JP2000121461A - Torque sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a torque sensor which can sense contact failures even if a torque detection coil and a temperature compensation coil are singlet systems, respectively. SOLUTION: Torque is detected based on a change in impedance occurring on a coil 12 according to torque to be detected. The torque sensor includes means 11, 21 for making constant current flow to coils 12, 22; AC detection means 13, 15, 23, 25 for detecting alternate current contained in output voltage of the coils 12, 22; DC detection means 17, 27 for detecting direct current contained in output voltage of the coils 12, 22; and means 18, 28, 35, 38 for detecting abnormality based on the direct current detected by the DC detection means 17, 27.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque sensor, and more particularly to an improvement in a torque sensor suitable for a power steering device of an automobile.

[0002]

2. Description of the Related Art FIG. 7 is a block diagram showing a configuration example of a conventional torque sensor. In this torque sensor, an alternating current output from the oscillation circuit 10 is supplied to a current amplification circuit 41 and an inverted current amplification circuit 42, and are amplified and invertedly amplified, respectively. The series circuit of the coil 43 and the coil 44 for temperature compensation whose impedance changes according to the applied torque, the series circuit of the resistors 45 and 46, and the two ends of the parallel circuit of the series circuit of the resistors 47 and 48, Currents amplified and inverted by the current amplifier 41 and the inverted current amplifier 42, respectively, are supplied.

The voltage at the connection point between the coils 43 and 44 and the voltage at the connection point between the resistors 45 and 46 are supplied to a differential amplifier circuit 49, and the difference between them is amplified. Coil 43
And the voltage at the connection point of the coil 44, the resistance 47 and the resistance 4
The voltage at the connection point 8 is supplied to the inverting differential amplifier circuit 53, and the difference is inverted and amplified. Coil 43 and coil 4
The voltage at the connection point of No. 4 is also applied to the sampling pulse creation circuits 50 and 54, which create and output sampling pulses based on the applied voltages.

The differential voltage amplified by the differential amplifier circuit 49 is sampled by a sampling pulse output from a sampling pulse generating circuit 50 in a sample and hold circuit 51, and is output as a detected torque value via a buffer 52. The difference voltage inverted and amplified by the inverted differential amplifier circuit 53 is sampled by the sampling pulse output from the sampling pulse generation circuit 54 in the sample and hold circuit 55, and is output as a detected torque value via the buffer 56.

[0005] In the torque sensor having such a configuration, the alternating current output from the oscillation circuit 10 is supplied to the current amplifier circuit 41 and the inverted current amplifier circuit 42 to be amplified and inverted respectively. The amplified and inverted amplified AC current is supplied to both ends of a parallel circuit of a series circuit of a coil 43 and a coil 44 for temperature compensation, a series circuit of a resistor 45 and a resistor 46, and a series circuit of a resistor 47 and a resistor 48. Given.

The voltage at the connection point between the coil 43 and the coil 44 and the voltage at the connection point between the resistor 45 and the resistor 46 are supplied to a differential amplifier circuit 49. Amplify the temperature compensated voltage difference.
The voltage at the connection point between the coils 43 and 44 and the resistance 47
And the voltage at the connection point of the resistor 48 and the inverted differential amplifier 53
The inverting differential amplifier circuit 53 inverts and amplifies the temperature compensated voltage difference according to the applied torque.

The differential voltage amplified by the differential amplifier circuit 49 is sampled by a sample and hold circuit 51 and output as a detected main torque value via a buffer 52. The differential voltage inverted and amplified by the inverting differential amplifier circuit 53 is sampled by the sample and hold circuit 55, and is output as a detected sub torque value via the buffer 56.

FIG. 8 is a block diagram showing another example of the configuration of a conventional torque sensor. This torque sensor includes a series circuit of a compensation coil 61 for temperature compensation and a detection coil 62 whose impedance changes in accordance with the applied torque, a resistor 63, a variable resistor 64 and a resistor 65. , A resistor 66, a variable resistor 6
7 and the resistor 68 are provided at both ends of a parallel circuit with the series circuit.

