JPH0450743A - Differential pressure transmitter - Google Patents

Abstract

PURPOSE:To make a zero-point adjustment with a small error by providing a mechanism which closes a by-pasby a valve mechanism at the time of differential pressure detection to lead the pressure of a diaphragm to a detecting element, and closes one pressure medium passage and open the by-pass at the time of the zero-point adjustment to apply equal pressure to both surfaces of the detecting element. CONSTITUTION:The valve mechanism 12 is provided to the connection part between a U-shaped pressure medium passage 9 and by-pass 11 and when differential pressure is detected, the high-pressure side downstream part 9aa and high-pressure side downstream part 9ab of the passage 9 are linked with each other to lead pressure Pa and Pb which are applied to respective diaphragms 7 to the surfaces of the element 10 with the by-pass 11 closed. When the zero-point adjustment is performed, the valve mechanism 12 is switched to close the high-pressure side upstream side part 9aa and links the low-pressure side downstream part 9bb with the high-pressure side downstream part 9ab, thereby applying the pressure Pb to the respective surfaces of the element 10. Consequently, the zero-point adjustment can be performed with a small error through remote operation without operating a three-branch valve mechanism installed outside the differential pressure transmitter.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a differential pressure transmitter used in various plants and the like.

(Prior Art) As one of the differential pressure transmitters used in various plants, the one shown in FIG. 4 is conventionally known.

The differential pressure transmitter shown in this figure includes a block part 101 formed in a thick plate shape, and pressure receiving flange parts 102 provided on both sides of this block part 101, and a pressure receiving flange part 102 connected to each pressure receiving flange part 102. Each process plumber 03a, 1
03b is detected and transmitted to the outside.

The block part 101 is a block body 1 formed in a thick plate shape.
05, a partition diaphragm 107 provided to cover each recess 106 formed on both sides of this block body 105, and a pressure medium passage 108 formed in the block body 105 so as to communicate each recess 106.
A differential pressure detecting element 109 provided approximately in the center of the block body 105 is inserted into a signal line hole 110 formed in the block body 105 so as to pass through the pressure medium passage 108 and the upper part of the block body 105. Differential pressure detection element 10
9 to the outside, a hermetic seal 112 that guides the signal line 111 to the outside while closing the signal line hole 110 of the block body 105, and the pressure sealed by each partition diaphragm 107. A pressure medium 113 such as silicone oil or ethylene glycol is provided to be filled in the medium passage 108 and the signal line hole 110.

Further, each pressure receiving flange portion 102 includes a thick plate-shaped flange body 115 provided so as to cover each surface of the block body 105, and a peripheral groove 116 formed on the partition wall diaphragm 107 side of this flange body 115. The packing 117 to be fitted and each of these flange bodies 115
and a bolt nand mechanism 118 that brings the process piping 10 into close contact with the screen of the block body 105.
3a, 103b is applied to the flange body 1 through a passage hole 119 formed in the upper part of the flange body 115.
A recess 120 formed on the partition wall diaphragm side of No. 15
lead to.

If each partition diaphragm 107 is distorted by the pressure from each process pipe 103a, 103b, a difference will occur in the pressure applied to each side of the differential pressure detecting element 109, and this will be caused by the differential pressure detecting element 109. It is detected, and the test result is outputted to the outside via the signal line 111.

In addition to such differential pressure transmitters, various structures are known, but they are based on different measurement principles.

(Problem to be Solved by the Invention) However, in such a differential pressure transmitter, slight permanent distortion occurs due to aging, excessive pressure, etc., and this may cause zero point drift.

