JPH01109232A - Fine differential pressure transducer - Google Patents

Abstract

PURPOSE:To detect differential pressure with high accuracy by the small-sized, low-price transducer which is easily manufactured and has extremely small capacity by providing a strain gauge to the strain inducing part of the thin cylinder part of the transducer main body. CONSTITUTION:When 1st and 2nd liquids to be measured are admitted from left and right pressure leading-in paths 1d and 1e and the pressure P1 and pressure P2 of two systems to be measured are applied to diaphragms 2a and 2b, the diaphragms 2a and 2b bend because of the pressure difference between P1 and P2 to be measured and become stable where P1 and P2 balance with each other. Then support members 3a and 3b and a connecting rod 6 are all displaced from a high-pressure side to a low-pressure side. As the support members 3a and 3b are displaced, strain inducing parts 25 and 30 of transducer main bodies 20 and 30 bend and strain gauges expand or contract. Those strain gauges form a Wheatstone bridge circuit and an electric signal corresponding to the pressure difference (¦P1-P2¦ between the 1st and 2nd liquids to be measured is obtained from the bridge output terminal to detect fine differential pressure.

Description

Detailed Description of the Invention (a) Technical Field The present invention relates to a micro differential pressure transducer, and more specifically, the present invention relates to a micro differential pressure transducer that converts the micro pressure of two systems of fluids to be measured introduced through two pressure introduction paths. This invention relates to a minute differential pressure converter that detects a difference and converts it into an electrical quantity.

(b) In a conventional differential pressure transducer, a strain-generating portion is disposed within a pair of diaphragms (or bellows) that receive the pressure of two systems of fluid to be measured, and deforms in accordance with the pressure difference between the two systems. Broadly speaking, there are diaphragm types, double-end support beam types, and cantilever support beam types.

FIG. 4 is a sectional view showing the configuration of a conventional differential pressure converter.

In the figure, 51 is a casing, inside which a substantially cylindrical space is formed, and at both ends of the casing in the direction of the sensitive axis (in the left and right direction in the figure), there are pressure introduction parts connected to the object to be measured. 52 and 53 are provided in a protruding manner, and pressure introduction passages 54 and 55 communicating with the space are formed in the center thereof. A pair of diaphragms 5 which are substantially parallel to each other so as to be substantially perpendicular to the sensing axis direction are located near the pressure inlet passages 54 and 55 in this space.
6.57 is installed in an airtight state.

In this way, the area surrounded by the two diaphragms 56 and 57 and the inner wall of the casing 51 forms a sealed chamber completely cut off from the outside air. This sealed room has bellows 58
The bellows 58 is divided into two parts in terms of volume by a pressure receiving plate 59 that closes the end surface of the bellows 58 and a bellows mounting plate 60 that fixes the other end of the bellows 58 to the inner wall of the casing 1 in a sealed state. A force transmitting rod 6 is attached to the pressure receiving plate 59.
A strain diaphragm 62 is connected via 1. At least four strain gauges SG are bonded to the circumferential edges of both sides of the strain diaphragm 62 in the illustrated case.

Here, the left sealed chamber divided by the bellows 58, the pressure receiving plate 59, etc. will be referred to as a first sealed chamber 63, and the right sealed chamber will be referred to as a second sealed chamber 64. These, the first and second
A liquid for pressure transmission is sealed in the sealed chambers 63 and 64.

The operation of the conventional differential pressure converter configured as described above will be explained.

A first fluid to be measured and a second fluid to be measured are respectively introduced from the left and right directions in FIG.
and 57, the respective diaphragm 5
6 and 57 are bent (deformed) in accordance with the measured pressures P4 and P2 to form the first and second sealed chambers 63.
The pressure inside the chambers 63 and 64 changes, and the pressure receiving plate 59 moves from the high pressure side to the low pressure side and stops at a position where the pressures in both sealed chambers 63 and 64 are balanced. As the pressure receiving plate 59 moves (displaces), the strain diaphragm 62 bends, and the strain gauges SG attached to both sides of the strain gauge SG also expand or contract.A Wheatstone bridge (not shown) is assembled with these strain gauges SG. The pressure difference (P, -P,
) to obtain an electrical signal corresponding to the

However, conventional differential pressure transducers constructed and operated in this manner suffer from first-order drawbacks.

First, the volumes of the two sealed chambers (first and second sealed chambers) 63 and 64 divided into two are designed to be the same, but due to processing and assembly errors, they are actually strictly the same. Since it cannot be made into a volume, there is a disadvantage that when a temperature change occurs, the pressure receiving plate 59 is displaced due to expansion and contraction due to the temperature, and this is mixed into the pressure measurement value, giving a large error.