The voltage at the connection point between the compensation coil 61 and the detection coil 62 and the voltage at the variable terminal of the variable resistor 64 are supplied to a main-side differential output circuit 69, and the difference between them is detected. Output to terminal TMAIN. The voltage at the connection point between the compensation coil 61 and the detection coil 62 and the variable terminal voltage of the variable resistor 67 are supplied to the sub-side differential output circuit 70, and the difference is detected, and the difference is detected by the sub-terminal TSUB of the torque sensor connector TCN. Is output.

On the other hand, the power supply voltage Vcc of +8 V applied through the power supply terminal TV of the connector TCN is used as a drive voltage as the oscillation circuit 60, the reference power supply circuit 71, the main-side differential output circuit 69, and the sub-side differential output circuit 70. Has been given to. The reference power supply circuit 71 generates two predetermined reference voltages, one of which is provided as a reference voltage for determining the oscillation frequency of the oscillation circuit 60 and the offset voltage of the non-inverting input terminal of the main-side differential output circuit 69. The other one is given as an offset voltage of the non-inverting input terminal of the sub-side differential output circuit 70.

In the torque sensor having such a configuration, when the power supply voltage Vcc is applied to the power supply terminal TV, the oscillation circuit 60
Oscillates, and the reference power supply circuit 71 outputs two reference voltages. The oscillation voltage of the oscillation circuit 60 is a parallel circuit of a series circuit of the compensation coil 61 and the detection coil 62, a series circuit of the resistor 63, the variable resistor 64 and the resistor 65, and a series circuit of the resistor 66, the variable resistor 67 and the resistor 68. Given to both ends.

The voltage at the connection point between the compensation coil 61 and the detection coil 62 and the voltage at the variable terminal of the variable resistor 64 are given to the main differential output circuit 69, and the main differential output circuit 69 And a temperature compensated voltage difference is detected, an offset voltage is added to the detected voltage difference, and the main terminal TMAI is output as a main torque signal.
Output to N. The voltage at the connection point between the compensation coil 61 and the detection coil 62 and the voltage at the variable terminal of the variable resistor 67 are provided to the sub differential output circuit 70,
0 detects a voltage difference corresponding to the applied torque and temperature compensated, adds an offset voltage to the detected voltage difference, and outputs it to the sub-terminal TSUB as a sub-torque signal.

The offset voltage is provided so that each of the main torque signal and the sub torque signal is set to the middle point of the torque signal when no torque is applied. Therefore, when the torque is not detected, the output voltages of the main-side differential output circuit 69 and the sub-side differential output circuit 70 are in accordance with the offset voltage, and when the torque is detected, the direction of the torque is determined. Accordingly, the output voltage changes in the increasing or decreasing direction with reference to the offset voltage, and the magnitude and direction of the torque are detected.

A main torque signal and a sub torque signal corresponding to the detected torque are supplied to a power steering device.
The power steering device controls the rotation of the electric motor that assists the steering force in accordance with one of the applied main torque signal and the sub torque signal. Also,
If a voltage difference occurs between the main torque signal and the sub torque signal, an abnormality occurs in the torque detecting circuit, and it is determined that the torque is erroneously detected, and control of the electric motor for assisting the steering force is stopped.

[0015]

In the conventional torque sensor as shown in FIG. 7, the coil 43 for detecting the torque and the coil 44 for compensating for the temperature are each a single system.
There is a problem in that a contact failure occurs in the connection to the winding or the amplifier circuit board, and even if a midpoint shift occurs, it cannot be detected. Further, in the conventional torque sensor as shown in FIG. 8, when the supplied power supply voltage is reduced due to a contact failure of the connector portion or a decrease in the battery voltage, the sensor output is reduced by the main torque signal and the sub torque signal. However, in this case, the main torque signal does not always indicate the middle point, and depending on the value of the sub torque signal, a decrease in the sensor output cannot be detected, and the steering operation is stable. There is no problem.

The present invention has been made in view of the above-described circumstances. According to the first invention, even if each of the torque detecting coil and the temperature compensating coil is a single system, a contact failure is detected. It is an object of the present invention to provide a torque sensor capable of performing the above. According to the second aspect, when the supplied power supply voltage is reduced, the main torque signal can indicate the middle point, and the drop of the power supply voltage can be reliably detected by reliably detecting the drop of the sensor output. It is an object of the present invention to provide a torque sensor capable of performing the following.

