JP3318804B2 - Differential pressure sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a strain gauge provided on one surface of a strain-generating portion of a double-sided pressure-receiving diaphragm to differentiate the pressure fluid introduced on each side of the strain-generating portion of the diaphragm. The present invention relates to a differential pressure sensor for measuring pressure.

[0002]

2. Description of the Related Art FIG. 5 shows an example of the structure of a conventional differential pressure sensor. In FIG. 5, reference numeral 51 denotes a hermetic member having a plurality of hermetic seal portions (meaning of a sealing member, the same applies hereinafter), and 52 denotes a signal input / output line fixed to each of the hermetic seal portions in a sealed state. The number of hermetic seal portions 51 matches the number of signal input / output lines 52. The signal input / output line 52 externally supplies power to a differential pressure detecting electric unit disposed inside the differential pressure sensor,
Alternatively, it is a conductor having a function of extracting a detection signal output based on a detection operation of the electric unit to the outside. Further, the hermetic member 51 is provided in the space 6 inside the differential pressure sensor which is in a high pressure state by introducing pressure oil, for example.
0, a member having a function of drawing out the signal input / output line 52 to the outside while maintaining a high sealing property, and the hermetic seal portion as a part having this function is:
It is provided corresponding to each of the plurality of signal input / output lines 52. The hermetic seal portion is, for example, a signal input / output line 5.
2 and a resin or the like that fills the above-mentioned hole in a state where the signal input / output line 52 is made to pass through to fill the hole. Various structures of the hermetic seal portion have been conventionally proposed, and any hermetic seal structure can be adopted in the present invention. Therefore, the hermetic seal portion is not specifically shown in FIG. Only the line 52 is shown by a broken line.

[0005] The hermetic member 51 is disposed at an upper opening position in FIG. 5 in a housing recess 54 having a substantially circular cross section, for example, formed in the center of the main body 53. An O-ring 55 is interposed between the hermetic member 51 and the housing recess 54 of the main body 53, thereby maintaining the sealing performance of the gap formed in the contact portion. In the case where the differential pressure sensor according to the present invention is used to detect a differential pressure of each part of an oil passage in a hydraulic device such as a hydraulic shovel, for example, the main body 53 may be located near a main oil passage in the hydraulic device. In FIG. 5, a part of the wall is taken out and its cross section is shown.

[0004] 56 is a diaphragm preferably made of a metal material. The diaphragm 56 is provided at the bottom of the accommodation recess 54. An O-ring 57 is interposed between the diaphragm 56 and the housing recess 54 to seal a gap. A substantially film-shaped strain-generating portion 56a is formed in the upper central portion of the diaphragm 56. The strain-generating portion 56a receives different pressures from both sides, and functions as a strain-generating portion that generates a strain based on a difference between the pressures. The fluid for applying pressure is, for example, hydraulic oil flowing inside a hydraulic device. Flexure section 56a
Is formed on one surface (the upper surface in the illustrated example).
8 (hereinafter, referred to as a film forming unit 58). The film forming unit 58 is manufactured by applying a semiconductor film forming technique, and includes, for example, four strain gauges, and these strain gauges are electrically connected to form a Wheatstone bridge circuit, At the same time, a predetermined voltage is applied to maintain an electrical equilibrium state. Fluids having different pressures A and B are guided to the upper and lower sides of the strain-generating portion 56a, and the application of those pressures causes a strain in the strain-generating portion 56a. The resistance value changes to break the equilibrium state, and a voltage corresponding to the differential pressure is output from the output terminal of the Wheatstone bridge circuit.

[0005] Hermetic member 51 and diaphragm 56
A cylindrical spacer 59 is disposed between the two. The spacer 59 forms a required space 60 between the hermetic member 51 and the diaphragm 56. A fluid of pressure B is introduced into this space, and the space is in a high pressure state according to the pressure of the pressure fluid (fluid of pressure B). In this space, a conductor 61 that electrically connects the input / output end of the film forming unit 58 and the lower end of each signal input / output line 52 is arranged. The signal led out by the signal input / output line 52 is led to an amplifier (not shown).