Second, if the above 1. Even if a product with no difference in volume between the second sealed chambers 63 and 64 is obtained by chance, the pressure transmitting liquid filled in the two sealed chambers 63 and 64 (
In general, there is a high possibility that air bubbles will be mixed into the oil), and the amount of air bubbles, that is, the air content, is
3.64, therefore both sealed chambers 63.6
As a result, the coefficient of thermal expansion of each liquid in 4 is different, and as expected,
1st. There is a drawback that a differential pressure is generated between the second sealed chambers 63 and 64, and this is mixed into the measured value and causes an error.

The above-mentioned first and second drawbacks are a big problem especially when measuring minute differential pressures.

Thirdly, the above 1. In order to solve the second drawback, applying temperature compensation requires a lot of cost and man-hours, and the product price increases significantly.In addition, it is not always possible to provide sufficient temperature compensation. There is a problem.

In other words, each strain gauge generally has a different temperature coefficient of resistance, and when a Wheatstone bridge is configured, the unbalance generates heat output. To compensate for this, an appropriate temperature coefficient of resistance is set on the bridge side. It is done to insert a compensating resistor with. However, this compensation is only effective if no temperature gradients occur between the strain gauge and the compensation resistor.

However, in differential pressure transducers, in addition to the heat output due to the unbalanced temperature coefficient of resistance of the strain gauges mentioned above,
As mentioned above, the first. Heat output occurs due to structural reasons such as a difference in volume between the second sealed chambers 63 and 64 or bubbles contained in the filled liquid. The heat output of the former can be known in advance through experiments, but the latter cannot be determined until after the transducer is assembled and the pressure transfer fluid is sealed in. Therefore, the compensation resistor is the same as the strain gauge. Compensation cannot be performed within the closed chamber 67, 68 which can be considered as a temperature-affected zone; that is, compensation must be performed within a terminal box (not shown) attached outside.

However, the actual usage of differential pressure converters is as follows:
In most cases, the temperature of the fluid to be measured and the ambient temperature are different, and the temperature difference varies in each case. Therefore, a temperature gradient is created between the strain gauge and the compensation resistor, making it impossible to compensate.

Fourth, conventionally, a diaphragm, a cross beam, a cross beam, a cantilever beam, etc. have been used as the strain generating part, but we have created a strain generating part that can detect minute differential pressures. It is extremely difficult to do so, and even if it could be manufactured, it would be extremely expensive.

This drawback will be explained in more detail with reference to FIGS. 5(A), (B) and (C).

FIGS. 5(A) and 5(B) are a plan view showing the main part configuration of a conventional diaphragm type load converter, and
- An X-ray cross-sectional view, and (C) is a bending stress distribution diagram of the conventional example. Because load transducers have something in common with pressure transducers in their principle.

A load converter will be explained below as an example.

In these figures, the transducer main body 71 has an elastic, thick-walled cylindrical outer shell 72, and a small-diameter, thick-walled cylindrical load dust part that introduces the load to be measured at the center of the outer shell 72. 73, and a strain-generating portion 74 made of a thin diaphragm is connected between the outer periphery of the load dust 73 and the inner periphery of the outer shell portion 72 so that their respective surfaces are perpendicular to each other. This load transducer has four strain gauges SG each on a portion of the strain generating portion 74 near the outer periphery of the load dust 73 and a portion close to the inner periphery of the outer shell portion 72. The sensitive direction is determined so that the bending strain (stress) of the strained portion 74 can be detected, and the strained portion 74 is attached by adhesive or other means.

However, this type of load transducer has drawbacks of first order.

That is, first of all, if a low capacity diaphragm type load transducer is to be manufactured, the wall thickness of the strain generating portion 74 must be made extremely thin. However, it is very difficult to reduce the wall thickness by cutting, and there is a limit to how thin it can be (currently the limit is about 0.2 wm), and in that case, the cost becomes extremely high.

On the other hand, since there is a constraint that the wall thickness cannot be reduced below a certain level, in order to make the wall thickness up to a certain level and have a lower capacity, the inner diameter of the outer shell 72 should be increased and the thinner part (
diaphragm), but in this case, the following problem arises: 6 In other words, as the outer diameter of the strain-generating portion 74 becomes larger, the conversion inevitably increases. As the outer diameter of the main body 71 becomes larger, it becomes virtually impossible to manufacture a compact load converter, and as the bending rigidity is reduced, the response frequency inevitably decreases. This causes the problem that dynamic loads cannot be measured, and since there is a limit to structurally thin wall processing, there is a problem that a small and low-capacity load transducer cannot actually be manufactured.

