JPS5930442Y2 - Force balanced differential pressure transmitter - Google Patents

Description

[Detailed description of the invention] This invention relates to a force-balanced differential pressure transmitter that extracts the sound of a change in differential pressure as the displacement of a force rod and transmits it as, for example, an air pressure signal, and particularly relates to a measuring pressure receiving element and a measuring pressure receiving element. It is an object of the present invention to provide a force-balanced differential pressure transmission system that does not cause output errors even if a pin connecting the force rod is deformed due to temperature change.

Figure 1 shows a conventional force-balanced differential pressure transmitter.

1 in the figure is the body.

First and second pressure elements 2 and 3 are attached to both ends of the body 1.

In this example, a diaphragm 4 is shown as the pressure-receiving elements 2 and 3, but other pressure-receiving elements such as bellows may also be used.

A measuring pressure receiving element 4 is provided within the body 1 .

This measurement pressure receiving element 4 is also shown in the case where a pressure receiving diaphragm 4 is used in this example, but a bellows ring may be used in the same manner as described above.

Two chambers, a first chamber 5 and a second chamber 6, are formed in the body 1 by the measuring pressure receiving element 4.

These first and second chambers 5 and 6 are filled with incompressible first and second filled liquids 7.8, such as silicone oil, respectively.

On the other hand, one end side of the force rod 9 is inserted into the first chamber 5.

The force rod 9 is attached to the support member 1 at the lead-out point of the body 1.
This support point is supported by 0 so that it can rotate as a gold fulcrum.

The end of the force rod 9 and the measuring pressure receiving element 4 are connected by a sound-opening connecting pin 11, and as the measuring pressure receiving element 4 is displaced, the force rod 9 is moved sideways so as to be taken out of the body 1.

Although not particularly shown here, a pneumatic conversion device, for example, is attached to the other end of the force rod 9.

As is generally well known, in the pneumatic conversion device, for example, an air discharge nozzle is provided opposite to the lead-out end of the force rod 9, and when the force rod 9 is displaced, the gap between the force rod 9 and the nozzle is By changing the facing distance, the air discharge resistance changes, and the change in the discharge resistance converts the sound into a pneumatic signal, and the pneumatic pressure signal is transmitted to another control finely while connected to the force rond. A pneumatic pressure signal 4 proportional to the input is obtained by balancing the force generated in the feedbank element with the force transmitted from the measurement pressure receiving element on a gold force rond.

The force-balanced differential pressure transmitter with the above-mentioned structure is also commonly referred to as a force-balanced differential pressure transmitter with a three-layer membrane and two-chamber structure. ,
The measuring pressure receiving element 4 is displaced by an amount corresponding to the differential pressure, and the force rod 9 is moved.

Therefore, the differential pressure sound can be measured based on the amount of displacement of the force rod 9 (7).

By adopting the structure in which the pressure to be measured is applied to the measurement pressure receiving element 4 via the blade metal pressure receiving element 2 or 3 and the sealed liquid 7 or 84, the measurement pressure receiving element 4 is made of a material with high corrosion resistance because it does not come into contact with the fluid to be measured. Therefore, it is possible to select a material with excellent spring properties that is suitable for the measurement pressure receiving element.
Material 4 can be selected only for the second pressure-receiving elements 2 and 3 in consideration of corrosion resistance.

By the way, in the above-mentioned force-balanced differential pressure transmitter having a three-layer membrane and two-chamber structure, when temperature fluctuations are applied, the measurement pressure receiving element 4 and the connecting pin 11 expand and contract, and this expansion and contraction causes the force rod 9 to be displaced. However, the disadvantage is that the output fluctuates.

For this reason, in the past, the ratio of the volumes of the first and second chambers was appropriately selected, and the measuring pressure receiving element 4 was appropriately displaced in response to temperature fluctuations by the expansion and contraction of the first and second sealed liquids 7, 8, and the force was applied. The displacement of the rod 9 is canceled out.

However, it is difficult to uniformly determine a value suitable for eliminating the effects of expansion and contraction of the volumetric sound measuring pressure receiving element 4 and the connecting pin 11 in the first and second chambers 5 and 6, and the The volume 4 has to be changed little by little, which requires a lot of manpower and time 4 , resulting in high costs and disadvantages that are an obstacle to mass production.

However, even if the influence of the expansion and contraction of the measuring pressure receiving element 4 and the connecting pin 11 can be canceled out by the ratio of volume changes of the filled liquids I and 8, the expansion and contraction of the measuring pressure receiving element 4 and the connecting pin 11 It is not possible to match the time constants of the expansion and contraction of the fill liquids 7 and 8 with gold.

Therefore, transient output fluctuations occur during the process of temperature change.

