JPH02280022A - Magnetostrictive torque detector - Google Patents

Abstract

PURPOSE:To prevent the error of an output caused by the relative dislocation by supporting a shaft to be measured with a supporting body through a bearing and holding a coil provided in the vicinity of a magnetic anisotropy part with the shaft to be measured through another bearing for coil. CONSTITUTION:The shaft 4 to be measured provided with magnetic anisotropy parts 6a, 6b is supported by a supporting body 2 through supporting bearings 3a, 3b, and coils 15a, 15b provided in the vicinity of the anisotropy parts 6a, 6b are held by the shaft 4 through other bearings 11a, 11b for coil. Accordingly, when a large load is applied to the shaft 4 in the axial direction, it is received by the supporting body 2 through the bearings 3a, 3b and no load is applied to the part for holding the coil. Also, since a coil casing 12 is energized in the axial direction by a tension spring 18, the relative dislocation in the axial direction of spiral grooves 5a, 5b of the shaft 4 and the coils 15a, 15b does not occur. In such a manner, an output error caused by the dislocation is eliminated and the torque can be exactly detected.

Description

[Detailed description of the invention] [Purpose of the invention]

(Industrial Application Field) The present invention relates to a magnetostrictive torque detector used to detect torque using a magnetostrictive effect. (Prior Art) FIGS. 6 and 7 schematically show the structure of this type of torque detector that utilizes the magnetostrictive effect. This magnetostrictive torque detector 51 has a surface plate. A bearing 53a for supporting the shaft to be measured is attached to a support 52 such as a vehicle body or a building.
, 53b to rotatably support the shaft to be measured 54,
The shaft to be measured 54 is made of, for example, Fe-13% by weight An alloy, mechanical structural steel (SCM,
Figure 7 (a)
As also shown in (b), a plurality of partial spiral grooves 55a are formed on the surface at an angle of ±45 degrees with the axial direction and in the circumferential direction. 55b are formed symmetrically on the left and right sides, and these parts are provided with geometrical magnetic anisotropy parts 56a and 56b due to the skin effect of magnetic permeability, and on the end side of the support body 52, a bearing stopper 57a, 57b is provided, and a yoke 58 is fixed on the inner peripheral side with screws 59, and this yoke 58
, a magnetic anisotropic portion 56a provided on the shaft 54 to be measured.
, 56b, that is, the left and right partial spiral grooves 55
a. The coil 60a is located at a position where the centers 60a-c, 60b-c of the coils 60a, 60b are aligned with the centers 55a-c, 55b-c of each of the coils 55b. 60b, the yoke 58 and the coil 60a
, 60b and the shaft 54 to be measured, with a gap 61 provided therebetween. In addition, as shown in FIGS. 8(a) and 8(b), the fixed shaft 54 of the fixed shaft 611 may be made of, for example, the same <Fe-13% by weight An alloy or m for machine structures (SCM, SNCM, etc.). There is also one in which a partially spiral thin film 65a, 65b made of a non-magnetic electrically conductive material such as copper is formed by plating on the surface thereof, thereby providing geometrically magnetically anisotropic parts 56a, 56b in these parts. there were. Furthermore, the surface of the shaft 54 to be measured may be made smooth in the circumferential direction by embedding a non-magnetic electrically conductive material such as copper into the partial spiral grooves 55a and 55b shown in FIGS. 7(a) and 7(b). (For example, Japanese Patent Application Laid-Open No. 62-1851
Publication No. 36). To explain how to detect torque using the magnetostrictive torque detector 51 having such a structure, first, before detecting torque, as shown in FIG. A bridge circuit is formed with the resistors 66a and 66b, and one of the opposing connection points C and D is set as the supply side (V in) of the AC power source 67, and the other opposing connection point A and B is set as the output side (V in ). VD=VB-VA), and both coils 60 are connected through the connection point C-D.
By applying a constant alternating current voltage (V in ) to each of a and 60b, the partial spiral grooves 55a and 5
5b and partially spiral thin film 65a. Shape magnetic anisotropy portion 56a formed by 65b,
56b, gap 61. A magnetic circuit passing through the yoke 58 is formed around both coils 60a, 60b, respectively. In this state, when a torsional torque T is applied to the shaft 54 to be measured, for example in the right direction, one portion of the helical groove 5
5a and the partially spiral thin film 65a undergoes tensile deformation, and the other magnetically anisotropic section 56b formed by the other partially spiral groove 55b and the partially spiral thin film 65b undergoes tensile deformation. undergoes compressive deformation. For example, a shaft to be measured 54 having a magnetostriction constant of >0
When using , the magnetic permeability increases under tensile deformation and decreases under compressive deformation. As a result, the inductance LA of one coil 60a increases, and the inductance LB of the other coil 60b decreases. Then, when a torsional torque in the left direction is applied to the shaft 54 to be measured, contrary to the above case, the situation is reversed to the above case. Therefore, the alternating current constant voltage (V i
When torque T is applied to the measured shaft 54 with the voltage VD (= VB
-VA) becomes XRo XV in . (Problem to be Solved by the Invention) However, such a conventional magnetostrictive torque detector 5
In No. 1, a coil 60a is connected to a support 52 that supports a shaft 54 to be measured via a yoke 58. 60b is attached and a large axial load is applied to the shaft 54 to be measured, the relative positions of the fixed shaft 54 of the 611 and the coils 60a and 60b will shift in the axial direction. Therefore, when a large load is applied in the axial direction, the inductances LA and LB of the left and right magnetic anisotropic parts 56a and 56b change, and the difference between the inductances LA and LB is detected by the torque detector 51.
Therefore, there was a problem in that an output error could occur due to the addition of an axial load.6 (Objective of the Invention) This invention was made by focusing on such a conventional problem. Even when a large load is applied to the shaft to be measured in the axial direction, the load is not applied to the part that holds the coil, so that relative positional deviation in the axial direction does not occur between the shaft to be measured and the coil. It is an object of the present invention to provide a magnetostrictive torque detector that can prevent errors in output and accurately detect torque.

