WO2002014820A1 - Pressure sensor - Google Patents

Abstract

A pressure sensor capable of increasing a detection accuracy by preventing the adverse effect of a diaphragm on a detection part, wherein the diaphragm (2) forms a clearance between an outer ring part (23) as the outer peripheral end part of the detection part (22) and a case (3), maintains the detection part (22) and the case (3) in the state of not coming in contact with each other, allows the detection part (22) to be deformed radially by thermal expansion, and prevents the deformation of the case (3) from affecting the detection part (22).

Description

 Description Pressure sensor Technical field

 The present invention relates to a pressure sensor for detecting a pressure of a fluid or the like. Background art

 Conventionally, this type of pressure sensor has been used in, for example, a chemical factory or a food factory for a device for a storage where the detection target is a fluid such as a drug or food (milk, beer, etc.). Prior art pressure sensors are

FIG. 10 is a schematic sectional view of FIG.

 In FIG. 10, the pressure sensor 101 generally has a structure including a diaphragm 102 as a pressure-sensitive portion that directly receives a fluid pressure, and a metal case 103.

 The case 103 includes a cylindrical part 13 1 having an opening covered by a diaphragm 102, and an outward flange 13 2 provided at an R-side end of the cylindrical part 13 1 on the mounting opening side. ing.

 Flange 13 2 is for connecting with flange 14 1 of mounting port 10 4 and clamp 10 5, and the outer circumference of flange 13 2 is the same as flange 14 1 of mounting port 10 4 Diameter. Further, a packing 106 for preventing leakage is arranged between the two flanges 13 2 and 14 1 connected by the clamp 105.

Diaphragm 102 has a thick central portion 121 and a detecting portion 122 having a lower thickness than the central portion 121 around the central portion 121. And a disk shape having: Diaphragm 1 0 2 has an outer peripheral end integrally formed with an annular projection 1 33 protruding inward from the cylindrical portion 1 3 1 of the case 103, and is fixed to the cylindrical portion 1 3 1 of the case 103. .

 On the inner surface (upper side in the figure) of the cylindrical part 13 1 of the detecting part 122, a strain gauge 108 that converts the deformation of the detecting part 122 to an electric signal due to the pressure of the fluid 107 is directly provided on the surface. is set up. That is, the deformation of the detection unit 122 caused by the fluid pressure directly deforms the strain gauge 108 provided on the surface of the detection unit 122.

 In the pressure sensor 101 having the above configuration, the strain gauge 108 is deformed as the detecting portion 122 of the diaphragm 102 is deformed by the fluid pressure, and the resistance of the deformed strain gauge 108 is changed. Changes in values are extracted as electrical signals and output to the outside.

 The pressure sensor 101 of the prior art as described above detects a fluid 107 such as a medicine or food (milk, beer, etc.). For example, the fluid 107 decays and bacteria grow. Use conditions in which low-temperature fluid and high-temperature fluid alternately flow, such as washing with sterilization using a heating fluid such as high-temperature steam at 150 ° C or disinfection using a low-temperature fluid such as alcohol at 0 ° C to prevent It was used for.

 However, in the case of the pressure sensor 101 of the prior art, the zero point greatly fluctuates under the above-mentioned operating conditions in which the low-temperature fluid and the high-temperature fluid alternately flow, which deteriorates the detection accuracy. There was a problem.

 For example, when fluid 107 at 0 ° C and 150 ° C flows alternately and repeatedly, every time the flowing fluid 107 changes, the pressure sensor 101 changes output from% to several tens% every time. In such a case, it could not be actually used. .

This is due to the heat of the detector 102 and the case 103 of the diaphragm 102. If there is a difference in capacity and the fluid temperature changes rapidly, the detection unit 122 with a small heat capacity approaches the fluid temperature in a short time, whereas the case 103 with a large heat capacity will loosen This is because the temperature approaches the fluid temperature significantly, and the difference in radial expansion between the detection unit 122 and the case 103 in the radial direction increases, and a stress that causes the detection unit 122 to permanently deform is generated.

 For example, when the fluid at 0 ° C is changed to a fluid at 107 ° C at a temperature of 150 ° C, the detection unit 122 with a small heat capacity tries to expand in the outer diameter direction in a short time. On the other hand, the case 103, which has a large heat capacity, expands slowly, so that the detection part 122 is prevented from expanding in the radial direction by the case 103, as shown in Fig. 11. However, due to the stress caused by expansion, the detection unit 122 expands by distorting itself in a direction other than the outer diameter direction, and is permanently deformed. Since the permanent deformation of the detector 122 directly deforms the strain gauge 108, the output changes and the zero point also fluctuates.

 When such permanent deformation of the detection unit 122 is repeated, the diaphragm 102 may eventually be damaged.

 In addition, the pressure sensor 101 is connected to the mounting port 104 in order to keep the fluid receiving surface such as the pressure receiving surface of the diaphragm 102 clean so as not to contaminate the fluid 107 due to propagation of various bacteria. It needs to be removed and cleaned periodically, and is removably connected to the mounting opening 104 with the clamp 105.

However, if the clamp 105 is a ferrule-type clamp 122, as shown in Fig. 12, which is fastened by an operator, the fastening force of the worker will not always be constant, so the fastening force will not be constant. Is too strong, case 103 is overtightened, and as shown in Fig. 11, the deformation of case 103 due to the tightening distorts the detection section 122 of diaphragm 102, causing a few percent An output change of several tens of percent occurred, causing the zero point to fluctuate. For this reason, it was necessary to adjust the zero point each time the pressure sensor 101 was mounted by fastening with the clamp 105. Further, even when the zero point is adjusted, the packing 106 is cleaved during use, and the amount of distortion of the detection unit 122 changes with time, so that the detection accuracy may deteriorate.

 SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a pressure sensor which prevents an adverse effect on a detection unit of a diaphragm and improves detection accuracy. . Disclosure of the invention

 The present invention

 A pressure sensor including a diaphragm having a detection unit that receives a fluid pressure,

 The diaphragm allows the detection unit to be deformed by thermal expansion, and keeps the detection unit and the housing in a non-contact state so that deformation of a housing to which the diaphragm is attached does not affect the detection unit. And a deformation absorbing portion for absorbing deformation caused by thermal expansion of the detection portion or deformation of the housing between the detection portion and a fixed position of the diaphragm fixed to the housing. Features.

Therefore, when the detector is deformed due to thermal expansion, by keeping the detector and the housing in a non-contact state, even if there is a difference in heat capacity between the detector and the housing, deformation due to thermal expansion of the detector is prevented. Since the sensor is allowed, even when the fluid temperature changes suddenly, permanent deformation of the detection unit caused by the thermal expansion of the detection unit being hindered by the housing can be suppressed, and the detection accuracy can be improved. Therefore, it is possible to prevent the final diaphragm from being damaged due to repeated permanent deformation of the detection unit.On the other hand, the deformation absorption unit deforms and absorbs the deformation due to the thermal expansion of the detection unit. Therefore, no stress is generated between the deformation absorbing portion and the housing due to the deformation of the deformation absorbing portion.

 Also, when the housing is deformed, by keeping the detection unit and the housing in a non-contact state, the deformation of the housing does not affect the detection unit. Fluctuations can be suppressed. On the other hand, although the deformation of the housing is transmitted to the deformation absorbing portion, the deformation absorbing portion deforms and absorbs the deformation of the housing, so that stress due to the deformation of the deformation absorbing portion may be generated between the deformation absorbing portion and the detecting portion. Absent.

 It is preferable that the deformation absorbing portion is positioned such that the fixed position is different from the same pressure direction as the pressure receiving surface of the detection portion.

 Accordingly, the deformation due to thermal expansion of the detection unit is not hindered in the same plane direction as the pressure receiving surface of the detection unit, and the deformation of the housing does not affect the detection unit.

 It is preferable that a protection portion for preventing the deformation of the deformation absorbing portion from being transmitted to the detection portion is provided at an end of the detection portion connected to the deformation absorbing portion.

 This can prevent the deformation of the deformation absorbing section from being transmitted to the detection section by the protection section, and can prevent the detection accuracy from deteriorating.

 Assuming that the thickness of the detection unit is t0, the thickness of the deformation absorbing unit is t1, and the length of the deformation region of the deformation absorbing unit is L,

 t 1 <1.5 X t O, force, L> 2 X t 0

It is preferable to satisfy the following condition.

As a result, for example, when the fluid at 0 ° C and 150 ° C alternately flows, the fluctuation of the zero point due to the output change every time the flowing fluid changes can be suppressed within 3%, and the detection accuracy can be improved. Can be planned. When the cross-sectional area of the protection part is A, Aku l OOX t OX t O

It is preferable to satisfy the following condition.

 This prevents the deformation of the deformation absorption part from being transmitted to the detection part and prevents the protection part from obstructing the thermal expansion of the detection part due to the heat capacity of the protection part becoming too large. Can be prevented.

The deformation absorbing portion is a thin portion between two grooves formed adjacent to each other from both the front surface and the back surface in contact with the fluid ₍ therefore, production of a diaphragm having a thin portion is It is only necessary to machine two grooves in a state where it is integrated with the housing.Since machining can be performed simultaneously with the housing, there is no need for welding and finishing processes for joining the diaphragm to the housing, reducing the number of processes and facilitating production. In addition, the depth of the groove on the diaphragm surface is shallow, making it difficult for debris to stay in the groove, making it suitable for handling foodstuffs as a saori.

 It is preferable that the thin portion is provided between a first groove on the outer periphery of a front surface and a second groove on an inner diameter side of the first groove on the back surface. 'Thereby, a thin portion can be formed by simple processing.

 If the diameter of the detection unit is a,

 It is preferable that the thickness between the grooves is set to 2Za or more and 20 / a or less, and the length between the grooves is set to 6 / a or more and 60 / a or less to form the thin portion. ·

 Thereby, the thin portion absorbs the deformation due to the thermal expansion of the detecting portion or the deformation of the housing, so that the detection accuracy can be improved.

 If the diameter of the detection unit is a,

 It is preferable that the depth of the surface of the detection unit, which is in contact with the fluid, depressed from a reference position is set to 10 to 60 a.

 Thereby, the detection accuracy can be improved more favorably.

Equipped with an annular member that is fastened and fastened with a fastening member ,

 It is preferable that the housing to which the diaphragm is fixed is fixed to the annular member by screws.

 As a result, since the housing is not directly clamped and fixed by the fastening member, the deformation of the housing is suppressed low, and the deformation absorbing portion deforms and absorbs the deformation of the housing, so that there is no space between the deformation absorbing portion and the detecting portion. No stress is generated due to the deformation of the deformation absorbing portion.

 An annular member that is fixed to the mounting opening by being fastened with a fastening member,

 It is preferable that a flange is formed in a housing to which the diaphragm is fixed, and the flange is also fixed by being clamped together with the annular member by the fastening member.

