JPS60186726A - Pressure transducer - Google Patents

Abstract

PURPOSE:To reduce the weight of the pressure transducer and to attain its mass- production by welding the projection part of an intake part to the peripheral part of a pressure receiving diaphragm electrically and forming integral constitution. CONSTITUTION:The thin annular projection part 12e which covers a large- diameter opening part 12d and has the same height is formed at the intake part 12 where fluid as a pressure medium is admitted. The pressure receiving diaphragm 13 is formed of a material which has nearly the coefficient of expansion with the intake part 12 into a disk thin enough to deform by sensing the pressure of the fluid. Then when the transducer is assembled, the peripheral edge part of the diaphragm 13 abuts on the projection part 12e and a large current is fed from an electrode 14 which presses the diaphragm to weld both in one body.

Description

Detailed Description of the Invention (a) Technical Field The present invention deforms a pressure receiving diaphragm using fluid as a pressure medium, detects the deformation of the pressure receiving diaphragm with a strain gauge attached to the diaphragm, and responds to the applied pressure. It relates to a pressure transducer that obtains electrical signals.

(b) Prior Art Conventionally, this type of pressure transducer has been constructed as shown in FIG. 1, for example.

In Fig. 1, reference numeral 1 denotes an introduction for connecting and fixing this pressure transducer to a device, container, pipe line, etc. as a pressure detection object, and introducing fluid such as gas or liquid as a pressure medium from the object. Department. This introduction part 1 has a through hole 1a as a fluid introduction path in the center, and a threaded part 1b as a mounting part is formed on the outer circumferential surface of one end, and the other end has a step with respect to the threaded part 1b. A large-diameter portion 1 having a substantially flange-like shape and threaded on its outer peripheral surface in the same manner.
c. , 2 is an outer cylinder portion formed in a cylindrical shape, one end of which is a threaded portion 2a that is threaded on the inner peripheral surface, and is formed on the outer periphery of the large diameter portion 1c of the introduction portion 1. It is screwed into the threaded part and welded to the introduction part 1 by welding or the like. Further, a thin plate-shaped pressure receiving diaphragm 2b is integrally formed in the middle of the outer cylinder portion 2 so as to close the hollow portion thereof. Then, the back surface of this pressure receiving diaphragm 2b (
A strain gauge 3 that deforms together with the pressure receiving diaphragm 2b and converts the pressure applied to the pressure receiving diaphragm 2b into an electrical signal is attached to the surface opposite to the pressure receiving surface using an adhesive or the like. Reference numeral 4 denotes a relay board fixed to the other end of the outer cylinder part 2 and electrically connected to the strain gauge 3. Reference numeral 5 indicates a case in which one end is fixed to the outer periphery of the protruding end of the outer cylindrical portion 2 by welding or the like, and reference numeral 6 indicates one end that is fitted into the other end of the case 5 and electrically connected to the relay board 4 to provide a conversion output (electrical output) to the outside. signal)
7 is a fixture for fixing the waterproof connector 6 to the case 5, and 8 is an O-ring for sealing the joint between the case 5 and the waterproof connector 6.

With such a configuration, fluid such as liquid or gas led from the object such as a pressure vessel through the introduction part 1 deforms the pressure receiving diaphragm 2b due to its pressure, and the fluid attached to the pressure receiving diaphragm 2b is The strain gauge 3 detects strain and obtains an electrical signal output corresponding to the applied pressure.

By the way, among the members constituting this pressure transducer, the outer cylinder portion 2 including the pressure receiving diaphragm 2b is integrally formed by cutting a bar-shaped steel material such as stainless steel with a lathe or the like. By integrally forming the pressure-receiving diaphragm 2b in this manner, the relationship between the output of the strain gauge 3 and the fluid pressure from the object is made linear, hysteresis is reduced, and a highly accurate and stable pressure transducer can be obtained. .

However, when processing the outer cylinder portion 2 in this manner, there were several problems.

