U.S. patent application number 09/742087 was filed with the patent office on 2001-07-05 for electric power steering apparatus.
Invention is credited to Maekawa, Tomohiro.
Application Number | 20010006130 09/742087 |
Document ID | / |
Family ID | 18491519 |
Filed Date | 2001-07-05 |
United States Patent
Application |
20010006130 |
Kind Code |
A1 |
Maekawa, Tomohiro |
July 5, 2001 |
Electric power steering apparatus
Abstract
An electric power steering apparatus comprises a housing 22b for
housing rotatably a steering shaft 18 interlocked with a steering
wheel (not shown), an electric motor 8a which has a through hole 50
through which a screw member 53 is to be inserted and is attached
to the housing 22b by the screw member 53 through the through hole
50, and a gear mechanism 57, 57a, connected to the electric motor
8a through a joint 55, for transmitting a torque of the electric
motor 8a to the steering shaft 18. The joint 55 is formed by a
synthetic resin so as to detach the electric motor 8a from the
housing 22b by an impact force in an axial direction of the
steering shaft 18. 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, it is possible to sufficiently absorb the impact force
of the secondary collision.
Inventors: |
Maekawa, Tomohiro; (Osaka,
JP) |
Correspondence
Address: |
BIRCH, STEWART, KOLASCH & BIRCH, LLP
P.O. Box 747
Falls Church
VA
22040-0747
US
|
Family ID: |
18491519 |
Appl. No.: |
09/742087 |
Filed: |
December 22, 2000 |
Current U.S.
Class: |
180/442 |
Current CPC
Class: |
B62D 1/195 20130101;
B62D 5/0409 20130101; B62D 1/192 20130101 |
Class at
Publication: |
180/442 |
International
Class: |
B62D 005/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 24, 1999 |
JP |
11-368317 |
Claims
1. An electric power steering apparatus, 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 said housing by
said screw member through said through hole; and a gear mechanism,
connected to said electric motor through a joint, for transmitting
a torque of said electric motor to said steering shaft, wherein in
order to detach said electric motor from said housing by an impact
force in an axial direction of said steering shaft, said through
hole has a notch, and said joint is formed by a synthetic
resin.
2. The electric power steering apparatus as set forth in claim 1,
wherein in order to detach said electric motor from said housing by
an impact force in an axial direction of said steering shaft, said
notch is open from said through hole in an opposite direction to
said steering wheel.
3. An electric power steering apparatus, 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 said housing by said screw member through
said through hole; and a gear mechanism, connected to said electric
motor through a joint, for transmitting a torque of said electric
motor to said steering shaft, wherein in order to detach said
electric motor from said housing by an impact force in an axial
direction of said steering shaft, said through hole has a notch,
and said positioning member and joint are formed by a synthetic
resin.
4. The electric power steering apparatus as set forth in claim 2,
wherein in order to detach said electric motor from said housing by
an impact force in an axial direction of said steering shaft, said
notch is open from said through hole in an opposite direction to
said steering wheel.
5. An electric power steering apparatus, comprising: a housing
having at least two engaging grooves, for housing rotatably a
steering shaft interlocked with a steering wheel; an electric motor
which has at least two engaging grooves provided at positions
corresponding to said at least two grooves of said housing, is
positioned by a positioning member and attached to said housing by
engaging tightly respective end portions of at least two curved
elastic members with the respective said at least two engaging
grooves of said housing and said at least two engaging grooves
thereof; and a gear mechanism, connected to said electric motor
through a joint, for transmitting a torque of said electric motor
to said steering shaft, wherein in order to detach said electric
motor from said housing by an impact force in an axial direction of
said steering shaft, a part or all of said engaging grooves of said
electric motor are open in a predetermined direction, and said
positioning member and joint are formed by a synthetic resin.
6. An electric power steering apparatus comprising an electric
motor attached to a housing for housing rotatably a steering shaft
interlocked with a steering wheel, by a screw member; through a
through hole and a gear mechanism, connected to said electric motor
through a joint, for transmitting a torque of said electric motor
to said steering shaft, wherein in order to detach said electric
motor from said housing by an impact force in an axial direction of
said steering shaft, said screw member and joint are formed by a
synthetic resin.
Description
BACKGROUND OF THE INVENTION
[0001] 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.
[0002] 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.
[0003] 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.
[0004] 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.
[0005] 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.
[0006] 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.
[0007] 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.
[0008] 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.