Therefore, when installing such a differential pressure transmitter, a bypass pipe 1 is sometimes installed in each process pipe 103a, 103b in advance.
21, and each of these process piping 103
a, 103b and the stop valve 12 in the bypass pipe 121.
2a, 122b, and 122c are respectively attached to form a three-way valve mechanism, and when adjusting the zero point, the stop valve 122c provided in the bypass pipe 121 is opened, and the stop valve 1 provided in each process pipe 103a, 103b is opened.
22a and 122b are closed to make the pressure applied to the differential pressure detection element 109 the same, and after measuring the offset amount of the signal output from the differential pressure detection element 109, the stop valve 122c provided in the bypass pipe 121 is closed. is closed, and stop valves 122a and 122b provided in each process pipe 103a and 103b are opened to measure the differential pressure.

However, with this method, it is not possible to operate the three-way valve mechanism from a remote location, so when adjusting the zero point, it is necessary to go to the location where the differential pressure transmitter is installed and operate the three-way valve mechanism. , it was inconvenient.

In view of the above circumstances, the present invention provides a differential pressure transmitter that can perform zero point adjustment with less error at a remote location without operating a three-way valve mechanism installed outside the differential pressure transmitter. The purpose is to

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, a differential pressure transmitter according to the present invention includes a differential pressure detection element provided at a position that blocks a pressure medium passage formed in a block body, and a pressure A partition diaphragm that closes both ends of the medium passage, a bypass passage that bypasses each side of the differential pressure detection element of the pressure medium passage, and a bypass passage that bypasses each side of the differential pressure detection element of the pressure medium passage, and a bypass passage that is provided at a connecting portion between the bypass passage and the pressure medium passage, and is provided to open the bypass passage. and a valve mechanism that switches between blocking the pressure medium passage, blocking the bypass passage, and opening the pressure medium passage.

(Function) In the above configuration, when differential pressure is detected, the bypass passage is closed by the valve mechanism, and the pressure medium passage is opened to guide the pressure applied to each partition diaphragm to each surface of the differential pressure detection element. The valve mechanism is switched to close one of the pressure medium passages, and the bypass passage is opened to equalize the pressure applied to both sides of the differential pressure detection element.

(Embodiment) FIG. 1 is a sectional view showing an embodiment of a differential pressure transmitter according to the present invention.

The differential pressure transmitter shown in this figure includes a block portion 1 formed in the shape of a thick plate, pressure receiving flange portions 2 provided on both sides of the block portion 1, and drive and control of the block portion 1 and the pressure receiving flange portions 2 provided on both sides of the block portion 1. It is equipped with a signal processing circuit 3 that performs signal processing, detects the pressure difference between each process pipe 4a, 4b connected to each pressure receiving flange portion 2, and transmits this to the outside via the signal processing circuit 3. Further, when a zero point adjustment signal is supplied from the outside, the signal processing circuit 3 drives the block section 1 to perform the zero point adjustment.

The block part 1 includes a block body 5 formed in a thick plate shape,
A U-shaped partition wall diaphragm 7 provided to cover each recess 6 formed on both sides of the block body 5, and a diaphragm 8 formed within the block body 5 so as to communicate the recesses 6. A semiconductor type differential pressure detection element 10 provided in the center of the pressure medium passage 9 and a bypass path that communicates required parts of the U-shaped pressure medium passage 9 so as to communicate each surface of the differential pressure detection element 10. 11 and a valve mechanism 12 provided at a connecting portion with the U-shaped pressure medium passage 9.

Further, the block portion 1 is configured to include the U-shaped pressure medium passage 9.
and a signal line 14 that is inserted into a signal line hole 13 formed in the block body 5 so as to pass through the upper part of the block body 5 and leads the output of the differential pressure detection element 10 to the external signal processing circuit 3. , the signal line 15 inserted through the signal line hole 13 and guiding the drive voltage of the signal processing circuit 3 to the valve mechanism 12, and each signal 1! while closing the signal line hole 13 of the block body 5! Silicone oil and ethylene are filled in the hermetic seal 16 that guides 14.15 to the outside, the U-shaped pressure medium passage 9 sealed by each partition diaphragm 7, the bypass passage 11, and the signal line hole 13. A pressure transmission medium 17 such as glycol is provided.