First, the processing of the outer cylindrical portion 2 requires a large number of so-called machining steps, such as thread cutting of the threaded portion 2a, cutting of the pressure receiving diaphragm 2b, and cutting of the outer peripheral surface and end face. It must be formed into a thin plate shape and requires extremely high precision, so the cutting process requires careful attention and takes a long time.Thirdly,
When assembling the pressure transducer, especially when screwing the introduction part 1 and the outer cylinder part 2 together, there is a risk that the pressure receiving diaphragm 2b may be deformed and the zero point of the conversion output may fluctuate, so be very careful during the assembly work. Fourthly, there is a problem regarding the material of the pressure receiving diaphragm 2b. That is, it is essential for the pressure receiving diaphragm 2b to have corrosion resistance against liquids and fluids as a pressure medium for long-term stability.
Since it is attached, the material must have high tensile strength. Conventionally, the pressure receiving diaphragm 112b
There were some that used austenitic stainless steel such as 18-8 stainless steel, but in this case there was no problem in terms of corrosion resistance, but there were some problems in terms of tensile strength. In addition, 18-8 stainless steel does not harden even after heat treatment and cannot be used as an elastic diaphragm, but it shows remarkable work hardening properties when rolled into a thin plate. If the outer cylindrical portion 2 can be rolled to form a diaphragm, it can be used satisfactorily, but due to its shape, rolling is practically impossible.

On the other hand, when precipitation-hardened stainless steel such as 17-JPH steel is used as a material, it is possible to obtain an extremely high-precision pressure transducer that satisfies both corrosion resistance and tensile strength. Since the pressure transducer itself is expensive and machining is relatively difficult, there is a problem in that the cost of the pressure transducer increases significantly. In order to avoid this problem, if the material of the introduction part 1 is made of a different material from the material of the outer cylinder part 2, if the expansion coefficients of these parts are different, when a temperature change occurs in the pressure transducer.

A new problem is that thermal strain (thermal stress) occurs at the threaded portion of the large diameter portion 1c of the introduction portion 1 and the threaded portion 2a of the outer cylinder portion 2, deforming the pressure receiving diaphragm 2b and causing errors. occurs. Therefore, it is necessary to use a material for the introduction part 1 that is the same as the outer cylinder part 2, or at least one that can be considered to have the same expansion coefficient.For example, the outer cylinder part 2 must be made of expensive material such as 17-4PH steel If 17-4PH steel is used for the introduction section, the cost of the pressure transducer as a whole cannot be reduced.

Under these circumstances, the demand for pressure transducers has increased with the recent increase in the number of various hydraulic control equipment, etc., and there is a desire in the market for lower-priced pressure transducers to be supplied in large quantities. .

Therefore, one of the countermeasures is not to use the introduction part 1,
A possible method is to reduce the number of members by configuring the threaded part 2a of the outer cylinder part 2 to be directly attached to the object, thereby reducing costs. However, in the case of this method, when the introduction part 1 is screwed onto the object, stress is generated in the threaded part 2a, and the stress may deform the pressure receiving diaphragm 2b, causing initial fluctuation (initial movement). . Therefore, there are various restrictions in putting it into practical use. Also,
It would be good if it were possible to manufacture a member that integrated the introduction part I and the outer cylinder part 2, but this is not possible due to its shape.

Furthermore, as another measure, it is conceivable to configure the outer cylinder portion and the diaphragm as separate members as shown in FIG. That is, the introduction part 9 is similar to the introduction part l shown in FIG. An edge portion having a shape like this], Ob is formed. Then, the pressure receiving diaphragm 11 formed in the shape of a thin disk is held between the other end surface of the introduction part 9 and the edge part tab of the outer cylinder part 10 screwed thereto. When configured in this way, the pressure receiving diaphragm 11 is
Since it is a separate member, the pressure receiving diaphragm 11 can be made of, for example, 17-4 PH steel, and it is also possible to use an inexpensive one.
Since it is possible to increase the tensile strength by rolling 8-8 stainless steel and work hardening it, it is possible to manufacture a pressure transducer that is cheaper than conventional pressure transducers. However, simply sandwiching the pressure receiving diaphragm 11 in the introduction section 9 in this way does not allow the pressure receiving diaphragm 11 to be securely fixed without generating stress at the peripheral edge thereof, so that hysteresis in the output of the strain gauge 3 becomes large and the accuracy of the pressure transducer deteriorates.

