JPS6198671A - Controller for motor power steering system - Google Patents

Abstract

PURPOSE:To return the steering wheel accurately by arranging such that the added value will be the returning direction motor current command to produce an output torque from motor in returning direction. CONSTITUTION:A delay circuit 23 is provided in the output circuit of returning torque level indicating section 22 to produce slow rising characteristic of returning direction motor current command level itheta thus to reduce fluctuation of steering torque upon turning on of steering direction switch 21 and to improve the steering feeling. A control circuit 3 will decide the polarity of added signal of assist direction motor current command level (i) and returning direction motor current command level itheta in deciding section 31. While motor drive section 32 will drive a motor on the basis of a current command from an absolute level converting section 33. Armature current is compared with the current command from said converting section 33 to execute duty control through duty control section 34.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a control device for an electric power steering device for an automobile.

Conventional technology In order to reduce the number of turn/turn operations during steering by 4, a torque sensor is provided to detect the steering torque at the time of steering 1'E, and the steering torque detected by the torque sensor is An electric motor that converts it into an electric quantity, controls the output of an electric motor to suddenly change depending on the change in the electric quantity, and uses the electric motor to provide power assist in the steering direction according to the steering torque. Type power steering equipment has already been developed (for example, see Japanese Patent Publication No. 45-41246).

Problems to be Solved by the Invention The above-mentioned electric power steering device is designed to reduce the steering force in the steering direction due to the -pection of the electric motor during steering operation. When returning the steering wheel to straight-line reliability from the steered state, the inertia of the electric motor, the friction of the speed reducer, etc. act as resistance, making it difficult to return the steering wheel.

It is an object of the present invention to solve the problems of the electric power steering device as described above, and to improve the steering feeling and straight-line performance.

Means for Solving the Possible Problems The present invention provides an electric power steering device in which current to an electric motor is controlled in accordance with the torsional torque of a steering shaft, and power assist in the steering direction is provided by the single-movement motor. , an assist direction motor current instruction section that issues an assist direction motor current command value based on a torsional torque signal from a torsional torque sensor that detects the torsional torque of the steering shaft operates in accordance with the assist direction motor current command value and the steering angle. The return direction motor current command value is determined by the return direction motor current command value of the return direction motor current command value of the return direction motor current instruction section equipped with a delay circuit that makes the rise of the return direction motor current command value smooth. This feature is characterized in that the output torque of the electric motor is controlled via a control circuit based on the added value of .

Function In the above, as soon as the rudder starts to be turned during steering operation, the steering direction switch is activated and the return direction motor current command value is output from the return direction motor current instruction section, and the assist direction motor current is adjusted according to the torsional torque of the steering shaft. The electric motor performs power assist in the steering direction based on the sum of the assist direction motor current command value output from the command value and the return direction motor current command value, and after steering, the steering force is loosened and the torsional torque is maintained at a predetermined level. When the steering wheel is returned to a position below the value, the above-mentioned added value becomes the return direction motor 6-stroke 1 command value, and the electric motor generates an output torque in the return direction, so that the return of the handle is performed accurately.

In addition, the rise of the return direction motor current command value has a gentle characteristic that gradually reaches a predetermined value from zero due to the delay circuit, so the change in steering torque when the steering direction switch is activated is extremely small, improving the steering feeling. There are things that can be measured.

Example Embodiments of the present invention will be described below with reference to backbiting.

In FIG. 1, reference numeral 1 denotes an assist direction motor current indicating section, which includes a torsional torque sensor 11 that detects the torsional torque of the steering shaft and emits a torsional torque signal VT proportional to the torsional torque as shown in FIG. It consists of an output torque value indicating function section 12 which issues a motor current command value in the assist direction based on a function such as that shown in FIG.

Reference numeral 2 denotes a torsion direction motor current instruction section, and the return direction motor current instruction section 2 includes a steering direction switch 21 that detects whether steering is to the right or left during a steering operation; A return torque value indicating section 22 that issues a certain return direction motor current command value io in response to a rudder direction switch 210 ON signal, and a delay circuit 23 that makes the rise of the return direction motor current command value tθ a gentle curve. Then, the control circuit is activated by the addition signal (2) which is the addition of the assist direction motor current command value t of the assist direction motor current command section 1 and the return direction motor current command value (see FIG. 4) of the return direction motor current command section 2. 3 drives an electric motor 4 via a steering mechanism 5.
It is designed to provide power assist.

