JPS5946526A - Electromagnetic stress sensor - Google Patents

Abstract

PURPOSE:To prevent the occurrence of poor contact, by constituting a magnetic core means by a magnetic core supporting body, which is attached to a body to be detected, and a pair of tubular bodies of a high permeability material, which surrounds said magnetic core supporting body and has a saw tooth edge, and providing a coil means so as not to contact with said tubular body. CONSTITUTION:A DC or AC voltage is applied to an exciting coil 9. Then magnetic lines of force are generated in a magnetic circuit comprising a tubular body 2b, a tubular coil supporting body 8, and gaps d1 and d2 and in a magnetic circuit comprising a magnetic core supporting body 2a, an annular body 2d, the tubular body 2b, the gap d2, and the tubular coil supporting body 8. When torque is applied to a rotary shaft 1 at this time, the reluctance of the latter magnetic circuit is changed, and the magnetic lines of force generated in the former magnetic circuit is also changed. By detecting the inductance change of the coil as a result of the change in the number of the magnetic lines of force related to the shaft torque, the shaft torque can be accurately measured.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic core means associated with a subject whose stress is to be measured; a coil means provided around the magnetic core means; The present invention relates to an electromagnetic stress sensor comprising a detection means for detecting stress based on a correlation with the stress. Furthermore, the present invention particularly relates to an electromagnetic stress sensor that measures the axial torque of a rotating shaft.

As a conventional electromagnetic stress sensor, there is one shown in FIG. ] is a rotating shaft as an object to be measured for stress or shaft torque, 2 is a magnetic core means coaxially attached to the rotating shaft 1, and 1. 8 is a coil means provided around the magnetostrictive material 2, and 4 is a detection means for detecting the rotational torque of the rotating shaft 10 from a change in self-inductance that correlates with deformation of the magnetostrictive material.

However, in conventional electromagnetic stress sensors,
Since the coil was wound around the magnetic core means, for example, the magnetostrictive material 2, the coil also rotated with the shaft, and the electromagnetic changes occurring at both ends of the coil could not be taken out without passing through the slip ring. There is a problem in that contact failure may occur due to wear.

Furthermore, the conventional sensor is a magnetostrictive stress sensor that applies the inverse magnetostrictive (pilary) effect of a ferromagnetic material. That is,
In a ferromagnetic material, the crystal lattice is deformed in the direction of spontaneous magnetization inside the magnetic domain, so when full strain is applied, the magnetic domain in that direction becomes stable or unstable, and the magnetization characteristics change. The rotational torque of the rotating shaft can be detected by changing the self-inductance of the magnetic core of the coil.

However, Hiko explained that although the pillar effect is noticeable for uniaxial tension and compression, the effect is not as pronounced for screw threads, and that it is difficult to accurately measure rotational torque. There is a problem.

The present invention was developed by paying attention to such conventional problems, and includes a magnetic core means, a magnetic core support attached to a subject,
and a pair of cylindrical bodies made of a high magnetic permeability material having serrated edges surrounding a magnetic core support. The coil means is attached to the magnetic core support via the cylindrical body, and the coil means is disposed on the inner surface of the cylindrical coil support means surrounding the cylindrical body so as to come into contact with the cylindrical body. The object of the present invention is to solve the above problems by creating a structure in which the detection is noticeable and can be detected without using a slip ring.

Hereinafter, the present invention will be explained based on the drawings. FIG. 2 shows an embodiment of the electromagnetic stress sensor of the present invention. First, to explain the configuration, in the embodiment shown in FIG. and a pair of cylindrical bodies 2b made of a high magnetic permeability material and having serrated edges surrounding the magnetic core support 2a, and each serrated edge 20f facing and spaced apart from each other. An annular body 2d71 at the end edge of the cylindrical body opposite to the edge 20
r- to the magnetic core support 2a (see FIG. 3).

