JP2001278080A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a screw groove of a rack shaft and a ball screw device from external environment in an electric power steering device. SOLUTION: In the electric power steering device 10, a ball screw device 50 is installed between an engagement region of a pinion 15 and a mounting region for an electric motor 30 in the axial direction along the rack shaft 16 in a housing 11.

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 Conventionally, as disclosed in Japanese Patent Application Laid-Open No. Hei 9-104351, as an electric power steering apparatus, the steering rotation of a steering wheel is transmitted to a rack shaft via an input shaft and a pinion as left and right movements. When turning the wheels via the tie rods connected to both ends, the steering torque of the input shaft is detected, and the electric motor is driven based on the detected value. In some cases, the steering force is assisted by transmitting the steering force via the steering wheel.

At this time, in the electric power steering apparatus, the housing and the housing are movably supported by the housing.
A rack shaft in which a pinion connected to the input shaft meshes, an electric motor disposed around the rack shaft in the housing, and a ball disposed around the rack shaft in the housing and transmitting torque of the electric motor to the rack shaft And a screw device.

However, in the prior art, the electric motor is installed between the pinion meshing portion and the installation site of the ball screw device in the axial direction along the rack axis in the housing.

[0005]

The prior art has the following problems. The ball screw device is installed near the end of the housing, and the screw groove of the rack shaft that meshes with the ball screw device comes out of the housing during left-right steering. For this reason, flying stones and the like may damage the screw groove of the rack shaft from the outside or foreign matter that enters when the dust boot sealed at the end of the housing is damaged may contaminate the screw groove of the rack shaft or the ball screw device. There is.

In the case where tie rods are connected to both ends of a rack shaft protruding from both sides of the housing, a bending moment due to a right-angle load applied to the end of the rack shaft by the tie rods is applied to the outer peripheral side of the ball screw device. It will be supported by the housing via the bearing. However, since this bearing is in sliding contact with the thread groove of the rack shaft, it is difficult to actively support the bearing. For this reason, the ball screw device is twisted by the bending moment, causing friction loss and abnormal noise.

An object of the present invention is to protect a thread groove of a rack shaft and a ball screw device from an external environment in an electric power steering device.

Another object of the present invention is to improve the operability of a ball screw device.

[0009]

According to the present invention, a housing and a housing are movably supported by the housing.
A rack shaft in which a pinion connected to the input shaft meshes, an electric motor disposed around the rack shaft in the housing, and a ball disposed around the rack shaft in the housing and transmitting torque of the electric motor to the rack shaft An electric power steering device having a screw device, wherein a ball screw device is installed between a pinion meshing portion and an electric motor installation portion in an axial direction along a rack axis in a housing. .

According to a second aspect of the present invention, in the first aspect of the present invention, one end of the rack shaft is supported by a housing via a rack guide at a pinion meshing portion, and the other end of the rack shaft is connected to the other end of the rack shaft. The electric motor is supported on the housing via a bearing on the outer side in the axial direction, and a substantially intermediate portion of the rack shaft is supported on the housing via a bearing on the outer peripheral side of the ball screw device.

[0011]

According to the first aspect of the present invention, the following operations are provided. Since the ball screw device is installed at a substantially intermediate portion between the pinion meshing portion and the electric motor installation portion in the housing, the screw groove of the rack shaft meshing with the ball screw device can be housed inside the housing even when steering left and right. it can.
For this reason, flying stones and the like do not damage the screw groove of the rack shaft from the outside, and foreign matter that enters when the dust boot sealed at the end of the housing is damaged does not enter the screw groove of the rack shaft or the ball screw device. There is no risk of soiling.

According to the second aspect of the present invention, the following operations are provided. In the case where tie rods are connected to both ends of a rack shaft protruding from both sides of the housing, the bending moment due to a right angle load applied to the end of the rack shaft by the tie rods is as follows:
Both ends are supported by a rack guide at a pinion meshing portion at one end and a bearing provided outside the electric motor at the other end. For this reason, the above-mentioned bending moment does not squeeze the ball screw device provided around the substantially middle portion of the rack shaft, and it is possible to improve the friction loss and the generation of abnormal noise of the ball screw device.

[0013]

1 is a cross-sectional view showing an electric power steering apparatus, FIG. 2 is a cross-sectional view showing main parts on the right side of FIG. 1, and FIG. 3 is a cross-sectional view showing main parts on the left side of FIG. 4 is FIG.
1 is a sectional view taken along line IV-IV, and FIG. 5 is a sectional view taken along line VV in FIG.

