JP2949890B2 - Electric power steering - Google Patents

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 apparatus having an improved steering feeling in operating a steering handle.

[0002]

2. Description of the Related Art Conventionally, a manual torque applied by a driver to a steering wheel of an automobile is detected, and the output of an electric motor is controlled in accordance with the manual torque.
There is known an electric power steering device that controls an assist torque applied to a steering shaft or the like by an electric motor.

[0003]

The manual torque is detected by a torque sensor. The output value obtained from the torque sensor is input to the control device via an integration circuit having a fixed time constant. The integration circuit controls the generation of assist torque by the electric motor to improve the steering feeling when the steering wheel is turned. The way of turning the steering wheel varies depending on the situation at that time and is not fixed. Here, when the setting of the time constant of the integration circuit is shortened, when the steering wheel is turned slowly, the steering wheel is likely to be in an oscillation state. Conversely, if the setting of the time constant of the integration circuit is lengthened, when the steering wheel is turned quickly, a delay in following the assist torque occurs. Therefore, there is a problem that it is difficult to satisfy the steering feeling when the steering wheel is turned by the integration circuit having a fixed fixed time constant in all situations.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a steering feeling without turning on a steering wheel without causing an oscillation state or delay in following assist torque. The object of the present invention is to provide an electric power steering device capable of improving the power steering.

[0005]

According to a first aspect of the present invention, there is provided a torque sensor for detecting a manual torque applied to a steering shaft of an automobile.
A control method for an electric power steering apparatus comprising: a motor that generates an assist torque; and a control device that controls an output of the motor according to an output of the torque sensor.
To differentiate the output value of the torque sensor and calculate the differentiated value.
The time constant decreases as
The output value of the torque sensor is integrated based on the
The output of the motor is controlled by the value. Ma
A second aspect of the present invention is directed to a steering shuffle for an automobile.
Torque sensor that detects manual torque applied to the
An electric motor for generating assist torque;
A control device for controlling the output of the electric motor in accordance with the output of the sensor
In the electric power steering system consisting of
Output between the torque sensor and the
Force value to time constant determined from capacitor and resistance element
An integrating circuit that integrates more, and a resistance element in the integrating circuit.
Variable resistance value according to external signal connected in parallel
Variable resistance circuit and values related to manual torque fluctuation
Signal to the variable resistance circuit according to the time constant of the integration circuit.
And a time constant changing means for changing the time constant .

[0006]

According to the first aspect, the output value of the torque sensor is provided.
, And as this differentiated value increases,
Decrease the time constant and set the time constant based on the reduced time constant.
Integrates the output value of the torque sensor, and calculates the motor
Output is controlled so that assist torque is generated quickly.
You. Further, in the second aspect, the integrating circuit includes a torque sensor.
Connected between the sensor and the control unit.
When these output values are determined from the capacitor and the resistance element
It is integrated by a constant. The variable resistance circuit is added to the integration circuit.
Connected in parallel with the above resistor element in response to an external signal
Change the resistance value. Then, the time constant changing means
Variable resistance according to the value associated with the
Signal to the circuit, and the time constant of the integrating circuit changes.
It is. Thus, the manual torque fluctuation
Value, i.e. the steering wheel was turned early or late
Manual torque applied to the steering wheel
The time constant of the integration circuit is changed according to the raw situation.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to specific embodiments. FIG. 1 is a configuration diagram showing an electric power steering apparatus according to the present invention.

The steering handle 10 is fixed to a steering shaft 11, and a torque sensor 12 is provided on the steering shaft 11. Steering shaft 1
The manual torque applied to 1 is used to change the direction of the steered wheels 41 and 42 via the rack and pinion gear 13. As is well known, the torque sensor 12 detects a torque generated when the steering handle 10 is operated and the steering shaft 11 is twisted. The output signal from the torque sensor 12 is inputted to the integration circuit (CR circuit) 15 composed of a resistance element R ₁ and a capacitor C. Then, the analog signal from the integrating circuit 15 is output to the A / D converter 1
8 that is converted into a digital signal by the
It has been input to U20. Further, an analog signal which is an output signal from the torque sensor 12 is provided in addition to the above-described path,
A / D converter 19 directly without passing through the integrating circuit 15
Are input to the CPU 20 as digital signals.

Here, the resistance element R _{1 of the} integration circuit 15 is used.
In parallel, a variable resistance circuit comprising a series connected resistor elements R ₂ and FET are connected. The gate of this FET has a PWM (Pulse Width Modulat
ion) signal is input. This CPU2
0 is a ROM 2 storing a program and a map showing a relation between a duty ratio and a differential value of torque.
1. A RAM 22 for storing various data is connected. An output signal from the CPU 20 is input to a driver circuit 25 constituting a control device, and is output from the driver circuit 25 to a motor 31 having a built-in reduction gear. This electric motor 31
Is rotated, the assist torque is applied to the steered wheels 41 and 42 via the rack and pinion gear 32.

