JPH0459573B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for fixing a diaphragm to a body in a pressure transmitter, differential pressure oscillator, etc.

Liquid ring type pressure oscillators and differential pressure starters are equipped with a disc-shaped diaphragm that transmits external pressure to the internal liquid. A method is adopted in which the diaphragm is sandwiched between the two, and the main body and washer are welded together at the peripheral edge. FIG. 1 is a cross-sectional view of the vicinity of the outer periphery of the diaphragm of a differential pressure oscillator shown to explain a conventional fixing method. and ring 4 are stacked on top of each other, and the peripheral edges of body 1 and ring 4 are welded together, and after welding, body 1 and cover 2 are fastened together with bolts (not shown).

Since such a conventional diaphragm fixing method involves welding the plate-shaped ring 4, various problems have occurred after welding and during use of the instrument. That is, while the outer circumferential portion of the ring 4 contracts due to welding, the inner circumferential portion does not, so that the entire ring 4 is distorted and the inner circumferential portion bulges in a direction away from the body 1, forming a dish-like shape. Therefore, as shown in FIG. 1, a gap is created between the body 1 and the ring 4, and the diaphragm 3 is left in a free state without being held at its outer periphery. In this condition, the sealing liquid 5
If the amount of filled liquid changes due to a change in the temperature of the fluid to be measured after the diaphragm 3 is filled, the diaphragm 3, which was moving around the inner peripheral edge P of the body 1 as a fulcrum up to a certain point, will expand beyond a certain amount. It begins to move with the welding point _P1 as a fulcrum, and as a result, the volume-pressure coefficient, which is the ratio of volume change to pressure change, changes. Therefore, when the relationship between temperature and pressure is expressed in a diagram, it is not a straight line, and it is extremely difficult to correct this electrically, making it difficult to obtain accurate measurement results. In addition, since the diaphragm 3 is soft, it may separate from the joint surface of the body 1 after welding as shown in Figure 2. If the cover 2 is tightened in this state, the position of the diaphragm 3 will be pushed downward in the figure. There is a problem that the internal fluid pressure increases and a zero shift occurs. Furthermore, when the distorted ring 4 is forcibly pressed and tightened with the cover 2, the ring 4 breaks, and welding has to be repeated again.

The present invention was made in view of the above points, and a ring for fixing a diaphragm is formed in the shape of a disc spring with an inner circumference and an outer circumference shifted in the axial direction,
The inner peripheral edge of this ring is pressed against the diaphragm on the annular surface of the body, and the outer peripheral edge is pressed toward the diaphragm to elastically deform it into a flat plate. In this state, the ring, diaphragm, and outer peripheral edge of the body are integrated. The present invention provides a method for fixing a diaphragm that ensures close contact between the diaphragm and the body by welding, and prevents damage to the ring during welding. Hereinafter, a detailed explanation will be given with reference to embodiments shown in the drawings.

FIG. 3 is a sectional view of a differential pressure oscillator for explaining the method of fixing a diaphragm according to the present invention, and FIG. 4 is a sectional view of a ring. In the figure, the differential pressure oscillator 11 is integrally formed with a pressure receiving part 12 and a transmitting part 13, and the pressure receiving part 12 is provided with a sensor chamber 14 that houses a sensor connected to the starting part 13. The pressure receiving part 12 includes a cylindrical body 15, and at both ends thereof, an internal chamber 16 on the high pressure side and an internal chamber 17 on the low pressure side are surrounded by an annular joint and a diaphragm 18, which will be described later. It is set up. Further, both inner chambers 16 and 17 and the high pressure side and low pressure side of the sensor in the sensor chamber 14 are communicated with each other through inner sealing liquid passages 19 and 20, and the inner chamber 1
A sealing liquid 21 such as silicone oil is sealed inside the sealing liquid passages 6 and 17 and the sealing liquid passages 19 and 20. A pair of covers 22 are fastened to the body 15 by a plurality of bolts 23 passing through the flange of the body 15, and a diaphragm 18 and a ring 25, which will be described later, are connected between the annular surface 24 of the body 15 and the annular surface 24 of the body 15. It has an annular surface 26 that is joined through the annular surface 26, and an O-ring 27 for airtightness is mounted on the annular surface 26. Also,
Holes 28 and 29 are formed in the cover 21, respectively, so that the inner chamber of the cover 22 communicates with the high-pressure side and the low-pressure side of the process, respectively.

