JPS61178262A - Electrically driven power steering device - Google Patents

Abstract

PURPOSE:To make it possible to enhance the rectilinear advancing performance of a vehicle and to enhance the stability thereof upon backward movement, by detecting the forward or rearward movement of a vehicle and an acceleration, and by supplying electrical current to a motor in accordance with the acceleration to provide recovery force for reducing the steering angle of wheels to zero. CONSTITUTION:The torque which is detected by a sensor 8 is delivered to a circuit 110 which selects an assist function in accordance with the steering angle, and which delivers a current instruction signal in accordance with the assist force. Meanwhile, a circuit 120 receives the degree of steering angle from a steering angle meter 7 and selects a recovery force function in accordance with the steering angle. A current instruction signal corresponding to the recovery force is delivered and added with an instruction value from a circuit 10 and is then delivered to a circuit 150. Further, a vehicle speed is delivered from a sensor 30 to circuits 130, 140 which deliver their outputs to the circuit 120. Then, the result of calculation of acceleration is delivered to the circuit 102 to increase the recovery force current in proportion to the acceleration. Then, the recovery force and operating force are added together to judge the rotational direction of the motor, and are delivered to choppers.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a power steering device for a vehicle, and particularly relates to an electric motor for power steering in a direction where the steering angle becomes zero when the steering wheel is released when driving straight forward or backward. The present invention relates to an electric power steering device which is suitable for maintaining straight running unless a steering force is constantly applied to the steering wheel.

[Background of the invention]

Generally, running performance is better if the wheels are always in the straight direction during forward straight acceleration. For this reason, in the case of a steering wheel equipped with a conventional power steering device, if the steering wheel is left free (hands off the steering wheel), the wheels do not have the force to automatically return to the straight direction when accelerating normally. The resulting steering wheel shake causes the vehicle to meander. For this reason, when accelerating straight ahead, the driver usually holds the steering wheel fixed to prevent the vehicle from meandering due to steering wheel shake or the like. The shaking of the steering wheel, which causes the vehicle to meander when driving straight, occurs because when the vehicle accelerates, the load is applied to the rear wheels, reducing the load on the front wheels.

Furthermore, when the vehicle is traveling backwards with the steering wheel free, the straight-line performance is extremely poor because the effect of the caster angle of the wheels is opposite to that when the vehicle is traveling straight.

For this reason, in recent years, it has been considered that hydraulic power steering devices should be provided with a restoring force to improve straight-line performance, as disclosed in Japanese Patent Laid-Open No. 4-90726. However, how to control the restoring force during forward acceleration, sudden acceleration, and normal driving to improve safety while driving and straight-line performance.
No consideration was given to whether or not it would be possible to do so.

[Purpose of the invention]

An object of the present invention is to provide an electric vehicle that can provide a restoring force that causes the wheels to become flat in the longitudinal direction of the vehicle body when accelerating and reversing the vehicle, thereby improving straight-line performance and stability when reversing. An object of the present invention is to provide a power steering device.

[Summary of the invention]

The present invention detects whether the vehicle is moving forward or backward, and also detects the amount of acceleration of the vehicle, and supplies current to the armature of the electric motor in accordance with the detected amount of acceleration, so as to reduce the steering angle of the wheels to zero. The idea is to improve the straight-line performance of the vehicle when accelerating and the stability when reversing by giving the vehicle a restoring force.

[Embodiments of the invention]

Examples of the present invention will be described below.

FIG. 1 shows an embodiment of the invention.

In the figure, an electric motor 2 is connected to a battery 1, and the electric motor 2 is configured to be able to rotate either left or right. There is an FET in the counterclockwise rotation armature of this electric motor 2.
3 drains are connected. Additionally, a freewheel diode 5 connected in the forward direction is connected to the drain of this FET3.
Batch 1, 1] is connected via Also, a battery 1 is connected to the source of this FET3,
A microcomputer 100 is connected to the gate. Further, a drain of an FET 4 is connected to the clockwise rotation armature of the electric motor 2, and a battery 1 is connected to the drain of the FET 4 via a freewheel diode 6 connected in the forward direction. The source of this FET 4 is connected to the battery 1, and the gate is connected to the microcomputer 100. The microcomputer 100 receives the output from the sensor 50 that outputs the engine speed, the steering angle from the steering angle meter 7 of the steering system 9, and the rotational torque (steering force) of the steering wheel from the torque sensor 9. It is composed of Further, a signal from a vehicle speed sensor is input to this microcomputer 100.

Further, the electric motor 2 is provided with a current detector 10 for detecting the current supplied to the armature, and the detected value from the current detector 0 is inputted to the microcomputer 100.

FIG. 2 shows a block diagram for explaining the operation of FIG. 1.

