JP2515707Y2 - Differential type differential pressure transmitter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a differential type differential pressure transmitter for detecting a minute pressure.

(B) Conventional Technology FIG. 3 is a schematic explanatory view showing a conventional differential pressure differential transmitter for detecting a minute pressure.

This differential pressure transmitter is provided with a pressure detecting portion 52 at the center of the inside of a rigid body 51, and pressure receiving portions 53 and 53a on both opening surfaces of the body 51. The pressure receiving portions 53 and 53a are used as pressure detecting portions.
It communicates with 52 detection chambers 54. The pressure receiving portion 53, 53a, the seal diaphragm 55 is stretched on the opening surface of the body 51,
A filling liquid (silicone oil) 57 is filled in the inner space 56 of the chamber. The pressure transmitting portion (transmission pipe) 58 that communicates the pressure receiving portions 53 and 53a with the detection chamber 54 is provided with an orifice 60 via a branch pipe 59, and the pressure receiving portions 53 and 53a have opposite directions. Communication parts (communication pipes) 62, 62a having directional relief valves 61, 61a are provided. Further, a movable electrode 63 is provided at the center of the detection chamber 54, and fixed electrodes 64 and 64a are provided on opposite sides of the movable electrode 63 so as to face each other. The one pressure receiving portion 53a is directly arranged in a pipe for measuring a flow rate or pressure, or a process system (not shown) such as a tank for measuring a liquid level or pressure.

When detecting the differential pressure, the pressure is introduced into the pressure receiving portion 53 directly arranged in the process system. The pressure acting on the pressure receiving portion 53 is transmitted to the enclosed liquid (silicone oil) 57 by the seal diaphragm 55, is transmitted to the detection chamber 54, and acts on the movable electrode (metal plate) 63. The movable electrode 63 is displaced by the high pressure and the low pressure. As a result, the electrostatic capacitance between the movable electrode 63 and the fixed electrodes (fixed electrode plate provided on the wall surface of the detection chamber) 64, 64a changes, and this capacitance change is derived via a lead wire (not shown). . That is, the pressure difference is detected (not shown) via the electric signal transmission unit and the signal amplification / conversion unit connected to the lead wire, and the differential pressure is detected and transmitted. The relief valve
61 and 61a serve as a safety protection when a pressure exceeding the limit acts on the pressure receiving portion 53, and the orifice 60 acts so that only a sudden constant pressure acting on the pressure receiving portion 53 acts on the detecting portion 54, that is, differential. It works so that it can detect only various pressures. Therefore, as shown in the pressure signal characteristic diagram of FIG. 4, the input pressure signal is obtained only when a sudden pressure change (ΔP) is applied to the pressure receiving portion 53, and the input pressure signal is gradually obtained under a moderate time. The detection chamber 54 does not change with respect to the applied pressure, and the output voltage (ΔV) can be obtained only when a sudden pressure change is applied.
After that, the output voltage is gradually decreased by the orifice 60. That is, it has a differential type differential pressure transmission structure.

(C) Problems to be Solved by the Invention The above-mentioned conventional differential type differential pressure transmitter has a structure in which the filled liquid (working fluid) is filled between the pressure receiving part and the pressure detecting part, and the working fluid capacity of the pressure receiving part Is a method of detecting the differential pressure by the change of. Therefore, if the measurement range width is wide, it is necessary to increase the volume of the pressure receiving portion. However, when the volume of the pressure receiving portion is set to be large, the effective pressure receiving area of the pressure receiving portion changes and the linearity deteriorates. That is, the linear characteristic (linearity) is deteriorated. For this reason, conventionally, there is a disadvantage that a change in a minute pressure can be detected only in a low pressure range (for example, 0 to 5 Kg / m ² ).

An object of the present invention is to solve the above problems and to provide a differential pressure differential transmitter capable of accurately detecting a minute pressure change over a wide range from a low pressure side to a high pressure side.

(D) Means and Actions for Solving the Problem In order to achieve this object, the differential type differential pressure transmitter of the present invention has the following configuration.

The differential type differential pressure transmitter is equipped with a pressure detector in the center of the body, and pressure receivers filled with filled liquid on both openings of the body. In a differential type differential pressure transmitter that communicates with the detection chamber of the other section and communicates both of the transmission tubes through a branch pipe having an orifice, the one pressure receiving section contacts the diaphragm of this pressure receiving section. And a balancing bellows filled with a static pressure imparting member that applies a pressure opposite to the measured pressure, and a replaceable balancing spring that biases the balancing bellows against the diaphragm of the pressure receiving portion. The pressure balancing means is provided.

