JPH06312626A - Power transmission - Google Patents

Abstract

PURPOSE:To provide a power transmission capable of suppressing tight braking at the time of traveling at low speed with a large steering angle, improving escaping performance from a mire or the like and heightening manuevering stability at the time of traveling on a low mu road at high speed. CONSTITUTION:A hydraulic power transmission for transmitting power between a casing 29 and a retainer 30 by boosting operating oil in an oil pressure generating chamber by a driven gear 31 and a ring gear 32 according to the rotational difference between the casing 29 and the retainer 30 is provided with initial torque transmission mechanism for transmitting torque when the rotating speed of the casing 29 is the specified value or more. This torque transmission mechanism is formed of a weight 41 moved radially by centrifugal force generated by the rotation of the casing 29, a cam 42 for moving the retainer 30 axially by the movement of the weight 41, the male taper face 44a disposed on the other end face side of the retainer 30, and the male-female taper face 47a fixed to the casing 29.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power transmission device for transmitting power in accordance with the difference in the number of rotations of a rotating shaft connected thereto, and more specifically, to improve the maneuverability on a low μ road and the ability to escape from a muddy road. The present invention relates to an improvement in the initial torque generation mechanism that can be improved and can avoid the adverse effect of the tight braking phenomenon.

[0002]

2. Description of the Related Art 4W in which front and rear wheels are driven by an engine
Vehicle D employs a power transmission device that distributes the driving force of the engine to the front and rear wheels according to the rotational speed difference between the front and rear wheels.
As this type of device, a device having a viscous coupling between the front and rear wheels (first conventional example), a device having a hydrocoupling (second conventional example), or Japanese Patent Laid-Open No. 1-250625 is disclosed. There is a device (third conventional example).

First, as shown in FIG. 8, the transmission torque characteristics of the first prior art device provided with the above-mentioned viscous coupling generate an initial torque (A) even when there is no difference in the number of revolutions, and the difference in the number of revolutions is The transmission torque tends to increase rapidly at first and then gradually increase as it increases.

As shown in FIG. 9, the transmission torque characteristic of the second prior art device provided with the hydrocoupling is such that the transmission torque gradually increases at first as the rotational speed difference increases.
After that, it tends to increase sharply.

Further, as shown in FIG. 10, the transmission torque characteristics of the above-mentioned third conventional device generate initial torque (B) even when there is no difference in rotation speed between the front and rear wheels, and the difference in rotation speed increases. Accordingly, the transmission torque increases with the same tendency as in the second conventional example.

[0006]

In the device provided with the viscous coupling of the first conventional example, since the initial torque is generated, the maneuverability on the low μ road is high, but the tight braking phenomenon is large. In addition, there is a drawback that the ability to escape from the muddy area is low. The same applies to the case of the third conventional example.

Further, in the device provided with the hydrocoupling of the second conventional example, although the tight braking phenomenon is small and the ability to escape from the mud is high, the initial torque is not generated and the rotational speed is structurally increased. Since there is a time lag between the occurrence of the difference and the transmission torque, a low μ
When driving on a road, there is a drawback that the maneuverability is low.

The present invention has been made in view of the above-mentioned conventional problems, and tight braking can be suppressed especially at low speed and large steering angle traveling where it becomes a problem, and on a road surface having a small friction coefficient. It is an object of the present invention to provide a power transmission device capable of improving the operational stability during traveling of the vehicle, particularly during traveling in the medium-high speed range where this is a problem, and further improving the ability to escape from muddy or the like.

[0009]

The invention according to claim 1 is the first
In a power transmission device equipped with a mechanism for transmitting power according to a difference in rotation speed between the first rotation shaft and the second rotation shaft, when the input rotation speed of the first rotation shaft is equal to or more than a predetermined value, the rotation speed difference is Regardless of this, an initial torque transmission mechanism for transmitting an initial torque from the first rotary shaft to the second rotary shaft is provided.

