Land vehicles – Wheeled – Running gear
Reexamination Certificate
2000-12-22
2002-08-13
Mai, Lanna (Department: 3619)
Land vehicles
Wheeled
Running gear
C180S443000, C180S444000
Reexamination Certificate
active
06431601
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an electric power steering apparatus which is disposed in a housing rotatably a steering shaft interlocked with a steering wheel and comprises an electric motor for supplying a torque to the steering shaft.
As a power steering apparatus for a vehicle, there has been known, for example, an electric power steering apparatus including in a housing, which houses rotatably a steering shaft interlocked with a steering wheel, an electric motor for supplying a torque to the steering shaft.
In the case where the electric power steering apparatus is of a so-called column assist type, as shown in a depiction of
FIG. 1
illustrating a state in which the electric power steering apparatus is mounted on a vehicle body, the electric power steering apparatus comprises a steering shaft
1
connected to a steering wheel
100
; a housing
2
for housing the steering shaft
1
rotatably; and a mounting member
3
for mounting the lower side of the housing
2
to a vehicle body
104
, and is disposed inside the compartment of the vehicle so that the mounting member
3
is attached to the vehicle body
104
and the center portion of the housing
2
is attached to the vehicle body
104
by a mounting member
4
having an impact force absorber for absorbing an impact force of the secondary collision during a collision.
In this electric power steering apparatus, on the lower side of the housing
2
, an electric motor
8
is disposed in the vicinity of the mounting member
3
, and a joint
106
for connecting the steering shaft
1
and a steering mechanism to each other is provided to pass through a dash panel
107
.
In such an electric power steering apparatus, the steering shaft
1
and housing
2
are respectively divided into a plurality of parts in the axial direction, the divided parts have a structure fitting to each other, and their positional relationship is kept by calking, etc. When an impact force of not less than a predetermined value is applied in an axial direction, the steering shaft
1
and housing
2
shrink as their fitting structures overlap more deeply, and absorb the impact force.
Therefore, in the event of a head-on collision of a vehicle, after the primary collision, when the driver collides with the steering wheel
100
(secondary collision) due to a shock of the primary collision and then the impact force is applied to the steering shaft
1
and housing
2
, the steering shaft
1
and housing
2
are pushed in an axial direction and shrink, while the impact force absorber of the mounting member
4
is broken, thereby absorbing the impact force of the secondary collision.
In a conventional electric power steering apparatus as described above, when a head-on collision of a vehicle occurs, if the vehicle body
104
including the dash panel
107
rises due to the impact force of the primary collision, as shown in
FIG. 2
, a portion of the vehicle body
104
and the mounting member
3
, etc. belonging to the vehicle body
104
may be caught on the electric motor
8
.
In this case, since the electric motor
8
is fixedly attached to the housing
2
, as shown in
FIG. 3
, the housing
2
and steering shaft
1
can not shrink to an expected degree during the secondary collision, and thus there is a possibility that the impact force of the secondary collision is not sufficiently absorbed.
Moreover, even in the case of an electric power steering apparatus of a so-called pinion assist type, when parts (not shown) such as a transmission (not shown) attached to a vehicle body
104
go down due to the impact force of the primary collision, they may be caught on an electric motor
8
. Thus, there is a possibility that the vehicle body
104
can not deform sufficiently and the impact force is not absorbed sufficiently.
For these reasons, positioning of the electric motor
8
poses a problem in installing the electric power steering apparatus on the vehicle body.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide an electric power steering apparatus capable of solving the above problem.
An electric power steering apparatus according to the first invention, comprising: a housing for housing rotatably a steering shaft interlocked with a steering wheel; an electric motor which has a through hole through which a screw member is to be inserted and is attached to the housing by the screw member through the through hole; and a gear mechanism, connected to the electric motor through a joint, for transmitting a torque of the electric motor to the steering shaft, wherein in order to detach the electric motor from the housing by an impact force in an axial direction of the steering shaft, the through hole has a notch, and the joint is formed by a synthetic resin.
In this electric power steering apparatus according to the first invention, the housing houses rotatably the steering shaft interlocked with the steering wheel; the electric motor has the through hole through which the screw member is to be inserted and is attached to the housing by the screw member through the through hole; and the gear mechanism is connected to the electric motor through the joint and transmits the torque of the electric motor to the steering shaft. The electric motor has the notch in the through hole though which the screw member is to be inserted, and the joint is formed by a synthetic resin. Therefore, when an impact force in an axial direction of the steering shaft is applied, the screw member passes through the notch and comes out of the through hole, while the joint to be an obstacle to the screw member coming out of the through hole is broken, so that the electric motor is detached from the housing.
With this structure, even when a portion of a vehicle body and a mounting bracket, etc. belonging to the vehicle body are caught on the electric motor during the primary collision or secondary collision, since the electric motor is detached from the housing by the impact force of the primary collision or secondary collision, the housing and steering shaft can sufficiently absorb the impact force of the secondary collision, and the position of the electric motor can be easily determined in incorporating it into the vehicle body.
An electric power steering apparatus according to the third invention, comprising: a housing for housing rotatably a steering shaft interlocked with a steering wheel; an electric motor which has a through hole through which a screw member is to be inserted, is positioned by a positioning member and attached to the housing by the screw member through the through hole; and a gear mechanism, connected to the electric motor through a joint, for transmitting a torque of the electric motor to the steering shaft, wherein in order to detach the electric motor from the housing by an impact force in an axial direction of the steering shaft, the through hole has a notch, and the positioning member and joint are formed by a synthetic resin.
In this electric power steering apparatus according to the third invention, the housing houses rotatably the steering shaft interlocked with the steering wheel; the electric motor has the through hole through which the screw member is to be inserted, is positioned by the positioning member and attached to the housing by the screw member through the through hole; and the gear mechanism is connected to the electric motor through the joint and transmits the torque of the electric motor to the steering shaft. The electric motor has the notch in the through hole though which the screw member is to be inserted, and the positioning member and joint are formed by a synthetic resin that is broken more easily than a metal. Therefore, when an impact force in an axial direction of the steering shaft is applied, the screw member passes through the notch and comes out of the through hole, while the positioning member and joint to be obstacles to the screw member coming out of the through hole are broken, so that the electric motor is detached from the housing.
With this structure, even when a portion
Koyo Seiko Co. Ltd.
Mai Lanna
Royal, Jr. Paul
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