[0017]

According to a first aspect of the present invention, there is provided a torque sensor for detecting a torque based on a change in impedance generated in a coil according to a torque to be detected. Means to shed,
AC component detecting means for detecting an AC component included in the output voltage of the coil, DC component detecting means for detecting a DC component included in the output voltage of the coil, and based on the DC component detected by the DC component detecting device. Means for detecting an abnormality, wherein the torque is detected based on the alternating current detected by the alternating current detecting means.

[0018] In this torque sensor, the flowing means supplies a constant current to the coil, the AC component detecting means detects an AC component included in the output voltage of the coil, and the DC component detecting device includes the AC component in the output voltage of the coil. The means for detecting the DC component and detecting the abnormality detects the abnormality based on the DC component detected by the DC component detecting means. Then, the torque is detected based on the AC component detected by the AC component detecting means. Thereby, even if the coil for torque detection and the coil for temperature compensation are each a single system, a contact failure can be detected.

A torque sensor according to a second aspect of the present invention includes a first torque signal output circuit and a second torque signal output for adding a reference voltage given from a reference voltage circuit to a voltage related to the detected torque and outputting the torque signal. In the torque sensor having a circuit, the reference voltage circuit is driven by a first voltage to supply a reference voltage to a first torque signal output circuit, and a second reference voltage circuit is driven by a second voltage higher than the first voltage. A second reference voltage circuit for applying a reference voltage to the second torque signal output circuit, and a second reference voltage circuit for driving the second reference voltage circuit.
Means for stopping supply of the second voltage to the second reference voltage circuit when the voltage is lower than the predetermined voltage.

In this torque sensor, the first reference voltage circuit of the reference voltage circuit is driven by the first voltage to apply a reference voltage to the first torque signal output circuit, and the second reference voltage circuit of the reference voltage circuit is driven by the first reference voltage circuit. The reference voltage is applied to the second torque signal output circuit driven by the second voltage higher than the voltage. The stopping means stops the supply of the second voltage to the second reference voltage circuit when the second voltage for driving the second reference voltage circuit is lower than the predetermined voltage. As a result, the output difference between the first torque signal output circuit and the second torque signal output circuit increases, so that a decrease in the sensor output can be reliably detected, and a decrease in the supplied power supply voltage can be reliably detected.

A torque sensor according to a third aspect of the present invention supplies a second voltage to the first torque signal output circuit as a drive voltage. When the supplied second voltage is lower than the first voltage, the first voltage is supplied to the first torque signal output circuit.
The apparatus further comprises means for supplying a voltage to the first torque signal output circuit as a drive voltage.

In this torque sensor, the supplying means is:
The second voltage is supplied to the first torque signal output circuit as a drive voltage. When the supplied second voltage is lower than the first voltage, the first voltage is supplied to the first torque signal output circuit as a drive voltage. When the power supply voltage is lowered, the main torque signal can indicate the middle point, and by reliably detecting the drop in the sensor output, the drop in the power supply voltage can be reliably detected.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below.
The description will be made based on the drawings showing the above. Embodiment 1 FIG. FIG. 1 is a block diagram showing a configuration of an embodiment of a torque sensor according to the first invention. In this torque sensor, the voltage output by the oscillation circuit 10a is supplied to constant current circuits 11 and 21 (means for flowing), and based on this, the constant current circuits 11 and 21 output a constant current regardless of the load. The constant current output from the constant current circuit 11 is applied to a detection coil 12 whose impedance changes according to the applied torque, and the constant current output from the constant current circuit 21 is applied to a compensation coil 22 for temperature compensation.

The voltage from the detection coil 12 is applied to high-pass filters 13 and 15 (AC component detecting means), and the high-pass filters 13 and 15 allow the AC component to pass through the applied voltage from the detection coil 12 respectively. The transmitted AC component is detected by detection circuits 14 and 16 and supplied to differential amplifiers 30 and 33, respectively. The voltage from the compensation coil 22 is supplied to high-pass filters 23 and 25 (AC component detecting means), and the high-pass filters 23 and 25 respectively transmit and transmit the AC component from the supplied voltage from the compensation coil 22. The AC component is detected by the detection circuits 24 and 26, respectively.
0,33.

