JPH02261946A - Control device for limited slip differential - Google Patents

Abstract

PURPOSE:To have continuous change of the frictional bond force of a friction plate by connecting the disengage side chamber of a cylinder with a back pressure valve, and connecting the working side chamber between the pressure source for the working fluid through a pressure control valve and a selector valve, which uses the set pressure on the pressure control valve as a pilot pressure. CONSTITUTION:A back pressure valve 50 is connected with a low pressure side piping 36 leading to the disengage side chamber of an oil cylinder 27 while a selector valve 38 is installed between an oil pump 42 and a high pressure side piping 35 leading to the working side chamber, and a pressure control valve 49 is installed between these selector valve 38 and oil pump 42. This pressure control valve 49 is controlled by a controller 52 to feed the set pressure therein via No.1 pilot line 47 as pilot pressure for the selector valve 38. This enables setting of the differentially limited condition and disengaged condition, and the limit point where a friction plate encounters slippage can be adjusted as any desired.

Description

[Detailed description of the invention]

[Field of industrial application] The present invention relates to a limited slip differential control and device, and in particular, a friction plate is provided between one side gear and a differential case, and the friction plate is brought into a connected state by an actuator such as an oil cylinder. 111 l in a limited slip differential that limits the differential by
@ [Regarding. K Summary of the Invention] A chamber on the operating side of an oil cylinder that applies a force in the direction of frictional coupling to the friction plate of a limited slip differential is connected to a high pressure side piping, and the high pressure side piping is connected to the high pressure side piping via a switching valve. The chamber on the opposite side of the oil cylinder is connected to the back pressure valve that sets the release pressure via the low-pressure side piping, and the pressure between the oil pump and the switching valve is connected to the oil pump. A control valve is connected, and when the pressure set by the pressure control valve becomes high, the switching valve is switched to supply high pressure to the working side chamber of the oil cylinder through the high pressure side piping to bring the friction plate into a connected state, When the oil pump pressure is released to the reservoir by the pressure control valve, the switching valve is switched in the opposite direction, and the oil in the chamber on the operating side of the oil cylinder is discharged to the reservoir side, and the release pressure set by the back pressure valve is The oil is supplied to a chamber on the opposite side of the oil cylinder to actively release the friction plates.

