JP2622865B2 - Limited slip differential - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a limited slip differential, in particular, providing a friction plate between one side gear and a differential case, and connecting the friction plate by an air cylinder. The present invention relates to a limited slip differential in which differential limiting is performed by using a differential slip differential.

[Summary of the Invention]

A plurality of solenoid valves are provided in parallel with one another to supply air to the air cylinder of the limited slip differential, and at least one of these solenoid valves is combined with a pressure reducing valve to provide a different pressure through each solenoid valve. Air is supplied to the air cylinder and the pressure applied to the air cylinder is changed stepwise to generate the optimal frictional force on the friction plate according to the road surface condition and running condition, and the effect of the limited slip differential Is drawn out sufficiently.

[Conventional technology]

Generally, a differential (differential gear device) is interposed between a propeller shaft and a drive shaft of an automobile, and a difference in travel distance between left and right drive wheels during turning is adjusted by a differential device to provide a smooth operation. It allows the vehicle to run and prevents tire wear. However, when such a differential is provided, when one of the wheels falls into mud or snow, only the wheel slips and the other wheel does not rotate. Differentials also tend to reduce the straight running stability of vehicles.

In order to solve such disadvantages of the differential, a limited slip differential has been used. Limited slip differentials, for example, when one wheel falls into a mud, etc., differentially limit the differential to transmit driving force to the other wheel, so as to ensure escape from mud. It is. In addition, by performing such a differential limitation at the time of high-speed traveling, straight running stability is improved. In addition, skidding of the vehicle during braking is prevented.

[Problems to be solved by the invention]

However, in the conventional limited slip differential, the pressure applied to the air cylinder when limiting the differential is set to a constant value, so that the same torque is applied both when the vehicle is running at high speed and when it is running at low speed. This causes the friction plate to slip. If the set torque at which the differential slips is high, tire wear becomes severe. If the set torque is low, the torque applied to the other wheel when the wheel escapes from the mud becomes insufficient. That is, the conventional limited slip differential has a disadvantage that it cannot always be controlled in an optimum state according to the running state of the vehicle.

The present invention has been made in view of such a problem, and while improving the straight running stability while reducing tire wear as much as possible at the time of vehicle speed running, when the wheel escapes muddy etc at low speed. It is an object of the present invention to provide a limited slip differential capable of applying a full torque so as to apply a large force close to a differential lock.

[Means for solving the problem]

The present invention provides an apparatus in which a friction plate is provided between one side gear and a differential case, and a differential restriction is performed by connecting the friction plate by a cylinder. A pressure source, a pressure changing means comprising a combination of an electromagnetic valve and a pressure reducing valve connected between the pressure source and the cylinder, and a pressure changing means for setting the pressure of the pressure source to a plurality of different pressures; An operation switch for switching between an active state and an inactive state; vehicle speed detecting means for detecting a vehicle speed; and when the vehicle is running at a low speed and the operation switch is ON, the high pressure obtained by the pressure changing means is applied to the cylinder. The low pressure obtained by the pressure changing means when the vehicle is running at a low speed and the operation switch is OFF and at a medium speed. And a solenoid valve control means for controlling the opening and closing of the solenoid valve so that an intermediate pressure is supplied to the cylinder when the cylinder is operated at a high speed.

[Action]

The vehicle speed is detected by the vehicle speed detecting means. When the vehicle is running at low speed and the differential switch of the limited slip differential is ON, the high pressure obtained by the pressure changing means is supplied to the cylinder, and the set torque of the limited slip differential increases. On the other hand, when the vehicle is traveling at a low speed and the differential switch is OFF or at a medium speed, the low pressure obtained by the pressure changing means is supplied to the cylinder so that a low set torque is given to the limited slip differential. Become. In the case of high speed, an intermediate pressure is supplied to the cylinder, and the set torque of the limited slip differential also has an intermediate value.

〔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,
In addition, the housing 11 is rotatably supported via bearings 12 and 13. The drive pinion 10 is designed to mesh with the ring gear 14. The ring gear 14 is fixed to a differential case 16 via a bolt 15.

