JP2967250B2 - Torque sensor - Google Patents

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 proposes, for example, a torque sensor suitable for an electric power steering device of an automobile.

[0002]

2. Description of the Related Art An electric power steering device has been developed as a power steering device for assisting an operating force of a steering wheel of an automobile. This has a structure in which torque applied to a steered wheel is detected, and an electric motor provided in a steering mechanism is driven in accordance with the detected torque to assist operating force of the steered wheel.

FIG. 1 is a half sectional view showing a structure of a torque detecting mechanism for detecting a torque based on a change in the facing area of the teeth. The input shaft 1 coaxially connects an upper shaft 1a on which a steering wheel (not shown) is mounted and a lower shaft 1c on which a steering mechanism is mounted via a torsion bar 1b.
Is rotatably supported via a bearing 3 on a cylindrical case 2 attached to the vehicle body. Lower end of upper shaft 1a (left side in drawing)
A first sleeve 4a made of a non-magnetic material is externally fitted and fixed to the outer peripheral surface, and first and second torque detecting rings 5 and 6 formed of a magnetic material cylinder are externally fitted and fixed to the outer periphery of the first sleeve 4a at an appropriate distance in the axial direction. is there. First
The right edge of the torque detection ring 5 is a plane perpendicular to the axis of the input shaft 1, and the left edge is a large number of rectangular teeth 5.
are formed at equal pitches in the circumferential direction.

[0004] The second torque detecting ring 6 has a right end edge facing the first torque detecting ring 5.
Are formed in parallel with the left end edge thereof, and a large number of rectangular teeth 6a, 6a,. The tooth width dimension of the tooth portion 6a is the notch 6b between the tooth portions 6a, 6a.
Is selected to be approximately equal to the width dimension of

A second sleeve 4b made of a non-magnetic material is externally fitted and fixed to the upper end portion (right side in the drawing) of the lower shaft 1c, and a third torque detecting ring 7 made of a magnetic material cylinder is externally fitted and fixed to the outer periphery. It is. On the right edge of the torque detecting ring 7, a number of teeth 7a, 7a,... Having the same width, the same shape, and the same pitch as the teeth 6a formed on the torque detecting ring 6 are formed. When the torque is not acting on the torsion bar 1b, the teeth 6a, 7a of the torque detecting rings 6, 7 are opposed to each other at an appropriate length of the tooth width.

Inside the case 2, magnetic cylinders 8A and 8B each having a U-shaped cross section and having an inner flange are fixedly fitted. The cylindrical body 8A has a length dimension that straddles the torque detecting rings 5 and 6, and its central portion in the axial direction is a position facing the torque detecting rings 5 and 6, and the cylindrical body 8B is It has a length dimension that straddles 6 and 7, and its central portion in the axial direction is disposed as a position facing the torque detection rings 6 and 7.

A temperature compensating coil L ₁ and a torque detecting coil L ₂ are wound around the cylinders 8A and 8B, respectively, along the circumferential direction. These temperature compensation coil L ₁ and torque detection coil L
By connecting ₂ to an oscillator (not shown), the cylinder 8A forms a magnetic circuit with the torque detection rings 5 and 6, and the cylinder 8B forms a magnetic circuit with the torque detection rings 6 and 7, respectively.

Then, from the torque detecting coil L ₂ , the teeth 6 a of the torque detecting ring 6 and the teeth of the torque detecting ring 7 are formed.
The voltage corresponding to the area facing 7a, that is, the voltage corresponding to the magnetic resistance is output. Therefore, when the upper shaft 1a rotates the torsion bar 1b twists, the impedance of the facing area is varied torque detection coil L ₂ between the teeth 7a of the tooth portion 6a and the torque detection ring 7 of the torque detection ring 6 It changes, and the torque applied to the torsion bar 1b is detected by the voltage output according to the change.

FIG. 2 is a block diagram showing a circuit configuration of a torque sensor which has been filed by the present applicant in Japanese Patent Application No. 3-361207. Voltage stabilizing circuit 9 for outputting DC voltage
The voltage output terminal 9a is connected to a resistor r constituting the voltage dividing circuit 10.
₁ and r ₂ are grounded via a series circuit, and a resistor r
The connection portion 10a between ₁ and r ₂ is grounded via a capacitor C that lowers the impedance with respect to the oscillating voltage described later. The torque detection circuit 17 includes a temperature compensation coil L ₁
And a series circuit of the torque detection coil L _2, and a series circuit of resistors R ₁ and R ₂ is configured by parallel connection.

