Electric power steering device and method of assembling the same

Abstract

To provide an electric power steering apparatus in which it is possible to minimize a connection distance between a control unit and an electric motor and surely prevent electric noise from mixing between the control unit and the electric motor as well as to minimize electric resistance and minimize an electric loss by directly connecting the control unit and connection terminals of the electric motor and a torque sensor. A motor control apparatus includes a steering column 3 having inserted therein a steering shaft 2 to which steering torque is transmitted, a reduction gear box 4 coupled to the steering shaft 2, and an electric motor 5 that transmits a steering assisting force to the steering shaft 2 via a reduction mechanism in the reduction gear box 4. The electric motor 5 and a control unit 19 including a control board mounted with a control circuit that controls to drive the electric motor 5 are provided side by side in the reduction gear box 4 and a connection terminal of the electric motor 5 is electrically connected to the control unit 19 directly.

Description

technical field [0001] The present invention relates to an electric power steering device and a method for assembling the same. The mechanism transmits steering power to the steering column. Background technique [0002] As a conventional electric power steering apparatus, for example, there has been proposed an electric power steering apparatus in which a motor is housed in a rack case or a part of a steering gear case that accommodates or mounts a rack shaft in a slidable manner, and the motor is housed to drive the motor. The housing of the control board of the control is formed on the rack case or the steering gear case, when the control board inserted from the opening abuts against a mounting boss formed on the bottom of the housing opposite to the opening The substrate connection terminals provided on the control substrate are electrically connected to the motor-side connection terminals protruding from the motor and provided in the housing (for example, refer to Japa...

AI Technical Summary

Problems solved by technology

[0005] However, in the conventional examples described in the above-mentioned Patent Documents 1 to 4, there is such a structure that in a so-called rack-type electric power steering device in which a motor is accommodated in a part of a rack case or a steering gear case, the motor-side connection terminal It is electrically connected to the board-side connection terminals provided on the control board, and directly assembled without intervening an electrical connection wire between the motor and the control board. Thus, the wiring length between the motor and the control board can be reduced to The shortest, can prevent electrical noise from mixing, and can reduce wiring resistance and reduce electrical loss. However, the torque detection value of the torque sensor that detects the torque transmitted to the steering shaft must be input to the control board that controls the motor. In general, the torque sensor is usually installed on the side of the steering wheel away from the rack box or steering gear box, and a long connection cable must be installed between the torque sensor and the control board, so there is an unsolved problem: Electrical noise is mixed in the connecting cable, and electrical loss increases due to the increase in resistance

[0006] Also, in the conventional example described in Patent Document 1, since the electric motor has a direct motor structure, it is not necessary to perform phase matching for connecting the electric motor to the speed reduction mechanism. In the electric power steering device of the shape, since the electric motor and the reduction mechanism need to be fitted with splines or triangular splines, when the electric motor is connected to the reduction mechanism, it is necessary to perform phase matching while rotating the electric motor itself. In this case, there is an unsolved problem that the structure in Patent Document 1 cannot cope with

[0007] Furthermore, in the conventional example described in the aforementioned Patent Document 1, unless the positions of the male terminal on one side and the female terminal on the other side of the motor-side connection terminal and the board-side connection terminal are not set with high precision, Then, at the time of connection, residual stress is generated on the male terminal and the female terminal that are in contact with each other in a crimped state, so there is a problem in extending the service life of the board side connection terminal and the motor side connection terminal.

On the other hand, if the positions of the male terminal and the female terminal are set with high precision so that no residual stress occurs during connection, there is a problem in terms of manufacturing cost

[0008] In addition, the conventional example described in the above-mentioned Patent Document 5 has a structure in which a power board, a large current board, and a control board constituting a control device for controlling an electric motor are laminated and built in a case and a cover. In the body, the cover is directly installed on the electric motor; although it will generate heat in the control device, the electric motor is also a heat source, so the heat in the control device cannot be efficiently transferred to the device with large heat capacity and surface area through the electric motor. As a countermeasure, the gear box of a large speed reducer is equipped with heat dissipation fins to improve heat dissipation. However, there is an unsolved problem that the size of the control device cannot be avoided due to the installation of heat dissipation fins.

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