JPH05223134A - Driving force transmission device - Google Patents

Abstract

PURPOSE:To avoid jumping-out from turning at the time of cornering at a medium or high speed, in a driving force transmission device provided with a lock-up mechanism, without any sacrifice of escape performance at the time of a wheel out of place. CONSTITUTION:A cam engagement element 29 which engages with a cam surface 21A in the circumferential direction installed on the end wall of a housing 21 is mounted in a housing 21 so as to generate thrust which presses a multiple disk clutch 25 by relative rotation to the housing 21. This is a driving force transmission device where the energizing force of the spring 12 changes according to vehicle speed by engaging a spring 12 which energizes the cam engagement element 29 in the direction where it is engaged with the cam surface 21A of the housing 21 with the tapered surface 102 of a weight 10 energized inward by a coil spring 11 which is placed on the outer periphery 212 of a central protruding part 211 in the housing 21 and is inserted in a space to the inner periphery wall 291 of the cam engagement element 29.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving force transmission device used in a four-wheel drive vehicle.

[0002]

2. Description of the Related Art In a driving force transmission device having a multi-plate clutch, when the multi-plate clutch has a sliding friction for a long period of time, such as when a vehicle is derailed, friction heat is generated in the multi-plate clutch to cause a clutch plate. May be damaged. As a means for solving such a problem, a driving force transmission device provided with a lock-up mechanism using a cam is conventionally known, as described in JP-A-1-93631.

[0003]

However, in the above-mentioned known driving force transmitting device, since the differential rotation speed of the lockup is constant, when cornering at a medium speed, for example, which belongs to general running, The vehicle may be locked up, and the vehicle may suddenly jump out of the turn.
In order to avoid such a situation, if the differential rotation speed of the lockup is increased, the most important advantage of having the lockup is to deteriorate the escape performance at the time of derailing.

Therefore, the present inventors have focused on the basic idea of changing the lockup differential rotation speed according to the vehicle speed, and as a result of repeated research and development, the sacrifice of the escape performance at the time of derailing. In other words, the present invention has been achieved which achieves the object of avoiding the outward protrusion of the turning when cornering at medium and high speeds.

[0005]

According to the present invention, there is provided a driving force transmitting device, wherein a cam engaging body which engages with a cam surface in a circumferential direction provided on an end wall of the housing is rotated by relative rotation with the housing. The multi-plate clutch is mounted so as to generate a thrust force, a plurality of outer plates of the multi-plate clutch are respectively engaged with the cam engagement body in the rotational direction, and the multi-plate clutch is arranged between the outer plates. Biasing force control means for engaging a plurality of inner plates of the plate clutch with the rotary shaft, respectively, and changing the biasing force of a spring for biasing the cam engagement body in the direction of engaging the cam surface of the housing according to the vehicle speed. Is provided.

[0006]

With the above structure, when the relative rotational speed difference between the housing and the rotary shaft increases, the frictional engagement force of the multi-plate clutch increases, and the transmission torque exceeds the bias set by the spring, the clutch engagement body is activated. Rotates relative to the housing to generate a thrust force that presses the multi-plate clutch by its cam action. As a result, the outer plate and the inner plate are almost directly connected to each other, and the transmission torque by the multi-plate clutch rapidly increases to facilitate escape from the mud or the like. Since the biasing force control means controls the biasing force of the spring, that is, the bias in accordance with the vehicle speed, the bias increases as the vehicle speed increases, and the differential rotation speed (lock point) that locks up increases according to the vehicle speed. If you do not exceed the points, you will not be locked up.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. (Structure of First Embodiment) In FIG. 1, reference numeral 21 denotes a housing coupled to one driven shaft of two relatively rotatable two shafts (front and rear wheel shafts), and this housing 21 has the other two drive shafts. A rotary shaft 22 coupled to the shaft is rotatably supported. Inside the housing 21, the housing 21 and the rotary shaft 2
Hydraulic pressure generating means 2 for generating hydraulic pressure according to differential rotation with respect to 2
3, a piston 24 to which hydraulic pressure generated by the hydraulic pressure generating means 23 is applied, and a multi-plate clutch 25 frictionally engaged by the pressing force of the piston 24 and transmitting torque between the two shafts. ing.

A cylindrical hollow chamber 27 is formed in the housing 21, and the open end of the hollow chamber 27 is closed by an end cover 28 fixed to the housing 21. In the hollow chamber 27, a cylindrical cam engagement body 29 is mounted concentrically with the rotary shaft 22 so as to be rotatable and slidable relative to the housing 21. As shown in FIG.
As shown in FIG. 5, a wavy cam portion 29A is formed on the end surface in the circumferential direction, and a plurality of engagement grooves 29B are formed in the cylindrical portion at equal angular intervals on the circumference.

A corrugated cam surface 21A is circumferentially formed on the bottom wall of the hollow chamber 27, that is, the end wall of the housing 21, and a cam portion formed on the end surface of the cam engagement body 29 is formed on the cam surface 21A. 29A is engaged.