[0010] partial connection portions 10a of the pressure circuit 10 is connected to the connecting portion 17a of the torque detection coil L ₂ and the resistance R ₂ in the voltage input terminal 11a and a torque detecting circuit 17 of the oscillation circuit 11. Voltage output terminal 11b of the oscillation circuit 11 is connected portions of the temperature compensation coil L ₁ and the resistor R ₁ in the torque detection circuit 17
Connected to 17b. The voltage at the connection 10a of the voltage dividing circuit 10 is selected to determine the value of the DC voltage included in the oscillation voltage output from the voltage output terminal 11b of the oscillation circuit 11.

[0011] from the temperature compensation coil L ₁ and the torque detection coil L ₂ of the connecting portion 17c, is output AC voltage V _T corresponding to the torque to be detected divided oscillation voltage from resistors R ₁ and R ₂ of the connecting portion 17d reference voltage V _S of the pressure alternating is to be outputted.

Next, the torque sensor having the above-described structure will be described.
The operation for detecting the torque will be described. Output voltage of voltage stabilizing circuit 9
Is the resistance r of the voltage dividing circuit 10.₁And r_TwoIs divided by
Anti-r ₁And r_TwoBy the voltage of the connection part 10a divided by
Oscillation voltage output from voltage output terminal 11b of oscillation circuit 11
The voltage value of the included DC voltage is determined. The oscillation circuit 11
The oscillating voltage including the output DC voltage is the temperature compensation coil L
₁And resistance R₁To the connection 17b.
Outgoing coil L_TwoAnd resistance R_TwoThe connecting portion 17a has a connecting portion 10
From a, a DC voltage equal to the DC voltage included in the oscillation voltage
Given. This allows connection in the torque detection circuit 17
Each of the sections 17a and 17b is supplied with the same DC voltage,
Degree compensation coil L₁And torque detection coil L_TwoSeries circuit with
And resistance R₁And resistance R_TwoDC current flows in the series circuit with
As a result, the burden on the oscillation circuit 11 is reduced.

Meanwhile, the temperature compensation coil L ₁ and the torque detection coil L ₂ of the connecting portion 17c in the alternating voltage V which is divided by the impedance of the two coils L _1, L ₂ the oscillating voltage is applied from the oscillation circuit 11 _T is output. So if impedance changes of the torque detection coil L ₂ in accordance with the torsion of the torsion bar 1b shown in FIG. 1, the AC voltage V _T of the connecting portion 17c of the temperature compensation coil L ₁ and the torque detection coil L ₂ is changed Te, it is possible to detect the torque applied to the torsion bar 1b by the alternating voltage V _T. Also the connection portion 17d of the resistor R ₁ and R _2, the reference voltage V _S obtained by dividing the oscillation voltage min is obtained.

Therefore, the AC voltage V _T and the reference voltage V _S
By comparing with, the torsional direction of the torsion bar 1b can be detected. That in the case of V _T> V _S rotation in the one direction of the torsion bar, in the case of V _T <V _S can detect the rotation of the other direction of the torsion bar. When the ambient temperature changes, the temperature compensation coil L ₁
Since the impedance and rate of change of the impedance of the torque detection coil L ₂ equal, the AC voltage V _T becomes what is temperature compensated, without affected by the temperature change in the ambient temperature, the torque applied to the torsion bar 1b It can always be detected accurately.

[0015]

However, in the conventional torque sensor, the oscillation voltage of the oscillation circuit is applied to both ends of the series circuit of the temperature compensation coil and the torque detection coil. Is applied, the output of the torque detection coil is small, and the torque detection sensitivity is low. Further, in order to convert the voltage generated in the temperature compensation coil and the torque detection coil into a DC voltage, it is necessary to provide a clamp circuit, a peak hold circuit, and the like, which causes a problem that the circuit becomes complicated. The present invention has been made in view of the above problems, and has as its object to provide a high-sensitivity torque sensor that can increase the output of a torque detection coil, can simplify a circuit, and is inexpensive.

