JPH09226406A - Controller of differential limiting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out the optimum operation limiting control irrespective of changes in road surface μ, etc., by computing the steering angular velocity of a vehicle from a detection signal of a second sensor if deceleration of the vehicle is recognized from a detection signal of a first sensor, and determining the force of engagement of the clutch on the basis of the steering angular velocity. SOLUTION: Hydraulic pressure is supplied to a clutch 7 from a hydraulic pressure generator 9 in order to control the force of engagement of the clutch 7. A controller 10 outputs control signals for increasing or decreasing the hydraulic pressure. The controller 10 is an electronic control unit, performing predetermined arithmetic on signals that are input from a variety of sensors at every specified sampling time, and outputting control signals to the hydraulic pressure generator 9. The sensors include a first sensor which detects vehicle deceleration, that consists of a throttle opening sensor 11 and a brake switch 12, and a second sensor 2 serving as a steering angle sensor 13 that detects the steering angle of the vehicle by directly detecting the steering angle of the steering wheel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for controlling the differential limiting force of a limited slip differential (limited slip differential).

[0002]

2. Description of the Related Art Generally, a differential limiting device distributes and transmits a driving force from an engine to left and right driving wheels, and when a differential occurs due to a slip on those driving wheels, the differential is limited and driven. It is intended to prevent the wheel from idling and reliably transmit the driving force to the road surface. In recent years, there is a differential limiting device that has a friction multi-plate clutch inside and can control the differential limiting force by controlling the engaging force of this clutch.
In this case, the clutch engagement force is electronically controlled according to the running state of the vehicle, and in particular, conventionally, the clutch engagement force is controlled based on the deceleration of the vehicle to prevent tack-in or the like during deceleration turning. (Japanese Patent Application Laid-Open No. 5-185858, Japanese Patent Application Laid-Open No. 62-18330).

Particularly, in Japanese Unexamined Patent Publication No. 5-185858, the clutch engagement force (that is, the differential limiting force) is proportional to the deceleration at the time of reduction speed to strengthen the understeer tendency to prevent tack-in during turning, and at the time of high deceleration. The clutch engagement force is reduced to prevent strong understeer during turning.

Hereinafter, this point will be described in detail. When the vehicle decelerates, a load shift occurs between the front and rear wheels, causing the front wheel to be heavily loaded and the rear wheel to be lightly loaded. On the other hand, when a turn is applied to this deceleration, the front wheels have a heavy load, and thus the frictional force (grip) between road surfaces is increased, and the rear wheels are weakened.

FIG. 4 shows the state at this time. Since the front wheel a has a strong grip, a large lateral force Fyf for turning can be obtained, and the rear wheel b has a weak grip and a small lateral force Fyr.
You can only get it (for convenience, Fyf and Fyr are the same for the left and right wheels). Therefore, the moment around the center of gravity G due to these resultant forces M ₀ = 2Fyf · Lf −2Fyr · Lr (1) (Lf, Lr; vehicle-longitudinal distance from the center of gravity of the front and rear wheels) increases, and the vehicle is inside Phenomenon like getting caught in. This is the phenomenon of tuck-in.

By the way, at the time of turning, there is a difference in rotation between the left and right rear wheels as driving wheels due to the difference in turning trajectory. As shown in the figure, the left rear wheel rotates at a higher speed than the right rear wheel when making a right turn. .

When the differential limiting device limits the differential of the left and right rear wheels in this state, the left rear wheel tends to rotate at a low speed and the right rear wheel tends to rotate at a high speed. This strengthens the deceleration direction force (braking force) Fdrl of the left rear wheel and weakens the braking force Fdrr of the right rear wheel. And these braking force F
drl, Fdrr generate a moment in the opposite direction that reduces the moment M ₀ . That is, the moment M due to the total resultant force is M = M ₀ + Tr / 2 · Fdrr −Tr / 2 · Fdrl = 2Fyf · Lf −2Fyr · Lr + Tr / 2 · Fdrr −Tr / 2 · Fdrl (2) (Tr / 2; distance in the vehicle width direction from the center of gravity of the left and right rear wheels), and eventually the vehicle becomes understeer due to the differential limitation.

Therefore, in the above-mentioned Japanese Patent Laid-Open No. 5-185858,
The differential limiting control is executed based on the deceleration of the vehicle, the differential limiting force is increased at the time of reduction speed to prevent tack-in, and the differential limiting force is reduced at the time of high deceleration to prevent strong understeer. It is a translation.

