JP2523123Y2 - Electric power steering device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to an electric power steering control device used for a reach type forklift.

(Prior Art) Conventionally, various electric power steering systems have been proposed in which steering torque of a steering system is detected by various sensors, and a control circuit generates an assist torque required for an electric motor based on the detected amount.

Above all, when the steering system is fully rotated, the electric power steering gearbox collides with the stopper and is damaged by the large assist torque output from the electric motor. For example, there is a proposal disclosed in Japanese Utility Model Application Laid-Open No. Sho 62-19477.

This proposal includes a control device that reduces the steering assist force when the steering wheel is rotated close to the rotation limit and the steering wheel is about to rotate toward the rotation end. A limit switch that detects the rotation end is provided. The polarity of the rotation end detection signal and the polarity of the torque signal output from the torque detector are detected by a comparator, and the amplification of the voltage output to the servo motor drive circuit is changed by AND output of both signals.

(Problem to be Solved by the Invention) The above-described conventional technology has a drawback that the control circuit becomes complicated and expensive.

SUMMARY OF THE INVENTION An object of the present invention is to provide a relatively simple and inexpensive electric power steering control device which eliminates such disadvantages.

(Means for Solving the Problems) The present invention has been made in view of the above problems, and a torque sensor for detecting the magnitude and polarity of a steering torque applied to a steering system; Rotating end detecting means for detecting that the steering has been performed near the rotating end, wherein the left or right rotating end detecting means detects that the steering system has been steered to near the left or right rotating end, and the steering torque When the polarity of the detection signal coincides with the direction detected by the rotation end detection signal, the assist torque to the steering system is reduced, the left or right rotation end detection signal is detected, and the steering torque detection signal is detected. When the polarity is different from the direction detected by the rotation end detection signal, a control device that generates an assist torque to a normal steering system An electric power steering apparatus comprising: a diode having an opposite polarity connected to the left or right rotation end detecting means.

(Embodiment) An embodiment of the present invention will be described below in detail with reference to the drawings.

A sensor 1 detects a steering torque applied to the steering system A and is applied to a non-inverting input terminal of an operational amplifier 2. The operational amplifier 2 detects that the output of the sensor 1 is +
If the value is, a constant voltage of + is output, and the output of the sensor 1 is-.
Output a constant voltage of-in the same way, so-called 1:
One amplification.

S1 and S2 are limit switches as rotating end detecting means, which are normally closed contacts. In this embodiment, S1 is the left rotating end, S2
Are used for detecting the right rotation end. Therefore, when the steering system A is steered to the right, for example, and the gear box 5 comes into contact with the limit switch S2, the contact is opened. Needless to say, the rotation end detecting means can be variously modified such as a proximity sensor in addition to the limit switch.

Diodes 3 and 4 are connected to the limit switches S1 and S2, respectively, and have their polarities connected in opposite directions.

Here, the operation of the present invention will be described. For convenience, as shown in FIG. 2, the polarity of the sensor output at the time of rightward steering of the steering system is negative (-), and the polarity of the sensor output at the time of leftward steering is positive. This is described below as (+).

Assuming that the steering system A is steered, for example, to the right around the point O in FIG. 3, the output voltage of the sensor 1 is negative, and the output voltage of the operational amplifier 2 is also negative (-). A normal assist torque is generated by a motor (not shown) from the circuit 6 through the limit switch S2 and the diode 3.

Further, when the steering system A is steered to the right, the limit switch S2 is opened, the voltage level is reduced from the power steering control command circuit 6 through the resistor R, and the assist torque generated by the motor is also reduced. Even if the box 5 collides with the stopper 7, the impact can be reduced.

If the steering system A is steered to the left in this state, the output voltage of the operational amplifier 2 becomes positive (+), and the output voltage of the operational amplifier 2 passes through the diode 4 and the limit switch S1 without passing through the resistor R and the normal voltage. Assist torque is generated by the electric motor. Therefore, when it is detected that the steering system A is steered near the right rotation end, and the polarity of the detection signal of the steering torque matches the direction detected by the rotation end detection signal (that is, the right steering of the steering system). If the right rotation end detection signal is detected and the polarity of the steering torque detection signal is different from the direction detected by the rotation end detection signal (i.e., Steering system left steering), an assist torque to the normal steering system can be generated.

The same applies to the case where the steering system A is steered to the left.

(Effect of the Invention) According to the present invention, the left or right rotation end detecting means detects that the steering system is steered to the vicinity of the left or right rotation end, and the polarity of the steering torque detection signal is the rotation end detection signal. If the direction matches the direction detected by, the assist torque to the steering system is reduced,
When the left or right rotation end detection signal is detected and the polarity of the steering torque detection signal is different from the direction detected by the rotation end detection signal, a control device that generates an assist torque to a normal steering system is provided. There is an effect that a simple configuration using two diodes can be provided at a low cost.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing the present invention, FIG. 2 is a graph showing the relationship between steering torque and sensor output, and FIG. 3 is a schematic diagram showing a steering system. 1 Sensor 2 Operational amplifier 3 4 Diode S1, S2 Limit switch R Resistance

Claims (1)

(57) [Scope of request for utility model registration] A torque sensor for detecting a magnitude and a polarity of a steering torque applied to a steering system; and a rotation end detecting means for detecting that the steering system is steered near a left or right rotation end. The left or right rotation end detecting means detects that the steering system is steered near the left or right rotation end, and the polarity of the steering torque detection signal matches the direction detected by the rotation end detection signal. When the assist torque to the steering system is reduced, the left or right rotation end detection signal is detected, and when the polarity of the steering torque detection signal is different from the direction detected by the rotation end detection signal, a normal operation is performed. An electric power steering system equipped with a control device for generating assist torque to the steering system of Electric power steering device formed by connecting a diode in which the polarity is reversed each rotation end detection means.