JP2003137111A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device capable of carrying on steering assistance even when an anomaly occurs in a torque detecting part. SOLUTION: The electric power steering device is provided with three detection circuits 12a, 12b and 12c connected in parallel, and a CPU 14 working as a means of determining whether or not each of the three detection circuits 12a, 12b and 12c is normal and a means of selecting one detection circuit determined to be normal. Driving of a motor for steering assistance is controlled on the basis of a torque signal outputted from the selected detection circuit.

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 for driving and controlling a steering assisting motor based on steering torque detected by a torque sensor.

[0002]

2. Description of the Related Art An electric power steering device has been put into practical use as a power steering device for assisting a force for operating a steering wheel of an automobile. Such an electric power steering device is
The torque acting on the steering wheel is detected by the torque sensor,
The steering assisting motor provided in the steering mechanism is driven according to the detected torque.

FIG. 6 shows a schematic structure of a torque sensor 16 portion of an electric power steering system. Signal output unit 10
Includes a transmission circuit, a coil for torque detection, and the like, and outputs a detection signal according to the torque applied to the steered wheels. The output terminal of the signal output unit 10 is connected to the input terminals of the main detection circuit 12a and the sub detection circuit 12b.

Main detection circuit 12a and sub detection circuit 12b
Is a detection circuit (torque detection unit) having the same characteristics including a resistance and a differential amplifier circuit, detects torque based on the detection signal, and outputs a main torque signal and a sub torque signal according to the detected torque. . The output terminals of the main detection circuit 12a and the sub detection circuit 12b are connected to the input terminals of the CPU 14.

The CPU (motor control unit) 14 compares the main torque signal and the sub-torque signal, and if it is determined that there is no difference between them, the CPU (motor control unit) 14 determines a steering assist motor (not shown) based on the main torque signal. Drive control.

[0006]

By duplicating the detection circuit in this way, steering assist can be performed while monitoring the presence or absence of abnormality in the detection circuit. However, a difference occurs between the main torque signal and the sub torque signal, and the main detection circuit 12a
Alternatively, when it is determined that the sub detection circuit 12b has an abnormality,
It is difficult to specify which torque signal (detection circuit) is normal.

Therefore, when an abnormality in the detection circuit is detected, there is no guarantee that normal torque detection can be continued, so it is necessary to interrupt the steering assist. When the steering assist is interrupted in this way, there arises a problem that the driver needs to cope with a sudden change in the steering feeling.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an electric power steering apparatus capable of continuing steering assist even when an abnormality occurs in a detection circuit (torque detection section). To aim.

[0009]

An electric power steering apparatus according to a first aspect of the present invention includes a signal output section for outputting a detection signal corresponding to torque applied to steered wheels, and torque detection and detection based on the detection signal. In the electric power steering apparatus including a torque detection unit that outputs a torque signal according to the torque, and a motor control unit that drives and controls a motor for steering assist based on the torque signal, three torque detection units are provided. The motor further includes a normal torque determination unit that determines whether each of the three torque detection units is normal, and a selection unit that selects one of the torque detection units determined to be normal. The control unit is configured to drive-control the motor based on the torque signal output from the selected torque detection unit.

In such an electric power steering apparatus, the normal torque determination means determines whether each of the three torque detection sections is normal or abnormal, and the selection means determines any one of the torque detection sections. Select. Even when an abnormality occurs in the torque detection unit, the normal torque detection unit is selected by the determination unit and the selection unit, and the steering assist can be continued using the torque signal output from the selected torque detection unit. For example, the three torque detection units are connected in parallel to have a triple structure.

The electric power steering apparatus according to a second aspect of the present invention is the electric power steering apparatus according to the first aspect of the present invention, which is provided with means for obtaining a difference between two torque signal values of the three torque signals respectively output from the three torque detecting portions, and the means. And a torque difference within a predetermined range determining means for determining whether or not the difference is within a predetermined range,
The normal torque determination means is configured to determine that the two torque detection units that have respectively output the two torque signals for which the determined difference is within the predetermined range are normal.

In such an electric power steering apparatus, the difference between the two torque signal values is obtained by the means for obtaining the difference, and the torque difference predetermined range determining means is provided.
It is determined whether the obtained difference is within a predetermined range. The normal torque determination means determines that the two torque detection units that output two torque signals whose calculated difference is within a predetermined range are normal.

An electric power steering apparatus according to a third aspect of the present invention is the electric power steering apparatus according to the first or second aspect of the present invention, further comprising a storage section for storing the priority order of the three torque detecting sections, and the selecting means based on the priority order. It is characterized in that the torque detector is selected.

In such an electric power steering apparatus, the torque detection unit having the higher priority stored in the storage unit is selected from the torque detection units determined to be normal. For example, a higher priority can be assigned to the smaller terminal number of the input terminal of the motor control unit to which the torque signal is input.

An electric power steering apparatus according to a fourth aspect of the present invention is characterized in that, in any one of the first to third aspects of the present invention, it is provided with an informing means for informing that the torque detecting section is determined to be abnormal. .

In such an electric power steering apparatus, the notification means can notify the driver or the like of the occurrence of an abnormality in the torque detection unit. The electric power steering apparatus according to any one of the first to third aspects of the present invention is any one of the torque detection units.
Even when an abnormality occurs, the normal torque detection unit is used to continue the steering assist. However, the warning means can issue a warning to inform the driver of the abnormality and prompt an early repair.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below with reference to the drawings showing the embodiments thereof. FIG. 1 shows a torque sensor 16 of the electric power steering device according to the present invention.
The schematic structure of a part is shown. The output terminal of the signal output unit 10 is
It is connected to the input terminals of the three torque detection units (the first detection circuit 12a, the second detection circuit 12b, and the third detection circuit 12c). The output terminals of the first detection circuit 12a, the second detection circuit 12b, and the third detection circuit 12c are connected to the input terminals of the CPU (motor control unit) 14.

The signal output unit 10 and each detection circuit 12a, 1
An example of 2b and 12c is shown in FIG. Each detection circuit 12a,
Since 12b and 12c use the detection circuit having the same characteristics, FIG. 2 shows an example of the detection circuit 12a.

The signal output unit 10 includes a DC power source E, an oscillator circuit 20, a current amplifier circuit 21, and an inversion current amplifier circuit 22.
A sampling pulse generating circuit 23, a temperature compensating coil L1, and a torque detecting coil L2. First
Detection circuit 12a (second detection circuit 12b, third detection circuit 1
2c) includes resistors R1 and R2, a differential amplifier circuit 25, a sample hold circuit 27, and a voltage / current conversion circuit 29.

As shown in FIG. 2, the output terminal of the oscillation circuit 20 connected to the DC power source E has a current amplification circuit 21, an inverted current amplification circuit 22 and a sampling pulse generation circuit 23.
Connected to each input terminal of. A series circuit of a temperature compensation coil L1 and a torque detection coil L2 is interposed between the output terminal of the current amplification circuit 21 and the output terminal of the reversal current amplification circuit 22.

A series circuit of a resistor R1 and a resistor R2 is connected in parallel to a series circuit of the temperature compensation coil L1 and the torque detection coil L2, and a bridge circuit is formed by these two series circuits. The connection contact between the temperature compensation coil L1 and the torque detection coil L2 is connected to one input terminal of the differential amplifier circuit 25. The connection contact of the resistors R1 and R2 is connected to the other input terminal of the differential amplifier circuit 25.

The output terminal of the differential amplifier circuit 25 is connected to the input terminal of the sample hold circuit 27. The output terminal of the sampling pulse generation circuit 23 is connected to the sampling pulse input terminal of the sample hold circuit 27. The output terminal of the sample hold circuit 27 is connected to the input terminal of the voltage / current conversion circuit 29, and the voltage / current conversion circuit 29 outputs the first torque signal.

The connection contact between the temperature compensating coil L1 and the torque detecting coil L2, both ends of the series circuit of the temperature compensating coil L1 and the torque detecting coil L2, and the output terminal of the sampling pulse generating circuit 23 are connected to each other. Second detection circuit 12
b and the third detection circuit 12c, respectively.

The second detection circuit 12b and the third detection circuit 12
c has the same configuration as the first detection circuit 12a, and since the same signal is input, the second torque signal and the third torque signal that are output are normally the same signals as the first torque signal. Become.

The CPU 14 includes the detection circuits 12a and 12
It operates as a means for determining whether or not each of b and 12c is normal, and a means for selecting one of the detection circuits judged to be normal. The CPU includes the detection circuits 12a, 12b, 1
The normality / abnormality of each of the detection circuits 12a, 12b and 12c is determined based on the difference between the first, second and third torque signals output from 2c.

The CPU 14 includes the detection circuits 12a and 12
It operates as a means for obtaining the difference between the torque signal values output from b and 12c and a means for determining whether the obtained difference is within a predetermined range. When the difference between the two torque signal values is within the predetermined range, the detection circuits that output the two torque signals respectively determine that they are normal. The CPU 14 determines that the detection circuit that has output the torque signal in which both of the obtained two differences are out of the predetermined range is abnormal. The predetermined range is, for example, ± 5 of the torque signal value.
It can be a value of about%.

In the storage unit such as the register in the CPU 14,
The priority order of each detection circuit 12a, 12b, 12c is stored. The CPU 14 selects one detection circuit from the normal detection circuits based on the priority order. For example, the first detection circuit 12a (first torque signal) has the highest priority, and the third detection circuit 12c (third torque signal) has the lowest priority.

When all of the detection circuits 12a, 12b, 12c are normal, the CPU 14 determines that the first, second, and third torque signals are all the same, and the first torque signal with the highest priority is given. Is selected.

When an abnormality occurs in any one of the detection circuits 12a, 12b, 12c, the CPU 14 causes only two torque signals of the first, second and third torque signals to coincide with each other. The torque signal (detection circuit) having the higher priority is selected from the two torque signals determined to match.

As shown in FIG. 1, a warning device (notifying means) 18 is connected to the CPU 14. The warning device 18
It operates as a means for reporting an abnormality in the detection circuit. The warning device 18 includes a warning lamp, a warning buzzer, etc., and when an abnormality of the detection circuits 12a, 12b, 12c is detected, C
It is activated by the PU 14 and emits light or sounds.

Next, steering assistance using the electric power steering apparatus according to the present invention will be described. The oscillation circuit 20 of the torque sensor 16 outputs an AC voltage Va biased by the DC voltage Vd, as shown in FIG. The AC voltage Va is input to the current amplification circuit 21 and the reversal current amplification circuit 22, and the current amplification circuit 21 is shown in FIG.
As shown by the solid line in (b), the AC voltage Vb and the positive DC voltage Vd in phase with the output voltage of the oscillation circuit 20 are output. On the other hand, the inversion current amplifier circuit 22 changes the phase of the output voltage of the oscillation circuit 20 by 180 as shown by the broken line in FIG.
The shifted AC voltage Vc and positive DC voltage Vd are output.

Since a DC voltage Vd having the same potential is applied to both ends of the series circuit of the temperature compensating coil L1 and the torque detecting coil L2, the temperature compensating coil L1 and the torque detecting coil L2 are connected to the DC voltage Vd. No current flows. And
As shown in FIG. 3C, when the impedance of the torque detecting coil L2 is larger than the impedance of the temperature compensating coil L1, the AC voltage of the connection contact between the temperature compensating coil L1 and the torque detecting coil L2 is AC voltage Va
To AC voltage Vb having the same phase as that of AC voltage Va. On the contrary, when the voltage is small, AC voltage Va changes to AC voltage Vc having an opposite phase.

The DC voltage at the connection contact point between the resistor R1 and the resistor R2 is the DC voltage Vd as shown in FIG. 4A when the resistors R1 and R2 are equal. Then, the voltage at the connection contact between the temperature compensation coil L1 and the torque detection coil L2 and the voltage at the connection contact between the resistors R1 and R2 are input to the differential amplifier circuit 25, and as shown in FIG. The differentially amplified voltage is input to the sample hold circuit 27.

Here, the sampling pulse generating circuit 23
Applies a sampling pulse generated based on the AC voltage Va to the sample hold circuit 27. The sample hold circuit 27 samples and holds the AC voltage input from the differential amplifier circuit 25 at a timing corresponding to the sampling pulse, and outputs a voltage signal corresponding to the steering torque. For example, when the sampling timing is adjusted to the peak of the AC voltage Vb (valley of the AC voltage Vc), it is possible to output a voltage signal according to the magnitude of the impedance of the torque detection coil L2.

The voltage signal output from the sample and hold circuit 27 is input to the voltage / current conversion circuit 29, converted into a current signal, and given a predetermined offset value.
It is output as a torque signal. The output torque signal (first, second, third torque signal) is input to the CPU 14.

One of the first, second and third torque signals is selected by the CPU 14, and the drive control of the steering force assisting motor (not shown) is performed based on the selected torque signal. . An example of the procedure for selecting the torque signal is shown in FIG.

The CPU 14 determines the coincidence of the first torque signal and the second torque signal, the coincidence of the second torque signal and the third torque signal, and the coincidence of the third torque signal and the first torque signal. (S10).

It is determined that the first torque signal and the second torque signal match (Ts1≈Ts2), and the second torque signal and the third torque signal do not match (Ts2 ≠ T).
s3), if it is determined that the third torque signal and the first torque signal do not match (Ts3 ≠ Ts1) (S12: YE).
S), since the first detection circuit 12a and the second detection circuit 12b can be regarded as normal, the CPU 14 selects the first torque signal according to the priority order (S14). Where T
s1, Ts2, and Ts3 are the first, second, and third torque signal values, respectively. Since it can be considered that an abnormality has occurred in the third detection circuit 12c, the warning device 18 is activated by the CPU 14.

Similarly, Ts1 ≠ Ts2, Ts2≈Ts
3, when Ts3 ≠ Ts1 is determined (S16: YE
S), since the second detection circuit 12b and the third detection circuit 12c can be regarded as normal, the CPU 14 selects the second torque signal according to the priority order (S18). Since it can be considered that an abnormality has occurred in the first detection circuit 12a, the CPU 1
4 activates the alarm device 18.

Further, Ts1 ≠ Ts2, Ts2 ≠ Ts3,
When it is determined that Ts3≈Ts1 (S20: YES),
Since the first detection circuit 12a and the third detection circuit 12c can be regarded as normal, the CPU 14 determines the first detection circuit 12a according to the priority order.
A torque signal is selected (S22). Second detection circuit 12
Since it can be considered that abnormality has occurred in b, the warning device 18 is activated by the CPU 14.

The first, second and third torque signals are all the same (Ts1≈Ts2, Ts2≈Ts3, Ts3≈T).
When it is determined to be s1) (S24: YES), the first torque signal is selected according to the priority order (S26).

If none of the above conditions are satisfied (S12: NO and S16: NO and S20: NO and S24: NO), the torque signal is not selected. Since none of the above conditions is satisfied, the signal output unit 1
There is a possibility that an abnormality has occurred in 0 or the like, and it is possible to perform a steering assist stop process or the like.

[0043]

According to the electric power steering system of the first aspect of the present invention, even if an abnormality occurs in the torque detection unit, the normal torque detection unit can be used to continue the steering assist.

According to the electric power steering system of the second aspect of the present invention, it is possible to determine whether the torque detection unit is normal or abnormal based on the result of the determination whether the difference between the torque signals is within the predetermined range.

According to the electric power steering system of the third aspect of the present invention, any one of the normal torque detection units can be selected according to the priority order stored in the storage unit.

According to the electric power steering system of the fourth aspect of the invention, it is possible to notify the driver or the like of the occurrence of an abnormality in the torque detection unit.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a torque sensor portion of an electric power steering device according to the present invention.

2 is a diagram illustrating a signal output unit and a first detection circuit (second
It is a figure which shows an example of a detection circuit and a 3rd detection circuit.

FIG. 3A is a diagram showing an example of an output waveform of a transmission circuit, FIG. 3B is a diagram showing an example of an output waveform of a current amplification circuit and an inverted current amplification circuit, and FIG. It is a figure which shows an example of the output waveform of the connection contact of the coil for torque and the coil for torque detection.

FIG. 4A is a diagram showing an example of an output waveform of a connection contact of a first resistor and a second resistor, and FIG. 4B is a diagram showing an example of an output waveform of a differential amplifier circuit.

FIG. 5 is a diagram showing an example of a procedure for selecting a torque signal.

FIG. 6 is a diagram showing a schematic configuration of a torque sensor portion of a conventional electric power steering device.

[Explanation of symbols]

10 Signal Output Units 12a, 12b, 12c Detection Circuit (Torque Detection Unit) 14 CPU (Motor Control Unit, Normal Torque Judgment Means, Selection Means, Means for Obtaining Difference between Torque Signal Values, Torque Difference Predetermined Range Judgment Means)

Claims (4)

[Claims] 1. A signal output section for outputting a detection signal according to the torque applied to the steered wheels, and a torque detection section for detecting torque based on the detection signal and outputting a torque signal according to the detected torque. An electric power steering apparatus comprising: a motor control unit that drives and controls a motor for steering assistance based on the torque signal. The electric power steering device includes three torque detection units, and each of the three torque detection units is normal. A normal torque determination unit that determines whether or not there is a torque detection unit, and a selection unit that selects any one of the torque detection units determined to be normal, and the motor control unit outputs the torque output from the selected torque detection unit. An electric power steering apparatus, characterized in that the motor is driven and controlled based on a signal. 2. A means for obtaining a difference between two respective torque signal values of the three torque signals respectively outputted from the three torque detectors, and a torque for judging whether or not the obtained difference is within a predetermined range. A difference within a predetermined range determination unit, wherein the normal torque determination unit determines that the two torque detection units that output the two torque signals for which the determined difference is within the predetermined range are normal. The electric power steering apparatus according to claim 1, wherein the electric power steering apparatus is provided. 3. A storage unit for storing the priority order of the three torque detection sections, wherein the selection unit is configured to select the torque detection section based on the priority order. The electric power steering device according to 1 or 2. 4. The electric power steering apparatus according to claim 1, further comprising an informing unit for informing that the torque detection unit is determined to be not normal.