JPH0278926A - Pressure detector - Google Patents

Abstract

PURPOSE:To detect fine pressure with high accuracy by providing a displacement quantity detecting means in a device main body and detecting the quantity of displacement of a pressure sensing elastic body in terms of magnetic flux density, and providing a signal output circuit which leads out the output of said displacement quantity detecting means as an output voltage corresponding to pressure. CONSTITUTION:When air M is sent into the passage 6 of the device main body 1, a bellows 8 extends and deforms according to its pressure, so a magnet 10 is displaced upward in response to that. The gap G formed with a Hall element 11 varies owing to the upward displacement of the magnet 10, and consequently the magnetic flux density of a magnetic field to the Hall element 11 varies, so that the Hall element 11 varies in the level of a voltage generated at right angles to a current. An arithmetic circuit 20 extracts the voltage of the difference between the voltage and a reference voltage and the difference voltage is amplified by a DC amplifying circuit 21. Consequently, the output voltage corresponding to the pressure is generated between a couple of output terminals 22 and 23 and used for the control signal of, for example, an air blower controller.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a pressure detection device used for controlling equipment by detecting the pressure of a fluid such as gas or liquid.

<Prior art and issues> For example, in air conditioning systems, etc., a configuration is adopted that detects the air blowing pressure from a blower and controls the amount of air blowing to each room at a constant level, but depending on the scale of the system, it is difficult to detect minute pressures with high accuracy may be required.

As a conventional device of this type, there is a semiconductor diffused resistor turgor pressure sensor in which a strain gauge made of a diffused resistor is formed on the main surface of a silicon diaphragm, and deformation of the silicon diaphragm due to pressure is detected as a change in resistance value. this is,
The spring constant of the silicon diaphragm is constant and large, and it is effective in detecting pressure levels that are relatively higher than atmospheric pressure, but it has poor accuracy and is difficult to detect minute pressures at a level near atmospheric pressure of several mm 820. It is something. In order to be able to detect minute pressures, the expensive chip that makes up the silicon diaphragm must be made larger.
Significant increases in costs are unavoidable and unrealistic.

Further, even with a Bourdon tube that detects changes in the pressure inside the tube from changes in the shape of the tube, it is naturally impossible to cope with the highly accurate detection of the above-mentioned minute pressure.

<Objective of the Invention> The present invention has been made in order to solve the problems of the conventional devices described above, and an object of the present invention is to provide a pressure detection device that can easily achieve high accuracy in detecting minute pressures.

<Structure and Effects of the Invention> The pressure detection device according to the present invention includes a pressure-sensitive elastic body that is elastically deformed according to the pressure of the fluid, installed in a device main body having a passage through which fluid is taken in, and Displacement detection means for detecting the displacement of the body by converting it into a change in magnetic flux density or light intensity is disposed in the device main body, and the output from the displacement detection means is outputted by a signal output circuit corresponding to the pressure. It is designed to be extracted as voltage.

According to this invention, the amount of displacement of the pressure-sensitive elastic body can be changed into a large change in magnetic flux density using, for example, a magnet and a magnetoelectric transducer, so minute pressure can be detected without using expensive materials or special parts. can be easily realized by simply changing the spring constant by selecting the material of the pressure-sensitive elastic body, etc.
Detection accuracy is improved, and in particular, the amount of displacement of the pressure-sensitive elastic body can be detected without friction, and operability can be stabilized.

<Description of Embodiment> An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view showing an example of a pressure detection device according to the present invention.

In the figure, l is a device main body made of metal or synthetic resin, etc., and the device main body 1 consists of, for example, an upper case 2, a lower case 3 fitted to the lower surface of the upper case 2, and a structure formed in the upper case 2. and a cover 5 that closes the opening of the recess 4, and the lower case 3 is filled with a fluid such as air M
A passage 6 for taking in the water is formed from the side surface to the top surface.

7 is a space formed in the upper case 2 corresponding to the passage 6.

Reference numeral 8 denotes a pressure-sensitive elastic body disposed in the space 7 and elastically deformed by the pressure of the air M, such as a bellows made of a copper base material with thin nickel films formed on both sides thereof, and a lower peripheral edge 8a thereof. is fitted into a notch 9 formed on the lower end side of the upper case 2 and fixed to the upper surface of the lower case 3 with a clamp.

