JPH0731088B2 - Pressure sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] A pressure sensor is provided with means for passing a magnetic flux through a closed magnetic circuit that can be reversibly deformed by a contact pressure and measuring a leakage magnetic field thereof, so that the closed magnetic circuit is deformed by a contact pressure. It is possible to detect the contact pressure on the closed magnetic circuit by capturing the leakage current as a change in the leakage magnetic field.

[Industrial application field]

The present invention relates to a pressure sensor used in fields such as factory automation.

[Conventional technology]

In recent years, sensors for detecting tactile pressure when grasping an object have been used in the field of factory automation and the like, and one of them is by magnetic means. FIG. 7 is a diagram showing a conventional pressure sensor using magnetic means. This is one in which a plurality of permanent magnets 1 are oriented and a rubber plate 3 on which a magnetoresistive element 2 is arranged so as to face the permanent magnets 1 is provided on a substrate 4, and when the contact pressure P is applied to the permanent magnets 1. The contact pressure can be measured by detecting a change in the output of the magnetoresistive element 2 due to a change in the distance between the magnetoresistive element 2 and the magnetoresistive element 2.

[Problems to be solved by the invention]

The conventional pressure sensor described above has a drawback that the relative position between the magnetoresistive element 2 and the permanent magnet 1 changes due to slippage or the like.

The present invention was created in view of these points.
It is an object of the present invention to provide a pressure sensor that can accurately detect pressure with a simple structure.

[Means for solving problems]

FIG. 1 is a diagram for explaining the principle of the pressure sensor of the present invention.

In FIG. 1a, 10 and 10 'are ferromagnetic plates forming a closed magnetic circuit, and in particular, 10 has a structure that is reversibly deformed by external pressure. Reference numerals 11, 11 'are permanent magnets or electromagnets that give a magnetic flux to the closed magnetic path, and 12, 12', 12 "are magnetic field detectors for detecting a leakage magnetic field. Fig. 1a shows the case where there is no external pressure. The magnetic flux from one magnet 11 (11 ') is a closed magnetic circuit.
It passes through 10 (10 ') and reaches the opposing magnet 11 (11'). At this time, magnetic flux leaks from the magnetic paths 10 to 10 'and from the magnetic paths 10' to 10, and the magnetic fields cancel each other out at the central portion and become zero, but become larger toward the ends and have opposite polarities at both ends. When this magnetic field is measured, it becomes as shown by the curve A in FIG.

[Work]

FIG. 1b shows a state in which an external pressure or a negative pressure is applied to the magnetic path 10. When the external pressure is applied, the magnetic path 10 bends inward, and near the center, it approaches the opposing magnetic path 10 ', so that the leakage magnetic field is large. Become. Although the central magnetic field cancels out to zero, the outputs (and output difference) of the detectors 12 'and 12 "farther from the center increase, as shown by curve B in FIG. 1c. Also, when a negative pressure is applied to the magnetic path 10, the output (and the output difference) of the detectors 12 'and 12 "becomes smaller as shown by the dotted line in FIG. It becomes as shown by C.

Thus, the detectors 12 ', 1
Since the output of 2 ″ (and the output difference) reflects the bending of the magnetic path 10, that is, the magnitude of the external pressure, the external pressure can be measured by the outputs of the detectors 12 ′ and 12 ″.

〔Example〕

 FIG. 2 is a diagram showing a first embodiment of the present invention.

In this embodiment, a magnetic stainless steel or permalloy (15 × 100 mm) plate having a thickness of 0.3 mm is used for the magnetic paths 10 and 10 ′, and the magnets 11 and 11 ′ which give a magnetic flux remain with a size of 5 × 20 × 15 mm. Magnetic flux density ~ 12.5KG, Curie temperature ~ 600 ℃ alnico magnet (Fe-N
(i-Co-Al alloy), the left and right magnets 11 and 11 'are arranged so that their polarities are opposite to each other, and a detector 1 for detecting a leakage magnetic field is used.
A barber pole type magnetoresistive element or Hall element (GaAs, InSb, etc.) that can detect the magnitude of the magnetic field is used as 2 ', 12 ", and two detectors 12', 12" are placed at the center of the closed magnetic path 10, 10 '. They are placed symmetrically with respect to each other, about 40 mm apart. Reference numeral 13 is a slip stopper using a rubber plate or the like.

According to the present embodiment thus configured, the output difference when the external pressure is not applied is 0.74 mV (100 times amplification) as shown in FIG. 3, but the maximum output when the positive or negative pressure is applied. Each difference
It was 1.12mV and 0.40mV.

FIG. 4 is a diagram showing a second embodiment of the present invention. In this embodiment, as shown in the figure, a magnet 11 is arranged only on one side of the closed magnetic paths 10 and 10 ', and a soft magnetic material or a non-magnetic material 14 is arranged on the other side instead of the magnet, and a detector for detecting a leakage magnetic field is provided. Since only one 12 is arranged, an effect similar to that of the previous embodiment can be obtained.

FIG. 5 is a diagram showing a third embodiment of the present invention.

In this embodiment, a plurality of elements of the embodiment shown in FIG. 1 are arranged so that the pressure distribution can be measured. Magnet in this case
11 to 11 'can be shared by adjacent magnetic paths.

FIG. 6 is a diagram showing a fourth embodiment of the present invention. In this embodiment, a chamber 15 is further provided on the magnetic path 10 side in the configuration shown in FIG. 2, and the pressure when the pressure in the chamber 15 becomes negative or positive is measured, and the degree of vacuum is measured. Alternatively, the gas pressure can be measured. A non-magnetic material is used as the material forming the chamber 15. Although an alnico magnet is used as the magnet in each of the above embodiments, a rubber magnet in which ferromagnetic powder or the like is oriented may be used.

〔The invention's effect〕

As described above, according to the present invention, the slip between the magnet and the detector when rubber is used has a very simple structure including the closed magnetic circuit made of metal and the magnetic field detector for detecting the leakage magnetic flux. Since it is possible to perform accurate pressure measurement without any problems, it is extremely useful in practice.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the principle of a pressure sensor of the present invention, FIG. 2 is a perspective view showing a first embodiment of the present invention, and FIG. 3 is a diagram showing deflection of a magnetic path and output difference. FIG. 4 is a diagram showing a second embodiment of the present invention, FIG. 5 is a diagram showing a third embodiment of the present invention, FIG. 6 is a diagram showing a fourth embodiment of the present invention, and FIG. The figure shows a conventional pressure sensor using magnetic means. In FIGS. 1 to 6, 10 and 10 'are magnetic paths, 11, 11', 11 ", 11 and 11 'are magnets, and 12, 12' and 12" are magnetic field detectors.

Claims (2)

[Claims] 1. A pair of magnetic paths (10, 10 ') made of metal, which can be reversibly deformed by contact pressure, and one or a plurality of magnets () for giving a magnetic flux to the magnetic paths (10, 10'). 11, 11 ') and a magnetic field detector (1 for detecting magnetic flux leaking from the magnetic path (10, 10').
2, 12 ') and a pressure sensor. 2. A plurality of magnetic field detectors (12 ', 12 ") detect a leakage magnetic field at a position away from the center, and the detectors (12', 1").
The pressure sensor according to claim 1, wherein the pressure is detected by the output difference of 2 ″).