Left and right side gears 17 and 18 are arranged in the differential case 16. These side gears 17 and 18 are connected to drive wheels via drive shafts 19 and 20, respectively. In the differential case 16, there are four differential pinions 21, 22.
Are arranged so as to mesh with the side gears 17 and 18.
The differential pinions 21 and 22 are supported by the differential case 16 via a cross-shaped spider 23. The differential case 16 is connected to the housing 11 via left and right bearings 24.
It is supported rotatably.

A casing 27 constituting an air cylinder is attached to the left side of the differential case 16 in FIG. A piston 28 is slidably held in the air cylinder 27 at the base end side of the casing 27. A plurality of friction plates 29 and 30 are arranged in the casing 27 so as to be pressed by the piston 28. The outer peripheral portion of the friction plate 29 engages with a spline of the casing 27. On the other hand, the friction plate 30 has a portion on the center side engaged with the outer peripheral surface of the boss of the side gear 17.

The air cylinder 27 is composed of an air tank 33 and a first solenoid valve.
The connection is made via a second solenoid valve 35 and the second solenoid valve 35. These solenoid valves 34 and 35 are connected in parallel with each other, and a pressure reducing valve 36 is connected to the solenoid valve 35 in series. Further, another pressure reducing valve 37 is connected in parallel to two pipes provided with the electromagnetic valves 34 and 35, respectively. The two solenoid valves 34 and 35 are controlled by an electronic control unit 38 composed of a microcomputer. A vehicle speed sensor 39 and an LSD switch 40 are connected to the input side of the control device 38. LSD is an abbreviation for Limited Slip Differential.

In the above-described configuration, when the friction plates 29 and 30 and the air cylinder 27 are not provided, the differential shown in FIG. 1 functions in the same manner as a normal differential. That is, the torque applied to the drive pinion 10 via the propeller shaft is transmitted to the ring gear 14, and the differential case including the ring gear 14
16 rotates about the axis of the drive shafts 19 and 20. If the resistances of the left and right wheels are the same, the rotation of the differential case 16 is transmitted to the side gears 17 and 18 via the differential pinions 21 and 22 and transmitted to the left and right drive shafts 19 and 20. In this case, the left and right wheels are rotated at the same rotation speed.

On the other hand, if the resistance of one of the wheels increases, for example, during turning, the differential pinions 21 and 22 roll on the side gear 17 connected to the wheel with the higher resistance, whereby the other side gear 18 Will increase accordingly. As a result, the number of rotations of the wheel having small resistance increases, and the original function as the differential gear device is exhibited.

Next, open one of the solenoid valves 34 and 35 to open the air cylinder.
When compressed air is supplied to the air tank 27 from the air tank 33, the piston
28 presses the friction plates 29, 30 and frictionally connects the friction plates 29, 30 to each other. And friction plates 29, 30
Are connected to the splines 31, 32 of the casing 27 and the side gear 17, respectively, so that the friction plate
The side gear 17 is frictionally coupled to the differential case 16 via 29 and 30. Moreover, since the differential pinions 21 and 22 are supported by the differential case 16 via the spider 23, the relative rotation between the side gears 17 and 18 and the differential pinions 21 and 22 is suppressed by the frictional resistance between the friction plates 29 and 30. As a result, the differential limiting state is established. Therefore drive pinion 10
The rotation of the ring gear 14, differential case 16 and side gear
It is transmitted equally to the left and right drive wheels 19 and 20 through 17 and 18.

The torque when the friction plates 29 and 30 cause slippage can be adjusted by the air pressure applied to the piston 28 of the air cylinder 27, and is the highest when the vehicle is traveling at a low speed of 0 to 20 km / h. Slip with torque. In this case, open the solenoid valve 34 and, for example,
Supply pressure of cm ² . That is, compressed air is supplied from the air tank 33 to the air cylinder 27 through the three-way joints 42 and 43, the first solenoid valve 34, the double check valves 44 and 45, and the air passage 41 of the housing 11. The double check valves 44 and 45 allow the higher pressure of the left and right pressures to pass therethrough. Therefore, in this case, a high pressure of about 8 kg / cm ² in the air tank 33 is supplied, and the set torque of the limited slip differential becomes very high.