In the embodiment shown in FIGS. 2 and 3, the serrated edge 2
Both convex portions and concave portions of C are opposed to each other in the axial direction, and a gap δ□ is left between the opposing convex portions. The annular body 2d can be formed integrally or separately from the same material as the cylindrical body 2b, but it can also be fixed as a separate body from a different material.

The assembly of the rotating shaft 1 and the magnetic core means is rotatably mounted within the cylindrical coil support means via the bearing 6. This cylindrical coil support means includes a cylindrical body 7 made of a low magnetic permeability material that fully supports the bearing, and a high-pressure coil fixed to the inner surface of the cylindrical body 7 so as to surround the cylindrical body 2b of the magnetic core means without contacting it. It is constructed with a cylindrical coil support 8 made of a magnetically permeable material, and coil means, that is, an excitation coil 9 and a detection coil 10 are attached to the inner surface of the cylindrical coil support 8. This cylindrical coil support 8
7 langes 8a extending radially inward are provided at both ends of the
The free end of the flange 8a is opposed to the edge of the cylindrical body 2b on the annular body 2d side, leaving a gap d2. Furthermore, the excitation coil 9 is connected to a DC or AC power supply, and the detection coil 10f
Connect to detection means.

Next, the effect will be explained. When a DC or AC voltage is applied to the excitation coil, a magnetic circuit consisting of the cylindrical body 2b, the cylindrical coil support 8, and gaps d□, d2 and the magnetic core support 2
a, annular body 2d, cylindrical body 2b.

Lines of magnetic force are generated in the magnetic circuit exerted by the gap d11 and the cylindrical coil support. At this time, when torque is applied to the rotating shaft 1, the shaft 1 and the magnetic core support 2a are twisted, a slight reverse magnetostriction (pilary) effect is generated on the magnetic core support 2a, and the cylindrical bodies 2b are opposed to each other. The relative position of the serrated #A edge changes (see Figure 4). Therefore, when a torque is applied to the shaft, the magnetic permeability of the magnetic core body changes slightly due to the slight reverse magnetostriction of the magnetic core support, and the magnetic permeability in the gap d□ changes slightly due to the relative position change of the opposing serrated edges. Overall, the magnetic resistance of the latter magnetic circuit changes relatively largely, and the number of magnetic lines of force generated in the former magnetic circuit also changes relatively largely. Therefore, the shaft torque can be accurately measured by detecting the change in the inductance of the coil as a result of the change in the number of lines of magnetic force that correlates with the shaft torque. The correlation between the torque and the inductance of the magnetic circuit is shown in FIG. In addition,
The characteristic shown by the dotted line in Figure 5 shows the characteristic corresponding to the relative position change of the opposing serrated edges, and the characteristic shown by the solid line corresponds to the inverse magnetostriction, which is added to the characteristic shown by the dotted line. It is something. Furthermore, since the coil means does not rotate together with the rotating shaft, the detection means 4. No need to connect to.

In the embodiments shown in FIGS. 2 and 8, the shape of the serrated edge when developed is a rectangular row of protrusions and protrusions, and the four parts and the protrusions are opposed to each other. The magnetic core means can also be constructed so that both the projections and depressions are fitted with each other with a gap as shown in FIG. In this case, when torque is applied, the state changes as shown in Figure 6 (1)),
The relationship between torque and inductance at this time is as shown in Figure $7.

Furthermore, the shape of the serrated edge may be a triangular row of projections and depressions spanning a trapezoid instead of a rectangular row of projections and recesses, and in this case, the magnetic core means is configured so that the projections are in contact with each other instead of facing each other. You can also. Further, as shown in FIG. 6(a), the concave and convex portions may be fitted with each other with a gap between them.

The arrangement pinch of the unevenness is preferably determined depending on the size of the range of torsional deformation due to torque fluctuation.

In the case of embodiments in which the concave and convex portions of the serrated edges fit together or the convex portions are brought into opposing contact with each other, it is suitable for detecting a specific torque value, and this torque value detection can be applied to all on/off control. .

