JPH06344927A - Motor-driven power steering device - Google Patents

Abstract

PURPOSE:To obtain the large steering assisting power and the excellent steering feeling by suppressing the variation of the turning moment transmitted to a steering mechanism for each motor by using a plurality of motors having the phase in deflection each other, as a motor for applying the steering assisting power. CONSTITUTION:A motor-driven power steering device A connected with a steering device B holds a steering shaft 2 having a steering wheel 1 installed at the upper part, in a turnable manner in a steering column 3, and two motors 10 and 20 for assisting steering are installed on the steering column 3, oppositely in the reverse direction, having the steering shaft 2 interposed. Each tuning moment of two motors 10 and 20 is applied on the steering shaft 2 and transmitted to the steering mechanism B, and steering is assisted. As two motors 10 and 20, are used the motors having each small output having the phase in deflection each other, and the necessary steering assisting force is generated by simultaneously driving two motors through a controller 5.

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.

[0002]

2. Description of the Related Art Conventionally, in a light vehicle, an electric power steering device for transmitting a rotational force of a DC motor to a steering mechanism has been used to assist steering in accordance with a steering torque applied to a steering shaft. In this electric power steering device, a motor is attached to a steering column that holds a steering shaft, and the rotational force of the motor is applied to the steering shaft via, for example, a worm gear. Further, a torsion bar is interposed in the middle of the steering shaft, and when the steering wheel is operated,
Since the torsion bar is slightly twisted and a relative displacement occurs between the input shaft and the output shaft connected via the torsion bar, this relative displacement is detected by the torque sensor, and the direct current is detected based on this detection result. The input current to the motor is controlled to assist the steering force according to the steering torque applied to the steering shaft.

[0003]

The above electric power steering device is being applied to not only a light vehicle but also a normal vehicle because it is possible to perform fine control according to the running conditions. about,
A high-power DC motor is required to secure a desired steering assist force.

However, in a DC motor, cogging (torque fluctuation) occurs due to a change in magnetic flux when the rotor passes through the magnetic flux, and this cogging tends to increase as the motor has a higher output. Therefore, the electric power steering device for an ordinary vehicle has a problem that the steering feeling is deteriorated by the cogging. The present invention has been made in view of the above problems, and an object of the present invention is to provide an electric power steering device that can obtain a large steering assist force and has a good steering feeling.

[0005]

In order to achieve the above object, an electric power steering apparatus of the present invention drives a motor based on a steering torque applied to a steering shaft and applies a rotational force of the motor to a steering mechanism. In an electric power steering device that transmits steering assist, the plurality of motors are configured, and the phases of the motors are shifted from each other in order to suppress fluctuations in the rotational force transmitted to the steering mechanism. It is what

[0006]

According to the electric power steering apparatus having the above-described structure, a desired steering assist force can be obtained by a plurality of motors, and the phases of the motors are shifted from each other. Can be canceled out, and the fluctuation of the rotational force transmitted to the steering mechanism can be suppressed.

[0007]

Embodiments will be described in detail below with reference to the accompanying drawings shown in the embodiments. FIG. 1 is a schematic perspective view showing a state in which an electric power steering device A of the present invention is connected to a steering mechanism B. In the electric power steering apparatus A, a steering shaft 2 having a steering wheel 1 mounted on an upper end thereof is rotatably held by a steering column 3, and two steering assisting motors 10 and 20 are provided on the steering column 3. The steering mechanism B is mounted by applying the rotational force of the motors 10 and 20 to the steering shaft 2.
Is to be transmitted to.

More specifically, the above two motors 1
Nos. 0 and 20 are arranged opposite to each other with the steering shaft 2 interposed therebetween, and the respective rotational forces are passed through the electromagnetic clutches 30 and 40, the worm gear 7, and the worm wheel 8 meshed with the worm gear 7. , And is configured to be simultaneously added to the steering shaft 2 (see FIG. 2). These two motors 10, 20 are
Each of them has a small output, and by driving two units at the same time, the steering assist force necessary for the electric power steering apparatus A for a normal vehicle can be secured.

A torsion bar is interposed in the middle of the steering shaft 2. When the steering wheel 1 is operated, the torsion bar is slightly twisted, and an input shaft and an output shaft 2a are connected to each other by the torsion bar. There is a relative displacement between the two. The output shaft 2a is connected to, for example, a rack and pinion type steering mechanism B via a universal joint B1, and the input shaft and the output shaft 2a are connected to each other.
And the relative displacement generated between the torque sensor 4 and the controller 5, based on the detection result.
The input current to the motors 10 and 20 is controlled so that the steering force is assisted according to the steering torque applied to the steering shaft 2.