The electric power steering apparatus 10 is shown in FIG.
As shown in FIG. 3, first to third housings 11A to 11A
The housing 11 is divided into three sections 1C. An output shaft 14 is connected to an input shaft 12 to which a steering wheel is coupled via a torsion bar 13, a pinion 15 is provided on the output shaft 14, and a rack shaft 16 having a rack 16 </ b> A meshed with the pinion 15 is provided. Housing 1
1 is supported to be able to move left and right. Input shaft 12 and output shaft 1
4, a steering torque detecting device 17 is provided.
The input shaft 12 and the output shaft 14 have bearings 12A, 14A, 1
It is supported by the housing 11 via 4B.

As shown in FIG. 4, the steering torque detecting device 17 includes two detecting coils 17A and 17B surrounding a cylindrical core 17C engaged with the input shaft 12 and the output shaft 14, respectively.
It is provided on the housing 11A. The core 17C is provided with a vertical groove 17E that engages with the guide pin 17D of the output shaft 14, is movable only in the axial direction, and has a spiral groove 17G that engages with the slider pin 17F of the input shaft 12. As a result, when the steering torque applied to the steering wheel is applied to the input shaft 12 and a relative displacement in the rotational direction occurs between the input shaft 12 and the output shaft 14 due to the elastic torsional deformation of the torsion bar 13, the input shaft 12 Output shaft 1
4 displaces the core 17C in the axial direction, and the detection coil 1 due to the displacement of the core 17C.
The inductance of the detection coils 17A and 17B changes due to magnetic changes around 7A and 17B. That is, when the core 17C moves toward the input shaft 12, the inductance of the detection coil 17A closer to the core 17C increases,
The inductance of the detection coil 17B away from the core 17C decreases, and the change in the inductance enables the detection of the steering torque.

As shown in FIG. 4, a rack guide 19 is provided on a cylinder portion 18 provided at a portion of the first housing 11A on one end side of the housing 11 opposite to the pinion 15 with one end of the rack shaft 16 interposed therebetween. The rack guide 19 (the bush 19A) is resiliently pushed toward the rack shaft 16 by a spring 21 supported on the back surface by a cap 20 attached to the cylinder portion 18, and the rack 1
6A against the pinion 15 and the rack shaft 1
6 is slidably supported at one end. The other end of the rack shaft 16 is supported by a bearing 42 described later. Then, both ends of the rack shaft 16 project to the left and right of the housing 11,
Tie rods 22A and 22B are connected to their ends, and the tie rods 22A and 22B are
The left and right wheels can be steered via 2B. Both ends of the rack shaft 16 and the left and right tie rods 22A, 22B are
They are connected by universal joints 23A and 23B and are sealed by a dust boot 24A attached to the first housing 11A and the tie rod 22A and a dust boot 24B attached to the third housing 11C and the tie rod 22B.

As shown in FIG. 3, an electric motor 30 is disposed around the rack shaft 16 mainly in the second housing 11B of the housing 11. Electric motor 30
Consists of a stator (magnet) 31 fixed to the inner periphery of the second housing 11B and a rotor 32 arranged on the outer periphery of the rack shaft 16 with a gap. Iron core 3 is attached to rotor 32
3 is fixed, and a coil 34 is wound around the iron core 33. At this time, one end of the rotor 32 is rotatably supported by the first housing 11A via a ball screw device 50 described later and a bearing 35 formed of an angular ball bearing, and the other end of the rotor 32 is connected to the radial ball bearing. Is rotatably supported by the third housing 11C via a bearing 36.

In the electric motor 30, as shown in FIGS.
B on the end face of the third housing 11C to which the rotor 3 is connected.
The brush folder 37 is fixed around two turns, and the brush 38 is held in the brush folder 37. The brush 38
A spring 39 provided in the brush folder 37 repels the rotor 32 in the radial direction, and is brought into contact with a commutator 40 provided near the end of the rotor 32. 41 is a lead wire.

As shown in FIG. 3, a bearing 42 made of a bush is provided at an end of the third housing 11C at the other end of the housing 11, and slidably supports the other end of the rack shaft 16.

