JP2002284021A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize an electric motor by reducing its dimension and its weight in an electric power steering device. SOLUTION: In this electric power steering device 10, one end of an outer ring 35A of a bearing 35 supporting a rotor 32 is held by a first locking member 61, and one end of an inner ring 35B of the bearing 35 is held by only a second locking member 62 engaged with a groove 33A provided in a sleeve 33 integral with the rotor 32.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an electric power steering apparatus.

[0002]

2. Description of the Related Art An electric power steering apparatus transmits an output of an electric motor to a nut of a ball screw coaxial with a rack shaft interlocking with a steering input shaft, as disclosed in Japanese Patent Application Laid-Open No. 7-322573, for example. The linear movement of the rack shaft is performed by the ball screw, and the wheels linked to the rack shaft are steered to assist the steering force.

[0003] In this electric power steering apparatus, an electric motor is rotatably supported on the inner periphery of the housing via a bearing and a stator fixed to the inner periphery of the housing. And a rotor that transmits rotational force to the nut. The outer ring of the bearing is held by a first locking member fixed to the housing, and the inner ring of the bearing is locked to a groove provided in a sleeve integral with the rotor by a second locking member such as a retaining ring. And is held by a third locking member such as a washer that is backed up in the first position.

[0004]

In the prior art, the inner ring of the bearing that supports the rotor is held by a third locking member that is backed up by a second locking member, and uses two locking members in the axial direction. Therefore, the number of parts increases, the length of the sleeve integral with the rotor increases, and the size of the electric motor increases in size and weight.

An object of the present invention is to reduce the size and weight of an electric motor in an electric power steering device.

[0006]

According to a first aspect of the present invention, an output of an electric motor is transmitted to a nut of a ball screw coaxial with a rack shaft interlocked with a steering input shaft, and rotation of the nut is transmitted to the rack shaft by the ball screw. In an electric power steering device that performs linear motion, steers wheels interlocked with a rack shaft, and assists a steering force, an electric motor includes a stator fixed to an inner circumference of a housing and a bearing on an inner circumference of the housing. A first locking member rotatably supported and arranged at a gap around the outer periphery of the rack shaft and transmitting a rotational force to a nut, wherein one end of an outer ring of the bearing is fixed to a housing; , And one end of the inner ring of the bearing is held only by the second locking member engaged with the groove provided in the sleeve integrated with the rotor.

According to a second aspect of the present invention, in the first aspect of the present invention, the second engaging member is further adapted to engage with an annular cutout provided on an end surface of the inner race.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the first locking member obstructs a front surface of a gap between the outer ring and the inner ring.

[0009]

According to the first aspect of the present invention, the following operations are provided. One end of the inner ring of the bearing that supports the rotor is held only by the second locking member that is engaged with the sleeve integral with the rotor, and only one locking member is used in the axial direction. In other words, the length of the sleeve integrated with the rotor is shortened, and the size and weight of the electric motor can be reduced.

According to the second aspect of the present invention, the following effects are obtained. Since the second locking member is locked in the annular notch provided in the inner ring and is assembled so as to bite into the inner ring in the axial direction,
The sleeve can be further shortened integrally with the rotor.

According to the third aspect of the invention, the following operation is provided. Since the first locking member obstructs the front surface of the gap between the outer ring and the inner ring, the abrasion powder of the brush is prevented from entering through the gap between the outer ring and the inner ring of the bearing, and the operation of the bearing is stabilized. Longer life.

[0012]

FIG. 1 is a partially cutaway front view of an electric power steering apparatus, FIG. 2 is an enlarged sectional view of a main part of FIG. 1, FIG. 3 is a sectional view showing a first embodiment, and FIG. FIG. 5 is a sectional view showing a second embodiment, FIG. 5 is a sectional view showing a third embodiment, and FIG. 6 is a sectional view showing a fourth embodiment.

(First Embodiment) (FIGS. 1 to 3) As shown in FIGS. 1 and 2, an electric power steering device 10 includes a housing 11 divided into first and second housings 11A and 11B. Have. An output shaft 14 (not shown) is connected to an input shaft 12 (steering input shaft) to which a steering wheel is coupled via a torsion bar 13, and a pinion 15 (not shown) is provided on the output shaft 14. A rack shaft 16 having a rack that meshes with the rack shaft 15 is supported on the housing 11 so as to be movable left and right. A steering torque detecting device 17 (not shown) is provided between the input shaft 12 and the output shaft 14. The steering torque detecting device 17 applies the steering torque applied to the steering wheel to the output shaft 14, and based on the relative rotational displacement generated between the input shaft 12 and the output shaft 14 due to the elastic torsional deformation of the torsion bar 13, the steering torque is determined. Is detected.