[Structure of the invention]

(Means for Solving the Problems) This invention provides a method for attaching a shaft to be measured which has a magnetostrictive effect on at least the surface or the entire surface and is provided with a magnetic anisotropic portion to a support via a bearing for supporting the shaft to be measured. A coil is disposed near the magnetically anisotropic portion, and a magnetic flux generated by the coil forms a magnetic circuit passing through the magnetically anisotropic portion of the shaft to be measured. In a magnetostrictive torque detector that detects the torque using magnetostriction caused by deformation of the shaft to be measured due to torsional torque applied thereto, the coil is held on the shaft to be measured via a coil holding bearing. One embodiment is characterized by a configuration in which a force in the axial direction is kept applied to the coil, and such a configuration solves the above-mentioned conventional problem. It is used as a means to solve the problem. (Operation of the invention) In the magnetostrictive torque detector according to the present invention, the shaft to be measured provided with the magnetic anisotropic portion is connected to the surface plate through the bearing for supporting the shaft to be measured.
This is because the coil is supported by a support such as a vehicle body or a building, and the coil disposed near the magnetic anisotropic portion is held by the shaft to be measured via a coil holding bearing. . When a large load is applied to the measured axis in the axial direction,
This load is received by the support body through the bearing for supporting the shaft to be measured, and the load is not applied to the part that holds the coil, so the axial direction between the shaft to be measured and the coil is This results in the effect that relative positional deviation does not occur, and output errors due to positional deviation are eliminated, allowing accurate torque detection. (Embodiment) FIG. 1 shows a schematic structure of a torque detector using the magnetostrictive effect according to the present invention. A bearing 3a for supporting a shaft to be measured is mounted on a support 2 such as a building. A shaft 4 to be measured is rotatably supported via the shaft 3b, and the shaft 4 to be measured is made of, for example, Fe-
13% by weight An alloy and mechanical structural steel (SCM, SNCM
etc.), and as shown in Fig. 7, a plurality of partial spiral grooves 5a, 5b are formed on the surface at an angle of ±45 degrees with the axial direction and in the circumferential direction, symmetrically on the left and right. These parts are formed to have geometrically magnetic anisotropic parts 6a and 6b due to the skin effect of magnetic permeability, and a bearing stopper 7a is provided on the end side of the support 2. 7b for positioning, and coil holding bearings 11a and llb are provided on the stepped portions 4a and 4b of the shaft 4 to be measured, and the coil casing 12 is fixed to these coil holding bearings 11a and llb, and the coil casing 12 is fixed to these coil holding bearings 11a and llb. Bearing stoppers 13a and 13b are provided on the end side of the casing 12, and a yoke 14 is fixed on the inner peripheral side of the coil casing 12. Coils 15a and 15 are installed near the portions 6a and 6b, that is, at the center of each of the left and right partial spiral grooves 5a and 5b.
When the centers of the coils 15a and 15b coincide with each other,
b, and the yoke 14 and coils 15a, 1
5b and the shaft to be measured 4, and a bracket 2a provided on the support body 2 and the coil casing 12.
A tension spring 18 is hung between the coil casing 12. The structure is such that the yoke 14 and the coils 15a, 15b are urged in the axial direction (rightward in FIG. 1), and the coil casing 12 degrees prevents the rotation of the yoke 14 and the coils 15a, 15b. When detecting torque using the magnetostrictive torque detector 1, it is connected to the circuit shown in FIG. In this case, in addition to pure torque, loads such as axial (thrust direction) force, radial direction (radial direction) force, and bending stress are often applied. In this case, these loads are transmitted to the support body 2 via the bearings 3a and 3b for supporting the shaft to be measured, and the above-mentioned loads are not applied to the yoke 14 and the coils 15a and 15b. 15a and 15b are held by the coil casing 12 via the yoke 14 and are connected to the tension spring 1.
