JPS63235840A - Pressure sensor - Google Patents

Abstract

PURPOSE:To enable highly reliable measurement of pressure with limited errors, by arranging a diaphragm, a pair of magnets, a magnetosensitive element and the like. CONSTITUTION:When a gas or liquid intended to measure pressure is taken into a pressure detection chamber P at a pressure detection port 31, the center 42 of a diaphragm 4 is displaced vertically according to the size of pressure of the gas or liquid and at the same time, a pair of magnets 7 and 8 are driven. Consequently, relative position between the magnets 7 and 8 and Hall element 9 changes, which causes a change in the intensity of a magnetic field working on the element 9 to vary an output voltage of the element 9. Therefore, pressure can be measured from the output voltage of the element 9 by obtaining relationship between the size of the pressure working on the diaphragm 4 and the output voltage thereof 9 beforehand. With the magnets 7 and 8 magnetized reversely in the polarity to each other, changes in the intensity of a magnetic field roughly vertical to opposed surfaces 71 and 81 becomes smaller than would be when one magnet is used. This enables measurement of pressure with limited errors.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a pressure sensor that includes a diaphragm to which a pair of magnets are attached and a Hall element and detects the pressure of gas or liquid.

<Prior Art> As a pressure sensor for detecting the pressure of gas or liquid, pressure sensors having the following configuration have conventionally been used. That is, a single magnet is attached to a diaphragm whose central portion is displaced by the above pressure, and a magnetically sensitive element, such as a Hall element, is arranged near the magnet.

With the above configuration, as the magnet is displaced together with the diaphragm, the relative position between the magnet and the Hall element changes, depending on the strength of the magnetic field or the magnitude of the pressure applied to the Hall element.

Then, since the Hall element outputs a voltage according to the strength of the magnetic field, the pressure can be measured from the output voltage.

<Problems to be Solved by the Invention> However, since the displacement of the magnet attached to the diaphragm is accompanied by vibration, the magnitude of pressure does not correspond accurately to the strength of the magnetic field relative to the magnetic sensing element. That is, the output from the Hall element for a constant pressure does not have a constant value but varies, causing a large error in pressure measurement.

Means for Solving the Problems> The present invention was proposed to solve the above problems, and consists of a diaphragm whose peripheral edge is attached to a case and whose central portion is displaced by the pressure of gas or liquid, and an opposing surface. a pair of magnets attached to the diaphragm with the magnets substantially perpendicular to the diaphragm; and a magnetically sensitive element supported by the case and loosely inserted between opposing surfaces of the pair of magnets. It is a pressure sensor consisting of. Furthermore, the pair of magnets are magnetized on the opposing surfaces in a direction substantially perpendicular to the diaphragm, and are opposed to each other with opposite polarities.

Effect> With the above configuration, the change in the strength of the magnetic field in the direction substantially perpendicular to the magnetized opposing surface becomes extremely small. Therefore, even if the pair of magnets is moved in a direction substantially perpendicular to the facing surfaces, the variation in the output voltage of the Hall element is very small, and an almost constant output voltage is always obtained for a constant pressure. That is, the error in pressure measurement becomes extremely small.

<Example> An embodiment of the present invention will be described below based on one drawing.

FIG. 1 is a schematic side sectional view of the pressure sensor.

As shown in the figure, the pressure sensor l includes a substantially cylindrical case 2,
The case 2 is covered by a two-piece 3 which is airtightly attached to the upper end of the case 2. A substantially cylindrical pressure detection port 31 is formed on the top surface of the top lid 3 .

A peripheral edge 41 of a diaphragm 4 is airtightly attached to the upper edge of the case 2, and a pressure detection chamber P is formed between it and the upper lid 3. The diaphragm 4 is made of a highly elastic material such as rubber, and has a thick central portion 42 and a peripheral portion 43 that is thin and bulges downward to increase elasticity.

Further, the upper end of the magnet case 6 is attached to the lower surface of the center portion 42 of the diaphragm 4 with screws T, with the center portion 42 being sandwiched between the sandwiching plate 5 and the magnet case 6.

And inside the magnet case 6 that opens downward,
A pair of rod-shaped magnets 7 and 8 facing each other are placed on the facing surface 7.
1.81 is attached substantially perpendicular to the diaphragm 4. The pair of magnets 7.8 are arranged on opposing surfaces 71.81 in a direction substantially perpendicular to the diaphragm 4.
They are magnetized and are opposed to each other with opposite polarities. That is, for example, if the upper part of one opposing surface 71 is set as the N pole and the lower part is set as the S pole, the upper part of the other opposing surface 81 is set as the S pole.
The pole is the north pole at the bottom.

