JPH05149805A - Torque sensor - Google Patents

Abstract

PURPOSE:To detect a torque highly sensitively and stably. CONSTITUTION:An oscillation circuit 11, a voltage stabilization circuit 9 outputting a DC voltage determining the DC voltage contained in an oscillation voltage which the oscillation circuit 11 outputs, and a torque detection circuit 17 comprising a series circuit of a temperature compensation coil L1 and a torque detection coil L2, are provided. The oscillation voltage containing the DC voltage outputted from the oscillation circuit 11 is given to one side end part 17b of the torque detection circuit 17, while the DC voltage being equal to the DC voltage contained in the oscillation voltage is given to the other side end part 17a from the voltage stabilization circuit 9.

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 a torque sensor suitable for, for example, 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 the operating force of steering wheels of an automobile. This has a structure in which the torque applied to the steered wheels is detected and an electric motor provided in the steering mechanism is driven according to the detected torque to assist the operating force of the steered wheels.

FIG. 1 is a half cross-sectional view showing the structure of a torque sensor for detecting torque based on a change in the facing area of a tooth portion. The input shaft 1 is an upper shaft to which steering wheels (not shown) are attached.
1a and a lower shaft 1c to which a steering mechanism is attached are coaxially connected via a torsion bar 1b, and the upper shaft 1a is freely rotatable via a bearing 3 in a cylindrical case 2 attached to the vehicle body. It is supported. A first sleeve 4a made of a non-magnetic material is externally fitted and fixed to the lower end portion (right side in the drawing) of the upper shaft 1a, and the outer circumference of the first sleeve 4a is made of a magnetic material, and the first and second torque detection rings 5,
6 is externally fitted and fixed at a proper distance in the axial direction. The right edge of the first torque detection ring 5 is a plane perpendicular to the axis of the input shaft 1, and the left edge has a large number of rectangular tooth portions 5a, 5a.
Are formed at equal pitches in the circumferential direction.

The right end of the second torque detecting ring 6 facing the first torque detecting ring 5 has the right edge.
Are opposed to each other in parallel with the left end edge of the tooth, and a large number of rectangular tooth portions 6a, 6a ... Are formed at equal intervals in the circumferential direction on the left end edge. The tooth width of the tooth 6a is determined by the notch 6b between the teeth 6a, 6a.
Is selected to be approximately equal to the width dimension of.

A non-magnetic second sleeve 4b is externally fitted and fixed to an upper end portion (right side in the drawing) of the lower shaft 1c, and a third torque detecting ring 7 formed of a magnetic cylinder is externally fitted and fixed to the outer periphery thereof. There is. A large number of tooth portions 7a, 7a ... Having the same width, the same shape and the same pitch as the tooth portion 6a formed on the torque detecting ring 6 are formed on the right end edge of the torque detecting ring 7. The tooth portions 6a and 7a of the torque detection rings 6 and 7 face each other at an appropriate length portion of the tooth width when no torque acts on the torsion bar 1b.

Inside the case 2, magnetic cylinders 8A, 8B having a U-shaped cross section and having an inner flange are internally fixed. The cylindrical body 8A has a length dimension that straddles the torque detection rings 5 and 6, and the central portion in the axial length direction is a position facing the torque detection rings 5 and 6, and the cylindrical body 8B is the torque detection ring. It has a length dimension that extends over 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 compensation coil L ₁ and a torque detection coil L ₂ are wound around the cylinders 8A and 8B along the circumferential direction thereof. These temperature compensation coil L ₁ and torque detection coil L
By connecting ₂ to an oscillator (not shown), the temperature compensation coil L ₁ is electromagnetically coupled to the torque detection rings 5 and 6, and the torque detection coil L ₂ is electromagnetically coupled to the torque detection rings 6 and 7, respectively.

From the torque detecting coil L ₂ , the tooth portion 6a of the torque detecting ring 6 and the tooth portion of the torque detecting ring 7 are connected.
The area facing 7a, that is, the voltage corresponding to the magnetic coupling state is output. Therefore, when the upper end shaft 1a is rotated and the torsion bar 1b is twisted, the facing area between the tooth portion 6a of the torque detection ring 6 and the tooth portion 7a of the torque detection ring 7 changes, and the impedance of the torque detection coil L ₂ changes. The torque acting on the torsion bar 1b is detected by the voltage that changes and is output according to the change.

