JPH01162121A - Torque detector - Google Patents

Abstract

PURPOSE:To achieve a higher torque detection sensitivity with an improved propagating property of a stress to a magnetic layer from a passive shaft with a thinner adhesive, by bonding a slender magnetic layer on the circumference of the passive shaft through an epoxy based adhesive 20-100mum thick. CONSTITUTION:Magnetic layers 5 and 6 herein used are amorphous magnetostrictive material and an adhesive for bonding the magnetic layers 5 and 6 on a passive shaft 1 employs a thermosetting epoxy based film adhesive 20-100mum thick. With the thickness of the adhesive set at 200-100mum, a stress propagation ratio can be increased and hence, even when the chevron length of the magnetic layers 5 and 6 is, for example, 2mm, a stress propagation ratio exceeding 70% can be obtained to improve a torque detection sensitivity. This also achieves a higher adhesion strength because of a thin adhesive.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a torque detector that non-contactly measures the shaft torque of a passive shaft such as a rotating shaft.

[Conventional technology]

FIG. 1 shows the configuration of a conventional torque detector, in which 2 is a passive shaft consisting of a rotating shaft, 2 is a central axis of the passive shaft 1, and 3.4 is a bearing that rotatably supports the passive shaft 1. First and second magnetic layers 5.6 made of a highly magnetostrictive material are fixed to the outer periphery of the passive shaft 1. The first magnetic layer 5 is formed in a plurality of elongated strips at an angle of +45 degrees with respect to the central axis 2, and the second magnetic layer 6 is formed in a plurality of elongated strips at an angle of 145 degrees with respect to the central axis 2. Moreover, each magnetic layer 5
A cylindrical coil pobbin 7 is disposed coaxially with the driven shaft 1 on the outer periphery of the shaft 1 with a gap therebetween. First and second detection coils 8°9 are wound around the outer periphery of the coil bobbin 7.
Each detection coil 8, 9 is connected to a detection circuit 14. or,
Reference numerals 10 and 11 denote first and second magnetic convergence layers made of a high magnetic permeability material and provided around the detection coil 8.9. f6
When attaching the i-type layers 5 and 6 to the passive shaft 1, apply adhesive to the back side of the thin ribbon of high magnetostrictive material, heat and harden the adhesive while applying pressure to the thin ribbon, and then A chevron pattern magnetic layer 5.6 is selectively removed by etching.
get.

Next, the operation will be explained. When torque is applied to the passive shaft 1 from the outside, stress propagates from the passive shaft 1 to the magnetic layer 5.6 through the adhesive, creating a tensile force on one side of the magnetic layer 5.6 and a compressive force on the other. occurs, causing distortion. When this strain occurs, the magnetic permeability of the magnetic layer 5.6 changes, and the magnetic permeability changes in opposite directions depending on whether the tensile force is applied or the compressive force is applied.

The detection coils 8 and 9 are supplied with current and detect changes in magnetic permeability as changes in magnetic impedance.
A detection voltage V is output according to the amount of distortion.

[Problem that the invention seeks to solve]

However, in the conventional torque detector described above, no consideration was given to the thickness of the adhesive. As a result, the thickness of the adhesive became thicker, and the torque applied to the passive shaft 1 was absorbed in the adhesive, resulting in poor propagation to the magnetic layer 5.6, resulting in a decrease in torque detection sensitivity. Furthermore, as the thickness of the adhesive increased, the adhesive strength also decreased, resulting in a decrease in reliability.

The second invention was made to solve the above problems, and aims to provide a torque detector with good torque detection sensitivity, high adhesive strength of the magnetic layer, and high reliability. purpose.

[Means for solving problems]

In the torque detector according to the present invention, a chevron pattern magnetic layer is bonded to the outer periphery of a passive shaft using an epoxy adhesive having a thickness of 20 μm or more and 100 μm or less.

[For production]

The magnetic layer in this invention has a thickness of 100 mm on the outer periphery of the passive shaft.
- Bonded via the following epoxy adhesive, reducing torque absorption in the adhesive and increasing adhesive strength.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. The structure of the torque detector according to this embodiment is the same as that shown in FIG. The thickness of the adhesive that adheres to 1 is 10
0. A thermosetting epoxy film adhesive having a rating of 111 or less (for example, product name F147, manufactured by 3M Company) is used. The operation as a torque detector is the same as the conventional one.

