JPH02102872A - Control device for vehicle power steering system - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for a power steering device for automobiles and the like.

[Conventional technology]

A power steering system that aims to reduce steering force in an automobile includes a hydraulic pump driven by an engine, a control valve that controls the flow of oil discharged by the hydraulic pump, and a control valve that applies oil pressure in the steering direction during steering. It is usually constructed with a hydraulic cylinder device, etc. (for example, Utility Model Publication No. 53-4418
(See Publication No. 1).

[Problem to be solved by the invention]

If you try to add straight-line restoration control, etc. that automatically returns the steering wheel to the straight-ahead position when stopped, to the basic hydraulic power steering system that provides power assist according to the driver's steering force as described above, the hydraulic piping will be damaged. Modification work such as making changes or incorporating various actuators and control valves into the hydraulic power steering system itself is required, which is complicated and expensive.

Therefore, a control motor is connected to the steering shaft so as to be able to apply steering torque, and an electric straight-ahead restoring control device is provided, which is configured to use current from the motor to give the restoring torque to return the steering wheel to the straight-ahead position. is possible. In this case, when returning, the restoring torque is set to be large relative to the steering angle θ, etc., as shown in Figure 4, in order to promote the returning action, and when increasing the turning, the restoring torque is set to a large value so as not to impair the turning action. is set to be smaller as shown in the figure,
These torques are controlled by motor current.

By the way, when the restoring torque of the 2Fl type is set as described above, the restoring torque increases rapidly along with the motor current when changing from the cut mode to the return mode as shown in Fig. 5, and the handle is therefore returned strongly for a moment. . On the other hand, when changing from the return mode to the cut mode, the restoring torque increases and decreases along with the motor current, causing a sudden feeling of loss of power and a bad feeling.

Furthermore, when the steering wheel is held, the mode change described above is repeated in a short period of time based on the steering angle signal, and the motor current fluctuates rapidly, causing hunting, which causes vibration and noise in the steering wheel.

From this, in electric straight forward restoration control using a motor,
It is desired that improvements be made to reduce sudden mode changes and hunting when holding the steering wheel.

The present invention has been made in view of the above points, and its object is to provide a system in which a hydraulic power steering device is provided with an electric straight-line restoration control function, and restoration torque is set in 2FI classes to perform restoration control. An object of the present invention is to provide a control device for a power steering system for a vehicle that can smooth mode changes to improve the feeling and prevent hunting.

[Means to solve the problem]

In order to achieve the above object, the control device of the present invention attaches an electric straight forward restoring device using a motor to a steering shaft equipped with a hydraulic power steering device, and restores the cut mode and the return mode! - In a control system in which the torque is varied by the motor current of the control circuit, the motor current is controlled to be gradually increased or decreased at each change from the cut mode to the return mode and from the return mode to the cut mode.

[For production]

Based on the above configuration, when the vehicle is steered with the assistance of the hydraulic power steering device, restoring torque is further applied by the electric straight-line restoring control device at the time of increasing and returning the steering, making it easier to operate the steering wheel.

When changing between turning mode and return mode, the restoring torque is gradually increased/decreased along with the motor current to improve the feeling, and when the steering is held, the delay in the motor current suppresses fluctuations in the motor current and prevents hunting. It disappears.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

In FIG. 1, l is a steering wheel, 2 is a steering shaft, and 3 is a front wheel.The known front wheel steering system from the handle (2) to the front wheels 3 includes a control valve 4 that operates according to the steering torque of the steering wheel (1). A known hydraulic power steering device 7 is provided which includes a power cylinder 6 having left and right oil chambers into which hydraulic pressure discharged from a hydraulic pump 5 is introduced to either the left or right side by the operation of the control valve 4.

Reference numeral 8 denotes an electric straight forward restoring device, in which a steering control motor 9 with a speed reduction mechanism is attached to the steering shaft 2.
is attached. The above steering control motor 9
The steering torque of the steering wheel 1, that is, the power assist by the hydraulic power steering device 7, can be variably controlled by energizing the steering wheel 1.

The current flowing through the steering control motor 9 is at least a signal from a steering angle sensor lO that detects the steering angle of the steering shaft 2 during steering, and further a vehicle speed sensor l! that detects the vehicle speed. It is controlled by a control signal from a control circuit 15 based on a vehicle speed signal.

When the control circuit 5 is stopped, the control circuit 5 outputs a signal when the stationary steering torque Ts is greater than the stationary steering torque Ts required to turn the steering wheel 1 when the steering control motor 9 is not used, and the steering angle is greater than or equal to a predetermined steering angle in the direction of returning the steering wheel 1 to the straight direction. By supplying a return direction current to the steering control motor 9 so as to generate a constant value of return direction torque To, when the driver stops steering and takes his hands off the steering wheel i when the driver stops steering, the above return direction torque To is generated. The control valve 4 of the hydraulic power steering device 7 is operated in the return direction with a directional torque To,
Based on this, the surface pressure type power steering device 7 operates in the return direction and automatically returns the entire front wheel steering system to the vicinity of straight-ahead driving, making it easier to enter the garage when the vehicle is parked or stopped.

Furthermore, it is possible to prevent the inconvenience of the vehicle starting to move in an unexpected direction and steering in a hurry because the vehicle does not notice that the steering wheel 1 is still being steered when the vehicle starts the next time.

