JPH05288620A - Pressure sensor - Google Patents

Abstract

PURPOSE:To obtain a pressure sensor which achieves high measuring accuracy in a measuring range and moreover, eliminates damage that may be caused when a fluid to be measured reaches a pressure exceeding the upper limits of the measuring range. CONSTITUTION:This apparatus is provided with a diaphragm 2 which comprises a flexible thin film arranged with the surface thereof facing a fluid to be measured, a piston body 7 arranged on the rear side of the diaphragm 2 and an energizing means 18 to energize the piston body 7 from the rear side. Moreover, a liquid 9 sealed between the diagram 2 and the piston body 7 and a pressure detector 10 for detecting the pressure of the liquid 9 are so arranged that the liquid 9 can pass freely between the diaphragm 2 and the piston body 7 and a passing liquid stopper 17 is provided to let the rear of the diaphragm 2 get tight almost over the entire surface thereof when the pressure of the fluid to be measured exceeds a specified value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor for measuring the pressure of fluid.

[0002]

2. Description of the Related Art A pressure sensor may be subjected to a pressure higher than the upper limit of the pressure range to be measured from the fluid to be measured side. Even in such a case, it is inconvenient if the pressure sensor is damaged. is there.

Therefore, conventionally, for example, in a pressure sensor using a pressure detector in which a piezoresistor is formed on a silicon single crystal substrate, the strength of the pressure detecting portion is increased by thickening the silicon single crystal substrate to increase the measurement pressure range. Even when a pressure exceeding the upper limit of was applied, it was able to withstand it.

[0004]

However, if the thickness of the silicon single crystal substrate is increased, the amount of deformation of the silicon single crystal substrate with respect to the pressure change of the fluid to be measured becomes small and the sensitivity is lowered. There is a drawback that the measurement accuracy in the range becomes poor.

Therefore, an object of the present invention is to provide a pressure sensor which has a high measurement accuracy in the measurement range and which is not damaged even when the fluid to be measured has a pressure exceeding the upper limit of the measurement range.

[0006]

In order to achieve the above object, a pressure sensor of the present invention comprises a diaphragm made of a flexible thin film arranged so that its surface faces the fluid to be measured.
A piston body arranged on the back side of the diaphragm,
A biasing means for biasing the piston body from the back side, a liquid sealed between the diaphragm and the piston body, a pressure detector for detecting the pressure of the liquid, the diaphragm and the piston body. And a liquid passage stopper arranged so that the liquid can freely pass therethrough, and the back surface of the diaphragm comes into close contact with the substantially entire surface when the pressure of the fluid to be measured exceeds a predetermined pressure. It is characterized by being provided.

[0007]

[Function] The pressure of the fluid to be measured is received by the diaphragm,
The liquid enclosed between the diaphragm and the piston body also has the same pressure, and the pressure is detected by the pressure detector.

When the pressure of the fluid to be measured becomes larger than the urging force of the urging means, the diaphragm and the piston body start to be pushed down as a whole with the liquid sealed between them. Then, when the pressure of the fluid to be measured reaches a predetermined pressure which is the upper limit of the measurement range, the back surface of the diaphragm comes into close contact with the stopper surface,
Even if the pressure of the fluid to be measured rises further, the diaphragm cannot be displaced any further.

Therefore, the pressure exceeding the above-mentioned predetermined pressure is not applied to the enclosed liquid and the pressure detector for detecting the pressure thereof.

[0010]

Embodiments will be described with reference to the drawings. FIG. 1 shows a pressure sensor, and a fluid to be measured is introduced into the pressure measurement port 1. A diaphragm 2 made of a flexible thin film is arranged facing the pressure measurement port 1 so that the front surface faces the fluid to be measured, and its outer edge portion is watertightly sealed by O-rings 3 and 4 from both front and back surfaces. Has been done.

The housing 6 for pressing the outer edge of the back surface of the diaphragm 2 is formed in a cylindrical shape, and a piston body 7 made of an electrically insulating material is arranged inside the housing 6 so as to face the back surface of the diaphragm 2 and move back and forth. Has been done. An O-ring 8 seals between the outer surface of the piston body 7 and the inner surface of the housing 6.

A liquid 9 such as silicon oil is enclosed in the space between the diaphragm 2 and the piston body 7, and no gas such as air exists in this space. A pressure detector 10 for detecting the pressure of the liquid 9 is attached to the upper surface of the piston body 7 facing the liquid 9.

This pressure detector 10 forms a piezoresistor on the surface of the silicon single crystal substrate 11 and detects the deformation amount of the silicon single crystal substrate 11 by the piezoresistive effect to detect the pressure of the liquid 9. is there. Since silicon oil is used as the liquid 9, the silicon single crystal substrate 1
The liquid 1 is not corroded by the liquid 9.

