Motor vehicles – Steering gear – With electric power assist
Reexamination Certificate
2001-06-22
2002-08-27
Zeender, F. (Department: 3627)
Motor vehicles
Steering gear
With electric power assist
Reexamination Certificate
active
06439339
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electronic power steering apparatus for a vehicle, and in particular to an electronic power steering apparatus for a vehicle which is capable of providing a support structure of a ball nut engaged with a motor shaft on a rack pinion type gear mechanism having a motor for thereby enhancing a steering force.
2. Description of the Background Art
Generally, a steering apparatus for a vehicle is directed to changing a running direction of a vehicle and includes an operating mechanism formed of a steering wheel, a steering shaft and a steering column, a gear mechanism for changing an operating direction of the operating mechanism, and a link mechanism for transferring a movement of the gear mechanism to a steering wheel.
The gear mechanism includes a worm sector type formed of a worm gear and a sector gear, and a rack pinion type which is operated based on a combination of a rack gear and a pinion gear. The electronic power steering apparatus further includes a motor and a decelerator capable of enhancing a steering force of the gear mechanism.
FIG. 1
is a cross sectional view illustrating a conventional rack pinion type electronic power steering apparatus. As shown therein, the conventional rack pinion type electronic power steering apparatus includes a torque sensor
10
for receiving a rotational force from the operating mechanism, a pinion housing
20
which is installed across the torque sensor
10
and has a rack bar
30
therein, a tie rod
40
formed at both ends of the rack bar
30
, and a motor
50
installed at an intermediate portion of the rack bar
30
.
The motor
50
includes a motor housing
51
having a certain diameter larger than that of the pinion housing
20
, a stator
52
installed closely to an outer surface of the interior of the same, a rotor
53
rotatably installed in an inner side of the stator
52
, a motor shaft
54
extended toward the inner side of the rotor
53
, and a ball nut
55
provided at one end in the interior of the motor shaft
54
.
At this time, a screw groove is formed in an inner side of the ball nut
55
and an outer side of the rack bar
30
, and a ball is disposed therebetween. Therefore, when the ball nut
55
is rotated, the rack bar
30
is moved in the axial direction.
One end of the motor shaft
54
is closely contacted with a step formed in the interior of the ball nut
55
, and the other end of the same is fixed by a lock screw
56
, and a stop ring
58
is installed in a rear side of the lock screw
56
.
The lock screw
56
is capable of preventing an escape of the ball nut
55
and includes a threaded portion formed in an outer surface of the same for thereby being engaged with a threaded portion formed in the interior of the motor shaft
54
. The stop ring
58
is capable of preventing an escape of the lock screw
56
and is inserted onto the outer portion of the groove
57
formed in the interior of the motor shaft
54
, so that the inner side supports the lock screw
56
.
In the conventional motor, the groove in which the stop ring is installed and the cross section of the stop ring are formed in a square shape, and the width of the groove is larger compared to the thickness of the stop ring for a smooth installation. Therefore, there is a certain operational gap therebetween.
Therefore, if the lock screw is loosened, since the lock screw is moved in the axial direction by the distance corresponding to the operational gap between the stop ring and the groove, the rotation and reciprocating movement of the ball nut fixed in the interior of the motor shaft becomes free.
Namely, since the rotational force transferred from the motor shaft to the ball nut is not properly obtained, a certain problem occurs in the steering force, and a noise occurs because the ball nuts collide with each other.
In addition, since a torque limit device is not provided, the motor may be damaged when an overload occurs.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an electronic power steering apparatus for a vehicle which overcomes the problems encountered in the conventional art.
It is another object of the present invention to provide an electronic power steering apparatus for a vehicle which is capable of improving the structures of a stop ring and a groove for thereby preventing a certain operational gap which is formed when installing the system and providing a torque limiting function when an over load occurs in the motor.
To achieve the above objects, there is provided an electronic power steering apparatus for a vehicle according to the present invention in which a groove is formed in a circular shape, an inner tapered surface is formed in an outer surface, a stop ring is formed to be expandable in the outer direction, and an outer tapered surface is formed in a portion opposite to the inner tapered surface at an outer surface for thereby being closely contacted with the groove based on a movement in the axial direction due to the expansion force of the stop ring wherein the electronic power steering apparatus for a vehicle includes a motor housing provided at an intermediate portion of a pinion housing having a rack bar therein, a ball nut inserted into an inner end portion of the motor shaft which is rotatable in the interior of the motor housing and moves the rack bar, a lock screw engaged to a portion of the motor shaft for thereby closely contacting the ball nut to the inner portion of the motor shaft, a groove formed in a rear portion of the lock screw, and a stop ring inserted into the groove and supporting the rear portion of the lock screw.
REFERENCES:
patent: 3938589 (1976-02-01), Mott
patent: 4724711 (1988-02-01), Sakakibara et al.
patent: 4898258 (1990-02-01), Ohe et al.
patent: 5927429 (1999-07-01), Sugino et al.
patent: 5957236 (1999-09-01), Kitazawa et al.
patent: 5988311 (1999-11-01), Kuribayashi et al.
Coleman Henry
Mando Corporation
Sapone William
Sudol R. Neil
Zeender F.
LandOfFree
Electronic power steering apparatus for vehicle does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electronic power steering apparatus for vehicle, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electronic power steering apparatus for vehicle will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2884633