 As a result, only the flange portion of the housing is directly clamped and fixed by the fastening member, so that the deformation of the housing is suppressed to a low level, and the deformation of the housing is absorbed by the deformation absorbing portion. No stress is generated between the sensor and the detector due to the deformation of the deformation absorber. BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1 is a sectional view showing a pressure sensor according to a first embodiment,

 FIG. 2 is a half sectional view showing a diaphragm according to the first embodiment,

 FIG. 3 is a half sectional view showing another example of the diaphragm according to the first embodiment,

FIG. 4 is a half sectional view showing another example of the diaphragm according to the first embodiment, FIG. 5 is a half sectional view showing a pressure sensor and a diaphragm according to a second embodiment,

 FIG. 6 is a graph showing a measurement result of an output change in a set range of the pressure sensor according to the second embodiment,

 FIG. 7 is a diagram showing the verification results of the present invention.

 FIG. 8 is a cross-sectional view showing a pressure sensor of a comparative example when a bag nut method is used.

 FIG. 9 is a sectional view showing a pressure sensor according to the third embodiment,

 FIG. 10 is a cross-sectional view showing a conventional pressure sensor, and FIG. 11 is a half cross-sectional view showing a state in which a diaphragm of the prior art has failed.

 FIG. 12 is a perspective view showing a ferrule-type clamp. BEST MODE FOR CARRYING OUT THE INVENTION

 (First Embodiment)

 Hereinafter, the first embodiment will be described with reference to FIGS. 1 to 4 and 12. FIG. 1 is a sectional view showing a pressure sensor according to the first embodiment. FIG. 2 is a half sectional view showing the diaphragm according to the first embodiment. FIGS. 3 and 4 are half sectional views showing another example of the diaphragm according to the first embodiment.

 The pressure sensor 1 is used in a sanitary device for detecting a fluid such as a drug or food (milk, beer, etc.) in a drug factory or a food factory, for example, as in the conventional technology.

In FIG. 1, the pressure sensor 1 has a general configuration including a diaphragm 2 as a pressure-sensitive portion that directly receives a fluid pressure, and a metal case 3 as a housing. The case 3 includes a cylindrical portion 31 whose opening is covered by the diaphragm 2, and an outward flange 32 provided at the R-side end of the cylindrical portion 31 on the mounting opening side.

 The flange 32 is for connecting with the flange 41 of the mounting port 4 by the clamp 5, and the outer circumference of the flange 32 is the same diameter as the flange 41 of the mounting port 4. Then, the two flanges 32 and 41 are fastened by the clamp 5. As the clamp 5, as shown in FIG. 12, a rule-type clamp or the like is used for fastening by an operator.

 A packing 6 for preventing leakage is arranged between the two flanges 32 and 41 connected by the clamp 5.

 The diaphragm 2 has a thick central part 21, a detecting part 22 having a thinner thickness than the central part 21 around the central part 21, and a detecting part 22 having a pressure receiving surface on the lower surface shown in the drawing, and a detecting part. 22 The outer ring 23 as a protective part provided with a thicker outer peripheral end and the outward flange 24 a at the R end on the mounting port side are attached from the outer ring 23 And a cylindrical portion 24 as a thin deformation absorbing portion extending to the mouth side R.

 In the diaphragm 2, a gap is formed between the outer ring part 23, which is the outer peripheral end of the detection part 22, and the case 3, and the detection part 22 and the case 3 are maintained in a non-contact state. The deformation in the radial direction due to the thermal expansion of the case 22 is allowed, and the deformation of the case 3 does not affect the detection unit 22.

 The detecting unit 22 is deformed by receiving a fluid pressure on a pressure receiving surface on the lower surface in the figure in contact with the fluid 7.

The outer ring 23 prevents the deformation of the cylindrical portion 24 from being transmitted to the detecting portion 22 as a protective portion, and the deformation of the cylindrical portion 24 is transmitted to the detecting portion 22 to detect the deformed portion 22. the _c cylindrical portion 2 4 but prevents' the deformation to cause detection accuracy is deteriorated, varying deformation or casing 3 due to thermal expansion of the detection unit 2 2 It absorbs the shape and prevents either deformation of the detector 22 or the case 3 from affecting the other. That is, it is possible to prevent deformation of the detection unit 22 due to thermal expansion from being hindered by the case 3, and prevent deformation of the case 3 from deforming the detection unit 22.

 Further, the cylindrical portion 24 extends in a direction perpendicular to the pressure receiving surface of the detecting portion 22, and the fixing position where the outer periphery of the flange 24 a of the cylindrical portion 24 is fixed to the case 3 is determined by the pressure receiving portion of the detecting portion 22. It should be positioned inside the cylindrical part 31 of the case 3 so as to be different from the same plane direction as the surface, and support the detecting part 22 while forming a gap between the outer ring part 23 and the case 3. Is possible.

 That is, the detecting section 22 is recessed inside the cylindrical section 31 of the case 3. For this reason, when the pressure sensor 1 is detached from itself, it is possible to avoid applying an impact to the detection unit 22 due to cleaning or the like, and the handling is easy.

 Then, as shown in the enlarged view of FIG. 2 (a), the diaphragm 2 has a thickness of the detecting section 22 of t O, a thickness of the cylindrical section 24 of tl, and a heat of the detecting section 22. Assuming that the length of the cylindrical portion that is the deformation region length of the cylindrical portion 24 that absorbs the deformation due to expansion or the deformation of the case 3 is L, the conditions of tl <l.5Xt0 and L> 2Xt0 are satisfied. Meets

 Also, the cross-sectional area A of the outer ring part 23 satisfies the condition of A <100 Xt O Xt O.