Second, as shown in the stress distribution diagram of FIG. 5(C), the stress distribution change in the diametrical direction of the strain-generating portion 74 is rapid, and it is difficult to attach a strain gauge to the position where the maximum stress occurs. Since this is not possible, the strain detection efficiency is poor, and the stress change rapidly decreases, resulting in a decrease in the average detection sensitivity of the strain gauge as a whole. That is, it has the disadvantage of low strain detection efficiency and low strain detection sensitivity.

Thirdly, as described above, even if the strain detection efficiency is low, it is necessary to output a required strain detection output, so a very large stress is substantially generated in the strain-generating portion (diaphragm) 74. As a result, the fatigue life is shortened, in other words, the durability is deteriorated, the overload tolerance range is narrowed, and the load-strain characteristics are also deteriorated, which makes it impossible to obtain a highly accurate load transducer. be.

On the other hand, if the strain-generating part is not a diaphragm as described above but a cross-shaped beam, for example, the strain-generating part has the advantage of being slightly thicker compared to the diaphragm type, and the diaphragm The stress distribution of the diaphragm type load transducer is almost the same as that of the diaphragm type load transducer, which has low strain detection efficiency and strain detection sensitivity, poor durability, narrow overload tolerance range, and load-strain characteristics. It has disadvantages such as poor performance.

(c) Purpose The present invention was devised in view of the problems existing in the prior art described above, and its purpose is to provide an ultra-low capacity that is easy to manufacture and that was previously considered impossible.

The object of the present invention is to provide a micro differential pressure transducer that is ultra-compact, inexpensive, has high differential pressure detection sensitivity and detection efficiency, has good pressure-strain characteristics, is highly accurate, and is durable.

(d) Structure In order to achieve the above-mentioned object, the present invention provides a differential pressure converter that detects the pressure difference between two systems of fluids to be measured, which are respectively introduced via two pressure introduction paths, and converts it into an electrical quantity. A casing member having a space inside and having the two pressure introduction passages each extending outward so as to communicate with the space, and a predetermined interval in the vicinity of the inner end of the pressure introduction passage within the space. and a pair of flexible sealing films such as diaphragms or bellows that are stretched so as to face each other and form a sealed chamber inside.

A pair of highly rigid support members connected to the pair of sealing films and substantially parallel to each other, and a fixed base integrally or integrally connected to the casing member facing approximately the middle of the pair of support members. a rigid connecting member that loosely passes through a hole drilled in a portion away from the center of the fixed base and connects the pair of supporting members to each other; and a thick-walled hollow having elasticity. By cutting a circumferential groove with a narrow width and a constant depth in the axial center of the cylinder, a thin cylindrical part is formed in the axial center, and each outer part of the thick cylindrical parts on both sides of this thin cylindrical part is formed. By forming a first slit along the central axis from the end to each inner end, a pair of thick circular arc plate parts are formed on both sides of the thin cylindrical part, and are further sandwiched between the first slits on both sides. A separating portion is formed by forming a second slit along the central axis extending from one end to the other end in one of the pair of thin-walled cylindrical portions of the region, and two transducer bodies each having a flat surface formed by cutting at least one outer surface along the central axis; The two transducer bodies are respectively attached to the fixed base in the sealed chamber in a state where the second thrusts are in contact with the other surface side and are deviated from each other by 180° with respect to the sensing axis orthogonal to the central axis. the thick circular arc plate portions of the two transducer bodies on the side not fixed to the fixed base are respectively in contact with the pair of support members, and the pressure introduction portions The present invention is characterized in that an electric signal corresponding to the pressure difference of the introduced fluid to be measured is obtained by a strain gauge attached to a strain-generating portion in the thin-walled cylindrical portion of the transducer main body.

First, prior to a detailed explanation of the present invention, the invention of a strain gauge type physical quantity-to-electrical quantity converter (hereinafter referred to as
Since the invention of the prior application (hereinafter referred to as the "prior invention") constitutes the main part of the invention of the present application, this invention of the prior application will be explained.

3(A) to 3(D) are all related to the above-mentioned prior invention, of which FIG. 3(A) is a front view showing the overall configuration of the bending type load converter, and FIG. 3(B) is is a side view showing the structure of the converter main body, FIG. It is.

In FIGS. 3(A) and 3(B), reference numeral 10 denotes a transducer main body having a substantially hollow cylindrical overall shape, and is formed in the following manner. That is, materials with elasticity, such as nickel-chromium steel, nickel-chromium-molybdenum steel, beryllium-copper alloy, aluminum alloy, Amber (trade name)
A thick-walled hollow cylinder is formed using a material suitable for the purpose of use. A circumferential groove 11 having a narrow width (for example, 4 m width) and a constant depth (for example, 2 cm depth) is cut on the outer periphery of the central part of this thick-walled hollow cylinder in the direction of the central axis 0-o using, for example, a lathe. . As a result, a thin cylindrical portion 12 is formed at the center in the axial direction, and thick cylindrical portions are formed on both sides of the thin cylindrical portion 12, that is, on both left and right sides in FIG. 3(B).

