JPH087104B2 - Magnetostrictive torque detector - Google Patents

Description

Detailed Description of the Invention [Object of the invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetostrictive torque detector used for detecting torque by utilizing a magnetostrictive effect. (Prior Art) FIG. 2 and FIG. 3 exemplify a schematic structure of a torque detector utilizing this type of magnetostrictive effect.
This magnetostrictive torque detector 11 uses, for example, a Fe-13 wt% Al alloy or a mechanical structural steel (SCM, SNCM, etc.) having a magnetostrictive effect as the shaft 12 to be measured, and is shown in FIGS. As also shown in, the surface is formed with a plurality of partial spiral grooves 13a, 13b in the circumferential direction forming an angle of ± 45 degrees with the direction of the central axis 12A and symmetrically in the circumferential direction. Forming magnetic anisotropy portions 14a and 14b by the skin effect of magnetic permeability are provided, and in the vicinity of the measured shaft 12, that is, the centers 13a-c, 13b-c of the left and right partial spiral grooves 13a, 13b, respectively. In coil 1
The coils 15a and 15b are arranged at positions where the centers 15a-c and 15b-c of the coils 5a and 15b are aligned with each other, and the outer peripheral portions of the coils 15a and 15b are
A structure is provided in which a yoke 17 made of a high magnetic permeability material is provided with a gap 16 provided between the measured shaft 12 and the shaft 12. Further, as shown in FIGS. 4 (a) and (b), the measured shaft 12
For example, similarly using Fe-13 wt% Al alloy and steel for machine structure (ScM, SNcM, etc.), by forming a non-magnetic good electric conductor, for example, a partial spiral thin film 18a, 18b made of copper by plating In some cases, these portions are provided with geometrically anisotropic magnetic portions 14a and 14b. Furthermore, by embedding a non-magnetic good electric conductor such as copper in the partial spiral grooves 13a and 13b shown in FIGS. 3 (a) and 3 (b), the surface of the shaft 12 to be measured is made smooth in the circumferential direction. Some have been done (for example, JP-A-62-185136). Explaining how to detect torque using the magnetostrictive torque detector 11 having such a structure, first, as shown in FIG. 5, two coils 15a and 15b and two coils 15a and 15b are provided prior to the detection of torque. A bridge circuit is formed by the resistors 19a and 19b, one of the connecting points C and D facing each other serves as the supply side (Vin) of the AC power supply 20, and the other connecting point A and B of the facing side connects to the output side (V _D = V _B -V _a) and then was circuitry, both coils 15a through the inter-connection point C-D, a constant voltage of each AC to 15b (Vin)
Add. In this way, the partial spiral groove 13a,
Shape magnetic anisotropy part 14a, 14b formed by 13b, gap 1
6, magnetic circuits passing through the yoke 17 are formed around the coils 15a and 15b, respectively. In this state, when a torsional torque T is applied rightward to the shaft 12 to be measured, one magnetic anisotropic portion 14a formed by one partial spiral groove 13a undergoes tensile deformation and the other partial spiral. The other magnetic anisotropic portion 14b formed by the groove 13b undergoes compressive deformation. For example, when the measured shaft 12 having a magnetostriction constant λ> 0 is used, the tensile deformation increases the magnetic permeability, and the compressive deformation decreases the magnetic permeability. As a result, the inductance L _A of the one coil 15a increases and the inductance L _B of the other coil 15b decreases. Then, when a leftward twisting torque is applied to the shaft to be measured 12 contrary to the above, it is the opposite of the above case. Therefore, when the torque T is applied to the shaft 12 to be measured while the constant voltage (Vin) of AC is applied by the AC power supply 20, the pressure voltage V _D (= V _B −V _A ) between the connection points A and B becomes , Becomes (Problems to be Solved by the Invention) However, in such a conventional torque detector 11, the left and right partial spiral grooves 13 formed on the shaft to be measured 12 are formed.
Coils 15a and 15b at the centers 13a-c and 13b-c of a and 13b, respectively.
Although the two coils 15a and 15b are arranged so that the centers 15a-c and 15b-c of the two are aligned, as shown in FIG. 7, a measuring instrument 21 for measuring the inductance L and the resistance R is used. The ring-shaped detection coil 22 connected to the
12 was inserted, the shaft 12 to be measured was moved in the axial direction, and changes in the inductance L and the resistance R in the direction of the central axis of the shaft 12 to be measured were examined. As shown in FIG. Center 13a-c of the partial spiral grooves 13a, 13b formed in
It is clear that 13b-c and the centers L _A −c and L _B −c of the peaks of the inductance L are displaced by the displacement amounts δ and δ ′.
Therefore, the centers of the partial spiral grooves 13a, 13b 13a-c, 13b-
In the conventional case in which c and the centers 15a-c and 15b-c of the coils 15a and 15b are aligned, as shown in the conventional example of FIG. When the absolute value of (ΔL = L _B −L _A ) becomes relatively large and, for example, the measured shaft 12 is displaced in its thrust direction due to rattling of the bearing supporting the measured shaft 12, Is (ΔL
= L _B −L _A ) becomes large, a relatively large value due to displacement in the thrust direction as shown in the conventional example of FIG. 9 is generated between the output ends V _A −V _{B of} the bridge circuit shown in FIG. There was a problem of generating a bridge differential output (error output). (Object of the Invention) The present invention has been made in view of the above-mentioned conventional problems, in a torque detector that detects torque by utilizing the magnetostrictive effect of the shaft to be measured, the shaft to be measured is the center of the torque detector. It is an object of the present invention to make it possible to significantly reduce the error output at the time of torque detection even when it is displaced in the axial direction (thrust direction).