 The diaphragm 2 is fixed to the cylindrical part 31 of the case 3 by beam welding the outer peripheral end of the outward flange 24 a to the inner end of the cylindrical part 24 by an electron beam, a laser, or the like. I have.

A strain gage 8 that converts deformation of the detection unit 22 due to the pressure of the fluid pressure into an electric signal is directly installed on the inner surface (upper side in the figure) of the cylindrical portion 3 1 of the case 3 of the detection unit 22. . That is, the detection unit 22 The deformation is such that the strain gauge 8 installed on the surface of the detection unit 22 is directly deformed by the deformation.

 In the pressure sensor 1 having the above-described configuration, the strain gauge 8 is also deformed as the detecting portion 22 of the diaphragm 2 is deformed by the fluid pressure, and a change in the resistance value of the deformed strain gauge 8 is taken out as an electric signal, and is sent to the outside Output.

 In the pressure sensor 1 according to the present embodiment, as in the conventional technology, the detection target is a fluid 7 such as a medicine or food (milk, beer, etc.). For example, the fluid 7 rots and bacteria grow. Low temperature fluid and high temperature fluid alternately flow, such as washing with sterilization using a heating fluid such as high-temperature steam at 150 ° C or disinfection using a low-temperature fluid such as alcohol at 0 ° C. It is used for use conditions.

 If the fluid temperature changes rapidly under the above-mentioned operating conditions in which the low-temperature fluid and the high-temperature fluid alternately flow, there is a small difference in the heat capacity between the detection unit 22 of the diaphragm 2 and the case 3 and the heat capacity. While the temperature of the detection unit 22 approaches the fluid temperature in a short time, the case 3 having a large heat capacity slowly approaches the fluid temperature, so that the linear expansion difference between the detection unit 22 and the case 3 increases.

 However, in the pressure sensor 1 of the present embodiment, as shown in FIG. 2 (b), the cylindrical portion 24 of the diaphragm 2 is interposed between the detecting portion 22 and the case 3, and the outer ring portion 23 is formed. Since a gap is formed between the case 3 and the detection unit 22 and the case 3 is maintained in a non-contact state, radial deformation due to thermal expansion of the detection unit 22 is allowed, and the It is possible to prevent the thermal expansion of the detection unit 22 from being hindered by the case 3 due to the difference in linear expansion, thereby suppressing generation of stress.

On the other hand, since the cylindrical portion 24 deforms and absorbs the radial deformation due to the thermal expansion of the detecting portion 22, the cylindrical portion 24 is moved between the cylindrical portion 24 and the case 3. There is no generation of stress due to deformation.

 Therefore, even when the fluid temperature changes suddenly, permanent deformation of the detector 22 caused by the thermal expansion of the detector 22 being hindered by the case 3 can be suppressed, and the detection accuracy can be improved. Therefore, it is possible to prevent the diaphragm 2 from being finally damaged due to the permanent deformation of the detection unit 22 being repeated.

For example, when the fluid at 0 ° C changes to a fluid at 150 ° C, the detection unit 22 with small heat capacity expands in the outer diameter direction in a short time, and the case 3 with large heat capacity expands slowly. I do. At this time, the detecting section 22 can linearly expand in the outer radial direction, the radial deformation due to the thermal expansion of the detecting section 22 is not hindered, and the detecting section 22 has a flat state without distortion except in the radial direction. since this _c can be maintained, strain gauge 8 is also not deformed, it is possible to suppress the variation of the output variation.

 This effect becomes more effective when the diaphragm 2 satisfies the conditions of tl <1.5 XtO and L> 2XtO, as in the present embodiment. When the fluid 7 at 150 ° C flows repeatedly and alternately, the fluctuation of the zero point due to the output change every time the flowing fluid 7 changes can be suppressed within 3%.

 Further, as in the present embodiment, when the diaphragm 2 satisfies the condition of A × 100 × T0 × T0, the heat capacity of the outer ring portion 23 becomes too large, and the outer ring portion 23 becomes outside the detection portion 22. The difference in the linear thermal expansion in the radial direction of the ring portion 23 increases, causing a stress that permanently deforms the detecting portion 22, and the outer ring portion 23 hinders the thermal expansion of the detecting portion 22. Can be prevented. However, the cross-sectional area A of the outer ring portion 23 needs to be thick enough to prevent the deformation of the cylindrical portion 24 from being transmitted to the detection portion 22.

In addition, the pressure sensor 1 keeps the fluid contact surface such as the pressure receiving surface of the diaphragm 2 clean so as not to contaminate the fluid 7 due to propagation of various bacteria. For this purpose, it is necessary to remove it from the mounting port 4 and periodically clean it.

 As shown in Fig. 12, when the clamp 5 is a ferrule type clamp 121, etc., which is fastened by an operator, the fastening force of the worker is not always constant when the pressure sensor 1 is attached. However, if the fastening force is too strong, case 3 may be overtightened.

 At this time, in the pressure sensor 1 of the present embodiment, as shown in FIG. 2 (c), a gap is formed between the outer ring portion 23 and the case 3, and the detecting portion 22 and the case 3 are connected. Since the case 3 is maintained in a non-contact state, the deformation of the case 3 due to the tightening does not affect the detection unit 22, the detection unit 22 is maintained in a substantially constant shape, and the fluctuation of the output change can be suppressed within 3%.