Next, slits 13a having a constant width (in this example, a width of 4 cm) are formed along the central axis O-0 from each outer end to each inner end of each thick-walled cylindrical portion on both sides.

13b is cut using a milling machine, for example. As a result, the thick cylindrical portions on each side form slits 13a.

13b, each pair of thick circular arc plate portions 14a are provided on both sides of the thin cylindrical portion 12.

14b, 14c, and 14d are formed.

Note that it is desirable that the inner circumferential surface of the thin cylindrical portion 12 be smoothed using a reamer or the like.

In the converter main body 10 thus formed, the thin cylindrical portion 12 in the region sandwiched between the slits 13a and 13b on both sides serves as the strain-generating portion 15.

Further, the thick circular arc plate portions 14a and 14c on both sides at an angular position deviated from the strain-generating portion 15 by 90” with respect to the central axis O serve as a load introducing portion 16, and the load introducing portion 1
Thick circular arc plate part 1 at an angular position deviated from 6 to 180°
4b and 14d are load bearing parts 17. Third
In Figures (A) to (C), examples are shown in which the load introduction part 16 is arranged at the upper part and the load bearing part 17 is arranged at the lower part.
It does not necessarily have to be used in this posture (arrangement); for example, when trying to detect a lateral (horizontal) load, it is necessary to use the
@It will be placed in a fallen position.

A strain generating portion 15 is provided on the inner circumferential side and the outer circumferential side of the strain generating portion 15.
A plurality of strain gauges SG whose sensitive axis directions are set are attached by adhesion, vapor deposition, sputtering, welding, or other appropriate means so as to be able to detect the bending strain of. Multiple sheets attached in this way (in this example, 4
A Wheatstone bridge (not shown) is formed by the strain gauges SG.

It should be noted that the inner circular arc plate portions 14a and 14c are in line contact with the load introducing portion 16.

The load seat 18 receives the load, and similarly, the load bearing part 19 disposed in the stationary part is in line contact with the load bearing part 17 in the thick circular arc plate parts 14b and 14d. be.

Although not shown in the drawings, the transducer body 10 is housed in a transducer case to prevent oxidation and a decrease in insulation resistance due to moisture absorption, particularly in the strain gauge SG, and is generally provided with a sealing means for blocking outside air. administered. In addition, in the figure, the symbol Ω
The member marked with is a gauge lead connected to the gauge tab of the strain gauge SG.

Next, the operation of the embodiment according to the prior invention constructed as described above will be explained.

When, for example, a compressive load is applied to the load introducing portion 16 of the converter body 10 via the load seat 18 in the direction of the load axis N-N, the portions of the converter body 10 other than the strain-generating portion 15 will be
Since the strain-generating portion 15 of the thin-walled cylindrical portion 12 is thicker than the strain-generating portion 15 and has sufficiently high rigidity, the strain-generating portion 15 of the thin-walled cylindrical portion 12 is elastically deformed (changes in curvature) without causing almost any strain (deformation). This causes distortion. As a result, a bending moment proportional to the applied load acts on the strain-generating portion 15 due to the compressive load, and bending stress is generated.

The bending moment Mb when the load W acts on the load introduction part 16 of the converter main body 10
If the outer diameter of 2) is d and the inner diameter is d, it is given by the following equation.

Mb = W (D+d)/8...
-(1) Therefore, the bending stress δb is given by the following equation (2).

ab =++3W (D+d)/4b-t" -・
...(2) Here, b is the width of the strain-generating portion 15, and t is,
This is the wall thickness of the strain-generating portion 15.

The bending stress distribution in the circumferential direction in the strain-generating portion 15 of the embodiment according to the invention of the prior application has a very gentle curved shape as shown in FIG. 3(D). As can be seen from this figure, the difference between the maximum bending stress εborax and the minimum εb■in is
It is very small and can be ignored in terms of the detection range of the strain gauge. Therefore, like the diaphragm type and cross beam type transducers mentioned above, the strain gauge SG
Since there is no steep change in stress in the detection range, no localized high strain occurs in the strain gauge SG, so the detected strain level is high and average strain can be detected with high sensitivity. As mentioned above, in the stress distribution of the diaphragm type and cross beam type, very high stress occurs outside the strain detection range of the strain generating part, so when considering the mechanical strength of the transducer, it is difficult to When the stress in a region is reduced, the strain level in the strain detection range is naturally reduced. On the other hand, the strain generating portion 15 in the load converter of the above embodiment
The maximum stress of is located at the center of the strain detection range of the strain generating part 15, and the strain level in the strain detection range can be considered to be approximately constant, so highly sensitive strain detection is possible.
Since the stress level in the other parts of 5 is low, it is possible to obtain a highly sensitive and accurate load transducer that is sufficiently durable even against repeated loads.

