JP2003327082A - Speed reduction mechanism for electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a speed reduction mechanism for an electric power steering device provided with a key lock mechanism, capable of sufficiently securing a space and having a simple constitution. <P>SOLUTION: In this speed reduction mechanism for the electric power steering device, a shaft of a motor is connected to a worm shaft 10 and an output of the motor is transmitted to a steering shaft 1 via a worm 9 and a worm wheel 2. This mechanism is provided with the key lock mechanism constituted of many lock holes 2b provided at equal intervals in the peripheral direction of the worm wheel 2 and a lock unit 5 having a lock pin 6 engaged to the lock holes 2b. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed reduction mechanism for an electric power steering device.

[0002]

2. Description of the Related Art A conventional steering shaft key lock mechanism is disclosed in, for example, Japanese Utility Model Laid-Open No. 3-24959, as shown in FIG. In the figure,
An engagement hole 2 is formed by pressing a metal plate into an elliptic cylinder shape, and an inner end portion of the lock pin 22 is engageable with a part of the oval cylinder shape.
The lock bracket 21 provided with 1a is welded and fixed to the outer peripheral surface of the intermediate portion of the steering shaft 20. Reference numeral 23 is an ignition switch, 24 is a key, and 25 is a steering column.

Further, in Japanese Patent Laid-Open No. 2001-163187, the steering shaft is centered on the steering shaft in a lock member that is inserted into the steering column so as to be relatively movable in the column axis direction and to prevent relative rotation about the column shaft center. The lock member is relatively rotatably inserted in the steering wheel, and the lock member is displaced in the column axial direction between the locked position and the unlocked position by interlocking with the transmission mechanism that operates in accordance with the opening / closing operation of the ignition switch by the opening / closing mechanism. A shaft key lock mechanism is disclosed. The lock member at this lock position is connected to the receiving part that can rotate together with the steering shaft so that it cannot rotate relative to the center of the column shaft, and when its unlocked position is released, the lock member rotates relative to the receiving part about the center of the column shaft. This is the configuration.

[0004]

However, in the conventional key lock mechanism for the steering shaft, the lock bracket 21 is welded and fixed to the steering shaft, or the lock shaft and the torque limiter are combined with the steering shaft so that they can rotate relative to each other. Since the key lock mechanism and its surroundings are complicated and the number of parts is increased to occupy a space, there is a problem that the collapse stroke of the steering shaft is limited.

Particularly, in the case of an electric power steering system, since a reduction mechanism including a worm and a worm wheel is equipped, a key lock mechanism is provided on a steering shaft (or a transmission shaft connected to the shaft). , It was difficult to secure enough space for the shaft.

The present invention improves the disadvantages of the above-mentioned conventional example, includes a key lock mechanism, and can sufficiently secure a space on the steering shaft (or a transmission shaft connected to the shaft). An object is to provide an electric power steering device having a simple structure.

[0007]

In order to achieve the above object, according to the present invention, there is provided a deceleration mechanism of an electric power steering apparatus, wherein an output of a motor is transmitted to a steering shaft, and the deceleration mechanism is provided in the deceleration mechanism. Provided is a reduction mechanism for an electric power steering device, which is provided with a key lock mechanism for preventing power transmission from a motor.

With the above construction, it is not necessary to provide a key lock mechanism on the steering shaft (or a transmission shaft connected to the same shaft), and a sufficient space can be secured on the shaft, which allows the collapse. The stroke can be taken sufficiently.

The deceleration mechanism of the electric power steering apparatus of the present invention includes a drive shaft to which a motor shaft is connected, a drive gear connected to the drive shaft, and a driven gear connected to the steering and transmitting power from the drive gear. The key lock mechanism includes at least one lock hole provided in any of the drive shaft, the drive gear, and the driven gear, and a lock unit having a lock pin that engages with the lock hole. It can be configured.

Further, in the reduction mechanism of the electric power steering apparatus of the present invention, the drive shaft may be a worm, and the driven gear may be a worm wheel engaging with the worm.

Further, in the reduction mechanism of the electric power steering apparatus of the present invention, the lock holes may be provided in large numbers at equal intervals in the circumferential direction of the worm wheel. According to this configuration, since the distance from the axial center of the lock hole position of the worm wheel can be made relatively large, it is possible to lock with a smaller yield strength against the same input torque due to the force moment.

