JPH10129511A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device which can maintain smooth steering and which need not special waterproofing structure. SOLUTION: An electric power steering device is provided with a rotary member 63, which is threaded with a rack 4 engaged with a pinion that is rotated by steering operation, and a housing 66, which supports the rotary member 63. By rotating the rotary member 63 through driving a motor, auxiliary steering force in the longitudinal direction of the rack 4 is generated. The housing 66 is provided with a first member 71 and a second member 72, which are juxtaposed in the axial direction of the rotary member 63 and which are joined with each other via a faucet joint constituted of a socket part 71 c and an inserting part 72a. An annular male screw member 81 is threaded with a female screw part 71d in such a manner that a bearing 65 is pushed from the axial direction against the inner surface 71' of the first member 71, so that the male screw member 81 is pushed from the axial direction against the bearing 65 by the inserting part 72a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power for generating a steering assisting force along a longitudinal direction of a rack by driving a rotating member screwed to a rack meshing with a pinion rotated by steering by a motor. The present invention relates to a steering device.

[0002]

2. Description of the Related Art A pinion that rotates by steering, a rack that meshes with the pinion, a rotating member that is screwed to the rack, a motor that drives the rotating member, and supports the rotating member via a bearing. There is an electric power steering device that includes a housing that performs steering of the vehicle by moving the rack in the longitudinal direction by rotation of the pinion, and generates a steering assisting force along the longitudinal direction of the rack by rotating the rotating member.

Conventionally, as shown in FIG. 5, a housing 101 has a first member parallel to an axial direction of a rotating member 102.
A first member 1 having a member 103 and a second member 104;
03 is formed on the end of the second member 1
The female screw portion 104a formed at the end of the screw 04 is screwed. The bearing 105 supporting the rotating member 102 is sandwiched between the first member 103 and the second member 104 by screwing the male screw portion 103a into the female screw portion 104a, and is fixed at a fixed position.

[0004]

In the conventional configuration, since the male screw portion 103a and the female screw portion 104a receive a steering reaction force acting via the rack 106, there is a possibility that the screw adjustment may be loosened. When such loosening occurs, the bearing 105 cannot be fixed at a fixed position, and smooth steering is hindered. In the worst case, the steering may not be possible.

The male screw 103a and the female screw 1
In order to prevent water from entering the housing 101 from the screwing portion with the screw portion 04a, a special waterproof structure for waterproofing between the male screw portion 103a and the female screw portion 104a and for waterproofing the bearing 105 is required. there were.

An object of the present invention is to provide an electric power steering device that can solve the above-mentioned problems.

[0007]

According to the present invention, there is provided a pinion rotated by steering, a rack meshing with the pinion,
A rotating member screwed to the rack, a motor for driving the rotating member to rotate, and a housing for supporting the rotating member via a bearing; The present invention is applied to an electric power steering device that performs steering and generates a steering assist force along the longitudinal direction of a rack by rotationally driving a rotating member. The housing has a first member and a second member that are arranged in the axial direction of the rotating member, and a socket formed at one end of the first member and the second member and a second member at the other end. A spigot joint is formed by the formed insertion portion, and the first member and the second member are joined via the spigot joint. An annular male screw member is screwed onto a female screw portion formed on the inner periphery of the first member so as to press the bearing against the inner surface of the first member from the axial direction, and the male screw member is connected to an end of the second member. The bearing is pressed from the axial direction to the bearing by one of the socket portion and the insertion portion formed in the bearing.

According to the structure of the present invention, the male screw member for pressing the bearing for supporting the rotating member against the inner surface of the first member from the axial direction is the end of the second member joined to the first member via the spigot joint. The bearing is pressed axially against the bearing by means of a plug or socket. Thus, since the male screw member is sandwiched between the bearing and the insertion portion or the socket portion, it is possible to prevent the loosening of the screw engagement between the male screw member and the female screw portion of the first member. Further, since the screw fitting portion between the male screw member and the female screw portion is arranged inside the housing, it is possible to prevent water from entering between the male screw member and the female screw portion.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

A rack and pinion type electric power steering apparatus 1 shown in FIGS. 1 and 2 has a steering shaft 3 which is rotated by steering of a steering wheel (not shown).
And a pinion 3a formed at one end of the steering shaft 3, and a rack 4 meshing with the pinion 3a, and both ends of the rack 4 are provided with steering wheels (not shown).
Linked to When the pinion 3a rotates by steering, the rack 4 moves in the longitudinal direction along the vehicle width direction. The vehicle is steered by the movement of the rack 4.