Next, in the case of a vehicle equipped with the vehicle speed sensor 11, the value of the return direction torque is gradually decreased as the vehicle speed increases according to the vehicle speed signal, and then increased again in the high speed range (for example, 100 + s/h or more). It becomes possible to arbitrarily give the characteristic that the vehicle tries to return to the straight direction when traveling.

In addition, the control circuit 15 calculates the steering angular velocity υ from the rate of change of the steering angle signal emitted from the steering angle sensor 10, and the rotation of the steering wheel is controlled to attenuate the return torque acting in the direction of returning the steering wheel 1 to the straight direction. By applying a motor control signal such that the torque in the opposite direction gradually increases as the steering angular velocity 6 increases, it is also possible to prevent vibrations in the vicinity of straight-ahead motion due to excessive return of the steering wheel 1.

This control signal can also be activated only when returning to straight travel.

Furthermore, the control circuit 15 calculates the lateral acceleration G from the vehicle speed signal emitted from the vehicle speed sensor 11 and the steering angle signal emitted from the steering angle sensor 10, and calculates the lateral acceleration G that acts to return the steering wheel l to the straight direction. By supplying the return direction current to the steering control motor 9 such that it increases as the acceleration G increases, this return direction current is added to the return direction current determined only by the steering angle θ. It is possible to increase the feeling of response to the steering direction and prevent the steering wheel l from becoming too light due to increased power assist.

In the above, if the return direction torque is set to be large in order to ensure that the handle l returns to the straight direction, the handle l
may become too extreme. Therefore, control circuit 1
5 is provided with a steering direction determining means, and when the steering wheel is held or when the steering wheel is turned further, a smaller return direction torque is applied than when the steering wheel is returned.

That is, the control circuit 15 controls the vehicle speed sensor 1 as shown in FIG.
The restoring torque calculating section 16 receives the vehicle speed V of 1 and the steering angle θ of the steering angle sensor 10 as input, and the restoring torques at the time of additional turning and at the time of returning are set with different characteristics as shown in FIG. Also, the steering angle θ is determined by the steering direction determination section! 7, the increase in steering angle θ determines whether to increase steering, the decrease in steering angle determines return, and the determination determines whether to hold the steering when stopped.
In step 6, the torque characteristics of the cut mode or return mode are manually output. The torque signal is input to the motor drive unit 19 via the current delay command unit 18, and the motor drive unit 19 controls the current of the steering control motor 9.

The current delay command unit 18 provides a time delay when switching between the cut mode and the return mode.1. It is designed to give commands to gradually increase or decrease.

Next, the operation of the control device having such a configuration will be described.

First, when steering by operating the steering wheel, the steering angle θ is manually determined by the steering direction determining unit 17, and if it is determined that the steering angle θ increases and the turning is to be increased, the restoring torque calculating unit 16 determines the low restoring torque characteristic. is selected. Based on this, the steering control motor 9 generates a restoring torque that is controlled at a low current, so that the steering operation can be performed without any problem.

When the steering wheel is returned from the above-mentioned turning mode, it is detected by the steering direction determination section 17, and the restoring torque calculation section 16
selects high restoring torque characteristics and moves to return mode. Then, at this time of change, the current delay command unit 18 corrects the motor current so that it gradually increases as shown in FIG. 3, and therefore the restoring torque also gradually increases. After shifting to the return mode, the large restoring torque quickly returns the steering wheel to the straight-ahead direction.

On the other hand, even when changing from the return mode to the cut mode, the current delay command unit 18 corrects the motor current and restoring torque so that they gradually decrease as shown in FIG. 3, so that no discomfort occurs. Furthermore, when the steering is held, the steering direction determining section 17 repeatedly detects the turning mode or the return mode in a short period of time based on an increase or decrease in the steering angle θ, but at each change in this case, a delay is caused by the current delay command section l8. Current changes are suppressed.

Therefore, the motor current is held substantially constant, and hunting does not occur.

Further, it can also be limited to cases where the steering angle is equal to or greater than a predetermined steering angle.

〔Effect of the invention〕

As described above, according to the present invention, when an electric straight-travel restoring device is attached to a power steering system and different restoring torques are applied when turning and returning, the restoring torque is gradually increased or decreased at each change. Improved feeling.

Furthermore, since the restoring torque is kept constant together with the motor current when the steering is held, hunting and associated vibrations can be prevented.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing an embodiment of the control device for a vehicle power steering system of the present invention, Fig. 2 is a block diagram of the electric control system, Fig. 3 is a motor current characteristic diagram when changing modes, and Fig. 4 Figure 5 is a characteristic diagram of restoring torque during return and additional turning, and Figure 5 is a characteristic diagram showing mode change states. 2... Steering shaft, 7... Hydraulic power steering device, 8... Electric straight forward restoring device, 9...
... Steering control motor, 15... Control circuit,
18...Current delay command section

Claims (1)

[Claims] A steering shaft equipped with a hydraulic power steering device is provided with an electric straight-travel restoring device using a motor, and the restoring torque in a cut mode and a return mode is controlled by changing the motor current of a control circuit. A control device for a power steering system for a vehicle, characterized in that the motor current is controlled to be gradually increased or decreased at each change from the cut mode to the return mode and from the return mode to the cut mode.