8 in the axial direction (rightward in Figure 1), the partial helical shape y formed on the shaft 4 to be measured
Fluctuations in relative position in the axial direction between t5a, 5b and coils 15a, 15b can be kept extremely small. Furthermore, depending on the usage conditions, for example, take into account axial thermal expansion caused by an increase in temperature.
By selecting the materials of the coil casing 12 and the yoke 14, the partial spiral grooves 5a and 5b can be formed even when the temperature rises.
It is also possible to reduce the influence of thermal expansion by aligning the centers of the coils 15a and 15b with the centers of the coils 15a and 15b. Fig. 5S2 shows another embodiment of the magnetostrictive torque detector according to the present invention. A bracket 2a that supports the shaft 4 to be measured on the support 2 via a bearing 3 and is provided on a flange 19 fixed to the support 2;
2b and the bracket 12a provided on the coil casing 12
. 12b, tension springs 18a, 18b are applied between the coil casing 12. Yoke 14 and coil 15a
, 15b in the axial direction and the coil casing 12. The structure is such that the yoke 14 and the coils 15a, 15b are prevented from rotating. In the torque detector 1 according to this embodiment, the measured shaft 4 is supported by one measured shaft supporting bearing 3, for example, a third
As shown in the figure, it can also be used to detect the torque applied to the main shaft of a machine tool such as a drilling machine. That is, in FIG. 3, the shaft to be measured 4 is the main shaft, and the chuck 21 and the tool 22 are attached to the lower end of the main shaft (4). In this way, when applied to a machine tool, the magnetic anisotropic parts 6a, 6b and the coil 15a, which are the sensor parts of the upper shaft (4), regardless of the feeding state of the tool 22,
, 15b in the axial direction is always kept constant, so that fluctuations in output during torque detection can be kept small. FIG. 4 shows still another embodiment of the magnetostrictive torque detector according to the present invention, and this magnetostrictive torque detector 1 includes:
In contrast to the magnetostrictive torque detector 1 shown in FIG. 2 in which pole bearings are used as the coil holding bearings 11a and llb, a case is shown in which air bearings with air passages and passages 11 are used. , each air bearing (l
la. An air pipe 20 is connected to the air passage 11 of 11b), and an air bearing retainer 21 is provided on the stepped portion 4a of the shaft to be measured 4 facing one coil holding bearing 11a. It is something. In the magnetostrictive torque detector 1 having the structure shown in FIG.
The load is transmitted to the support body 2 via the yoke 14 and the coils 15a and 15b, so that the load is not applied at all to the yoke 14 and the coils 15a and 15b. Further, the coils 15a and 15b are held by the coil casing 12 via the yoke 14, and the tension spring 1
8a and 18b in the axial direction (to the right in FIG. 4), the partial helical groove 5a formed in the shaft 4 to be measured. 5b and the coils 15a, 15b, the variation in relative position in the axial direction becomes extremely small. Furthermore, since air bearings are used as the coil holding bearings 11a and llb, it is possible to eliminate the heat generation in the bearing parts that occurs when pole bearings are used, and the temperature of the shaft 4 to be measured can be kept constant. It also has the advantage of being able to do Figure 5 shows the magnetostrictive torque detector (bearing 2) shown in Figure 1.
A magnetostrictive torque detector in which the tension spring 18 is not tensioned in the magnetostrictive torque detector 1 shown in FIG. 1 (example of two-stage bearing), and This is an example of the results of investigating the relationship between the torque applied to the shaft to be measured and the error using the conventional magnetostrictive torque detector (conventional example) shown in the figure. It was observed that the error was considerably smaller.