First, the torque (steering force) detected by the torque sensor 8 is input to the assist function determination circuit 110 of the microcomputer 100, where an assist function corresponding to the steering force is selected. This assist function is determined so that the steering force remains constant. The assist function determination circuit 110 outputs a current command corresponding to the assist force.

On the other hand, based on the amount of steering angle input from the steering angle meter 7, a restoring force function is selected in accordance with the steering angle in the restoring force function determination circuit 120, and a current command corresponding to the restoring force is output. This current command is added to the current command value output from the assist function determining circuit, and is manually input to a left/right determining circuit 150 that determines whether the rotation direction of the steering wheel is left or right.

The vehicle speed is detected from the vehicle speed sensor 30 that I received from the gear ratio determination circuit 13.
0 is input to the acceleration calculation circuit 140.

Further, the engine rotation speed is inputted to this gear ratio determination circuit 130 from an engine rotation sensor 50. The output from the gear ratio determination circuit 130 and the output from the acceleration calculation circuit 140 are input to the restoring force function determination circuit 120. In this way, the restoring force function outputs a value determined by the output from the steering angle sensor 7, the acceleration calculation result, and the gear ratio.

This gear ratio calculation is Gear ratio = N/V However, N: engine rotation speed ■：Vehicle speed determined by

Back gear is detected by this gear ratio calculation.

This reverse gear detection may be performed using a reverse switch.

In addition, the acceleration calculation for detecting the acceleration amount is as follows: acceleration amount =
Vn -Vn-s However, Vn is determined by the current vehicle speed Vn-+ and the vehicle speed a certain time ago. This acceleration calculation result is input to the restoring force function determination circuit 120, and the restoring force current is increased in proportion to the amount of acceleration with the characteristics shown in FIG. The characteristic map shown in FIG. 3 is stored in the restoring force function determination circuit 120. As shown by the dashed line in FIG. 3, by using a steering angle sensor capable of linearly detecting the steering angle, the steering angle can be linearly increased from zero to a constant value. However, in this embodiment, a switch that outputs an output when a certain steering angle is reached is used to detect the steering angle.

The restoring force and the operating force thus determined are added and the motor is rotated clockwise in the right/left determination circuit 150.
It is determined whether to rotate to the left and outputs to either the right chopper 180 or the left chopper 190. Further, the composite signal input to the right/left determination circuit 150 is input to the current command circuit, and the absolute value is output as a current command value. This current command value is compared with the detected current value output from the current detector 10, and the difference with the detected current value is determined by the chopper circuit 17.
Output to 0. In this chopper circuit 170, it is converted into a chopping signal and outputted to a right chopper circuit 180 and a left chopper circuit 190, and either the right chopper circuit 180 or the left chopper circuit 190 acts depending on the judgment signal from the right/left judgment circuit 150. , FET3 or FE
T4 is chopped.

These FETs 3 and 4 will be destroyed if the temperature becomes high. Therefore, the amount of current flowing through the FETs 3 and 4 has a limit as shown in FIG. This is the current limit value for the temperature of the FET. For this reason, the power circuit is configured to detect the temperature of the power circuit and supply a current corresponding to the temperature to the motor. That is, a temperature detector is provided in the power part of the electric power steering drive circuit, and the microcomputer 100 calculates the maximum current to be passed through the motor with respect to the temperature, and is controlled so that no more than the maximum current flows through the motor. This flowchart is shown in FIG.

Therefore, according to this embodiment, when the vehicle is traveling with the steering wheel free, the straight direction can always be maintained due to the restoring force.

Furthermore, according to this embodiment, it is possible to prevent meandering caused by pre-driving during driving.

Furthermore, according to this embodiment, the FET and the motor can be protected from destruction due to temperature rise.

〔Effect of the invention〕

As explained above, according to the present invention, the wheels have a restoring force that tends to be flat in the longitudinal direction of the vehicle body when accelerating and reversing the vehicle, thereby improving straight-line performance and stability when reversing. can be improved.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is an operational block diagram, Fig. 3 is a restoring force current characteristic diagram with respect to steering angle, Fig. 4 is a temperature characteristic diagram of current limit value, and Fig. 5 is a flowchart of current limitation based on temperature. 2... Electric motor, 3.4... FET, 7... Rudder angle sensor, 8... Torque sensor, 100... Microcomputer.

Claims (1)

[Claims] 1. In an electric power steering device that uses an electric motor to assist with the steering force that changes the steering angle of the wheels left and right in response to left and right rotation of the steering wheel, it detects whether the vehicle is moving forward or backward and also detects the amount of acceleration of the vehicle. An electric power steering device characterized in that a current is supplied to an armature of the electric motor in accordance with the detected acceleration amount to give the wheels a restoring force in the direction of zeroing the steering angle of the wheels.