JPH08150945A - Motor-driven power steering device - Google Patents

Abstract

PURPOSE: To provide a motor-driven power steering device by which not only downsizing can be attained but also cost can be restrained low and reliability can be enhanced. CONSTITUTION: A control circuit 19 and a driving circuit 20 are arranged on a deformable flexible circuit board 21. The circuit board 21 is arranged in a deformed shape in a gear housing 15 of a speed reduction gear mechanism so as to cover a part of an outside surface of the housing along an outside surface shape.

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 device used in vehicles such as automobiles.

[0002]

2. Description of the Related Art As an electric power steering device,
A steering torque detector that detects a steering torque input to a steering system, an electric motor that applies a steering assist torque to the steering system, and a control circuit that sets a current value for the electric motor based on an output signal from the steering torque detector. And a drive circuit that supplies a drive current according to the set current value of the control circuit to the electric motor is known. The control circuit and the drive circuit are housed in a rectangular parallelepiped board housing case arranged at a position away from the steering system.

However, when the board housing case is arranged at a position distant from the steering system in this manner, the space for housing the board housing case hinders downsizing of the apparatus. Therefore, the control circuit and the drive circuit are arranged in the housing of the rack shaft, which is one of the members constituting the steering system,
As a result, there has been proposed a device in which the space for disposing the substrate housing case described above is unnecessary and the device is downsized (see Japanese Utility Model Laid-Open No. 63-69671).

[0004]

In such an electric power steering apparatus, since the space within the rack shaft housing is limited, the control circuit and the drive circuit are separated from each other and arranged in the housing. However, if the control circuit and the drive circuit are separated in this way, not only a new harness or connector for connecting each circuit is required, but also a board housing case is required for each circuit, which increases the product cost. There is. Also,
Since each circuit is connected by a new harness or connector, there is a problem in that the number of elements that cause a failure (for example, deterioration of the harness or connector, connection failure, etc.) increases and the reliability of the device decreases.

The present invention has been made in order to eliminate such inconvenience, and it is possible to reduce the size as well as to reduce the cost and improve the reliability. An object is to provide an electric power steering device.

[0006]

In order to achieve the above object, an electric power steering apparatus according to the present invention comprises a steering torque detector for detecting a steering torque input to a steering system, and a reduction gear mechanism for the steering system. An electric motor for applying a steering assist torque via a motor, a control circuit for setting a current value for the electric motor based on an output signal from the steering torque detector, and a drive current according to the set current value by the control circuit for the electric motor. A drive circuit for supplying the control circuit and the drive circuit to a deformable circuit board,
The circuit board is provided in one of the housing of the member forming the steering system and the housing of the reduction gear mechanism by being deformed so as to cover a part of the outer surface of the housing along the outer surface shape. It is characterized by

[0007]

According to the present invention, the control circuit and the drive circuit are integrally arranged on the circuit board, and the circuit board is provided in either the housing of the member forming the steering system or the housing of the reduction gear mechanism, Since it is provided so as to be deformed so as to cover a part of the outer surface of the housing along the outer surface shape, the device can be downsized without separating each circuit.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory schematic diagram for explaining the basic configuration of an electric power steering apparatus that is an embodiment of the present invention, FIG. 2 is a partial detailed view of FIG. 1, and FIG. Is. Referring to FIG. 1, reference numeral 1 is a steering shaft, and this steering shaft 1
Is composed of an input shaft 3 and an output shaft 4 which are connected via a torsion bar 2. The input shaft 3 is inserted into a cylindrical input shaft housing 3a, and a steering wheel 5 is fixed to the upper end thereof. A pinion shaft 7 is connected to the lower end of the output shaft 4 via a universal joint 6. The pinion 7 provided at the lower end of the pinion shaft 7
a meshes with the teeth of the rack shaft 9 inside the rack shaft housing 8. Therefore, the driver can
The steering force generated by steering the
It is transmitted to the steered wheels 10 via the torsion bar 2, the output shaft 4, the pinion shaft 7, the pinion 7 a and the rack shaft 9.

