JPH04274969A - Abnormality in torque sensor detecting device for electric power steering - Google Patents

Abstract

PURPOSE:To detect deviation of a middle point due to abnormality of source voltage or ground potential. CONSTITUTION:This device is provided with a torque sensor 1 to detect steering torque of a handle and output voltage corresponding to the detected torque, and an abnormality judging means 2 to input the output signal of the torque sensor 1 and judge the abnormality. Further, it is constituted by containing a first rheostat 3A and a second rheostat 3B of same characteristic which outputs voltage rectilinearly changing corresponding to the value of steering torque in the torque sensor 1, both rheostats 3A, 3B are connected so as to output the maximum voltage in one side while outputting the minimum voltage in the other side, an abnormality judging means judges whether the output voltage of both rheostats 3A, 3B are mutually conformed or not, when both output voltage are conformed, the voltage is judged whether the voltage is conformed to regular middle point voltage or not, and when both are not conformed, the torque sensor output is judged to be abnormal.

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 torque sensor abnormality detection device for detecting an abnormality in the output of a torque sensor for detecting steering torque in an electric power steering system (hereinafter referred to as "electric power steering").

0002

[Background Art] Conventionally, in automobiles, motor current of an assist motor is increased/decreased or controlled on/off according to the steering torque and vehicle speed in order to reduce the amount of operation required when steering the steering wheel, and the rotation of the assist motor is controlled. A relatively large number of so-called vehicle speed-sensitive electric power steering systems, which provide power assist in the steering direction according to steering torque, have been developed and put into practical use.

FIG. 5 shows a vehicle equipped with a general vehicle speed-sensitive electric power steering system. In FIG. 4, power steering 60 is installed at the front of vehicle body 100. This power steering 60 includes a steering shaft 5 having a steering handle (steering wheel) 51 at one end.
2, a torque transmission shaft 53 connected to the other end of the steering shaft 52 via a universal joint (not shown), and the torque transmitted from the torque transmission shaft 53 steers the left and right front wheels 55A, 55B via tie rods 54. A steering gear part 70 is provided.

Of these, the steering shaft 52 is rotatably supported by a steering column 56, and a torsion bar (not shown) is provided at a portion of the steering shaft 52 inside the steering column 56. In addition, the steering handle 5 of the steering column 56
At the end opposite to 1, there is a torque sensor (steering sensor) 57 that detects the torsion angle of the torsion bar, that is, the steering wheel steering torque value, and outputs the corresponding voltage.
is provided. Further, a gear box 5 is provided near the connection portion between the steering shaft 52 and the torque transmission shaft 53.
An assist motor 58 is provided which rotationally drives the torque transmission shaft 53 with its rotational force via a speed reduction mechanism (not shown) installed in the steering wheel 9 and assists the steering force. Here, an electromagnetic clutch 61 is provided between the assist motor 58 and the deceleration mechanism section to connect or separate the two. The steering gear section 70 is a type of speed reduction mechanism that converts the rotational motion of the torque transmission shaft 53 into a reciprocating motion of the tie rod 54, and is composed of, for example, a rack and pinion mechanism. In this case, the number of teeth of the pinion is the same as that of the steering gear. ratio.

Furthermore, a controller 80 is provided that controls the motor current value of the assist motor 58 and the on/off state of the electromagnetic clutch 61. This controller 80 is
Vehicle speed sensor (speedometer) 65 and torque sensor 5
Based on the output signal of the assist motor 58, predetermined calculations (calculation of the steering wheel torque based on the torque sensor output, calculation of the assist force according to the speed, etc.) are performed to determine the magnitude and direction of the assist force of the assist motor 58, and the motor current is It is designed to control the value. In FIG. 5, reference numeral 90 indicates a battery as a power source.

With such a configuration, the electric power steering 6
0, as is clear from the steering torque-motor current control map in Figure 6, the motor current is increased to increase the assist force (auxiliary steering force) when driving at low speeds, which allows for light steering. As the vehicle speed increases, the motor current is reduced to gradually reduce the assist force.
Furthermore, at speeds above a certain level (medium/high speed range), the electromagnetic clutch 6
1 is turned off, the rotational force of the motor 58 is not transmitted to the torque transmission shaft 53, a manual steering state is established, and stable steering performance can be obtained.

By the way, in electric power steering, the torque detection section is an important part that can be called the heart. For this reason, a torque sensor is usually composed of two variable resistors (potentiometers) with the same characteristics: a main and a sub, which simultaneously and separately detect the steering torque, that is, the amount of twist of the torsion bar.
If these outputs deviate, it is determined that the potentiometer output is abnormal. Here, in the conventional torque sensor 57, the main variable resistor 57A and the sub variable resistor 57B are configured to have the same relationship with the power supply and ground (GND), as shown in FIG. Therefore, both the main variable resistor 57A and the sub variable resistor 57B always exhibited characteristics as shown in FIG. 8, and their output voltage values always matched. These variable resistors 57A, 57B
The output voltage is 2.5V, which is the neutral point potential (midpoint voltage)
When steering to the right, the vehicle changes in the direction of arrow A, and when steering to the left, the vehicle changes in the direction of arrow B.

