JPH05142069A - Distortion detector - Google Patents

Abstract

PURPOSE:To prevent the influences of the external magnetic field to a detecting coil through a driven shaft by using a non-magnetic, non-conductive material for the driven shaft. CONSTITUTION:When the torque is impressed to a driven shaft 1 from outside, a tensile force is generated at one of magnetic layers 3, 4 made of a material of high magnetic permeability, and a compression force is generated at the other layer, resulting in a distortion of the shaft. As the distortion is generated, the magnetic permeability is changed. The magnetic permeability is changed in opposite directions between when the tensile force is generated and when the compression force is generated. Detecting coils 10, 11 detect the change of the magnetic permeability as the change of the magnetic impedance, and the outputs of the detecting coils 10, 11 are input to a detecting circuit 14. The detecting circuit 14 generates a detecting voltage V corresponding to the amount of the distortion of the driven shaft 1. Since the driven shaft l is formed of a non-magnetic, non conductive material, the external magnetic field never influences the detecting coils 10, 11 through the driven shaft 1. Accordingly, the output is not fluctuated by the external magnetic field.

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,
The present invention relates to a strain detection device for detecting strain when an external force is applied to a passive shaft such as a rotating shaft.

[0002]

2. Description of the Related Art For example, FIG. 2 is a block diagram of a conventional magnetostrictive torque sensor. In the figure, 1 is a passive shaft formed of a rotary shaft, 2 is a central shaft of the passive shaft 1, and 31 and 32 are bearings that rotatably instruct the passive shaft 1. First and second magnetic layers 3 and 4 made of a highly magnetically permeable material are fixed on the outer peripheral surface of the passive shaft 1 at intervals in the axial direction. First magnetic layer 3
Are elongated in the +45 degree direction with respect to the central axis 2, and the second magnetic layer 4 is formed with a plurality of elongated strips in the −45 degree direction with respect to the central axis 2.

A cylindrical coil bobbin 5 is arranged coaxially with the passive shaft 1 on the outer circumference of each of the magnetic layers 3 and 4 with a gap therebetween. The outer circumference of the coil bobbin 5 corresponds to the first and second magnetic layers 3 and 4, and the first and second detection coils 10 and 1 are provided.
1 is wound, and each of the detection coils 10 and 11 includes a detection circuit 1
4 is connected. Reference numeral 33a denotes a first magnetic flux concentrating layer which is wound around or fitted around the first detection coil 10.
Reference numeral 3b is a second magnetic flux concentrating layer wound around or fitted around the second detection coil 11.

The magnetic flux concentrating layers 33a and 33b are made of an amorphous alloy or a soft magnetic material having a high magnetic permeability such as a silicon steel plate. Reference numerals 35a and 35b are non-magnetic, high-conductivity metal shield layers provided on the outer periphery of the magnetic flux concentrating layers 33a and 33b.
The metal shield layers 35a and 35b utilize a skin effect in which the penetration depth of the magnetic flux is reduced, and a nonmagnetic high conductivity material is used so that the magnetic resistance of the magnetic circuit and the leakage of the magnetic flux are reduced.

In the above structure, when a torque T is applied to the passive shaft 1 from the outside, a tensile force is generated in one of the magnetic layers 3 and 4, a compressive force is generated in the other, and strain is generated. 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 10 and 11 detect a change in magnetic permeability as a change in magnetic impedance, and the detection circuit 14 detects each change in the detection coil 1.
The outputs 0 and 11 are input, and the detection voltage V according to the distortion amount of the passive shaft 1 is output.

[0006]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention
With the above configuration, when the passive shaft 1 is a magnetic or conductive material, an external magnetic field, for example, geomagnetism, magnetism of an electric motor, a clutch or the like arranged near the strain detecting device, is detected through the passive shaft 1. The detection coils 10 and 11 are affected by the magnetic field generated when electricity flows through the passive shaft 1 while being guided and influenced by the coils 10 and 11, and the output of the strain detection device shows a value different from the applied torque. There was a problem.

The present invention has been made to solve the above-mentioned problems, and prevents an external magnetic field from being guided to the detection coil through the passive shaft, and is generated by the current flowing through the passive shaft. An object of the present invention is to obtain a strain detection device that is not affected by a magnetic field.