Furthermore, as in the embodiment shown in FIG.
5 When the cylindrical body 2b is made of the same high magnetic permeability material as the cylindrical body 2b, the two types of magnetic circuits described above are generated, but the annular body 2ci'Ii7 has a low magnetic permeability different from that of the cylindrical body 2b. When provided as a separate body depending on the material, the magnetic core support 2a may be made of any material and does not need to be made of a high magnetic permeability material, and when the magnetic core support is made of a high magnetic permeability material, the magnetic circuit involved in detection may be Cylindrical body 2b, cylindrical coil support 8
And only the magnetic circuit extends from the gaps d□ and d2.

As has been explained, in accordance with the present invention, the magnetic core means comprises a magnetic core support attached to the specimen and a pair of high magnetic permeability materials surrounding the magnetic core support and having serrated edges. The cylindrical bodies are attached to the magnetic core support via the annular body so that the serrated edges thereof face each other, and the coil means is attached to the magnetic core support so as not to come into contact with the cylindrical body. Since the structure is arranged on the inner surface of the cylindrical coil support means surrounding the cylindrical body, the amount of change in magnetic resistance in the magnetic circuit due to stress increases, and therefore stress can be detected with high accuracy, and the coil means is fixed. A slip ring is often used, which has the effect of being able to detect stress.

Furthermore, since a cylindrical magnetic core means is provided, the overlapping distribution is even in the circumferential direction of the axis. Therefore, even if the subject rotates at high speed around the axis, it will not be affected by vibration due to air resistance, and the axis will not be affected by vibration due to air resistance. Torque can be detected accurately and stably from low to high torque. Also, since there are no worn parts, the lifespan can be significantly extended.

Furthermore, although the above-mentioned embodiments have been described with respect to the detection of shaft torque, the gap d1. It is also possible to detect compressive stress and tensile stress by changing d2.

[Brief explanation of the drawing]

Fig. 1 is a diagram of a torque sensor as a conventional electromagnetic stress sensor, Fig. 2 is a diagram of an embodiment of the electromagnetic stress sensor of the present invention, and Fig. 8 is a diagram of a torque sensor as a conventional electromagnetic stress sensor. FIG. 4 is a perspective view of the related magnetic core means. FIG. 4 is an explanatory diagram showing a state in which the relative position of the serrated edge of the cylindrical body of the magnetic core means is moved by torque. FIG. Graph showing the relationship with the inductance of the coil means, Fig. 6(a), Φ)
are explanatory diagrams showing the no-load state and the state when torque is applied to the serrated edge of the cylindrical body, which are installed differently from the embodiment shown in FIG. 2, respectively. 3 is a graph showing the relationship between the torque applied to the rotating shaft and the inductance of the coil means in the embodiment having the cylindrical body shown in FIG. 1... Rotating shaft, 2... Magnetostrictive material (magnetic core means), 2a.
...Magnetic core support, 2b...High magnetic permeability paulownia material cylindrical body, 2
G: serrated edge, 2d: annular body, 3: coil means,
4...Detection means, 5...Diamagnetic member, 6...Bearing, ? . . . Cylindrical body made of low magnetic permeability material, 8. Cylindrical coil support, 9. Excitation coil, ] 0. Detection coil. Sign V+- Applicant Nissan Motor Co., Ltd. Figure 2 Figure 6 (a) (b) Figure 7

Claims (1)

[Claims] 1. Stress is detected based on a magnetic core means related to the subject whose stress is to be measured, a coil means provided around the magnetic core means, and a correlation between the deformation of the magnetic core means caused by stress and the inductance of the coil means. an electromagnetic stress sensor comprising: a magnetic core support attached to a subject; and a pair of tubes of high magnetic permeability material surrounding the magnetic core support and having serrated edges. These cylindrical bodies are attached to a magnetic core support via an annular body such that their serrated edges face each other, and the coil means is configured to be in contact with the cylindrical body. An electromagnetic stress sensor that is disposed on the inner surface of a cylindrical coil support means surrounding a cylindrical body.