Next, the configuration of the diaphragm 18 and ring 25 and the method of fixing the diaphragm 18 will be explained. The diaphragm 18 is formed into a disk shape with a corrugated cross section and concentric irregularities, and its outer peripheral portion is joined to the annular surface 24 of the body 15. Further, the ring 25 as an annular washer is formed into an annular shape when viewed from above, and the inner circumferential circle and the outer circumferential circle are shifted by an amount indicated by the symbol t, as shown in FIG. ing. In order to fix the diaphragm 18 and the ring 25 configured in this way, the diaphragm 18 and the ring 25 are held between the annular surface 24 of the body 15 and the annular surface 26 of the cover 22, and then the bolt 23 is tightened to secure the body. 15 and the cover 22 are fastened. In this case, the ring 25 is inserted so that the inner peripheral surface side, which is the small diameter portion, faces the diaphragm 18 side. When fastened in this manner, the ring 25 is elastically deformed by the fastening pressure to become a flat plate, and a force that presses the diaphragm 18 against the annular surface 24 of the body 15 is accumulated therein. In this state, the periphery of the body 15 and the periphery of the ring 25 are welded together to form a welded portion 30.

In the differential pressure oscillator in which the diaphragm 18 is fixed as described above, the pressure in the high pressure section in the process pipe is transferred to the diaphragm 18 on the high pressure side through the hole 28.
When the pressure of the low pressure part is applied to the low pressure side diaphragm 18 through the hole 29, the high pressure is guided to the high pressure side of the sensor via the internal sealing liquid 21, and the low pressure is introduced via the internal sealing liquid 21. and is guided to the low pressure side of the sensor. The sensor detects the differential pressure between high and low pressure, converts it into an electrical signal, and sends it out.

In the method of fixing the diaphragm 18 in the differential pressure oscillator 11 that operates in this way, a ring 25 formed in a dish shape is inserted with the small diameter part located on the diaphragm 18 side, and the ring 25 is flattened with a cover 22 and fixed to the diaphragm. By configuring so that the welding is performed while the pressing force on 18 is accumulated,
Due to the welding, even if the outer circumference of the ring 25 contracts, the inner circumference of the ring 25 does not separate from the diaphragm 18, and the accumulated force presses the diaphragm 18, bringing the diaphragm 18 and the ring 25 into planar contact.

FIG. 5 is a sectional view of an annular washer 25A as a ring showing another embodiment of the present invention, in which the tapered surface is formed into an arc shape instead of a straight line in the embodiment shown in FIG. be.

Although each of the above-mentioned embodiments shows an example in which the present invention is implemented in a differential pressure transmitter, the present invention can be similarly implemented in a pressure transmitter that measures pressure at one location.

As explained above, according to the present invention, the annular washer for fixing the diaphragm is formed in the shape of a disc spring in which the inner circumference and the outer circumference are shifted in the axial direction, and the inner circumferential edge side of the annular washer is formed on the annular surface of the body. By applying pressure to the upper diaphragm and pressing the outer periphery toward the diaphragm, it is elastically deformed into a flat plate shape, and in this state, the annular washer, diaphragm, and outer periphery of the body are welded together. Even if the outer periphery of the annular washer contracts, the inner periphery will not separate from the diaphragm, and the annular washer makes plane contact with the diaphragm to firmly fix it.
The fulcrum of motion of the diaphragm does not change even if the temperature of the fluid to be measured changes, and the volume-pressure coefficient remains constant regardless of temperature changes, resulting in highly accurate measurement results that do not require correction. This improves measurement accuracy. The diaphragm does not move toward the compression side of the sealed liquid, and zero shift due to an increase in liquid pressure can be prevented from occurring. Further, since there is no need to forcefully press a distorted annular washer after welding, the welded portion does not crack, and material costs and labor for re-welding can be reduced.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of the vicinity of the outer periphery of the diaphragm of a differential pressure transmitter shown for explaining the conventional diaphragm fixing method, respectively, and FIG. 3 is a cross-sectional view for explaining the diaphragm fixing method according to the present invention. FIG. 4 is a sectional view of the pressure transmitter, FIG. 4 is a sectional view of the ring, and FIG. 5 is a sectional view of the ring shown for explaining another embodiment of the present invention. 15...Body, 18...Diaphragm, 22
...cover, 24 ... annular surface, 25 ... ring,
30...Welded part.

Claims (1)

[Claims] 1. A method in which a diaphragm is interposed between an annular surface of a body and a ring, and the diaphragm is fixed to the body by welding the outer peripheries of each, and the ring is a disc spring in which the inner and outer peripheries are offset in the axial direction. The inner peripheral edge of the ring is pressed against the diaphragm on the annular surface of the body, and the outer peripheral edge is pressed toward the diaphragm to elastically deform it into a flat plate. In this state, the ring, diaphragm, and body are A diaphragm fixing method characterized by welding the outer periphery together.