Configuration of the Invention

(Means for Solving the Problem) The present invention provides a coil in the vicinity of a measured shaft provided with a magnetic anisotropic portion having a magnetostrictive effect at least on the surface and forming a predetermined angle with respect to the central axis direction. The magnetic flux generated from the coil forms a magnetic circuit that passes through the magnetic anisotropy portion of the shaft to be measured, and the magnetic force resulting from the deformation of the shaft to be measured by the torsional torque applied to the shaft to be measured. In the magnetostrictive torque detector that detects the torque by utilizing strain, the coil of the coil is adjusted according to the position of the peak of magnetic permeability (including the vicinity of the position of the peak) in the magnetic permeability distribution characteristic of the shaft to be measured. It is characterized in that the center is arranged, and such a structure of the torque detector is used as means for solving the above-mentioned conventional problems. The shaft to be measured applied in the magnetostrictive torque detector according to the present invention has a magnetostrictive effect at least on the surface, and does not have a magnetostrictive effect or the axial strain on the surface of the shaft main body made of a small material. It is possible to use a structure in which a material having an effect is provided, or it is possible to use an integrated material having a magnetostrictive effect. The shaft to be measured has a structure in which a magnetic anisotropy portion that makes a predetermined angle with respect to the central axis direction is provided. The magnetic anisotropy portion in this case is shown in FIG. It can be provided by forming the partial spiral grooves (13a, 13b) as described above, but the spiral thin film (18a, 18b) made of a non-magnetic good electric conductor as shown in FIG.
It is also possible to provide the magnetic anisotropy portion by forming a groove-shaped portion or a projection-shaped portion having a relative shape with the groove-shaped portion. Further, the number of coils provided near the magnetic anisotropy portion of the measured axis is not particularly limited, and for example, two coils may be provided to form a part of the bridge circuit,
It is also possible to provide four bridge circuits and a part of the temperature compensation circuit. In the torque detector according to the present invention, the center of the coil is arranged at or near the position of the peak of the magnetic permeability in the magnetic permeability distribution characteristic of the shaft to be measured. The magnetic susceptibility peaks may be inductance peaks or impedance peaks. (Operation of the Invention) This invention is a torque detector for detecting torque by utilizing the magnetostrictive effect of a shaft to be measured, and the position of the peak of the magnetic permeability in the magnetic permeability distribution characteristic of the shaft to be measured (peak). Since the center of the coil is arranged in accordance with the position of, the magnetic permeability changes in the direction in which the magnetic permeability decreases when the measured shaft deviates to the left or right in the direction of the central axis. 5 and 6 when two coils 15a and 15b are provided as in the conventional case, for example.
As shown in the figure, the inductance L _A of one coil 15a decreases while the inductance L _{B of the} other coil 15b decreases.
The difference between the inductances L _A and L _B | L _B −
Since L _A | does not cause an expanding change, the action of reducing the error output due to the displacement of the measured shaft in the central axis direction (thrust direction) is brought about. (Embodiment) FIG. 1 shows an embodiment of a magnetostrictive torque detector according to the present invention. The magnetostrictive torque detector 1 has a surface portion of a shaft 2 to be measured having a magnetostrictive effect. Forming an angle of ± 45 degrees with the direction of the central axis 2A of the shaft to be measured 2 and forming plural partial spiral grooves 3a, 3b in the circumferential direction so as to be symmetrical on the left and right sides, The magnetically anisotropic portions 4a and 4b are provided by the skin effect, and the coils 5a and 5b are provided in the vicinity of the magnetically anisotropic portions 4a and 4b.In this case, the coils 5a and 5b are provided. Is wound on the bobbins 6a, 6b, and the centers 5a-c, 5b of the coils 5a, 5b are
The bobbins 6a and 6b are connected so that −c coincides with the magnetic ridge peak positions 2a−c and 2b−c, that is, the inductance peak positions L _A −c and L _B −c shown in FIG. The structure is such that the coil position is fixed by connecting with the member 7, and the centers 5a-c, 5b-c of the coils 5a, 5b are attached to the centers 3a-c, 3b-c of the spiral grooves 3a, 3b as in the conventional case. Instead of adjusting the peaks of magnetic permeability 2a-c, 2b-c (peaks of inductance L, peaks L _A -c, L _B
The centers 5a-c and 5b-c of the coils 5a and 5b are aligned with -c) so that the coils 5a and 5b are arranged at positions displaced by a distance δ from the conventional one. Also in the torque detector 1 having such a structure,
By using the bridge circuit shown in the figure, the torque T
Is detected, and the value of the torque T is detected as the value of the voltage V _D by the equation (1). In this torque detector 1, the center 5 of the coils 5a, 5b is
a-c and 5b-c are the peak positions L _A -c and L _B -c of the inductance L shown in FIG. 6 (the peak positions 2a of the magnetic permeability shown in FIG. 1).
-C, 2b-c), the value of the difference between the inductances L _A and L _B (ΔL = L _B −L _A ) is the same as that of the conventional example as shown in FIG. Compared with the case, it becomes significantly smaller (near zero), and ΔL for the displacement of the measured shaft 2 in the central axis 2A direction, that is, the thrust direction displacement.
Has a characteristic close to flat. That is, in the numerator in the formula (1) (L _B -L _A) values significantly smaller ones (close to zero), and the bridge differential output as shown in the present invention example of FIG. 9 is a conventional Compared with the case of the example, it becomes extremely small (close to zero), and the torque detection error becomes extremely small with respect to the displacement of the measured shaft 2 in the direction of the central axis 2A, that is, the displacement in the thrust direction. Further, at the position of the peak of the inductance L, the values of the inductances L _A and L _B are large, the values of the impedances R _A and R _B are large, and the denominator is large, so that the differential output V _D
Becomes smaller, and the torque can be detected more accurately.

