JP2732140B2 - Control device for limited slip differential - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a control device for a limited slip differential, and in particular, a friction plate is provided between one side gear and a differential case, and the friction plate is controlled by an actuator such as an air cylinder. The present invention relates to a limited slip differential control device in which differential limiting is performed by setting a connection state.

[Summary of the Invention]

When the friction plate is connected by an actuator such as an air cylinder, the side gear and differential case are connected to limit the operation. The operation of the differential is released, whereby the straight running stability is improved, and the lowering of the stability limit at the time of turning is prevented.

[Conventional technology]

When a car turns, the outer wheels travel a longer distance than the inner wheels. In order to absorb the difference between the rotational speeds of the left and right wheels, especially the drive wheels during turning, a differential device (differential device) is interposed between the left and right drive shafts. The rotation of the propeller shaft is automatically transmitted to the left and right wheels at different rates due to the difference between the resistances applied to the left and right drive wheels during the turn, so that the vehicle turns without causing excessive force in each part.

However, if such a differential is provided, the wheels will slip when one of the wheels falls into mud or when traveling on a road surface having a low friction coefficient such as a snowy road. That is, the starting performance and the running performance on a road surface having a low friction coefficient are impaired by the differential. In order to solve such a drawback, a differential lock device is provided in the differential, or a limited slip differential is attached.

[Problems to be solved by the invention]

When such a limited slip differential is operated during high-speed running, the straightness of the vehicle is improved, and the straight running stability is ensured. However, when the differential limitation is performed by the limited slip differential, there is a problem that the stability limit at the time of turning relatively decreases.

At the time of turning, a lateral force that tilts the vehicle body to the side opposite to the turning center is generated, so that the contact force of the drive wheel on the turning center side becomes low, and vehicles without limited slip differential or limited When the differential limitation by the slip differential is not performed, the wheel on the turning center side idles. Therefore, no driving force is applied to the driving wheel opposite to the turning center, and the propulsion of the vehicle is lost.

However, at this time, if the differential slip is limited by the limited slip differential, idling of the drive wheel on the turning center side is prevented, and the driving force is reliably transmitted to the opposite drive wheel to generate propulsion. Moreover, at this time, since the front wheels are steered toward the turning center, the lateral force is reduced and the turning performance is reduced. That is, there is a problem that when the differential limit is performed by the limited slip differential during turning, the stability limit of the vehicle is reduced.

The present invention has been made in view of such a problem, and an object of the present invention is to provide a limited slip differential control device capable of improving straightness without lowering a stability limit during turning. It is assumed that.

[Means for solving the problem]

The present invention relates to a limited slip differential in which a friction plate is provided between one side gear and a differential case, and the friction plate is connected by a cylinder constituting an actuator so as to limit the differential. Calculating means for calculating the lateral acceleration applied to the vehicle from the steering angle of the vehicle, and determining whether or not the lateral acceleration is lower than a preset value at the vehicle speed in the normal steering range from the lateral acceleration and the vehicle speed obtained by the calculating means. The present invention relates to a control device for a limited slip differential, comprising a judgment means for judging, and canceling the operation when the vehicle goes beyond a normal steering range during turning.

Another invention provides a limited slip differential in which a friction plate is provided between one side gear and a differential case, and the friction plate is connected by a cylinder constituting an actuator to limit the differential. Control means for controlling the operating pressure applied to the actuator of the limited slip differential according to the steering angle and the steering angle. The control means controls the operating pressure for preventing the slip of the drive wheels by limiting the differential when the vehicle speed is zero. And a control device for a limited slip differential, wherein the operating pressure is reduced at an extremely low speed, and the operating pressure is increased as the vehicle speed increases.

[Action]

Therefore, according to the present invention, the lateral acceleration applied to the vehicle is obtained by calculation from the vehicle speed and the steering angle of the front wheels, and it is determined whether the vehicle is in a normal steering range from the lateral acceleration and the vehicle speed, and the lateral acceleration is set in advance at that vehicle speed. When the normal steering range lower than the set value is exceeded, the differential limitation of the limited slip differential is released.

