JP2001281079A - Torque sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a torque sensor for detecting a torque with precision, over the entire range of core displacement amount, as linear change in a sensor output voltage to the core displacement amount. SOLUTION: A torque sensor is provided where a core 8 moves in the axial direction according to a torque in first and second coils 11 and 12 which are wound coaxially and symmetrically, so that the torque is detected from the inductances of the first and second coils 11 and 12 hanging in an opposite direction to each other. Here, related to the first and second coils 11 and 12, winding diameter of the coils becomes smaller as comes away from the central position of them in the axial direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a torque sensor for detecting a torque based on a change in inductance of a pair of coils.

[0002]

2. Description of the Related Art FIG. 7 schematically shows a cross section of a main part of a conventional torque sensor of this kind. A first coil B 01 and a second coil 02 are coaxially arranged around the axis of a core 05 that is displaced in the axial direction according to the torque.

[0003] The first coil 01 and the second coil 02 have the same cylindrical shape in which the coils are wound with their winding directions reversed. The core 05 is a non-magnetic material such as an aluminum ring, and when no torque is generated, the first and second coils 01,
It is at a neutral position not biased toward one of the middle portions of 02, and when a torque is applied in one direction, the core 05 moves in one of the axial directions.

When a pulse current is applied to the first and second coils 01 and 02 and the magnetic field fluctuates, the core 05 is displaced and, for example, approaches the first coil 01 so that the coil magnetic field of the first coil 01 is obstructed. An eddy current is generated on the surface of the core 05, the magnetic flux density decreases, the magnetic permeability decreases, and the inductance decreases. Conversely, the inductance of the other second coil 02 increases as the core 05 moves away.

Since the induced electromotive force as the sensor output changes in proportion to the inductance, the change in the output voltage with respect to the displacement of the core 05 is as shown in FIG. In the coordinates shown in FIG. 8, the voltage is plotted on the vertical axis, and the core
The amount of displacement of the core 05 toward the first coil 01 is shown, and the leftward direction of the horizontal axis represents the amount of displacement of the core 05 toward the second coil 02.

When the core 05 moves toward the first coil 01, the first sub-voltage VS1 of the first coil 01 decreases, and the second coil 02
Of the second sub-voltage VS2 increases, and conversely, the core 05
When moving to the 02 side, the first sub-voltage VS1 increases and the second sub-voltage VS2 decreases.

A first coil 01 and a second coil 02 as in the prior art
Is formed in a cylindrical shape, the change of the output voltage draws a curve as shown in FIG. 8, and the first and second sub-voltages VS1, VS
As shown in FIG. 9, the final change in the sensor output voltage V obtained by taking the difference of 2 is a curve in which both ends of the S-shape are stretched. Is a curved shape approaching.

[0008]

That is, in the range where the displacement of the core 05 is large, the change in the sensor output voltage V is small, and the displacement of the core, that is, the torque cannot be detected with high accuracy.

[0009] The present invention has been made in view of such a point,
An object of the present invention is to provide a torque sensor capable of accurately detecting torque in the entire range of the core displacement amount by linearly changing the sensor output voltage with respect to the core displacement amount.

[0010]

In order to achieve the above object, according to the first aspect of the present invention, the core is converted into a torque in the first coil and the second coil wound coaxially and symmetrically. A first coil and a second coil which are moved in the axial direction in response to each other and detect torque from inductances of the first coil and the second coil which change in opposite directions; The torque sensor is wound so that the winding diameter of the coil becomes smaller as the distance from the coil increases.

Since the first coil and the second coil are wound so that the winding diameter of the coil decreases as the distance from the center of the first coil and the second coil increases in the axial direction, the magnetic field having a higher magnetic flux density increases as the distance from the center to the axis increases. Has occurred.

Therefore, in the coil in the direction in which the core moves, the inductance and the output voltage decrease due to the influence of the eddy current, but the effect of the eddy current acts greatly even in a large displacement range of the core. The rate of change of the output voltage with respect to the amount can be maintained the same as the vicinity of the center even if the distance from the vicinity of the center is increased, and the output voltage with respect to the amount of core displacement can be linearly changed as a whole.