Here, in the present embodiment, the steering system A is constituted by the steering wheel 5, the input shaft 3, the output shaft 4, the torsion bar 2, the universal joint 6, the pinion shaft 7, the pinion 7a and the rack shaft 9. are doing. Further, in the present embodiment, the housing 3a of the input shaft 3 and the housing 8 of the rack shaft 9 are the housings of the members constituting the steering system A, but the present invention is not limited to this, and the housings of other members may be provided. .

A steering torque sensor 11 for detecting the steering torque input to the steering shaft 1 is provided on the input shaft 3.
Is provided. The steering torque sensor 11 allows the driver to steer the steering wheel 5,
A steering torque detection signal corresponding to the magnitude and direction of the twist generated in the steering shaft 1 is output. Output shaft 4
Is connected to a drive shaft 14 of an electric motor 13 via a reduction gear mechanism 12. The reduction gear mechanism 12 includes a worm 16 and a worm wheel 17 that mesh with each other in the gear housing 15. The worm 16 is fixed to the drive shaft 14 of the electric motor 13, and the worm wheel 17
Are fixed to the output shaft 4. The rotating force of the electric motor 13 is generated by the drive shaft 14, the worm 16, and the worm wheel 1.
It is adapted to be transmitted to the output shaft 4 via 7. By transmitting the rotational force, steering assist torque is applied to the output shaft 4 to reduce the steering torque, and the burden on the driver is reduced. Then, the rotational force of the electric motor 13 is controlled according to the direction and magnitude of the steering torque generated in the steering system A.

1 to 3, reference numeral 18 denotes a steering system A.
The control device controls the rotational force of the electric motor 13 in accordance with the direction and magnitude of the steering torque that is generated in the. The control device 18 includes a control circuit 19 and a drive circuit 20, and its basic operation is as follows. That is,
The control circuit 19 controls the steering torque sensor 11 described above.
The electric current value for the electric motor 13 is set based on the steering torque detection signal from the electric motor 13 and the drive circuit 20 supplies the electric current to the electric motor 13 according to the set electric current value, so that the steering system A is operated. A torque corresponding to the direction and magnitude of the torque is generated on the drive shaft 14 of the electric motor 13, and this torque acts on the output shaft 4 as steering assist torque.

As shown in FIG. 3, the control circuit 19 and the drive circuit 20 are arranged on a deformable flexible circuit board 21, and the circuit board 21 is provided integrally with the gear housing 15 of the reduction gear mechanism 12. Board housing case 2
It is housed in 2. The board housing case 22 includes the bottom plate 2
3 is formed in a mountain shape (see FIG. 3) in cross section, and the surface 25 on the back side of the ridge line portion 24 of the mountain of the bottom plate 23 covers a part of the outer surface of the gear housing 15 along the shape of the outer surface. It is provided. A side wall 26 is formed upright around the entire periphery of the bottom plate 23 in a direction perpendicular to the bottom plate 23, and an accommodation space 27 for the flexible circuit board 21 is formed in a space surrounded by the bottom plate 23 and the side wall 26. still,
In this embodiment, the bottom plate 23 and the side wall 26 of the substrate housing case 22 are formed integrally with the gear housing 15, but the present invention is not limited to this, and the bottom plate 23 may be fixed to the gear housing 15 by bolts or welding. Good.

The flexible circuit board 21 is bent at the center so that its cross-sectional shape is substantially the same as that of the bottom plate 23, and is supported by the support member 28 in parallel with the bottom plate 23. Thereby, the flexible circuit board 21 is provided so as to cover a part of the outer surface of the gear housing 15 along the shape of the outer surface. A lid 29 is configured to openably and closably cover the upper opening of the accommodation space 27. The lid 29 is formed so that its cross-sectional shape is substantially the same as the bottom plate 23, and its peripheral edge is fixed to the upper end surface of the side wall 26 by screwing or the like.