The control circuit 3 includes a positive/negative determining section 31 that determines whether the addition signal of the assist direction motor current command value - and the return direction motor current command value 2θ is positive or negative, and an absolute value l i of the addition signal.
The direction of the output torque of the electric motor is determined by the absolute value converter 33 which takes -1-iθ1 and the signal from the positive/negative distinguisher 31, and the electric motor 4 is driven by the current command of 1 m from the absolute value converter 33. The electric motor drive unit 32 compares the armature current of the electric motor detected by the armature current detection unit 35 with the current command value of the absolute value conversion unit 33, and determines the duty i.
and a duty control section 34 that performs ii control.

In the above, for example, if the assist direction motor current command value when steering to the right is set to a positive value as shown in Figure 6, the return direction motor current command value in this case becomes a negative value, The addition signal ■ is (L-if)), and the addition signal ■ ends up being a function as shown by the small line in FIG. 5, which is the indicator function shown in FIG. Is motor 4 controlled by this current value? You will be fried. When the steering is finished and the steering wheel is returned to its normal state, if the torsional torque No. 5 of the torsional torque sensor 11 becomes less than the predetermined value (less than A in Figure 5), the motor current command value ■
becomes a negative value and generates a motor output in the left-turn direction, that is, in the return direction. Furthermore, when the torsional torque becomes smaller than B in FIG. This return torque is applied to the plow near the point where the steering direction switch 21 turns off. Therefore, by setting the return direction output Lθ to cancel the force that acts as resistance in one direction such as the inertia force of the electric motor and the friction of the reducer when returning the steering wheel, the steering device can be naturally returns to a straight position near 1r7 due to its inherent caster effect, the steering direction switch 21 is turned off, and the return direction motor ``i''
li +J finger indicator up output is stopped and electric motor 4
The output stops.

As described above, it is possible to improve the steering wheel return function when steering the steering wheel, dynamic power steering system, and ring mounting system.
For example, in the case of a rack-binion type steering device, the steering direction switch 21 detects a sliding movement of the rack shaft to the left of the neutral position (toward the straight-ahead position) and turns on the steering direction switch 21.
Therefore, when the steering direction switch 210 is turned on and the return motor current command value tθ is strongly issued, the steering torque is suddenly increased at the beginning of turning the rudder. changes and the steering feeling worsens.

Therefore, in the present invention, the output circuit of the return torque value indicating section 22 is provided with a delay circuit 23 made of, for example, a known integrating circuit.
In the delay circuit 23, the rise of the return direction motor first-class command value Lθ is made to have a gentle characteristic as shown in FIG. Since the fluctuation is extremely small and the addition of the torque in the return direction gradually increases thereafter, the shocking strange feeling at the beginning of turning the rudder is greatly alleviated, and the steering feeling can be improved. When the steering is finished and the torsional torque becomes less than the predetermined value as mentioned above, tθ
Or, when the steering mechanism 5 is in a state where the electric motor 4 is applying a return force corresponding to a current value of approximately tθ, the steering mechanism 5 is in a clean state.
When the steering direction switch 21 is turned off, the return direction motor current command value -tθ gently returns to zero due to the delay circuit 23 as shown in the dotted bearing in Fig. 4, and accordingly, the function shown by the dotted line in Fig. 5 The current value indicated by is gradually moved in parallel as shown by the solid line, and the electric motor 4 stops when it is very close to the straight-ahead position.

Effects of the Invention As described above, according to the present invention, in a frost dynamic power steering device, it is possible to improve the return of the steering wheel, improve the release and convergence performance, and significantly improve the steering feeling. This, coupled with the fact that the structure is extremely simple and inexpensive, can bring about great practical effects.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a torsional torque signal characteristic diagram, Fig. 3 is an assist direction motor current command value characteristic diagram, and Mushroom i4 is a return direction motor current command value characteristic diagram. , Fig. 5 shows the characteristics of the added value of the assist direction motor current command value and the return direction motor current command value.
...Electric motor, 5...Steering mechanism. that's all

Claims (1)

[Claims] A torsional torque sensor that detects torsional torque of a steering shaft in an electric power steering device that controls current to an electric motor according to torsional torque of a steering shaft and provides power assist in a steering direction using the electric motor. The assist direction motor current command value of the assist direction motor current instruction section which issues the assist direction motor current command value based on the torsional torque signal of The return direction motor current command value is added to the return direction motor current command value of the return direction motor current instruction section equipped with a delay circuit that makes the rise of the return direction motor current command value smooth. A control device for an electric power steering device, characterized in that the control device controls the output of the electric power steering device.