In order to apply a steering assist force corresponding to the steering torque transmitted by the steering shaft 3, a torque sensor 7 for detecting the steering torque, and a motor 8 driven in accordance with the detected steering torque are provided. , A screw mechanism 1 for transmitting the rotational force of the motor 8 to the rack 4
0 is provided.

The steering shaft 3 has a bearing 26, a housing 26 of the torque sensor 7, and a pinion housing 30 covering the pinion 3a.
It is supported via 27 and 28. Both housings 21, 3
0, the steering shaft 3 is divided into a first shaft 3b on the steering wheel side and a second shaft 3c fitted to the outer periphery of the first shaft 3b via a bush 25 so as to be relatively rotatable. The pinion 3a is formed on the second shaft 3c. A torsion bar 23 is provided on both shafts 3b, 3c with pins 22,
4 so that both shafts 3b, 3c
Are relatively elastically rotatable according to the steering torque.

The torque sensor 7 includes first and second detection coils 33 and 34 held by a sensor housing 21.
And a first detection ring 36 made of a magnetic material fitted to the first shaft 3b, and a second detection ring 37 made of a magnetic material fitted to the second shaft 3c. One end surface of the first detection ring 36 and the second detection ring 37
Are arranged to face each other. On opposite end faces of the detection rings 36 and 37, teeth 36a,
37a are provided along the circumferential direction. The first
The other end of the detection ring 36 is a small-diameter portion 36b having a smaller outer diameter than the one end. The first detection coil 33
Is disposed so as to cover the space between the first detection ring 36 and the second detection ring 37 facing each other. The second detection coil 34
Are arranged so as to cover the first detection ring 36. Each of the detection coils 33 and 34 is connected to a printed board 41 attached to the sensor housing 21 by wiring.

The signal processing circuit shown in FIG. 3 is formed on the printed board 41. That is, the first detection coil 33 is connected to the oscillator 46 via the resistor 45, the second detection coil 34 is connected to the oscillator 46 via the resistor 47, and the detection coils 33 and 34 are connected to the differential amplifier circuit 48. Is done. Thus, when the torsion bar 23 is twisted due to transmission of the steering torque, the first detection ring 36 and the second detection ring 37 rotate relatively. Due to this relative rotation, the teeth 36a of the first detection ring 36 and the second detection ring 3
The facing area of the seventh tooth 37a changes. Due to the area change, the first detection coil 3 passing through both teeth 36a, 37a
3, the magnetic resistance to the generated magnetic flux changes. The output of the first detection coil 33 changes according to the change in the magnetic resistance. Thereby, the steering torque corresponding to the output is detected. Further, the second detection coil 34 faces the small diameter portion 36b of the first detection ring 36. In a state where the steering resistance is not acting, the magnetic resistance to the magnetic flux generated by the first detection coil 33 and the magnetic resistance to the magnetic flux generated by the second detection coil 34 passing through the small diameter portion 36b are made equal to each other. The outer diameter of the small diameter portion 36b is determined. As a result, the output fluctuation of the first detection coil 33 due to the temperature fluctuation becomes equal to the output fluctuation of the second detection coil 34 due to the temperature fluctuation, so that the output fluctuation is canceled out by the differential amplifier circuit 48. That is, the temperature fluctuation of the detected value of the steering torque is compensated.

The motor 8 generates a torque corresponding to the steering torque detected by the torque sensor 7.
Are driven by a drive control device (not shown). The motor 8 is provided so as to cover the rack 4 protruding from the pinion housing 30. That is, the motor 8 includes a cylindrical motor housing 8a attached to the pinion housing 30 and a motor housing 8a.
a, a rotor 8e rotatably supported on the motor housing 8a via bearings 8c and 8d, and a magnet 8f attached to the rotor 8e. Surrounds the rack 4.

As shown in FIG. 4, a screw mechanism 10 for transmitting the rotational force of the motor 8 to the rack 4 includes a ball screw shaft 6 integrally formed on the outer periphery of the rack 4.
1 and a ball 62 on the ball screw shaft 61.
Nut (rotary member) 63 screwed through
And One end of the ball nut 63 forms an inner ring 65 a of the ball bearing 65, and the ball nut 63 is supported by the rack housing 66 via the ball bearing 65. The outer periphery of the other end of the ball nut 63 is connected to the inner periphery of one end of the rotor 8e so as to rotate together therewith. The connection can be made, for example, via a spline, a serration, a torque limiter, or the like. Thus, the ball nut 63 can be driven to rotate by the motor 8, and the rotation of the ball nut 63 generates a steering assist force along the longitudinal direction of the rack 4.