[0009] 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.
[0010] 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
[0011] An object of the present invention is to provide an electric
power steering apparatus capable of solving the above problem.
[0012] 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.
[0013] 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.
[0014] 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.
[0015] 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.
[0016] 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.
[0017] 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.
[0018] The electric power steering apparatus according to the
second and fourth inventions, in the first and third inventions, in
order to detach the electric motor from the housing by an impact
force in an axial direction of the steering shaft, the notch is
open from the through hole in an opposite direction to the steering
wheel.
[0019] The electric power steering apparatus according to the
second and fourth inventions, in the first and third inventions,
since the notch is open from the through hole in the opposite
direction to the steering wheel, 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, the electric motor is detached relatively from
the housing in the direction of the steering wheel by the impact
force of the primary collision or secondary collision. Therefore,
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.
[0020] An electric power steering apparatus according to the fifth
invention, comprising: a housing having at least with two engaging
grooves, for housing rotatably a steering shaft interlocked with a
steering wheel; an electric motor which has at least two engaging
grooves provided at positions corresponding to the at least two
grooves of the housing, is positioned by a positioning member and
attached to the housing by engaging tightly respective end portions
of at least two curved elastic members with the respective at least
two engaging grooves of the housing and thereof; 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, a part
or all of the engaging grooves of the electric motor are open in a
predetermined direction, and the positioning member and joint are
formed by a synthetic resin.
[0021] In this electric power steering apparatus according to the
fifth invention, the housing houses rotatably the steering shaft
interlocked with the steering wheel and has at least two engaging
grooves; and the electric motor has at least two engaging grooves
provided at positions corresponding to the at least two grooves of
the housing, is positioned by the positioning member and attached
to the housing by engaging tightly respective end portions of at
least two curved elastic members with the respective two grooves of
the housing and thereof. The gear mechanism is connected to the
electric motor through the joint and transmits the torque of the
electric motor to the steering shaft. A part or all of the engaging
grooves of the electric motor are open in a predetermined
direction, and the positioning member and joint are formed by a
synthetic resin that is more easily broken than a metal. Therefore,
when an impact force in an axial direction of the steering shaft is
applied, a part or all of the end portions of the elastic members
are disengaged in the open direction of the engaging grooves, while
the positioning member and joint to be obstacles to the
disengagement of the end portions are broken, so that the electric
motor is detached from the housing.
[0022] With this structure, even when parts such as a transmission
attached to a vehicle body go down and are caught on the electric
motor during the primary collision, the electric motor is detached
from the housing in the opposite direction to the steering wheel by
the impact force of the primary collision. Consequently, the
vehicle body can deform sufficiently and absorb the impact force of
the primary collision sufficiently, and the position of the
electric motor can be easily determined in incorporating it into
the vehicle body.
[0023] An electric power steering apparatus according to the sixth
invention, comprising an electric motor attached to a housing for
housing rotatably a steering shaft interlocked with a steering
wheel, by a screw member through a 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
screw member and joint are formed by a synthetic resin.
[0024] In this electric power steering apparatus according to the
sixth invention, the electric motor is attached to the housing for
housing rotatably the steering shaft interlocked with the steering
wheel, by a screw member through a 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.
Since the screw member and joint are formed by a synthetic resin,
when an impact force in an axial direction of the steering shaft is
applied, the screw member and joint are broken; and then the
electric motor is detached from the housing.
[0025] 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 housing and steering shaft can
sufficiently absorb the impact force of the primary collision or
secondary collision, the position of the electric motor can be
easily determined in incorporating it into the vehicle body.
[0026] The above and further objects and features of the invention
will more fully be apparent from the following detailed description
with accompanying drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0027] FIG. 1 is a depiction showing a state in which an electric
power steering apparatus according to the present invention is
mounted on a vehicle body;
[0028] FIG. 2 is a depiction showing the function of an electric
power steering apparatus according to the present invention;
[0029] FIG. 3 is a depiction showing the function of a conventional
electric power steering apparatus;
[0030] FIG. 4 is a front view showing the structure of an electric
power steering apparatus according to the present invention;
[0031] FIG. 5A is a plan view of an electric motor;
[0032] FIG. 5B is a partial transverse cross-sectional view of the
electric motor and a motor-side cylindrical portion;
[0033] FIG. 6 is a perspective view showing the appearance of a
spacer;
[0034] FIG. 7 is a perspective view showing the appearance of a
joint;
[0035] FIG. 8 is a depiction showing the function of an electric
power steering apparatus according to the present invention;
[0036] FIG. 9 is a front view showing the structure of an
embodiment of an electric power steering apparatus according to the
present invention;
[0037] FIG. 10A is a plan view of an electric motor;
[0038] FIG. 10B is a partial transverse cross-sectional view of the
electric motor and a housing;
[0039] FIG. 11 is a depiction showing a state in which an electric
power steering apparatus according to the present invention is
mounted on a vehicle body; and
[0040] FIG. 12 is a depiction showing the function of an electric
power steering apparatus according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0041] The following description will explain the present invention
with reference to the drawings illustrating the embodiments
thereof.
