JPH0353139A - Pressure cell for differential pressure transmitter - Google Patents

Abstract

PURPOSE:To improve the pressure resistance to measure a high differential pressure by adopting the structure where a force is not applied to the weld around a sensor at the time of applying an excessive differential pressure. CONSTITUTION:A pressure cell has a two-diaphragm structure consisting of a high pressure-side seal diaphragm 4a and a low pressure-side seal diaphragm 4b, and pressures introduced to the high pressure side and the low pressure side are transmitted to both faces of a semiconductor sensor 1 through diaphragms and sealed liquid 5, and the differential pressure is converted to an electric signal. The upper face part of a housing 8 in which the sensor 1 is stored is fitted to a high pressure-side pressure receiving part main body 6 and is supported by a part (a) and is welded in a part (b). The lower face part of the housing 8 is supported through a member 10 by a part (c) and is welded in parts (d) and (e). By this structure, the force in the axial direction generated in the housing 8 and the member 10 at the time of applying the differential pressure is supported by parts (a) and (c) to prevent the generation of stress in welded parts (b) and (d), and the part (e) is deeply welded to give a sufficient strength to this part (e) against the excessive differential pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a differential pressure transmitter, particularly a high differential pressure transmitter that is effective for detecting high differential pressures.

[Conventional technology]

A conventional differential pressure transmitter has a configuration as schematically shown in FIG. 3. Reference numeral 61 indicates a semiconductor sensor formed by diffusing a gauge resistor into a silicon diaphragm, and reference numeral 14 indicates a semiconductor sensor for extracting a signal from the semiconductor sensor to the outside. hermetic seal part, 1
5 is a center diaphragm that serves to protect the semiconductor sensor from excessive differential pressure; 4a is a high-pressure side seal diaphragm; 4b is a low-pressure side seal diaphragm; 5 is a sealed liquid; 6
is the body. Here, conventional differential pressure transmission lines measure small differential pressures that occur under high static pressure, so they are not affected by static pressure fluctuations. For example, it has a structure that is less susceptible to static pressure fluctuations due to deformation of the pressure receiving part body,
The sensor support structure is such that deformation of the main body due to static pressure is not transmitted to the semiconductor sensor, and the semiconductor sensor is equivalently structured to float in the filled liquid. In addition, when excessive differential pressure is applied, it is necessary to reduce the influence and protect the semiconductor sensor, so a three-diaphragm structure consisting of a center diaphragm and a seal diaphragm is used, and the volumetric rigidity of these is selected optimally. This solves the above point. With this structure, each diaphragm correctly transmits pressure to the semiconductor sensor without contacting the main body in the normal measurement range, but when an excessive differential pressure is applied, the seal diaphragm stops in close contact with the main body waveform, suppressing the increase in internal pressure. Can be done. At this time, the center diaphragm does not come into contact with the main body, deformation is within the elastic range, and pressure differential above a certain level is not generated. In addition, the rigidity of the main body is sufficiently larger than that of the seal diaphragm, so even if the seal diaphragm remains deformed when excessive differential pressure is released, it will not affect the semiconductor sensor. [Problem to be solved by the invention] In the conventional differential pressure transmitter described above, in order to measure a high differential pressure, it was necessary to increase the rigidity of the center diaphragm and the pressure resistance of the sensor section. However, increasing the rigidity of the center diaphragm increases the thickness of the diaphragm, making it difficult to weld it with the necessary strength. Furthermore, since it is not possible to reduce the amount of liquid sealed inside to the required amount, it has been impossible to create a sensor part with high pressure resistance. An object of the present invention is to provide a high differential pressure transmitter that can measure high differential pressures. [Means for Solving the Problems] In order to achieve the above object, in a pressure receiving part structure in which a high differential pressure is received by two seal diaphragms and this differential pressure is directly transmitted to a sensor, when an excessive differential pressure is applied, the sensor The structure has a structure that does not apply force to the surrounding welds, making it possible to measure high differential pressures by improving pressure resistance. [Function] The pressure that the seal diaphragm receives when an excessive differential pressure is applied is:
It is transmitted directly to the semiconductor sensor and the housing that houses the semiconductor sensor via the sealed liquid.

Semiconductor sensors have a withstand pressure that is 10 times higher than the measured differential pressure, so they themselves have sufficient withstand pressure of 150 kgf/cd, which is required when the measured differential pressure is several tens of kgf/al. There is.

On the other hand, the housing that houses the semiconductor sensor has its upper surface in contact with the pressure receiver body and its lower surface in contact with the member fixed to the pressure receiver body, so the force generated when an excessive differential pressure is applied is applied to the welds around the sensor. The pressure receiving part is supported by the main body of the pressure receiving part and other members, so the pressure resistance of the pressure receiving part is improved. [Example] Hereinafter, an example of the present invention will be described with reference to FIG.