 —While the deformation of Case 3 due to the tightening is transmitted to the cylindrical portion 24, the deformation of the Case 3 is deformed and absorbed by the cylindrical portion 24, so the cylindrical portion between the cylindrical portion 24 and the detecting portion 22 is No stress is generated by the deformation of 24.

 For this reason, it is not necessary to adjust the zero point each time the pressure sensor 1 is mounted by fastening with the clamp 5.

 Hereinafter, other embodiments of the diaphragm 2 according to the present embodiment will be described.

 Fig. 3 (a) shows the corner of the bent corner of the flange 24a of the cylindrical portion 24. FIGS. 3 (b) and 3 (c) show the case where the angle obtained by bending the flange 24a of the cylindrical portion 24 is R.

 In the diaphragm 2 shown in FIG. 3 described above, it is possible to prevent the corner of the cylindrical portion 24 from which the flange 24 a is bent from being damaged during cleaning or the like, thereby preventing the cylindrical portion 24 from being deformed.

FIG. 4 (a) shows the central part 21 and the detecting part 22 having the same thickness. Diaphragm 2 in Fig. 4 (a) is particularly suitable for high fluid pressure. Used when

 FIG. 4 (b) shows the cylindrical portion 24 having a tapered shape. As shown in FIG. 4 (), the cylindrical portion 24 may have any shape as long as it exhibits a deformation absorbing effect.

 FIGS. 4 (c) and (d) show a shape in which the detecting portion 22 protrudes toward the mounting port side R. FIG. In FIGS. 4 (c) and 4 (d), since the case 3 does not exist on the outer diameter side of the outer ring portion 23, it can be used when the detection portion 22 is greatly deformed due to thermal expansion. Further, it is not necessary to provide the flange 2.4a in the cylindrical portion 24. Further, FIG. 4 (d) shows that even with such a shape, the detecting portion 22 is recessed inside the cylindrical portion 31 of the case 3 to protect the detecting portion 22 and is easy to handle.

 (Second embodiment)

 The second embodiment will be described with reference to FIGS. FIG. 5 is a half sectional view showing a pressure sensor and a diaphragm according to a second embodiment. FIG. 6 is a graph showing a measurement result of an output change in a setting range of the pressure sensor according to the second embodiment.

 In the pressure sensor according to the first embodiment, the diaphragm and the case are separately processed, and then the diaphragm is joined to the flange of the case. Was hanging. Further, the groove formed by the cylindrical portion of the surface of the pressure sensor according to the first embodiment that comes into contact with the fluid of the diaphragm is deep, and garbage is easily accumulated when handling food for sanitary use. It is. Therefore, in the present embodiment, the diaphragm and the case are configured to be integrally processed, and the groove formed on the surface of the diaphragm is made shallow so that dust does not easily stay when handling food for sanitary use. .

Note that the description of the present embodiment is the same as that of the first embodiment. The same members are denoted by the same reference numerals and description thereof will be omitted.

 In FIG. 5 (a), the pressure sensor 1 'is composed of a diaphragm 2, a case 3, and a body as in the first embodiment. The case 3 includes a cylindrical portion 31 whose opening is covered by the diaphragm 2, and an outward flange 32 provided at the R-side end of the cylindrical portion 31 on the mounting opening side.

 The diaphragm 2 has a thick central portion 21, a detecting portion 22 having a thickness smaller than the central portion 21 around the central portion 21, and a detecting portion 22 having a pressure receiving surface on the lower surface in the drawing for receiving fluid pressure. 22 An inner cylindrical portion 25 with an increased thickness toward the mounting port R at the outer peripheral end of the inner cylindrical portion 25, an annular portion 26 extending in the outer diameter direction from the mounting port side R end of the inner cylindrical portion 25, and a circle An outer cylindrical portion 27 as a thin portion which is a thin deformation absorbing portion connecting the outer peripheral end portion of the ring portion 26 and the case 3 to each other.

 On both sides of the inner and outer diameters of the outer cylindrical portion 27 of the diaphragm 2, first and second grooves 9 and 10 are dug so as to be adjacent and alternate with each other. An outer cylindrical portion 27 is provided as a thin portion between the groove side surfaces sandwiched between the grooves.

 The first groove 9 is formed in an annular shape so as to surround the diaphragm 2 on the surface of the case 3 that receives the fluid. The depth of the first groove is formed to be shallow so that dust does not easily stay when the pressure sensor 1 ′ handles food for sanitary use. For this reason, when the pressure sensor 1 ′ is detached alone, cleaning can be performed more easily.

The second groove 10 is formed in an annular shape on the back surface of the diaphragm 2 on the inner diameter side of the first groove 9 on the side opposite to the mounting opening side R of the diaphragm 2. In the second groove 10, the inner wall surface of the cylindrical portion 31 is used as a groove side surface on the outer diameter side as it is, the inner cylindrical portion 25 is used as the groove side surface on the inner diameter side, and the annular portion 26 is grooved on the upper surface in the drawing. It is formed to be a bottom surface. Since the first and second grooves 9 and 10 are formed by machining such as cutting in a state where the diaphragm 2 and the case 3 are integrated, the machining with the case 3 can be performed simultaneously. There is no need for the welding and finishing steps for joining in step 3, which reduces the number of steps and facilitates manufacturing. The diaphragm 2 forms a gap between the outer peripheral surface of the inner cylindrical portion 25 on the outer diameter side of the detecting portion 22 and the case 3 by the second groove 10, and the detecting portion 22 and the case 3 are in a non-contact state. , And radial deformation due to thermal expansion of the detection unit 22 is allowed, and the deformation of the case 3 does not affect the detection unit 22.