[0016]

A torque sensor according to the present invention includes a parallel circuit in which a series circuit of a first resistor and a second resistor is connected in parallel to a series circuit of a temperature compensation coil and a torque detection coil. A torque sensor that applies an oscillating voltage including a DC voltage to one side of the parallel circuit so as to detect torque by a voltage at a connection between a temperature compensation coil and a torque detection coil, An inverting circuit for applying a voltage shifted in phase by 180 ° to the other side of the parallel circuit;
A differential amplifier circuit to which a voltage at a connection between the temperature compensation coil and the torque detection coil and a voltage at a connection between the first resistor and the second resistor are input; Is configured to detect the torque based on

[0017]

When an oscillating voltage including a DC voltage is applied to one side of a series circuit of a temperature compensating coil and a torque detecting coil, and a voltage obtained by shifting the phase of the oscillating voltage by 180 ° is applied to the other side, the temperature compensating coil and the torque detecting coil are detected. A voltage twice the oscillation voltage is applied to the series circuit with the coil, and the voltage applied to the torque detection coil is the same as the oscillation voltage. In addition, the DC voltage applied to one side and the other side is canceled, so that no DC current flows through the temperature compensation coil and the torque detection coil.
As a result, the output of the torque detection coil increases, and the current load on the current amplifier circuit can be reduced.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing the embodiments. FIG. 3 is a block diagram showing a circuit configuration of the torque sensor according to the present invention. An output terminal for outputting an oscillating voltage including a DC voltage of the oscillating circuit 30 oscillating by receiving a power supply voltage from the DC power supply E is connected to the current amplifying circuit 31, the inverted current amplifying circuit 32, and the sampling pulse generating circuits 33 and Connected to each input terminal. An output terminal of the current amplification circuit 31,
Between the output terminal of the inverting current amplifier circuit 32, the series circuit of the temperature compensation coil L ₁ and the torque detection coil L ₂ is interposed. The series circuit of the temperature compensation coil L ₁ and the torque detection coil L _2, the first for the main circuit resistance R ₁ and the second resistor R ₂
And a series circuit of a first resistor R ₁ ′ and a second resistor R ₂ ′ for a fail-safe auxiliary circuit are connected in parallel. Connecting portions between the temperature compensation coil L ₁ and the torque detection coil L ₂ is connected to one input terminal of the one input terminal and a differential amplifier circuit 36 of the differential amplifier circuit 35.

The connection between the first resistor R ₁ and the second resistor R ₂ for the main circuit is connected to the other input terminal of the differential amplifier circuit 35. The connection between the first resistor R ₁ ′ and the second resistor R ₂ ′ for the auxiliary circuit is connected to the other input terminal of the differential amplifier circuit 36. The output terminal of the differential amplifier circuit 35 is a sample-and-hold circuit.
The input terminal of 37 and the output terminal of the differential amplifier circuit 36 are connected to the input terminal of the sample and hold circuit 38. The pulse output terminal of the sampling pulse generation circuit 33 is connected to the sampling pulse input terminal of the sample and hold circuit 37, and the pulse output terminal of the sampling pulse generation circuit 34 is connected to the sampling pulse input terminal of the sample and hold circuit 38.

The output terminal of the sample hold circuit 37 is connected to the input terminal of the voltage / current conversion circuit 39 and the sample hold circuit.
The output terminal 38 is connected to the input terminal of the voltage / current conversion circuit 40. The voltage / current conversion circuit 39 outputs a torque detection signal T _S for the main circuit, and the voltage / current conversion circuit 40 outputs a torque detection signal T _S ′ for the auxiliary circuit.

Next, the operation of the torque sensor constructed as described above will be described with reference to FIG. 4, FIG. 5, FIG. 6, FIG. 7, FIG. FIG.
This will be described with reference to FIGS. 10 and 11. Now, when the oscillation operation of the oscillation circuit 30, an oscillation circuit 30 outputs a biased oscillation voltage V _A by the DC voltage V _D as shown in FIG.
Then, the oscillation voltage _{VA including the} DC voltage V _D is input to the current amplifier circuit 31 and the inverted current amplifier circuit 32, and the current amplifier circuit 31 outputs the AC voltage having the same phase as the output voltage of the oscillator circuit 30 as shown in FIG. the voltage V _B, and outputs a positive DC voltage V _D.