The valve mechanism 12 is connected to the bypass passage 1 as shown in FIG. 2(a).
1 and a U-shaped pressure medium passage 9, the valve 19 is housed in a chamber 18, and the valve 19 is slidably inserted into a hole 2° provided in the chamber 18, and the valve 19 is indicated by the arrow. The drive shaft 21 is slidably supported in the directions A and B, and the drive shaft 21 is accommodated in the hole 20 and biased in the direction of the arrow A. The high-pressure side upstream portion 9aa of the U-shaped pressure medium passage 9 is closed, and the bypass passage 11 and the high-pressure side downstream portion 9a of the U-shaped pressure medium passage 9 are closed.
and a spring 22 that communicates with b.

Furthermore, the valve mechanism 12 is embedded around the hole 20 and is formed in the valve 19 by urging the drive shaft 21 in the direction of arrow βμB when a drive voltage is supplied through the signal line 15. Bypass path 1 by the other needle portion 19b
1 is closed, and the high pressure side upstream portion 9aa of the U-shaped pressure medium passage 9 is opened to open the U-shaped pressure medium passage 9.
A drive coil 23 is provided that communicates the high pressure side of the flow section 9aa and the high pressure side downstream portion 9ab.

Further, each pressure receiving flange portion 2 has a thick plate-shaped flange body 26 provided so as to cover each surface of the block body 5.
A packing 28 is fitted into a circumferential groove 27 formed on the partition wall diaphragm 7 side of the flange body 26, and a bolt and nut mechanism 29 that brings each of the flange bodies 26 into close contact with both sides of the block body 5. The pressure in the process pipes 4a and 4b is guided to a recess 31 formed on the partition wall diaphragm 7 side of the flange main body 26 through a passage hole 30 formed in the upper part of the flange main body 26.

Further, the signal processing circuit 3 includes the signal line 1 as shown in FIG.
an amplifier 35 for amplifying the differential pressure detection signal from the differential pressure detection element 10 supplied via the A/D converter 3;
4, which performs A/D conversion of the differential pressure detection signal supplied from the amplifier 35, and then performs various preset correction processing and arithmetic processing, and a working area of this microprocessor 36. A memory 37 is also provided.

Further, the signal processing circuit 3 includes a D/A converter 38 for D/A converting the processing result of the microprocessor 36;
A modulator 39 modulates the current supplied from the outside via the two-wire transmission line 41 based on the high power of the D/A converter 38, and transmits a differential pressure detection signal to the outside. a switch 43 operated by the zero point adjustment signal;
When this switch 43 is in the zero point adjustment position, the generation of drive voltage is stopped and the drive coil 23 of the valve mechanism 12 is
The valve drive circuit 40 is provided with a valve drive circuit 40 that stops energizing the valve.

Next, the differential pressure detection operation and zero point adjustment operation of this embodiment will be sequentially explained.

First, in the differential pressure detection operation, the pressure Pa applied to the high pressure side is transmitted to the pressure transmission medium 17 via the partition diaphragm 7, and then the U-shaped pressure medium passage 9 filled with this pressure transmission medium 17 is transmitted to the valve mechanism 12 via the high-pressure side upstream portion 9aa.

Here, at the time of differential pressure transverse ratio, the drive shaft 21 is urged in the direction of arrow B by the drive coil 23 as shown in FIG. 2(b).
The needle portion 19b of the valve 19 closes the bypass passage 11 and closes the high pressure side upstream portion 9a of the U air pressure medium passage 9.
a is open, the pressure from the high-pressure side upstream portion 9aa of the U-shaped pressure medium passage 9 is not transmitted to the low-pressure side upstream portion 9ba and the low-pressure side downstream portion 9bb of the U-shaped pressure medium passage 9; High pressure side downstream portion 9ab of the shape pressure medium passage 9
It is transmitted only to one side of the differential pressure detection element 1o via the.