Each of the differential amplifiers 30 and 33 includes a detection component for an AC component of the output voltage of the given detection coil 12,
The difference between the output voltage of the compensation coil 22 and the detected component of the AC component is amplified, and output as the main torque signal and the sub torque signal after temperature compensation via the output buffers 31 and 34. The main torque signal and the sub torque signal output via the output buffers 31 and 34 are provided to a power steering device (not shown).

The main torque signal and the sub torque signal output via the output buffers 31 and 34 are compared with each other, and when the difference is larger than a predetermined value, a signal notifying that an abnormality has occurred is output. Abnormality detection circuit 38
(Means for detecting an abnormality). The high-pass filters 13, 23, the detection circuits 14, 24, the differential amplifier 30, and the output buffer 31 constitute a main torque detection circuit 36, and the high-pass filters 15, 25, the detection circuit 16,
26, the differential amplifier 33 and the output buffer 34 constitute a sub torque detection circuit 37.

On the other hand, the voltage from the detection coil 12 is also supplied to a low-pass filter 17 (DC component detecting means), and the low-pass filter 17 transmits a DC component from the supplied voltage from the detection coil 12 and transmits the DC component. The DC component is input to a comparison circuit 18 (means for detecting an abnormality) and is compared with a predetermined value. The voltage from the compensating coil 22 is also supplied to a low-pass filter 27 (DC component detecting means). The low-pass filter 27 allows the DC component to pass from the given voltage from the compensating coil 22, and the transmitted DC component is Is input to a comparison circuit 28 (means for detecting an abnormality) and is compared with a predetermined value. The comparison results of the comparison circuits 18 and 28 are as follows:
The output of the switching circuit 35 is input to a switching circuit 35 (means for detecting an abnormality).
Given to.

The operation of the torque sensor having such a configuration will be described below. The voltage (for example, 2 to 5 V around 3.5 V) output from the oscillation circuit 10 a is applied to the constant current circuit 11,
21. Based on this, the constant current circuits 11, 21
Outputs a constant current regardless of the load. Constant current circuit 1
The constant current output by 1 is supplied to the detection coil 12, and the constant current output by the constant current circuit 21 is supplied to the compensation coil 22 for temperature compensation.

The voltage from the detection coil 12 changes according to the impedance which changes according to the applied torque.
The high-pass filters 13 and 15 are respectively provided. The high-pass filters 13 and 15 are provided with the given detection coil 1.
The AC components are respectively transmitted from the voltage from the second, and the transmitted AC components are detected by the detection circuits 14 and 16, respectively, and supplied to the differential amplifiers 30 and 33. Compensation coil 2
2 are applied to the high-pass filters 23 and 25, respectively. The high-pass filters 23 and 25 transmit an AC component from the applied voltage from the compensation coil 22, respectively. The transmitted AC component is detected by detection circuits 24 and 26, respectively, and supplied to differential amplifiers 30 and 33.

The differential amplifier 30 is provided with a detection component for an AC component of the output voltage of the given detection coil 12 and a compensating coil 22.
And a difference between the output voltage and the AC detection component is amplified and output as a main torque signal after temperature compensation via the output buffer 31. The differential amplifier 33 includes a detection component for an AC component of the output voltage of the given detection coil 12 and the compensation coil 2.
The difference between the output voltage of the second output signal and the detection component of the AC component is amplified and output as a temperature-compensated sub-torque signal via the output buffer 34.

The main torque signal and the sub torque signal output via the output buffers 31 and 34 are supplied to a power steering device (not shown), and the power steering device outputs one of the supplied main torque signal and sub torque signal. The rotation of the electric motor assisting the steering force is controlled in accordance with the torque signal. Output buffer 3
The main torque signal and the sub-torque signal output via 1 and 34 are applied to an abnormality detection circuit 38. The abnormality detection circuit 38 compares the applied two signals and, when the difference is larger than a predetermined value, an abnormality occurs. It outputs a signal notifying that it has done so.