According to the conventional differential pressure sensor having the above-described structure, the diaphragm 56 having the film forming portion 58 and the hermetic member 51 having the hermetic seal portion are formed in separate steps, and then the film forming portion 58 is formed. The input / output end and the lower end of each signal input / output line 52 are connected by, for example, a conductor 61. More specifically, a conductive wire 61 is adhered to the upper surface of the diaphragm 56, and thereafter, connection to the conductive wire 61 is performed using a wire bond or a conductive adhesive so that input to or output from the strain gauge can be performed. The upper end of the conductor 61 is connected to the lower end of each signal input / output line 52 by means such as solder. After that, the diaphragm 56 and the hermetic member 51 are incorporated into the housing recess 54 with the spacer 59 interposed therebetween. Further, the main body 5
After assembling the other components to 3, the cover member 62 is attached, and the whole sensor is fixed using a plurality of bolts 63.

[0007]

In a conventional differential pressure sensor, various components such as a diaphragm are incorporated in a main body,
The use of an assembly structure in which a plurality of bolts are used as the fastening means has led to an increase in the size of the sensor, and also has the problem of being affected by the stress from the sensor-fixing bolts and deteriorating the detection performance. Was. This problem generally occurs in a differential pressure sensor having a similar structure other than the above structure.

It is an object of the present invention to firstly make the differential pressure sensor compact by making use of beam welding such as electron beam welding or ordinary welding, and secondly to carry out the above beam welding. Thirdly, it is intended to have a sensor structure which can be easily performed, thirdly, to reduce the initial distortion of the diaphragm caused by distortion of the mounting screw portion due to the welding portion and the tightening torque of the differential pressure sensor, and fourthly, to reduce the welding portion. A fifth object of the present invention is to provide a differential pressure sensor designed to reduce the influence of the pressure fluid on the pressure fluid, and fifthly exhibit high detection accuracy.

[0009]

According to the present invention, there is provided a differential pressure sensor comprising: a double-sided pressure receiving type diaphragm having a differential pressure detecting portion provided on one surface of a strain generating portion; and a fluid having a different pressure from a fluid passage portion. It has a first and a second introduction passage for introducing on each side of both sides of the strain generating portion of the intake diaphragm,
Further, an annular support portion having a mounting screw portion on an outer peripheral portion is provided, and an annular support portion to which the diaphragm is joined is formed in a convex stepped shape at the center of the outer end surface portion, and the first introduction passage is annular. A sensor mounting portion formed to communicate with an inner region of the support portion and a second introduction passage communicating with an outer region of the annular support portion, the sensor mounting portion being fixed to the fluid passage portion by a mounting screw portion, and having a cylindrical shape; One of the opening ends is welded to a peripheral edge of the outer end surface of the sensor mounting portion, and a hermetic member for fixing a signal input / output line is fixed to the other opening end. A diaphragm accommodating portion in which a space for accommodating the pressure fluid introduced by the second introduction passage is formed, and a conducting wire connecting between the input / output terminal of the differential pressure detecting portion and the signal input / output line, and At the annular support Parts and an annular portion of the diaphragm are joined by beam welding over the entire circumference.

In the above configuration, it is preferable that the thickness of the annular supporting portion is smaller than the thickness of the annular portion of the diaphragm. In addition, a backing member is provided inside the joint between the sensor attachment portion and the diaphragm accommodating portion to insulate the respective walls of the sensor attachment portion and the diaphragm accommodating portion to separate the joint space from the space of the diaphragm accommodating portion. Can also. Further, it is preferable to form an annular recess around the annular support.

[0011]

According to the present invention, in producing the differential pressure sensor, bolt fastening is stopped and beam welding such as electron beam welding or laser beam welding is mainly used as a joining means. Can be achieved.

Further, when welding the annular portion of the diaphragm and the annular support portion by irradiating an electron beam or the like from the lateral direction, the annular support portion is formed in a convex step shape so as to protrude from the outer end surface portion. Therefore, beam welding can be easily performed.