Figure 2 shows the adhesive thickness [μ] and its shear strength (MPa).
), the shear strength is highest when the thickness of the adhesive is about 50 mm, and if the thickness is in the range of 20 pm or more and 100 μ or less, good shear strength is obtained, and therefore good adhesive strength is obtained. can get.

In addition, the Young's modulus of the passive shaft 1, the coefficient of linear expansion β5, and the thickness 1
, the rigidity Gc of the adhesive, the thickness h, the individual lengths of the magnetic layer 5°6, that is, the Chevron length, the Young's modulus E2, the linear expansion coefficient β and the thickness 1. Then, the Young's modulus El, E! of the passive shaft 1 and the magnetic layer 5.6 are is about two orders of magnitude larger than the Young's modulus of the adhesive, so the pressure 1/tensile stress parallel to the surface of the passive shaft 1 is absorbed by the shear/shear deformation of the adhesive, and the passive shaft 1 and the magnetic layer 5
．． 6, it is assumed that only --like expansion and contraction deformation occurs in the length direction and no bending deformation occurs. Further, if the deformation of the passive shaft 1 in the X direction (length direction) is ul, and the deformation of the magnetic layer 5.6 is u2, then the shear deformation T received by the adhesive is the rigidity G of the adhesive.
This is the relationship between c and shear force τ. Also, t2 is 2
About 5 μ, t is several thousand μ, so EltI)Ezt
The assumption that t holds true, the proportion of stress propagated from the passive axis l to the magnetic layer 5.6 via the adhesive, that is, the stress propagation ratio □
is given by σ 10 h E t t t . Figure 3 shows the relationship between the adhesive thickness h and the stress propagation ratio using the length of the magnetic layer 5.6 as a parameter, and as the adhesive thickness changes, the stress propagation ratio also changes. . In this example, the thickness of the adhesive is 20-1
Since the stress propagation ratio is 00 μ or less, the stress propagation ratio becomes large, and even when the chevron length of the magnetic layer 5.6 is, for example, 2 ma+, a stress propagation ratio of 70% or more can be obtained, and the torque detection sensitivity is improved.

Furthermore, efficiency is also improved due to improved torque detection sensitivity, and the current applied to the detection coils 8 and 9 can be reduced.
Heat generation from capacitors, resistors, etc. is reduced, power-on drift, aging and deterioration are reduced, and reliability is improved.

Note that although a film adhesive was used as the adhesive, a liquid adhesive may also be used.

[Effects of the Invention] As described above, according to the present invention, an elongated magnetic layer is adhered to the outer periphery of the passive shaft via an epoxy adhesive having a thickness of 20 to 100 Pa. The thinner thickness improves stress propagation from the passive shaft to the magnetic layer, improving torque detection sensitivity. Furthermore, since the thickness of the adhesive is thin, adhesive strength is also improved, and reliability is improved. Furthermore, efficiency is also improved due to improved detection sensitivity, and the current in the detection coil can be reduced, which reduces heat generation and extends life.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a torque detector according to the present invention, FIG. 2 is a diagram showing the relationship between adhesive thickness and its shear strength, and FIG. 3 is a diagram showing the relationship between adhesive thickness and stress propagation ratio. ■... Passive axis, 5.6... Magnetic layer, 8.9... Detection coil. Agent Masuo Oiwa Figure 1 Figure 2 Figure 3

Claims (2)

[Claims] (1) A passive shaft that receives torque, and multiple strips of highly magnetostrictive material fixed at a predetermined angle to the axial direction via an epoxy adhesive with a thickness of 20 μm or more and 100 μm or less on the outer periphery of the passive shaft. A torque detector comprising an elongated magnetic layer and a detection coil disposed around the magnetic layer with a gap therebetween to detect changes in permeability of the magnetic layer due to torque applied to a passive shaft. (2) The torque detector according to claim 1, wherein the magnetic layer is made of amorphous metal.