On the other hand, in the coil in the opposite direction in which the core moves, the inductance increases and the output voltage also increases. However, even in the range where the displacement of the core is large, the influence of the eddy current is small and the output with respect to the displacement of the core is reduced. The rate of change in voltage is the same in the vicinity of the center and in the vicinity of the center, and the output voltage with respect to the core displacement can be linearly changed as a whole.

Since the output voltage of both the first coil and the second coil changes linearly with respect to the amount of core displacement, the torque can be accurately detected over the entire range of the amount of core displacement.

According to a second aspect of the present invention, the core moves in the first coil and the second coil wound coaxially and symmetrically in the axial direction according to the torque and changes in the opposite directions.
In the torque sensor for detecting torque from the inductance of the coil and the second coil, the first coil and the second coil may be wound so that the number of turns of the coil increases as the distance from the center of the two coils increases in the axial direction. This is a characteristic torque sensor.

Since the coil is wound so that the number of turns of the coil increases as the distance from the center of the coil increases in the axial direction, a magnetic field having a higher magnetic flux density increases as the distance from the center increases in the axial direction. Thus, the output voltage of both the first coil and the second coil can be changed linearly with respect to the core displacement, and the torque can be accurately detected in the entire range of the core displacement.

[0017]

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.

The input shaft 3 and the output shaft 4 which are rotatably supported by the housing 2 via bearings 5 and 6 and are coaxially inserted therein are connected 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.

The core 8 is a non-magnetic aluminum ring. Two first coils 11 and second coils 12 for torque detection supported inside the housing 2 are provided on the outer periphery of the cylindrical core 8 that slides in the axial direction via a gap.

The first coil 11 and the second coil 12 are arranged on opposite sides with respect to the axial movement center of the core 8, and the coil diameter becomes smaller as the distance from the center of the core 8 in the axial direction decreases. It is curved and wound.

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 to the first coil 11 side, the magnetic flux density of the first coil 11 decreases due to the eddy current, the permeability decreases, and the inductance decreases.
12, the coil inductance increases.

That is, when a torque for moving the core 8 toward the first coil 11 acts, the inductance L1 of the first coil 11 decreases and the inductance L2 of the second coil 12 decreases.
Increases, and conversely, when a torque for moving the core 8 toward the second coil 12 acts, the inductance L of the first coil 11
1 increases, and the inductance L2 of the second coil 12 decreases.

FIG. 2 is a schematic configuration diagram of an electric circuit of the torque sensor 1 for detecting a torque based on changes in the inductances L1 and L2 of the first coil 11 and the second coil 12. The coils 11 and 12 are suspended at a positive voltage E via a resistor 13 (R1) and a resistor circuit 14 (R2), respectively. The other ends of the coils 11 and 12 are both connected to an oscillation output device 20. .

A voltage signal line 21 extending from a connection between the coil 11 and the resistor 13 is connected to a rectification / smoothing circuit 23, and a voltage signal line 22 extending from a connection between the coil 12 and the resistor 14 is connected to a rectification / smoothing circuit. Connected to 24.

That is, a bridge circuit is formed by the first coil 11, the second coil 12, the resistor 13, and the resistor 14, and an oscillating voltage is input to the bridge circuit, and an output voltage appears as a sine wave amplitude and a rectifying / smoothing circuit 23. , And 24, the first and second sub-voltages VS1 and VS2, which are the rectified and smoothed DC voltages output from the rectifying and smoothing circuits 23 and 24, respectively, are the first coil 11 and the second coil Indicates a voltage proportional to the inductance of 12.

The first and second sub-voltages VS1, VS2 are:
The signal is output to the differential amplifier circuit 25, and the difference between the two is taken as the sensor output voltage V by the differential amplifier circuit 25. FIG. 4 shows changes in the first and second sub-voltages VS1 and VS2 with respect to the displacement amount of the core 8 in this embodiment, and FIG. 5 shows changes in the sensor output voltage V.

