U.S. patent application number 09/793285 was filed with the patent office on 2001-10-25 for electric power steering apparatus.
Invention is credited to Fujita, Hiroshi, Tsuboi, Yoshitaka.
Application Number | 20010032752 09/793285 |
Document ID | / |
Family ID | 18634962 |
Filed Date | 2001-10-25 |
United States Patent
Application |
20010032752 |
Kind Code |
A1 |
Fujita, Hiroshi ; et
al. |
October 25, 2001 |
Electric power steering apparatus
Abstract
In a motor-driven power steering apparatus, a grease storage is
provided in a lower portion of an engagement portion between a
drive gear and an intermediate gear in a housing, and a partition
wall for preventing a lubricating material or grease from flowing
down from the grease storage to an engagement portion between a
pinion shaft and a rack shaft is provided in a periphery of a
pinion shaft inserting portion of the housing.
Inventors: |
Fujita, Hiroshi; (Tochigi,
JP) ; Tsuboi, Yoshitaka; (Tochigi, JP) |
Correspondence
Address: |
ORUM & ROTH
53 West Jackson Boulevard
Chicago
IL
60604-3606
US
|
Family ID: |
18634962 |
Appl. No.: |
09/793285 |
Filed: |
February 26, 2001 |
Current U.S.
Class: |
180/443 |
Current CPC
Class: |
B62D 5/0403 20130101;
B62D 5/0409 20130101; F16H 57/0464 20130101; F16H 57/045 20130101;
F16H 57/0498 20130101; B62D 5/0421 20130101 |
Class at
Publication: |
180/443 |
International
Class: |
B62D 005/04 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 25, 2000 |
JP |
2000-124912 |
Claims
What is claimed is:
1. An electric power steering apparatus comprising: a pinion shaft
connected to a steering shaft, the pinion shaft being inserted to
an inner portion of a housing so as to be engaged with a rack
shaft; and a drive gear connected to an electric motor and an
intermediate gear connected to the pinion shaft, the drive gear and
the intermediate gear being engaged with each other in an upper
portion of an engagement portion between said pinion shaft and said
rack shaft disposed within the housing, wherein a lubricating
material storage is provided in a lower portion of the engagement
portion between said drive gear and the intermediate gear in the
housing, and a partition wall for preventing the lubricating
material from migrating down from said storage to a side of the
engagement portion between said pinion shaft and the rack shaft is
provided in a periphery of a portion through which the pinion shaft
of said housing is inserted.
2. An electric power steering apparatus as claimed in claim 1,
wherein when said drive gear is constituted by a worm gear and said
intermediate gear is constituted by a worm wheel, said storage is
formed in a groove shape extending along a tooth face of the worm
wheel.
3. An electric power steering apparatus as claimed in claim 2,
wherein said groove-shaped storage is extended along only a part of
the tooth face of the worm wheel in the peripheral direction.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an electric power steering
apparatus.
[0003] 2. Description of the Related Art
[0004] As shown in a Japanese unexamined Patent Publication No.
(JP-A) 8-34355, an electric power steering apparatus is structured
such that a pinion shaft connected to a steering shaft is engaged
with a rack shaft. A worm gear is provided in a drive shaft
connected to an electric motor and a worm wheel engaged with the
worm gear is connected to the pinion shaft, whereby a torque of the
motor is transmitted to the rack shaft so as to assist a steering
operation.
[0005] In an electric power steering apparatus, one type of
lubricating material or grease is used for an engagement portion
between the pinion shaft and the rack shaft, and another type of
lubricating material or grease is used for an engagement portion
between the worm gear and the worm wheel The two engagement
portions mentioned above are arranged within a housing which forms
the same space, and the engagement portion between the worm gear
and the worm wheel is positioned above the engagement portion
between the pinion shaft and the rack shaft. Accordingly, in the
conventional art, the lubricating material in the engagement
portion between the worm gear and the worm wheel flows down to a
lower engagement portion between the pinion shaft and the rack
shaft so as to be mixed with the lubricating material in the
engagement portion between the pinion shaft and the rack shaft.
This generates an unexpected change in the nature of the grease to
be used for the engagement portion between the pinion shaft and the
rack shaft and causes a reduction of durability due to an inferior
lubrication between the pinion shaft and the rack shaft.
SUMMARY OF THE INVENTION
[0006] An object of the present invention is to improve lubricating
performance between a pinion shaft and a rack shaft and improve a
durability thereof at while simultaneously providing both
engagement portion between the pinion shaft and the rack shaft and
engagement portion between a drive gear and an intermediate gear in
the same space formed by a housing, in an electric power steering
apparatus.
[0007] In accordance with the present invention, there is provided
an electric power steering apparatus comprising:
[0008] a pinion shaft connected to a steering shaft, the pinion
shaft being inserted to an inner portion of a housing so as to be
engaged with a rack shaft.
[0009] A drive gear is provided, connected to an electric motor,
and an intermediate gear connected to the pinion shaft, the drive
gear and the intermediate gear being engaged with each other in an
upper portion of an engagement portion between the pinion shaft and
the rack shaft disposed within the housing.