[0008]

However, in the conventional torque sensor described above, as shown in FIG. Alternatively, although it is possible to detect an open or short circuit in the sensor, it is inconvenient that it is impossible to detect a shift in the midpoint due to a drop in the power supply voltage. That is, if the 5V power supply drops to 4V for some reason, the neutral point potential (midpoint voltage) will change from 2.5V to 2.0V accordingly. Therefore, the controller 80 uses this 2.0V
The motor current value corresponding to the current speed of the torque value corresponding to the output voltage of is determined according to the steering torque-motor current control characteristic map of FIG. 6, and the motor current value of the assist motor 58 is controlled. As a result, even though the steering wheel 51 is actually in the neutral position, the rotational force of the assist motor 58 causes the steering wheel 51 to move.
There was a risk that the vehicle would rotate to the left against the driver's will, causing an inconvenience.

[0009]

OBJECTS OF THE INVENTION It is an object of the present invention to provide a torque sensor abnormality detection device for electric power steering that can improve the disadvantages of the conventional example and detect a midpoint shift caused by an abnormality in the power supply voltage or ground potential. There is a particular thing.

0010

[Means for Solving the Problems] The present invention provides a torque sensor that detects the steering torque of a steering wheel and outputs a voltage corresponding to the detected torque, and a torque sensor that inputs the output signal of this torque sensor and determines whether it is abnormal or not. and a determination means. The torque sensor is configured to include a first variable resistor and a second variable resistor having the same characteristics that output a voltage that linearly changes in response to a steering torque value, and both variable resistors are connected so that when one outputs the maximum voltage, the other outputs the minimum voltage. Furthermore, the abnormality determination means has a first function of determining whether or not the output voltages of the two variable resistors match each other, and if the two output voltages match, the voltage is within the normal range. It has a second function of determining whether or not it matches the point voltage, and a third function of determining that the torque sensor output is abnormal if it does not match. This configuration attempts to achieve the above-mentioned purpose.

[0011]

[Operation] The torque sensor is configured to include a first variable resistor and a second variable resistor having the same characteristics, and when one of the variable resistors outputs the maximum voltage, the other outputs the minimum voltage. As a result, the output voltages of both variable resistors match only at the neutral point where their characteristic lines intersect. Then, the determination means determines that the torque sensor output is abnormal if the output voltages of both variable resistors match each other, and if the voltages differ from the normal midpoint voltage.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to FIGS. 1 to 3. Here, the same reference numerals are used for the same components as in FIG. 5 described above, and the explanation thereof will be simplified or omitted.

FIG. 1 shows the configuration of a torque sensor abnormality detection device according to an embodiment of the present invention. In the embodiment shown in FIG. 1, a torque sensor 1 detects a steering torque of a steering wheel 51 and outputs a voltage corresponding to the detected torque.
and a controller 2 as an abnormality determining means for inputting the output signal of the torque sensor 1 and determining an abnormality thereof.

Of these, the torque sensor 1 includes a first variable resistor 3A and a second variable resistor 3B having the same characteristics and outputting a voltage that varies linearly in accordance with the steering torque value. Both variable resistors 3A and 3B are connected so that when one outputs the maximum voltage, the other outputs the minimum voltage. Therefore, these variable resistors 3A, 3
There is a relationship between the output voltages V1 and V2 of B as shown by the solid line in FIG. As is clear from this figure, the two outputs of the torque sensor 1, namely the first variable resistor 3A
main output V1 which is the output of
The sub-output V2, which is the output of It looks like this. now,
Even if the power supply voltage drops for some reason and becomes, for example, 4V as shown by the dotted line in Figure 2, both output voltages V1 and V2 will still match only at the neutral point, and at this time, the main Both the output and the sub-output show a midpoint voltage of 2V with a reduced power supply voltage of 4V.

The controller 2 is an electric power steering controller, and this controller 2 includes a microcomputer, and its internal memory stores a torque sensor abnormality determination program, which will be described later, as well as an assist motor motor control program. Various control programs such as current values, and various control data are stored. As shown in FIG. 3, this controller 2 is configured to receive the output of a vehicle speed sensor 65 in addition to the output of the torque sensor 1. On the other hand, an assist motor 58 and an electromagnetic clutch 61 are connected to the output side of the controller 1. The structure of other parts such as the mechanical part of this electric power steering is the same as that of FIG. 5 described above.

