U.S. patent application number 10/519485 was filed with the patent office on 2005-10-20 for motor power steering system.
Invention is credited to Chikaraishi, Kazuo, Endo, Shuji, Onizuka, Toshiyuki.
Application Number | 20050230178 10/519485 |
Document ID | / |
Family ID | 30112325 |
Filed Date | 2005-10-20 |
United States Patent
Application |
20050230178 |
Kind Code |
A1 |
Chikaraishi, Kazuo ; et
al. |
October 20, 2005 |
Motor power steering system
Abstract
The present invention relates to a motor-driven power steering
apparatus structured such as to apply a steering assist force
generated by a motor to a steering system of a motor vehicle or a
vehicle in accordance with a rotation force of an electric motor on
the basis of a steering torque detected by a torque sensor.
Further, the invention relates to a rotation angle sensor for
detecting a rotation angle of a steering shaft, a detected portion
of the rotation angle sensor is provided within the speed reduction
gear, and a detecting portion of the rotation angle sensor is
provided in a radial direction of the steering shaft and in an
outer side of a bearing in the speed reduction gear.
Inventors: |
Chikaraishi, Kazuo; (Gunma,
JP) ; Onizuka, Toshiyuki; (Gunma, JP) ; Endo,
Shuji; (Gunma, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Family ID: |
30112325 |
Appl. No.: |
10/519485 |
Filed: |
December 30, 2004 |
PCT Filed: |
April 18, 2003 |
PCT NO: |
PCT/JP03/05001 |
Current U.S.
Class: |
180/444 ;
324/207.25 |
Current CPC
Class: |
B62D 15/0215 20130101;
B62D 5/0409 20130101; Y10T 74/19888 20150115; G01L 5/221
20130101 |
Class at
Publication: |
180/444 ;
324/207.25 |
International
Class: |
B62D 005/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 3, 2002 |
JP |
2002-195042 |
Claims
What is claimed is:
1. A motor-driven power steering apparatus structured such as to
assist a steering force of a steering shaft via a transmission
mechanism such as a gear of a speed reduction gear or the like by a
rotation force of an electric motor on the basis of a steering
torque detected by a torque sensor, comprising: a rotation angle
sensor for detecting a steering state of a steering wheel, wherein
a detected portion of said rotation angle sensor is provided within
said speed reduction gear, and a detecting portion of said rotation
angle sensor is provided in a radial direction of said steering
shaft and in an outer side of a bearing in said speed reduction
gear.
2. A motor-driven power steering apparatus as claimed in claim 1,
wherein said detected portion is arranged in a worm wheel within
said speed reduction gear, and the rotation of said worm wheel is
detected by said detecting portion.
3. A motor-driven power steering apparatus as claimed in claim 1,
wherein said detecting portion is mounted to a recess groove formed
in any one side within the worm wheel within said speed reduction
gear.
4. A motor-driven power steering apparatus as claimed in claim 1,
wherein said detecting portion is arranged at a position opposing
to a side surface of said detected portion, thereby detecting a
magnetic or optical angle signal from said detected portion.
5. A motor-driven power steering apparatus as claimed in claim 1,
wherein said detected portion is structured by a recess groove
formed in any one side within the worm wheel within said speed
reduction gear, and is constituted by a small gear provided in an
inner peripheral surface of said recess groove.
6. A motor-driven power steering apparatus as claimed in claim 1,
wherein said rotation angle sensor is constituted by an annular
detected portion provided in the side surface of the worm wheel
within said speed reduction gear, and a detecting portion provided
at a position opposing to said detected portion.
7. A motor-driven power steering apparatus as claimed in claim 1,
wherein said speed reduction gear is supported by a plurality of
bearings.
Description
TECHNICAL FIELD
[0001] The present invention relates to a motor-driven power
steering apparatus structured such as to apply a steering assist
force generated by a motor to a steering system of a motor vehicle
or a vehicle, and more particularly to a rotation angle sensor for
detecting a rotation angle (a steering angle) of a steering
shaft.
BACKGROUND ART
[0002] In order to reduce a fatigue of a driver and safely drive, a
motor-driven power steering apparatus is generally mounted on the
vehicle. The motor-driven power steering apparatus is structured
such as to assist a load of the steering shaft and energize via a
transmission mechanism such as a gear of a speed reduction gear or
the like on the basis of a driving force of the motor.
[0003] As a conventional motor-driven power steering apparatus, an
outline structure of the steering system is generally shown in FIG.