According to another invention, the operating pressure applied to the limited slip differential actuator is controlled by the control means, and when the vehicle speed is 0, the operating pressure for preventing the drive wheels from slipping due to the differential limitation is applied to the actuator. At extremely low speeds, the operating pressure of the actuator is kept low, and as the vehicle speed increases, the operating pressure applied to the actuator increases.

〔Example〕

FIG. 1 shows a limited slip differential according to an embodiment of the present invention. The limited slip differential includes a drive pinion 10. The drive pinion 10 is connected to the tip of the propeller shaft,
The carrier case 11 is rotatably supported by front and rear bearings 12 and 13. The drive pinion 10 is designed to mesh with the ring gear 14. Ring gear 14
Is fixed to a differential case 16 by bolts 15.

Inside the differential case 16, a pair of left and right side gears 17, 18 are arranged. These side gears 17 and 18 are driven shafts 19 and 20
And a spline, respectively, so that the driving force of the engine is transmitted to the drive wheels via the drive shafts 19 and 20. In the differential case 16, there are four differential pinions 21,
22 are arranged. These differential pinions 21 and 22 are supported by a differential case 16 via a cross-shaped spider 23. The differential case 16 is rotatably supported by bearings 24 on both sides about the axis of the drive shafts 19 and 20.

In FIG. 1, a casing 27 constituting an air cylinder is mounted on the right side of the differential case 16. A piston 28 is provided in the air cylinder 27 and presses friction plates 29 and 30 which are alternately arranged so as to be stacked on each other. The friction plate 29 of the friction plates 29, 30 in the casing 27 has its outer peripheral portion engaged with the spline 31 of the casing 27, and the friction plate 30 has its central portion connected to the spline 32 of the side gear 17. It is designed to engage.

An air pipe is connected to the casing 27 of the limited slip differential air cylinder through a joint 35.
36 is connected. This air pipe 36 has an air tank 37
Is connected, and a solenoid valve 38
Are connected. Further, a branch pipe 39 for exhaust is connected to the air pipe 36, and the branch pipe 39
Is connected to a solenoid valve 40.

The pair of solenoid valves 38 and 40 are controlled by a controller 43 composed of a computer. The pressure gauge 44 connected to the branch pipe 39 is connected to the controller
Connected to 43. Furthermore, rotation detection sensors 45 to 45 detect the respective rotation speeds of the left and right front wheels and the left and right rear wheels of the vehicle.
48 is connected to the controller 43. Further, a steering angle sensor 49 for detecting a steering angle of the front wheels,
A manual switch 50 for switching the operation of the limited slip differential by a manual operation is connected to the controller 43.

In the above configuration, the air cylinder having the friction plates 29 and 30 from the limited slip differential shown in FIG.
If you remove 27, it will work as a normal differential. That is, the torque transmitted via the propeller shaft is transmitted to the ring gear 14 by the drive pinion 10, and
The case 16 to which the 14 is fixed rotates. Differential case 16
Is mounted with four differential pinions 21 and 22 via a spider 23, so that when the resistance of the left and right drive wheels is the same, the differential pins 21 and 22 rotate by hooking the left and right side gears 17 and 18. Will do. Therefore, in this case, torque is transmitted to the left and right drive wheels through the drive shafts 19 and 20 at the same rotational speed. The rotation speed of the drive wheels at this time is
It becomes equal to the number of rotations.

On the other hand, if the resistance of one of the drive wheels increases, the side gear 17 connected to the drive wheel becomes difficult to rotate, so the differential pinions 21 and 22 rotate with the differential case 16 while rolling on the side gear 17. . Therefore, in this case, the rotation associated with the revolution of the differential case 16 and the differential pinion 2
The rotation associated with the rotation of the wheels 1 and 22 is applied to the drive shaft 20 via the side gear 18, so that the rotation speed of the drive wheel with low resistance increases. In this way, when the vehicle turns, the difference in the number of revolutions is absorbed according to the traveling distance of the left and right drive wheels.