Furthermore, in the reduction mechanism of the electric power steering device of the present invention, the lock hole may be formed in a lock bracket provided on the worm shaft.

[0013]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a reduction gear mechanism of an electric power steering system showing a first embodiment of the present invention, FIG. 2 is a view of the worm wheel of FIG.
Is a cross-sectional view of the reduction mechanism of the electric power steering apparatus according to the second embodiment, FIG. 4 is a view of the worm wheel of FIG. 3 seen from the direction of arrow B, FIG. 5 is a perspective view of a tolerance ring, and FIG. It is sectional drawing of the reduction mechanism of the electric power steering apparatus which shows 3rd Embodiment.

In FIG. 1, a torsion bar 7 is fitted inside, and a worm wheel 2 is fitted and fixed to a transmission shaft 1 which is coaxially connected to a steering shaft (not shown). This transmission shaft 1 is attached to a cover 3. And is rotatably provided via the bearing 4.

The worm wheel 2 is engaged with a worm (9 in FIG. 6) which is a drive gear connected to the output shaft of a motor (M in FIG. 6) for power assistance, and transmits power from the motor. It is a driven gear that receives and constitutes a part of the reduction mechanism. The structure of the speed reducing mechanism itself is a conventionally known structure, and detailed description thereof will be omitted.

In the present embodiment, the worm wheel 2
As shown in FIG. 2, a large number of lock holes 2b are arranged in the core metal portion 2a at equal intervals in the circumferential direction.

On the other hand, on the cover 3 side, a lock unit 5 having a cylinder (lock pin) 6 freely movable in the axial direction is arranged. The cylinder 6 of the lock unit 5 is moved in the axial direction, and the tip of the cylinder 6 is locked by being engaged with the lock hole 2b of the worm wheel 2. The lock hole 2b, the lock unit 5, and the cylinder 6 constitute a key lock mechanism. When the steering shaft is connected to a universal joint (cross joint) which is not shown, the lock unit 5 is arranged at a position avoiding the swing circle of the joint.

In the above structure, the distance between the lock hole 2b of the worm wheel 2 and the center of the transmission shaft 1 is at least 4 mm.
It can be placed over 0 mm. This is because the moment force has a smaller proof strength against the input torque than the case where the distance from the shaft center (column center) is 25 to 30 mm like the lock hole of the conventional key lock mechanism. Since the lock can be performed, it becomes easy to pass the regulation that requires the lock to withstand a predetermined input torque.

Further, unlike the conventional case, it is not necessary to provide the lock bracket on the steering shaft (or the transmission shaft connected to the same shaft), so that a sufficient space can be secured on the shaft.

Next, a second embodiment will be described with reference to FIGS. 3 and 4. This embodiment is substantially the same as the first embodiment, and the same members are given the same numbers.
The difference is that the worm wheel 2 is externally fitted to the transmission shaft 1 via a tolerance ring 8 which is a torque limiter.

As shown in FIG. 5, the tolerance ring 8 is formed integrally with a metal ring main body having a split groove, and a large number of projections 8a projecting radially outward at equal intervals along the circumferential direction. Thus, a radial force corresponding to the radial deformation amount of each protrusion 8a is applied to the outer peripheral surface of the transmission shaft 1 and the shaft hole of the cored bar 2a of the worm wheel 2.

The friction between the outer circumference of the tolerance ring 8 and the inner circumference of the shaft hole of the cored bar 2a, and the tolerance ring 8
The torque between the transmission shaft 1 and the cored bar portion 2a can be transmitted by the friction between the inner peripheral portion of the transmission shaft 1 and the outer periphery of the transmission shaft 1.
The core metal portion 2a and the core metal portion 2a are integrally rotatable up to a preset limit torque. When a torque exceeding this limit torque acts on the cored bar 2a from the transmission shaft 1,
Sliding occurs between the outer periphery of the tolerance ring 8 and the inner periphery of the shaft hole of the cored bar 2a, or between the inner periphery of the tolerance ring 8 and the outer periphery of the transmission shaft 1, so that the cored bar 2a is It rotates relative to the transmission shaft 1.

The value of this limit torque may be set so that the core metal portion 2a and the lock unit 5 are not damaged by its action, and the press-fitting and interference control of the tolerance ring 8 may be performed according to the value of the limit torque. .

As described above, when a torque exceeding the limit torque acts on the cored bar portion 2a from the transmission shaft 1, the worm wheel 2 rotates relative to the transmission shaft 1, so that the cylinder 6 of the lock unit 5 is excessively bent. It is possible to prevent damage due to input.