In particular, the invention of the prior application described above can reduce the size of the converter.
We will explain whether lower capacity can be achieved.

That is, in the transducer according to the prior invention, since it is only necessary to form the circumferential groove 11 and the slits 13a and 13b in the thick hollow cylinder, the hollow cylinder can be made small and the thin cylindrical part 12 forming the strain-generating part 15 can be made small. By shortening the axial length of
A small, low-capacity converter can be easily manufactured. In other words, when compared with the size of conventional diaphragm-type or cross-beam-type load converters, it can be made into a water-repellent type that can be said to be extremely small.

Furthermore, in order to reduce the load capacity, the depth of cut during machining of the circumferential groove 11 may be increased to narrow the groove width.

According to the above production procedure, it is possible to easily and inexpensively
A compact, low-capacity load transducer can be provided.

Regarding the response frequency, as mentioned above, in order to lower the capacity of the conventional diaphragm type and cross beam type, due to their structure, it is necessary to reduce the bending rigidity. Although the response frequency inevitably decreased, according to this embodiment, a load transducer with a high response frequency and low capacity can be easily obtained.

By the way, although it is possible to reduce the capacity in the prior invention that is configured and operates as described above, for example, a load transducer that can detect a load of several grams or a pressure on the order of 0.01 kg/a# It is extremely difficult or impossible to manufacture a pressure transducer (micro differential pressure transducer), which is a factor that significantly increases costs. for example,
Although the device according to the above-mentioned prior invention can be turned to have a strain-generating portion thinner (for example, about 0.1 mm) than the diaphragm type, the turning operation is not easy and requires a skilled worker. However, there is a risk of producing defective products, which is extremely disadvantageous in terms of cost. Furthermore, even if the width of the strain-generating portion 15 is reduced in order to reduce the capacitance, there is a limit in this respect because there is a restriction on the size of the strain gauge SO attached thereto.

The present invention has been made in consideration of such circumstances, and the overall configuration will be described below with reference to FIG. 1.
The structure of the converter body, which is the main part, is shown in Figure 2 (A).
, (B), (C), (D) and (E).

First, in FIG. 1, reference numeral 1 denotes a casing member having a thick-walled cylindrical overall shape, and a cylindrical space 1a is formed inside the casing member, and the sensing axis direction (in the case of this figure, the left-right direction) is a casing member. ) Pressure introduction parts 1b and lc connected to the object to be measured (for example, a pressure tank, etc.) are protrudingly provided at both ends, and a space 1a and a space 1a are provided in the center (a part that substantially coincides with the sensing axis). Pressure introduction passages 1d and 1e are formed to communicate with each other. Pressure introduction path 1d in this space lc
, le, a pair of flexible sealing films, in this example, a pair of diaphragms 2a, are arranged substantially perpendicular to the sensitive axis direction and facing each other with a predetermined interval.

2b connects its peripheral parts 2c and 2d to the space 1 of the casing 1.
(a) It is attached to the inner wall in an airtight manner, for example, by welding or the like.

In this way, in the space 1a, two diaphragms 2a
, 2b and the inner wall of the casing member 1 constitutes a sealed chamber 1f completely cut off from the outside air.

Near the inner side of the pair of diaphragms 2a and 2b,
A pair of highly rigid plate-shaped support members 3a are arranged substantially parallel to the diaphragms 2a and 2b.

3b connects to the diaphragm 2a via the connecting shafts 4a and 4b.
, 2b. These pair of supporting members 3a
, 3b are disposed, and a plate-shaped fixed base 5 integrally or integrally connected to the inner wall of the space 1a of the casing member 1 is disposed so as to cross the intermediate portion where the casing members 1 and 3b are disposed. The fixed base 5 has one through hole 5a in the center and two through holes 5b in areas away from the center. A connecting rod 6 serving as a highly rigid connecting member is loosely inserted into the two through holes 5b of the fixed base 5, and each end of the connecting rod 6 is connected to the pair of supporting members 3a.
, 3b, and the pair of supporting members 3a, 3
b are connected to each other.

As described in detail later, converter bodies 20 and 30 are fixed to both ends of the fixed base 5 by screws 29 serving as attachment members inserted into the through holes 5a. As will be described in detail later, the other parts of the transducer bodies 20 and 30 are integrally connected to the pair of support members 3a and 3b by threaded portions formed on the connecting shafts 4a and 4b while in contact with the pair of support members 3a and 3b. ing.

22, the more detailed structure of the converter bodies 20 and 30 will be explained with reference to FIGS. 2(A) to 2(E).