[0042] Embodiment 1
[0043] FIG. 4 is a front view showing the structure of an electric
power steering apparatus according to the present invention. This
electric power steering apparatus is of a so-called column assist
type, and comprises a steering shaft 1 whose one end portion is
interlocked with a steering wheel 100 for steering; a housing 2 for
housing and supporting the steering shaft 1 rotatably; a lower-side
mounting member 3 for mounting a lower-side end portion of the
housing 2 on a vehicle body; an upper-side mounting member 4 for
mounting a center portion of the housing 2 in a longitudinal
direction on the vehicle body; and a steering assisting electric
motor 8a which is driven and controlled based on a steering torque
applied to the steering shaft 1.
[0044] The housing 2 includes a cylindrical pipe portion 21 and a
formed cylindrical portion 22 connected to the pipe portion 21 by
press-fitting an end portion of the pipe portion 21 into the formed
cylindrical portion 22, and the upper-side mounting member 4 is
attached to a center portion of the pipe portion 21 in an axial
direction. The formed cylindrical portion 22 includes a sensor-side
cylindrical portion 22a housing a torque sensor (not shown) for
detecting a steering torque applied to the steering shaft 1 and a
motor-side cylindrical portion 22b connected to the electric motor
8a. These sensor-side cylindrical portion 22a and motor-side
cylindrical portion 22b are coupled together by a plurality of
fastening screws 23.
[0045] The motor-side cylindrical portion 22b has a plurality of
mounting holes formed at equal intervals in a circumferential
direction in the surface of its one end portion on the opposite
side to the sensor-side cylindrical portion 22a. Moreover, one side
of the motor-side cylindrical portion 22b to be connected to the
electric motor 8a is made a flange portion 22c to be joined to a
flange portion 8b of the electric motor 8a.
[0046] In the lower-side mounting member 3, one side plate portion
of a metallic plate bent in an L-shape is formed as mounting pieces
31 having mounting holes 30, 30 for mounting on the vehicle body
104, and the other side plate portion is made a ring-shaped fixed
portion 32 to be fixed to an end portion of the motor-side
cylindrical portion 22b of the housing 2. The fixed portion 32 has
a plurality of through holes corresponding to the above-mentioned
mounting holes 30, 30 of the motor-side cylindrical portion 22b,
which are formed at equal intervals in a circumferential direction,
and is attached to the formed cylindrical portion 22 by tightly
screwing mounting screws 34 inserted through these through holes
into the mounting holes 30, 30.
[0047] The formed cylindrical portion 22 houses therein an input
shaft (second steering shaft: not shown) coupled to the other end
portion of the steering shaft (first steering shaft) 1, a torsion
bar (not shown) whose one end portion is coupled to the input
shaft, and an output shaft (third steering shaft) 18 (see FIG. 5B)
coupled to the other end portion of the torsion bar.
[0048] The steering shaft 1 and housing 2 are respectively divided
into a plurality of parts in the axial direction, and the divided
parts have a structure fitting to each other to keep the positional
relationship 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 the above-mentioned
fitting structures overlap each other more deeply, and absorb the
impact force.
[0049] Regarding the mounting piece 31 of the lower-side mounting
member 3, a pair of the mounting pieces 31 are positioned
separately, and the above-mentioned mounting holes 30, 30, each
having a notch on its one side, are formed in these mounting pieces
31. Impact force absorbing portions 39, 39 having a notched groove
portion are formed between the base portion and the mounting holes
30, 30 of the respective mounting pieces 31, 31, so that, when an
impact force is applied from the driver to the steering wheel 100
due to a head-on collision of a vehicle, etc., the impact force
absorbing portions 39, 39 are deformed to absorb the impact
force.
