JPH07229800A - Torque sensor - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain a torque sensor in which the coil used is small, the air gap is small, and the magnetic characteristics of the shield case do not change even when the sensor is thermally changed. [Structure] The coils 13, 14 arranged around the magnetic anisotropic portion 12 formed on the torque detection shaft 11 and capable of picking up a torque detection signal are constituted by bobbinless coils having no bobbin on the inner peripheral side. .

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 a magnetostrictive torque sensor capable of non-contact torque detection.

[0002]

2. Description of the Related Art As a magnetostrictive torque sensor capable of non-contact torque detection, a magnetic anisotropic portion 2 is formed on the outer circumference of a torque detection shaft 1 as shown in FIG. It is known that the exciting coil 3 and the detecting coil 4 are concentrically arranged around the portion 2. A non-contact type torque sensor represented by this magnetostrictive torque sensor can detect static torque and dynamic torque, but since it is a non-contact type, it is particularly suitable for dynamic torque detection applications. This is advantageous in terms of reliability.

The exciting coil 3 and the detecting coil 4 in this magnetostrictive torque sensor are constructed by winding a copper wire around the outer circumference of a resin bobbin 5 such as PPS or Ultem. Then, the coils 3 and 4 in which the bobbin 5 is wound in this manner are housed in the shield case 6 to improve the detection output.

[0004]

However, the coils 3 and 4 with such a bobbin 5 have a large width and a large diameter, and there is a drawback that a space is required for their installation. Further, in the non-contact type torque sensor, it is unavoidable that the air gap 7 exists between the shaft 1 and the coil, and this air gap 7 causes a decrease in accuracy. However, in the coil with the bobbin 5, there is a problem that the air gap 7 is substantially increased by the thickness of the bobbin 5 on the inner peripheral side of the coil, and the detection output is reduced.

Further, since the bobbin 5 is made of resin,
The thermal expansion coefficient is greatly different from that of the metal shield case 6. Therefore, when the sensor receives a thermal change such as when the temperature is high, the bobbin 5 expands and exerts a pressing force on the shield case 6. However, since the shield case 6 is made of a magnetostrictive material, there is a problem in that the magnetic characteristics change when stress is applied, which causes an output error.

Therefore, the present invention solves these problems,
The object is to be small in size, have a small air gap, and prevent the magnetic characteristics of the shield case from changing even when the sensor is thermally changed.

[0007]

In order to achieve this object, the present invention can form a magnetic anisotropic portion on the outer circumference of a torque detection shaft and pick up a torque detection signal around the magnetic anisotropic portion. A coil is arranged, and this coil is configured by a bobbinless coil having no bobbin on the inner peripheral side.

[0008]

With this structure, since the bobbin does not exist, the coil width and diameter are reduced. Further, since there is no bobbin, the air gap becomes smaller accordingly. In addition, even if the sensor receives a thermal change, the bobbin does not expand and press the shield case, so the magnetic characteristics of the shield case do not change, and the output error accompanying it does not occur. Is also avoided.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, 11 is a torque detecting shaft, and a pair of magnetic anisotropic portions 12 are formed on the outer circumference thereof. An exciting coil 13 on the inner peripheral side and a detecting coil 14 on the outer peripheral side are concentrically arranged around the magnetic anisotropic portion 12. As shown in FIG. 2, these coils are composed of bobbinless coils, that is, air-core coils composed only of multiple windings. Then, the excitation coil 13 and the detection coil 14 are housed inside a cylindrical shield case 16, and the shield case 16 and the coil 13,
A gap 17 is filled with a filler 17 such as an adhesive. The shield case 16 is concentrically supported inside a casing 19 forming a sensor via a magnetic insulating member 18 having an L-shaped cross section. The torque detection shaft 11 is arranged so as to penetrate the casing 19, and the casing 19
It is concentrically and rotatably supported by a pair of bearings 20 inside. An electronic circuit 21 for signal processing is provided in the casing 19, and the electronic circuit 21 is electrically connected to the coils 13 and 14 by a lead wire 22. A socket 23 for electrically connecting the electronic circuit 21 to the outside of the system is provided on the outer surface of the casing 19.

3 and 4 show the details of the connection between the coils 13 and 14 and the lead wire 22. As shown in FIG. As shown in the drawing, in the exciting coil 13 and the detection coil 14 which are configured by a bobbinless coil having no bobbin on the inner peripheral side, this connection portion is
A resin-made terminal member 24 having an L-shaped cross section is arranged so as to straddle the coils, and is integrated with these coils 13 and 14 by adhesion or the like.

More specifically, the coils 13 and 14 are wound so that the windings are super-super-aligned windings, and are formed so that the dimensional accuracy of the inner diameter and the roundness are at a fine level. An insulating layer 26 made of insulating paper or the like is formed between the inner peripheral side excitation coil 13 and the outer peripheral side detection coil 14. The terminal member 24 is formed with four accommodating recesses 28 for accommodating a total of four lead wires 22 corresponding to the ends of the windings 27 of the exciting coil 13 and the detecting coil 14, respectively. . These lead wires 22 are fixed to the terminal member 24 by bonding or the like with the conductor wire exposed portion 29 at the tip thereof being arranged in the housing recess 28, and the end portion 27 of the winding is wound around the conductor wire exposed portion 29. In addition, by being soldered, the electrical connection between the two is achieved. As shown in FIG. 1, by fitting the terminal member 25 into a predetermined position inside the shield case 16, the coils 13 and 14 are positioned in the axial direction.

