JP2003175839A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device possible to be assembled by reducing the number of part items and assembly man-hours by making it a single housing. <P>SOLUTION: The electric power steering device is equipped with a torque sensor detecting a steering torque, a control circuit determining an auxiliary steering force, an electric motor giving the auxiliary steering force to an output shaft and a power transmission part transmitting the auxiliary steering force to a steered wheel side. This device has the single housing to store the torque sensor and the power transmission part. Inside of the housing is formed by a multi-step nearly cylindrical shape where diameters are enlarged in stepped shape toward the output shaft side in the direction of steering shaft. They are a first cylindrical part arranging the torque sensor, a second cylindrical part placing a bearing and a third cylindrical part arranging a worm wheel in order. Since it is not necessary to join together in the case of assembling thereby, the number of part items and the assembly man-hours are reduced. In addition, components of the torque sensor and the power transmission part can be assembled inside the housing. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus for assisting steering force of a vehicle steering wheel.

[0002]

2. Description of the Related Art A conventional electric power steering apparatus (hereinafter abbreviated as EPS) includes a torque sensor, a control circuit, an electric motor, and a power transmission section, as described in Japanese Patent Laid-Open No. 8-175403. Is configured.

[0003]

However, the above-mentioned EP
In S, a bearing that supports the input shaft and a bearing that supports the output shaft are arranged on the inner circumference of the housing.
Since the diameter of the worm wheel is large, it cannot be assembled unless the housing is divided into separate parts. for that reason,
Since it is necessary to connect separate housings, there is a problem that the number of assembling steps at the time of assembling increases. Further, there is a problem that the number of parts such as screws is increased and the cost is increased.

The present invention has been made in view of the above problems, and a single housing is provided by providing first, second, and third cylindrical portions whose diameters are stepwise expanded in the inner circumference of the housing. It is an object of the present invention to provide an EPS that can be assembled by reducing the number of parts and the number of assembling steps.

[0005]

In order to solve the above-mentioned problems, according to claim 1, a torque sensor (2) for detecting a steering torque from a steering wheel (6) and a detection value detected by the torque sensor are used. The steering assist force determined by the control circuit, the electric motor (4) that applies the steering assist force determined by the control circuit to the output shaft (52), and the steering assist force output by the electric motor. In an electric power steering device including a power transmission unit (5) having a worm wheel (59) for transmitting to a steered wheel side, a torque sensor,
And a single housing (11) for accommodating the power transmission unit, and is formed on the inner circumference of the housing in a multi-stage substantially cylindrical shape whose diameter spreads stepwise on the output shaft side in the steering axis direction,
A first cylindrical portion (14) for disposing a torque sensor, a second cylindrical portion (15) provided with a bearing (13) for supporting an output shaft, and a third disposing a worm wheel.
It is characterized in that it is formed in the order of the cylindrical portion (16).

With this structure, the inner periphery of the housing is formed in a multi-stage, substantially cylindrical shape whose diameter increases toward the output shaft side in the steering axis direction. And, the torque sensor and the second
A bearing that supports the output shaft in the cylindrical portion, and a worm wheel that forms the power transmission portion in the third cylindrical portion are assembled in this order. Therefore, each component of the torque sensor and the power transmission unit can be assembled in a single housing. Therefore, since it is formed of a single housing, it is not necessary to screw the housings together to assemble them. Therefore, the number of parts and the number of assembling steps can be reduced.

Further, in the present invention, the torque sensor detects the steering torque by using the Hall IC (22) which is a magnetic sensor.

With this configuration, it is not necessary to directly detect the magnetic flux generated from the hard magnetic material magnet fixed to the input shaft. Therefore, an electric contact portion is not provided for the Hall IC, so that a highly reliable torque sensor can be provided. Further, it can be made smaller than a conventionally known torque sensor using a rotary variable resistor and a torque sensor using an inductance change.