[0050] The upper-side mounting member 4 is formed by a metallic
plate in a grooved shape, and includes a U-shaped fixed piece 41 to
be attached to the housing 2 and a pair of mounting pieces 42 which
are bent at right angles from one end portion and the other end
portion of the fixed piece 41, respectively, and are to be attached
to the vehicle body 104. The mounting pieces 42 have notched groove
portions extending in the axial direction of the housing 2,
respectively, and hold in the notched groove portions first spacers
43, 43 which are made of a metal such as aluminum and have bolt
holes 43a and second spacers 45, 45 which are made of a synthetic
resin and have impact force absorbers, respectively, so as to fix
the mounting member 4 to the vehicle body 104 by bolts inserted
through the bolt holes 43a, 43a of the first spacers 43, 43.
[0051] In this fixed state, when the housing 2 is pushed in an
axial direction via the steering shaft 1 and its bearing by an
impact force applied from the driver to the steering wheel 100 due
to a head-on collision of the vehicle, etc., the impact force
absorbers of the second spacers 45 are broken and the upper-side
mounting member 4 slides with respect to the first spacers 43, 43,
thereby absorbing the impact force.
[0052] FIG. 5A is a plan view of the electric motor 8a, and FIG. 5B
is a partial transverse cross-sectional view of the electric motor
8a and the motor-side cylindrical portion 22b.
[0053] The motor-side cylindrical portion 22b houses therein a worm
wheel 57a fixed to the outer circumference of the output shaft 18
by fitting, a worm 57 meshing with the worm wheel 57a, and ball
bearings 58, 59 engaged in one side and the other side of the worm
57 in the axial direction, respectively.
[0054] In the flange portion 8b of the electric motor 8a, notches
50a are formed in the through holes 50, 50 for screwing bolts
(screw members) 53, 53 into screw holes 60, 60 formed in the flange
portion 22c of the motor-side cylindrical portion 22b,
respectively, so that, when an impact force is applied from the
driver to the steering wheel 100 due to a head-on collision of a
vehicle, etc, the electric motor 8a is detached from the flange
portion 22c of the motor-side cylindrical portion 22b in the
direction of arrow B (the upper side direction of the housing
2).
[0055] In the through holes 50, 50, the bolts 53, 53 are wound by
metallic pipes 51, 51 made of aluminum, etc., and are held and
fixed in the spacers 52, 52 formed by a synthetic resin or rubber
in the state in which the bolts 53, 53 are wound by the metallic
pipes 51, 51.
[0056] As shown in FIG. 6, the spacer 52 is formed in a cylindrical
shape having a flange portion 52a in one end portion of the
cylinder, and provided with a slit 52b cut across both end portions
thereof so as to ease the detachment of the bolt 53.
[0057] An end potion 56 of the rotating shaft of the electric motor
8a is formed in a square plate shape, and an end portion on one
side of the worm 57 in the axial direction is formed in a square
column shape. These end portions are connected to each other by
fitting them into holes formed in both bottom surfaces of a joint
55 formed by a synthetic resin, respectively.
[0058] As shown in FIG. 7, the joint 55 is formed in a cylindrical
shape with a hole 55a into which the end portion 56 of the rotating
shaft of the electric motor 8a is to be fitted, at the center of
one of the bottom surfaces; a hole 55b into which the end portion
on one side of the worm 57 in the axial direction is to be fitted,
at the center of the other bottom surface; and a notching portion
55c formed along a circumferential surface in the vicinity of the
center of a side surface. The joint 55 can adjust its strength by
adjustment of the depth of the notching portion 55c and the
material.
[0059] The flange portion 8b of the electric motor 8a and the
flange portion 22c of the motor-side cylindrical portion 22b
respectively have holes formed at two opposite positions in their
mutually facing surface, and mutual positioning is carried out by
fitting pins 54, 54 (positioning members) formed by a synthetic
resin into the respective holes.
[0060] FIG. 1 is a depiction showing a state in which an electric
power steering apparatus having such a structure is mounted on a
vehicle body 104. This 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 on a vehicle body 104,
and is disposed inside the compartment 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.
[0061] In this electric power steering apparatus, on the lower side
of the housing 2, an electric motor 8a is disposed in the vicinity
of the mounting member 3 and a joint 106 for connecting the
steering shaft 1 and a steering mechanism is positioned to pass
through a dash panel 107 of the vehicle body 104.