Incidentally, in Japanese Patent Laid-Open No. 62-18330, the differential limiting force is made constant at a predetermined deceleration or higher.

[0010]

However, these conventional techniques have the following problems.

When the road surface μ changes, it is not possible to perform decelerating turning traveling in accordance with the driver's intention.

On a road surface having a small coefficient of friction, such as a snowy road, a large deceleration does not occur, so that only a small differential limiting force can be obtained. Further, if the driven wheel is locked by the foot brake, the deceleration is detected from the driven wheel, which results in excessive differential limitation. In this way, if the control is based on deceleration, tack-in and understeer will appear conspicuously regardless of the driver's intention. In particular, in the above-mentioned conventional technique, the deceleration of the vehicle is detected by the differential value of the vehicle speed or the wheel speed, or the deceleration sensor, but even this cannot detect tack-in or understeer.

A map of the differential limiting force based on deceleration needs to be created every time the vehicle specifications differ.

For example, vehicle weight, distance from the center of gravity of the front and rear wheels, suspension characteristics (spring, shock absorber)
Due to differences and changes in the above, the degree of load change and the tire grip will differ, and it will be necessary to change the map. Conversely, the map of the differential limiting force is limited to the value when the specific vehicle is traveling on the specific road surface.

[0015]

SUMMARY OF THE INVENTION The present invention is a differential limiting device having a clutch for limiting the differential between the left and right driving wheels, and is a control device for controlling the engaging force of the clutch. A first sensor for detecting deceleration of the vehicle, a second sensor for detecting a steering angle of the vehicle,
A controller for calculating the steering angular velocity of the vehicle from the detection signal of the second sensor when determining deceleration of the vehicle from the detection signal of the first sensor, and determining the engagement force of the clutch based on the steering angular velocity. It is equipped with and.

In this case, when the vehicle is decelerating, the clutch engagement force, that is, the differential limiting force is determined based on the steering angular velocity, not the deceleration. That is, when the vehicle decelerates, the driver applies counter steering to reduce the steering angle if tack-in occurs, and if under-steering occurs, the driver increases the steering angle to increase the steering angle. So the controller
The differential limiting force is uniquely determined based on the increase or decrease of the steering angle or according to the steering operation of the driver. This makes it possible to execute optimal differential limiting control regardless of changes in road surface μ, vehicle characteristics, etc., which allows the driver to make a decelerated turn as the driver wishes, and has an extremely superior ability to respond. It becomes a thing.

[0017]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 2 shows a vehicle equipped with a control device for a differential limiting device according to the present invention, and the direction of the arrow indicates the front of the vehicle. In this vehicle, the driving force generated by the engine 1 is transmitted to the differential mechanism 4 via the transmission 2 and the propeller shaft 3, and the driving force is distributed to the left and right drive shafts 5 in the differential mechanism 4. The left and right drive wheels 6 are driven. Here, the vehicle is an FR vehicle having the engine 1 at the front and the rear wheels 6 as driving wheels.

The differential mechanism (differential) 4 has a general structure having a plurality of differential gears in a differential case, and while distributing the driving force to the left and right drive shafts 5, the drive shafts 5 of the drive shafts 5 are also transmitted. Allows free differential or relative rotation. The differential of the differential mechanism 4 is appropriately limited according to the engaging force of the clutch 7. The clutch 7 is a friction multi-plate clutch in which a fastening force is controlled by receiving a hydraulic pressure. A differential limiting device (limited slip differential) 8 is a combination of the differential mechanism 4 with a clutch 7 and a mechanism for controlling the clutch 7. The differential limiting device 8 has the same structure as in Japanese Patent Laid-Open No. 5-185858 and is shown separately in the figure, but the clutch 7 and the differential mechanism 4 are integrated and housed in the same housing. There is.

To control the engagement force of the clutch 7, a hydraulic pressure is supplied to the clutch 7 from a hydraulic pressure generator 9. The controller 10 outputs a control signal for increasing or decreasing the hydraulic pressure. The controller 10 is an electronic control device, which inputs signals from various sensors at predetermined sampling times, performs predetermined calculations, and outputs control signals to the hydraulic pressure generator 9. Here, the controller 10 is an ECU and simultaneously executes fuel injection control of the engine 1 and the like.