 At least one of the inner cylindrical portion 25 and the annular portion 26 serves as a protection portion to prevent the deformation of the outer cylindrical portion 27 from being transmitted to the detecting portion 22, and to prevent the outer cylindrical portion 27 from being deformed. The deformation is prevented from being transmitted to the detection unit 22 and the detection unit 22 is deformed, thereby preventing the detection accuracy from deteriorating.

 The outer cylindrical portion 27 absorbs the deformation of the detecting portion 22 due to thermal expansion or the deformation of the case 3, and prevents the deformation of either the detecting portion 22 or the case 3 from affecting the other. That is, it is possible to prevent the deformation of the detection unit 22 due to the thermal expansion from being hindered by the case 3, and to prevent the deformation of the case 3 from deforming the detection unit 22.

 As shown in the enlarged view of FIG. 5 (b), the diaphragm 2 is located between the first and second grooves 9, 10 when the inner diameter up to the outer periphery of the detecting section 22 is ψa. The thickness b of the outer cylindrical portion 27 that absorbs the deformation due to the thermal expansion of the detecting portion 22 or the case 3 is 2 Za or more and 2 OZa or less, and the deformation region length of the outer cylindrical portion 27 c Is set to 6 / a or more and 60a or less.

In addition, the surface of the annular portion 26 that comes into contact with the fluid is set as the reference position, and the depth d recessed from the reference position of the surface of the detection portion 22 is set to 1 OZa or more and 60 / a or less. I have. In order to measure the output change in the above setting range, the output change was measured at the upper and lower limits of the setting range. That is, assuming the inner diameter φ a = 2 O mm to the outer circumference of the detection section 22, the thickness b of the outer cylindrical section 27 is b = 0.1111111 and 1 111111, and the deformation area length c of the outer cylindrical section 27 = 0.3 mm and 3 mm, surface depth d of detector 22 = 0.5 mm and 3 mm, load F when tightening was set to 500 kg weight, and output change was measured. .

 The result was as shown in FIG. As shown in Fig. 6, within the setting range, the output change due to the effect of tightening could be kept within 3% of the specification. The experimental values were evaluated as φ a = 20 mm, b = 0.1 mm, c = 0.5 mm, and d = 1.5 mm. . 8%, which is at the same level as the value in Fig. 6, confirming the effectiveness.

 Like the first embodiment, such a pressure sensor 1 ′ according to the present embodiment causes the thermal expansion of the detection unit 22 to be hindered by the case 3 even when the fluid temperature changes rapidly. Permanent deformation of the detection section 22 can be suppressed, and detection accuracy can be improved. For example, when the fluid 7 at 0 ° C and 150 ° C flows alternately and repeatedly, the fluctuation of the zero point due to the output change every time the flowing fluid changes can be suppressed within 3%.

 Further, the deformation of the case 3 due to the tightening of the clamp or the like does not affect the detection unit 22, the detection unit 22 is maintained in a substantially constant shape, and the fluctuation of the output change can be suppressed within 3%.

 Furthermore, since the diaphragm 2 and the case 3 can be integrally processed, there is no need for welding and finishing processes, and man-hours can be reduced.

 (Verification of output change)

Using the above first and second embodiments and the structure of the conventional technology, the output change was measured and verified. Figure 7 shows the results of verification of the output change. Here, the pressure sensor 1 ′ used as an implementation model of the second embodiment has an inner diameter φ a of 20 mm, an outer cylindrical portion 27 having a thickness b of 0.8 mm, and an outer cylindrical portion 2 having a thickness b of 0.8 mm. The length c of the deformation region in Fig. 7 is 0.5 mm, and the depth d from the pressure receiving surface of the detecting portion 22 to the end R on the mounting port side of the annular portion 26 is 1.5 mm.

 Verification measures the output change of external force (clamping effect) such as compression and bending by clamp, and the output change after repeated inflow of 0 ° C fluid for 2 minutes and inflow of 150 ° C fluid for 2 minutes (thermal shock). Thus, the effect of the present invention was verified.

As shown in FIG. 7, in the conventional structure, the fluctuation of the zero point due to the effect of tightening was 12%, and the fluctuation of the zero point due to the thermal shock was 10%, whereas in the model of the first embodiment, The fluctuation of the zero point due to the effect of tightening is 2.2 ° / ₀ , the fluctuation of the zero point due to thermal shock is _0.8 %, and the fluctuation of the zero point due to the effect of tightening is 1.6% in the model of the second embodiment. The fluctuation of the zero point due to the impact was 1.5%, and the effect of suppressing the fluctuation of the output change of the present invention within 3% could be verified.

 (Third embodiment)

 The third embodiment will be described with reference to FIG. 8 and FIG. FIG. 8 is a cross-sectional view showing a pressure sensor of a comparative example using a bag nut method. FIG. 9 is a sectional view showing a pressure sensor according to the third embodiment.

 Although the pressure sensors according to the first and second embodiments have a shape used when fastened by a ferrule-type clamp or the like as shown in FIG. 1, in the present embodiment, the IDF / ISO This shape is used when the fastening load of a screw union joint (commonly referred to as a bag nut (annular member): hereinafter referred to as a bag nut) is large.

If the diaphragm of the present invention is directly applied to the bag nut method, The configuration of the comparative example is as shown in FIG. However, since the bag nut 11 is tightened with a large-diameter screw, a few tons of axial force is applied. + May occur several%.