FIG. 2 is a block diagram showing a circuit configuration of a conventional torque sensor. The voltage stabilizing circuit 9 that outputs a DC voltage is grounded via a series circuit of resistors r ₁ and r ₂ that form a voltage dividing circuit 10. The connection 10a between the resistors r ₁ and r ₂ is connected to the voltage input terminal 11a of the oscillator circuit 11. The voltage of the connection portion 10a is selected to determine the voltage value of the DC voltage included in the oscillation voltage output from the voltage output terminal 11b of the oscillation circuit 11. The voltage output terminal 11b for outputting the oscillation voltage of the oscillation circuit 11 is grounded via the series circuit of the resistance R ₁ and the temperature compensation coil L ₁ which compose the temperature compensation circuit 12, and the torque detection circuit 13 is also provided. Is connected to the ground via a series circuit of a resistor R ₂ and a torque detection coil L ₂ that form

A voltage V ₁ according to a change in ambient temperature is output from a connecting portion 12c between the resistance R ₁ of the temperature compensating circuit 12 and the temperature compensating coil L ₁ , and the torque detecting circuit 13 has a voltage V ₁ . Connection part 13c between resistance R ₂ and torque detection coil L ₂
A voltage V ₂ corresponding to the torque applied to the steered wheels and the change in the ambient temperature is output. Therefore, the torque can be detected by the difference between the voltages V ₁ and V ₂ without being affected by the ambient temperature.

[0011]

The resistors R ₁ and R ₂ used in the temperature compensation circuit 12 and the torque detection circuit 13 are the temperature compensation coil L ₁ and the torque detection coil L, respectively.
It is connected in series to detect the impedance change of ₂ as a voltage change. Further, in order to suppress the direct current and reduce the load on the oscillation circuit 11, the resistors R ₁ and R ₂ are made larger than the impedances of the temperature compensation coil L ₁ and the torque detection coil L ₂ . Therefore, there is a problem that the oscillation current from the oscillation circuit 11 decreases and the output voltage from the torque detection coil L ₂ decreases, so that the torque cannot be detected with high sensitivity.

In view of the above problems, it is an object of the present invention to provide a torque sensor capable of detecting torque with high sensitivity without increasing the load on the oscillation circuit.

[0013]

A torque sensor according to the present invention applies an oscillating voltage including a DC voltage to a torque detection coil, and a voltage output from the torque detection coil based on impedance change of the torque detection coil. In a torque sensor that detects a torque, an oscillation voltage including the DC voltage is applied to one end of a series circuit formed by connecting the torque detection coil and a temperature compensation coil that temperature-compensates the detected torque in series. A DC voltage equal to the DC voltage is applied to the other end to prevent a DC current from flowing through the series circuit.

[0014]

When the oscillation voltage including the DC voltage is applied to one end of the series circuit of the temperature compensation coil and the torque detection coil, and the DC voltage equal to the DC voltage included in the oscillation voltage is applied to the other end, There is no DC voltage difference between the other side ends,
No DC current flows through the temperature compensation coil and the torque detection coil. When an oscillating voltage is applied to one end of the series circuit of the temperature compensating coil and the torque detecting coil, a large oscillating current flows through the torque detecting coil according to the impedance change of the torque detecting coil, and The voltage at the connection changes significantly.

Therefore, the DC current flowing due to the DC voltage contained in the oscillation voltage is blocked, and the load on the oscillation circuit does not increase. Further, a large oscillating current flows through the torque detection coil, and the torque can be detected with high sensitivity.

[0016]

The present invention will be described in detail below with reference to the drawings showing the embodiments thereof. FIG. 3 is a block diagram showing the circuit configuration of the torque sensor according to the present invention. The voltage output terminal 9a of the voltage stabilizing circuit 9 that outputs a DC voltage is grounded via a series circuit of resistors r ₁ and r ₂ that form the voltage dividing circuit 10,
The connecting portion 10a between the resistors r ₁ and r ₂ is grounded via a capacitor C that lowers the impedance with respect to the oscillation voltage described later. The torque detection circuit 17 includes a series circuit of a temperature compensation coil L ₁ and a torque detection coil L ₂ , and a resistor R.
₁ and a series circuit of a resistor R ₂ are connected in parallel.

The connecting portion 10a of the voltage dividing circuit 10 is connected to the voltage input terminal 11a of the oscillation circuit 11 and the connecting portion 17a of the torque detecting coil L ₂ and the resistor R ₂ in the torque detecting circuit 17. The voltage output terminal 11b of the oscillation circuit 11 is connected to the temperature compensation coil L ₁ and the resistor R _{1 in} the torque detection circuit 17.
It is connected to 17b. The voltage of the connection portion 10a of the voltage dividing circuit 10 is selected so as to determine the voltage value of the DC voltage of the oscillation voltage output from the voltage output terminal 11b of the oscillation circuit 11.

