JPH06258156A - Strain detector and strain detecting unit - Google Patents

Abstract

PURPOSE:To make a load, which is changed with temperature hard to be applied to a magnetic converging layer and to prevent the erroneous output caused by the temperature by arranging a member for alleviating pressure at the edge of the magnetic converging layer in the axial direction. CONSTITUTION:A magnetic converging layer 12A is constituted in the shape smaller than the size Y of a bobbin 8. A gap Z between the converging layer 12A and the flange part of a shield 13 is filled with soft bonding agent 17 such as silicon sealing agent. Thus, the converging layer 12A is fixed. As the bonding agent, material, which is softened by the temperature rising, is preferable. Since the converging layer is softly fixed with the bonding agent 17, which inserted into the gap Z, the load in the axial direction caused by the temperature change is not applied in the entire range of temper in use, and the erroneous output caused by the temperature can be prevented. Even if vibration is applied, the vibration is absorbed the bonding agent. Thus, the erroneous output caused by the vibration can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strain detecting device, and more particularly to a strain detecting device for detecting strain when an external force is applied to a passive shaft such as a rotary shaft.

[0002]

2. Description of the Related Art For example, a conventional strain detecting device of this type proposed by Japanese Patent Application No. 3-216838 is shown in FIGS.
Will be explained. In the figure, 1 is a passive shaft consisting of a rotary shaft, 2 is a central axis of the passive shaft 1, and 3a and 3b are the passive shaft 1.
Is a bearing that rotatably supports. On the outer peripheral surface of the passive shaft 1, first and second magnetic layers 4 and 5 made of a highly magnetically permeable material are fixed at intervals in the axial direction. The first magnetic layer 4 is formed in a plurality of elongated lines in the +45 degree direction with respect to the central axis 2, and the second magnetic layer 5 is elongated in a −45 degree direction with respect to the central axis 2. Further, a cylindrical bobbin 8 made of engineering plastic in which a shield A6 and a shield B7 are insert-molded is arranged on the outer circumference of each magnetic layer 4, 5, and the bobbin 8 is wound with detection coils 9, 10. The shields A, B6, 7 are provided with notches 6a, 7a for allowing the resin to flow during insert molding and for passing the coil leads.

The coil ends of the detection coils 9 and 10 are connected to a lead wire 11 and led to a detection circuit (not shown).
A magnetic flux concentrating layer 12 is provided around the bobbin 8 around which the detection coils 9 and 10 are wound, and a cylindrical shield C1 is provided outside the magnetic flux concentrating layer 12.
3 are arranged, and these are integrally housed in the cylindrical case 14. The bearing 3 a is press-fitted in close contact with the step portion 1 a provided on the passive shaft 1, and the bearing 3 b is press-fitted in the outer case 15. The case 14 accommodating the detection coils 9 and 10 is preloaded by the wave washer 16 serving as a spring member so that the bobbin 8 closely contacts the bearing 3a in order to reduce the relative position error with the magnetic layers 4 and 5. It is housed in the outer case 15.

In the above structure, when external torque is applied to the passive shaft 1 and a tensile force is generated in one of the magnetic layers 4 and 5, a compressive force is generated in the other and distortion occurs. When this strain occurs, the magnetic permeability changes, and the magnetic permeability changes in the opposite direction depending on the tensile force and the compressive force. The detection coils 9 and 10 detect a change in magnetic permeability as a change in magnetic impedance, and the detection circuit receives the outputs of the detection coils 9 and 10 and outputs a detection voltage according to the distortion amount of the passive shaft 1. It has become. Regarding the magnetic change when a current flows through the detection coils 9 and 10, for example, see Japanese Patent Laid-Open No.
Since it is described in detail in Japanese Laid-Open Patent Publication No. 52535/1990, description thereof will be omitted here.

[0005]

Since the conventional strain detecting device is constructed as described above, each component expands due to heat when the temperature rises. However, the bobbin 8 made of engineering plastic is made of aluminum. Since the outer case 15 thus formed has a smaller coefficient of thermal expansion, the distance X between the bobbin 8 in which the wave washer 16 is incorporated and the outer case 15 shown in FIG. The load on the wave washer 16 increases. Since the magnetic flux concentrating layer 12 is pressed against the bobbin 8 by the wave washer 16 via the case 14 and the shield C13 so that the position does not change due to vibration, the pressing force increases as the temperature rises. If a soft magnetic material such as ferrite is used for the magnetic flux concentrating layer 12 (material that allows easy passage of magnetism and is hard to magnetize), its physical properties change depending on the load, so that the inductance of the coil can be reduced without applying torque to the passive shaft 1. There was a problem that the output changed without changing differentially.