On the other hand, the inverted current amplifying circuit 32 is as shown in FIG.
In which the phase of the oscillation voltage of the oscillation circuit 30 is shifted by 180 °
Voltage V_CAnd a positive DC voltage V_DIs output. to this
More temperature compensation coil L₁And torque detection coil L_TwoDirectly with
AC voltage V is applied to both ends of the column circuit. _BAnd V_CVoltage difference between
Oscillation voltage V_AGiven a voltage twice as high as
Detection coil L_TwoHas an oscillation voltage V_AAnd same voltage
Is given.

Further temperature compensation coil L ₁ and the temperature compensating coil L ₁ and the torque detection coil L for the one side and the other side of the series circuit are given DC voltage V _D of the same potential of the torque detection coil L _{2 No} DC current flows through ₂ . And
AC voltage at the connection of the temperature compensation coil L ₁ and the torque detection coil L _2, as shown in FIG. 7, the torque detection coil L
If the _second impedance is the impedance greater than the temperature compensation coil L _1, the oscillation voltage V AC voltage _A and in phase with the change in V _B, is less contrary to the AC voltage V _C of the oscillating voltage V _A and antiphase To change.

The first resistor R₁And the second resistor R_TwoConnection with
As shown in FIG.₁And R_TwoWhen
Are equal, the DC voltage V_DBecomes And temperature compensation
Coil L₁And torque detection coil L_TwoVoltage and connection
And the first resistor R₁And the second resistor R _TwoThe voltage at the connection with
It is input to the amplifier circuit 35 and differentially amplified, and its output voltage is
The output voltage changes as shown in FIG.
Input to the threshold circuit 37.

The oscillation voltage _VA of the oscillation circuit 30 is input to the sampling pulse generation circuit 33, and is synchronized with the oscillation voltage _VA as shown in FIG.
SP is generated, and the sampling pulse SP is supplied to the sample hold circuit 37. Whereby the sample-and-hold circuit 37, an AC voltage V _B which is input from the differential amplifier circuit 35 as shown in FIG. 11 at the timing of the sampling pulse SP is given by sampling and holding a voltage signal corresponding to the detected torque _SV is obtained.

The sampled and held voltage signal S _V
Is input to the voltage / current conversion circuit 39 to be converted into a current signal and to give a predetermined offset value to output a torque detection signal T _S for the main circuit. By driving a motor (not shown) for assisting the steering force based on the torque detection signal T _S , the steering force can be properly assisted.

On the other hand, the voltage at the connection between the temperature compensating coil L ₁ and the torque detecting coil L ₂ and the first resistor R for the auxiliary circuit
₁ 'and the second resistor R _2' the voltage at the connection portion between the differential amplifier circuit
The voltage / current conversion circuit is operated in the same manner as when the signal is input to the differential amplifier 36 and differentially amplified to obtain the main circuit torque detection signal T _S.
And outputs a torque detection signal T _S 'for the auxiliary circuits which changes in the same manner as the torque detection signal T _S for the main circuit 40. Thus, when the torque detection signal for the main circuit disappears, the operation can be shifted to the fail-safe operation by the torque detection signal for the auxiliary circuit.

As described above, according to the present invention, the same voltage as the oscillation voltage output from the oscillation circuit can be applied to the torque detection coil, so that the output of the torque detection coil can be increased and the torque can be detected with high sensitivity. it can. Also, since the same potential DC voltage is applied to the other side of the series circuit of the temperature compensation coil and the torque detection coil, no DC current flows from the oscillation circuit through the temperature compensation coil and the torque detection coil, and the current load of the current amplification circuit is reduced. Can be reduced. Further, the voltage at the connection between the temperature compensation coil and the torque detection coil and the voltage at the connection between the first resistor and the second resistor are directly input to the differential amplifier circuit, and the torque is determined by the output voltage of the differential amplifier circuit. Can be detected, so that a clamp circuit, a peak hold circuit and the like are not required unlike the conventional torque sensor, the circuit configuration is simplified, and the cost can be reduced.