Therefore, the conventional force-balanced differential pressure transmitter of this type has the disadvantage that it cannot completely eliminate the noise generated by output fluctuations due to temperature fluctuations.

The purpose of this invention is to obtain a force-balanced differential pressure transmitter 4 that does not require adjustment and does not cause fluctuations in output due to temperature fluctuations.

In this invention, a compensating spring metal is provided at the border of the force rod in the opposite direction to the measuring pressure receiving element, and the compensating spring and the force rod are connected by a second connecting hinge, and the compensating spring and the second The expansion and contraction of the connecting pin cancels out the influence of the expansion and contraction of the measuring pressure receiving element and the connecting pin.

An embodiment of this invention will be explained in detail below using FIG. 2 and FIG.

In FIG. 2, parts corresponding to those in FIG. 1 are designated with the same reference numeral 4, and redundant explanation thereof will be omitted, but a first pressure receiving element 2 and a second pressure receiving element 3 are attached to both end surfaces of the body 1, and A measurement pressure receiving element 4 is installed in a chamber in the body 1, and first and second chambers 5 and 6 are formed in the body 1, and the measurement pressure receiving element 4 and the force rod 9 are connected by a quantitative connection pin 11. The structure is the same as before.

For this invention, a compensating spring 12 is provided on the opposite side of the force rod 9 from the measuring pressure receiving element 4, and a second connecting pin 13 is connected between the compensating spring 12 and the force rod 9.
It is connected by.

In this example, the compensating spring 12 is shown as 4 when a pressure-receiving diaphragm similar to the measuring pressure-receiving element 4 is used.

For this reason, the first chamber 5 was previously divided into two by the compensation spring 12, but since the pressure applied to the first pressure receiving element 2 is no longer transmitted to the measuring pressure receiving element 4, a flow path 14 is formed using gold. 14 so that the pressure applied to the first pressure receiving element 2 is transmitted to the measurement pressure receiving element 4 via the first sealed liquid 7 gold.

Note that when the compensating rigid spring 124 is shaped as shown in FIGS. 3 to 5, it is not necessary to form the flow path 14 gold.

In the above configuration, the connecting pin 11 and the second connecting pin 13
The spring constant of the compensating spring 12 and the amount of deformation due to temperature are selected to be approximately equal to that of the measuring pressure receiving element 4, so that the deformation of the measuring pressure receiving element 4 and the expansion and contraction of the connecting pin 11 The influence caused by the compensation spring 12
This can be canceled out by a change in , or by expansion and contraction of the second connecting pin 13 .

Therefore, it is possible to obtain a force-balanced differential pressure transmitter 4 in which output fluctuations do not occur due to flow rate fluctuations.

In the embodiment shown in FIG. 2, first and second
Although the example in which the pressure receiving elements 2 and 3 are directly attached has been explained, as an example of other types, for example, as shown in the sixth page, the pressure receiving elements 2 and 3 are directly attached.
Both or either one of them is attached to the gold pressure receiving flange 15, and the capillary 16 between the pressure receiving flange 15 and the body 1 is
It is easy to understand that this idea can also be applied to force-balanced differential pressure transmitters of the type communicated by.

[Brief explanation of drawings]

Fig. 1 is a sectional view for explaining the conventional force balance type differential pressure transmission mechanism, Fig. 2 is a sectional view of an embodiment of this invention, and Fig. 3
5 to 5 are front views showing another embodiment 4 of the compensation spring used in this invention, and FIG. 6 is a sectional view of another embodiment of the invention. 1... Body, 2... First pressure receiving element,
3... Second pressure receiving element, 4... Measurement pressure receiving element, 5... First vacant chamber, 6... Second vacant chamber, 7... ...First sealing liquid, 8...Second sealing liquid, 9...Force rod, 11, 13...
...Connecting pin, 12... Compensation spring.

Claims (1)

[Scope of utility model registration request] A first pressure receiving element, a measurement pressure receiving element, a first chamber formed between the first pressure receiving element and the measurement pressure receiving element, an incompressible first sealed liquid filled in the first chamber, and the above measurement pressure receiving element. a second pressure receiving element provided on the opposite side of the first pressure receiving element with the pressure receiving element as a boundary; a second chamber formed between the second pressure receiving element and the measurement pressure receiving element; a force rod having one end inserted into the first chamber; a connecting pin connected between the measurement pressure receiving element and the force rod to transmit the displacement of the measurement pressure receiving element to the force rod; In the force-balanced differential pressure transmitter, a compensating spring provided in the first chamber and connected to the force rod, and a second connecting pin connecting the compensating spring and the force rod are provided. , a force-balanced differential pressure transmitter formed by horizontally striking the rond to compensate for the displacement caused by the temperature change of the measuring pressure-receiving element and the connecting pin, which is offset by the deformation of the second connecting pin due to the temperature change. .