【The invention's effect】

The present invention relates to a torque detector for detecting torque by utilizing a magnetostrictive effect of a shaft to be measured, and a coil for generating a magnetic flux that forms a magnetic circuit passing through a magnetic anisotropic portion provided on the shaft to be measured. Since the center of the shaft is arranged according to the position of the peak of magnetic permeability in the magnetic permeability distribution characteristic of the shaft to be measured, torque can be detected even when the shaft to be measured is displaced in the direction of the central axis (thrust direction). It is possible to greatly reduce the error output at the time of, and when there is magnetic unevenness on the shaft to be measured, the rotation produces an output even in the state of zero torque. By aligning the center of the coil with the position of the peak of magnetic permeability, it is possible to reduce the influence of the magnetic unevenness, and it is possible to significantly improve the torque detection accuracy. Effect is brought about.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view of a torque detector according to an embodiment of the present invention, FIG. 2 is an explanatory view of a conventional torque detector, and FIGS. 3 (a) and 3 (b) are torque detection. Partial front view and sectional view showing an example of the shaft to be measured used in the container, FIG.
FIG. 6B is a partial front view and a sectional view showing another example of the shaft to be measured used in the torque detector, and FIG. 5 is an explanatory view showing an example of an electric circuit connected to the torque detector. FIG. 7 is an explanatory diagram showing an inductance change and a resistance change in the central axis direction of the measured shaft, FIG. 7 is an explanatory diagram showing a procedure of measuring the inductance change and the resistance change in the central axis direction of the measured shaft, and FIG. FIG. 9 is a graph showing the relationship between the displacement in the thrust direction of the shaft to be measured and the inductance difference in the conventional example and the present invention example, and FIG. 9 is the relationship between the displacement in the thrust direction of the shaft to be measured and the bridge differential output in the conventional example and the present invention example. It is a graph which shows. 1 ... Torque detector, 2 ... Measured shaft, 2A ... Central axis of measured shaft, 2a-c, 2b-c ... Position of magnetic ridge, 4a, 4b
...... Magnetic anisotropy part, 5a, 5b ...... Coil, 5a-c, 5b-c ...
… The center of the coil.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Munekatsu Shimada 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (56) Reference JP-A-63-117230 (JP, A) JP-A-59-166827 (JP, A)

Claims (1)

[Claims] 1. A coil is disposed in the vicinity of a shaft to be measured which has a magnetic anisotropy portion having a magnetostrictive effect at least on the surface and forming a predetermined angle with respect to a central axis direction, and The generated magnetic flux forms a magnetic circuit that passes through the magnetic anisotropy portion of the measured shaft, and the torque is utilized by utilizing the magnetostriction resulting from the deformation of the measured shaft due to the torsion torque applied to the measured shaft. In the magnetostrictive torque detector for detecting, the center of the coil is arranged according to the position of the peak of the magnetic permeability in the magnetic permeability distribution characteristic of the shaft to be measured.