[Prior art 1] When a car turns, the outer wheels travel a longer distance than the inner wheels. In this way, in order to absorb the difference in rotation speed between the left and right wheels, especially the drive wheels, when turning, a differential is interposed between the left and right drive shafts. Depending on the difference in resistance applied to the drive wheels, the rotation of the propeller shaft is automatically transmitted to the left and right wheels at different rates, allowing the vehicle to turn without straining each part. However, if such a differential is installed, if one wheel falls into mud or on a snowy road, etc. ! When driving on a road surface with a low coefficient of friction, the wheels will slip. In other words, the differential impairs the starting performance and running performance on a road surface with a low H-friction coefficient. In order to eliminate these drawbacks, a differential lock device or a limited slip differential is installed on the differential. K Problems to be Solved by the Invention] A differential lock device or a limited slip differential suppresses the function of a differential and transmits the rotation of the propeller shaft equally to the left and right drive wheels. Therefore, when only one drive wheel slips, such a device can improve starting performance. Furthermore, if the limited slip differential is activated when driving at high speeds, the straight-line performance of the vehicle will be improved. However, if you drive with the limited slip differential locked, tire wear will be significant. Therefore, it is necessary to limit the differential movement of the differential depending on the slip state of the drive wheels or the running state of the vehicle. That is, it is preferable to continuously vary the frictional coupling force of the Ifl friction plate for limiting differential movement. The present invention has been made in view of these problems, and an object of the present invention is to provide a control device for a limited slip differential that continuously changes the friction bonding force of the friction plates. It is something. Means for Solving Problem K] The present invention provides a friction plate between one side gear and a differential case, and limits the differential by connecting the friction plate with a cylinder constituting an actuator. In the limited slip differential, the chamber on the actuating side of the cylinder is connected to a pressure source of the working fluid via a switching valve, and the chamber on the releasing side of the cylinder is connected to a back pressure valve, and the chamber on the actuating side of the cylinder is connected to a back pressure valve. A pressure control valve is connected between the switching valve and the switching valve, and the pressure set by the pressure control valve is supplied to the switching valve as pilot pressure. 1. Accordingly, the pressure of the working fluid supplied to the working side chamber of the cylinder through the switching valve can be arbitrarily set by the pressure control valve. Therefore, it is possible to continuously change the frictional coupling force of the friction plates for limiting the differential by using the above pressure, and the differential movement of the differential can be controlled by partially slipping the friction plates depending on the driving condition of the vehicle. be able to limit. Embodiment FIG. 1 shows a limited slip differential according to an embodiment of the present invention, and this limited slip differential includes a drive pinion 10. As shown in FIG. The drive pinion 10 is connected to the tip of the propeller shaft, and is rotatably supported by the housing 11 by front and rear bearings 12,13. The drive pinion 10 is adapted to mesh with the ring gear 14. Ring gear 14 is fixed to differential case 16 with bolts 15. Inside the differential case 16 are a pair of left and right side gears 17.18.
are arranged. These side gears 17, 18 are fixed to the drive shaft 19, 20, respectively, and are connected to the drive shaft 1.
Torque is transmitted to the drive wheels via 9.20. In addition, there are four differential binions 2 inside the differential case 16.
1.22 is arranged. These definions 21.
22 is connected to the differential case 1 via a cross-shaped spider 23.
6 is supported. The differential case 16 is rotatably supported by bearings 24 on both sides about the axis of the drive shaft 19, 20. A casing 27 constituting an oil cylinder is attached to the left side of the differential case 16 in FIG. As shown in an enlarged view in FIG. 2, a piston 28 is disposed within the oil cylinder 27 and is configured to press against friction plates 29 and 30 that are stacked on top of each other. Friction plate 2 of friction plates 29, 30 in casing 27
9 is the spline 3 of the casing 27 on the outer peripheral side.
At the same time, the center portion of the friction plate 30 is engaged with the spline 32 of the side gear A717. The oil cylinder 27 for frictionally connecting the FJ friction plates 29 and 30 to each other has a high pressure side pipe 35 and a low pressure side pipe 36.
are connected. The high-pressure side pipe 35 supplies hydraulic pressure to the chamber on the left side of the piston 28 shown in FIG. On the other hand, the low pressure side piping 36 is the oil passage 3