When the solenoid valve 38 is switched by the controller 43, the air stored in the air tank 37 is supplied to the air cylinder 27 through the air pipe 36, and the piston 28 is pushed to the left in FIG. Then, the piston 28 frictionally connects the friction plates 29 and 30 to each other. Friction plate 29 is case 27
Since the friction plate 30 is engaged with the spline 32 on the outer peripheral surface of the boss of the side gear 17 on the side spline 31, respectively, when the friction plates 29, 30 are frictionally coupled to each other, the side gear 17 becomes the friction plate 29, It will be mechanically connected to the differential case 16 via the casing 30 and the casing 27. Then, since the relative movement between the differential gears 21 and 22 supported by the differential case 16 via the spider 23 and the side gear 17 is not allowed in the middle, a differential limiting state is set. This limits the differential to its original function and only has the function of transmitting the rotational speed to the left and right drive wheels approximately equally.

FIG. 2 shows the operation of the limited slip differential control by the computer 43. The rotation speeds of the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel are measured by the four rotation sensors 45 to 48, respectively. Reads. Then, the vehicle speed is calculated from the rotation speed of the wheels that are not the driving wheels. The steering angle sensor 49 reads the steering angle of the front wheels. Then, the lateral acceleration is calculated from the vehicle speed and the steering angle. When the lateral acceleration is a predetermined value, for example, 0.30 G to 0.35 G or more, the differential control is canceled. That is, the air in the air cylinder 27 is opened and discharged by opening the solenoid valve 40, so that the friction plate 2
The frictional connection between 9 and 30 is released.

As described above, in the limited slip differential according to the present embodiment, the operation area is set in the area shown in FIG. 3, and the operation of the limited slip differential is canceled in an area outside the area. When the limited slip differential is actuated, the traction force acts on the tires of the wheels, and the straightness in the normal steering range is improved, but the cornering force of the tires of the wheels is relatively reduced. Therefore, the stability limit area at the time of turning decreases.

Such a decrease in the stability limit region is explained by the following phenomenon. When the vehicle turns, the drive wheel on the turning center side floats with a lateral force and idles. Therefore, when the differential limitation by the limited slip differential is not performed, the driving force is not applied to the driving wheel on the opposite side, and the traction force is eliminated or reduced. On the other hand, when the limited slip differential is activated, a tractive force is generated. However, at this time, since the front wheels are steered toward the turning center, the lateral force increases. Therefore, when the limited slip differential operates in a region beyond the normal steering range, there is a possibility that a side slip occurs. Therefore, in this embodiment, as shown in FIG. 2, the normal steering range, that is, the lateral acceleration is a predetermined value,
For example, in the case of 0.30G to 0.35G or more, the differential limitation of the limited slip differential is released, and the vehicle is surely prevented from skidding during turning. Therefore, it is possible to improve the straightness during high-speed running without lowering the stability limit.

When the lateral acceleration calculated by the computer 43 is equal to or less than a predetermined value, for example, 0.35 G, it is determined that the vehicle is in the normal steering range. In such a case, when it is determined from the difference between the rotational speeds of the left and right front wheels and the left and right rear wheels that slippage exists in the drive wheels, the differential lock is performed. That is, the electromagnetic valve 38 is opened by the computer 43 and compressed air is supplied to the air cylinder 27 to frictionally couple the friction plates 29 and 30 to each other. Then, the differential shown in FIG. 1 is completely locked, thereby preventing the wheels from slipping.

When the lateral speed is a predetermined value, for example, 35G or less, and there is no slip in the driving wheels, the differential pressure is controlled by controlling the operating pressure applied to the air cylinder 27 with reference to the map. I have. The map referred to by the computer 43 may be, for example, as shown in FIG. 3, in which a predetermined operating pressure is given according to the steering angle of the front wheels and the vehicle speed. 27 to be supplied. The operating pressure is controlled by a solenoid valve 38,
The operation is performed by 40. When the operating pressure to the cylinder 27 is increased, the solenoid valve 38 is opened.
On the other hand, when reducing the pressure in the cylinder 27, the electromagnetic valve 40 is opened to exhaust the compressed air. In this way, it is possible to limit the differential with the optimum operating pressure according to the running state of the vehicle.