[0010] Storage for the lubricating material is provided in a lower
portion of the engagement portion between the drive gear and the
intermediate gear in the housing. A partition wall prevents the
lubricating material from dripping down from the storage area to an
area where the engagement portion between the pinion shaft and the
rack shaft is provided in a periphery of a portion through which
the pinion shaft of the housing is inserted.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The present invention will be more fully understood from the
detailed description given below and from the accompanying drawings
which should not be taken to be a limitation on the invention, but
are for explanation and understanding only.
[0012] The drawings
[0013] FIG. 1 is a front elevational view showing an electric power
steering apparatus in a partly broken manner;
[0014] FIG. 2 is a cross sectional view along a line II-II in FIG.
1;
[0015] FIG. 3 is a front elevational view showing a housing;
and
[0016] FIG. 4 is an end surface view along a line IV-IV in FIG.
2.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] An electric power steering apparatus 10 has a housing 11
(first to third housings 11A to 11C) fixed to a vehicle body frame
or the like by a bracket (not shown), as shown in FIGS. 1 and 2.
The electric power steering apparatus 10 is structured such that a
pinion shaft 14 is connected to a steering shaft 12 to which a
steering wheel is connected, via a torsion bar 13. A pinion 15 is
provided in the pinion shaft 14 and a rack shaft 16 provided with a
rack 17 engaged with the pinion 15 is supported to the first
housing 11A in such a manner as to freely move in a lateral
direction. A steering torque detecting apparatus 20 is provided
between the steering shaft 12 and the pinion shaft 14. In this
case, the steering shaft 12 and the pinion shaft 14 are supported
to the housing 11 via bearings 12A, 14A and 14B.
[0018] The steering torque detecting apparatus 20 is, as shown in
FIG. 2, provided with two detecting coils 20A and 20B surrounding a
cylindrical core 20C engaged with the steering shaft 12 and the
pinion shaft 14 in the third housing 11C. The core 20C is provided
with a vertical groove 20E engaging with a guide pin 20D of the
pinion shaft 14 so as to freely move only in an axial direction. It
is also provided with a spiral groove 20G engaging with a slider
pin 20F of the steering shaft 12. Accordingly, when a steering
torque applied to the steering wheel is applied to the steering
shaft 12 and a relative displacement in a rotational direction is
generated between the steering shaft 12 and the pinion shaft 14 due
to an elastic torsional deformation of the torsion bar 13, the
displacement in the rotational direction of the steering shaft 12
and the pinion shaft 14 causes displacement of the core 20C in an
axial direction. An inductance of the detecting coils 20A and 20B
due to a magnetic change in the periphery of the detecting coils
20A and 20B generated by the displacement of the core 20C is
changed. When the core 20C moves toward the steering shaft 12, an
inductance of the detecting coil 20A disposed in a side to which
the core 20C moves is increased, and an inductance of the detecting
coil 20B disposed in a side from which the core 20C moves apart is
reduced, whereby it is possible to detect the steering torque due
to the change of the inductance.
[0019] A rack guide 22 is installed, as shown in FIG. 2, in a
cylinder portion 21 provided in a portion opposing the pinion 15
with respect to the rack shaft 16 within the first housing 11A. The
rack guide 22 (a bush 22A) is elastically provided in a side of the
rack shaft 16 by a spring 24 supported on a back surface by a cap
23 attached to the cylinder portion 21 so as to press the rack 17
of the rack shaft 16 to the pinion 15 and slidably support one end
of the rack shaft 16. In this case, another end side of the rack
shaft 16 is supported by bearing 25. Further, right and left tie
rods 27A and 27B are connected to an intermediate portion of the
rack shaft 16 by connecting bolts 26A and 26B.
[0020] The second housing 11B supports an electric motor 30, as
shown in FIG. 1. A drive shaft (not shown in the figure) is
connected to an output shaft 31 of the electric motor 30 via a
clutch, the drive shaft (not shown in the figure) is supported to
the housing 11B by bearing device at both ends, and a worm gear (a
drive gear) 35 is integrally provided in an intermediate portion of
the drive shaft (not shown in the figure). Then, a worm wheel 36
(an intermediate gear) engaging with the worm gear 35 is fixed to
an intermediate portion of the pinion shaft 14. A generated torque
of the electric motor 30 is applied as a steering assist force to
the rack shaft 16 via an engagement between the worm gear 35 and
the worm wheel 36 and an engagement between the pinion 15 and the
rack 17 so as to assist steering force which a driver applies to
the steering shaft 12. In this case, reference numerals 33A and 33B
denote an outer wheel lock nut and an inner wheel stopper ring of
the bearing 33, respectively.