7 supplies hydraulic pressure to the chamber on the right side of the piston 28. The high pressure side pipe 35 is connected to a switching valve 38 shown in FIG. The switching valve 38 includes a spool 39 and is connected to an oil pump 42 via a check valve 40 and a filter 41. Note that a relief valve 43 is connected to the discharge side of the oil pump 42. Further, a reservoir 44 is provided on the suction side of the oil pump 42. The chambers on both sides of the spool 39 of the switching valve 38 are connected to a first pilot line 47 and a second pilot line 48, respectively. Further, a pressure control valve 49 is connected between the discharge side of the oil pump 42 and the inlet side of the switching valve 38. This pressure control valve 49 is composed of a duty control valve. On the other hand, a back pressure valve 50 is connected to the tip side of the low pressure side piping 36, and this back pressure valve 50 causes the oil cylinder 2
The release pressure to be applied to 7 is set. Further, the pressure in the low pressure side pipe 36 is detected by a pressure sensor 51. The pressure control valve 49 is controlled by a controller 52, and has a pressure sensor 51 on its input side.
Additionally, four rotation detection sensors 53 to 56 are connected. These rotation detection sensors 53 to 56 are adapted to detect the rotation speeds of the left front wheel, right front wheel, left rear wheel, and right short wheel, respectively. Further, a manual switch 57 and a brake switch 58 are connected to the controller 52. Further, an operation display device 59 and a failure display device 60 are connected to the output side of the controller 52. In the above configuration, if the air cylinder 27 having the friction plates 29, 30 is removed from the limited slip differential shown in FIG. 1, it functions 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 differential case 16 to which the ring gear 14 is fixed rotates. Since four differential binions 21.22 are attached to the differential case 16 via spiders 23, if the resistance of the left and right drive wheels is the same, the differential binions 21.2
2 rotates by connecting the left and right side gears 17 and 18. Therefore, in this case, torque is transmitted to the left and right drive wheels through the drive shafts 19, 20 at the same rotational speed. The rotation speed of the drive shaft at this time is equal to the rotation speed of the ring gear 14. On the other hand, if the resistance of one of the drive wheels increases, the side gear 17 connected to this drive wheel becomes difficult to rotate, so the differential gears 21 and 22 rotate together with the differential case 16 while shifting over the side gear 17. Therefore, in this case, the rotation accompanying the revolution of the differential case 16 and the rotation accompanying the rotation of the differential binion 21, 22 are caused by the rotation of the side gear 1.
8 to the drive shaft 20, and the rotational speed of the drive wheel with less resistance increases. In this way, when the vehicle turns, the difference in rotational speed is absorbed depending on the traveling distance of the left and right drive shafts. When the controller 52 switches the switching valve 38 via the pressure control valve 49 to move the spool 39 to the right as shown in FIG. 2
7, causing the piston 28 to be pushed to the right in FIGS. 1 and 2. The piston 28 then connects the friction plates 29, 30 to each other FflFM. The M swing plate 29 is attached to the spline 31 on the case 27 side, l! The I friction plate 30 is a spline 32 around the outer circumference of the boss of the side gear 17.
When the friction plates 29 and 30 are frictionally coupled to each other, the side gear 17 is engaged with the friction plates 29 and 30, respectively.
．． 30 and the casing 27, it is mechanically coupled to the differential case 16. Then differential case 16
The differential gear 2 supported via the spider 23
1.22 and the side gear 17 is no longer permissible, resulting in a limited differential condition. As a result, the original function of the differential is limited, and it only has the function of transmitting approximately equal rotational speed to the left and right drive shafts. Next, the operation for controlling the hydraulic pressure applied to the piston 28 of the oil cylinder 27 will be explained. If the controller 52 detects a slip of the drive wheel from the difference in the rotational speed of the left front wheel, right front wheel, left rear wheel, and right rear wheel detected by the four rotation sensors 53 to 56, the pressure control valve 4 The differential is limited by the oil cylinder 27 via the two. That is, the controller 52 closes the four pressure control valves. Then, a high pressure, for example, 23 kg/d, is applied to the left side of the spool 39 of the switching valve 38 through the first pilot line 47, which is set by the four pressure control valves. Furthermore, the one-way valve 4 is controlled by the discharge pressure of the oil pump 42.
0 is opened, and high pressure is similarly applied to the spool 39 in its middle portion. Therefore, the spool 39 moves to the right against the low pressure applied through the second pilot line 48 and the release pressure set by the back pressure valve 50, and the discharge side of the oil pump 42 and the high pressure side line 35 are moved. It will be communicated. Therefore, high pressure oil is supplied to the left chamber of the piston 28 shown in FIG.
