JPS5873835A - Pressure transmitter - Google Patents

Abstract

PURPOSE:To facilitate the manufacture and assembly while ensuring the protection from overloading by preventing a seal disphragm from seating on the body to avoid the application of overload pressure on a pressure detecting element through cooperation with a adjusting diaphragm. CONSTITUTION:When working on a seal diaphragm 24, a pressure P is transmitted to a semiconductor pressure detecting element 34 through a non-compressive liquid 40 sealed into a fluid chambers 28, 36 and a fluid path 38, where the pressure is detected depending on variation in the resistance of a piezo-electric resistance element formed in the element 34. As the measured pressure increases, the sealed liquid 40 in a liquid chamber 28 moves gradually to the fluid chamber 36 to deform an adjusting disphragm 32. This prevents the seal diaphragm 24 from seating on a corrugated wall 26 to avoid the application of overload on the element 34 immediately before the pressure reaches the allowable limit of the element 34 thereby ensuring protection from overloading while facilitating the manufacture and assembly.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a pressure transmitter that uses a semiconductor pressure detection element to convert fluid pressure or a differential pressure between two fluid pressures into an electrical signal and transmit the electrical signal. In particular, the present invention relates to an overload protection device for a semiconductor pressure detection element.

[Prior art]

Since the deformation of the detection portion of a semiconductor pressure detection element is extremely small, it is necessary to protect the semiconductor pressure detection element from being subjected to overload pressure when the pressure is applied.

For this reason, as shown in the first example, by bringing the center plate 4 of the seal diaphragm 2 into contact with the O-ring 8 provided on the main body 6, the sealed liquid can be removed. A method of stopping the movement of 0 is generally adopted. However, as mentioned above, since the deformation of the semiconductor pressure sensing element 12 is extremely small, the amount of movement of the sealed liquid is similarly small, and unless the gap between the center plate 4 and the O-ring 8 is made extremely small, overloading may occur. It is not possible to practice Hoken.

Therefore, in the configuration shown in FIG.
It has the disadvantage that it is extremely difficult to adjust the IE.

[Object of the Invention] An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to provide a pressure transmitter equipped with an overload protection device that is easy to manufacture and assemble.

[Summary of the invention]

To achieve the above object, the pressure transmitter of the present invention is provided with an Fi adjustment diaphragm. The regulating diacrum is configured to be applied with fluid pressure in the same manner as the pressure sensing element. - When overloaded, the joint diaphragm seats the seal diaphragm on the main body to prevent overload pressure from being applied to the pressure detection element.

[Embodiments of the invention]

Hereinafter, one example of the present invention will be explained based on the drawings.

In Fig. 2, the pressure section main body 2 having 7 flange 20A
0Kit, a pressure guiding port 22 for the measurement fluid and a seal diaphragm 24 are provided, and the wall facing the seal diaphragm 24 is a corrugated wall 26, and the seal dia 7.9 mm 24
A first fluid chamber 28 is formed between the first waveform 1126 and the third waveform 1126. Pressure detection cord...
Note t11. .

The body 30 is provided with an adjustment diaphragm 32, and a semiconductor pressure detection element 34 is provided in the center of the adjustment diaphragm 32.
is provided. A second fluid chamber 36 is formed between the pressure detection section main body 30 and the adjustment diaphragm 32. The first fluid chamber 2B and the second fluid chamber 36 are connected to a fluid passage 38.
1. The second fluid chamber 28.86 and the fluid passageway 38 are filled with an incompressible fill liquid 40.

42 is a diaphragm that absorbs fluid pulsation.