On the other hand, the voltage from the detection coil 12 is also supplied to the low-pass filter 17,
Transmits a DC component from a given voltage from the detection coil 12, and the transmitted DC component is input to the comparison circuit 18. The comparison circuit 18 compares the input DC component with a predetermined value, and when the DC component falls below the predetermined value, determines that a contact failure has occurred and outputs a notification signal to the switching circuit 35.

The voltage from the compensation coil 22 is also supplied to a low-pass filter 27,
Transmits a DC component from a given voltage from the compensation coil 22, and the transmitted DC component is input to the comparison circuit 28. The comparison circuit 28 compares the input DC component with a predetermined value, and when the DC component falls below the predetermined value, determines that a contact failure has occurred and outputs a notification signal to the switching circuit 35. The switching circuit 35 includes the comparison circuits 18 and 2
8, when the notification signal of the occurrence of the contact failure is input, the output of the sub torque signal from the output buffer 34 is stopped. At this time, the abnormality detection circuit 38
Detects that the difference between the main torque signal and the sub torque signal has increased, and outputs a signal notifying that an abnormality has occurred.

Embodiment 2 FIG. 2 is a block diagram showing the configuration of the embodiment of the torque sensor according to the second and third inventions. This torque sensor includes a compensation coil 61 for temperature compensation and a detection coil 62 whose impedance changes in accordance with the applied torque.
, A series circuit of a resistor 63, a variable resistor 64 and a resistor 65, and a series circuit of a resistor 66, a variable resistor 67 and a resistor 68.

The voltage at the connection point between the compensation coil 61 and the detection coil 62 and the variable terminal voltage of the variable resistor 64 are supplied to a main-side differential output circuit 69 (first torque signal output circuit), and the difference between them is detected. , Torque sensor connector TCN
The signal is output to the main terminal TMAIN of FIG. Compensation coil 6
1 and the voltage at the connection point of the detection coil 62 and the variable resistor 67
Is supplied to the sub differential output circuit 70 (second torque signal output circuit), and the difference is detected and output to the sub terminal TSSUB of the connector TCNa of the torque sensor.

On the other hand, a power supply voltage Vcc (second voltage) of +8 V applied through a power supply terminal TV of the connector TCNa.
Are supplied to the oscillation circuit 60, the switching circuit 72 (stopping means), and the sub-side differential output circuit 70 as drive voltages. As shown in FIG. 3, the switching circuit 72 has a power supply voltage Vcc of +8 V applied to the emitter, a collector connected to the reference power supply circuit 71 (second reference voltage circuit), and a resistor 77 between the base and the emitter. A PNP transistor 76 having a resistor 78 connected between ground.

The power supply terminal TVr of the connector TCNa
The power supply voltage Vcc (first voltage) of +5 V provided through ef is supplied to the reference power supply circuit 73 (first reference voltage circuit) as a drive voltage. Main side differential output circuit 6
The driving voltage of the diode 9 is a diode 74 (supplying means) having a power supply voltage Vcc (second voltage) of +8 V applied to the anode.
+ 5V power supply voltage Vcc (first
The voltage is supplied from a common connection point with the cathode of the supplied diode 75 (supply means).

The reference power supply circuit 71 generates two predetermined reference voltages, gives one as a reference voltage for determining the oscillation frequency of the oscillation circuit 60, and gives the other one to the sub-side differential output circuit 70. This is given as the offset voltage of the non-inverting input terminal. The reference power supply circuit 73 generates one predetermined reference voltage and supplies it as an offset voltage of the non-inverting input terminal of the main-side differential output circuit 69.

The operation of the torque sensor having such a configuration will be described below. When power supply voltages Vcc + 8V and + 5V are applied to the power supply terminals TV and TVref, the oscillation circuit 60 oscillates, and the reference power supply circuit 71 outputs two reference voltages.
The oscillation voltage of the oscillation circuit 60 is a parallel circuit of a series circuit of the compensation coil 61 and the detection coil 62, a series circuit of the resistor 63, the variable resistor 64 and the resistor 65, and a series circuit of the resistor 66, the variable resistor 67 and the resistor 68. Given to both ends.