[0021] In the electric power steering apparatus 10, as mentioned
above, the pinion shaft 14 (the pinion 15) connected to the
steering shaft 12 is inserted into the pinion shaft inserting
portion 41 within the first housing 11A so as to be engaged with
the rack shaft 16 (the rack 17) (corresponding to the engagement
portion 42B), and the worm gear 35 connected to the electric motor
30 and the worm wheel 36 connected to the pinion shaft 14 are
engaged with each other at the upper portion of the engagement
portion 42B between the pinion shaft 14 and the rack shaft 16 which
is disposed within the second housing 11B (corresponding to the
engagement portion 42A). The engagement portion 42A and the
engagement portion 42B are commonly disposed in the same space
which both of the housings 11A and 11B commonly form. Accordingly,
there is a difference between a kind of a lubricating material or
grease A applied to the engagement portion 42A between the worm
gear 35 and the worm wheel 36 and another kind of a lubricating
material or grease B applied to the engagement portion 42B between
the pinion 15 and the rack 17.
[0022] Accordingly, in the electric power steering apparatus 10, in
the first housing 11A shown in FIG. 3, a grease storage 43 is
provided in a lower portion of the engagement portion 42A between
the worm gear 35 and the worm wheel 36, as shown in FIGS. 2 and 4.
A cross section at which the grease storage 43 in FIG. 2 is
positioned is along a line A-A in FIG. 4. The grease storage 43 is
placed in the periphery of the pinion shaft inserting portion 41
mentioned above in the first housing 11A and is formed in a groove
shape extending along a tooth face of the worm wheel 36. In this
case, the grease storage 43 is not limited to a structure partly
provided along the periphery of the pinion shaft inserting portion
41 (FIG. 4), and may be structured such as to be continuously
provided in all the periphery.
[0023] Further, in the electric power steering apparatus 10, a
ring-shaped partition wall 44 is provided in the periphery of the
pinion shaft inserting portion 41 mentioned above in the first
housing 11A in a standing manner. The partition wall 44 prevents
the lubricating material or grease A from flowing down from the
grease storage 43 to the side of the engagement portion 42B between
the pinion shaft 14 (the pinion 15) and the rack shaft 16 (the rack
17).
[0024] Therefore, in accordance with the present embodiment, the
following effects can be obtained.
[0025] (1) The lubricating material or grease A in the engagement
portion 42A between the worm gear 35 and the worm wheel 36 can be
received by the grease storage 43 in the lower portion thereof even
when dropping down, and is prevented by the existence of the
partition wall 44 from flowing downward in the side of the pinion
shaft 14. Accordingly, even in the case that the engagement portion
42B between the pinion shaft 14 and the rack shaft 16 and the
engagement portion 42A between the worm gear 35 and the worm wheel
36 are commonly disposed in the same space formed by the housing 11
(11A and 11B), the lubricating material or grease A in the
engagement portion 42A between the worm gear 35 and the worm wheel
36 does not flow down to the side of the engagement portion 42B
between the lower pinion shaft 14 and the rack shaft 16 and is not
mixed into the lubricating material or grease B in the engagement
portion 42B between the pinion shaft 14 and the rack shaft 16 so as
to change the nature thereof, so that an inferior lubrication is
not generated in the engagement portion 42B between the pinion
shaft 14 and the rack shaft 16 and it is possible to improve a
durability thereof.
[0026] (2) Since the lubricating material or grease storage 43 is
formed in the groove shape along the tooth face of the worm wheel
36, it is possible to securely receive the grease A migrating down
from the engagement portion 42A between the worm gear 35 and the
worm wheel 36 by the grease storage 43.
[0027] (3) When the grease storage 43 is structured such as to
extend along only a part of the tooth face of the worm wheel 36 in
the peripheral direction, when providing the groove-shaped grease
storage 43 in the housing 11, it is possible to reduce a portion in
which the outer wall of the housing 11 protrudes outward due to the
formation of the grease storage 43, so that it is possible to make
the housing 11 and in its turn the electric power steering
apparatus 10 compact.
[0028] As heretofore explained, embodiments of the present
invention have been described in detail with reference to the
drawings. However, the specific configurations of the present
invention are not limited to the embodiments but those having a
modification of the design within the range of the present
invention are also included in the present invention. For example,
in accordance with the present invention, the drive gear and the
intermediate gear interposed between the electric motor and the
pinion shaft are not limited to those constituted by the worm gear
mechanism, and may be constituted by the other structures
comprising a bevel-shaped gear mechanism such as a hypoid gear, a
bevel gear or the like. Likewise, the lubricating material may
comprise any suitable substance.
[0029] As mentioned above, in accordance with the present
invention, in the electric power steering apparatus, it is possible
to improve lubricating performance between the pinion shaft and the
rack shaft and improve durability thereof, while simultaneously
disposing the engagement portion between the pinion shaft and the
rack shaft and the engagement portion between the drive gear and
the intermediate gear in the same space formed by the housing.
Further, it is possible to integrally assemble with the housing
without independently assembling a seal member or the like for
preventing the grease from flowing down later, so that it is easy
to assemble the structure.
[0030] Although the invention has been illustrated and described
with respect to several exemplary embodiments thereof, it should be
understood by those skilled in the art that the foregoing and
various other changes, omissions and additions may be made to the
present invention without departing from the spirit and scope
thereof. Therefore, the present invention should not be understood
as limited to the specific embodiment set out above, but should be
understood to include all possible embodiments which can be
embodied within a scope encompassed and equivalents thereof with
respect to the features set out in the appended claims.
* * * * *