[0062] In such an electric power steering apparatus, in the event
of occurrence 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 wheel 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.
[0063] In the case where the mounting member 3 is detached and then
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, etc.
belonging to the vehicle body 104 may be caught on the electric
motor 8a.
[0064] In this case, the through holes 50, 50 of the flange portion
8b of the electric motor 8a can not hold the bolts 53, 53 against
the impact force of the secondary collision because of the presence
of the notches 50a.
[0065] Moreover, at this time, the joint 55 and the positioning
pins 54, 54 are broken by the impact force of the secondary
collision because they are formed by a synthetic resin that is more
easily broken than a metal.
[0066] Therefore, there is no means to keep the positional
relationship between the electric motor 8a and the housing 2, and
consequently the electric motor 8a is detached from the flange
portion 22c of the motor-side cylindrical portion 22b in the upper
side direction of the housing 2.
[0067] Hence, as shown in FIG. 8, since the housing 2 can move to
the lower side while leaving the electric motor 8a caught on a
portion of the vehicle body 104 and the mounting member, etc.
belonging to the vehicle body 104 at that position, the steering
shaft 1 and housing 2 can shrink sufficiently in an axial
direction, thereby satisfactorily absorbing the impact force of the
secondary collision.
[0068] Besides, the same effect can be obtained by using the bolts
53, 53 made of a synthetic resin instead of forming the notches 50a
in the through holes 50, 50 of the flange portion 8b of the
electric motor 8a. In other words, if the bolts 53, 53 made of a
synthetic resin are broken by the impact force of the secondary
collision, the positional relationship between the electric motor
8a and housing 2 can not be retained, and consequently the electric
motor 8a is detached from the flange portion 22c of the motor-side
cylindrical portion 22b toward the upper side of the housing 2.
[0069] Embodiment 2
[0070] FIG. 9 is a front view showing the structure of Embodiment 2
of an electric power steering apparatus according to the present
invention. FIG. 10A is a plan view of the electric motor 8c, and
FIG. 10B is a partial transverse cross-sectional view of the
electric motor 8c and housing 122. This electric power steering
apparatus is of a so-called pinion assist type, and comprises a
second steering shaft 101 (input shaft) whose upper end portion is
connected to a steering wheel (not shown) through a first steering
shaft (not shown); a torsion bar (not shown) whose upper end
portion is coaxially connected to the lower end portion of the
second steering shaft 101; a third steering shaft 103 (output
shaft) coaxially connected to the lower end portion of the torsion
bar; and a torque sensor (not shown) for detecting a torque applied
to the third steering shaft 103 and the second steering shaft 101
by rotation of the steering wheel, according to a twist of the
torsion bar, all of which are housed in a housing 122.
[0071] The housing 122 also houses a reduction mechanism (gear
mechanism) for transmitting to the third steering shaft 103 the
rotation of a steering assisting electric motor 8c which is driven
and controlled based on a torque detected by the torque sensor.
This reduction mechanism is composed of a worm 57 for transmitting
the rotation of the electric motor 8c, and a worm wheel which 57a
meshes with the worm 57 and is fixed to the outer circumference of
the third steering shaft 103 by fitting.
[0072] With this structure, the steering mechanism 121 operates
with the rotation of the third steering shaft 103, and the
operation of the steering mechanism 121 corresponding to the
rotation of the steering wheel is assisted by the rotation of the
electric motor 8c, thereby reducing the driver's labor for
steering.
[0073] The electric motor 8c is coupled to the housing 122 by
fastening a flange portion 8d of the electric motor 8c and a flange
portion 123 provided in the housing 122 by two substantially
C-shaped springs 61 (elastic members) as to be described later.
[0074] The steering mechanism 121 includes a pinion (not shown)
attached to the lower end portion of the third steering shaft 103,
a rack shaft (not shown) which is extended in the right and left
directions at the front portion of the vehicle body and meshes with
the pinion, a rack housing 126 for housing the rack shaft and a
pair of bellows 127, 127 for sealing the space between both end
portions of the rack shaft.
[0075] The housing 122 houses the above-mentioned torque sensor and
reduction mechanism, and also supports the second steering shaft
101 and third steering shaft 103 rotatably.
[0076] The housing 122 houses the worm wheel 57a fixed to the outer
circumference of the above-mentioned third steering shaft 103 by
fitting, the worm 57 meshing with the wham wheel 57a, and ball
bearings 58, 59 fitted on one side and the other side of the worm
57 in the axial direction, respectively.