According to this structure, since the bobbin is not provided, the width and diameter of the coil can be reduced, and a small torque sensor can be constructed. Specifically, the width of the coil space can be reduced by 2 mm and the outer diameter thereof can be reduced by 6 mm as compared with a bobbin.

Since there is no bobbin, the inner circumferences of the coils 13 and 14 can be made as close as possible to the outer circumference of the magnetic anisotropic portion 12, and the air gap 30 can be reduced accordingly. Specifically, the air gap can be reduced by a maximum of 1 mm, and the detection coil 14 can be correspondingly reduced.
The amount of current generated in the device increases, and the detection output can be improved by 37% as compared with the device having the bobbin. In addition, the general bobbinless coil has a poorer inner diameter dimensional accuracy than the bobbin-equipped coil, which causes an output error due to the rotation of the shaft because the air gap is not uniform. Since the roundness is set to the precision level, the air gap 30 can be uniformly formed in the circumferential direction, and the occurrence of output error due to the rotation of the shaft 11 can be prevented.

Even if the sensor is subjected to a thermal change, no stress is generated in the shield case 17 due to the pressure due to the expansion of the bobbin, and the magnetic characteristics of the shield case 17 may change to cause an output error. Absent. Therefore, more specifically, the temperature output error is 0.15% compared to that with a bobbin.
It can be reduced by% FS / 10 ° C.

Since the windings of the coils 13 and 14 are ultra-super-aligned windings, the variation in impedance of the coils 13 and 14 is 2 to 3% or less, and the variation in sensitivity of the sensor can be reduced. That is, when the winding is randomly wound like a general bobbinless coil, there is a problem that the magnetic flux distribution along the axial direction of the coil has a mountain shape and the variation in the output error of the sensor increases. According to this, such a problem can be solved. Further, the ultra-super-aligned winding has an advantage that the outermost diameter of the coil can be made smaller than that of the random winding.

In the magnetostrictive torque sensor, the excitation coil 13 and the detection coil 14 are generally arranged inside and outside as shown in the figure in order to amplify the detection signal. Mutual induction may occur between the coils and cause an output error. On the other hand, as described above, the insulating layer is provided between the inner excitation coil 13 and the outer detection coil 14.
By forming 26, mutual induction between coils can be prevented,
It is possible to improve sensor performance such as hysteresis, linearity and reproducibility. Therefore, the insulating layer 26 preferably has a thickness of 0.5 mm or more.

A terminal member is provided at a portion of the coil in the circumferential direction.
Since 25 is integrally provided and the end portion 27 of the winding and the exposed wire portion 29 of the lead wire 22 are electrically connected, the position of this connection portion becomes stable, which facilitates the soldering process,
In addition, the tensile strength of the connecting portion is increased. In a general bobbinless coil, such a configuration is not adopted, it is difficult to connect the coil winding and the lead wire, and there is a problem that reliability is poor due to low tensile strength. By providing the terminal member 25, such a problem can be solved. Moreover, this tensile strength can be made even higher than that of the pin-coupling configuration normally applied to coils having bobbins. Further, as described above, the terminal member 25 can be used for positioning the coils 13 and 14 in the axial direction by fitting the terminal member 25 at a predetermined position in the shield case 16.

As described above, by applying the bobbinless coil to the torque sensor, and by applying various measures as described above in applying the torque sensor, it is possible to achieve the sensor performance equal to or higher than that when the coil having the bobbin is used. You can

The shielding material 16 is filled with the filling material 17.
When fixing the coils 13 and 14 therein, for example, a sleeve having a thickness corresponding to the air gap 30 is externally fitted to the shaft 11, and further the coils 13 and 14 and the shield case 16 are externally fitted to this sleeve. Then, the gap between the coils 13 and 14 and the shield case 16 is filled with the filling material 17 to be solidified, and then the sleeve is removed.
It is possible to position and fix 13 and 14 concentrically.

[0020]

As described above, according to the present invention, the coil which is arranged around the magnetic anisotropy portion formed on the torque detection shaft and which can pick up the torque detection signal, and the bobbin on the inner peripheral side are provided. Since it is composed of a bobbinless coil, the width and diameter of the coil can be made smaller, the air gap can be made smaller, and the detection output can be made larger. Does not expand and presses the shield case. Therefore, it is possible to prevent the magnetic characteristics of the shield case from changing and to prevent the output error from occurring.

[Brief description of drawings]

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

FIG. 2 is a partially cutaway perspective view of a coil and a shield case in FIG.

FIG. 3 is a detailed enlarged view of a terminal member and its surroundings in FIG.

FIG. 4 is a side view of the portion shown in FIG.

FIG. 5 is a diagram showing a conventional torque sensor coil together with a relevant part of a corresponding torque detection shaft.

[Explanation of symbols]

 11 Torque detection axis 12 Magnetic anisotropy section 13 Excitation coil 14 Detection coil 16 Shield case 17 Filling material 25 Terminal member

Claims (4)

[Claims] 1. A magnetic anisotropy portion is formed on the outer circumference of a torque detection shaft, and a coil capable of picking up a torque detection signal is arranged around the magnetic anisotropy portion. A torque sensor comprising a bobbinless coil having no. 2. The torque sensor according to claim 1, wherein the windings of the coil are aligned windings. 3. The coil has an inner peripheral side excitation coil and an outer peripheral side detection coil, and an insulating layer is formed between the excitation coil and the detection coil. Torque sensor. 4. The coil integrally has a terminal member used for electrically connecting an end portion of the coil wire and a lead wire to the outside.
The torque sensor according to any one of items 1 to 7.