In the differential type differential pressure transmitter having such a configuration, for example, a pressure balancing means (pressure balancing housing) is attached to one pressure receiving portion (pressure receiving portion facing the pressure receiving portion for receiving pressure introduced from the process system) side. are doing. This pressure balance housing is composed of a balance bellows filled with, for example, a filling liquid on the outside of the seal diaphragm of the pressure receiving portion, and a balance spring for exerting a pressure on the balance bellows. The maximum measurement range is set by setting the pressure of the balance spring. For example, as shown in the explanatory diagram of the pressure-voltage characteristic of FIG. 2, when detecting a minute pressure in the pressure range of pressure 0 to P ₁ , the load is set to 0, that is, the balance spring (balance bellows). Thus, the pressure applied to the pressure receiving portion in advance is set to 0. As a result, the introduction pressure acting on the pressure receiving part on the process side is 0 to P ₁
In the range of, the balance spring bends. At this time, the displacement of the equilibrium bellows causes a maximum volume change of V ₁ , and that point becomes the maximum measurement range. That is, the maximum measurement range of the measurement pressure is set.

If a slight pressure change is detected in the pressure range of P _{2 to} P ₃ shown in FIG. ₂ , the balance spring is replaced, that is, the spring for measuring P ₁ is replaced with, for example, a long spring ( the P ₂ to P ₃ for the spring) is attached to equilibrate housing. Then, this spring is compressed and set to a load corresponding to the introduction pressure P ₂ , and a static pressure is applied to the pressure receiving portion by the balance bellows. As a result, the volume change V ₃ in the (P ₃ −P ₂ ) range can be covered. In other words, by using a balanced housing (bellows, spring) to apply a pressure (static pressure) that opposes the measured pressure to the pressure receiving portion in advance, a constant volume of working fluid similar to the conventional one is used (volume of pressure receiving portion). Can be accurately detected in a wide pressure range.

(E) Embodiment FIG. 1 is a schematic explanatory view showing a specific embodiment of the differential type differential pressure transmitter according to the present invention.

As is well known, the differential type differential pressure transmitter is provided with a pressure detecting portion 11 at the inner center of the rigid body body 1 and pressure receiving portions 2 and 2a on both opening surfaces of the body body 1.
2a is connected to the detection chamber 12 of the pressure detection unit 11 via the pressure transmission unit (transmission pipe) 14. In the pressure receiving portions 2 and 2a, a seal diaphragm 21 is stretched on the opening surface of the body body 1, and a filling liquid (silicone oil) 22 is filled in the space 13 inside.
The pressure transmitting portion (transmission pipe) 14 is provided with an orifice 16 that enables differential type differential pressure transmission via a branch pipe 15, and both pressure receiving portions 2 and 2a have unidirectional reliefs in opposite directions. The communication parts (communication pipes) 18 and 18a provided with the valves 17 and 17a are provided, and the safety of the pressure receiving parts 2 and 2a is intended. Also,
A movable electrode 19 is provided in the center of the detection chamber 12, and fixed electrodes 20 and 20a are provided on opposite sides of the movable electrode 19 so as to face each other. The one pressure receiving portion 2 is directly arranged in a pipe for measuring a flow rate or pressure, or a process system (pressure introducing pipe) 4 such as a tank for measuring a liquid level or pressure.

When detecting the differential pressure, the pressure P (for example, P ₁ , P ₂ , P ₃ ) is introduced into the pressure receiving portion 2 directly arranged in the process system 4. The pressure P acting on the pressure receiving portion 2 is transmitted to the enclosed liquid (silicone oil) 22 by the seal diaphragm 21, is transmitted to the detection chamber 12, and acts on the movable electrode (metal plate) 19. The movable electrode 19 is displaced by the high pressure and the low pressure.
As a result, the electrostatic capacitance between the movable electrode 19 and the fixed electrode (fixed electrode plate provided on the wall surface of the detection chamber 12) 20, 20a changes,
This capacitance change is derived via a lead wire (not shown). That is, the pressure difference is detected (not shown) via the electric signal transmission unit and the signal amplification / conversion unit connected to the lead wire, and the differential pressure is detected and transmitted.

The feature of this invention is that the pressure balance means 3 is provided on one pressure receiving portion 2a.
Is provided and the static pressure applied to the pressure receiving portion 2a is selected, so that the maximum measurement range of the measurement pressure P can be arbitrarily set.

The pressure balance means (pressure balance housing) 3 includes a balance bellows 31 for applying a pressure opposite to the measured pressure P to the pressure receiving portion (seal diaphragm 21) 2a, and an exchange for energizing the balance bellows 31. Possible balancing springs
It consists of 32 and.

The pressure balance housing 3 is the body 1 on the pressure receiving portion 2a side.
Is a flat cylindrical body with both ends opened. A flange-shaped arm portion 33 is projectingly provided at the tip of the housing 3. Balance bellows 31 is housing 3
A member for static pressure application (for example, silicone oil or a pneumatic material 34) is provided inside and fixed to the inner peripheral edge of the housing 3 in the space between the pressure receiving portion 2a and the seal diaphragm 21.
Is sealed and filled. The balance spring 32 is disposed between the arm portion 33 and the balance bellows 31 and is replaceably attached to the housing 3. The balance spring 32 is for applying a pressure opposite to the measurement pressure P to the pressure receiving portion 2a via the balance bellows 31 and setting the maximum measurement range. As shown in the explanatory diagram of the pressure (load) output voltage characteristic of FIG. 2, the balance spring 32 has, for example, three types of spring forces capable of giving a pressure corresponding to the pressures P ₁ , P ₂ and P _3. The springs 32 (A, B, C) are prepared. In the embodiment, three types of springs 32 having the same spring force (formed of the same material) and different spring lengths are used, and the three types of springs 32 are used according to the measured pressure P (P ₁ , P ₂ , P ₃ ). , Selectable to use. For example, when the measured pressure is P ₁ , the shortest spring 32 is used, and when the measured pressure is P ₃ , the longest spring 32 is used.