Output signal (voltage) from the pressure detector 10
Is output from the output terminal 14 to the outside through the circuit board 13 on which the amplifier circuit and the like are formed. 15 is a positive electrode terminal, 1
6 is a negative electrode terminal.

The space between the diaphragm 2 in which the liquid 9 is enclosed and the piston body 7 is formed of a liquid-permeable material such as sintered metal, and the diaphragm 2
A stopper plate 17 that allows the liquid 9 to freely pass between the side and the piston body 7 side is fixed to the housing 6.

Further, the rear surface of the piston body 7 and the housing 6
A compression coil spring 18 is mounted between the piston body 7 and the bottom of the stopper plate 17 and is stopped by the compression coil spring 18 while being pressed against the back surface of the stopper plate 17 by a predetermined urging force.

FIG. 2 is a diagram showing the operation of the above embodiment, in which the measured fluid pressure is not so high that the pressure of the liquid 9 acting on the piston body 7 is smaller than the urging force of the compression coil spring 18. Then, the measured fluid pressure is the same as the pressure of the liquid 9 sealed inside the diaphragm 2 as in O-A of (a), and the pressure signal between them is as shown in (b). The output is linear with pressure changes,
As shown in (c), the piston body 7 does not move during that time.

When the fluid pressure to be measured rises and the pressure of the liquid 9 acting on the piston body 7 becomes larger than the urging force of the compression coil spring 18, as shown in FIG.
Starts moving in the direction of compressing the compression coil spring 18.

At this time, the liquid 9 moves from the diaphragm 2 side to the piston body 7 side through the stopper plate 17.
Then, the pressure rise of the liquid 9 becomes gentler than the fluid pressure to be measured, such as between A and B in (a), and the pressure signal output is always the pressure of the liquid 9 as shown in (b). On the other hand, it is linear.

When the measured fluid pressure reaches the upper limit pressure required for measurement, as shown in FIG. 3, the back surface of the diaphragm 2 comes into close contact with the surface of the stopper plate 17, and the diaphragm 2 cannot move any more.

Then, as shown in FIG.
No matter how much the pressure of the fluid to be measured in the pressure measurement port 1 rises, the pressure of the liquid 9 inside the diaphragm 2 does not change, and therefore the pressure signal output also changes as shown in (b). Instead, the piston body 7 also remains stopped as shown in (c).

FIG. 4 shows a second embodiment of the present invention, in which the diaphragm 2 uses a flexible thin metal plate. Further, the surface of the stopper plate 17 is formed by slightly recessing the inside. Even with this configuration, the operation is exactly the same as in the first embodiment.

FIG. 5 shows a third embodiment of the present invention, which incorporates an electric switch 20 for transmitting the movement of the piston body 7 to the outside when the piston body 7 is moved. The electric switch 20 is pushed by the piston body 7 to close when the pressure reaches the upper limit of the measurement range.

The present invention is not limited to the above embodiment, for example, the pressure detector 10 may be provided in a place other than the piston body 7, and instead of the compression coil spring 18,
It is also possible to use an inversion leaf spring or the like that inverts when the load exceeds a certain level.

[0025]

According to the pressure sensor of the present invention, even if the pressure of the fluid to be measured exceeds the pressure range required to be measured, the pressure detector does not receive a pressure higher than the required measurement pressure. Does not break, and the pressure detector only needs to have the strength to withstand the pressure in the pressure range that needs to be measured, and it does not need to be made stronger than necessary, so the sensitivity in the required pressure range is high. It is possible to have high and excellent measurement accuracy.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a first embodiment.

FIG. 2 is a diagram showing the operation of the first embodiment.

FIG. 3 is a vertical cross-sectional view of the first embodiment.

FIG. 4 is a vertical sectional view of a second embodiment.

FIG. 5 is a vertical sectional view of a third embodiment.

[Explanation of symbols]

 2 Diaphragm 7 Piston body 9 Liquid 10 Pressure detector 17 Stopper plate 18 Compression coil spring

Claims (1)

[Claims] 1. A diaphragm made of a flexible thin film, the surface of which faces the fluid to be measured, a piston body arranged on the back side of the diaphragm, and a biasing means for urging the piston body from the back side. A biasing means, a liquid enclosed between the diaphragm and the piston body, a pressure detector for detecting the pressure of the liquid, and the liquid passing freely between the diaphragm and the piston body. A pressure sensor, which is provided so as to be capable of being provided, and which is provided with a liquid passage stopper arranged so that the back surface of the diaphragm is brought into close contact with substantially the entire surface when the pressure of the fluid to be measured exceeds a predetermined pressure.