An AC voltage V _T corresponding to the torque to be detected is output from the connecting portion 17c of the temperature compensating coil L ₁ and the torque detecting coil L ₂ , and the oscillation voltage is divided from the connecting portion 17d of the resistors R ₁ and R _2. The compressed AC reference voltage V _S is output.

Next, the torque detecting operation of the torque sensor thus configured will be described. The output voltage of the voltage stabilizing circuit 9 is divided by the resistors r ₁ and r _{2 of the} voltage dividing circuit 10, and by the voltage of the connecting portion 10a divided by the resistors r ₁ and r ₂ ,
The voltage value of the DC voltage included in the oscillation voltage output from the voltage output terminal 11b of the oscillation circuit 11 is determined. The oscillation voltage including the DC voltage output from the oscillation circuit 11 is the temperature compensation coil L.
₁ is provided to the connection portion 17b between the resistor R ₁ and the connection portion 17a between the torque detection coil L ₂ and the resistance R _2, and the connection portion 10b is provided.
A DC voltage equal to the DC voltage contained in the oscillation voltage is given from a. As a result, the same DC voltage is applied to the connection portions 17a and 17b in the torque detection circuit 17, and a series circuit of the temperature compensation coil L ₁ and the torque detection coil L ₂ and a series circuit of the resistance R ₁ and the resistance R ₂ are provided. No direct current flows through the circuit, which reduces the load on the oscillator circuit 11.

On the other hand, in the temperature compensation coil L ₁ and the torque detection coil L ₂ to which the oscillating voltage from the oscillating circuit 11 is applied, an AC voltage is generated by the oscillating voltage. Therefore, if the impedance of the torque detecting coil L ₂ changes according to the twist of the torsion bar 1b shown in FIG. 1, the AC voltage V _T of the connecting portion 17c between the temperature compensating coil L ₁ and the torque detecting coil L ₂ changes. Then, the torque applied to the torsion bar 1b can be detected by the AC voltage V _T. Further, a reference voltage V _S obtained by dividing the oscillation voltage is obtained at the connecting portion 17d between the resistors R ₁ and R ₂ .

Therefore, the AC voltage V _T and the reference voltage V _S
By comparing with, the twisting direction of the torsion bar 1b can be detected. That is, the rotation of the torsion bar in one direction can be detected when V _T > V _S , and the rotation of the torsion bar in the other direction can be detected when V _T <V _S. When the ambient temperature changes, the temperature compensation coil L ₁
Since the change ratio of the impedance of the torque detection coil L ₂ is equal to that of the torque detection coil L ₂ , the AC voltage V _T is temperature-compensated, and the torque applied to the torsion bar 1b is not affected by the temperature change of the ambient temperature. It can always be detected accurately.

[0022]

As described in detail above, in the torque sensor of the present invention, the DC voltage of the same voltage is applied to each end of the series circuit of the temperature compensation coil and the torque detection coil. The direct current does not flow from the oscillation circuit to the series circuit of, and the load on the oscillation circuit can be reduced. Further, since no resistance is interposed in the series circuit of the temperature compensation coil and the torque detection coil, a large current based on the oscillation voltage flows in the torque detection coil, and a high AC voltage is generated in the torque detection coil. The torque can be detected with high sensitivity. Therefore, the present invention exerts an excellent effect of providing a torque sensor that can detect torque with high sensitivity, with a small load on the oscillation circuit.

[Brief description of drawings]

FIG. 1 is a half cross-sectional view showing a configuration of a main part of a torque sensor.

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

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

[Explanation of symbols]

9 Voltage stabilization circuit 10 Voltage dividing circuit 11 Oscillation circuit 17 Torque detection circuit L ₁ Temperature compensation coil L ₂ Torque detection coil R ₁ , R ₂ resistance

Claims (1)

[Claims] 1. A torque sensor for applying an oscillating voltage including a DC voltage to a torque detecting coil and detecting torque based on a voltage output from the torque detecting coil based on a change in impedance of the torque detecting coil. And a temperature-compensating coil for temperature-compensating the detected torque are connected in series, one end of the series circuit is provided with an oscillating voltage containing the DC voltage, and the other end is supplied with a DC voltage equal to the DC voltage. A torque sensor characterized by being configured to apply a voltage to prevent a direct current from flowing through the series circuit.