According to a second aspect of the present invention, the power transmission mechanism is
A retainer, to which the second rotary shaft is connected, is arranged coaxially and axially movable in a casing to which the first rotary shaft is connected, and a driven gear rotatably supported by the retainer is provided on the inner surface of the casing. To form a hydraulic pressure generating chamber by the casing, the ring gear, the driven gear, and the retainer, and the hydraulic oil in the hydraulic pressure generating chamber is moved in accordance with the rotation difference between the first and second rotating shafts. It is configured to transmit power between the first rotary shaft and the second rotary shaft by increasing the pressure by the driven gear and the ring gear, and the initial torque transmission mechanism is
Axial moving means, which is disposed on one end side of the retainer and moves the retainer in the axial direction by centrifugal force when the number of rotations of the first rotating shaft is a predetermined value or more, and on the other end side of the retainer. It is characterized in that it is provided with a connecting means for connecting the retainer and the casing by the movement in the axial direction.

[0011]

According to the power transmission device of the present invention, the initial torque is not transmitted and the tight braking phenomenon does not occur when the input rotation speed of the first rotary shaft is running at a low speed or less.
When a difference in rotation speed occurs, torque is transmitted according to the difference, and escapeability such as mud can be secured. In addition, the initial torque is transmitted during high-speed traveling in which the input rotation speed of the first rotation shaft is equal to or higher than the predetermined value, and the steerability on a low μ road can be improved. When a rotation speed difference occurs, torque is transmitted according to the difference.

According to the second aspect of the present invention, the axial moving means moves the retainer in the axial direction, and the connecting means connects the retainer and the casing by the movement of the retainer. Will be transmitted.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 5 are views for explaining a power transmission device according to an embodiment of the present invention, FIG. 1 is a schematic configuration diagram of a four-wheel drive vehicle, and FIG. 2 is a configuration diagram schematically showing hydraulic oil flow paths. 3 is a cross-sectional side view, FIG. 4 is an enlarged view of a main part of FIG. 3, and FIG.
5 is a sectional view taken along line VV of FIG. In the present embodiment, a case where the present invention is applied to a four-wheel drive vehicle based on the front engine / rear drive system will be described as an example.

In FIG. 1, reference numeral 17 denotes a four-wheel drive vehicle to which the device of this embodiment is applied.
A transmission 19 is connected to 8 via a clutch, and a transfer 20 is connected to the transmission 19. This transfer 20
Transmits the driving force from the engine 18 to the rear wheel 22 via the propeller shaft 21, and at the same time, the transmission shaft 23
Is transmitted to the front wheel 24 via the front differential 24a between the front wheel 24 and the transmission shaft 23.
A front differential (hereinafter abbreviated) is disposed, and a rear differential 25b (hereinafter rear differential) is disposed between the rear wheel 22 and the propeller shaft 21.

The front differential 25a and the transmission shaft 2
3, a hydraulic power transmission device 26 for increasing / decreasing the driving force to the front wheels 24 according to the running condition and consequently controlling the driving force distribution ratio to the front and rear wheels 24, 22 is arranged. It is set up.

The power transmission device 26 has forward and reverse main oil passages 27a and 27, as shown in FIG.
It is of a gear pump type which incorporates a main oil passage 27 composed of b, an oil tank 38, and the like. This power transmission device 26
In the casing 29, a retainer 30 is rotatably and coaxially arranged, and four driven gears 31 rotatably supported by the retainer 30 are axially movable on the inner surface of the casing 29. Installed ring gear 3
2, the ring gear 32, the driven gear 3
1, a structure in which a hydraulic pressure generating chamber (A to H) is formed by the casing 29 and the retainer 30. The retainer 30 is connected to the front differential 25a, and the casing 29 is connected to the transmission shaft 23. As a result, the hydraulic oil in the hydraulic pressure generating chambers (A to H) is increased in pressure by the driven gear 31 and the ring gear 32 according to the rotation difference between the front and rear wheels 24, 22, and thus the transmission shaft 23 and the front. Power is transmitted to the differential 25a.

3 to 5 showing the concrete structure of the power transmission device 26, the casing 29 comprises a disc-shaped bottom wall portion 29a and a bottomed cylindrical body portion 29b fixed to the bottom wall portion 29a. The ring gear 32 is inserted and arranged in the body portion 29b.