As the sensor, a throttle opening sensor 11 for detecting the throttle opening of the engine 1 in conjunction with an accelerator pedal, a brake switch 12 which is turned on / off by depressing and returning the brake pedal, and a steering angle of a steering wheel. Steering angle sensor 13 (second sensor) for detecting the steering angle of the vehicle, and a lateral G sensor 14 for detecting lateral G (lateral acceleration) of the vehicle.
(Third sensor) is provided.

FIG. 1 is a flow chart of control executed by the controller 10.

First, at step 101, it is judged whether or not the brake switch 12 is ON. If it is ON, the process proceeds to step 103, and if it is OFF, the process proceeds to step 102. At step 102, the detected value TPS of the throttle opening sensor 11
Is smaller than the threshold value TPS0. If it is smaller than TPS0, the routine proceeds to step 103, and if it is larger than TPS0, the control by this flow is ended.

In these steps 101 and 102, it is judged whether or not the vehicle deceleration condition is satisfied.
That is, when it is determined in step 101 that the brake operation is being performed, or when it is determined in step 102 that the accelerator pedal is returned from the predetermined position and the engine brake is applied, the vehicle is decelerated. In other words, the clutch engagement force control is executed in the flow from step 103 onward.

As described above, the throttle opening sensor 11 and the brake switch 12 form a first sensor for detecting the deceleration of the vehicle.

Next, in step 103, the lateral G sensor 1
4 is input to read the lateral GYg of the vehicle, and the detection signal of the steering angle sensor 13 is input to input the steering angle STRn of the vehicle.
Read. Here, the lateral GYg value is positive in the left direction,
The steering angle STRn is positive in the clockwise direction. In particular, for the steering angle STRn, the previous value STRn-1 of one sampling time before is stored in the controller 10.

Next, at step 104, the steering angular velocity DSTR is calculated from the difference between the present and previous steering angles STRn, STRn-1.
That is, the steering angular velocity DSTR is calculated by the following equation.

DSTR = STRn-STRn-1 Then, in step 105, the turning direction of the vehicle is determined from the value of the lateral GYg. That is, if the value of Yg is positive, it is determined that the vehicle is making a right turn, and the process proceeds to step 106. If the value of Yg is 0 or a negative value, it is determined that the vehicle is making a left turn, and step 10 is performed.
Go to 7.

In step 106, the map 1 shown in FIG. 3A is selected. This map 1 shows the steering angular velocity
The relationship between DSTR and the target engagement force T of the clutch 7 is represented and stored in the controller 10 in advance. In Map 1, the target fastening force T is a constant value T ₀ when DSTR ≦ −DSTR1 (where DSTR1 is a positive value), and −DSTR
DS when 1 ≤ DSTR ≤ DSTR2 (where DSTR2 is a positive value)
As TR increases, it decreases from T ₀ to 0 at a constant rate, and DSTR
It takes a value of 0 when ≥ DSTR2.

After this, the process proceeds to step 108,
The target fastening force T based on the steering angular velocity DSTR is calculated from the map 1, and the control flow ends.

When the target engagement force T is calculated in this manner, a control signal corresponding to the calculated target engagement force T is sent to the hydraulic pressure generator 9 to obtain the clutch engagement force according to the target engagement force T and to limit the differential force. Differential limiting control of the device 8 can be performed.

On the other hand, if it is determined in step 105 that the vehicle is making a left turn, the routine proceeds to step 107, where the map 2 shown in FIG. 3B is selected.

This map 2 is also similar to map 1, and steering angular velocity
The relationship between the DSTR and the clutch target engagement force T is shown. In particular, the map 2 is a map 1 symmetrical with respect to the T axis. Therefore, the target fastening force T is 0 when DSTR ≤ -DSTR2.
When -DSTR2 ≤ DSTR ≤ DSTR1, it increases from 0 to T ₁ at a constant rate as DSTR increases, and when DSTR ≥ DSTR1, it becomes a constant value T ₀ . When DSTR = 0, it takes the same value T ₁ .

Next, at step 109, the target engagement force T based on the steering angular velocity DSTR is calculated from the map 2 and the control flow ends. When the target engagement force T is calculated, a control signal corresponding to this is sent to the hydraulic pressure generator 9 to control the clutch engagement force or the differential limiting force.

Next, the operation of the above-described clutch engagement force control on the vehicle actually running will be specifically described. Here, the case of decelerating right turn is taken as an example.

First, when a tuck-in occurs such that the vehicle rolls inward (right side) in the turning direction, the driver applies counter-steer to prevent the rolling-in, that is, performs steering operation to the left side opposite to the turning direction. Becomes

Since the right rotation of the steering angle sensor 13 is positive, the steering angular velocity DSTR becomes negative, and as a result, as shown in FIG.
A predetermined target fastening force T is given from the map 1 of (a),
The differential limitation corresponding to this is executed.

