JPH02259538A - Pressure sensor - Google Patents

Abstract

PURPOSE:To easily detect stress over a wide range with small-sized constitution by providing an iron core made of a two-directional electromagnetic steel plate and detection winding for measuring the magnetic permeability/antimagnetic force variation of the iron core corresponding to stress which is applied in the thickness direction of the iron core. CONSTITUTION:The two-directional electromagnetic steel plate is cut into a ring-shaped core and a magnetic circuit is composed of one or >=2 ring cores 1 and provided with primary winding 2 and secondary winding 3 to form a pressure element. A pressure receiving plate 5 which has a leg part 4 is provided on the surface of the core 1. A load P is placed on the pressure receiving plate 5, a DC power source 6 is connected to the winding 2, and a flux meter 7 is connected to the winding 3 to measure initial magnetic permeability and antimagnetic force. Those magnetic characteristics vary with the surface pressure of the core 1 based upon the load P and a linear relation is recognized in a certain range of the surface pressure. Thus, the magnetic permeability or antimagnetic force is measured to easily measure additional stress. The magnetic permeability is accurately measured in a low stress range and the antimagnetic force measurement is preferable in a high stress range.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pressure sensor for measuring load and stress.

[Conventional technology]

Conventionally, the following sensors have been used to measure stress or load.

■ Strain gauge pressure sensor This utilizes the fact that when stress is applied to an object, strain occurs and its electrical resistance changes.

A load cell is one such type.

■ Diaphragm pressure sensor A diaphragm is a thin disk whose peripheral part is fixed.The disk deforms elastically in proportion to the difference in pressure between one side and the other side of the disk. This is to detect.

[Problem to be solved by the invention]

However, in the strain gauge type pressure sensor, the size of the sensor to which the strain gauge is attached is required, and even the pressure type sensor has the problem of being thick.

Additionally, since diaphragm pressure sensors utilize the elastic deformation of a disc, the range of pressure changes that can be measured is narrow.
There was also the problem of large size.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a pressure sensor that is small and can easily measure up to a large stress range.

[Means to solve the problem]

In order to achieve the above object, the pressure sensor of the present invention includes an iron core made of a bidirectional electrical steel sheet, and changes in magnetic permeability or coercive force of the iron core depending on the magnitude of stress applied in the thickness direction of the iron core. It is characterized by comprising a detection winding for measurement.

[Effect]

In grain-oriented electrical steel sheets, it is known that when tension is applied to the axis of easy magnetization, the magnetic domains are subdivided and iron loss, particularly abnormal eddy current loss among eddy current losses, is reduced. This abnormal eddy current loss is an eddy current loss based on the movement of domain walls, and its analysis has been conducted only recently when magnetic domain theory and magnetic domain observation were developed.

Therefore, in the present invention, one or more bidirectional electromagnetic steel sheets are used as a core constituting a magnetic circuit, and a secondary winding is provided via a nonmagnetic substrate that receives a load. For accuracy, it is desirable that the magnetic circuit be a closed magnetic circuit.

Measurements can also be made from above the winding.

When a load is applied to the core of a bidirectional electrical steel sheet, a compressive force acts in the thickness direction of the sheet, and this force produces a tension effect on two axes of easy magnetization that are orthogonal to each other in the sheet surface direction. This tension causes the magnetic domain along the thickness direction of the bidirectional electrical steel sheet to become parallel to the sheet surface.
And because it acts to subdivide, the magnetic properties of the core,
In particular, the initial magnetic permeability μm changes depending on the core surface pressure. As shown in FIG. 3, this rate of change has a linear relationship within a certain range of surface pressure. For the same reason, the coercive force H also changes as shown in Figure 4.

Therefore, by measuring magnetic permeability or coercive force,
Added stress can be easily measured.

Stress can be measured using either method, but magnetic permeability can be measured with high accuracy in a low stress range, and coercive force measurement is preferable in a high stress range.

A similar test was conducted on the core of a grain-oriented electrical steel sheet, but there was almost no change in the magnetic properties, and there was no change in the pressure range shown in FIGS. 3 and 4. This is because the unidirectional electrical steel sheet has an axis of easy magnetization, and the 100> direction is 45° with respect to the sheet surface.
Because they intersect at an angle of

〔Example〕

Hereinafter, the present invention will be specifically explained based on Examples.

CO, 048% by weight, Si3.40% by weight, ! Jn
Q. 14% by weight.