 That is, FIG. 8 shows an example of a bag nut 11 of 2 S, and the bag nut 11 is pressed against the mounting opening 4 via the packing 6 with the hexagon nut 12 to seal. . Specifically, a hexagon nut 12 is screwed into the mounting port 4, and a bag nut 11 and a packing 6 are provided between the end face of the mounting port 4 and the inwardly projecting portion of the hexagon nut 12. And fix it. The screw diameter of this hexagon nut 12 is 64 mm, and the maximum axial load generated when tightened is several tons. In the bag nut 11, the load P1 and the reaction force P2 of the packing 6 act on the diaphragm 2 via the bag nut 11, and as a result, the zero point fluctuates by more than 10%.

 Therefore, an embodiment that solves the problem of the bag nut method will be described below with reference to FIG. In the pressure sensor 1 "shown in FIG. 9 (a), the case 3 having the diaphragm 2 is connected to the bag nut 11 and the screw portion 33. In this configuration, the hexagon nut 12 is tightened. The axial load P1 and reaction force P2 generated in this case act on the bag nut 11, but the transmission of force to Case 3 is blocked by the groove S between Case 3 and the bag nut 11. That is, a part of the forces P l and P 2 is transmitted through the screw part 33, but this part absorbs the deformation, and the transmission of the force to the diaphragm 2 becomes small. In the pressure sensor 1 "shown in FIG. 9 (a), it is necessary to arrange an O-ring 13 in the groove S to prevent fluid from entering.

The dimensions that the pressure sensor 1 "shown in Fig. 9 (a) can take are DO for the diameter of the diaphragm 2, D1 for the diameter of the case 3 to the gap S, and C Assuming that the height of thread 3 is h O and the length of thread 3 3 is hi, D 1> 1.3 D 0, h 0> 0.3 DO, h 1 <0.4 h O Becomes valid.

 In the pressure sensor 1 "shown in FIG. 9 (b), a flange 34 is provided in the case 3, and the flange 34 is attached to the end face of the mounting port 4 together with the bag nut 11 through the packing 6 with the hexagon nut. It is sandwiched and fixed between the inward convex portions of 12. Even in this case, the axial load P1 and the reaction force P2 are applied only to the flange portion 34, and the ¾ shape is absorbed at this portion. As a result, the transmission of force to the diaphragm 2 is slight. Even in the pressure sensor 1 "in Fig. 9 (b), the dimension value is defined as h1 as the length of the collar portion 34 in the effective range described above. Meet.

 In the pressure sensor 1 "shown in FIG. 9 (c), the screw part 33 is formed in the case 3 as in FIG. 9 (a), but the case 3 is the second case (annular member). 4 is connected to the mounting part 4 by a screw part 33. The second case 14 is fastened to the mounting port 4 by a ferrule type clamp 5. 15 is an O-ring that seals similarly to the packing 6. In the pressure sensor 1 "shown in FIG. 9 (c), an example is shown in which the second case 14 is fastened with the ferrule-type clamp 5, but the second case 14 is an example. The case can be changed. As described above, this embodiment can cope with a case where the mounting method is changed, and can exert the same effect.

In the pressure sensor 1 "shown in FIG. 9 (d), a diaphragm 2 having a shape in which the detection part 22 protrudes toward the mounting port side R as shown in FIG. 4 (c) is used. Yes, the screw part 33 is formed in the case 3 and the connection is made in the same manner as in Fig. 9 (a) As described above, even if the diaphragm 2 is changed within the scope of the present invention, the present embodiment is implemented. The configuration of the form of holds. Industrial applicability

 As described above, according to the present invention, the diaphragm allows the detecting section to be deformed by thermal expansion, and prevents the deformation of the housing to which the diaphragm is attached from affecting the detecting section. And a housing in a non-contact state, and a deformation absorbing portion for absorbing deformation due to thermal expansion of the detecting portion or deformation of the housing between the detecting portion and a fixing position of the diaphragm fixed to the housing. If the detection unit is deformed due to thermal expansion, the detection unit and the housing are kept in a non-contact state, and even if there is a difference in heat capacity between the detection unit and the housing, the deformation due to thermal expansion of the detection unit is suppressed. This allows for permanent deformation of the detector caused by the thermal expansion of the detector being hindered by the housing, even when the fluid temperature changes suddenly. Improvement can be achieved. Therefore, it is also possible to prevent the final diaphragm from being damaged due to repeated permanent deformation of the detecting section. On the other hand, since the deformation absorbing section deforms and absorbs the deformation due to the thermal expansion of the detecting section, no stress is generated between the deformation absorbing section and the housing due to the deformation of the deformation absorbing section. '

When the housing is deformed, the detector and the housing are kept out of contact with each other, and since the deformation of the housing does not affect the detector, the detector is maintained in a substantially constant shape to suppress fluctuations in output change. I can do it. On the other hand, the deformation of the housing is transmitted to the deformation absorbing part, but the deformation of the housing is deformed and absorbed by the deformation absorbing part.Therefore, stress due to the deformation of the deformation absorbing part is generated between the deformation absorbing part and the detecting part. Nor. The deformation absorbing part is positioned so that the fixed position is different from the same direction as the pressure receiving surface of the detector, so that deformation due to thermal expansion of the detector is hindered in the same direction as the pressure receiving surface of the detector. Without the housing The deformation does not affect the detection unit.

 A protection section is provided at the end of the detection section connected to the deformation absorption section to prevent the deformation of the deformation absorption section from being transmitted to the detection section, so that the protection section prevents the deformation of the deformation absorption section from being transmitted to the detection section. It is possible to prevent the detection accuracy from deteriorating.