The retainer 30 has a four-lobed main body 30a for rotatably supporting the driven gear 31,
And a large diameter portion 33e and a tip portion 33f of the shaft portion 33 which are spline-fitted to the rolling bearing 3
It is rotatably supported by the casing 29 via 4, 35. A pressure resistant oil seal 36 is provided between the body portion 29b of the casing 29 and the large diameter portion 33e of the shaft portion 33. Further, the tip portion 33 of the shaft portion 33
The opening 29c of the bottom wall portion 29a in which f is inserted is closed by a lid member 37 and a seal member 38.

An oil tank 38 is formed at the axial center of the large-diameter portion 33e of the shaft 33 so as to store the working oil and absorb the increase in the volume of the working oil due to the increase in the oil temperature. The oil tank 38 has a structure in which a piston 39 is slidably inserted in a cylinder hole 38a and a piston ring 40 seals between the two.

On the other hand, referring to FIG.
To the right of the driven gear 31 in the drawing, the weight 4 that moves in the radial direction by the centrifugal force generated by the rotation of the casing 29.
1 and the body portion 29 by the radial movement of the weight 41.
A cam 42 that moves in the axial direction is provided along the inner surface of b. Further, the retainer 3 is provided on the back surface of the cam 42.
The seal plate 4 slidably slidably contacts the right end surfaces of the main body 30a of 0, the driven gear 31, and the ring gear 32.
3 is arranged via a thrust bearing 43a. In this way, the axial movement means is configured to axially move the retainer 30 leftward in the drawing when the input rotation speed of the transmission shaft 23 becomes equal to or higher than the predetermined value. Further, the axial moving means also functions as a spring that applies a preload to the movable side plate 44 described later.

Further, on the left side of the driven gear 31 in the casing 29 in the drawing, there is a male taper surface 44a having a smaller diameter on the left side in the drawing, and the main body portion 30 of the retainer 30.
A movable side plate 44 slidably slidably provided on the left end surfaces of the a, the driven gear 31, and the ring gear 32.
The male taper surface 44a of the movable side plate 44 is fitted to the female taper surface 47a of the guide member 47 fixed to the inner surface of the casing 29. In this manner, the male and female tapered surfaces 44a and 47a are fitted by the axial movement of the retainer 30 to form a connecting means for connecting the casing 29 and the retainer 30. In contrast to the above, the male taper may be formed on the guide member 47 side and the female taper may be formed on the movable side plate side.

Further, as shown in FIG. 4, the movable side plate 4 is
4, two large and small piston holes 44b and 44c are formed in parallel in the axial direction.
A large diameter piston portion 46a and a small diameter piston portion 46b of the piston 46 are inserted therein. Large piston hole 4 above
4b, the space surrounded by the bottom surface of the large-diameter piston portion 46a and the tip surface is one hydraulic working chamber a, and the space surrounded by the small-diameter piston hole 44c, the bottom surface of the small-diameter piston portion 46b, and the tip surface is the other. Is the hydraulic working chamber b. The piston 46 is supported on the bottom surface of the body portion 29b via a thrust bearing 48 arranged on the back surface. Also,
The piston 46 is locked to the body portion 30a of the retainer 30 together with the movable side plate 44 by a pin 45, and is rotated together with the body portion 30a.

As shown in FIG. 4, the piston 46 has an orifice 46 communicating with the working chambers a and b.
c, 46d are provided, and the hydraulic working chamber a,
One-way valves 46e and 46f that prevent the flow of hydraulic oil from b to the oil tank are provided.

Here, as shown in FIGS. 2 and 4, the normal main oil passage 27a includes the forward rotation side hydraulic pressure generation chambers A, C, E, and G as the oil passage 30b of the main body portion 30a, the hydraulic working chamber b, Movable side plate 4
4, the oil tank 38 through the orifice 46d
Is in communication with.

Further, the sub-main oil passage 27b is configured such that the reverse rotation side hydraulic pressure generating chambers B, D, F and H are oil tanks via the oil passage 44d in the movable side plate 44, the hydraulic operating chamber a and the orifice 46c. 38.