FIG. 1 shows an internal structural diagram of a high differential pressure transmitter.

The pressure receiving part structure has a two-diaphragm structure consisting of a high pressure side seal diaphragm 4a and a low pressure side seal diaphragm 4b to measure high differential pressure.The pressure introduced to the high pressure side and low pressure side passes through the seal diaphragm through the sealed liquid 5. is transmitted to both sides of the semiconductor sensor 1, and the pressure difference (differential pressure) is converted into an electrical signal. The pressure receiving part must operate stably even with corrosive fluids and fluid temperatures between -40°C and 120°C, so the semiconductor sensor l is sealed in a liquid such as silicone oil, which has a proven track record of stability. The fully welded structure completely isolates it from the outside atmosphere. In addition, since no other organic solvents are used inside, there is no deterioration of parts even under harsh environments such as high temperatures, resulting in a highly reliable structure with excellent long-term stability.

Here, in the semiconductor sensor l, a strain-generating body that receives a differential pressure is made of silicon single crystal, and a gauge resistor is diffused into this, and the resistance value is affected by the piezoresistance effect against the stress generated by the differential pressure. The output is obtained by changing the output. Further, this output is connected to a hermetic seal terminal 9 provided in a housing 8 that houses the semiconductor sensor by a bonding wire l1 and a wiring board 12, and is taken out to the outside via a relay board 13. This semiconductor sensor 1 consists of a hollow cylindrical base 2 and a hollow metal base 3.
By fitting this into the housing 8 that houses the semiconductor sensor, it is supported at the g section, and by welding at the f section, it has a structure that equivalently floats in the liquid.
As with the three-diaphragm structure, this structure is not easily affected by deformation of the pressure-receiving part body.

Furthermore, the upper surface part of the housing 8 that accommodates the semiconductor sensor is fitted into the high-pressure side pressure-receiving part main body 6, supported by contacting at part a, and welded at part b.

The lower surface of the housing 8 that houses the semiconductor sensor is a member 1.
It is supported at part C through 0 and welded at parts d and e.
When differential pressure is applied, the axial force generated in the housing 8 housing the semiconductor sensor and the member 10 is received by the support parts a and C, and no stress is generated in the weld parts b and d. It has become. Furthermore, since the welding depth of the welded part e is made deep, it has sufficient strength against excessive differential pressure. A low pressure side pressure receiving section main body 7 is joined to the high pressure side pressure receiving section main body 6 to form a pressure receiving section in order to reduce the amount of sealed liquid to the required amount. In the above embodiment, in order to reduce the amount of sealed liquid to the required amount, the pressure receiving part main body was divided into two parts, the high pressure side pressure receiving part main body and the low pressure side pressure receiving part main body. It is also possible to configure the unit 6 by itself. In this case, the structure is simplified and the number of parts is reduced. Furthermore, cost reduction and reliability improvement are achieved.

According to the present invention, the stress applied to the welded part around the sensor can be reduced by providing the support parts a and C, and the structure allows the differential pressure to be directly transmitted from the seal diaphragm to the semiconductor sensor via the sealed liquid. It is possible to realize a pressure receiver for a differential pressure transmitter that measures high differential pressures. Furthermore, by configuring the pressure receiving section main body as a single unit, the structure is simplified and the number of parts is reduced. Furthermore, cost reduction and reliability improvement are achieved.

〔Effect of the invention〕

According to the present invention, the stress applied to the welded portion around the sensor can be reduced by providing the support portions a and C, and the structure allows differential pressure to be directly transmitted from the seal diaphragm to the semiconductor sensor via the sealed liquid. A pressure receiver for differential pressure transmission can be configured to measure high differential pressures. In addition, by configuring the pressure receiver body as a single unit, the structure is simplified and the number of parts is reduced. Furthermore, cost reduction and reliability improvement are achieved.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view showing the structure of the pressure receiving part of a high differential pressure transmitter according to an embodiment of the present invention, and FIG. 2 is a longitudinal cross-sectional view showing the structure of the pressure receiving part of a high differential pressure transmitter according to another embodiment of the present invention. 3 is a vertical sectional view showing a conventional example of a differential pressure transmitter. 1...Semiconductor sensor. 4a...High pressure side seal diaphragm, 4b...Low pressure side seal diaphragm, 5...
・Filled liquid, 8... Hermetic seal fitting, 15...
・Sen Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. A differential pressure transmitter using a semiconductor sensor has a high pressure side seal diaphragm and a low pressure side seal diaphragm,
The pressure difference is directly transmitted to the semiconductor sensor via the sealed liquid, and the upper surface of the housing housing the semiconductor sensor is in contact with the pressure receiver body, and the lower surface is in contact with a member fixed to the pressure receiver body. A pressure receiving part for a differential pressure transmitter characterized by having a structure.