In the end, with conventional pressure transducers, if you try to manufacture a pressure transducer with high precision and long-term stability, it becomes expensive.
On the other hand, there is a problem in that the accuracy decreases when costs are reduced.

(C) Purpose The present invention was made in view of the above-mentioned problems, and its purpose is to reduce cost, weight, and mass production without causing deterioration of characteristics and sensitivity compared to conventional ones. The object of the present invention is to provide a pressure transducer that can realize the following.

(d) Structure The present invention is characterized by deforming a pressure receiving diaphragm using fluid as a pressure medium, detecting the deformation of the pressure receiving diaphragm with a strain gauge attached to the pressure receiving diaphragm, and generating an electric signal corresponding to the applied pressure. In the pressure transducer to be obtained, a mounting portion is formed at one end so as to be able to be coupled and fixed to a pressure detection object, and an introduction passage is bored through from one end side to the other end to guide the fluid from the pressure detection object. and an introduction part having a thin protrusion of the same height formed on the end face of the other end so as to surround the outlet of the introduction passage, and a material having at least the same expansion coefficient as the introduction part. It consists of a pressure receiving diaphragm formed in a plate shape that is thin enough to be deformed in response to the pressure of a fluid, and the protruding part of the introduction part and the peripheral edge of the pressure receiving diaphragm are welded together by electric welding. It is located in the configuration.

Hereinafter, the present invention will be explained in detail based on an illustrated embodiment.

FIG. 3 is a longitudinal sectional view showing the configuration of an embodiment of the present invention.

In the figure, an introduction part 12 that is fixedly connected to a container, a pipe line, etc. as a pressure detection object and introduces a fluid as a pressure medium has a through hole 12a, which is an introduction path for the fluid, formed in the center. A threaded portion 12b as a mounting portion is formed on the outer circumferential surface of one end, and a large diameter portion 12, c, which has a substantially flange shape with a step relative to the threaded portion 12b, is formed on the other end.
Further, a large diameter opening 12d is formed, which has a diameter smaller than the diameter of the large diameter portion 12c and larger than the diameter of the through hole 12a, and reaches a predetermined depth from the other end surface. A thin, ring-shaped protrusion 12e having the same height is formed on the other end surface of the introduction part 12 so as to surround the large diameter opening 12d that communicates with the outlet of the through hole 12a. There is.

On the other hand, the pressure-receiving diaphragm 13 is formed into a disc-shaped material that is rolled separately from the introduction section 12 and made of a material having at least the same expansion coefficient as the introduction section 12, and is thin enough to deform in response to the pressure of the fluid. is formed. Then, when assembling, the peripheral edge of the pressure receiving diaphragm 3 is brought into contact with the protrusion 12e formed protrudingly on the other end surface of the introduction part 12,
In this state, a large current (about several hundred to several tens of KA) is generated between the introduction part 12 and the electrode 14 pressing the pressure receiving diaphragm 13.
When electricity is applied, this current passes through the contact surface between the protrusion 12e and the pressure receiving diaphragm 13, that is, the ring-shaped contact area with a small contact area, so that the current passes through a part of the protrusion 12e and the pressure receiving diaphragm 13. The joint will melt. As a result, the introduction part 12 and the pressure receiving diaphragm 13 are welded and integrated, and the other end of the introduction part 12 is closed. According to this resistance welding method, welding can be performed in an extremely short time, and the heat generated during welding is localized, so there is no thermal effect.

There is almost no deformation or change in characteristics of the pressure receiving diaphragm 13 due to residual stress.