The primary and secondary oil passages 50a connect the oil tank 38 and the primary main oil passage 27a via the one-way valve 46f. The reverse sub oil passage 50b connects the oil tank 38 and the reverse main oil passage 27b via the one-way valve 46e.

That is, the hydraulic pressure generating chambers A, C, E on the forward rotation side,
The pressure of G is such that the orifice 46d and the one-way valve 46f arranged between the oil pressure generating chamber and the oil tank 38.
As a result, the pressures in the positive-side hydraulic working chamber b and in the reverse-side hydraulic generating chambers B, D, F, and H are controlled by the orifice 46c and the one-way valve 46e arranged between the hydraulic generating chamber and the oil tank 38. Thus, each of them acts on the opposite hydraulic working chamber a.

Next, the function and effect will be described. For example,
When the front wheel rotation speed and the rear wheel rotation speed are the same at low speed traveling, the casing 29 and the retainer 30 have the same rotation speed. Therefore, the driven gear 31 and the ring gear 32
There is no relative rotation between, and no hydraulic pressure is generated, so there is no increase in torque transmission to the front wheels 24, as shown in FIG. Further, at this time, since the weight 41 is traveling at a low speed and a sufficient centrifugal force does not work, the weight 41 does not move in the radial direction and the initial torque described later does not occur. Therefore, it is possible to avoid the tight braking phenomenon, which is a problem when traveling at a low speed and a large steering angle.

When the rear wheel rotation speed becomes higher than the front wheel rotation speed due to slip of the rear wheel 22, the rotation speed of the casing 29 becomes higher than that of the retainer 30, and the ring gear 32,
The driven gear 31 rotates in the direction of arrow a in FIG. In this case, for example, when focusing on the driven gear 31 ', the hydraulic pressure generation chamber A is the discharge side and the hydraulic pressure generation chamber H is the suction side. The hydraulic oil discharged from the hydraulic pressure generating chamber A flows into the positive hydraulic pressure operating chamber b from the oil passage 30b. And
The hydraulic oil is blocked from flowing into the oil tank 38 by the one-way valve 46f, and the orifice 46d
The front wheel 24
When the rotational difference is increased, the transmission torque is also increased as shown in FIG. 6, and therefore the escapeability due to muddyness can be improved.

Further, at this time, the movable side plate 44 presses the left end surface of the driven gear 31, the retainer main body 30a, and the ring gear 32 in the drawing by the above hydraulic pressure, and the right end surface of the drawing presses the seal plate 43, thereby generating the hydraulic pressure. Oil leakage from the left and right end surfaces of the chamber is prevented.

Next, when traveling at high speed, in FIG. 3, the weight 41 is moved radially outward from the axial center side by the centrifugal force, and the cam 42 moves the movable side plate 44 through the main body 30a of the retainer 30 and the like. It is pressed to the left in the drawing, whereby the male taper surface 44a and the female taper surface 47a are combined,
As a result, the rotation of the casing 29 is transmitted to the retainer 30, and the torque is transmitted to the front wheels as so-called initial torque even if there is no difference in the number of revolutions, and the characteristic has the initial torque (C) as shown in FIG. 7. . Therefore, the maneuverability on the low μ road can be improved. At this time, the axial force of the weight 41 and the cam 42 is applied to the movable side plate 4.
Preload is applied to 4.

When a rotational speed difference occurs during high-speed traveling, in the range (a) where the rotational speed difference is smaller than k in FIG. 7, the transmission torque is the male and female tapered surfaces 44a, 4a.
Since the coupling force of 7a is larger than the pressing force of the movable side plate 44, the coupling is maintained and becomes almost the same as the initial torque (C) due to the coupling. Also, the above k was exceeded (b)
In the range, the pressing force of the movable side plate becomes large, the coupling of the tapered surfaces 44a and 47a is released, and the transmission torque increases with the same tendency as in the low speed (FIG. 6).

When the rotational speed of the front wheel 24 becomes higher than the rotational speed of the rear wheel 22 due to the slip of the front wheel 24 or the like, the hydraulic pressure generating chamber H becomes the discharge side and the hydraulic pressure generating chamber A becomes the suction side contrary to the above. .