 Assuming that the thickness of the detecting part is t0, the thickness of the deformation absorbing part is t1, and the length of the deformation region of the deformation absorbing part is L, tl <l.5 X tO and L> 2 By satisfying the condition of Xt0, for example, when the fluid at 0 ° C and 150 ° C alternately flows, the fluctuation of the zero point due to the output change every time the flowing fluid changes is kept within 3%. And the detection accuracy can be improved.

 Assuming that the cross-sectional area of the protection unit is A, the condition of A <100 X t OX t O is satisfied, preventing the deformation of the deformation absorption unit from being transmitted to the detection unit and detecting the heat capacity of the protection unit. It is possible to prevent the protection unit from obstructing the thermal expansion of the detection unit due to the heat capacity of the protection unit becoming too large.

 The deformation absorbing part is a thin part between two grooves formed adjacent to each other from the front and back sides that come into contact with the fluid, so that the production of a diaphragm with a thin part is integrated with the housing. It is only necessary to machine the two grooves in this state, and it can be machined simultaneously with the housing, eliminating the welding and finishing steps of joining the diaphragm to the housing, reducing the number of steps and facilitating production. In addition, the depth of the groove on the diaphragm surface is shallow, so that dirt does not easily accumulate in the groove, making it suitable for sanitary food products.

 Since the thin portion is provided between the first groove on the outer periphery of the front surface and the second groove on the inner diameter side of the first groove on the back surface, the thin portion can be formed by simple processing. Can be.

Assuming that the diameter of the detector is a, the thickness between the grooves is 2 Za or more and 20 a or less. By forming the thin portion by setting the length between the bottom and the groove to be 6 Za or more and 60 a or less, the thin portion absorbs a deformation or a housing deformation due to thermal expansion of the detecting portion. Therefore, the detection accuracy can be improved.

 Assuming that the diameter of the detection unit is a, the detection is more excellent by setting the depth of the surface of the detection unit in contact with the fluid, which is recessed from the reference position, at 1 mm / a or more and 60 Za or less. Accuracy can be improved.

 An annular member that is clamped and fastened by a fastening member is provided in the mounting opening, and the housing to which the diaphragm is secured is fixed to the annular member by screwing. Since the deformation of the housing is kept low and the deformation absorbing portion deforms and absorbs the deformation of the housing, no stress is generated between the deformation absorbing portion and the detecting portion due to the deformation of the deformation absorbing portion.

 An annular member is provided in the mounting opening to be clamped and fixed by a fastening member, and a flange portion is formed in a housing to which the diaphragm is fixed. The flange portion is also clamped and fixed together with the annular member by the fastening member, thereby securing the housing. Since only the collar part is directly clamped and fixed by the fastening member, the deformation of the housing is kept low, and the deformation absorbing part deforms and absorbs the deformation of the housing. No stress is generated between the deformation absorbing portions due to the deformation.

Claims

The scope of the claims  1. In a pressure sensor provided with a diaphragm having a detection unit for receiving fluid pressure,  The diaphragm allows the detection unit to deform due to thermal expansion, and sets the detection unit and the housing in a non-contact state so that the deformation of the housing to which the diaphragm is attached does not affect the detection unit. And a deformation absorbing section for absorbing deformation due to thermal expansion of the detection section or deformation of the housing between the detection section and a fixed position of the diaphragm fixed to the housing. Features pressure sensor.  2. The pressure sensor according to claim 1, wherein the deformation absorbing section is positioned such that the fixed position is different from a pressure receiving surface of the detection section from a same plane direction.  3. A protection section for preventing deformation of the deformation absorbing section from being transmitted to the detection section is provided at an end of the detection section connected to the deformation absorbing section. 2. The pressure sensor according to item 2.  4. Assuming that the thickness of the detecting section is t 0, the thickness of the deformation absorbing section is t 1, and the length of the deformation area of the deformation absorbing section is L,  t 1 <1.5 X t O, power, L> 2 X t O 4. The pressure sensor according to claim 1, wherein the pressure sensor satisfies the following condition.  5. If the cross-sectional area of the protection part is A,  A <1 0 0 X t O X t O 5. The pressure sensor according to claim 3, wherein the pressure sensor satisfies the following conditions. 6. The deformation absorbing portion is a thin portion between two adjacent grooves formed on both sides of the front surface and the back surface that come into contact with the fluid. The pressure sensor according to claim 1, wherein  7. The thin-walled portion is provided between a first groove on an outer periphery of a front surface and a second groove on an inner diameter side of the first groove on a rear surface. Pressure sensor.  8. If the diameter of the detector is a,  The thin portion is formed by setting the thickness between the grooves to 2 / a or more and 20 / a or less and the length between the grooves to 6 / a or more and 60 / a or less. Item 8. The pressure sensor according to item 6 or 7.  9. If the diameter of the detector is a,  9. The pressure sensor according to claim 8, wherein a depth of the surface of the detection unit, which is in contact with the fluid, recessed from a reference position is set to 10 / a or more and 6OZa or less.  10. Equipped with an annular member that is fastened and fastened by a fastening member in the mounting opening  The pressure sensor according to any one of claims 1 to 9, wherein a housing to which the diaphragm is fixed is fixed to the annular member by screws.  1 1. An annular member which is fixed to the mounting opening by being clamped  10. A flange formed in a housing to which the diaphragm is fixed, wherein the flange is also fixed together with the annular member by being clamped and fixed by the fastening member. Or the pressure sensor according to item 1.