1. In the drawing, a steering shaft 1 having a steering wheel in a
leading end (a right end in FIG. 1) is rotatably supported by a
ball bearing 3 within a coaxial steering column 2, and is extended
in an axial direction. The steering shaft 1 is constituted by a
tubular outer shaft 4, and an inner shaft 5 fitted within the outer
shaft 4. Further, the steering column 2 is formed by connecting a
tubular outer column 6 and an inner column 7 press fitted and fixed
within the outer column 6. Further, when an impact load is applied
in a compression direction at a time of colliding, the outer shaft
4 and the outer column 6 are pressed into a base end side (a left
side in FIG. 1), absorbs an energy by contracting an entire length
and absorbs an impact applied to a body of the driver colliding
with the steering wheel.
[0004] Further, an input shaft 9 and an approximately tubular
output shaft 10 are connected to the base end side (the left side
in FIG. 1) of the inner shaft 5 via a torsion bar 8. The torsion
bar 8 is inserted into the output shaft 10, one end of the torsion
bar 8 is press fitted and fixed to the input shaft 9, and the other
end thereof is fixed to the output shaft 10 by a pin 11.
[0005] Further, a speed reduction gear unit 12 is supported to an
outer periphery of a center portion of the output shaft 10 by a
pair of ball bearings 13 and 13. The speed reduction gear unit 12
is constituted by a worm wheel 14 fixedly mounted to an outer
periphery of the output shaft 10 in accordance with a press
fitting, a worm 15 engaging with the worm wheel 14, and a motor in
which the worm 15 is mounted to an output shaft 16, and is
structured such as to reduce a speed of rotation of the motor via
the worm 15 and the worm wheel 14 so as to transmit a torque, on
the basis of driving the motor.
[0006] Further, a torque sensor 17 is arranged in a leading end
side (a right side in FIG. 1) of the speed reduction gear unit 12,
and the torque sensor 17 is provided with the torsion bar 8 and an
electromagnetic yoke 20 receiving a coil winding 19 in an outer
periphery of a spline groove 18 formed in a leading end of the
output shaft 10, and is structured such as to detect a magnetic
change by the coil winding 19 within the electromagnetic yoke 20,
by generating a torsion angle in correspondence to a torque
generated in the steering shaft 1.
[0007] Further, a rotation angle sensor (a steering sensor) 21 is
arranged in a base end side (a left side in FIG. 1) of the speed
reduction gear unit 12, and the rotation angle sensor 21 is
constituted by a tubular hollow member 22 arranged in an outer
periphery of the output shaft 10, and a casing 23 rotatably
supporting the hollow member 22. In this case, in the hollow member
22, a projection 24 is extended to an inner side from an inner
peripheral surface, and is engaged with a locking hole 25 provided
in an outer peripheral surface of the output shaft 10, whereby the
hollow member 22 is integrally rotated with the output shaft 10.
Accordingly, the structure is made such as to detect the rotation
angle of the output shaft 10 by detecting a relative displacement
between the casing 23 and the hollow member 22 by a detecting means
26 provided in the casing 23. Accordingly, the steering state of
the steering wheel is detected from the rotation angle (the
steering angle).
[0008] In this case, reference numeral 27 denotes a universal joint
for connecting to an intermediate shaft, and reference numeral 28
denotes a bracket for mounting the steering apparatus to the
vehicle body.
[0009] In this case, in order to protect a passenger at a time when
the vehicle is collided, it is necessary that an energy absorbing
mechanism is provided in the steering column 2 for the regulation
or the safety. Accordingly, in the conventional structure mentioned
above, the steering shaft 1 and the steering column 2 are
respectively constituted by two members (the outer shaft 4 and the
inner shaft 5, and the outer column 6 and the inner column 7), and
the outer shaft 4 and the outer column 6 can be moved at a certain
range (a stroke t) in the axial direction at a time of collision.
Therefore, the steering column 2 or the like is plastically
deformed at a time of moving, and it is possible to absorb the
energy generated at a time when the passenger collides with the
steering wheel, on the basis of the deformation energy.
[0010] In this case, since the absorbing amount of the energy is
determined by a product of a force applied by the impact and the
stroke t, it is important to make the stroke t as long as possible
in order to make the impact force to the passenger small so as to
reduce an injury.