As described above, in this embodiment, the axial movement means constituted by the weight 41 and the cam 42, and the coupling means constituted by the male taper surface 44a and the female taper surface 47a are provided. Since the initial torque transmission mechanism that generates the initial torque only when the number is equal to or greater than the predetermined value is provided, the initial torque is not generated during low-speed traveling, the tight braking phenomenon can be avoided, and the rotation difference occurs. The transmission torque is increased, and escapeability such as mud can be improved. Since the initial torque is generated during high speed traveling, it is possible to improve the maneuverability during low μ road traveling.

Further, in this embodiment, when the difference in the number of revolutions becomes large, the connection between the tapered surfaces 44a and 47a is released, so that the wear of both can be prevented and the durability can be improved. Noise can be avoided by preventing squeaking.

[0036]

As described above, according to the power transmission device of the first aspect of the present invention, when the rotation speed of the first rotating shaft is equal to or higher than a predetermined value, the first rotating shaft changes to the second rotating shaft. Since the initial torque transmission function that transmits the initial torque is provided, it is effective in avoiding the tight braking phenomenon at the time of low speed traveling and improving the escapeability such as mud, etc. There is an effect that the maneuverability in the can be improved.

According to the power transmission device of the second aspect of the present invention, the initial torque transmission mechanism is composed of the axial moving means and the connecting means, so that the initial torque can be transmitted only when the input rotation speed is equal to or higher than the predetermined rotation speed. .

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a four-wheel drive vehicle including a power transmission device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram schematically showing a working fluid flow path of the power transmission device of the above embodiment.

FIG. 3 is a sectional side view of the power transmission device of the above embodiment.

FIG. 4 is an enlarged view of a main part of FIG.

5 is a sectional view taken along line VV of FIG.

FIG. 6 is a diagram showing a relationship between a rotation difference and a transmission torque when the power transmission device of the above-described embodiment rotates at a low speed.

FIG. 7 is a diagram showing a relationship between a rotation difference and transmission torque during high-speed rotation of the power transmission device of the above embodiment.

FIG. 8 is a diagram showing a relationship between a rotation difference and a transmission torque of the first conventional example device.

FIG. 9 is a diagram showing a relationship between a rotation difference and a transmission torque of the second conventional example device.

FIG. 10 is a diagram showing a relationship between a rotation difference and a transmission torque of a third conventional example device.

[Explanation of symbols]

 26 Hydraulic Power Transmission Device 29 Casing 30 Retainer 31, 31 'Driven Gear 32 Ring Gear 41 Weight 42 Cam 44a Male Tapered Surface 47a Female Tapered Surface A to H Hydraulic Pressure Generation Chamber

Claims (2)

[Claims] 1. A power transmission device comprising a power transmission mechanism for transmitting power between two rotating shafts according to a rotational speed difference between the first rotating shaft and the second rotating shaft. When the input rotation speed is equal to or higher than a predetermined value, an initial torque transmission mechanism that transmits an initial torque from the first rotation shaft to the second rotation shaft is provided regardless of the difference in rotation speed. apparatus. 2. The power transmission mechanism according to claim 1, wherein the retainer, to which the second rotary shaft is connected, is arranged coaxially and axially movable in a casing to which the first rotary shaft is connected. , A driven gear rotatably supported by the retainer is meshed with a ring gear provided on the inner surface of the casing to form a hydraulic pressure generating chamber by the casing, the ring gear, the driven gear and the retainer, and the hydraulic oil in the hydraulic generating chamber is , The power is transmitted between the first rotating shaft and the second rotating shaft by increasing the pressure of the driven gear and the ring gear according to the rotation difference between the first rotating shaft and the second rotating shaft. The initial torque transmission mechanism is disposed on one end side of the retainer, and when the rotation speed of the first rotating shaft is equal to or more than a predetermined value, the centrifugal force causes the retainer to move in the axial direction. A power transmission device comprising: an axial moving means for moving; and a connecting means arranged on the other end side of the retainer for connecting the retainer and the casing by the axial movement.