negative pressure. Further, the friction coefficient of the road surface may be detected based on a parameter other than acceleration.

[0021]

As is apparent from the above description, the differential limiting control device of the present invention performs differential limiting mainly on the high μ road in accordance with the magnitude of the engine output, and on the low μ road, mainly the left and right sides. Since the differential limitation is performed according to the differential rotation speed of the wheels, it is possible to respond quickly to accelerator operation on high μ roads and obtain high acceleration performance, while at the same time stabilize vehicle behavior on low μ roads. This can be ensured, and both the running intended by the driver and the running stability can be made compatible.

[Brief description of drawings]

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

FIG. 2 is a block diagram schematically showing an embodiment of the present invention.

FIG. 3 is a sectional view of a differential device.

FIG. 4 is a hydraulic circuit diagram for controlling differential limiting clutch pressure.

FIG. 5 is a map showing the relationship between differential limiting clutch hydraulic pressure and control current.

FIG. 6 is a flowchart showing a routine for controlling differential limiting clutch hydraulic pressure.

FIG. 7 is a map for obtaining a correction coefficient for the rotational speed difference between the left and right wheels based on the vector sum of accelerations.

FIG. 8 is a map for obtaining a correction coefficient for the throttle opening based on the vector sum of accelerations.

[Explanation of symbols]

 1 and 2 wheels 3 differential limiting device 4 road surface friction coefficient detecting means 5 rotational speed difference detecting means 6 engine output detecting means 7 differential limiting force determining means 8 output means

Claims (1)

[Claims] 1. A vehicle differential limiting control device for controlling a differential limiting force by a differential limiting device for limiting differential rotation of left and right wheels, and road surface friction coefficient detecting means for detecting a friction coefficient of a road surface, and right and left. Rotational speed difference detection means for detecting the rotational speed difference of the wheels, engine output detection means for detecting the magnitude of the output of the engine, and when the friction coefficient of the road surface is large, the differential limiting force is mainly applied according to the engine output. When the road surface friction coefficient is small, the differential limiting force determining means determines the differential limiting force mainly according to the rotational speed difference between the left and right wheels, and the differential limiting force determining means determines the differential limiting force. And a means for outputting an instruction signal to the differential limiting device so as to achieve the above.