[0008]

DISCLOSURE OF THE INVENTION A strain detecting apparatus according to the present invention comprises a passive shaft that receives an external force and a soft magnetic material having a high magnetic permeability and a predetermined magnetic constant fixed to the outer peripheral surface of the passive shaft. A strain detecting device comprising a magnetic layer and a detecting coil which is disposed with a gap on the outer periphery of the magnetic layer and detects a change in magnetic permeability of the magnetic layer caused by an external force applied to the passive shaft, It uses a non-magnetic and non-conductive material for the passive shaft.

[0009]

In the strain detecting device according to the present invention, since the passive shaft is made of a non-magnetic and non-conductive material, the detection coil is not affected by the external magnetic field and the output fluctuation due to the external magnetic field does not occur.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is a passive shaft made of a non-magnetic and non-conductive material, 2 is a central shaft of the passive shaft 1, and 31 and 32 are bearings that rotatably support the passive shaft 1. First and second magnetic layers 3 and 4 made of a highly magnetically permeable material are fixed on the outer peripheral surface of the passive shaft 1 at intervals in the axial direction. The first magnetic layer 3 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 4 is elongated in a −45 degree direction with respect to the central axis 2.

A cylindrical coil bobbin 5 is arranged coaxially with the passive shaft 1 on the outer circumference of each magnetic layer 3, 4. First and second detection coils 10 and 11 are wound around the outer circumference of the coil bobbin 5 corresponding to the first and second magnetic layers 3 and 4, and each detection coil is connected to a detection circuit 14. .
33a is wound around the first detection coil 10 or
The fitted first magnetic flux concentrating layer, 33b is the second magnetic flux concentrating layer wound around or fitted around the second detection coil 11. The magnetic flux concentrating layers 33a and 33b are made of an amorphous alloy or a soft magnetic material having a high magnetic permeability such as a silicon steel plate.

35a and 35b are magnetic flux concentrating layers 33a and 33.
It is a non-magnetic high-conductivity metal shield layer provided on the outer periphery of b. The metal shield layers 35a and 35b utilize a skin effect in which the penetration depth of the magnetic flux is reduced, and a non-magnetic high conductivity material is used so that the magnetic resistance of the magnetic circuit and the leakage of the magnetic flux are reduced. Reference numerals 37a and 37b are shaft members respectively coupled to both ends of the passive shaft 1.

In the above structure, when a torque is applied to the passive shaft 1 from the outside, a tensile force is generated in one of the magnetic layers 3 and 4, and a compressive force is generated in the other magnetic layer to cause strain. 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 10 and 11 detect a change in magnetic permeability as a change in magnetic impedance, and the detection circuit 14 detects each of the detection coils 10 and 1.
The output of No. 1 is input, and the detection voltage V according to the amount of distortion of the passive shaft 1 is output, as in the case of the above-described conventional example.

In the construction of the embodiment, the entire passive shaft 1 is made of a non-magnetic and non-conductive material, but only the fixed portions of the magnetic layers 3 and 4 are made of the above material, and the passive shaft 1 is made of the shaft material 37a. , 37b
Shaft member 37 other than the fixed portions of the magnetic layers 3 and 4
The material characteristics of a and 37b can be made into a structure with no problem.

[0015]

As described above, according to the present invention, since the passive axis of the strain sensing device is made of a non-magnetic and non-conductive material, the influence of the external magnetic field on the sensing coil is small and the strain sensing device There is an effect that the output can be made less susceptible to the influence of magnetism.

[Brief description of drawings]

FIG. 1 is a sectional view of a strain detecting device according to an embodiment of the present invention.

FIG. 2 is a sectional view of a conventional strain detection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Passive shaft 3,4 Magnetic layer 5 Bobbin 10,11 Detection coil 31,32 Bearing 33,33a, 33b Magnetic focusing layer 35,35a, 35b Shield

Claims (1)

[Claims] 1. A passive shaft which receives an external force, a magnetic layer fixed on the outer peripheral surface of the passive shaft and made of a soft magnetic material having a high magnetic permeability and a predetermined magnetic constant, and a gap formed on the outer periphery of the magnetic layer. In a strain detecting device comprising a detection coil arranged at a distance and detecting a change in magnetic permeability of the magnetic layer caused by an external force applied to the passive shaft, a non-magnetic, non-conductive material is used for the passive shaft. Distortion detection device characterized by.