On the other hand, the pressure pb applied to the low pressure side is
After being transmitted to the pressure transmission medium 17 via the pressure transmission medium 17, the pressure transmission medium 17 is transmitted to the differential pressure detection element 10 via the low pressure side upstream portion 9ba and the low pressure side downstream portion 9bb of the U-shaped pressure medium passage 9 filled with the pressure transmission medium 17. is transmitted to the other side.

At this time, since the bypass passage 11 is closed by the valve mechanism 12, the pressure on the low pressure side of the U-shaped pressure medium passage 9 is not transmitted to the high pressure side of the U-shaped pressure medium passage 9.

Therefore, in this state, the differential pressure detection element 10 generates a differential pressure detection signal having a value corresponding to the pressure difference between the pressures Pa and Pb applied to both sides thereof, and sends this signal to the signal processing circuit via the signal line 14. Supply to 3.

Then, when the microprocessor 36 of the signal processing circuit 3 is supplied with the differential pressure detection signal via the amplifier 35, it A/D converts and takes in the signal, and after performing correction processing, arithmetic processing, etc. The signal is supplied to an A converter 38 for D/A conversion and supplied to a modulator 39.

Thereby, the modulator 39 modulates the current supplied from the outside and transmits the differential pressure detection signal supplied from the D/A converter 38 to the outside.

Further, during the zero point adjustment operation, the switch 43 is first set to the zero point adjustment position by an instruction from the outside, and in response, the valve drive circuit 40 stops energizing the drive coil 23.

As a result, the drive shaft 21 is urged in the direction of arrow A by the spring 22 as shown in FIG.
aa is closed, and the bypass passage 11 and the high-pressure side downstream portion 9ab of the U-shaped pressure medium passage 9 are made to communicate with each other.

As a result, the high pressure side upstream portion 9a of the U-shaped pressure medium passage 9
The pressure from a is not transmitted to the high pressure side downstream portion 9ab of the U-shaped pressure medium passage 9, and the pressure in the low pressure side downstream portion 9bb of the U-shaped pressure medium passage 9 is transferred to the high pressure side of the U-shaped pressure medium passage 9. The pressure pb is transmitted to the downstream portion 9ab, and pressure pb is applied to both sides of the differential pressure detection element 10. Also at this time, the U-shaped pressure medium passage 9
The U-shaped pressure medium passage 9 is connected from the high pressure side upstream portion Qaa side and the low pressure side upstream portion 9ba side of the U-shaped pressure medium passage 9 by the throttle 8 provided in the high pressure side upstream portion 9aa and the low pressure side upstream portion 9ha of the U-shaped pressure medium passage 9. Movement of the pressure transmission medium 17 flowing into the high-pressure side downstream portion Qab side and the low-pressure side downstream portion 9bb side is suppressed.

Therefore, in this state, the differential pressure detection element 10 outputs a differential pressure detection signal when the differential pressure is zero, and this is supplied to the signal processing circuit 3 via the signal line 14 and amplified, and then A/D converted. After being subjected to correction processing, arithmetic processing, etc. by digital processing, it is D/A converted and outputted to the outside via a modulator 39.

As described above, in this embodiment, the valve mechanism 12 is provided at the connection portion between the U-shaped pressure medium passage 9 and the bypass passage 11,
When differential pressure is detected, the valve mechanism 12 connects the high-pressure side upstream portion 9aa of the U-shaped pressure medium passage 9 and the high-pressure side downstream portion 9ab of the U-shaped pressure medium passage 9, closes the bypass passage 11, and closes each partition wall. The pressures Pa and Pb applied to the diaphragm 7 are guided to each surface of the differential pressure detection element 10, and when adjusting the zero point, the valve mechanism 12 is switched to close the high-pressure side upstream portion 9aa of the U-shaped pressure medium passage 9, and the bypass The passage 11 is opened to connect the low-pressure side downstream portion 9bb of the U-shaped pressure medium passage 9 and the high-pressure side downstream portion a of the U-shaped pressure medium passage 9.
Since the pressure pb is applied to each surface of the differential pressure detection element 10 by communicating with Zero point adjustment with little error can be performed at a remote location simply by controlling the system.