0 to each other. This creates a differential limiting condition. When the four rotation detection sensors 53 to 56 detect that the slip of the drive wheels has been released, the controller 52 opens the pressure control valve 49. The pressure on the discharge side of the oil pump 42 then escapes to the reservoir 44 through the pressure control valve 49. Therefore, the check valve 40 connected to this pressure control valve 49 is closed. Also, since the pressure applied to the left side of the three spools through the first pilot line 47 also escapes to the reservoir 44 through the pressure control valve 49, the pressure applied to the left side of the spool 39 is equal to the back pressure set by the back pressure valve 50, i.e. For example, it will be lower than 3 kg/cd. On the other hand, on the right side of the three spools there is a pressure set by the back pressure valve 50 through the second pilot line 48, i.e. for example 3 kg.
A release pressure of /cj is supplied, and the spool 39
is shifted to the left in FIG. Therefore, the high pressure side pipe 35 is communicated with the reservoir 44, and the oil in the chamber on the left side of the piston 28 of the cylinder 27 escapes to the reservoir 44 side. Moreover, the release pressure set by the back pressure valve 50 is always supplied to the chamber on the right side of the piston 28 of the oil cylinder 27 shown in FIG. Move to I! J rubbing board 2
Actively move away from 30. Therefore, the friction plate 29.3
0 frictional coupling will be reliably released. Moreover, the pressure control valve 49 controlled by the controller 52 is composed of a duty control valve, and a pulsed drive voltage is applied by a drive circuit. By changing the pulse width and frequency, substantially the same control as arbitrarily setting the throttle gap of the pressure control valve 49 is performed. Therefore, this pressure control valve 49 makes it possible to continuously change the operating pressure applied to the oil cylinder 27 through the high pressure side pipe 35. This makes it possible to arbitrarily change the force with which the piston 28 presses the AM plate 29, 30, and thereby allows the limit value at which the limited slip differential slips to be arbitrarily set. . Therefore 4
By performing the above control in accordance with the detection of the rotation difference between the left front wheel, right front wheel, left rear wheel, and right rear wheel detected by the four rotation detection sensors 53 to 56, when changing lanes when driving at high speed, yaw and rolling of the vehicle can be reduced. In addition, handling stability during high-speed driving will be significantly improved. Further, since the controller 52 that controls the hydraulic control device is provided with a manual switch 57, this switch 5
controller 5 by supplying a signal by 7
2 and the pressure control valve 49, it becomes possible to arbitrarily limit the differential differential. Further, since the brake switch 58 is connected to the controller 52, by releasing the differential lock during rolling motion, it is possible to use the anti-skid brake device. That is, since the anti-skid brake device needs to separately control the rotation of the left and right wheels, the differential lock may be released by the controller 52 in response to the detection by the switch 58. Further, the operating state of the limited slip differential and its failure state are displayed by an operation display device 59 and a failure display I position 60 connected to the controller 52. [Effects of the Invention] As described above, the present invention connects the working side chamber of the cylinder constituting the actuator to the pressure source of the working fluid via the switching valve, and connects the releasing side chamber of the cylinder to the back pressure valve. Moreover, a pressure control valve is connected between the pressure source and the switching valve, and the pressure set by the pressure control valve is supplied to the switching valve as pilot pressure. Therefore, according to such a configuration, it is possible to set the differential restriction state and the differential restriction release state by the pressure control valve, and by continuously changing the operating pressure applied to the cylinder by the pressure control valve. , it becomes possible to arbitrarily adjust the operating limit of the limited slip differential, that is, the limit point at which the friction plate slips.

[Brief explanation of drawings]

FIG. 1 is a piping diagram showing a hydraulic control device for a limited slip differential according to an embodiment of the present invention, and FIG. 2 is an enlarged sectional view of essential parts of the limited slip differential. The names of the main parts in the drawings are as follows. 16...Differential case 17...Side gear 27...Casing (oil cylinder) 28...
... Piston 29.30 ... Friction plate 31.32 ... Spline 35 ... High pressure side piping 36 ... Low pressure side piping 37 ... Oil passage 38 ... Switching Valve 42... Oil pump 47... First pilot line 48... Second pilot line 49... Pressure control valve (duty control valve) 50.
・・・Back pressure valve

Claims (1)

[Claims] 1. A limited slip differential in which a friction plate is provided between one of the side gears and the differential case, and differential movement is limited by bringing the friction plate into a connected state by a cylinder constituting an actuator. A chamber on the actuating side of the cylinder is connected to a pressure source of working fluid via a switching valve, and a chamber on the releasing side of the cylinder is connected to a back pressure valve, and the pressure is controlled between the pressure source and the switching valve. A control device for a limited slip differential, characterized in that a valve is connected to the pressure control valve, and the pressure set by the pressure control valve is supplied to the switching valve as pilot pressure.