Next, a third embodiment will be described with reference to FIG. In this embodiment, a worm shaft 10 integrally having a worm 9 is rotatably and integrally connected to an output shaft M1 of the motor M. The worm wheel 2 meshes with the worm 9. A lock bracket 11 is integrally provided on the worm shaft 10. The cylinder 6 of the lock unit 5 fixed to the housing Z is engaged with the lock hole 11a of the lock bracket 11 to be locked.

The lock bracket 11 can be externally fitted / fixed on the worm shaft 10 or joined by press-fitting / welding or the like. However, the same tolerance ring as that of the second embodiment is attached to limit the limit torque. It can also be configured to have.

In this structure, when torque is applied to the transmission shaft 1 of the worm wheel 2, the worm wheel 2
The lock bracket 11 prevents the worm shaft 10 from moving in the circumferential direction due to the meshing relationship between the worm 9 and the worm 9.
And cylinder 6 are engaged to prevent this. At this time, the torque applied to the transmission shaft 1 of the worm wheel 2 can be supported with a proof stress of (1 / gear reduction ratio) as compared with the case where the worm wheel 2 is locked as in the above embodiment.

In the above embodiment, the worm / worm wheel gear mechanism is exemplified as the speed reducing mechanism, but the present invention is not limited to this, and may be applied to, for example, a hypoid gear mechanism, a spur gear mechanism, or a helical gear mechanism. Applicable.

[0029]

As described above, according to the present invention,
Since the deceleration mechanism is provided with the key lock mechanism, a sufficient space can be secured on the steering shaft (or the transmission shaft connected to the shaft), and the telescopic mechanism or the like can be provided.

Further, since the distance from the shaft center of the lock position can be made larger than in the conventional case, it is possible to easily clear the regulation of the proof stress against a predetermined input torque in relation to the moment of force.

Further, since the length of the fitting portion of the inner column and the outer column can be made large, a sufficient collapse stroke can be obtained, which can also contribute to advantageous characteristics at the time of collision. Further, it is not necessary to provide a key lock mechanism on the steering shaft, and column rigidity and column bending rigidity can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a reduction gear mechanism of an electric power steering device according to a first embodiment of the present invention.

FIG. 2 is a view of the worm wheel of FIG. 1 viewed from the direction of arrow A.

FIG. 3 is a cross-sectional view of a speed reduction mechanism of an electric power steering device according to a second embodiment.

FIG. 4 is a view of the worm wheel of FIG. 3 viewed from the direction of arrow B.

FIG. 5 is a perspective view showing a tolerance ring.

FIG. 6 is a cross-sectional view of a reduction gear mechanism of an electric power steering device showing a third embodiment.

FIG. 7 is a partial cross-sectional view showing a conventional key lock mechanism.

[Explanation of symbols]

1 Steering shaft (transmission shaft) 2 worm wheel 2a core metal 2b Lock hole 5 Lock unit 6 Lock pin (cylinder) 9 warm 10 Worm axis 11 Lock bracket

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Sakae Matsumoto             Gunma Prefecture Maebashi City 1-8-1 Sojamachi Japan             Within Seiko Co., Ltd. F-term (reference) 3D033 CA04

Claims (5)

[Claims] 1. A deceleration mechanism for an electric power steering device, which transmits an output of a motor to a steering shaft, wherein a key lock mechanism for preventing power transmission from the motor is provided in the deceleration mechanism. Characteristic electric power steering device speed reduction mechanism 2. A key-lock mechanism comprising: a drive shaft to which a shaft of a motor is connected; a drive gear connected to the drive shaft; and a driven gear connected to a steering and transmitting power from the drive gear. The at least one lock hole provided in any one of the drive shaft, the drive gear, and the driven gear, and a lock unit having a lock pin that engages with the lock hole. Deceleration mechanism of the electric power steering device. 3. The electric power steering system according to claim 2, wherein the drive shaft and the drive gear are integrally formed worms, and the driven gear is a worm wheel engaged with the worm. Device speed reduction mechanism. 4. The reduction mechanism of the electric power steering apparatus according to claim 2, wherein the lock holes are provided in large numbers at equal intervals in the circumferential direction of the worm wheel. 5. The deceleration mechanism of the electric power steering device according to claim 1, wherein the lock hole is formed in a lock bracket provided on the worm shaft.