In the electric power steering apparatus 10, both ends of the rack shaft 16 protrude to the left and right of the housing 11, and tie rods 18A and 18B are connected to those ends, and the tie rods 18A and 18B are moved by the left and right movement of the rack shaft 16. The left and right wheels can be steered through the intermediary. The rack shaft 16
Is connected to a pinion 15 at one end by a rack guide (not shown), and the other end is formed by a bearing 37 described later via an extension 36 of a sleeve 33 described later together with a nut 42 of a ball screw 41 described later. It is supported by the housing 11B.

The electric power steering device 10 includes a rack shaft 16 inside a second housing 11B of the housing 11.
, An electric motor 30 is provided. At this time,
The second housing 11B forms a motor housing.
The electric motor 30 is arranged with a gap between the stator (magnet 31A) 31 fixed to the inner periphery of the second housing 11B and the outer periphery of the rack shaft 16, and transmits the rotational force to a nut 42 of a ball screw 41 described later. And a rotor 32.
The rotor 32 is configured by winding a coil around an iron core, and has a sleeve 33 integrated with its inner periphery. The sleeve 33 is coaxially arranged on the outer periphery of the rack shaft 16 at an interval on the outer periphery of the rack shaft 16. And the other end extension 36 projecting to the other end of the rotor 32 is supported on the inner periphery of the second housing 11B by a bearing 37 made of a ball bearing, and is supported by the bearings 35 and 37. In the electric motor 30, the first housing 11A is connected to the first housing 11A in the vicinity of the connection portion between the first housing 11A and the second housing 11B.
A brush holder stay 38 is fixed to an end surface of the housing 11A, and the brush 38A is held by a brush holder fixed to the stay 38. The brush 38A is provided with a commutator 3 near the end of the rotor 32 by a spring provided on the stay 38.
9 is contacted. The electric motor 30 includes a brush 38
A, when power is supplied to the rotor 32 through the commutator 39, the lines of magnetic force of the rotor 32 cut off the magnetic field of the stator 31, thereby driving the rotor 32 to rotate.

In the electric power steering apparatus 10, a ball screw 41 is provided on the rack shaft 16, and the ball screw 4
A nut 42 meshing with the nut 1 is mounted on the inner periphery of the above-mentioned extension 36 of the sleeve 33. The nut 42 is an extension 36
Lock nut 4 screwed onto the stepped portion on the inner circumference and the extension portion 36
4. It is fixed by the stopper ring 45. The steel ball 43 is held between the screw groove 41A of the ball screw 41 and the screw groove 42A of the nut 42, and the rotation of the nut 42 is converted into the linear motion of the rack shaft 16 by the ball screw 41.

Hereinafter, the operation of the electric power steering device 10 will be described. (1) When the steering torque detected by the steering torque detecting device 17 is lower than a predetermined value, no steering assist force is required, and the electric motor 30 is not driven.

(2) When the steering torque detected by the steering torque detector 17 exceeds a predetermined value, a steering assist force is required, and the electric motor 30 is driven. The torque generated by the electric motor 30 is transmitted from the rotor 32 to the nut 42 via the sleeve 33, and the rotation of the nut 42 is converted into linear motion of the rack shaft 16 by the ball screw 41, and the rack shaft 1
6 is applied as a steering assist force to the wheel that is linked to the wheel 6.

However, the electric power steering device 1
0, a bearing 35 for supporting the one end extension 34 of the sleeve 33 integrated with the rotor 32 of the electric motor 30 to the first housing 11A is configured as follows. Bearing 3
5, the outer ring 35A is connected to the housing 11 as shown in FIG.
A is inserted into the bearing hole 51 of A, and is held and held between the washer 52 inserted into the step on the back side of the bearing hole 51 and the first locking member 61 in the form of a nut screwed and fixed to the housing 11A.
Note that the washer 52 may not be provided. Further, the inner ring 35B is loaded on the outer periphery of the sleeve 33, and the C-ring-shaped second retaining member 62 made of a circular cross-section material is engaged with the groove 33A provided on the outer periphery of the sleeve 33; It is clamped and held by a lock nut 53 screwed to the outer periphery.
That is, the bearing 35 connects the one end of the outer ring 35 </ b> A to the first locking member 6.
1 and one end of the inner ring 35B is
2 only.

At this time, the second locking member 62 is
B is engaged with an annular notch 63 provided on the inner diameter side of the end face of B.

