JP3389716B2 - Electric power steering device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus used for a vehicle such as an automobile. [0002] 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 corresponding to a set current value of the control circuit to the electric motor. The control circuit and the drive circuit are housed in a rectangular parallelepiped substrate housing case arranged at a position distant from the steering system. However, when the substrate housing case is arranged at a position distant from the steering system in this way, the space in which the substrate housing case is arranged hinders miniaturization 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,
Thus, there has been proposed an apparatus in which the space for disposing the substrate housing case is not required and the apparatus is downsized (see Japanese Utility Model Application Laid-Open No. 63-69671). [0004] In such an electric power steering apparatus, since the space inside the rack shaft housing is limited, the control circuit and the drive circuit are separated from each other and are arranged separately in the housing. ing. However, when the control circuit and the drive circuit are separated in this manner, not only is a new harness or connector required to connect the circuits necessary, but also a circuit 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 that elements causing a failure or the like (for example, deterioration or poor connection of the harness or connector) increase, and the reliability of the device decreases. SUMMARY OF THE INVENTION The present invention has been made to solve such inconveniences, and it is possible to reduce the size as well as the cost and to improve the reliability. It is an object to provide an electric power steering device. 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; A motor for applying a steering assist torque via a reduction gear mechanism, a control circuit for setting a current value for the motor based on an output signal from the steering torque detector, and a drive current corresponding to a set current value by the control circuit A drive circuit that supplies the motor to the motor, the control circuit and the drive circuit are integrally disposed on a deformable circuit board,
The bottom plate has a central part in the housing of the reduction gear mechanism.
Behind the bottom plate is formed in a mountain-shaped section so as to be convex
Side surface forms a part of the outer surface of the housing into the shape of the outer surface.
Provide a board storage case that covers along
The serial circuit board, the cross-sectional shape by bending a central portion thereof
Deforms substantially the same as the bottom plate and accommodates the substrate
In the case, cover the bottom plate and
Each of the parts on both sides of the center part
Characterized in that the set only to be fixed. [0007] According to the present invention, a control circuit and the drive circuit is disposed integrally with the circuit board, the circuit board is, in <br/> Haujin grayed-reducing gear mechanism, the outer surface of the housing since it is provided deformed to cover along a part on the outer surface shape, enabling the size of the apparatus without separating each circuit. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory schematic diagram for explaining a basic configuration of an electric power steering apparatus according to one embodiment of the present invention, FIG. 2 is a partially detailed view of FIG. 1, and FIG. It is. Referring to FIG. 1, reference numeral 1 denotes a steering shaft.
Is composed of an input shaft 3 and an output shaft 4 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 an upper end thereof. A pinion shaft 7 is connected to a lower end of the output shaft 4 via a universal joint 6. A 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, when the driver operates the steering wheel 5
The steering force generated by steering the input shaft 3
The power is transmitted to the steered wheels 10 via the torsion bar 2, the output shaft 4, the pinion shaft 7, the pinion 7a, and the rack shaft 9. In this embodiment, the steering system A is composed of 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. In the present embodiment, the housing 3a of the input shaft 3 and the housing 8 of the rack shaft 9 are used as housings of members constituting the steering system A. However, the present invention is not limited to this, and housings of other members may be provided. . A steering torque sensor 11 for detecting a steering torque input to the steering shaft 1 is provided on the input shaft 3.
Is provided. The steering torque sensor 11 is operated by turning the steering wheel 5 by the driver.
It outputs a steering torque detection signal according to the magnitude and direction of the twist generated in the steering shaft 1. 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 a gear housing 15. The worm 16 is fixed to the drive shaft 14 of the electric motor 13,
Are fixed to the output shaft 4. The rotational force of the electric motor 13 is controlled by the drive shaft 14, the worm 16, and the worm wheel 1.
7 to the output shaft 4. By transmitting the rotational force, a steering assist torque is applied to the output shaft 4 so that the steering torque is reduced, and the burden on the driver is reduced. The torque 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.
This is a control device that controls the rotational force of the electric motor 13 in accordance with the direction and magnitude of the steering torque generated in the motor. 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.
A current value for the electric motor 13 is set on the basis of the steering torque detection signal from the controller, and the drive circuit 20 supplies a drive current corresponding to the set current value to the electric motor 13, so that the steering generated in the steering system A is performed. A torque corresponding to the direction and magnitude of the torque is generated on the drive shaft 14 of the electric motor 13, and the 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. The circuit board 21 is provided integrally with the gear housing 15 of the reduction gear mechanism 12. Board storage case 2
2 housed. The substrate housing case 22 is
3 is formed in a mountain-shaped cross section (see FIG. 3), and a surface 25 on the back side of the ridge 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. Is provided. A sidewall 26 is formed around the entire periphery of the bottom plate 23 so as to rise in a direction perpendicular to the bottom plate 23, and a space 27 for accommodating the flexible circuit board 21 is formed in a space surrounded by the bottom plate 23 and the sidewall 26. still,
In the present embodiment, the bottom plate 23 and the side wall 26 of the substrate housing case 22 are formed integrally with the gear housing 15. However, the present invention is not limited to this, and the bottom plate 23 may be fixed to the gear housing 15 by bolts, welding, or the like. Good. The flexible circuit board 21 has a central portion bent 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. The upper opening of the storage space 27 is covered with a lid 29 so as to be freely opened and closed. The lid portion 29 is formed to have substantially the same cross-sectional shape 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 substrate housing case 22 is provided integrally with the gear housing 15 disposed close to the steering system A, and the flexible circuit board 21 is housed in the substrate housing case 22.
As in the related art, a space for disposing the board housing case at a position away from the steering system A is not required, and the flexible circuit board 21 is partially covered on the outer surface of the gear housing 15 so as to cover the shape of the outer surface. Bend and arrange,
By forming the board housing case 22 for housing the flexible circuit board 21 along the shape of the circuit board 21, the board housing case 22 can be prevented from protruding from the gear housing 15 and taking up space. ,
Since the substrate housing case 22 is compact, the size of the apparatus can be effectively reduced. The control circuit 19 and the drive circuit 20
Since they are arranged on the same circuit board 21, a new harness and connector for connecting the control circuit 19 and the control circuit 20 which were conventionally required are not required, and furthermore, a board housing case for housing the control circuit 19 and the drive circuit 20. Since only one 22 is required, the product cost can be greatly reduced as compared with the related art. Further, since a new harness or connector for connecting the control circuit 19 and the control circuit 20 is not required,
As in the past, there is no increase in factors that cause failures (for example, deterioration of the harness or connector or poor connection),
The high reliability of the device can be favorably maintained. Ma
Was, in the above embodiment, are arranged a flexible circuit board 21 to the outer surface of the gear housing 15, formate Ya housing 15 steering torque sensor 1 is connected to the control unit 18
1 and the electric motor 13 are disposed close to each other, so that the flexible circuit board 21 is disposed on the gear housing 15 .
Is arranged in the input shaft housing 3a, for example.
It is more effective than . In the above embodiment, the flexible circuit board 21 is employed as a deformable circuit board.
There is no particular limitation as long as it is a deformable circuit board. Further, in the above-described embodiment, the electric motor 13 is connected to the output shaft 3 via the reduction gear mechanism 12, but instead of this,
The electric motor 1 is connected to a pinion shaft 7 via a reduction gear mechanism 12.
3 may be connected. In this case, the flexible circuit board 21 is mounted on the gear housing 15 disposed on the pinion shaft 7.
Place. As is apparent from the above description, according to the present invention, the size of the apparatus can be reduced without separating the control circuit and the drive circuit, so that the product cost can be reduced. It can be held down and the reliability of the device can be maintained well.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory schematic diagram for explaining a basic configuration of an electric power steering device according to an embodiment of the present invention. FIG. 2 is a partial detailed view of FIG. 1; FIG. 3 is a sectional view taken along line − in FIG. 2; [Description of Signs] 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

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-185938 (JP, A) JP-A-6-61591 (JP, A) JP-A-3-27315 (JP, U) JP-A-59-159 56789 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) B62D 5/04 H05K 7/14

Claims (1)

(57) [Claim 1] A steering torque detector for detecting a steering torque input to a steering system, an electric motor for applying a steering assist torque to the steering system via a reduction gear mechanism, A control circuit for setting a current value for the motor based on an output signal from the steering torque detector; and a drive circuit for supplying a drive current to the motor according to a current value set by the control circuit; It arranged integrally with the driving circuit as the deformable circuit board, the housing of the reduction gear mechanism, a bottom plate
Is formed in a mountain-shaped cross-section such that the central part is convex, and
The rear surface of the bottom plate forms part of the outer surface of the housing.
A substrate housing case adapted to cover the shape of the outer surface.
A circuit board, and bending the circuit board at a central portion thereof.
With its cross-sectional shape being substantially the same as that of the bottom plate,
To, in the substrate housing case, 且so as to cover the bottom plate
That of the parts on both sides sandwiching the bent central part
An electric power steering apparatus characterized by a set only so that, respectively fixed to the bottom plate.