FIG. 12 is a partially cutaway sectional view showing another structure of the torque detecting mechanism. The same components as those of the torque detecting mechanism in FIG. 1 are denoted by the same reference numerals. On the outer side of the cylindrical body 8A made of a magnetic material, and turning the temperature compensation coil L _1a for the main circuit, and a on the inner peripheral side temperature compensation coil L _1b for auxiliary circuits each made independent winding. On the other hand, a torque detecting coil L for the main circuit is provided on the outer peripheral side of the cylindrical body 8B made of a magnetic material.
_On the inner peripheral side, a torque detection coil L _2b for an auxiliary circuit is wound independently.

FIG. 13 shows a temperature compensation coil L_1a, L_1bAnd Tor
Detection coil L_2a, L_2bOf the main part of the torque sensor using
FIG. 3 is a circuit diagram illustrating a configuration. The output side of the oscillation circuit 30
Kuta CN₁₁Temperature compensation coil L for auxiliary circuit _1bContact with
The temperature compensation coil L_1bIs the connector CN₁₂And connectors
TA CN_{twenty one}Through the torque detection coil L for the auxiliary circuit_2bWhen
Connected, torque detection coil L_2bIs the connector CN_{twenty two}Through
Grounded. The oscillation circuit 30 is connected to the connector CN.₃₁Through
Temperature compensation coil L for the main circuit_1aConnected to the temperature
Compensation coil L_1aIs the connector CN₃₂And connector CN₄₁Through
Torque detection coil L_2aAnd the torque detection coil L
_2aIs the connector CN₄₂Grounded.

Furthermore, the oscillation circuit 30 is grounded through a series circuit of a first resistor R ₁ 'and a second resistor R _2' for the auxiliary circuit, the first for the main circuit resistance R ₁ and a second resistor R ₂ Is grounded through a series circuit of Connection of the connector CN ₃₂ and CN ₄₁ includes one input terminal of the differential amplifier circuit 35 for the main circuit, the first
The connection between the resistor R ₁ and the second resistor R ₂ is connected to the other input terminal of the differential amplifier circuit 35. The connection between the connectors CN ₁₂ and CN ₂₁ is an input terminal on one side of the differential amplifier circuit 36 for the auxiliary circuit,
'And the second resistor R _2' first resistor R ₁ connected portion between is connected to the other input terminal of the differential amplifier circuit 36, the torque signal S _T for the main circuit from the differential amplifier circuit 35, a differential The amplifier circuit 36 outputs an auxiliary circuit torque signal _ST '.

As described above, the temperature compensation coil L_1a, L_1bas well as
Torque detection coil L_2a, L_2bConnectors at each end
(CN₃₁, CN₃₂), (CN₁₁, CN₁₂) And (CN₄₁, CN₄₂),
(CN _{twenty one}, CN_{twenty two}) Is provided, for example, for an auxiliary circuit.
Temperature compensation coil L_1bOr torque detection coil L_2bBreaks
Then, as shown in FIG. 14, the detection torque is output from the differential amplifier circuit 35.
Torque signal S according to the torque_TIs obtained, but the differential amplifier circuit
From 36, the torque signal S corresponding to the detected torque_T′
Disappears.

Further, for example, the connector CN ₁₁ is a contact failure, if the contact resistance is increased, although no change in the torque signal S _T, as shown in FIG. 15, the torque signal S _T 'for the auxiliary circuit reduced, the difference ΔS between the torque signal S _T and S _T 'increases according to the magnitude of the contact resistance. Further, the contact resistance of the connector CN ₂₁ is increased, there is no change in the torque signal S _T, as shown in FIG. 16, a torque signal for the auxiliary circuit S _T 'increases, the torque signal S _T according to the contact resistance And the difference ΔS between S _T ′ becomes larger.

Further, a second resistor R for the auxiliary circuit is provided._Two'of
When the resistance value changes, as shown in FIG.
Torque signal S_TDoes not change, but the torque signal for the auxiliary
No. S _T′ Decreases as resistance increases, and torque
No. S_TAnd S_T′ Is larger. Like this
The temperature compensation coil and torque detection coil for the main circuit.
And the auxiliary circuit are provided separately, and the
If connected to a differential amplifier circuit, the temperature compensation coil or torque
Disconnection of the detection coil, poor contact of the connector, or
If the resistance value of the first resistor or the second resistor changes, the torque
Signal S_TAnd S _T′ And the main circuit or auxiliary circuit
Can identify which circuit component on the road has failed
To ensure fail-safe operation.
You.