The voltage at the connection point between the compensation coil 61 and the detection coil 62 and the voltage at the variable terminal of the variable resistor 64 are given to the main-side differential output circuit 69, and the main-side differential output circuit 69 And a temperature compensated voltage difference is detected, an offset voltage is added to the detected voltage difference, and the main terminal TMAI is output as a main torque signal.
Output to N. The voltage at the connection point between the compensation coil 61 and the detection coil 62 and the voltage at the variable terminal of the variable resistor 67 are supplied to the sub differential output circuit 70,
0 detects a voltage difference corresponding to the applied torque and temperature compensated, adds an offset voltage to the detected voltage difference, and outputs it to the sub-terminal TSUB as a sub-torque signal.

The offset voltage is applied so that each of the main torque signal and the sub torque signal is set to the middle point of the torque signal when no torque is applied. Therefore, when the torque is not detected, the output voltages of the main-side differential output circuit 69 and the sub-side differential output circuit 70 are in accordance with the offset voltage, and when the torque is detected, the direction of the torque is determined. Accordingly, the output voltage changes in the increasing or decreasing direction with reference to the offset voltage, and the magnitude and direction of the torque are detected.

A main torque signal and a sub torque signal corresponding to the detected torque are supplied to a power steering device.
The power steering device controls the rotation of the electric motor that assists the steering force in accordance with one of the applied main torque signal and the sub torque signal.

Here, the power supply voltage Vcc (second voltage) applied through the power supply terminal TV decreases due to the contact failure of the connector TCNa or the voltage decrease of the power supply battery (not shown), and the switching circuit 72 (FIG. 3) Resistance 77,78
When the voltage becomes lower than the predetermined voltage determined by, the transistor 76 is turned off, and the supply of the power supply voltage Vcc to the reference power supply circuit 71 is stopped. Similarly, the power supply voltage Vcc (second voltage) given through the power supply terminal TV decreases,
When the voltage drops below + 5V and the diode 74 turns off,
The diode 75 is turned on, and a voltage of +5 V is supplied to the main-side differential output circuit 69 as a drive voltage.

At this time, the offset voltage of the main-side differential output circuit 69 is normally given from the reference power supply circuit 73, and the middle point of the main torque signal is reliably output.
Accordingly, the sensor output of the main-side differential output circuit 69 and the sensor output of the sub-side differential output circuit 70 are, for example, as shown in FIG. 4. When the power supply voltage is higher than 7 V, both sensor outputs are normal. is there. When the power supply voltage is 5 V to 7 V, the range of both sensor outputs is narrowed. When the power supply voltage is 5 V from the predetermined voltage, both sensor outputs indicate the middle points. When the power supply voltage is lower than the predetermined voltage, the sensor output of the main-side differential output circuit 69 indicates a middle point, and the sensor output of the sub-side differential output circuit 70 is 0 with a slope due to a time constant.
Therefore, the difference between the two is detected, and the abnormality can be reliably detected.

FIGS. 5 and 6 are a plan view and a side view showing an example of the configuration around the electric motor and the torque sensor of the electric power steering apparatus. The electric power steering apparatus includes a rudder shaft 100 interlocked with a steering wheel for steering, and a housing 101 that rotatably stores and supports the rudder shaft 100.
Drive control is performed based on a lower-side mounting tool 102 for mounting the lower side of the housing 101 to the vehicle body, an upper-side mounting tool 103 for mounting the longitudinal center portion of the housing 101 to the vehicle body, and a steering torque applied to the steering wheel. And an electric motor 108 for assisting steering.

The housing 101 has a cylindrical pipe portion 1.
09 and a molded cylindrical portion 1 whose ends are connected by press-fitting.
10, and an upper-side mounting member 103 is attached to the center of the pipe portion 109 in the axial length direction.
On one side of the motor 10, there is provided a motor-side cylindrical portion 111 in which a speed reduction mechanism linked to the electric motor 108 is housed. Also,
A torque sensor for detecting a torque acting on the rudder shaft 100 is housed in the molded cylinder 110, and the molded cylinder 110 and the motor-side cylinder 111 are attached by a plurality of attachment screws 112.