In the third aspect, the control circuit has the cover (33) which is a soft magnetic material, and the Hall IC.
A control circuit is arranged between the electric motor and the electric motor.

With this configuration, the Hall IC can prevent the influence of the magnetic force generated from the magnet, which is a component of the electric motor, by the cover of the soft magnetic material that can serve as the magnetic shielding means. Further, since it is not necessary to newly provide the magnetic shielding means, the number of parts does not increase. Further, since the Hall IC can be arranged near the control circuit, the wiring connecting the Hall IC and the control board can be shortened.

Further, in the present invention, a guide groove (25) for arranging a signal line for connecting the Hall IC and the control board (32) of the control circuit is formed on the inner peripheral surface of the housing. It is characterized by being.

With this configuration, the signal line of the Hall IC connected to the control board can be easily wired, so that the assembling property is improved.

Further, in claim 5, the magnetism collecting ring (21)
Is for concentrating the magnetic flux density on the Hall IC, and is characterized in that a notch (26) for positioning the Hall IC and the magnetism collecting ring is formed in the housing.

With this configuration, it is possible to accurately determine the positional relationship between the Hall IC and the magnetic flux collecting ring. Therefore, it is possible to prevent positional displacement when the Hall IC and the magnetic flux collecting ring are arranged. Further, since the Hall IC is easily fitted into the magnetism collecting ring, the assembling property is improved.

Further, according to a sixth aspect, the housing is arranged near the steering rack (54) of the steering shaft.

With this configuration, the distance between the output shaft and the pinion gear becomes small, and thus it is less likely to be affected by the twist of the steering shaft. Therefore, the steering assist force output from the EPS can be directly transmitted to the steering rack, and a large steering assist force can be transmitted.

According to a seventh aspect of the present invention, the housing has a steering rack penetrating therethrough.

As a result, since the EPS housing and the steering rack housing can be integrally formed, the number of parts can be reduced.

[0019]

DETAILED DESCRIPTION OF THE INVENTION Embodiments will be described below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of a rack type EPS. The configuration of the EPS will be described based on this figure.

The integrated EPS 1 of the rack type EPS shown in FIG. 1 is disposed near the steering rack 54 of the steering shaft. Further, the steering force applied to the steering wheel 6 by the driver is transmitted to the input shaft 51 and is transmitted to the integrated EPS 1 via the universal joint 60.
The steering assist force determined and output by the integrated EPS 1 is transmitted to the output shaft 52 (see FIG. 5). The structure and operation of the integrated EPS 1 will be described later. Then, the steering assist force is transmitted to a pinion gear (not shown) fixed to the tip of the steering shaft on the side opposite to the steering side. Then, the steering assist force transmitted to the pinion gear is transmitted to the steering rack 54 and converted into a linear motion in the left-right direction of the vehicle. Then, the tires 56 are steered via the tire hinges 55 which are arranged at both ends of the steering rack 54 and serve as hinges. Further, in the integrated EPS 1, one vehicle harness 17 for connecting the + and-power supply lines is connected to the battery 7. Further, the connector 10 (see FIG. 2) of the vehicle harness 17 can be connected to one or two serial communication lines for notifying the driver of information such as EPS failure.

FIG. 2 is a plan view of the integrated EPS 1 as viewed from above in the axial direction. 3 is a plan view of the torque sensor 2 as seen from above in the axial direction. 4 is a sectional view taken along the line AA of FIG. In addition, FIG. 5 shows BB of FIG.
FIG. 6 is a sectional view taken along the line CC of FIG. Based on these figures, the integrated EP of the present invention
The structure of S1 will be described.

As shown in FIG. 2, the integrated EPS 1 is composed of a torque sensor 2, a control circuit 3, an electric motor 4, a power transmission section 5, a housing 11 and the like.

The housing 11 covers the torque sensor 2 and the power transmission section 5. As shown in FIG. 5, a first cylindrical portion 14, a second cylindrical portion 15, and a third cylindrical portion 16 are formed on the inner circumference of the housing 11.