Next, the torque sensor abnormality detection process of the controller 2 will be explained with reference to the flowchart shown in FIG.

First, at the start of control, the controller 2 reads the main output and sub output of the torque sensor 1 (step S101). Next, the controller 2 determines whether the main output and sub output match (
Step S102) [First function]. If these outputs match, it is determined whether the output voltage is 2.5V, which is the normal midpoint voltage (step S104) [second function]. Here, the output voltage is 2.
If the voltage is 5V, it is determined that there is no abnormality in the torque sensor 1, and the abnormality detection process is ended. On the other hand, if the output voltage is not 2.5V, the controller 2 determines that the torque sensor output is abnormal [third function], turns off the electromagnetic clutch 61, and turns off the assist motor 58.
The motor current value is set to zero (step S105), and the process is then terminated.

On the other hand, if the main output and sub-output do not match in step S102, the controller 2 determines that the sum of both outputs is the original maximum voltage of the torque sensor 1, 5V (in this case, the normal power supply voltage). ) (step S104). and,
If the sum of both outputs is 5V, it is determined that there is no abnormality in the torque sensor 1, and the abnormality detection process is ended. On the other hand, if the sum of both outputs is not 5V, the controller 2 determines that the torque sensor output is abnormal, turns off the electromagnetic clutch 61, and zeros the motor current value of the assist motor 58 (step S105). ), then end the process.

As explained above, according to this embodiment,
Even if the midpoint potential fluctuates due to an abnormal drop in the power supply voltage, the main output and sub output of the torque sensor 1 will match only at the neutral point, and the controller 2 will confirm that the output voltage at this neutral point is normal. If it does not match the midpoint voltage of
Determine torque sensor output abnormality. This makes it possible to detect midpoint deviations due to abnormalities in the power supply or GND, which have been difficult to detect in the past. In addition, an abnormality in the torque sensor output due to an abnormality in the power supply or GND can be detected even at a location other than the neutral point by the controller 2 determining whether the sum of the main output and sub output matches the maximum voltage of 5V. Ru. If the controller 2 determines that the torque sensor output is abnormal, the electromagnetic clutch is immediately turned off and the assist motor is stopped, causing the inconvenience that the steering wheel rotates by itself due to center point deviation. can be effectively prevented.

[0020]

Effects of the Invention Since the present invention is configured and functions as described above, according to this, when the output voltages of the first variable resistor and the second variable resistor constituting the torque sensor match, The first to third functions of the determination means determine that the torque sensor output is abnormal when the voltage is different from the normal midpoint voltage, and this causes an abnormality in the power supply or GND that has been difficult to detect in the past. By configuring the program to turn off the electromagnetic clutch, assist motor, or cut off the power supply to the power steering itself when this abnormality is detected, the center point shift can be detected. It is possible to provide an unprecedented and excellent electric power steering torque sensor abnormality detection device that can effectively prevent the inconvenience that the steering wheel rotates by itself due to point deviation.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a torque sensor abnormality detection device according to an embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between the main output and sub-output of the torque sensor in FIG. 1;

FIG. 3 is a block diagram showing the configuration of an electric power steering including the device shown in FIG. 1;

FIG. 4 is a flowchart showing a torque sensor abnormality detection processing program of the controller in FIG. 1;

FIG. 5 is a diagram for explaining a conventional general vehicle speed-sensitive electric power steering system.

FIG. 6 is a diagram showing a steering torque-motor current control map of the electric power steering shown in FIG. 5;

FIG. 7 is an explanatory diagram showing the configuration of a torque sensor used in a conventional electric power steering system.

8 is a diagram showing the output characteristics of the torque sensor shown in FIG. 7. FIG.

[Explanation of symbols]

1 Torque sensor 2 Controller 3A as abnormality determination means
First variable resistor 3B Second variable resistor 51 Steering handle

Claims (1)

[Claims] 1. A torque sensor that detects a steering torque of a steering wheel and outputs a voltage corresponding to the detected torque, and an abnormality determining means that inputs an output signal of the torque sensor and determines whether the torque is abnormal. The sensor includes a first variable resistor and a second variable resistor having the same characteristics that output a voltage that changes linearly in response to the steering torque value, and both of the variable resistors have one a first function in which the variable resistor is connected so that when the variable resistor outputs the maximum voltage, the other outputs the minimum voltage, and the abnormality determining means determines whether the output voltages of both the variable resistors match each other;
a second function that determines whether or not the voltage matches a regular midpoint voltage when the two output voltages match;
A torque sensor abnormality detection device for electric power steering, characterized in that it has a third function of determining that the torque sensor output is abnormal when they do not match.