[0011] However, in the column type motor-driven power steering
apparatus, it is necessary that the speed reduction gear and the
torque sensor 17 are provided in the axial direction of the
steering shaft 1, and it is necessary that the rotation angle
sensor 21 is provided so as to have such a space that the steering
shaft, that is, the output shaft 10 is exposed between the
universal joint 27 and the speed reduction unit 12. Accordingly,
the stroke t is limited to a fixed length from the space of the
vehicle body, and there is a problem that it is hard to secure the
stroke t of the energy absorbing mechanism to a sufficient length
in the limited space.
[0012] Accordingly, an object of the present invention is to
provide a motor-driven power steering apparatus in which a rotation
angle sensor can be attached to a steering shaft in the limited
space without deteriorating an energy absorbing function for
protecting the passenger.
DISCLOSURE OF THE INVENTION
[0013] The object mentioned above of the present invention can be
effectively achieved by a motor-driven power steering apparatus
structured such as to assist a steering force of a steering shaft
via a transmission mechanism such as a gear of a speed reduction
gear or the like by a rotation force of an electric motor on the
basis of a steering torque detected by a torque sensor,
comprising:
[0014] a rotation angle sensor for detecting a steering state of a
steering wheel,
[0015] wherein a detected portion of the rotation angle sensor is
provided within the speed reduction gear, and a detecting portion
of the rotation angle sensor is provided in a radial direction of
the steering shaft and in an outer side of a bearing in the speed
reduction gear.
[0016] Further, the object mentioned above can be effectively
achieved by the structure in which the detected portion is arranged
in a worm wheel within the speed reduction gear, and the rotation
of the worm wheel is detected by the detecting portion.
[0017] Further, the object mentioned above can be effectively
achieved by the structure in which the detecting portion is mounted
to a recess groove formed in any one side within the worm wheel
within the speed reduction gear.
[0018] Further, the object mentioned above can be effectively
achieved by the structure in which the detecting portion is
arranged at a position opposing to a side surface of the detected
portion, thereby detecting a magnetic or optical angle signal from
the detected portion.
[0019] Further, the object mentioned above can be effectively
achieved by the structure in which the detected portion is
structured by a recess groove formed in any one side within the
worm wheel within the speed reduction gear, and is constituted by a
small gear provided in an inner peripheral surface of the recess
groove.
[0020] Further, the object mentioned above can be effectively
achieved by the structure in which the rotation angle sensor is
constituted by an annular detected portion provided in the side
surface of the worm wheel within the speed reduction gear, and a
detecting portion provided at a position opposing to the detected
portion.
[0021] Further, the object mentioned above can be effectively
achieved by the structure in which the speed reduction gear is
supported by a plurality of bearings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a cross sectional view showing an outline
structure of a conventional motor-driven power steering
apparatus;
[0023] FIG. 2 is a cross sectional view showing a structure of a
motor-driven power steering apparatus in accordance with a first
embodiment of the present invention;
[0024] FIG. 3 is a schematic view showing a rotation angle sensor
provided in a speed reduction gear unit of the motor-driven power
steering apparatus;
[0025] FIG. 4 is a cross sectional view showing a structure of a
motor-driven power steering apparatus in accordance with a second
embodiment of the present invention;
[0026] FIG. 5 is an enlarged view describing a detecting mechanism
of a rotation angle of an output shaft in accordance with the
second embodiment;
[0027] FIG. 6 is a cross sectional view showing a structure of a
motor-driven power steering apparatus in accordance with a third
embodiment of the present invention; and
[0028] FIG. 7 is a view showing an outline structure of a rotation
angle sensor in accordance with the third embodiment.
DESCRIPTION OF REFERENCE NUMERALS
[0029] 31 steering shaft
[0030] 35 steering column
[0031] 39 torsion bar
[0032] 40 input shaft
[0033] 41 output shaft
[0034] 42 speed reduction gear unit
[0035] 43 bearing
[0036] 44 torque sensor
[0037] 46 coil winding
[0038] 47 electromagnetic yoke
[0039] 48 worm wheel
[0040] 49 worm
[0041] 51 rotation angle sensor
[0042] 52 detected portion
[0043] 53 detecting portion
[0044] 61 core bar boss portion
[0045] 62 gear base portion
[0046] 63 resin gear
[0047] 64 detected portion
[0048] 65 rotation angle sensor
[0049] 67 detecting portion
[0050] 72 detecting gear
MODE FOR CARRYING OUT THE INVENTION
[0051] A description will be given below of embodiments in
accordance with the present invention with reference to the
accompanying drawings.
[0052] FIG. 2 shows a first embodiment of the present invention,
and is a view showing an outline structure of a steering system. A
steering shaft 31 rotating on the basis of an operation of a
steering wheel is connecting by press fitting and fixing a solid
cylindrical shaft-like inner shaft 33 to a tubular outer shaft 32.