The rack housing 66 has a first member 71 and a second member 72 arranged in the axial direction of the ball nut 63. The first member 71 has a cylindrical small diameter portion 7.
1a and a cylindrical large diameter portion 71b connected to the small diameter portion 71
A socket part 71c formed at one end of the large diameter part 71b; a female screw part 71d formed at the inner periphery of the large diameter part 71b; and a bolt receiving part 71e protruding outward from the socket part 71c. And The second member 72 is cylindrical and has one end integrally formed with the motor housing 8a, the other end formed with the insertion portion 72a, and the outer periphery formed with the bolt screw portion 72b. The socket part 71c and the insertion part 72a form an inlay joint, and the two members 71 and 72 are joined via the inlay joint. The first member 71 and the second member 72 are fixed to each other by the bolt 67 inserted into the bolt receiving portion 71e being screwed into the bolt screwing portion 72b.

Outer ring 65b of the ball bearing 65
Is constituted by joining two members 65b 'and 65b "which are arranged in the axial direction. One end surface of the outer ring 65b is in contact with the inner surface 71' of the first member 71 of the rack housing 66. A male screw member 81 having one end surface in contact with the other end surface is provided with a female screw portion 71 d on the inner periphery of the first member 71.
Screwed. When the male screw member 81 is screwed into the female screw portion 71d, the outer ring 65b becomes the first member 71.
Is axially pressed against the inner surface 71 ′, thereby fixing the ball bearing 65 in a fixed position. The male screw member 81 has an annular portion 81a formed between the outer periphery of the outer ring 65b and the inner periphery of the first member 71.

The other end surface of the male screw member 81 contacts the insertion portion 72a of the second member 72. Thereby, the first member 71 and the second member 72 are joined via the spigot joint, so that the male screw member 81 is pressed against the outer ring 65b of the ball bearing 65 from the axial direction by the insertion portion 72a.

According to the above configuration, the ball bearing 65 that supports the ball nut 63 is attached to the inner surface 7 of the first member 71.
The male screw member 81 that presses against the 1 'from the axial direction is pressed against the ball bearing 65 from the axial direction by the insertion portion 72a of the second member 72 that is joined to the first member 71 via a spigot joint. Thereby, the male screw member 81 is connected to the ball bearing 65 and the insertion portion 72.
a, it is possible to prevent the screwing of the male screw member 81 and the female screw portion 71d from being loosened. Further, since the screwed portion between the male screw member 81 and the female screw portion 71d is arranged inside the rack housing 66, it is possible to prevent water from entering from the screwed portion.

The present invention is not limited to the above embodiment. For example, an insertion portion may be formed at an end of the first member, a socket portion may be formed at an end of the second member, and the male screw member may be axially pressed against the bearing of the rotating member by the socket portion. Further, the type of the bearing that supports the rotating member is not limited to the ball bearing. The rotating member screwed to the rack is not limited to a ball nut, but may be a nut screwed to a trapezoidal screw formed on the outer periphery of the rack.

[0022]

According to the present invention, the loosening of the screwing between the male screw and the female screw for fixing the rotating member screwed to the rack at a fixed position can be prevented, and smooth steering can be maintained. It is possible to provide an electric power steering device that does not require a special waterproof structure at the screwed portion.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an electric power steering device according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is an explanatory diagram of a circuit configuration of a torque sensor of the electric power steering device according to the embodiment of the present invention.

FIG. 4 is a sectional view of a main part of the electric power steering device according to the embodiment of the present invention;

FIG. 5 is a partial sectional view of a conventional electric power steering device.

[Explanation of symbols]

 3a Pinion 4 Rack 8 Motor 63 Ball nut (Rotating member) 65 Ball bearing 66 Rack housing 71 First member 71c Socket portion 71d Female screw portion 72 Second member 72a Insertion portion 81 Male screw member

Claims (1)

[Claims] 1. A pinion that rotates by steering, a rack that meshes with the pinion, a rotating member that is screwed to the rack, a motor that drives the rotating member, and supports the rotating member via a bearing. An electric power steering device that steers the vehicle by moving the rack in the longitudinal direction by rotation of the pinion, and generates a steering assist force along the longitudinal direction of the rack by rotating the rotating member. The housing has a first member and a second member arranged in the axial direction of the rotating member, and a socket formed at one end of the first member and the second member and formed at the other end. The first member and the second member are joined via the spigot joint, and a female formed on the inner periphery of the first member. An annular male screw member is screwed to the inner surface of the first member so as to be able to press the bearing against the inner surface of the first member from the axial direction. An electric power steering device characterized in that the electric power steering device is pressed against the bearing from the axial direction by the shaft.