【Effect of the invention】

The magnetostrictive torque detector according to the present invention supports a shaft to be measured having an ri1 anisotropy section on a support such as a surface plate, a vehicle body, or a building via a bearing for supporting the shaft to be measured. Since the coil disposed near the directional part is held on the shaft to be measured via a coil holding bearing that is different from the bearing for supporting the shaft to be measured, the shaft to be measured is For example, when a large load is applied in the axial direction, this load is received by the support body through the bearing for supporting the shaft to be measured, and the load is not applied to the part that holds the coil. This makes it difficult to cause relative positional deviation in the axial direction between the center of the magnetic anisotropic part of the measurement axis and the center of the coil, resulting in a significantly superior effect in that output errors due to positional deviation can be prevented. It will be done.

[Brief explanation of drawings]

1 and 2 are cross-sectional explanatory views of magnetostrictive torque detectors according to embodiments of the present invention, and FIG. 3 shows a case where the magnetostrictive torque detector shown in FIG. 2 is applied to a machine tool. FIG. 4 is a cross-sectional explanatory diagram of a magnetostrictive torque detector according to still another embodiment of the present invention, and FIG. 5 is a graph illustrating the results of examining the torque-error characteristics of each magnetostrictive torque detector. , FIG. 6 is a cross-sectional explanatory diagram of a conventional magnetostrictive torque detector, and FIGS. 7(a) and 7(b) are a partial front view and a sectional view, respectively, showing an example of the shaft to be measured used in the magnetostrictive torque detector. , FIGS. 8(a) and 8(b) are partial front views and cross-sectional views showing other examples of the shaft to be measured used in the magnetostrictive torque detector, and FIG. iI
! , is an explanatory diagram illustrating a small example of an I' circuit. 1...Magnetostrictive torque detector, 2...Support, 3゜3
a, 3b... Bearing for supporting the shaft to be measured, 4... Shaft to be measured, 6a, 6b... Magnetic anisotropic part, lla, llb.
... Coil holding bearings, 15a, 15b... Coil retention. Figure 6 Figure 7 (G) Figure 7 (b) Patent applicant Nissan Motor Co., Ltd.

Claims (1)

[Claims] (1) A shaft to be measured, which has a magnetostrictive effect at least on the surface and is provided with a magnetic anisotropic portion, is supported by a support body via a bearing for supporting the shaft to be measured, and the shaft is provided with a magnetic anisotropic portion in the vicinity of the magnetic anisotropic portion. A coil is disposed in the coil, and the magnetic flux generated by the coil forms a magnetic circuit passing through the magnetic anisotropic portion of the shaft to be measured, and the deformation of the shaft to be measured is caused by the torsional torque applied to the shaft to be measured. A magnetostrictive torque detector that detects the torque using magnetostriction, characterized in that the coil is held on the shaft to be measured via a coil holding bearing.