The first locking member 61 has an outer diameter portion screwed to the housing 11A and an inner diameter portion to the inner race 35.
B extends to one end side, and confronts the inner ring 35B via a minute gap, thereby blocking the front surface of the gap between the outer ring 35A and the inner ring 35B. The first locking member 61 has an operation hole 61A for an assembling tool, but the operation hole 61A may be non-penetrating.

According to the present embodiment, the following operations are provided. One end of the inner ring 35B of the bearing 35 that supports the rotor 32 is held only by the second locking member 62 that is engaged with the sleeve 33 integrated with the rotor 32, and only one locking member is used in the axial direction. Therefore, the number of parts is reduced, the length of the sleeve 33 integrated with the rotor 32 is also shortened, and the size and weight of the electric motor 30 can be reduced.

The second engaging member 62 is engaged with the annular notch 63 provided in the inner ring 35B and is assembled so as to bite into the inner side of the inner ring 35B in the axial direction. Therefore, the sleeve 33 is further shortened integrally with the rotor 32. it can. Further, the second locking member 6
2 can be suppressed by the corresponding annular notch 63, and a large locking strength can be secured.

The first locking member 61 includes the outer race 35A and the inner race 3
Since the front surface of the gap of 5B is obstructed, the wear powder of the brush 38A is prevented from entering from the gap between the outer ring 35A and the inner ring 35B of the bearing 35, the operation of the bearing 35 is stabilized, and the electric motor 30 has a long life. Can be achieved. The first locking member 61 can also serve as a shielding member.

(Second Embodiment) (FIG. 4) The second embodiment is different from the first embodiment in that a first locking member 71 is used instead of the first locking member 61, and a first locking member 71 is used. Of the inner diameter of the inner ring 35B is reduced, and the area that blocks the front surface of the gap between the outer ring 35A and the inner ring 35B is changed.

(Third Embodiment) (FIG. 5) The third embodiment is different from the first embodiment in that a second locking member 72 is used instead of the second locking member 62, and a second locking member 72 is used. In a C-ring shape and a retaining ring shape made of a material having a rectangular cross section.

(Fourth Embodiment) (FIG. 6) The fourth embodiment is different from the third embodiment in that a first locking member 71 is used instead of the first locking member 61, and a first locking member 71 is used. Of the inner diameter of the inner ring 35B is reduced, and a region that blocks the front surface of the gap between the outer ring 35A and the inner ring 35B is changed.

The embodiment of the present invention has been described with reference to the drawings. However, the specific configuration of the present invention is not limited to this embodiment, and changes in design and the like may be made without departing from the gist of the present invention. The present invention is also included in the present invention.

[0029]

As described above, according to the present invention, in the electric power steering apparatus, the size and weight of the electric motor can be reduced, and the electric motor can also serve as a bearing shielding function.

[Brief description of the drawings]

FIG. 1 is a front view showing an electric power steering apparatus partially cut away.

FIG. 2 is an enlarged sectional view of a main part of FIG.

FIG. 3 is a sectional view showing the first embodiment.

FIG. 4 is a sectional view showing a second embodiment.

FIG. 5 is a sectional view showing a third embodiment.

FIG. 6 is a sectional view showing a fourth embodiment.

[Explanation of symbols]

 Reference Signs List 10 electric power steering device 11A, 11B housing 12 input shaft 16 rack shaft 30 electric motor 31 stator 32 rotor 33 sleeve 33A groove 35 bearing 35A outer ring 35B inner ring 41 ball screw 42 nut 61, 71 first locking member 62, 72 second Locking member 63 Annular notch

 ──────────────────────────────────────────────────の Continued on the front page F term (reference) 3D033 CA02 CA04 3J016 AA01 BA03 CA08 3J017 AA02 CA04 CA06 DA01 DB04 DB06

Claims (3)

[Claims] An output of an electric motor is transmitted to a nut of a ball screw coaxial with a rack shaft interlocked with a steering input shaft, and the rotation of the nut is converted into a linear motion of the rack shaft by the ball screw. In an electric power steering apparatus for turning and assisting a steering force, an electric motor is rotatably supported via a bearing on a stator fixed to an inner periphery of a housing and a rack shaft on an inner periphery of the housing. A rotor disposed at an outer periphery thereof with a gap therebetween and transmitting torque to a nut, wherein one end of an outer ring of the bearing is fixed to a housing.
An electric power steering apparatus, wherein the electric power steering device is held by a locking member, and one end of the inner ring of the bearing is held only by a second locking member engaged with a groove provided in a sleeve integrated with the rotor. 2. The electric power steering apparatus according to claim 1, wherein the second locking member is locked in an annular notch provided in an end surface of the inner race. 3. The electric power steering apparatus according to claim 1, wherein the first locking member blocks a front surface of a gap between the outer ring and the inner ring.