Further, the steering shaft 31 is rotatably supported at an end
portion of a steering column 35 by a bearing 34 such as a deep
groove type ball bearing or the like. The steering column 35 is
connected by press fitting and fixing an inner column 37 to a
tubular outer column 36.
[0053] The steering shaft 31 and the steering column 35 are
structured such that when a great load is applied in an axial
direction, the outer shaft 32 moves along the inner shaft 33 and
the outer column 36 moves along the inner column 37 respectively in
the axial direction within a range of the stroke t in the axial
direction so as to be plastically deformed. In other words, the
steering shaft 31 and the steering column 35 are both structured by
combining two members 32 and 33, and 36 and 37, and forms an energy
absorbing mechanism structured such as to absorb an impact applied
to a body of a driver colliding with the steering wheel.
[0054] In this case, in the embodiment mentioned above, the energy
of the steering shaft 31 and the steering column 35 is absorbed by
a plastic deformation at a time of relative movement between two
members, however, it is possible to absorb the energy by the
plastic deformation between the steering column 35 and a bracket 75
for fixing the steering column 35 to the vehicle body.
[0055] Further, an input shaft 40 and an approximately cylindrical
output shaft 41 are connected to a base end side (a left side in
FIG. 1) of the steering shaft 31 via a torsion bar 39. The torsion
bar 39 is inserted into the output shaft 41, one end thereof is
press fitted and fixed to the input shaft 40, and the other end
thereof is fixed to the output shaft 41 by a pin 41a.
[0056] Further, a speed reduction gear unit 42 is supported in an
outer periphery of the output shaft 41 by a pair of ball bearings
43 and 43, and a torque sensor 44 is arranged in a leading end side
(a right side in FIG. 1) of the speed reduction gear unit 42. The
torque sensor 44 is provided with the torsion bar 39, and an
electromagnetic yoke 47 arranged in an outer periphery of a spline
groove 45 formed in a leading end of the output shaft 41 and
receiving a coil winding 46, and is structured such as to detect a
magnetic change by the coil winding 46 within the electromagnetic
yoke 47 by generating a torsion in the torsion bar 39 in
correspondence to the torque generated in the steering shaft
31.
[0057] Further, the speed reduction gear is constituted by a worm
wheel 48 fixedly mounted to an outer periphery of the output shaft
41 in accordance with a press fitting, a worm 49 engaged with the
worm wheel 48, and a motor mounting the worm 49 to the output shaft
50, and is structured such as to reduce a speed of the rotation of
the motor via the worm 49 and the worm wheel 48 by driving the
motor so as to transmit the torque.
[0058] Further, the rotation angle sensor 51 is constituted by a
thin disc-like detected portion 52 provided within the speed
reduction gear unit 42 and having a smaller diameter than the worm
wheel 48, and the steering shaft 31, that is, a detecting portion
53 provided in an outer side of the bearing 43 in a radial
direction of the output shaft 41, as shown in FIG. 3. The detecting
portion 53 is arranged at a position opposing to a side surface of
the detected portion 52, and is integrally mounted to the output
shaft 41 within a recess groove 54 formed in any one side within
the worm wheel 48. Further, the detecting portion 53 is structured
such as to detect the rotation angle of the output shaft 41 by
detecting an angle signal from the detected portion 52 in a
magnetic manner or an optical manner, or an electric resistance
manner or an electrical capacitance manner.
[0059] Accordingly, in the first embodiment mentioned above, the
detected portion 52 of the rotation angle sensor 51 is provided
within the speed reduction gear unit 42, and the detecting portion
53 is provided in the outer side of the ball bearing 43 in the
radial direction of the output shaft 41. Accordingly, it is not
necessary that the exclusive space for mounting the rotation angle
sensor is provided on the steering shaft 31. As a result, it is
possible to make the stroke t of the energy absorbing mechanism,
that is, a distance in the axial direction by which the outer
column 36 of the steering column 35 moves along the inner column 37
long. As a result, even in the case that the length in the axial
direction on the steering shaft 31 is limited, such as the column
type motor-driven power steering apparatus or the like, it is
possible to secure a sufficient stroke t in the axial direction
even if the rotation angle sensor 51 is provided in the steering
shaft 31, whereby the energy absorbing capacity with respect to the
impact load is not sacrificed.