In this case, as described above, the understeer tendency is strengthened and the tack-in can be prevented.

Next, when an understeer occurs in which the vehicle bulges outward (left side) in the turning direction, the driver further increases the steering, that is, the steering operation is further performed to the right side in the same direction as the turning direction.

Then, the steering angular velocity DSTR becomes positive, so that the target fastening force T becomes 0 and the differential limitation is not executed.
Understeer is not strengthened by this,
The vehicle will make more turns due to the steering operation.

In the case of decelerating left turn, the same differential limiting control based on the map 2 of FIG. 3B is executed.

As described above, such a device does not execute the differential limiting control based on the deceleration as in the conventional case, but executes the differential limiting control based on the steering angular velocity. In this way, the occurrence of tuck-in or understeer can be known from the driver's steering operation, and the differential limiting control can be executed according to this to eliminate the above-mentioned problems. In other words, even if the road surface μ changes, it becomes possible to perform decelerating turning traveling as the driver's intention, steering stability and safety are improved, and it is not necessary to change the map due to changes in vehicle specifications. It will be extremely good.

By the way, in the above control, the turning direction is specified from the detected value Yg of the lateral G sensor 14, and the map 1
Alternatively, one of the maps 2 is selected.

However, map 1 and map 2 are T
Because of the axial symmetry, for example, after the turning direction is specified, the sign of the steering angular velocity DSTR may be inverted (positive / negative inversion) in the process of calculating the target engagement force T, and the same map may be used.

Further, the present invention is not limited to the above-mentioned form, but may be embodied in other forms. For example, a throttle opening sensor is provided in the throttle valve, or the steering angle of the front wheel, which is the steered wheel, is directly detected by the steering angle sensor. You can also do it. Also,
It is also possible to detect the deceleration with the differential value of the throttle opening, the front-rear G sensor, specify the turning direction with a wheel speed sensor or the like. Further, the engagement force of the clutch can be controlled by electromagnetic force. The present invention is not limited to FR vehicles, but FF
It is also applicable to cars, 4WD cars and the like.

[0046]

The present invention exhibits the following excellent effects.

(1) It is possible to perform decelerating turning traveling as intended by the driver without depending on the change of the road surface μ, and steering stability and safety are improved.

(2) Since the map does not need to be changed due to the change of the vehicle specifications, the support capability is extremely excellent.

[Brief description of drawings]

FIG. 1 is a flowchart of control by a control device according to the present invention.

FIG. 2 is a configuration diagram showing a vehicle provided with a control device according to the present invention.

FIG. 3 is a map for determining a target engagement force of a clutch.

FIG. 4 is a model diagram showing an external force applied to a wheel during deceleration turning.

[Explanation of Codes] 6 Rear Wheel (Drive Wheel) 7 Clutch 8 Differential Limiting Device 10 Controller 11 Throttle Opening Sensor (First Sensor) 12 Brake Switch (First Sensor) 13 Steering Angle Sensor (Second Sensor) ) 14 Lateral G sensor (3rd sensor) DSTR Steering angular velocity T Target clutch engagement force

[Procedure amendment]

[Submission date] April 25, 1996

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] All figures

[Correction method] Change

[Correction contents]

FIG.

[Fig. 2]

[Figure 3]

FIG. 4

Claims (3)

[Claims] 1. A differential limiting device having a clutch for limiting the differential between the left and right drive wheels, the control device for controlling the engagement force of the clutch, and detecting deceleration of a vehicle. A first sensor for detecting the steering angle of the vehicle, a second sensor for detecting the steering angle of the vehicle, and a detection signal of the second sensor when the deceleration of the vehicle is determined from the detection signal of the first sensor. And a controller that calculates the steering angular velocity of the vehicle from the vehicle and determines the engagement force of the clutch based on the steering angular velocity. 2. A third sensor for detecting the turning direction of the vehicle is further provided, wherein the controller determines the turning direction of the vehicle from the detection signal of the third sensor, and from a map different for each turning direction. The control device for the differential limiting device according to claim 1, wherein the engagement force of the clutch is determined based on the steering angular velocity. 3. The control device for a differential limiting device according to claim 2, wherein the first sensor comprises a brake switch and a throttle opening sensor, and the third sensor comprises a lateral G sensor.