The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to obtain a strain detecting device in which an output does not fluctuate with temperature by making it difficult to apply a load that changes with temperature to a magnetic converging layer. To aim.

[0007]

DISCLOSURE OF THE INVENTION A strain detecting device and a unit according to the present invention are provided with a member for relieving pressure on an axial end face of a magnetic flux concentrating layer.

[0008]

Since the strain detecting device and the unit according to the present invention are configured as described above, it is difficult to apply axial pressure to the magnetic converging layer over the operating temperature range, and there is no fluctuation in output due to temperature.

[0009]

【Example】

Example 1. One embodiment of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view in the axial direction, and the same or corresponding parts as those of the conventional one are designated by the same reference numerals and the description thereof will be omitted.
In the figure, 12A is a magnetic flux concentrating layer, which is the dimension Y of the bobbin 8.
Is set smaller than. 17 is the magnetic converging layer 12A
Is a member for fixing pressure to alleviate the pressure in the axial direction. A soft adhesive such as a silicone sealant is preferably used as the member 17, and an adhesive that softens as the temperature rises is particularly preferable. This material 17 is inserted in the gap Z between the collar portion 13a of the shield C13.

As described above, the magnetic flux concentrating layer 12A has the shield C.
There is a gap Z between the collar portion 13a of 13 and this gap Z
Since it is softly fixed by the member (adhesive) 17 inserted into the magnetic converging layer 12, no axial load is applied to the magnetic flux concentrating layer 12A over the operating temperature range, and there is no output fluctuation due to temperature.

Embodiment 2. In the first embodiment, the magnetic flux concentrating layer 1
Although a silicone sealant is used for fixing 2A, an epoxy adhesive or urethane adhesive may be used as long as it is a soft adhesive that does not apply a load to the magnetic flux concentrating layer 12A due to temperature.

[0012]

As described above, according to the present invention, since the load of the wave washer is not applied to the magnetic flux concentrating layer and the magnetic washer is held softly, an erroneous output due to temperature or vibration does not occur. can get.

[Brief description of drawings]

FIG. 1 is an axial sectional view showing an embodiment of the present invention.

FIG. 2 is an axial sectional view showing a conventional strain detection device.

3 is a perspective view showing each shield of FIG. 2. FIG.

[Explanation of symbols]

 1 Passive Axis 2 Center Axis 4,5 Magnetic Layer 6,7,13 Shield A to C 8 Bobbin 9,10 Detection Coil 12A Magnetic Converging Layer 14 Case 15 Outer Case 16 Wave Washer 17 Adhesive

Claims (4)

[Claims] 1. A passive shaft which receives an external force, a magnetic layer fixed on the outer peripheral surface of the passive shaft, and the magnetic force which is disposed on the outer periphery of the magnetic layer and is caused by an external force applied to the passive shaft. A detection coil for detecting a change in magnetic permeability of the layer,
It has a magnetic converging layer arranged so as to surround the detection coil, a shield arranged so as to surround the magnetic converging layer, and a case in which these are housed in one. In the strain detecting device to which a pressure is applied in the axial direction, a member for relaxing the pressure in the axial direction is arranged on an end face in the axial direction of the magnetic flux concentrating layer. 2. The strain detecting device according to claim 1, wherein a soft adhesive is provided on the axial end surface of the magnetic flux concentrating layer. 3. A bobbin, a detection coil wound around the outer periphery of the bobbin, a magnetic focusing layer arranged so as to surround the detection coil, a shield arranged so as to surround the magnetic focusing layer, and these. In a strain detection unit having a case that accommodates one of them, a member that alleviates the pressure applied in the axial direction of the magnetic converging layer is arranged on the axial end surface of the magnetic converging layer. Characteristic strain detection unit. 4. The strain detecting unit according to claim 3, wherein a soft adhesive is provided on the axial end surface of the magnetic flux concentrating layer.