[0060] Further, FIG. 4 shows a second embodiment in accordance with
the present invention. A description of the second embodiment will
be omitted by attaching the same reference numerals as those of the
first embodiment to the same members. In FIG. 4, the worm wheel 48
is constituted by an approximately ring-like core rod boss portion
61, a gear base portion 62 integrally formed in an outer peripheral
side of the core rod boss portion 61 by a resin, and a resin gear
63 formed in an outer peripheral side of the gear base portion 62
and engaged with the worm 49. Further, a recess groove is formed in
a left side in FIG. 4, in the worm wheel 48, and a detected portion
64 constituted by a small gear is formed within the recess groove
and in an inner peripheral side of the gear base portion 62.
Accordingly, a rotation angle sensor 65 of the output shaft 41 is
constituted by the detected portion 64 and a detecting portion 67
for detecting the rotation of the output shaft 41. Further, the
detecting portion 67 is provided with a protruding shaft 71
extending from a main body 68 arranged in an outer side of the
speed reduction gear unit 42 into the speed reduction gear unit 42
via an insertion hole 70 of a housing cover 69, and a detecting
gear 72 mounted to a leading end of the protruding shaft 71.
Accordingly, the rotation angle sensor 65 is structured, as shown
in FIG. 5 in an enlarged manner, such as to detect the rotation of
the output shaft 41 by the main body 68 from the detecting gear 72
via the protruding shaft 71, in accordance with an engagement
between the detecting gear 72 of the detecting portion 67 and the
small gear constituting the detected portion 64.
[0061] Accordingly, the detected portion 64 of the rotation angle
sensor 65 is provided within the speed reduction gear unit 42, and
the detecting portion 67 is provided in the outer side of the
bearing 43 of the speed reduction gear unit 42 in the radial
direction of the output shaft 41. Therefore, even in the case that
the rotation angle sensor 65 is provided in the steering shaft 31,
it is possible to sufficiently secure the stroke t of the energy
absorbing mechanism, and the energy absorbing capacity is not
sacrificed. Accordingly, the same operations and effects as those
of the first embodiment mentioned above can be achieved even by the
second embodiment.
[0062] Further, FIG. 6 shows a third embodiment in accordance with
the present invention. A description of the third embodiment will
be omitted by attaching the same reference numerals as those of the
first embodiment to the same members. In FIG. 6, the rotation angle
sensor 65 is constituted by an annular detected portion 64 provided
in a side surface of a leading end side (a right side in FIG. 6) of
the worm wheel 48, and a detecting portion 67 provided at a
position opposing to the detected portion 64, as shown in FIG.
7.
[0063] Accordingly, the detected portion 64 of the rotation angle
sensor 65 is provided within the speed reduction gear unit 42, and
the detecting portion 67 is provided in the outer side of the
bearing 43 of the speed reduction gear unit 42 in the radial
direction of the output shaft 41. Therefore, even in the case that
the rotation angle sensor 65 is provided in the steering shaft 31,
it is possible to sufficiently secure the stroke t of the energy
absorbing mechanism, and the energy absorbing capacity is not
sacrificed. Accordingly, the same operations and effects as those
of the first and second embodiments mentioned above can be achieved
even by the third embodiment.
[0064] In this case, in FIGS. 2, 4 and 6, reference numeral 74
denotes a universal joint for connecting to an intermediate shaft,
and reference numeral 75 denotes a bracket for mounting the
steering apparatus to the vehicle body.
[0065] As mentioned above, in accordance with the motor-driven
power steering apparatus on the basis of the present invention, in
the case that the rotation angle sensor for detecting the steering
state of the steering wheel is provided, the detected portion is
provided in the worm wheel or the like within the speed reduction
gear, and the detecting portion is provided in the outer side of
the bearing of the speed reduction gear in the radial direction of
the steering shaft. Therefore, the rotation angle of the steering
shaft is detected by utilizing the worm wheel of the speed
reduction gear and detecting the angle signal from the detected
portion provided in the worm wheel by the detecting portion while
using the magnetic or optical method, or the like. As a result, it
is not necessary that the exclusive space for arranging the
rotation angle sensor is provided in the axial direction of the
steering shaft, and it is possible to effectively utilize the
stroke of the energy absorbing mechanism. Accordingly, even in the
case that the rotation angle sensor is provided in the limited
space in the axial direction of the steering shaft, such as the
column type motor-driven power steering apparatus or the like, it
is possible to keep a safety with respect to the impact load
generated at a time of the collision of the vehicle or the like,
without sacrificing the energy absorbing capacity.
* * * * *