FIG. 2(A) is a front view showing the configuration of the bending type converter variant used in the embodiment shown in FIG. 1, and FIG. 2(B)
is also a side view, the same figure (C) is a sectional view taken along the line Q-Q with part of the same figure (B) omitted, and the same figure (D) and (E) are respectively the strain-induced strain in the same example. FIG.

In FIGS. 2(A) and 2(B), 20 and 30 have the same material and basic configuration as the converter main body 10 according to the invention of the prior application. That is, the circumferential grooves 21 and 31, and the pair of first slits 23a.

23b and 33a, 33b, two pairs of thick circular arc plate parts 24a to 24d and 34a to 34d, etc. are shown in FIG.
) and (B), the explanation thereof will be omitted, and only the members or portions that are different from the converter of the prior application will be explained. 22 and 32 are thin cylindrical parts, and the second slits 22a and 3
2a is formed and has a substantially C-shaped cross section and a substantially inverted C-shaped cross section, so strictly speaking, it should be called a thin-walled notched cylindrical portion. The second slits 22a and 32a are connected to one of the thin cylindrical portions 22 and 32 of the pair of thin cylindrical portions 22 and 32 in the area sandwiched between the first slits 23a and 33a and 23b and 33b on both sides. 32 from one end to the other end with the center axis 0. and 02, and as a result, a spaced part is formed. Therefore, the strain gauge SG is
) is attached to the inner and outer circumferential sides of the strain-generating parts 25 and 35 on the side where the separation parts (ie, the slits 22a and 32a) are not formed.

In the case of this transducer, one of the force introducing portions 16 is located at the top of the thick circular arc plate portions 24a and 24c of the upper transducer main body 20 (that is, at a 90° deviation from the strain-generating portion 25 with respect to the central axis 0. The other force introducing portion 17 is set at the thick arc plate portions 24a, 24c at the angular position, and the other force introducing portion 17 is a convex head on the lower side of the thick arc plate portions 34b, 34d of the lower transducer main body 30. Set at the top.

The other thick circular arc plate portions 24b, 24d and 34a, 34c of the converter bodies 20 and 30 are cut into planar shapes along the central axes 01 and o2, respectively, to form planar portions 24e and 34e. .

The two transducer bodies 20 and 30 have the flat portion 24a
and 34e are in contact with both sides of the fixed base 5, and the respective second slits 22a and 32a are deviated from each other by 180° with respect to the sensitive axis P-P that is perpendicular to the central axes 0□ and 0□. They are stacked on top of each other with the fixed base 5 in between, and are integrally connected by a mounting member. That is, this mounting member is assembled by inserting the countersunk screw 29 inserted into the semi-cylindrical washer 28 into the through hole bored in the thin-walled cylindrical parts 22 and 32, and screwing it into the semi-cylindrical nut 38. Two thick circular arc plate parts 24
b, 24d and 34a.

34c to the fixed base 5 integrally.

The converter main body 20 is connected to the support member 3a by screwing the male thread formed on the connecting shaft 4a into the semi-cylindrical nut 27 as described above. Further, the converter main body 30 is connected to the support member 3b by screwing a male screw formed on the connecting shaft 4b into a semi-cylindrical nut 37.

Next, the operation of the embodiment configured as described above will be explained.

A first fluid to be measured and a second fluid to be measured are introduced from the pressure introduction paths in the left and right directions in FIG.

When two systems of measured pressures P2 and P2 are applied to the diaphragms 2a and 2b as shown by the arrows, the respective diaphragms 2a and 2b respond to the measured pressure P
Due to the pressure difference between □ and P2, it bends so as to bulge from the high pressure side to the low pressure side, and stabilizes at a position where the pressure is balanced.

Then, the connecting shaft 4a is connected to the diaphragms 2a and 2b.
and support members 3a and 3b connected via 4b.
The supporting members 3a and 3b move (displace) together with the connecting rod 6 from the high pressure side to the low pressure side.
displacement), the strain-generating portions 25 of the converter bodies 20 and 30
and 30 are bent, and the strain gauges SG attached to both sides thereof also expand or contract. A Wheatstone bridge circuit is constructed with these plurality of strain gauges.
From the bridge output end, the first. An electrical signal corresponding to the pressure difference (Ipl-pI) of the second measurement fluid is obtained.

Here, regarding the action of the converter bodies 20 and 30, the second
This will be explained in more detail with reference to Figures (A) to (E).