Acid-soluble AI 0.023% by weight, total NO, 0035% by weight, balance Fe and inevitable impurities, thickness 1.65%
A hot-rolled sheet of mm was annealed at 1070° C. for 2 minutes and cold-rolled in the same direction as the hot-rolling direction at a rolling reduction of 65%. Next, it was cold rolled in a direction crossing this rolling direction at a reduction rate of 60%, and finished to a final plate thickness of 0.23 m1. This cold-rolled sheet was decarburized and annealed at 810° C. for 90 seconds in a wet hydrogen atmosphere.

After decarburization annealing, a magnesia-based annealing separator was applied to the surface of the steel sheet, and finish annealing was performed at 1200° C. for 20 hours in an atmosphere of 100% H2 to perform secondary recrystallization. This results in (
100) A bidirectional electrical steel sheet with <001> oriented grains was obtained. Then, this bidirectional electrical steel sheet was heated to 850°C for 1
Time annealed. The results are shown in Table 1.

Table 1 □i As is clear from Table 1, the magnetic steel sheet after secondary recrystallization annealing has a magnetic flux density B = (magnetic flux density of 800 A/m)
shows a high value of 1.91 T (Tesla) in both the L direction and the C direction, but the magnetic flux density in the L direction decreases as the magnetic field decreases. On the other hand, after secondary recrystallization annealing, an additional 850
In the case of those annealed at 0.degree. C., both the magnetic flux density B and the C direction exhibit almost the same values in a low magnetic field, and the rate of decrease is smaller than that of the magnetic flux density B in a high magnetic field.

A ring-shaped core was cut out from the unidirectional electromagnetic steel sheet produced in this way, and as shown in FIGS. 1 and 2, windings 2 and 3 were applied to the ring core 1 to form a pressure element. The ring core 1 was made of two types: one core and a five-layer stack. Pressure receiving plates 5, 5 having legs 4° 4 are provided on this core surface, a load P is applied to the pressure receiving plates 5, a DC power source 6 is connected to the secondary winding 2, and a magnetometer 7 is connected to the secondary winding 3. Connect the initial permeability μl
and coercive force Hc were measured. Note that the load can also be measured when it is applied directly onto the winding.

The initial magnetic permeability μ is derived from μ+ = B/H+, but here, the magnetic flux density B when H+ = 8 A/m was determined as Bi.

In addition, the coercive force HcltB=0, but H,=80A
/m.

It should be noted that the load could be sufficiently measured even with a single core made of bidirectional electrical steel sheet.

FIG. 3 shows the relationship between surface pressure and initial magnetic permeability μm, and FIG. 4 shows the relationship between surface pressure and coercive force H0. Stress is 0.1kgf/
μ2. Both of H6 show a linear relationship, approximately 10 kgf/cJ (1000 kgf/m
') We were able to measure the stress to a certain degree.

〔Effect of the invention〕

As described above, in the present invention, force is detected by electrically measuring changes in magnetic permeability or coercive force that occur when stress is applied to a bidirectional electrical steel sheet. When a load is applied to the core of a bidirectional electrical steel sheet, a compressive force acts in the thickness direction of the sheet, and this force produces a tension effect on two axes of easy magnetization that are orthogonal to each other in the sheet surface direction. Since this tension acts to subdivide the magnetic domains along the thickness direction of the bidirectional electrical steel sheet, the magnetic permeability and coercive force change depending on the core surface pressure. By utilizing this phenomenon, it is possible to detect stress or pressure with a small size and a wide measurement range.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing an embodiment of the present invention, Fig. 2 is a perspective view thereof, Fig. 3 is a graph showing the relationship between stress applied to a bidirectional electrical steel sheet and magnetic permeability, and Fig. 4 is a bidirectional 2 is a graph showing the relationship between stress applied to a magnetic steel sheet and coercive force. 1: Ring core 2 Primary winding 3: Secondary winding 4: Legs 5: Pressure receiving plate 6; DC power source 7: Magnetic flux meter Patent applicant Nippon Steel Corporation Representative Agent
Masu Kobori (and 2 others) Figure 1 Figure 3 Figure 2 Figure 4 Stress (kgf/cm')

Claims (1)

[Claims] 1. It is characterized by comprising an iron core made of a bidirectional electromagnetic steel sheet, and a detection winding that measures variations in magnetic permeability or coercive force of the iron core in accordance with the magnitude of stress applied in the thickness direction of the iron core. pressure sensor.