At the center of the main surface 8b of the bellows 8, a magnetic member (for example, a magnet) 10 that responds to the expansion and contraction deformation of the bellows 8 is fixed with an adhesive or the like. 11 is a magnet) 10 magneto-electric conversion elements are arranged facing each other with a gap G on the upper surface;
For example, it is a Hall element, and the amount of displacement of the bellows 8 is determined by the gap G between the magnet 10 and the Hall element 11.
This is replaced by a change in magnetic flux density due to a change in . That is, the Hall element 11 and the magnet 10 constitute a displacement detection means 12 for the pressure-sensitive elastic body 8 . Reference numeral 13 denotes a first printed wiring board on which the Hall element 11 is mounted, and is attached to a second printed wiring board, which will be described later, via hanging members 14A and 14B.

Reference numeral 15 designates a second printed wiring board, which is supported by a stepped portion 16.17 formed on the inner wall of the recess 4, and a circuit constituting the signal output circuit 18 shown in FIG. 2 is mounted on the side surface. Element 19 is attached. The signal output circuit 18 is
For example, as shown in FIG. 2, an arithmetic circuit 20 that detects a change in the output of the Hall element 11 due to a change in the magnetic flux density;
DC amplifier circuit 2 that amplifies the output from this arithmetic circuit 20
1, and the output of the DC amplifier circuit 21 is taken out to a pair of output terminals 22 and 23 as an output voltage corresponding to the pressure. 24 is a constant voltage circuit that supplies a constant voltage to the strain gauge 14;

25 is a power supply terminal, and 26 and 27 are resistors for setting the reference voltage of the arithmetic circuit 20.

In FIG. 1, 28 is a signal sending cable connected to the printed wiring board 15, and 29 is formed at the entrance port 6a of the passage 6, into which an air supply pipe joint (not shown) is screwed. It is a threaded part that is connected by

Next, the operation of the above configuration will be explained.

When air M is taken into the passage 6 of the device main body l, the bellows 8 expands and deforms according to the pressure, so the magnet)
10 is also displaced upward in response to this. magnet 10
Due to the upward displacement of G, the gap G between the Hall element 11 and
As a result, the magnetic flux density of the magnetic field to the Hall element 11 changes, and the voltage Vl generated in the Hall element 11 in a direction orthogonal to the current changes. By the arithmetic circuit 20,
After the voltage difference between the voltage Vl and the reference voltage v2 is extracted, it is amplified by the DC amplifier circuit 21. That is, as a result, an output voltage corresponding to the pressure is generated between the pair of output terminals 22 and 23 according to the characteristics shown in FIG. used.

Here, since the amount of displacement of the bellows 8 subjected to the pressure of the air M is detected by replacing it with a large change in magnetic flux density using the magnet 10 and the Hall element 11, the configuration is relatively simple, and It can easily cope with the detection of minute pressures of about several mmH20, and moreover, it can be obtained at a lower cost than those using conventional silicon diaphragms or the like.

Further, by simply changing the spring constant by selecting the material of the bellows 8, the detection range can be adjusted, and high precision detection can be achieved.

Furthermore, since there is no contact between the magnet 10 provided on the bellows 8 and the Hall element 11, both io, tt
There is no friction between the two, thus ensuring a stable detection operation.

Of course, the present invention is not limited to the Hall element 11 described above, and other magnetoelectric conversion elements may be used.

Further, the means 12 for detecting the amount of displacement of the bellows 8 includes:
Not limited to the above, those that use a differential transformer,
It is also possible to adopt other configurations, such as one in which the amount of received light is changed by intervening optical means.

Furthermore, in the above embodiment, the bellows 8 is used as the pressure sensitive elastic body.
However, similar effects can be achieved using other pressure-sensitive elastic bodies such as diaphragms.

Furthermore, although the above embodiments have been described for detecting the gas pressure of air, the present invention can also be applied to detecting the pressure of other fluids such as liquids.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an example of a pressure detection device according to the present invention, Fig. 2 is a block diagram showing a signal output circuit etc. for extracting the output of a strain gauge in the same device, and Fig. 3 shows pressure and output voltage. FIG. DESCRIPTION OF SYMBOLS 1... Apparatus body, 8... Pressure-sensitive elastic body, 12... Displacement detection means, 18... Signal output circuit, M... Fluid. Figure 1 M:i(, $.

Claims (1)

[Claims] (1) A device body having a passage through which fluid is taken in;
A pressure-sensitive elastic body is installed in the device body and elastically deforms according to the pressure of the fluid; A pressure detection device comprising: a displacement amount detection means for detecting the displacement amount; and a signal output circuit for taking out an output from the displacement amount detection means as an output voltage corresponding to the pressure.