In order to detect a minute pressure in the range of static pressure 0 to P ₁ by the differential type differential pressure transmitter having such a structure, a spring 32 having a short length is attached to the housing 3 in advance.
At a pressure of 0, the spring 32 prevents the load from acting on the pressure receiving portion 2a via the balance bellows 31. As a result, the maximum range P _{1 of} measured pressure is set. For example, second
As shown in the diagram for explaining the pressure output voltage characteristic in the figure, the balance spring 32 bends in accordance with the slight pressure difference in the pressure range of static pressure 0 to P ₁ . At this time, the displacement of the equilibrium bellows 31 causes a maximum volume change of V ₁ , and that point becomes the maximum measurement range.

On the other hand, in the case of detecting a slight pressure change in the range of static pressure P _{2 to} P ₃ shown in FIG. ₂ , replace the balance spring 32,
For example, a long spring 32 may be attached to the pressure balancing housing 3
Attach to. Then, the spring 32 is compressed, that is, the load is set to correspond to the introduction pressure P ₂ , and the balance bellows 31 applies the load to the pressure receiving portion 2a. This allows
It is possible to cover the volume change V _{3 in the} range of (P ₃ −P ₂ ). In other words, pressure balancing means (bellows 31, spring 3
2) By applying a pressure facing the lower limit P ₂ of the measured pressures P _{2 to} P ₃ to the pressure receiving portion 2a in advance by ₃ , the pressure receiving portion 2,
It is possible to accurately detect a minute pressure change in a wide pressure range without increasing the volume of 2a. Therefore, when detecting the differential pressure, the maximum measurement range of the measured pressure is set,
There is no need to expand the measurement range width, the input pressure and output voltage characteristics can be increased, and the measurement sensitivity can be improved.

In order to keep the sensitivity characteristic constant, a spring having a spring characteristic (spring constant) like a straight line "A" is selected as shown in the explanatory diagram of the pressure (load) output voltage characteristic in FIG. There is a need. Straight line "B" or straight line "C"
When a spring having the characteristic of 1 is selected, the pressure signal characteristic will also change.

(F) Effect of the device In this device, as described above, the pressure balancing means for applying a pressure opposite to the lower limit of the measurement pressure range is provided to one pressure receiving part, and the upper limit of the measurement range is arbitrarily selected. Since the setting is made, it is possible to accurately detect a minute pressure change over a wide range in the pressure receiving portion having a constant volume. Further, in this invention, the balance spring for applying a pressure opposite to the measured pressure to the pressure receiving portion can be exchanged, and an arbitrary maximum measurement range can be set by selecting the balance spring, so that it is not necessary to widen the measurement range width. The input pressure and output voltage characteristics can be made large, and the measurement sensitivity can be improved. Furthermore, since the differential pressure is detected by changing the applied force of the pressure balancing means for each measurement range (changing the characteristics of the balancing spring), the overall configuration can be miniaturized. Further, since it is not necessary to increase the volume of the pressure receiving portion, the effective pressure receiving area of the pressure receiving portion does not change, and the linear characteristic (linearity) does not deteriorate.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing the differential pressure transmitter of the embodiment, FIG. 2 is an explanatory view showing pressure (load) output voltage characteristics of the differential pressure transmitter of the embodiment, and FIG. 3 is a conventional differential pressure transmitter. FIG. 4 is a schematic explanatory diagram showing the transmitter, and FIG. 4 is an explanatory diagram showing pressure signal characteristics of the differential type differential pressure transmitter. 1: Body body, 2 ・ 2a: Pressure receiving part, 3: Pressure balancing means, 11: Pressure detecting part, 12: Detection chamber, 14: Transfer pipe, 15: Branch pipe, 16: Orifice, 21: Diaphragm, 31: Balance Bellows, 32: Balance spring, 34: Static pressure applying member

Claims (1)

(57) [Scope of utility model registration request] 1. A pressure detecting portion is provided at the center of the inside of a body body, and pressure receiving portions filled with an enclosed liquid are provided on both opening surfaces of the body body. The pressure receiving portions are detected by the respective transmission pipes by the pressure detecting portion. In a differential type differential pressure transmitter, which communicates with a chamber and communicates both of the transmission pipes through a branch pipe having an orifice, the differential pressure transmitter of the one pressure receiving portion is brought into contact with the diaphragm of the pressure receiving portion. A pressure parallel means having a balance bellows filled with a static pressure applying member for applying a pressure opposite to the measured pressure and an exchangeable balance spring for biasing the smoothing bellows against the diaphragm of the pressure receiving portion. A differential type differential pressure transmitter characterized by being provided.