Note that the pair of magnets 7, 8 are two magnets 72.73 and 82.8:l magnetized in a direction substantially perpendicular to the opposing surface 71.81, as shown in the schematic side view of FIG. They may be connected by metal plates 74 and 84 with their polarities reversed, and may also be opposed to each other with their polarities reversed.

On the other hand, a support stand G is fixed to the bottom of the case 2.
A magnetically sensitive element, for example, a Hall element 9 is attached to the tip of the support rod g erected on the upper surface of the support base G, and the opposing surface 71.81
It is installed loosely inserted between the two. The Hall element 9 outputs a voltage corresponding to the strength of the magnetic field applied to the Hall element /-9.

Next, the operation of the pressure sensor I having the above configuration will be explained.

That is, the pressure of the gas or liquid whose pressure is to be measured is detected by pressure r+3.
1 into the pressure detection chamber P, the center 42 of the diaphragm 4 is displaced in the vertical direction, that is, in a direction substantially perpendicular to the diaphragm 4, depending on the magnitude of the pressure of the gas or liquid, and at the same time, the pair of magnets 7 .8 or follow. Then, the relative position between the pair of magnets 7 and 8 and the Hall element 9 changes, and the strength of the magnetic field applied to the Hall element 9 changes. The output voltage of the Hall element 9 changes accordingly. Therefore, if the relationship between the magnitude of the pressure applied to the diaphragm 4 and the output voltage of the Hall element 9 is determined in advance, the pressure can be measured from the output voltage.

In addition, by providing the pair of magnets 7.8 magnetized as described above with opposite polarities, the change in the strength of the magnetic field in the direction approximately perpendicular to the facing surfaces 71, 81, - magnets It is much smaller than when using .

FIG. 3 is a diagram for explaining the above effect, and solid lines A and B in the diagram indicate the Hall elements 9 inserted between the opposing surfaces 71.81 by a certain amount from the lower ends of the pair of magnets 7.8. , facing surface 7
1.81, which represents the change in the output voltage E of the Hall element 9 when it is moved in a substantially perpendicular direction. The horizontal axis is one opposing surface 71
or distance from 81, and the vertical axis is the output voltage E of the Hall element 9. Also, broken lines a and b in the figure indicate either one of the magnets 7.
Or, 8 times are provided, and the changes in the output voltage E are shown when the Hall element 9 is moved in the same manner as above.

As shown in the figure, the changes in the vertical axis direction of solid lines A and B are broken lines a,
This is very small compared to the change in b in the same direction. That is, when the pair of magnets 7 and 8 are provided as described above, the opposing surfaces 71 .
Since the change in the strength of the magnetic field in the direction approximately perpendicular to 81 is very small, the change in the output voltage E of the Hall element 9 when the Hall element 9 is moved in the same direction is smaller than when using a single magnet. becomes very small.

Therefore, the pair of magnets 7, 8 and the opposing surfaces 71.81 and approximately +'
Even when turned in the vertical direction, the variation in the output voltage of the Hall element 9 is very small, and an almost constant output voltage is always obtained for a constant pressure. In other words, the above configuration can greatly reduce errors in pressure measurement.

Furthermore, regarding the vibration of the pair of magnets 7 and 8 in a direction substantially parallel to the opposing surfaces 71 and 81 and substantially perpendicular to the magnetization direction,
By increasing the length of the facing surfaces 71, 81 in the same direction to a certain extent, it is possible to reduce changes in the strength of the magnetic field in the same direction, thereby suppressing fluctuations in the output voltage of the Hall element 9.

<Effects of the Invention> As described above, according to the pressure sensor of the present invention, highly reliable pressure measurement with very small errors is possible.

[Brief explanation of the drawing]

Fig. 1 is a schematic side cross-sectional view of a pressure sensor, Fig. 2 is a schematic side view showing another example of a pair of magnets, and Fig. 3 is a side view schematically showing another example of a pair of magnets. FIG. 3 is a diagram showing changes in the output voltage of the Hall element over time. l...pressure sensor, 2...case. 4...Diaphragm, 41...Periphery. 42...Center, 7.8...Magnet. 71, 81... Opposite surface. 9...Hall element (magnetically sensitive element). Patent applicant Nippon Aleph Co., Ltd. Patent attorney Kuninori Funa Hashi Figure 1 Figure 2

Claims (1)

[Claims] a diaphragm whose peripheral edge is attached to a case and whose center is displaced by the pressure of gas or liquid; a pair of magnets attached to the diaphragm with opposing surfaces substantially perpendicular to the diaphragm; and a magnetically sensitive element supported by the case while being loosely inserted between the opposing surfaces of magnets, the pair of magnets being inserted between the opposing surfaces in a direction substantially perpendicular to the diaphragm. 1. A pressure sensor characterized in that the pressure sensors are magnetized and faced to each other with opposite polarities.