In such an electric power steering apparatus, heat generated from the electric motor 108 during operation is transmitted to the torque sensor in the molding cylinder 110, and may affect the output of the torque sensor. Therefore, FIG.
As shown in (1), a fin 108a for heat dissipation is provided on the side of the molding cylinder 110 of the housing of the electric motor 108. Also,
If the amount of heat generated by the electric motor 108 is large,
As shown in FIG. 6, a heat dissipating fin 110a is provided on the side closer to the motor side cylindrical portion 111 of FIG.

As a result, the surface area from the electric motor 108 to the molding cylinder 110 (the housing of the torque sensor) is increased, and the heat radiation performance is improved, so that the heat generated in the electric motor 108 is transmitted to the torque sensor. This makes it possible to minimize the influence of the heat generated by the electric motor 108 on the output of the torque sensor.

[0049]

According to the torque sensor of the first invention,
Even if the coil for torque detection and the coil for temperature compensation are each a single system, a contact failure can be detected.

According to the torque sensor according to the second aspect of the invention, the output difference between the first torque signal output circuit and the second torque signal output circuit is increased, and a decrease in the sensor output can be reliably detected. Can be reliably detected.

According to the torque sensor according to the third aspect of the invention, when the supplied power supply voltage decreases, the main torque signal can indicate the middle point, and by reliably detecting the decrease in the sensor output, Voltage drop can be detected reliably.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a torque sensor according to a first invention.

FIG. 2 is a block diagram showing a configuration of an embodiment of a torque sensor according to the second and third inventions.

FIG. 3 is a circuit diagram illustrating a configuration example of a switching circuit.

FIG. 4 is a graph showing characteristics of a sensor output of a main-side differential output circuit and a sensor output of a sub-side differential output circuit depending on a power supply voltage.

FIG. 5 is a plan view showing a configuration example around an electric motor and a torque sensor of the electric power steering device.

FIG. 6 is a side view showing a configuration example around an electric motor and a torque sensor of the electric power steering device.

FIG. 7 is a block diagram showing a configuration example of a conventional torque sensor.

FIG. 8 is a block diagram illustrating another configuration example of a conventional torque sensor.

[Explanation of symbols]

10a, 60 Oscillation circuit 11, 21 Constant current circuit (flow means) 12 Detection coil 13, 15, 23, 25 High pass filter (AC component detection means) 17, 27 Low pass filter (DC component detection means) 18 Comparison circuit (abnormality Means for detecting) 22 Compensation coil 30, 33 Differential amplifier 35 Switching circuit (means for detecting abnormality) 38 Abnormality detection circuit (means for detecting abnormality) 61 Coil for temperature compensation 62 Detection coils 63, 65, 66, 68 Resistance 64, 67 Variable resistance 69 Main-side differential output circuit (first torque signal output circuit) 70 Sub-side differential output circuit (second torque signal output circuit) 71 Reference power supply circuit (second reference voltage circuit) 72 Switching circuit (Means for stopping) 73 Reference power supply circuit (first reference voltage circuit) 74, 75 Diode (means for supplying) 76 PNP transistor

Claims (3)

[Claims] 1. A torque sensor for detecting a torque based on a change in impedance generated in a coil according to a torque to be detected, wherein: a means for flowing a constant current to the coil; and an AC included in an output voltage of the coil. AC component detecting means for detecting the component, DC component detecting means for detecting a DC component included in the output voltage of the coil, based on the DC component detected by the DC component detecting device,
Means for detecting an abnormality, wherein the torque is detected by the AC component detected by the AC component detecting means. 2. A torque sensor having a first torque signal output circuit and a second torque signal output circuit for adding a reference voltage given from a reference voltage circuit to a voltage related to a detected torque and outputting the resultant signal as a torque signal. The reference voltage circuit is driven by a first voltage to supply a reference voltage to a first torque signal output circuit, and is driven by a second voltage higher than the first voltage to reference a second torque signal output circuit. A second reference voltage circuit for applying a voltage; and means for stopping supply of the second voltage to the second reference voltage circuit when the second voltage for driving the second reference voltage circuit is lower than a predetermined voltage. A torque sensor characterized in that: 3. A second voltage is supplied to the first torque signal output circuit as a drive voltage, and when the supplied second voltage is lower than the first voltage, the first voltage is supplied to the first torque signal output circuit. 3. The apparatus according to claim 2, further comprising: means for supplying a voltage.
The torque sensor as described.