FIG. 4 is a schematic cross-sectional view for explaining another method of electric welding. What is shown in this figure is electron beam welding (
When an electron beam (electron beam) accelerated at a high voltage of tens of thousands of volts in a vacuum by an electron gun 15 hits the pressure receiving diaphragm 13, shock heat is generated locally, and this heat causes the pressure receiving diaphragm to 13 to the protruding part L2e of the introduction part 12, melting progresses in a wedge shape, and as a result, the introduction part 12
and the pressure receiving diaphragm 13 are welded together. According to this electron beam welding, unlike in the case of resistance welding, the object to be welded does not need to be a conductor, and welding can be performed in a short time and extremely locally, and the weld can be made strong. Also, like resistance welding, thermal effects and residual stress are extremely low.

Of the pressure-receiving diaphragm 13 welded to the introduction part 12 in this way, on the surface (back surface) opposite to the pressure-receiving surface that receives fluid pressure, there are four strain gauges Gl as shown in FIG. 5(a). , G2. G3 and G4 are attached on a line perpendicular to the center line of the pressure receiving diaphragm 13. Among these strain gauges 61 to G4, a strain gauge Gl is attached to a position near the periphery of the pressure receiving diaphragm 13.

As shown in FIG. 5(b), G4 detects compressive strain when the pressure receiving diaphragm 13 receives fluid pressure, and is also connected to a strain gauge G2 attached near the center of the pressure receiving diaphragm 13. G3 detects tensile strain. These strain gauges G1-04 have, for example, strain gauges G1 and G4 that detect compressive strain on opposite sides, and strain gauges G2 and G4 that detect tensile strain. A Wheatstone bridge is assembled with G3 as the other opposite side, and by applying a bridge power source to the input end of this bridge, an electrical signal corresponding to the fluid pressure can be obtained from its output end.

By the way, since the pressure receiving diaphragm 13 has a flat plate shape, it can be formed from various materials by rolling, as long as it can be considered to have at least the same coefficient of expansion as the introduction part 12. For example, introduction part 1
The pressure receiving diaphragm 13 can be made of a bar made of 18-8 stainless steel that has been cut, and the pressure receiving diaphragm 13 can be made of 18-8 stainless steel that has been cold-worked by rolling. Incidentally, when comparing the mechanical properties of this 18-8 stainless steel, when it is used as a bar, the yield strength is 21 kg f/wn" and the tensile strength is 5.
Although it is only 3 kgf/n1n', by rolling it, the yield strength becomes 48 kgf 7 mm" and the tensile strength becomes 8.
0kgf/mm". Therefore, in the case of bar material, there has been a problem with the tensile strength of the pressure receiving diaphragm I3, but the rolled material has increased tensile strength, so there is no problem at all. .Furthermore, if the price of the material is not important, one can be used as the introduction part 12 and the pressure receiving diaphragm
Precipitation hardening stainless steel such as 7-4PH11 may also be used. Incidentally, the mechanical properties of this +7-4I)H steel are
Resistance! 20kgf 1rtrn”, tensile strength is 1
Since it is as high as 34 kg f/mm2, a transducer with a higher output can be manufactured.

According to the embodiment configured as described above, the pressure receiving diaphragm 13 can be formed separately from the fluid introduction part 12 and in the form of a flat plate, so that it can be freely formed by rolling, polishing, etc., and can be formed with extremely high precision. A pressure-receiving diaphragm 13 can be manufactured.

In addition, the introduction part 1 that supports the pressure receiving diaphragm I3 is also provided.
We adopted a method of making it separate from 2 and fixing it by welding, but
Rather than simply welding, this method involves forming a ring-shaped protrusion 12e on the end face of the introduction part 12, and welding the protrusion 12e and the peripheral edge of the pressure receiving diaphragm 13 by resistance welding, beam welding, or the like. Since this is adopted, the pressure receiving diaphragm 13 can be firmly fixed to the introduction part 12 with little influence of heat and residual stress, and the non-linearity between the strain of the pressure receiving diaphragm 13 and the fluid pressure is Characteristics almost equivalent to those of the conventional method were obtained, and although the hysteresis characteristics were slightly deteriorated, the extent could be kept within the error range.