The torque sensor 2 is provided in the first cylindrical portion 14.
Arrange the components. In addition, the second cylindrical portion 15 is provided with a bearing 13 that rotatably supports the output shaft 52. Further, the power transmission unit 5 is provided in the third cylindrical portion.
A worm wheel 59 is formed.

The inner diameter of the first cylindrical portion 14 is smaller than the inner diameter of the second cylindrical portion 15, and the inner diameter of the second cylindrical portion 15 is smaller than the inner diameter of the third cylindrical portion 16. Has been formed. As a result, the housing 1
The inner circumference of No. 1 is formed in a multi-stage substantially cylindrical shape in which the diameter expands stepwise on the output shaft 52 side in the steering axis direction. A housing hole for housing each component of the integrated EPS 1 is formed on the output shaft 52 side of the housing 11. And
When the housing of each component is completed, the split housing 12
The accommodation hole is blocked.

As shown in FIG. 3, the housing 11
A guide groove 25 for a signal line that connects the Hall IC 22 and the control board 32 is formed in the. Furthermore, Hall IC
A notch 26 is formed to prevent the position of the magnetism collecting ring 22 from deviating from the magnetism collecting ring 21.

The torque sensor 2 includes a steering wheel 6 (see FIG.
The steering torque from (see) is detected. As shown in FIG. 5, the torque sensor 2 includes a magnetism collecting ring 21, a Hall IC 22, a yoke 23, a magnet 24, and the like.

The yoke 23 is cylindrical and has an input shaft 51.
Is arranged on the outer periphery of the. The magnetism collecting ring 21 has a ring shape and is arranged on the outer periphery of the yoke 23. Further, a flat plate-shaped magnetism collecting portion 21a is provided at one location in the circumferential direction, and the magnetism collecting portions 21a are arranged so as to face each other in the axial direction. However, the magnetism collecting part 21 a is provided axially closer to the other part of the magnetism collecting ring 21. The Hall IC 22 is inserted between the magnetism collecting portions 21a facing each other in the axial direction. The magnet 24 has a cylindrical shape and is fixed to the outer periphery of the input shaft 51.

Then, when the input shaft 51 rotates, the magnetic flux density of the yoke 23 changes due to the magnet 24 fixed to the input shaft 51. The change in the magnetic flux density is collected in the magnetism collecting portion 21a of the magnetism collecting ring 21, and the Hall IC 22 detects it as an electrical signal, thereby forming the torque sensor 2 that detects the steering torque by detecting the relative angle.

The control circuit 3 determines the steering assist force based on the steering torque detection value detected by the torque sensor 2. As shown in FIG. 4, the control circuit 3 includes a power transistor 31, a control board 32, a cover 33, and the like.

The power transistor 31 has a housing 1
It is fixed to 1 and plays a role of switching of power supply for operating the electric motor 4. The control board 32 is connected to the signal line of the Hall IC 22 and controls the power transistor 31 based on the detection value of the Hall IC 22. The cover 33 is a thin plate of soft magnetic steel and covers the power transistor 31 and the control board 32, and the electric motor 4 and the Hall IC.
It is arranged between the two. These control circuits 3 are connected to a connector 10 (see FIG. 2) that supplies power from a battery 7 (see FIG. 1) of the vehicle. This connector 1
0 is connected to the connecting portion formed on the side surface of the cover 33.

The electric motor 4 outputs the steering assist force determined by the control circuit 3. As shown in FIG.
The electric motor 4 includes a brush 41, a brush holder 42, a magnet 43, a commutator 44, a core 45, and the like.

The brush 41 is connected to a power supply line (not shown) from the control circuit 3 and plays a role of power supply. The brush holder 42 fixes the brush 41. The magnet 43 is cylindrical and has a plurality of N poles and S poles alternately magnetized. The commutator 44 is fixed to the inner circumference of the brush 41. The core 45 is a laminated layer and is arranged on the inner circumference of the magnet 43.