Next, the CP used in the apparatus of this embodiment is
Based on the flowchart of FIG. 2 showing the processing procedure of U20, a description will be given with reference to the map of FIG. In step 100, the output signal T from the torque sensor 12 is read via the A / D converter 19 as a value related to the fluctuation of the manual torque. Next, the process proceeds to step 102, where the output signal T read in step 100 is differentiated to calculate a differential value (dT / dt) of the torque. That is, the amount of change in torque per time is calculated. Then, the process proceeds to step 104, where the differential value (dT / dt) of the torque calculated in step 102 is input to the above-described map stored in the ROM 21 and searched for a duty ratio. Next, the process proceeds to step 106, where the PWM signal pulse-width modulated according to the duty ratio obtained in step 104 is input to the gate of the FET. Incidentally, the time constant changing means is achieved by the above steps 100 to 106.

As described above, when the FET is switched based on the PWM signal, the combined resistance value of the resistance element R ₁ and the resistance element R ₂ of the integration circuit 15 changes. That is, when the steering wheel 10 is turned early, the differential value (dT / dt) of the torque is large.
According to the map of FIG. 3, the duty ratio (α) has a large value. Then, the combined resistance value decreases, and the time constant of the integration circuit 15 decreases. In this case, the CPU 20
, A command value is quickly output to the driver circuit 25, and a current is supplied to the electric motor 31. Therefore, assist torque is quickly generated by the steering handle 10 so as to assist the manual torque applied to the steering shaft 11. That is, there is no delay in following the assist torque with respect to the manual torque.

When the steering wheel 10 is turned late, the differential value (dT / dt) of the torque is small, and the duty ratio (α) is small according to the map shown in FIG. Then, the combined resistance value increases, and the time constant of the integration circuit 15 increases. In this case, the CPU
A command value is slowly output from 20 to the driver circuit 25, and current is supplied to the electric motor 31. Therefore, assist torque is slowly generated by the steering handle 10 to assist the manual torque applied to the steering shaft 11. That is, the steering handle 10 does not enter the oscillation state. As described above, in the electric power steering apparatus according to the present invention, the steering feeling can be extremely improved regardless of how the steering wheel 10 is turned. In the above-described embodiment, the output signal T from the torque sensor 12 is used as a value related to the fluctuation of the manual torque.
Alternatively, a steering angle sensor may be provided to detect the steering angle of the steering wheel 10, and the above-mentioned time constant may be changed according to the steering angular velocity which is a differential value of the output signal. Also, a rotation speed sensor is provided to
May be detected, and the above-mentioned time constant may be changed according to the rotational acceleration which is a differential value of the output signal.

[0013]

According to the present invention, first, the output of the torque sensor
Differentiate the value, and as this differentiated value increases,
To reduce the time constant, and based on this reduced time constant,
The output value of the torque sensor is integrated, and the integrated value
Control the output of the machine. This reduces the assist torque
Generated early. Or, second, torque sensor and control
Connected to the device to control the output value from the torque sensor.
Integration by time constant determined from capacitor and resistor
Circuit and the resistance element in the integration circuit
Variable whose resistance value can be changed according to the external signal connected to
Resistor circuit and respond to values related to manual torque fluctuations.
Signal to the variable resistor circuit to change the time constant of the integration circuit.
Has a constant change unit time to be of the integral circuit in response to occurrence of manual torque applied to the steering wheel
Is changed . Thus, the electric power steering apparatus according to the present invention has an optimum torque because the assist torque is quickly generated when the steering wheel is quickly turned, and no oscillation is felt when the steering wheel is slowly turned. It has a steering feeling.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an electric power steering apparatus according to a specific embodiment of the present invention.

FIG. 2 is a flowchart showing a processing procedure of a CPU used in the apparatus of the embodiment.

FIG. 3 is a map showing a relationship between a duty ratio and a differential value of torque stored in a ROM according to the embodiment.

[Explanation of symbols]

10-Steering handle 11-Steering shaft
12-torque sensor 15-integration circuit (CR circuit) 20-CPU (control device) 21-ROM 25-driver circuit (control device) 31-motor

Claims (2)

(57) [Claims] An electric system comprising: a torque sensor for detecting a manual torque applied to a steering shaft of an automobile; an electric motor for generating an assist torque; and a control device for controlling an output of the electric motor in accordance with an output of the torque sensor. In the control method for the power steering device, the output value of the torque sensor is differentiated, and the time constant is reduced as the differentiated value increases.
Illusion, integrates the output value of the torque sensor based on the time constant
And, especially to control the output of the electric motor by this integrated value
A control method in an electric power steering device. (2) Ma on the steering shaft of a car
A torque sensor that detects the new torque and an assist
Motor that generates torque and the output of the torque sensor.
And a control device for controlling the output of the motor.
In pneumatic power steering, The torque sensor and the control
Output from the torque sensor
The value depends on the time constant determined from the capacitor and the resistance element.
An integration circuit that integrates Connected in parallel with the resistance element in the integration circuit
A variable resistance circuit whose resistance value can be varied according to an external signal; According to the value related to the fluctuation of the manual torque,
Giving a signal to a variable resistance circuit, and setting the time constant of the integration circuit to
Time constant changing means for changing Characterized by having
Electric power steering device.