A further advantage of this embodiment is that it is possible to reduce the number of man-hours and time in the manufacturing process of the introduction section 12 and the pressure receiving diaphragm 13. That is, there is no need to form a threaded portion 1c on the introduction portion 1 as in the conventional one (shown in the first figure), and there is no need to cut the outer cylinder portion 2 using a lathe, which takes time.
It can be manufactured by punching rolled material, which is much faster than machining, so the machining time can be significantly shortened, and together with the ability to use inexpensive materials, costs can be significantly reduced. be able to.

Incidentally, when using 18-8 stainless steel as the material,
The pressure transducer of this embodiment is 175 to 1
It can be manufactured at a cost of /3. In addition, the above-mentioned 17-
When precipitation hardening stainless steel such as JPH steel is used, a pressure transducer with a large rated output and small hysteresis characteristics can be obtained. In this case, it is undeniable that the cost will be high because precipitation hardening stainless steel is expensive as a material, but since the manufacturing man-hours and the manufacturing time of the pressure receiving diaphragm 13 are significantly shortened, the pressure transducer as a whole is It can be made cheaper than conventional products.

Furthermore, since the outer cylinder part 2 (shown in the first figure) in the conventional pressure transducer can be made thinner or unnecessary, the weight can be reduced accordingly.

It goes without saying that the present invention is not limited to the embodiments described above, and that various modifications, substitutions, etc. can be made without departing from the scope of the invention.

For example, as a method for welding the introduction part 12 and the pressure-receiving diaphragm 13, other than two welding methods, other welding methods may be used as long as they do not give the pressure-receiving diaphragm 13 any influence of heat or residual stress. You may also do this. Moreover, as the material for the introduction part 12 and the pressure receiving diaphragm 13, other materials than stainless steel may be used as long as they are corrosion resistant and have high tensile strength.

(e) Effects - 1 - As described in detail, the present invention provides a pressure transducer that can be produced at a lower price, lighter weight, and in mass production without causing deterioration in characteristics or sensitivity compared to conventional ones. can be provided.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an example of a conventional pressure transducer, FIG. The figure is a longitudinal sectional view showing the configuration of an embodiment of the present invention, FIG. 4 is a partial sectional view for explaining an example of the processing method of the present invention, and FIGS. 5(a) and 5(b) are FIG. FIG. 2 is a rear view and a partial vertical cross-sectional view for explaining the operation of the embodiment shown in FIG. 12...Introduction part, 12a...Threaded part, 12c...Large diameter part, 12d...Large diameter Opening, 12e...
Projection, 13... Pressure receiving diaphragm. 14... Electrode, 15... Electron gun, 6
1~G4...Strain gauge. Figure 1 Figure 2 Figure 3 Cause Figure 5 (0) (b)

Claims (1)

[Claims] (1) In a pressure transducer that deforms a pressure receiving diaphragm using fluid as a pressure medium and detects the deformation of the pressure receiving diaphragm with a strain gauge attached to the pressure receiving diaphragm to obtain an electric signal corresponding to the applied pressure, the pressure detection target is A mounting portion is formed at one end so as to be able to be coupled and fixed to the object, and an introduction path penetrating from one end to the other end is bored in order to guide the fluid from the pressure detection object, and further, the An introduction part having a thin protrusion of the same height formed so as to surround the outlet of the introduction passage, and a material having at least the same expansion coefficient as the introduction part, which can be deformed in response to the pressure of the fluid. The pressure receiving diaphragm is formed into a fairly thin plate shape, and the projecting part of the introduction part and the peripheral edge of the pressure receiving diaphragm are integrally welded together by electric welding. pressure transducer.