In particular, the feature of the map shown in FIG. 3 is that the operating pressure becomes maximum when the steering angle is O at each vehicle speed, and the operating pressure gradually decreases in accordance with the increase in the steering angle. With such characteristics, both straight running stability and turning limit stability are achieved. As is apparent from the characteristics shown in FIG. 3, the operating pressure is changed according to the vehicle speed, and a relatively large operating pressure is applied when O is on the left side. This is to prevent the drive wheels from slipping at the time of starting. Further, the operating pressure is reduced at an extremely low speed, and the operating pressure is gradually increased as the vehicle speed increases. Therefore, the straightness during high-speed running is particularly improved.

〔The invention's effect〕

As described above, the present invention provides a calculating means for calculating a lateral acceleration applied to a vehicle from a vehicle speed and a steering angle of a front wheel,
Judging means for judging whether the lateral acceleration is in a normal steering range lower than a predetermined value at the vehicle speed based on the lateral acceleration and the vehicle speed obtained by the calculating means, Is canceled.

Therefore, according to the present invention, when the lateral acceleration exceeds the normal steering range lower than a preset value at the vehicle speed, the differential limitation of the limited slip differential is released, whereby the vehicle is turned during turning. Side slip is reliably prevented. Therefore, it is possible to improve the straightness during high-speed running without lowering the stability limit.

Another invention comprises a control means for controlling an operating pressure applied to an actuator of a limited slip differential according to a vehicle speed and a steering angle, wherein the control means prevents a drive wheel from slipping by limiting the differential when the vehicle speed is zero. In addition to increasing the operating pressure, the operating pressure is reduced at an extremely low speed, and the operating pressure is controlled to increase as the vehicle speed increases.

Therefore, according to the present invention, when the vehicle speed is 0, the operating pressure for preventing the slip of the drive wheels is applied by the differential limitation, so that the slip of the drive wheels at the time of starting is prevented. Also, since the operating pressure applied to the limited slip differential actuator at extremely low speeds is reduced, the function of the differential during turning is not reduced,
Thereby, the turning performance can be secured. In addition, since the operating pressure is increased as the vehicle speed increases, the straightness when traveling at high speeds is improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a control device for a limited slip differential according to one embodiment of the present invention, FIG. 2 is a flowchart showing a control operation, and FIG. 3 is a graph of a control map. The names of the main parts in the drawings are as follows. 16 Differential case 17 Side gear 27 Casing (air cylinder) 29, 30 Friction plate 38, 40 Solenoid valve 43 Controller (computer) 45 Wheel rotation sensor (front left) 46 Wheel Rotation sensor (front right) 47 Wheel rotation sensor (rear left) 48 Wheel rotation sensor (rear right 49) Steering angle sensor

Claims (2)

(57) [Claims] 1. A limited slip differential wherein a friction plate is provided between one side gear and a differential case, and the friction plate is connected by a cylinder constituting an actuator to limit a differential. Calculating means for calculating the lateral acceleration applied to the vehicle from the steering angle of the front wheels, and determining whether the lateral acceleration is lower than a preset value at the vehicle speed based on the lateral acceleration and the vehicle speed obtained by the calculating means. A control device for a limited slip differential, comprising: a judgment means for judging whether or not the operation is canceled when the vehicle goes beyond a normal steering range during a turn. 2. A limited slip differential in which a friction plate is provided between one side gear and a differential case, and the friction plate is connected by a cylinder constituting an actuator to limit the differential. Control means for controlling an operating pressure applied to an actuator of the limited slip differential according to a steering angle, wherein the control means controls an operating pressure for preventing a slip of a drive wheel by a differential limitation when a vehicle speed is zero. In addition, a control device for a limited slip differential, wherein the operating pressure is reduced at an extremely low speed and the operating pressure is increased as the vehicle speed increases.