[0077] Two engaging grooves 62, 62 and two engaging grooves 63, 63
are formed at mutually corresponding positions in the flange
portion 8d of the electric motor 8c and the flange portion 123 of
the housing 122, respectively. The electric motor 8c and housing
122 are coupled together by engaging tightly the respective end
portions of the two substantially C-shaped springs 61 (elastic
members) with the respective two engaging grooves 62, 63. Note that
respective number of engaging grooves 62, engaging grooves 63 and
C-shaped springs 61 may be equal to three or more.
[0078] Each of the engaging grooves 62 of the flange portion 8d of
the electric motor 8c has an open end portion 64 which is open in
the direction of the steering wheel. Therefore, even when parts
attached to a vehicle body such as a transmission go down and are
caught on the electric motor 8c due to a head-on collision of a
vehicle, etc., the electric motor 8c is detached from the flange
portion 123 of the housing 122 by the impact force.
[0079] The end potion 56 of the rotating shaft of the electric
motor 8c is formed in a square plate shape, and an end portion of
one side of the worm 57 in the axial direction is formed in a
square column shape. These end portions are connected to each other
by fitting them into holes formed in both bottom surfaces of a
joint 55 formed by a synthetic resin, respectively.
[0080] Since the joint 55 is the same as that explained in
Embodiment 1 and illustrated in FIG. 7, the explanation thereof is
omitted.
[0081] The flange portion 8d of the electric motor 8c and the
flange portion 123 of the housing 122 respectively have holes
formed at two opposite positions in their mutually facing surfaces.
Their mutual positions are determined by fitting the pins 54, 54
(positioning members) formed by a synthetic resin into the holes,
respectively.
[0082] FIG. 11 is a depiction showing a state in which the electric
power steering apparatus having such a structure is mounted on a
vehicle body. According to this depiction, in the electric power
steering apparatus, a first steering shaft 111 is connected to a
steering wheel 100, and a housing 2 houses the first steering shaft
111 rotatably. The lower-side end portion of the first steering
shaft 111 and the upper end portion of a second steering shaft 101
are connected by a joint 106; the housing 122 houses the
above-mentioned torsion bar, third steering shaft 103, torque
sensor and the reduction mechanism of the electric motor 8c; and
the electric motor 8c is coupled to the housing 122 so that the
direction of its rotating shaft and the direction of the third
steering shaft 103 housed in the housing 122 cross at right
angles.
[0083] The above-mentioned rack housing 126 housing the rack shaft
is extended in the right and left directions at the front portion
of the vehicle body so as to cross the housing 122.
[0084] In such an electric power steering apparatus, when a head-on
collision of a vehicle occurs, parts 128 attached to the vehicle
body such as a transmission may go down and be caught on the
electric motor 8c due to the impact force of the primary
collision.
[0085] In this case, the end portions of the springs 61 coupling
the electric motor 8c and housing 122 together are disengaged from
the open end portions 64 of the engaging grooves 62, while the
joint 55 and the positioning pins 54, 54 are broken by the impact
force of the secondary collision because they are formed by a
synthetic resin that is broken more easily than a metal. Therefore,
the electric motor 8c is detached from the flange portion 123 of
the housing 122 in the lower side direction of the housing 122.
[0086] Thus, as shown in FIG. 12, since the parts 128 such as a
transmission can go down sufficiently together with the electric
motor 8c, the vehicle body can deform sufficiently and absorb the
impact force sufficiently.
[0087] Additionally, the open end portions 64 may be formed in
either the two engaging grooves 62 in the flange portion 8d of the
electric motor 8c or the two engaging grooves 63 in the flange
portion 123 of the housing 122. However, in the case where the open
end portions 64 are formed in the two engaging grooves 62 in the
flange portion 8d, as described above, the open end portions 64
should be open in the direction of the steering wheel. On the other
hand, when the open end portions 64 are formed in the two engaging
grooves 63 in the flange portion 123, the open end portions 64
should be open in the opposite direction to the steering wheel.
[0088] As this invention may be embodied in several forms without
departing from the spirit of essential characteristics thereof, the
present embodiments are therefore illustrative and not restrictive,
since the scope of the invention is defined by the appended claims
rather than by the description preceding them, and all changes that
fall within metes and bounds of the claims, or equivalence of such
metes and bounds thereof are therefore intended to be embraced by
the claims.
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