As described above, the first coil 11 and the second coil 12 of the torque sensor 1 are wound in a curved manner so that the winding diameter of the coil becomes smaller as the distance from the center between them increases in the axial direction. FIG. 3 schematically shows a cross section. In both the first coil 11 and the second coil 12, the winding diameter of the coil decreases as the distance from the center position increases, and thus the magnetic flux density increases as the distance from the center position increases.

Assuming that the torque is applied in a certain direction and the core 8 moves to the first coil side, the inductance L1 of the first coil 11 decreases as described above, and the first sub-voltage VS1 proportional to the inductance L1 also decreases. However, since the magnetic flux density increases as the distance from the center increases, the rate of change of the output voltage with respect to the amount of core displacement can be maintained at the same level as that near the center even if the distance from the center is greatly affected by the eddy current. As a result, as shown in FIG. 3, the first sub-voltage VS1 decreases linearly with respect to the core displacement amount as a whole. Conversely, the second sub-voltage VS2 increases linearly.

When the core 8 moves to the second coil 12 side, a phenomenon completely opposite to that described above occurs in the first and second coils 11 and 12, so that the first sub-voltage VS1 with respect to the displacement amount of the core 8 is generated.
And the change of the second sub-voltage VS2 is shown as a straight line in which the sign (positive or negative) of the slope is reversed as shown in FIG.

Therefore, the change in the sensor output voltage V, which is the difference between the first sub-voltage VS1 and the second sub-voltage VS2, with respect to the core displacement is a straight line as shown in FIG. Since the sensor output voltage V changes linearly with respect to the core displacement, the torque can be detected with high accuracy even in the vicinity where the core 8 is far away from the center position, as in the vicinity of the center.

In the above embodiment, the first coil 11 and the second coil 12 are wound such that the coil diameter becomes smaller as the distance from the center of the first coil 11 and the second coil 12 in the axial direction decreases, but as shown in FIG. Alternatively, the first coil 21 and the second coil 22 may be wound such that the number of turns of the coil increases as the distance from the center of the two coils increases in the axial direction.

The first coil 21 and the second coil 22 are wound so that the number of turns of the coil increases as the distance from the center position of the first coil 21 and the second coil 22 increases, so that the magnetic flux density increases as the distance from the center position increases in the axial direction. Since a magnetic field is generated, the output voltage can be linearly changed with respect to the displacement of the core 25 in both the first coil 21 and the second coil 22 in the same manner as in the above-described embodiment. Can be accurately detected in the entire range of

[Brief description of the drawings]

FIG. 1 is a side view of a torque sensor according to an embodiment of the present invention.

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

FIG. 3 is a schematic sectional view of a main part of the torque sensor.

FIG. 4 is a diagram showing changes in first and second sub-voltages with respect to a core displacement amount.

FIG. 5 is a diagram illustrating a change in sensor output voltage with respect to a core displacement amount.

FIG. 6 is a schematic sectional view of a main part of a torque sensor according to another embodiment.

FIG. 7 is a schematic sectional view of a main part of a conventional torque sensor.

FIG. 8 is a diagram showing changes in first and second sub-voltages with respect to a core displacement amount of the torque sensor.

FIG. 9 is a diagram showing a change in sensor output voltage with respect to a core displacement amount of the torque sensor.

[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 ... First coil, 12 ... Second
Coil, 13, 14 ... resistance, 21 ... first coil, 22 ... second coil, 25 ... core.

Claims (2)

[Claims] 1. A core moves axially in a first coil and a second coil, which are wound coaxially and symmetrically, according to torque.
In a torque sensor for detecting torque from the inductance of the first coil and the inductance of the second coil that change in opposite directions, the winding diameter of the coil increases as the distance between the first coil and the second coil increases in the axial direction from the center position between the two. A torque sensor which is wound so as to be small. 2. A core moves axially in a first coil and a second coil wound coaxially and symmetrically in accordance with torque.
In a torque sensor for detecting torque from the inductances of the first coil and the second coil that change in opposite directions, the number of turns of the coil increases as the distance between the first coil and the second coil increases in the axial direction from a central position between the two. A torque sensor characterized by being wound so as to increase.