The sensing axis P- is connected to the force introducing portions 16 and 17 of the upper transducer bodies 20 and 30 via the supporting members 3a and 3b.
When a force is applied in the P direction, for example, in a direction in which they approach each other, the parts of the transducer bodies 20 and 30 other than the strain-generating parts 25 and 35 become thicker than the strain-generating parts 25 and 35. Since the rigidity is set high, the thin-walled cylindrical portions 22 and 32 can be formed with almost no distortion (deformation).
The strain-generating parts 25 and 35 are elastically deformed (curvature changes) and strain is generated. As a result, a bending moment proportional to the acting force acts on the strain-generating portions 25 and 35 due to the force in the compression direction, and bending stress is generated.

In particular, in this embodiment, the thin cylindrical portions 22 and 32 are cut out at each location by the second slits 22a and 32a, so that the strain-generating portion 25
A large bending moment acts on and 35, generating bending stress.

Incidentally, using the same symbols (DI dt b, t, W) as shown in FIGS. 3(B) and (C), the bending moment Mb'' and bending stress ab' of the converter of this embodiment are as follows.
It is given by the following equations (3) and (4).

Mb' = W (D+d)/4 (3)
ab'=3W(D+d)/2b-t" (4) Comparing the above equations (1) and (3), and the above equations (2) and (4), the converter of this embodiment has twice the output sensitivity as the converter of the prior invention even with the same dimensions (outer diameter D, inner diameter d, width, wall thickness t).In other words,
If the output sensitivity is the same, for example, the strain generating parts 25 and 3
5 can be made thicker, turning becomes easier, and the manufacturing cost can be significantly reduced.

In the above embodiment, since the second slits 22a and 32a are respectively formed, each transducer body 20 and 30 individually displaces unbalancedly.
As shown in FIG. 2(A), both are relative to the sensitive axis P.
The supporting members 3a are arranged 180° opposite each other and are integrated.

3b when a compressive force (the same applies to tensile force) in the direction of the sensitive axis P is applied, the force introduction parts 16 and 17 move along the sensitive axis P-P.
Move along the line. Therefore, the second slit 22a
, 32a has no adverse effect on the accuracy of differential pressure measurement.

It has all the advantages of the converter of the prior application shown in FIG. 3 mentioned above.

In addition, in the differential pressure converter of the above embodiment, the sealed chamber lf
Even if air bubbles are mixed in the pressure transmitting fluid filled inside, there is an advantage that the measurement value is not affected by expansion and contraction due to temperature changes.

That is, for example, if we consider the case where the temperature rises and the pressure transmitting fluid expands, the diaphragms 2a and 2b
each tries to deform so as to bulge outward, but the center portions of both become rigid through the connecting shaft 4a, the supporting member 3a, the connecting rod 6, the supporting member 3b, and the connecting shaft 4b in this order. Since both the supporting members 3a are connected to each other at.

The interval between 3b can be considered to be unchanged. In the unlikely event that the connecting rod 6 is extended and the supporting members 3a and 3b
are slightly displaced away from each other, the strain-generating parts 25 and 35 of the transducer bodies 20 and 30 are deformed so that their radius of curvature increases. However, due to the strain gauges SG attached to each of the strain generating parts 25 and 35,
By assembling a suitable Wheatstone bridge, both transducer bodies 20 and 30 can electrically cancel each other out when they are pulled together as during expansion (same as when compressed together as during deflation). while one transducer body (e.g. 20) is tensioned and the other transducer body (e.g. 30) is
When is compressed, the displacement of supporting members 3a and 3b (
An electrical signal corresponding to the movement (movement) can be extracted from the output end of the Wheatstone bridge.

Incidentally, as a way of assembling a Wheatstone bridge with such a function, for example, strain gauges attached to the outer periphery of the strain generating part 25 and the inner periphery of the strain generating part 35 are connected to opposite sides of the bridge, and the strain gauges are attached to the opposite sides of the bridge. Strain gauges attached to the inner circumference of the strain section 25 and the outer circumference of the strain generating section 35 may be respectively connected to the other opposite side adjacent to the opposite side.

Note that the present invention is not limited to the embodiments described above and shown in the drawings, but can be implemented with various modifications without departing from the gist thereof.

For example, in the above embodiment, the diaphragms 2a and 2b are used as means for receiving the fluid to be measured and converting it into force.
Although an example using a bellows is shown, this may be replaced with a bellows, or a diaphragm and a bellows may be used together.

Furthermore, although the casing member 1 is shown as one member,
Depending on manufacturing convenience, cost considerations, etc., parts are manufactured in divided formats as appropriate, and finally welded (for example, TI
They may be closely connected by G welding, electron beam welding, etc.).

In addition, in the embodiment, the strain gauge has a strain generating part 15.
Although an example has been described in which the strain-generating parts 15 and 35 are attached to both the outer circumferential surface and the inner circumferential surface, they may be attached only to the inner circumferential surfaces or only to the outer circumferential surfaces of the strain-generating parts 15 and 35.