Next, the operation will be explained. When pressure p acts on the seal diaphragm 24, the pressure is applied to the first and second fluid chambers 2.
8.36 and the fluid passageway 38, and is transmitted to the semiconductor pressure sensing element 34 via a compressible filling liquid 40. In proportion to this, the piezoresistive element formed by the selective diffusion method in the semiconductor pressure detection element 34 causes a resistance change, so that the pressure can be determined from this. The pressure within the second fluid chamber 36 is equal to or less than the seal diaphragm 24.
□ It is determined by the rigidity ratio of the joint diaphragms 3...2, but if the rigidity of the seal diaphragm 79)"m"24 is made extremely small, the fluid chamber 2' will be closed! , the pressure within can be made almost equal to the measured pressure p. As the measuring pressure increases, the rattan l
The sealed liquid in the fluid chamber 28 of gz gradually flows into the fluid chamber 36 of gz.
The adjustment diaphragm 32 is deformed. Therefore, if the seal diaphragm 24, the gap between it and the waveform 1i26, and the rigidity of the adjustment diaphragm 72m 32 are appropriately designed,
Immediately before the measured pressure p reaches the allowable limit pressure of the semiconductor pressure detection element 34, the seal diaphragm 24 seats on the waveform 1126, and the pressure no longer reaches the second fluid chamber 36. Therefore, even if excessive pressure is applied to the pressure guiding port 22, the semiconductor pressure detection element 34 and the adjustment diaphragm 32 will not be damaged. Furthermore, by appropriately designing the size of the orifice 42), if the measured pressure p includes a pulsation component, it is possible to attenuate this pulsation component, and the second fluid chamber 36
The smoothed pressure is transmitted to the Therefore, it is possible to reduce the vibration load on the pressure detection cable 34, and the life of the pressure detection cord 34 can be greatly extended.

FIG. 3 is a principle diagram showing another embodiment of the present invention, and the same parts as in FIG. 2 are designated by the same reference numerals. The difference from FIG. 2 is that the mounting base 44 to which the semiconductor pressure detection element 34 is fixed is fixed to the pressure detection section main body 30 or is structured integrally with the main body. In the configuration shown in the alEZ diagram, since the natural frequency of the adjustment diaphragm 32 is low, the natural frequency of the entire body including the mounting base 44 and the semiconductor pressure detection element 34 mounted thereon is also low, and the disadvantage is that it is vulnerable to external vibration. However, in the configuration shown in FIG. 3, the mounting base 44 is fixed to the pressure detection section main body 30 or is integrated with the main body 30, so the natural frequency & I number of the entire structure including the semiconductor pressure detection element 34 is high. It has the advantage of being resistant to external vibrations.

[Efficacy of invention]

According to the present invention, the seal diaphragm and the adjustment diaphragm can cooperate with each other, and the seal diaphragm is seated on the main body to prevent overload pressure from being applied to the semiconductor pressure sensing element. Therefore, a pressure transmitter that can easily and reliably maintain overload can be obtained.

[Brief explanation of the drawing]

tj&1- is a sectional view of a pressure transmitter having a conventional overload protection device, FIG. 2 is a sectional view of a pressure transmitter having an overload protection device according to the present invention, and the third factor is a partial modification of FIG. 2. An example is shown in sectional view. DESCRIPTION OF SYMBOLS 20... Pressure receiving part main body, 22... Pressure guiding port, 24 River seal diaphragm, 26... Corrugated wall, 28... First fluid chamber, 30... Pressure detecting part main body, 32...・Adjustment diaphragm, 34...Semiconductor pressure detection element, 36.
...Second fluid chamber, 38...Fluid passage, 40...Filled liquid. 〉L, 1 certain 1 ω certain 2 mouth

Claims (1)

[Claims] 1. A seal diaphragm attached to the body with a gap therebetween and forming a first fluid chamber between the body and the body; 9 attached to the body with a gap between the seal diaphragm and the body; a regulating diaphragm forming a second fluid chamber; a fluid passage connecting the first fluid chamber and the second fluid chamber; a semiconductor pressure sensor attached to the main body and converting fluid pressure into an electrical signal; Element, the above-mentioned collection 1. A pressure transmitter comprising a second fluid chamber and a liquid sealed in a fluid passage, wherein the seal diaphragm is configured to sit on the main body when overload pressure is applied.