Further, the two motors 10 and 20 are
In order to suppress the fluctuation of the rotational force transmitted to the steering mechanism B, they are provided with their phases shifted from each other. Figure 3
FIG. 4 is a schematic diagram for explaining the state in which the phases are shifted, and the stators 12, 22 and the rotors 13, 22 when the one motor 10 and the other motor 20 are assumed to be coaxially arranged. 23 shows the positional relationship of 23. As shown in the figure, each of the motors 10, 20 has a stator 12,
The positions of the rotors 22 in the circumferential direction coincide with each other, and the positions of the rotors 13 and 23 in the circumferential direction are displaced and fixed by a predetermined angle θ. That is, when the rotor 13 of the motor 10 is in the rotation position where the cogging torque of the motor 10 is maximum (see the solid line in the figure), the rotor 23 of the motor 20 is
The rotor 1 of the motor 10 is positioned so that the cogging torque of the motor 20 is at the minimum (see the broken line in the figure).
By fixing the motor 3 and the rotor 23 of the motor 20 to the respective motor shafts 14 and 24 in a state of being displaced by a predetermined angle θ, the phases of the motors 10 and 20 are displaced from each other.

As described above, in the electric power steering apparatus A, the two motors 10 and 20 are out of phase with each other. Therefore, the coggings of the motors 10 and 20 are canceled by each other, and the steering mechanism B is operated. It is possible to minimize the fluctuation of the rotational force to be transmitted. Therefore, it is possible to obtain the steering assist force necessary for the electric power steering apparatus A for an ordinary vehicle and to obtain a good steering feeling.

Further, since the rotational force of each of the motors 10 and 20 is individually transmitted to the worm wheel 8, as compared with the case where a single high output motor is used,
The load acting on the worm gear 7 and the worm wheel 8 can be reduced. Therefore, the durability of the worm gear 7 and the worm wheel 8 can be ensured.

As shown in FIG. 4, the motors 10 and 20 may have a structure in which the motor shafts are connected in series by splines in a state where the phases are shifted. In this case, the motors 10 and 20 are respectively connected. If the flanges 15 and 25 for connecting the two are formed on the housings 11 and 21, the number of motors can be easily increased or decreased according to the required output.

As shown in FIG. 5, each motor 10,
The motor shaft and the housing of 20 may be shared, and in this case, the magnetic shield S may be interposed between both motors. The electric power steering device of the present invention is
The present invention is not limited to the above-described embodiment, and various design changes such as shifting the relative positions of the stators 12 and 22 of the motors 10 and 20 to shift the mutual phase of the motors 10 and 20 are possible. Can be given. Further, by using two motors having different rated outputs, a large steering assist force is obtained by using both motors when the vehicle is stopped and at low speed, and at the time of high speed, the motor having the larger rated output and the clutch connected thereto May be turned off to reduce the influence of the inertial force of the motor on the steering feeling.

[0015]

As described above, according to the electric power steering apparatus of the present invention, a plurality of motors are used, the phases of the motors are mutually shifted, and fluctuations in the rotational force transmitted to the steering mechanism are suppressed. As a result, it is possible to obtain a large steering assist force and to obtain a unique steering feeling.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing a state in which an electric power steering device of the present invention is connected to a steering mechanism.

FIG. 2 is a sectional view of a main part.

FIG. 3 is a schematic diagram for explaining a phase difference.

FIG. 4 is a sectional view showing another embodiment.

FIG. 5 is a sectional view showing still another embodiment.

[Explanation of symbols]

 2 Steering shaft 10 Motor 20 Motor A Electric power steering device B Steering mechanism

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kinchi Tokumoto 3-5-8 Minamisenba, Chuo-ku, Osaka City Koyo Seiko Co., Ltd.

Claims (1)

[Claims] 1. An electric power steering apparatus for driving a motor based on a steering torque applied to a steering shaft and transmitting the rotational force of the motor to a steering mechanism to assist steering, comprising a plurality of the motors. An electric power steering device characterized in that the respective phases of the respective motors are mutually shifted in order to suppress fluctuations in the rotational force transmitted to the steering mechanism.