Then, an electric current flows from the commutator 44 to the coil provided in the core 45, and the magnetic flux of the magnet 43 causes the core 45 to rotate.

Further, one end of the torsion bar 57 in the axial direction is connected to the input shaft 51 via the pin 8, and the other end is connected to the output shaft 52 via the pin 9.
The output shaft 52 is rotatably supported via the bearing 13.

The power transmission unit 5 transmits the steering assist force output from the electric motor 4 to the steered wheels. As shown in FIG. 6, the power transmission unit 5 includes a worm 58, a worm wheel 59, and the like.

The worm 58 is connected to the rotary shaft of the electric motor 4. Worm wheel 59 is worm 5
8 and is coupled to the output shaft 52.

The worm 58 rotates simultaneously with the rotation of the electric motor 4. And the worm wheel 59
Is a power transmission unit 5 that is rotated by the rotation of the worm 58 and that transmits the steering assist force to the output shaft 52.

In the EPS constructed as described above, the integrated EPS 1 is constructed such that when the input shaft 51 is rotated by the steering force from the steering 6, the torsion bar 57 is twisted and the output shaft 52 is rotated. To do. And the magnet 2
The change in the relative angle between the No. 4 and the yoke 23 is detected by the Hall IC 22 and output to the control circuit 3. The control circuit 3 determines the steering assist force according to the detected steering torque value of the Hall IC. Then, the steering assist force is output by the electric motor 4, and the output thereof is boosted by the reduction mechanism of the power transmission unit 5, and the steering assist force is transmitted to the output shaft 52.

In this embodiment, the steering rack 54
Since the integrated EPS 1 is arranged in the vicinity, the distance between the output shaft 52 and the pinion gear becomes minute. Therefore, the steering shaft is less likely to be affected by the twist of the steering shaft, and thus the steering assist force output from the integrated EPS 1 can be directly transmitted to the steering rack. As a result, a large steering assist force can be transmitted. Therefore, the rack type EPS is mainly applied to large vehicles.

Further, since only one vehicle harness 17 is required for the external connection portion with the vehicle, the connection can be easily made. Further, the connector 10 of the vehicle harness 17
Since it is also possible to connect a serial communication line, the number of parts does not increase.

Further, the steering rack 54 may penetrate the integrated EPS 1. Therefore, since the housing 11 of the integrated EPS 1 and the steering rack housing 53 can be integrally formed, the number of parts can be reduced.

Further, the housing 11 is formed in a single piece. As a result, when assembling, there is no need to perform screwing for connecting the housings to each other, so that the number of parts and the number of assembling steps can be reduced. Further, the output shaft 5 in the steering shaft direction is provided on the inner circumference of the housing 11.
Since it is formed in a multi-stage substantially cylindrical shape whose diameter expands to the 2 side, each component of the EPS can be assembled in the housing 11.

The torque sensor 2 is a Hall IC 22.
Is used to detect the steering torque. By this,
Hard magnetic magnet 24 fixed to the input shaft 51
Since it is not necessary to directly detect the magnetic flux generated from
There is no need to provide an electrical contact portion for the Hall IC 22. Therefore, a highly reliable torque sensor can be provided.

A cover 33, which is a soft magnetic material for covering the control circuit 3, is arranged between the Hall IC 22 and the electric motor 4. As a result, the influence of the magnetic force generated by the magnet 43 can be prevented. Also,
Since the Hall IC 22 can be arranged near the control circuit 3, the wiring connecting the Hall IC 22 and the control board 32 can be shortened.

A hole I is formed on the inner circumference of the housing 11.
A guide groove 25 for arranging a signal line connecting the C22 and the control board 32 is formed. As a result, the signal line of the Hall IC 22 connected to the control board 32 can be easily wired, and the assemblability is improved.

Further, the housing 11 has a Hall IC.
22 and a notch 26 for determining the position of the magnetism collecting ring 21. Because of this, Hall IC
Since the positions where 22 and the magnetism collecting ring 21 are arranged can be accurately determined, it is possible to prevent positional deviation. Further, since the Hall IC 22 is easily fitted into the magnetism collecting ring 21, the assembling property is improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a rack type EPS in the present embodiment.

FIG. 2 is a plan view of the integrated EPS according to the present embodiment as viewed from above in the axial direction.

FIG. 3 is a plan view of the torque sensor according to the present embodiment as viewed from above in the axial direction.

FIG. 4 is a sectional view taken along the line AA of FIG. 2 in the present embodiment.

5 is a cross-sectional view taken along the line BB of FIG. 2 in the present embodiment.

FIG. 6 is a sectional view taken along the line CC of FIG. 4 in the present embodiment.

[Explanation of symbols]

1 ... Integrated EPS, 2 ... torque sensor, 3 ... Control circuit, 4 ... electric motor, 5 ... power transmission part, 6 ... Steering, 7 ... battery, 8, 9 ... pins, 10 ... Connector, 11 ... Housing, 12: split housing, 13 ... Bearings 14 ... The first cylindrical portion, 15 ... The second cylindrical portion, 16 ... Third cylindrical shape portion, 17 ... Vehicle harness, 21 ... Magnetic flux collecting ring, 22 ... Hall IC, 23 ... York, 24, 43 ... Magnet, 25 ... Guide groove, 26 ... Notch, 31 ... Power transistor, 32 ... Control board, 33 ... cover, 41 ... brush, 42 ... Brush holder, 44 ... commutator, 45 ... Core, 51 ... input shaft, 52 ... Output shaft, 53 ... Steering rack housing, 54 ... Steering rack, 55 ... tire hinge, 56 ... tires 57 ... torsion bar, 58 ... warm, 59 ... Worm wheel, 60 ... Universal joint.

Claims (7)

[Claims] 1. A torque sensor (2) for detecting a steering torque from a steering wheel (6); a control circuit (3) for determining a steering assist force based on a detection value detected by the torque sensor; The steering assist force determined by the control circuit is output to the output shaft (5
Electric power steering including an electric motor (4) applied to 2) and a power transmission unit (5) having a worm wheel (59) for transmitting the steering assist force output from the electric motor to the steered wheels. The device includes a single housing (11) that houses the torque sensor and the power transmission unit, and the diameter of the housing is increased stepwise on the output shaft side in the steering axis direction on the inner periphery of the housing. A multi-stage substantially cylindrical shape, a first cylindrical portion (14) for disposing the torque sensor, and a second bearing (13) for supporting the output shaft.
An electric power steering device comprising a cylindrical portion (15) and a third cylindrical portion (16) in which the worm wheel is disposed in this order. 2. The electric power steering apparatus according to claim 1, wherein the torque sensor detects the steering torque using a Hall IC (22) which is a magnetic sensor. 3. The control circuit has a cover (33) which is a soft magnetic material, and the control circuit is arranged between the Hall IC and the electric motor. The electric power steering device according to Item 1 or 2. 4. A guide groove (25) for arranging a signal line for connecting the Hall IC and a control board (32) of the control circuit is formed on an inner peripheral surface of the housing. The electric power steering device according to claim 2 or 3. 5. The Hall-collecting ring (21) is the Hall IC.
5. The magnetic flux density is concentrated on the housing, and the housing is formed with a notch (26) for positioning the Hall IC and the magnetism collecting ring. The electric power steering device according to any one of claims. 6. The electric power steering apparatus according to claim 1, wherein the housing is arranged in the vicinity of the steering rack (54) of the steering shaft. 7. The electric power steering apparatus according to claim 6, wherein the steering rack penetrates the housing.