Furthermore, in this embodiment, the high-pressure side upstream portion 9aa of the U-shaped pressure medium passage 9 can be shut off and the bypass passage 11 can be opened by one operation of one valve mechanism 12. The structure can be made simpler than when using , and it can be driven with lower power consumption.

Furthermore, in this embodiment, even when the valve mechanism 12 is operated, the pressure transmission medium 17 in the U-shaped pressure medium passage 9 and the bypass passage 11 hardly moves, so it is possible to minimize the occurrence of errors. can.

Furthermore, in this embodiment, since the throttles 8 are provided in the high-pressure side upstream portion 9aa and the low-pressure side upstream portion 9ba of the U-shaped pressure medium passage 9, the movement of the pressure transmission medium 17 is reduced when zero point adjustment is performed. The time required for the differential pressure to reach zero can be shortened by reducing the

Furthermore, since the valve mechanism 12 is provided inside the block body 5, there is a risk of malfunction due to corrosion if the process piping 4a, 4b is clogged with foreign matter contained in the fluid, unlike when the valve mechanism is provided externally. can be completely eliminated.

Further, in the above embodiment, a semiconductor pressure sensitive element is used as the differential pressure detecting element 10, but a capacitance type differential pressure detecting element may be used.

In addition, in the embodiment described above, each process pipe 4a
, 4b, the pressure difference between the fluid and the atmosphere may be detected by opening the low pressure side to the atmosphere.

Further, in the embodiment described above, the needle type valve 19
Valve with similar function,
For example, an O-ring seal type valve may be used.

Further, in the embodiment described above, the valve mechanism 1 is provided at the connection portion between the high pressure side of the U-shaped pressure medium passage 9 and the bypass passage 11.
However, the valve mechanism 12 may be provided at the connection portion between the low pressure side of the U-shaped pressure medium passage 9 and the bypass passage 1i.

Further, in the embodiment described above, the valve 19 is driven by the drive coil 23, but the valve 19 is driven by another drive mechanism, for example, a drive mechanism using a piezoelectric element or the like.
It is also possible to drive the

〔Effect of the invention〕

As explained above, according to the present invention, zero point adjustment with less error can be performed at a remote location without operating the Toki valve mechanism installed outside the differential pressure transmitter.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of the differential pressure transmitter according to the present invention, FIG. 2 is a detailed cross-sectional view of the valve mechanism shown in FIG. 1, and FIG.
This figure is a detailed block diagram of the signal processing circuit shown in FIG. 1, and FIG. 4 is a sectional view showing an example of a conventionally known differential pressure transmitter. 1... Block part 2... Pressure receiving flange part 5... Block body 7... Partition diaphragm 8... Restriction 9... Pressure medium passage 10... Differential pressure detection element 1-... Bypass path 12... Valve mechanism

Claims (2)

[Claims] (1) A differential pressure detection element provided at a position that blocks a pressure medium passage formed in the block body, a partition diaphragm that closes both ends of the pressure medium passage, and each surface of the differential pressure detection element of the pressure medium passage. a bypass passage that bypasses the side; and a valve mechanism that is provided at a connecting portion between the bypass passage and the pressure medium passage and switches between opening the bypass passage and blocking the pressure medium passage, and closing the bypass passage and opening the pressure medium passage. A differential pressure transmitter comprising: (2) The differential pressure transmitter according to claim 1, wherein a restriction is formed in a predetermined portion of the pressure medium passage closer to the partition diaphragm than the connection portion between the pressure medium passage and the bypass passage.