FIG. 18 is a half sectioned partial sectional view showing another configuration of the torque detecting ring and the cylindrical body of the torque detecting mechanism. Other configurations are the same as those of the structure of the torque detection mechanism shown in FIG. Inside the cylindrical body 80 made of a magnetic material, for example, a torque detection coil L is wound along the inner peripheral surface. A third torque detection ring 70 made of a large-diameter cylinder is arranged at a position facing the cylinder 80 at an appropriate distance from the small-diameter cylinder inside the distal end side of the torque detection ring 70. The distal end side of the second torque detecting ring 60 is loosely fitted and arranged to face each other. The torque detection ring 60 is attached to, for example, an upper shaft, and the torque detection ring 70 is attached to a lower shaft. The base end of each of the detection rings 60 and 70 is bent in an inverted L-shape and is slightly thick. A plurality of teeth 60a, 70a are formed at a predetermined pitch in the circumferential direction on the distal end side of the torque detecting rings 60, 70. A step is formed between one inner peripheral end face 80L of the cylindrical body 80 and the other inner peripheral end face 80R, and a step is formed between the inner peripheral end face 80L and the torque detecting ring 70 and the inner peripheral end face 80R. The distance between the motor and the torque detection ring 60 is equalized to prevent the generation of magnetic flux leakage.

When the torque detecting ring is configured as described above, when the relative rotation amount between the torque detecting rings 60 and 70 changes according to the torque, the area where the tooth portions 60a and 70a overlap changes. Then, the impedance of the torque detection coil L changes, and the torque applied to the torsion bar is detected by the voltage output according to the change. When the relative positions of the torque detecting rings 60 and 70 in the axial direction change due to an external impact or the like, the sensor output changes. That is, the output gain of the torque detection coil changes as shown by a dashed line in FIG. 19, where the vertical axis is the output gain of the torque detection coil and the horizontal axis is the axial relative displacement of the torque detection ring 70 with respect to the torque detection ring 60. . That is, the torque detection coil L
The output gain gradually decreases from the state of the initial set value of the relative position in the axial direction of 0 as the relative displacement increases and decreases, and changes like an arc curve indicated by a chain line. Note that the straight line X is a change in the output of the torque detecting coil in the case of the structure of the torque detecting ring as shown in FIG. 1, and in this case, it changes linearly.

The output of the midpoint of the torque detecting coil with respect to the relative displacement in the axial direction changes as shown by the chain line in FIG. The midpoint output decreases when the axial relative displacement is increased from the state of the initial setting value 0, and conversely, when the axial relative displacement decreases, the midpoint output increases. A straight line Y represents a change in the midpoint output of the torque detecting coil in the case of the structure of the torque detecting ring as shown in FIG. 1. In this case, the rate of change with respect to the axial relative displacement is larger than in the case of the torque detecting ring shown in FIG. .

As described above, when the distal end side (tooth side) of the large-diameter torque detecting ring and the distal end side (tooth side) of the small-diameter torque detecting ring have a structure in which they are loosely fitted to each other,
Changes in the output gain and the midpoint output of the torque detecting coil with respect to the axial relative displacement of the two torque detecting rings are reduced.
Therefore, the shock resistance of the torque detection mechanism is improved, and workability in assembling the torque detection mechanism can be improved.

FIG. 21 is a partially cutaway sectional view showing still another example of the structure of the torque detecting mechanism. Large diameter torque detection ring 7
The 0 'and the small-diameter torque detection ring 60' are both formed of a thin plate-shaped cylinder. Other configurations are the same as those shown in FIG. 18, and the same components are denoted by the same reference numerals. According to this torque detection mechanism, the same characteristics as the output gain and the midpoint output of the torque detection coil in the torque detection mechanism shown in FIG. 18 can be obtained.