In such an electric power steering apparatus, the board housing case 22 is integrally provided in the gear housing 15 arranged in the vicinity of the steering system A, and the flexible circuit board 21 is housed in the board housing case 22.
A space for disposing the board housing case at a position away from the steering system A is not required unlike the conventional case, and moreover, the flexible circuit board 21 is covered on a part of the outer surface of the gear housing 15 along the shape of the outer surface. Bend and place,
By forming the board housing case 22 for housing the flexible circuit board 21 along the shape of the circuit board 21, it is possible to prevent the board housing case 22 from protruding from the gear housing 15 and taking up space. ,
The substrate housing case 22 becomes compact and the size of the device can be effectively reduced.

Further, the control circuit 19 and the drive circuit 20 are
Since they are arranged on the same circuit board 21, a new harness or connector for connecting the control circuit 19 and the control circuit 20, which has been conventionally required, is unnecessary, and moreover, a board housing case for housing the control circuit 19 and the drive circuit 20 is provided. Since only one 22 is sufficient, the product cost can be significantly reduced as compared with the conventional one.

Further, since a new harness or connector for connecting the control circuit 19 and the control circuit 20 is unnecessary,
As in the past, the number of factors that cause failures (such as deterioration of harnesses and connectors and poor connections) does not increase,
The high reliability of the device can be favorably maintained. still,
In the above embodiment, the flexible circuit board 21 is arranged on the outer surface of the gear housing 15, but instead, the flexible circuit board 21 is arranged on the outer surface of the rack shaft housing 8 or the input shaft housing 3a in the same manner as described above. You can also However, the gear housing 15 is the controller 1
Steering torque sensor 11 and electric motor 1 connected to
Since 3 is arranged in the vicinity, it is more effective to arrange the flexible circuit board 21 in the gear housing 15 when connecting them.

In the above embodiment, the flexible circuit board 21 is used as the deformable circuit board.
There is no particular limitation as long as it is a deformable circuit board. Further, in the above embodiment, the electric motor 13 is connected to the output shaft 3 via the reduction gear mechanism 12, but instead of this,
Electric motor 1 via pinion shaft 7 via reduction gear mechanism 12
3 may be connected. In this case, the flexible circuit board 21 is attached to the gear housing 15 arranged on the pinion shaft 7.
To place.

[0018]

As is apparent from the above description, according to the present invention, it is possible to reduce the size of the device without separating the control circuit and the drive circuit, so that the product cost can be kept low. In addition, the reliability of the device can be maintained well.

[Brief description of drawings]

FIG. 1 is an explanatory schematic diagram for explaining a basic configuration of an electric power steering apparatus that is an embodiment of the present invention.

FIG. 2 is a partial detailed view of FIG.

FIG. 3 is a sectional view taken along line − in FIG. 2;

[Explanation of symbols]

 A ... Steering system 1 ... Steering shaft 2 ... Torsion bar 3 ... Input shaft 3a ... Input shaft housing 4 ... Output shaft 5 ... Steering wheel 6 ... Universal joint 7 ... Pinion shaft 8 ... Rack shaft housing 9 ... Rack shaft 11 ... Steering torque Sensor 12 ... Reduction gear mechanism 13 ... Electric motor 15 ... Gear housing 19 ... Control circuit 20 ... Drive circuit 21 ... Flexible circuit board

Claims (1)

[Claims] 1. A steering torque detector that detects a steering torque input to a steering system, an electric motor that applies a steering assist torque to the steering system via a reduction gear mechanism, and an output signal from the steering torque detector. A control circuit that sets a current value for the electric motor based on the control circuit, and a drive circuit that supplies a drive current according to the set current value by the control circuit to the electric motor, and the control circuit and the drive circuit can be modified. A single circuit board, and the circuit board is mounted on either the housing of the member forming the steering system or the housing of the reduction gear mechanism, and a part of the outer surface of the housing follows the outer surface shape. An electric power steering device characterized by being provided so as to be transformed so as to cover it.