As shown in FIG. 2, the first solenoid valve 34 is opened when the vehicle is traveling at low speed and the LSD switch 40 is ON as described above. That is, when one wheel falls into mud or the like while traveling at low speed, or when traveling on a snowy road, the first solenoid valve 34
By turning ON, it is possible to apply a high set torque to the limited slip differential, thereby increasing the ability to travel on a rough road at low speeds.

On the other hand, when the vehicle is traveling at a high speed of, for example, 70 km / h or more, the second solenoid valve 35 is opened as shown in FIG. Then, from the air tank 33, the three-way joints 42 and 43, the pressure reducing valve
36, solenoid valve 35, double check valve 44, 45, air passage
Air is supplied to the air cylinder 27 through 41. At this time, since air having a pressure of 4 to 5 kg / cm ² reduced in pressure by the pressure reducing valve 36 is supplied, a slightly weaker set torque is applied. Therefore, at the time of high-speed running, it is possible to apply a torque to the limited slip differential while reducing the wear of the tire as much as possible and improving the straight running stability.

Next, the vehicle is traveling at low speed, and the LSD switch 40 is turned off.
And / or the vehicle is at medium speed, e.g. 20-70 km / h
When traveling with two solenoid valves as shown in FIG.
Both 34 and 35 are OFF. In such a case, compressed air is supplied from the air tank 33 to the air cylinder 27 through the three-way joint 42, the pressure reducing valve 37, the double check valve 45, and the air passage 41. That is, in this case, a low pressure of 1-2 kg / cm ² sufficiently reduced by the pressure reducing valve 37 is supplied into the differential, thereby giving a low set torque. In other words, even if the limited slip differential is turned off, the friction plates 29 and 30 perform differential limiting with a weak frictional coupling force, and improve running performance when traveling on a low friction coefficient road surface at medium speed or low speed. Becomes possible.

〔The invention's effect〕

As described above, according to the present invention, the vehicle speed is detected by the vehicle speed detecting means, and the high pressure obtained by the pressure changing means is supplied to the cylinder when the vehicle is running at a low speed and the operation switch of the limited slip differential is ON. Then, the set torque of the limited slip differential is increased, and when the vehicle is running at a low speed and the operation switch is OFF or at a medium speed, the low pressure obtained by the pressure changing means is supplied to the cylinder. In this case, the set torque of the limited slip differential is reduced, and at a high speed, an intermediate pressure is supplied to the cylinder to set the set torque of the limited slip differential to an intermediate value. That is, the set torque at which the limited slip differential causes a slip is changed according to the vehicle speed.

Therefore, the torque at which the limited slip differential slips is changed in accordance with the vehicle speed, so that it is possible to improve the straight running stability while reducing tire wear as much as possible at high speeds, and to reduce muddy at low speeds. At the time of escape, etc., it is possible to output a force close to the differential lock by turning on the operation switch. This makes it possible to sufficiently bring out the performance of the limited slip differential.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a limited slip differential according to one embodiment of the present invention, and FIG. 2 is a flowchart showing the operation 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 (air cylinder) 28 Piston 29, 30 Friction plate 34 First solenoid valve 35 Second solenoid valve 36 Pressure reducing valve

Claims (1)

(57) [Claims] 1. An apparatus in which a friction plate is provided between one side gear and a differential case, and the friction plate is connected by a cylinder to limit a differential, wherein a differential supplied to the cylinder is provided. A pressure source for a fluid, a pressure changing unit configured to combine a solenoid valve and a pressure reducing valve connected between the pressure source and the cylinder, and changing the pressure of the pressure source to a plurality of different pressures; An operation switch for switching the slip differential between an operating state and an inoperative state; vehicle speed detecting means for detecting a vehicle speed; and a high pressure obtained by the pressure changing means when the vehicle is running at low speed and the operation switch is ON. The low pressure supplied to the cylinder and obtained by the pressure changing means when the vehicle is running at a low speed and the operation switch is OFF and at a medium speed. Is supplied to the cylinder,
And a solenoid valve control means for controlling the opening and closing of the solenoid valve so that an intermediate pressure is supplied to the cylinder at a high speed.