[0040]

As described above in detail, according to the present invention, an oscillating voltage including a DC voltage output from an oscillating circuit is applied to one side of a series circuit of a temperature compensating coil and a torque detecting coil, and the oscillating voltage is applied to the other side. Since the voltage obtained by shifting the phase of the oscillating voltage by 180 ° is applied, the oscillating voltage can be applied to the torque detecting coil as it is, and the output of the torque detecting coil can be increased. Also, since a DC voltage of the same potential is applied to one side and the other side of the series circuit of the temperature compensation coil and the torque detection coil, no DC current flows through the temperature compensation coil and the torque detection coil, and the current load of the current amplification circuit is reduced. Can be reduced. Further, since a torque signal can be obtained by the differential amplifier circuit to which the voltage of the connection between the temperature compensation coil and the torque detection coil is input, the circuit configuration is simplified and the cost can be reduced. Therefore, the present invention has an excellent effect that a torque sensor having high sensitivity and stable operation can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a partially cutaway sectional view showing a configuration of a torque detection mechanism.

FIG. 2 is a block diagram showing a main configuration of a conventional torque sensor.

FIG. 3 is a block diagram showing a configuration of a torque sensor according to the present invention.

FIG. 4 is a waveform diagram of an output voltage of the oscillation circuit.

FIG. 5 is a waveform diagram of an output voltage of the current amplification circuit.

FIG. 6 is a waveform diagram of an output voltage of the inversion current amplifier circuit.

FIG. 7 is an AC voltage waveform diagram of a connection portion between a temperature compensation coil and a torque detection coil.

FIG. 8 is an output voltage waveform diagram of a connection portion between a first resistor and a second resistor.

FIG. 9 is an output voltage waveform diagram of the differential amplifier circuit.

FIG. 10 is a waveform diagram of an output voltage and a sampling pulse of the differential amplifier circuit.

FIG. 11 is a waveform diagram of an output voltage of a differential amplifier circuit, a sampling pulse, and a hold voltage of a sample hold circuit.

FIG. 12 is a partially cutaway sectional view showing another configuration of the torque detection mechanism.

13 is a main part circuit diagram of a torque sensor when the torque detection mechanism shown in FIG. 12 is used.

14 is a characteristic diagram of torque versus torque signal of the torque sensor shown in FIG.

FIG. 15 is a characteristic diagram of contact resistance versus torque signal of the connector of the torque sensor shown in FIG. 13;

16 is a characteristic diagram of contact resistance versus torque signal of the connector of the torque sensor shown in FIG.

17 is a characteristic diagram of a change in resistance value of the resistance of the torque sensor shown in FIG. 13 versus a torque signal.

FIG. 18 is a partially cutaway sectional view showing another configuration of the torque detection mechanism.

FIG. 19 is a graph showing the relative axial displacement of the torque detection ring shown in FIG. 18 versus the output gain characteristic of the torque detection coil.

20 is a characteristic diagram of the axial relative displacement of the torque detection ring shown in FIG. 18 versus the midpoint output characteristic of the torque detection coil.

FIG. 21 is a partially cutaway sectional view showing another configuration of the torque detection mechanism.

[Explanation of symbols]

30 the oscillation circuit 31 current amplifying circuit 32 inverting current amplifier 35 and 36 a differential amplifier circuit L ₁ temperature compensation coil L ₂ torque detecting coil R _1, R ₁ 'first resistor R _2, R _2' second resistor

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-2935 (JP, A) JP-A-2-195221 (JP, A) JP-A-4-67148 (JP, U) (58) Investigated Field (Int.Cl. ⁶ , DB name) G01L 3/10

Claims (1)

(57) [Claims] 1. A series circuit of a temperature compensation coil and a torque detection coil includes a parallel circuit in which a series circuit of a first resistor and a second resistor is connected in parallel, and one side of the parallel circuit includes a DC voltage. A torque sensor for applying an oscillating voltage and detecting a torque based on a voltage at a connection between a temperature compensation coil and a torque detecting coil, wherein a voltage obtained by shifting the phase of the oscillating voltage by 180 ° is applied to the parallel circuit. An inverting circuit to be applied to the other side, and a differential amplifier circuit to which a voltage at a connection between the temperature compensation coil and the torque detection coil and a voltage at a connection between the first resistor and the second resistor are input. A torque sensor configured to detect torque based on an output voltage of the differential amplifier circuit.