JPH0615332B2 - Electric power steering device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering device that applies an auxiliary torque to a shaft that is rotated by rotation of a handle by an electric motor.

(Prior Art) Generally, a steering shaft rotates at a low speed and requires a high torque. On the other hand, the electric motor that drives the steering shaft rotates at high speed and has low torque. For this reason,
Although the speed reduction mechanism was provided between the steering shaft and the electric motor, since the speed reduction mechanism is generally composed of gears, there were problems in terms of noise generation by the gears, rotational force transmission efficiency, and the like.

(Problems to be Solved by the Present Invention) Conventionally, JP-A-59-206259 discloses a solution to the problem.
And Japanese Patent Laid-Open No. 57-47251,
In the former case, although the noise of the gear is eliminated, there is a drawback that the structure is complicated and expensive because the screw ball system is adopted. In the latter, although the pinion shaft is directly rotated by the electric motor to eliminate the rotational force transmission efficiency, the electric motor is attached to the tip of the pinion shaft, which causes a problem in the space occupied by the electric motor. There were none, and none were satisfactory.

An object of the present invention is to provide an electric power steering device that can solve all of the above problems.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a rotor that is coaxially fixed to a shaft that is driven by rotation of a handle, and a rotor that is close to the rotor. An encoder fixed coaxially with respect to the portion, a stator arranged to face the rotor and giving a torque to the rotor, and a rotational position detection for detecting a rotational position by a signal output from the encoder. It is characterized in that it comprises a controller having means and electronic switching means, and a brushless direct drive motor.

(Operation of the present invention) Since the rotor of the direct drive motor is coaxially fixed to the shaft, the shaft is directly rotated by the direct drive motor.

(Effect of the present invention) Since the shaft is directly rotated by the direct drive motor, no reduction gear is required. Therefore, the structure is simplified, noise is not generated by the gears, and the rotation efficiency of the shaft is further improved. In addition, since the rotor of the direct drive motor is coaxially installed on the shaft, it does not take up a lot of space to install the direct drive motor. In addition, the direct drive motor is brushless, so low speed and high torque can be realized. ..

(Embodiment of the present invention) In FIG. 1, 1 is a steering shaft that transmits the rotational force of the handle 3 to the pinion shaft 5, 7 is a brushless direct drive motor that gives high torque to the pinion shaft 5 at low speed, and 9 is Pinions meshing with the rack 11, 13 are side rods, and 14 are wheels.

As shown in FIG. 2, the rotor 15 of the direct drive motor 7 is coaxially fixed to the pinion shaft 5 between the pinion 9 and the serration 12 connected to the steering shaft 1. Reference numeral 17 is a position facing the rotor 15, and is a stator of a direct drive motor fixed to the housing 19, and a coil 21 that applies a torque to the rotor 15 is wound. An encoder 23 generates several tens of pulses for each rotation of the direct drive motor 7, that is, for each rotation of the pinion shaft 5.
Further, the pinion shaft 5 is a bearing 2 provided in the housing 19.
It is rotatably supported by the housing 19 by bearings 5 and 27 and a bearing 31 provided on the cover 29.

FIG. 3 is a block diagram of a control device for controlling the direct drive motor 7. Reference numeral 41 is a vehicle speed sensor for detecting a vehicle speed and outputting a vehicle speed signal, and 42 is a torque transmitted to the steering shaft 1 by rotation of the steering wheel 3. A torque sensor that outputs a torque signal based on the vehicle speed signal, 43 is a signal output from each sensor, and a torque signal is input by a controller that includes a detection unit and a switching unit that detects the rotational position from the encoder. Then, the driving force of the direct drive motor 7 is calculated, and a control signal corresponding to the calculated driving force is output. Reference numeral 44 is a driver that outputs a current according to the control signal to drive the direct drive motor 7.

Next, the operation of the embodiment configured as described above will be described.

When the steering wheel 3 is rotated, torque is transmitted to the steering shaft 1, and the torque sensor 42 detects the torque and outputs a torque signal. When the controller 43 receives the torque signal, the controller 43 calculates the driving force of the direct drive motor according to the vehicle speed signal output from the vehicle speed sensor 41, and outputs the control signal according to the calculated driving force.
Then, the driver 44 outputs a current according to the control signal.

This current flows through the coil 21 of the stator 17, and the rotor 15 rotates at high speed with low torque. Due to the high torque rotation of the rotor 15, the pinion shaft 5 rotates together with the rotor 15,
This rotation causes the rack 11 to move horizontally in FIG. 1 to steer the wheels 14.

In this way, the high torque rotation of the rotor 15 allows the pinion shaft 5 to be directly rotated without providing a speed reducing mechanism, so that the structure is simplified.

When the rotation of the handle 3 is stopped, the output of the torque signal output from the torque sensor 42 is stopped. This stops the output of the control signal of the controller 43, and the driver 44
The output of the current is stopped and the rotation of the direct drive motor 7 is stopped. As a result, the turning of the wheels 14 is stopped.
Therefore, the wheels 14 are steered according to the rotation angle of the steering wheel 3.

Although the pinion shaft is rotated by the direct drive motor 7 in the above embodiment, the present invention is not limited to this, and the steering shaft may be rotated, for example. Further, although the case of the rack and pinion type has been described, it goes without saying that it can also be applied to a ball nut type, a worm sector type, a worm pin type and the like.

[Brief description of drawings]

FIG. 1 is a system diagram of an embodiment of the present invention, FIG. 2 is a sectional view of a steering portion of an electric power steering device according to the present invention, and FIG. 3 is a control block diagram of the electric power steering device. 1 ... Steering shaft 5 ... Pinion shaft 7 ... Direct drive motor 15 ... Rotor, 17 ... Stator

Claims (1)

[Claims] 1. A rotor that is coaxially fixed to a shaft that is driven by rotation of a handle, an encoder that is coaxially fixed to a portion close to the rotor, and a rotor that faces the rotor. A brushless direct drive motor, and a controller provided with a stator that applies a torque to the rotor, a rotation position detection unit that detects a rotation position based on a signal output from the encoder, and an electronic switching unit. An electric power steering device comprising: