JP2002022567A - Abnormality detector for torque sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simply structured abnormality detector for a torque sensor capable of surely detecting even an abnormality such as wire breakage of a harness. SOLUTION: The torque sensor 1 is equipped with a pair of coils with inductance changing in opposite directions to each other according to torque, a differential amplifying means for amplifying the difference between inputted sub- voltage of the two coils based on changes in their inductance and outputting it as a main voltage to a torque determination means 61 of a control device 50, an abnormality judging means 20a for judging whether an abnormality exists or not based on the two sub-voltage, and a switch means 49 turning off when the judging means 20a judges that an abnormality exists. This abnormality detector for the torque sensor is made by providing the control device 50 with a voltage impression means for impressing a prescribed voltage on the harness 73 via a pull-up resistor 65 with one switch terminal of the switch means 49 grounded and the other switch terminal thereof connected to one input terminal of the control device 50.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque sensor for detecting torque based on a change in inductance of a pair of coils and outputting a detection data signal to a control device, and more particularly to a device for detecting an abnormality of a torque sensor or the like.

[0002]

2. Description of the Related Art An example of a torque sensor having its own abnormality detecting means is disclosed in Japanese Patent Application Laid-Open No. 8-136366. The torque sensor of the same example has a pair of coils whose inductances change in opposite directions according to the torque, and a differential amplifier circuit that receives a pair of detection voltages induced by the pair of coils and differentially amplifies them. The output of the differential amplifier circuit is a torque detection signal, and the torque detection signal is output to the control circuit.

The torque sensor has an abnormality detection circuit for detecting an abnormality from a detection voltage induced in a pair of coils. When the abnormality detection circuit detects the abnormality, the output of the differential amplifier circuit is out of a steady output range. Is controlled to be a predetermined value. When the output of the differential amplifier circuit indicates such a predetermined value, the control circuit determines that there is an abnormality such as a coil connection failure.

However, when the abnormality detection circuit detects an abnormality, the output of the differential amplifier circuit is changed and the change is determined by the control circuit. In addition, the control circuit must judge a change in the output of the differential amplifier circuit, which is not reliable and causes a slight delay in the abnormality judgment.

[0005]

It is conceivable to output a detection signal directly to the control circuit through a dedicated harness when the abnormality detection circuit detects an abnormality. On the other hand, there is a case where the input becomes unstable on the side of the control circuit and the abnormality determination is erroneously made.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a torque sensor abnormality detecting device capable of reliably detecting an abnormality such as a disconnection of a harness with a simple configuration. Is to offer.

[0007]

In order to achieve the above object, the invention according to the first aspect of the present invention comprises a pair of coils whose inductances change in opposite directions according to a torque, Differential amplification means for inputting each sub-voltage based on each inductance change, amplifying the difference between the two sub-voltages, and outputting as a main voltage to the torque value determination means of the control device; Abnormality determining means for determining whether or not, the torque sensor includes a switch means that turns off when the abnormality determining means determines that there is an abnormality, grounding one switch terminal of the switch means,
The other switch terminal is connected to one input terminal of the control device via a harness, and voltage applying means for applying a predetermined voltage to the harness via a pull-up resistor detects abnormality of a torque sensor provided in the control device. The device.

When the abnormality judging means judges that there is no abnormality, the switch means is turned on and one of the harness and the control device is turned on.
When the input terminal is grounded and indicates 0 potential, and when it is determined that there is an abnormality, the switch means is turned off to turn off one of the harness and the control device
The input terminal is applied with a voltage via a pull-up resistor by a voltage applying means, and indicates a predetermined potential.

When an abnormality such as a disconnection occurs in the harness, the same as when the switch means is turned off, that is, one input terminal of the control device is connected to one input terminal of the control device via the pull-up resistor by the voltage application means. Indicates a predetermined potential applied. Therefore, even if there is an abnormality such as disconnection of the harness, it can be reliably detected.

According to a second aspect of the present invention, in the torque sensor abnormality detecting device according to the first aspect, the switch means is a transistor with a grounded emitter, and a collector terminal is connected to the harness as an output terminal. And

When the abnormality judging means judges that there is no abnormality, a voltage is applied to the base of the transistor, the transistor is turned on, one input terminal of the harness and the control device is grounded, and shows 0 potential. No voltage is applied to the base of the transistor, the transistor becomes non-conductive, and one input terminal of the harness and the control device is applied with a voltage via a pull-up resistor by a voltage applying means to indicate a predetermined potential. Using a simple transistor as the switch means, even if there is an abnormality such as disconnection of the harness, it can be reliably detected.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment according to the present invention will be described below with reference to FIGS. A torque sensor 1 according to the present embodiment is applied to a power steering device of a vehicle, and its schematic structure is shown in FIG.

An input shaft 3 and an output shaft 4 which are rotatably supported and coaxially inserted into the housing 2 via bearings 5 and 6 are connected to each other by a torsion bar 7 inside. A cylindrical core 8 is serrated and fitted on the outer peripheral surface of the large-diameter end 4 a of the output shaft 4 so as to be slidable only in the axial direction with respect to the output shaft 4. The pin 9 penetrates the elongated hole in the circumferential direction of the large-diameter end 4 a and engages with the spiral groove 8 a of the core 8.

Two coils 11 and 12 for torque detection supported inside the housing 2 are provided on the outer periphery of a cylindrical core 8 that slides in the axial direction via a gap. The two coils 11 and 12 are arranged on opposite sides of the center of movement of the core 8 in the axial direction.

When a torsional force acts on the input shaft 3, a rotational force is transmitted to the output shaft 4 via the torsion bar 7.
The torsion bar 7 is elastically deformed, and a relative displacement in the rotation direction occurs between the input shaft 3 and the output shaft 4. This relative displacement in the rotational direction causes the core 8 to slide in the axial direction through the engagement between the slider pin 9 and the spiral groove 8a.

When the core 8 moves in the axial direction, the coils 11,
The area surrounding each of the cores 12 changes so that one area increases and the other area decreases. As the area surrounding the core 8 increases, the magnetic loss increases and the inductance of the coil decreases. Conversely, as the area surrounding the core 8 decreases, the magnetic loss decreases and the inductance of the coil increases.

Therefore, when the torque for moving the core 8 toward the coil 11 acts, the inductance L of the coil 11
1 decreases, the inductance L2 of the coil 12 increases,
Conversely, when a torque for moving the core 8 toward the coil 12 acts, the inductance L1 of the coil 11 increases,
Twelve inductances L2 decrease.

The inductances L1, L2 of the coils 11, 12
Torque sensor 1 for detecting torque based on a change in L2
2 is shown in FIG. 2 as a schematic configuration diagram. The coils 11 and 12 are respectively composed of a resistor 13 (R1) and a resistor circuit 14 (R
2) is suspended at a positive voltage E via coils 11 and 12
Are connected to the oscillation output terminal osc of the control board 20a on which the CPU 20 is mounted.

The resistor circuit 14 has a configuration in which a resistor 15 is connected in parallel to a resistor 16 and a thermistor 17 which are connected in series, and performs a temperature compensation function by the action of the thermistor 17. That is, R1 / L1 = R always regardless of the temperature change.
The thermistor 17 has such a temperature characteristic as to exhibit a resistance value R2 satisfying 2 / L2.

A voltage signal line 21 extending from a connection between the coil 11 and the resistor 13 branches and is connected to rectification / smoothing circuits 23 and 25, respectively, and a voltage signal line extending from a connection between the coil 12 and the resistance circuit 14 is provided. The line 22 branches and the rectifying / smoothing circuits 24 and 26 respectively
It is connected to the.

That is, coils 11, 12, resistor 13, resistor circuit
14 constitutes a bridge circuit, an oscillating voltage is input to the bridge circuit, and the output voltage of the bridge circuit is
24, 25, and 26 are input.

The output voltage of the bridge circuit is rectified and smoothed by each of the rectifying / smoothing circuits 23, 24, 25, and 26 to obtain first, second, third, and fourth sub-voltages S1, S2, S3, and S4, respectively. Output to the buffer circuits 27, 28, 29, 30.

The output terminals of the buffer circuits 27 and 28 are connected to the inverting input terminal and the non-inverting input terminal of the differential amplifier 41 via resistors 31 and 32, respectively. Similarly, buffer circuit 2
Output terminals 9 and 30 are connected to an inverting input terminal and a non-inverting input terminal of the differential amplifier 42 via resistors 33 and 34, respectively.

The differential amplifiers 41 and 42 have resistors 35 and
Negative feedback is applied by 36 to function as a differential amplifier,
The output is input to the electronic control unit ECU 50 as a first main voltage M1 and a second main voltage M2.

The non-inverting input terminals of the differential amplifiers 41 and 42 are supplied with neutral point adjusting voltages V from neutral point voltage setting circuits 43 and 44 via buffer circuits 45 and 46 and resistors 37 and 38, respectively.
1, V2 are input.

The neutral point voltage setting circuits 43 and 44 receive the respective adjustment signals from the neutral point adjustment output terminals aj1 and aj2 of the control board 20a and receive the neutral point voltage V according to the adjustment signals.
1, V2 is set.

The differential amplifier 41 multiplies the difference between the first sub-voltage S1 and the second sub-voltage S2 by the amplification factor A, and outputs a voltage obtained by adding the neutral point adjustment voltage V1 as a bias voltage as the first main voltage M1. I do. That is, the first main voltage M1 is M1 = (S2−S1) · A + V1.

Similarly, also for the differential amplifier 42, the output second main voltage M2 is M2 = (S4-S3) .A '+ V2. Here, there is a relationship of V1 ≒ V2 and A ≒ A ′.

The neutral main voltage that is not biased to either the right steering torque (rightward torsional torque) or the left steering torque (leftward torsional torque) is referred to as a neutral point voltage. The adjustment voltages V1 and V2 become the neutral point voltages.

The ECU 50 outputs a motor control instruction signal to the motor driver 51 based on the first main voltage M1, and the motor driver 51 drives the motor 52 for assisting steering.

Then, the second main voltage M2 is used for detecting an abnormal state, and the ECU 50 determines that the difference between the first main voltage M1 and the second main voltage M2 is within a predetermined allowable range by abnormality determination means 63 described later. It is determined whether or not the torque sensor 1 is out of the allowable range, and it is determined that the torque sensor 1 is in some abnormal state.

The control board 20a has first, second, third and fourth sub-voltages S1, S2, S3, S4 and first and second sub-voltages.
When the main voltages M1 and M2 are input, the control board 20a controls the torque sensors 1 and 2 based on the third and fourth sub-voltages S3 and S4.
Judgment of abnormalities in the connection system, amplifier circuit, etc.
An abnormality determination signal is output from the abnormality output terminal fs to the abnormality-time switch circuit 49. The abnormality switch circuit 49 is directly connected to the ECU.
50, an abnormality determination signal is input from the abnormality output terminal fs, and if the signal is determined to be abnormal, the abnormality detection signal is set to EC.
Output to U50.

In addition, a neutral point adjustment signal AJS for instructing the neutral point adjustment is input to the neutral point adjustment terminal ajs from the neutral point adjustment switch AJS-SW47, and the neutral point voltage setting state is stored in the control board 20a. A rewritable E ² PROM 48 is connected to the neutral point voltage setting terminal rom.

The torque sensor 1 has a schematic circuit configuration as described above, and FIG. 3 shows a block diagram of the input / output of signals from the torque sensor 1 to the ECU 50 serving as a control device and a schematic configuration of the ECU 50.

The ECU 50 has torque value determining means 61 for determining the torque value from the first main voltage M1 and motor control means 62 for controlling the motor 52 based on the torque value determined by the torque value determining means 61. Then, the assisting force of the motor 52 according to the steering torque is applied to the steering by the motor control means 62 via the motor driver 51 to execute the power steering. Also, the ECU 50 controls the first main voltage M1
Abnormality judging means 63 for judging an abnormality from the second main voltage M2.

On the other hand, the abnormal-time switch circuit 49 in the torque sensor 1 is a transistor, whose emitter is grounded and whose base terminal is connected to the abnormal output terminal fs of the control board 20a.
And the open collector is the output terminal.

Between the torque sensor 1 and the ECU 50, a first
The harness 71 connects the terminal of the main voltage M1 and the input terminal of the torque value judging means 61 (and one input terminal of the abnormality judging means 63), and the terminal of the second main voltage M2 and one input terminal of the abnormality judging means 63 Are connected to a harness 73, and a collector terminal of the switch circuit 49 at the time of abnormality and one input terminal of the OR circuit 64 are connected to a harness 73.

Harness 73 connected to this collector terminal
Is pulled up to a positive potential via a pull-up resistor 65 on the ECU 50 side. The other input terminal of the OR circuit 64 is connected to the abnormality determining means 63, and an output signal is output to the motor control means 62.

Abnormal output terminal fs on control board 20a
The abnormality determination signal output to the base terminal of the transistor, which is the abnormality-time switch circuit 49, is a signal indicating whether or not voltage has been applied, and the CPU 20 of the control board 20a determines whether or not there is an abnormality, and determines that there is no abnormality. The voltage is applied to the base terminal, the transistor of the switch circuit 49 at the time of abnormality becomes conductive, and the output terminal of the collector becomes 0 volt (L
When it is determined that there is an abnormality, the application of the voltage to the base terminal is stopped, and the abnormality-time switch circuit 49 is turned off.
Transistors become non-conductive and pull-up resistor 65
The output terminal of the collector, to which a voltage is applied via, becomes a predetermined potential (referred to as H potential). The voltage signal at the output terminal of the collector is an abnormality detection signal and is input to one input terminal of the OR circuit 64.

The signal of the abnormality judging means 63 input to the other input terminal of the OR circuit 64 is a voltage signal indicating an L potential when it is judged to be normal and an H potential when judged to be abnormal. Therefore, the OR circuit 64 outputs the H potential to the motor control means 62 when at least one of the input terminals has the H potential.

Here, the abnormality determination method by the abnormality determination means 63 of the ECU 50 will be described with reference to the first, second, third, and fourth sub-voltages S.
1, S2, S3, S4 and first and second main voltages M1, M2
This will be described with reference to FIG. In the coordinates shown in FIG. 4, the vertical axis represents voltage, the right direction on the horizontal axis represents right steering torque, the left direction on the horizontal axis represents left steering torque, and the origin 0 is a neutral point.

FIG. 4 shows the case where the torque sensor 1 operates normally. When the right steering torque increases, the input shaft 3
The core 8 moves toward the coil 11 due to the relative rotation of the output shaft 4 and the output shaft 4, increasing the inductance L 2 of the coil 12 to increase the induced electromotive force.
Since the induced electromotive force is reduced by decreasing 1, the second and fourth sub-voltages S2 and S4 increase, and the first and third sub-voltages S1 and S3 decrease (see FIG. 4).

When the left steering torque increases, the second and fourth sub-voltages S2 and S4 decrease, contrary to the above.
The first and third sub-voltages S1 and S3 increase (FIG. 4,
reference). St indicates a neutral point voltage of the third and fourth sub-voltages S3 and S4.

Accordingly, the first and second outputs of the differential amplifiers 41 and 42 obtained by multiplying the difference between the two by A (A ') and adding the neutral point voltage thereto.
As shown in FIG. 4, the second main voltages M1 and M2 are inclined lines that rise rightward and pass through V1 and V2 at the neutral point.

The ECU 50 calculates the first and second main voltages M1,
M2 is compared to determine whether the difference between the two is within an allowable range. If it is normal, the changes of the first and second main voltages M1 and M2 are substantially coincident as shown in FIG. If the changes in the first and second main voltages M1 and M2 are different and the difference between the two exceeds an allowable range, it is determined that there is an abnormality.

On the other hand, the control board 20a separately includes means for detecting an abnormality in the torque sensor 1, the connection system, the amplifier circuit and the like based on the third and fourth sub-voltages S3 and S4. The memory of the control board 20a stores a coordinate map of XY coordinates shown in FIG.

The same coordinate map shows the ideal relation characteristics of the third and fourth sub-voltages S3 and S4 in the normal state on the XY coordinates where the X-axis is set to the third sub-voltage S3 and the Y-axis is set to the fourth sub-voltage S4. The curve L is obtained in advance, and the upper limit curve Lu and the lower limit curve Ld are set substantially symmetrically with respect to the ideal relation characteristic curve L.

Since the third and fourth sub-voltages S3 and S4 move symmetrically, the ideal relation characteristic curve L in FIG. Upper limit curve Lu and lower limit curve L set above and below L
The width of d is set so narrow that erroneous detection does not occur.

As shown in FIG. 5, the widths of the upper limit curve Lu and the lower limit curve Ld are partially changed, and the widths are set to be large in accordance with the increase in the left and right steering torque, and thus the width of the left and right steering neutral is small. The detection accuracy in the region (near torque 0), that is, the straight traveling region of the vehicle is increased.

The CPU 20 of the control board 20a has a control program for detecting an abnormality using the coordinate map. FIG. 6 is a flowchart showing a control procedure of the control program.

First, in step 1, the third and fourth sub-voltage values S
3 and S4, and the upper limit curve L corresponding to the third sub-voltage value S3 read in the next step 2 according to the coordinate map.
u and an upper limit fourth sub-voltage value S4u and a lower limit fourth sub-voltage value S4d indicated by the lower limit curve Ld (see FIG. 7).

In the next step 3, it is determined whether or not the fourth sub-voltage value S4 read in step 1 is between the upper limit fourth sub-voltage value S4u and the lower limit fourth sub-voltage value S4d. If so, proceed to step 4 and it is determined that there is no abnormality. If a voltage is applied to the transistor of the switch circuit 49 at the time of abnormality and the voltage is not between the upper limit fourth sub-voltage value S4u and the lower limit fourth sub-voltage value S4d, go to step 5. Then, it is determined that there is an abnormality, and no voltage is applied to the transistor.

If no voltage is applied to the transistor of the abnormal-time switch circuit 49, the transistor of the abnormal-time switch circuit 49 is turned off, the output terminal of the collector becomes H potential, and the output of the OR circuit 64 in the ECU 50 becomes H. The motor control means 62 receives this signal and stops the control of the motor 52.

As described above, the third and fourth states in a normal state are determined in advance.
An ideal relation characteristic curve L of the sub-voltages S3 and S4 is obtained in advance,
A coordinate map in which an upper limit curve Lu and a lower limit curve Ld are set based on the ideal relationship characteristic curve L is stored, and points on the coordinate map indicated by the actually detected third and fourth sub-voltage values S3 and S4 are stored. Is between the upper limit curve Lu and the lower limit curve Ld.

Therefore, the magnitude of the torque is irrelevant for detecting the abnormality, and therefore, the abnormality can be detected with high accuracy in the entire region of the torque. By setting the widths of the upper limit curve Lu and the lower limit curve Ld so narrow that erroneous detection does not occur, the accuracy of abnormality detection can be further improved. In addition, the width of the upper curve Lu and the lower curve Ld may be partially changed to particularly improve the detection accuracy near the required torque.

In addition to the above-described method, the abnormality determination method for the control board 20a is determined by defining the third and fourth sub-voltages S3 and S4 or the sum S3 + S4 of the two voltages as an allowable range between the upper limit voltage and the lower limit voltage. It should be noted that an abnormality may be determined when any of the voltages exceeds the allowable range.

When an abnormality is detected by the CPU 20 of the control board 20a, an abnormality detection signal is directly transmitted from the abnormality-time switch circuit 49 to the ECU 50 via the dedicated harness 73 (when the input terminal of the ECU 50 is Therefore, the ECU 50 can quickly and surely input the abnormality signal and quickly stop the motor control to respond.

Further, in addition to the abnormality judgment of the two main voltages by the abnormality judgment means 63 of the ECU 50, the CPU 20 of the control board 20a, which is the self-diagnosis means of the torque sensor 1, judges the abnormality of the sub-voltage. Is executed reliably.

Even when an abnormality such as a disconnection occurs in the harness 73, the pull-up resistor on the ECU 50 side is used in the same manner as when the transistor of the switch circuit 49 becomes nonconductive at the time of abnormality.
Since a voltage is applied to the input terminal of the ECU 50 via 65 and the potential becomes H potential, it can be determined that an abnormality has occurred. As described above, a simple transistor is used as the switch circuit 49 at the time of abnormality, and even if there is an abnormality such as a break in the harness, it can be reliably detected.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a mechanical part of a torque sensor according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of an electric circuit portion of the torque sensor.

FIG. 3 shows input / output of signals from a torque sensor to an ECU and E.
FIG. 3 is a block diagram illustrating a schematic configuration of a CU.

FIG. 4 is a diagram illustrating states of first, second, third, and fourth sub-voltages and first and second main voltages in a normal state.

FIG. 5 is a diagram showing a coordinate map for third and fourth sub-voltages.

FIG. 6 is a flowchart showing a control procedure for performing abnormality detection by a control board.

FIG. 7 is a diagram showing how to use the coordinate map.

[Explanation of symbols]

1. Torque sensor 2. Housing 3. Input shaft 4.
Output shaft, 5, 6 ... bearing, 7 ... torsion bar, 8
... Core, 9 ... Slider pin, 11,12 ... Coil, 13 ... Resistance, 14 ... Resistance circuit, 15,16 ... Resistance, 17 ... Thermistor, 20
... CPU, 20a ... control board, 21, 22 ... voltage signal line, 2
3, 24, 25, 26 ... rectifying / smoothing circuit, 27, 28, 29, 30 ... buffer circuit, 31, 32, 33, 34, 35, 36, 37, 38 ... resistor,
41, 42 ... differential amplifier, 43, 44 ... neutral point voltage setting circuit, 4
5, 46: buffer circuit, 47: neutral point adjustment switch AJS
-SW, 48: E ² PROM, 49: Switch circuit at abnormal time, 5
0 ... ECU, 51 ... Motor driver, 52 ... Motor, 61 ... Torque value determination means, 62 ... Motor control means, 63 ... Abnormality determination means, 64 ... OR circuit, 65 ... Pull-up resistance, 71, 72, 73 ...
Harness.

Claims (2)

[Claims] 1. A pair of coils whose inductances change in opposite directions according to a torque, and respective sub-voltages based on the respective inductance changes of the two coils are input to amplify a difference between the two sub-voltages to amplify a main voltage. Differential amplification means for outputting to the torque value judgment means of the control device, abnormality judgment means for judging whether or not there is an abnormality based on the two sub-voltages, and a switch which is turned off when the abnormality judgment means judges an abnormality Means, a torque sensor is provided, one switch terminal of the switch means is grounded, the other switch terminal is connected to one input terminal of the control device via a harness, and a predetermined value is connected to the harness via a pull-up resistor. An abnormality detecting device for a torque sensor, wherein voltage applying means for applying a voltage is provided in the control device. 2. The torque sensor abnormality detecting device according to claim 1, wherein said switch means is a transistor having a common emitter, and a collector terminal is connected to said harness as an output terminal.