JPH0366927A - Power transmission - Google Patents

Abstract

PURPOSE:To protect the engagement force of a friction clutch and reduce the size of a motor by employing the friction clutch for connecting a pair of transmission shafts capable of free relative rotation, and a cam for converting the torque of a motor into a thrust for connecting the friction clutch. CONSTITUTION:An output shaft 45 is inserted for free relative rotation into an input shaft 35. A friction clutch 61 is constituted with friction plates 57, 59 which engages with splines 53, 55 formed on clutch drums 49, 51 in free movement to the axial direction. A cam is provided for converting the torque of a motor 67 into a thrust for connecting the friction clutch 61. On the cam face of this cam, portions which do not convert the torque into thrust are formed in steps. Thus, the size of the motor is reduced and the motor current may be turned off in each engaged condition, and therefore the motor is prevented from a burn and the power consumption is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a power transmission device used in a vehicle or the like.

(Prior Art) Japanese Patent Application Laid-open No. 63-203958 describes an "actuator for frictional engagement device". This is a device that converts the rotational force of a motor into thrust force, operates a multi-disc clutch disposed between a pair of transmission shafts, and controls the connection and disconnection between these transmission shafts and the transmission torque.

(Problem to be solved by the invention) The conversion of the rotational force of the motor into thrust force is achieved by using a ball screw,
This is done with a normal screw, but if a ball screw is used, the reaction force from the multi-plate clutch applies a rotational force in the opposite direction to the motor via the ball screw. Therefore, when the current is turned off, the pressing force is lost, so the fastening force cannot be kept constant unless the current continues to flow through the motor during suppression. If power is applied with the rotor fixed in this way, there is a risk that the field coil of the motor will burn out.

Furthermore, if a normal screw or worm gear is used to prevent reverse rotation, the efficiency will be poor and a motor with high horsepower will be required, resulting in high power consumption.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a power transmission device in which the engagement force of a friction clutch is protected even when the motor current is cut off, and the same engagement force (transmitted torque) can be obtained with a relatively small horsepower motor.

[Structure of the Invention] (Means for Solving the Problems) A power transmission device of the present invention includes a pair of relatively rotatable transmission shafts, a friction clutch that connects these shafts, an externally operable motor, and an externally operable motor. A cam that converts rotational force into thrust force to engage the friction clutch is characterized in that the cam surface of the cam is provided with portions that do not convert thrust force into rotational force in stages.

(Operation) When the motor rotates, this rotational force is converted into thrust force by the cam, and the friction clutch is pressed and engaged.
The transmission members are connected. At this time, if the rotation of the motor is stopped at the position where the cam follower comes into contact with a part of the cam surface that does not convert thrust force into rotational force, such as a recess or a flat part, the friction clutch can be changed in stages. It can be fastened with extra strength. Furthermore, since the cam does not rotate in reverse at this time, the fastening force can be maintained even if the motor current is cut off. In particular, when a recess is provided, the cam follower is positioned in the rotational direction by engaging with the recess, so that the fastening force is stably maintained.

(Example) One embodiment will be explained with reference to FIG. 1 and FIG. 2.

FIG. 2 shows the power system of a vehicle using this embodiment.

Below, the left and right directions are the left and right directions of these drawings,
The left side of FIG. 1 corresponds to the front of this vehicle (the upper side of FIG. 2). Also, members that are not numbered are not shown.

First, the power system of the vehicle shown in FIG. (differential device), front axle 13°15, left and right front wheels 17, 19,
It is composed of a propeller shaft 21 on the rear wheel side, a rear differential 23 (a differential device on the rear wheel side), rear axles 25, 27, left and right rear wheels 29, 31, and the like.

Next, the configuration of the power transmission device 7 will be explained. Housing 33
is fixed inside the case of the transfer 5. A hollow input shaft 3 is inserted into the opening provided at the left end of the housing 33.
5 (transmission shaft) is rotatably supported via a bearing 37. The human power shaft 35 is located outside the housing 33.
A ring gear 39 is fixed to. This gear 39 is rotationally driven by the driving force from the transmission 1. An output shaft 45 (transmission shaft) is fitted into the input shaft 35 so as to be relatively rotatable. This output shaft 45 is connected to the propeller shaft 9 side and transmits the driving force from the engine 1 to the front wheels 17 and 19 side. Seal 4 between each shaft 35.45
7 is placed.

Inside the housing 33, these input and output shafts 35.
Clutch drums 49 and 51 are formed at the right end portions of the clutch drums 49 and 45, respectively. Splines 53 formed on each drum
．． Inner and outer friction plates 57 and 59 arranged alternately are engaged with the clutch 55 so as to be movable in the axial direction, thereby forming a multi-plate clutch 61 (friction clutch). A pressure receiving ring 63 is installed at the left end of the multi-disc clutch 61.

A reversible motor 67 is attached to the outside of the right side wall 65 of the housing 33, and a gear 71 is formed at the tip of a rotor spindle 69 that passes through the side wall 63. A cam ring 75 is rotatably supported inside the right side wall 65 via a bearing 73. A gear 77 is formed on the outer periphery of the cam ring 75.
7 meshes with the gear 71 of the rotor spindle 69.

In this way, the cam ring 75 is driven to rotate reversibly by the motor 67. The motor 67 is configured to automatically start, rotate forward, reverse, stop, etc., depending on steering conditions, road surface conditions, and the like.

On the left side of the cam ring 75, there are marks shown in FIGS.
), seven cams are formed. The cam 79 has recesses 83 at multiple locations in the middle of the tapered portion 81, as shown in FIG.
are formed at equal intervals. Three such cams 79 are formed with their taper directions aligned. As shown in FIG. 7(d), the highest point 85 of each cam and the adjacent cam 79
The lowest point 87 is the Taber section 89 which is steeper than the Taber section 81.
Continuous through. As shown in FIG. 7B, each cam 79 has a ball 91, which is a cam follower, rotatably abuts on each cam surface.