At the intermediate portion of the housing 11, the first housing 11A to which the second housing 11B is connected is provided with the structure shown in FIG.
As shown in the figure, the nut 51 of the ball screw device 50 is held via the bearing 35. The ball screw device 50 is
Thread groove 51A of nut 51 integrally joined to rotor 32
And a screw groove 52 provided on the rack shaft 16 to hold a steel ball 53, and converts the rotation of the rotor 32 into the axial movement of the rack shaft 16. The nut 51 includes a deflector that circulates the ball 53 through the thread groove 51A. The outer ring of the bearing 35 is fixed to the first housing 11A by a lock nut 54, and the inner ring is fixed to the nut 51 by a lock nut 55.

That is, in the electric power steering apparatus 10, the rack shaft 1 in the housing 11 (11A to 11C) is provided.
The ball screw device 50 is installed between the engagement portion of the pinion 15 and the installation portion of the electric motor 30 in the axial direction along 6. Then, one end of the rack shaft 16 is connected to the pinion 15.
Of the housing 11 via the rack guide 19
(11A), and the other end of the rack shaft 16 is connected to the housing 1 via an axially outer bearing 42 of the electric motor 30.
1 (11C), and the intermediate portion of the rack shaft 16 is connected to the housing 1
1 (11A).

Therefore, the electric power steering device 10
In this case, the power supplied to the electric motor 30 is determined by a control device (ECU) to which signals from the steering torque detecting device 17, a vehicle speed sensor, and the like are input. The motor 30 is driven.
When the rotor 32 is rotated by the drive of the electric motor 30,
The rack shaft 16 moves right and left via the nut 51 of the ball screw device 50 integrated with the rotor 32, and assists the steering force.

Therefore, according to the present embodiment, the following operations are provided. The ball screw device 50 is connected to the pinion 1 in the housing 11.
5, the screw groove 52 of the rack shaft 16 that meshes with the ball screw device 50 can be accommodated in the housing 11 even during left-right steering. . Therefore, flying stones and the like do not damage the thread groove 52 of the rack shaft 16 from the outside, and foreign matter that enters when the dust boots 24A and 24B sealed at the end of the housing 11 breaks is prevented. There is no risk of soiling the screw groove 52 and the ball screw device 50.

The tie rods 22A and 22B are connected to both ends of a rack shaft 16 protruding from both sides of the housing 11.
The bending moment due to the load perpendicular to the axis applied to the end of the rack guide 6 is the rack guide 1 at the meshing portion of the pinion 15 at one end.
9, and both ends are supported by bearings 42 provided outside the electric motor 30 on the other end side. For this reason, the above-mentioned bending moment does not pry the ball screw device 50 disposed around the intermediate portion of the rack shaft 16, and the friction loss of the ball screw device 50 and the generation of abnormal noise can be improved.

The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration of the present invention is not limited to this embodiment, and the design can be changed within the scope of the present invention. The present invention is also included in the present invention.

[0026]

As described above, according to the present invention, the screw groove of the rack shaft and the ball screw device can be protected from the external environment in the electric power steering device.

Further, according to the present invention, in the case where tie rods are connected to both ends of the rack shaft, the operability of the ball screw device installed around the rack shaft can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an electric power steering apparatus.

FIG. 2 is a sectional view showing a main part on the right side of FIG. 1;

FIG. 3 is a sectional view showing a main part on the left side of FIG. 1;

FIG. 4 is a sectional view taken along the line IV-IV in FIG. 1;

FIG. 5 is a sectional view taken along the line VV of FIG. 1;

[Explanation of symbols]

 Reference Signs List 10 electric power steering device 11 housing 12 input shaft 15 pinion 16 rack shaft 19 rack guide 30 electric motor 35 bearing 42 bearing 50 ball screw device

Claims (2)

[Claims] 1. A housing, a rack shaft movably supported by the housing and meshing with a pinion connected to an input shaft, an electric motor disposed around the rack shaft in the housing, and a rack shaft in the housing An electric power steering device having a ball screw device that is disposed around and transmits the torque of the electric motor to the rack shaft, wherein the pinion meshing portion and the electric motor installation portion are arranged in the axial direction along the rack shaft in the housing. An electric power steering device comprising a ball screw device installed therebetween. 2. An end of the rack shaft is supported by a housing via a rack guide at a pinion meshing portion, and the other end of the rack shaft is supported by the housing via an axially outer bearing of the electric motor. 2. The electric power steering device according to claim 1, wherein a substantially intermediate portion of the rack shaft is supported on the housing via a bearing on an outer peripheral side of the ball screw device.