Further, although the case where the sealed chamber lf is filled with an incompressible fluid is shown, if the pressure resistance is low, the fluid may not be filled.

(e) Effects As detailed above, according to the present invention, it is possible to achieve ultra-low capacity, ultra-miniaturization, low cost, and mass production, which were previously considered impossible, and to improve differential pressure detection sensitivity and detection efficiency. is extremely high, and the strain characteristics of the strain-generating part are good.In particular, even if air bubbles are mixed in the space, it is not affected by temperature unlike conventional examples, temperature compensation is easy, and it is durable. , it is possible to provide a minute differential pressure transducer that can detect minute pressure differences with high precision.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the overall configuration of an embodiment of a micro differential pressure transducer according to the present invention, and FIGS. 2 (A) to (E) are all according to the present invention. Figure 2 (A) is a front view showing in detail the main part of the converter body in the same embodiment, Figure 2 (B) is a side view thereof, and Figure 2 (C) is the same figure (
A sectional view of B) in the direction of the Q-Q line, (D) and (E
) are stress distribution diagrams of the strain-generating part in the same example, and
3(A) to 3(D) are all related to the invention of the earlier application, and among these, FIG. 3(A) is a front view showing the overall configuration of one embodiment of the bending type load converter; (B) is a side view showing the configuration of the main body of the converter, which is the main part of the prior invention, and (C) is the same figure.
is a sectional view in the Y-Y line arrow direction of the same figure (B), the same figure (D)
is a stress distribution diagram of the strain-generating part on the same side, FIG. 4 is a sectional view showing an example of a conventional differential pressure transducer, and FIGS. 5 (A) and (B) are a diagram of a conventional diaphragm type load transducer. A plan view showing the configuration of the main parts, a sectional view taken along the line x--X in FIG. 1...Casing member, 1a...
・Space, lb, lc...pressure introduction part. ld, le...pressure introduction path, 1f...
- Sealed chamber, 2a, 2b...Diaphragm, 3a, 3b
...Supporting member, 4a, 4b...Connection shaft. 5... Fixed base, 5a, 5b... Through hole. 6...Connection rod, 16.17...Force sensing input part. 20.30...Converter main body, 21.31... Circumferential groove, 22.32... Thin cylindrical portion, 22a, 32a... Second slit. 23a, 23b, 33a, 33b ---first slit, 24a to 24d, 34a to 34d ---Thick circular arc plate portion. 24e, 34a...Flat portion. 25.35...Strain part. 27.37.38...Semi-cylindrical nut. 29...screw, SG...strain gauge.

Claims (1)

[Claims] (1) Two pressures are introduced through two pressure introduction paths, respectively.
A differential pressure converter that detects a pressure difference in a fluid to be measured in a system and converts it into an electrical quantity, which has a space inside and the two pressure introduction paths each extending outward so as to communicate with the space. A casing member and a pair of flexible diaphragms or bellows, each of which is stretched so as to face each other at a predetermined distance near the inner end of the pressure introduction path in the space and form a sealed chamber therein. A sealing film, a pair of highly rigid support members connected to the pair of sealing films and substantially parallel to each other, and connected integrally or integrally with the casing member facing approximately the middle of the pair of support members. a fixed base, a highly rigid connecting member that loosely passes through a hole drilled in a portion away from the center of the fixed base, and connects the pair of supporting members to each other; A thin-walled cylindrical portion is formed in the axially central portion by cutting a circumferential groove with a narrow width and a constant depth in the axially central portion of the thick-walled hollow cylinder, and thick-walled cylinders are formed on both sides of this thin-walled cylindrical portion. A pair of thick circular arc plate parts are formed on both sides of the thin cylindrical part by forming first slits extending along the central axis from each outer end to each inner end of the part, and first slits on both sides are formed. A spacing part is formed by forming a second slit along the central axis extending from one end to the other end in one of the pair of thin-walled cylindrical parts in the area sandwiched between the thick-walled cylindrical parts, and two transducer bodies each having a plane part formed by cutting the outer surface of at least one of the arcuate plate parts along the central axis, and the plane part of each of these two transducer bodies being attached to the fixed base The two transducer bodies are placed in the sealed chamber with the second slits in contact with one side and the other side and shifted by 180 degrees from each other about the sensing axis perpendicular to the central axis. mounting members respectively fixed to the fixed base, the thick circular arc plate portions of the two converter main bodies on the side not fixed to the fixed base are respectively abutted with the pair of supporting members, and the two The transducer is characterized in that an electric signal corresponding to the pressure difference of the fluid to be measured introduced from the pressure introduction part is obtained by a strain gauge attached to the strain-generating part in the thin-walled cylindrical part of the transducer main body. Micro differential pressure transducer.