As shown in FIGS. 1 to 3, an annular snap ring 13 is fixed near the right end of the outer peripheral wall 212 of the central projecting portion 211 of the housing 21, and is vertically attached to one surface of the snap ring 13. Has a flat surface 101,
The other surface has a tapered surface 102, and the weight 10 is gradually thinned toward the outer side in the radial direction.
The weight 10 is placed on the concave portion 1 of the outer peripheral floor of the weight 10.
03 and the inner peripheral surface 291 of the cam engaging body 29, the coil spring 11 is inserted, and the end 292 of the inner peripheral surface 291 of the cam engaging body 29 and the tapered surface 10 of the weight 10 are inserted.
An annular disc spring 12 is inserted between the two and the above, and the biasing force control means is constituted by the above. The disc spring 12
The cam portion 29A of the normal cam engagement body 29 is engaged with the cam surface 21A by the spring force of the above. However, when the differential rotation speed increases and the transmission torque increases, the cam portion 29A rotates on the housing 21 that rotates corresponding to the vehicle speed. The weight 10 moves radially outwardly against the spring force of the coil spring 11 by the centrifugal force, and the end portion 292 of the inner peripheral surface 291 of the cam engagement body 29 is moved.
The locking position of the disc spring 12 with the taper surface 102 is relatively lowered and engages with a thick portion, and the disc spring 12 is deformed, so that the biasing force (bias force) of the disc spring 12 is increased. The load) is controlled according to the vehicle speed. Therefore, in FIG. 5, the transmission torque increases as the differential rotation speed increases as indicated by the broken line, and when the bias of the disc spring 12 controlled according to the vehicle speed or more is reached, the cam engagement body 29 moves to the housing 21. It rotates relative to it and slides against the spring force of the disc spring 12 to generate a thrust force for pressing the multi-plate clutch 25.

A piston 24 is fitted in the hollow chamber 27 so that it can slide only. A cylindrical space portion 40 restricted in the axial direction is formed between the piston 24 and the end cover 28, and a rotor 41 having a wall thickness slightly smaller than the axial dimension thereof can be slidably contacted with the space portion 40. It is stored in. As shown in FIG. 4, the rotor 41 has a plurality of substantially L-shaped blades 42 having a center portion spline-engaged with the outer circumference of the rotary shaft 22 and extending in the radial direction and the circumferential direction. Thereby, the space 40 is
A plurality of blades 42 divide the circumference into a plurality of pressure chambers, and a high-viscosity oil 4 such as silicon oil is provided in each of the pressure chambers.
4 is filled. Then, the cylindrical space portion 4 described above
The rotor 41 having the blade 42 housed in 0 and the high-viscosity oil 44 constitute the hydraulic pressure generating means 23.

In the hollow chamber 27, the cam engaging body 29 is provided.
A plurality of outer plates 37 and inner plates 38 constituting the multi-plate clutch 25 are alternately arranged between the piston 24 and the piston 24, and the outer plates 37 are respectively engaged with the engaging grooves 29B of the cam engaging body 29 to rotate. The inner plates 38 are spline-engaged with the outer circumference of the rotary shaft 22, respectively.

(Operation / Effect of First Embodiment) In the above structure, when the housing 21 and the rotary shaft 22 rotate relative to each other and the rotor 41 rotates relative to each other within the housing 21, the high viscosity filled in the space 40 is obtained. The oil 44 is forcibly moved by the blade 42 between the two surfaces that are close to each other at a flow velocity according to the rotational speed difference. At this time, the housing 21 and the piston 24
Due to viscous friction with both end walls of the rotor 41
An internal pressure proportional to the rotation speed of is generated. That is, for example, when the blade 42 rotates in the arrow direction with respect to the housing 21, this internal pressure is applied to the two adjacent blades 4.
The lowest on the changing blade side of the pressure chamber surrounded by 2,
The pressure distribution becomes highest on the subsequent blade side, and a pressure proportional to the rotation speed of the blade 42 is generated in the pressure chamber, and this pressure acts on the piston 24 to press the multi-plate clutch 25.

Therefore, the plurality of outer plates 37 and the inner plate 38 are frictionally engaged with each other by the pressing force corresponding to the oil pressure acting on the piston 24, and the torque is generated between the housing 21 and the rotary shaft 22 via the multi-plate clutch 25. Is transmitted, 4
Wheel drive state. By the way, when cornering at medium and high speeds, the housing 21 rotates according to the medium and high speeds of the vehicle, so that the weight 10 moves outwardly against the spring force of the coil spring 11 by the centrifugal force, and the weight of the disc spring 12 is increased. In order to increase the bias load, the lockup state does not occur unless the transmission torque becomes equal to or higher than the bias controlled for the disc spring 12 (the differential rotation reaches NV in FIG. 5). A situation in which the vehicle is in a lockup state (shown by the solid line in FIG. 5) during high-speed cornering and the vehicle jumps out of the turn is avoided.