Each ball 91 is held at equal intervals in the circumferential direction by a retainer 93.

The moving ring 95 is connected to the housing 3 by a spline portion 97.
3. Connected to the inner periphery so as to be movable in the axial direction.

A spherical recess 99 is provided on the right side surface of the ring 95, and a ball 91 is rotatably engaged in each recess 99. A needle bearing 101 is located on the left side of the moving ring 95.
, the ring 103, the return spring 105, and the pressing ring 107 of the multi-disc clutch 61 are arranged in contact with each other to constitute a pressing force transmission system. In this way, the power transmission device 7 is configured.

Therefore, when the cam ring 75 is rotated by the motor 67, the balls 91 rise on the cam surface of the cam 79, and this thrust force presses and engages the multi-disc clutch 61 via the above-mentioned transmission system. When the multi-plate clutch 61 is engaged, the human power shaft 35
and the output shaft 45 are connected, and the driving force from the engine 1 is transmitted to the front wheels 17 and 19 side. When the cam ring 75 is rotated in the opposite direction, the balls 91 move down the cam surface and move to the right by the biasing force of the return spring 105.
The fastening force of the multi-plate clutch 61 is weakened or released.

The engagement force of the multi-plate clutch 61 and the torque transmitted to the front wheels increase as the cam ring 75 rotates in the engagement direction, and decrease as the cam ring 75 rotates in the anti-engagement direction.

When the balls 91 engage with the recesses 83 of the cam 79 as the cam ring 75 rotates, the anti-thrust force from the multi-disc clutch 61 is not converted into rotational force and the ring 75 does not rotate.

Therefore, even if the current to the motor 67 is cut off at this point, the engagement force of the multi-disc clutch 61 is maintained as it is, and since the balls 91 are thus positioned on the cam 79, this engagement state is stable. Ball 91 is the highest point of cam 79 85
When the cam ring 75 is further rotated in the fastening direction when the ball 91 is in the vicinity, the ball 91 descends on the tapered portion 89 and reaches the lowest point 8.
7, and the multi-disc clutch 61 can be opened all at once.

In this way, by rotating the cam ring 75 and engaging the balls 91 with the respective recesses 83, the multi-disc clutch 61 can be stably engaged with stepwise strength, and the current of the motor 67 can be cut off in each engaged state. I can do it. Therefore, there is no risk of burning out the motor 67, and power consumption can be reduced. Further, since the cam has a higher conversion efficiency of rotating car thrust force than a conventional screw or worm gear, the torque is small and the motor 67 can be made smaller.

Note that, as shown in FIG. 1(f), a flat portion 115 in the rotational direction of the cam ring 113 may be formed in the middle of the tapered portion 111 of the cam 109, similar to the recessed portion 83 in the cam 79.

Next, the functions of this embodiment will be explained based on the power performance of the vehicle shown in FIG.

When the multi-plate clutch 61 of the power transmission device 7 is engaged, the vehicle enters a four-wheel drive (4WD) driving state. Since the rear wheels 29, 31 are directly driven by the engine 1, by adjusting the transmission torque of the multi-disc clutch 61, the driving force distribution ratio between the front and rear wheels can be changed arbitrarily, and the power characteristics of the vehicle can be controlled as shown below. be able to.

That is, as the engagement force of the multi-disc clutch 61 is strengthened, the amount of limited differential between the front and rear wheels increases, and the straight-line stability of the vehicle increases.

Also, even if the rear wheel 29.31 side slips, the front wheel 1
Since the driving force is transmitted to the 7.19 side, the running performance of the vehicle is maintained. When the engagement force of the multi-disc clutch 61 is weakened, differential motion between the front and rear wheels is allowed, the turning performance of the vehicle is increased, and tight corner braking is prevented.

When the multi-disc clutch 61 is released, the transmission of driving force to the front wheels is cut off, resulting in a two-wheel drive running state with rear wheel drive, which provides such power characteristics and improves fuel efficiency compared to when running in 4WD.

As described above, the engagement state of the multi-disc clutch 61 is stable, and the engagement force does not change due to vibrations during driving.

[Effects of the Invention] As described above, the power transmission device of the present invention is configured so that the rotational force of the motor is converted into thrust force by the cam and the multi-disc clutch is engaged, so that the motor can be made smaller. In addition, because we have provided a stepwise section on the cam surface that does not convert the thrust reaction force into rotational force, the engagement force (transmission torque) of the multi-disc clutch can be reduced.
can be increased or decreased in stages, and the current to the motor can be cut off in each fastened state, thereby preventing burnout of the motor and reducing power consumption.

[Brief explanation of drawings]

FIG. 1 relates to one embodiment, (a) is a sectional view, (b) is (
a) A-A cross-sectional view, (c) a B-B cross-sectional view of (b),
(d) is a developed view of the cam, (e) is an enlarged longitudinal partial view of (d), (f) is a developed view showing another aspect of the cam, and FIG. 2 is an example of the embodiment shown in FIG. 1(a). FIG. 2 is a skeleton mechanism diagram showing the power system of a vehicle using the vehicle. 35...Input shaft (transmission shaft) 45...Output shaft (transmission shaft)

Claims (1)

[Claims] The cam includes a pair of relatively rotatable transmission shafts, a friction clutch that connects them, an externally operable motor, and a cam that converts the rotational force of the motor into thrust force to engage the friction clutch. A power transmission device characterized in that a cam surface of the device is provided with a stepwise portion that does not convert thrust force into rotational force.