On the other hand, as when escaping from a muddy area,
When the vehicle speed is low, a large centrifugal force does not act on the weight 10, and the bias load of the disc spring 12 is small. Therefore, when the transmission torque becomes equal to or larger than the bias load of the disc spring 12, the cam engagement body 29 is moved relative to the housing 21. As a result, the cam engagement body 29 is rotated by the cam action and the spring 30 is rotated.
Axial thrust force is generated that pushes the multi-plate clutch 25 by displacing it. As a result, the outer plate 37 and the inner plate 38 are almost directly connected to each other, and the multi-plate clutch 2
5, the transmission torque rapidly increases at a predetermined differential rotation N1 as shown by the torque transmission characteristic shown by the solid line in FIG. 5, facilitating escape from the mud or the like.

In this case, since the plurality of outer plates 37 of the multi-plate clutch 25 are engaged with the cam engaging body 29, all friction torque acting on the multi-plate clutch 25 is transmitted to the cam portion 29A of the cam engaging body 29. As a result, torque is not concentrated on the joint surface between the multi-plate clutch 25 and the cam engagement body 29.

(Second Embodiment) The second embodiment is different from the first embodiment in that the tapered surface 102 is formed on the weight 10.
As shown in FIG. 6, the main difference is that the weight 15 of the disc spring 14 has a tapered surface on its abutting surface 141.
Along with that, the outer periphery of the disc spring 14 is fixed to the inner peripheral surface 291 of the cam engaging body 29, the weight 15 has a rectangular cross section, and balls 152, 153 that are vertically rotatable are attached to the surface 151 that comes into contact with the snap ring 13. A large rotatable ball 155 is provided at the center of the surface 154 of the disc spring 14 facing the tapered surface 141 of the disc spring 14, and the large ball 155 is brought into contact with the ball 155. The weight 15 can be smoothly moved outward in the radial direction by the centrifugal force acting by rotating.

In the second embodiment having the above construction, when the vehicle speed of the vehicle is high, the weight 15 moves radially outward due to the above construction, and the tapered surface 141 is pressed and deformed leftward in FIG. Since the cam engagement body 29 is strongly urged from the spring 14 toward the cam surface of the housing 21 to increase the bias load, the same operational effect as that of the first embodiment is achieved, and the balls 152, 153, 155 provide centrifugal weight. It has the effect of smoothing the movement of 15.

[0019]

As described above, according to the present invention, the urging force of the spring for urging the cam engaging body in the direction of engaging the cam surface of the housing is controlled by the urging force control means according to the vehicle speed. There is an effect that the lock-up state at the time of cornering at medium and high speeds can be avoided, and a situation in which the vehicle jumps out of the turning can be avoided.

The above-mentioned embodiments are merely examples for the purpose of explanation, and the present invention is not limited to them. Modifications and additions can be made without departing from the technical idea described in the scope of claims. is there.

In the above-mentioned embodiments, the urging force control means is described as an example in which the urging force is controlled by utilizing the centrifugal force according to the vehicle speed, but the vehicle speed is detected and the electromagnetic force or the like is detected accordingly. In addition to controlling the biasing force by force, any one can be adopted as long as it has the same effect.

In the embodiment described above, the piston 24
The oil pressure acting on the was described with respect to an example in which high-viscosity oil is generated by forcibly moving by a blade.
Alternatively, a well-known differential pump may be used.

[Brief description of drawings]

FIG. 1 is a sectional view of a driving force transmission device showing an embodiment of the present invention.

FIG. 2 is a partially enlarged sectional view of FIG. 1 showing weights when a vehicle speed is low.

FIG. 3 is a partially enlarged sectional view of FIG. 1 showing a weight when a vehicle speed is high.

FIG. 4 is a cross-sectional view taken along the line AA of FIG.

FIG. 5 is a diagram showing a transmission torque characteristic with respect to differential rotation.

FIG. 6 is a cross-sectional view of a second embodiment device.

[Explanation of symbols]

 10, 15 Weight 11 Coil spring 12, 14 Disc spring 13 Snap ring 21 Rotating housing 21A Cam surface 22 Rotating shaft 23 Hydraulic pressure generating means 24 Piston 25 Multi-plate clutch 29 Cam engaging body 29A Cam part 29B Engaging groove 30 Spring 37 Outer plate 38 Inner plate 102, 141 Tapered surface

Claims (1)

[Claims] 1. A multi-plate clutch for transmitting torque between a relatively rotatable housing and a rotary shaft, a piston for pressing the multi-plate clutch, and an oil corresponding to differential rotation between the housing and the rotary shaft. In a driving force transmission device including a hydraulic pressure generating unit that applies a pressure to the piston, a cam engagement body that engages a circumferential cam surface provided on an end wall of the housing in the housing is provided with the housing. It is mounted so as to generate thrust for pressing the multi-plate clutch by relative rotation, and a plurality of outer plates of the multi-plate clutch are engaged in the cam engagement body in the rotational direction, respectively, and arranged between the outer plates. Engaging a plurality of inner plates of the multi-plate clutch to the rotary shaft,
A driving force transmission device comprising an urging force control means for changing the urging force of a spring for urging the cam engagement body in the direction of engaging the cam surface of the housing according to the vehicle speed.