By making the thickness of the annular support portion smaller than the thickness of the annular portion of the diaphragm, or by forming an annular recess around the annular support portion to increase the axial length of the annular support portion. Further, a distortion caused by welding and a distortion due to a tightening torque for mounting the sensor are prevented from affecting the diaphragm, and a distortion buffer is provided substantially between the diaphragm and the joint.

The provision of the backing member prevents foreign matter generated by welding for forming a joint from being mixed into the pressurized fluid introduced into the internal space.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows the internal structure of one embodiment of the differential pressure sensor according to the present invention. In FIG. 1, reference numeral 11 denotes a sensor main body. The sensor main body 11 is formed by joining and integrating a cylindrical upper member 11a and a columnar lower member 11b.

The upper member 11a has a cylindrical shape with an internal space 12 formed in the center. Power is supplied to the internal space 12 to a double-sided pressure receiving type diaphragm 13 which generates distortion and deformation in accordance with a differential pressure, and a differential pressure detecting film forming unit 18 formed on one surface of a thin strain generating portion of the diaphragm 13. 1 for extracting the differential pressure detection signal from the differential pressure detecting film forming section 18
4. A hermetic member 16 having a portion for fixing and sealing a signal input / output line 15 connected to the conductor 14 and electrically connecting the inside and the outside of the differential pressure sensor is provided. Conductor 14
For example, a general connection line or an FPC (flexible print circuit) is used. A pressure fluid is introduced into each side of both surfaces of the strain generating portion of the diaphragm 13. The differential pressure detecting film forming unit 18 is formed by a semiconductor film forming technique, and includes four strain gauges forming a Wheatstone bridge circuit and wirings connecting them. The hermetic member 16 is fixed to one opening of the upper member 11a, and is prevented from coming off by the inner peripheral step portion 17. A liquid-tight structure is formed between the hermetic member 16 and the upper member 11a to prevent the pressure fluid introduced into the upper member 11a from leaking outside the upper member 11a. As the liquid-tight structure, various structures can be adopted. In this embodiment, the upper member 11a and the hermetic member 16 each made of a metal material are arranged at the mounting position of the upper member 11a. In this state, the peripheral edge of the inner surface of the hermetic member 16 is pressed by a ring-shaped pressing member, and a liquid-tight structure is formed based on the caulking action. When assembled as the sensor main body 11, the upper member 11a functions as a diaphragm accommodating portion having an internal space for accommodating the diaphragm 13 and other electric elements, and at the same time, one of the above-mentioned pressure fluids is subjected to strain deformation of the diaphragm. Functions as a pressure chamber for introduction into the section.

The lower member 11b is, for example, a pressure fluid having a pressure A (hereinafter, referred to as a pressure fluid (A)) and a pressure fluid having a pressure B from a fluid passage of a hydraulic device (a device to be measured through which the pressure fluid flows). Channels 19 and 20 are formed which take in the pressure fluid (hereinafter, referred to as pressure fluid (B)) and guide each pressure fluid to both sides of the strain generating portion of the diaphragm 13. For example, when the pressure fluid (A) and the pressure fluid (B) take in the pressure fluid from a hydraulic device of a hydraulic shovel and detect a differential pressure, for example, the upstream pressure fluid and the downstream pressure fluid are taken in, It is the same as the pressure fluid. Note that different pressure fluids may be used as the pressure fluid (A) and the pressure fluid (B). The pressure fluid (A) is guided to the lower surface side of the strain generating portion of the diaphragm 13 through the passage 19, and the pressure fluid (B) is guided to the upper surface side of the strain generating portion of the diaphragm 13 through the passage 20 and the internal space 12. I will Further, a sensor mounting screw portion 29 is formed on the outer peripheral surface of the lower member 11b, and the sensor body 11 is mounted on a differential pressure measuring portion provided in a hydraulic device or the like by a tightening torque applied to the screw portion 29. Fixed to the part. The lower member 11b is
It functions as a sensor mounting part having a pressure fluid introduction structure.

The upper member 11a and the lower member 11b are joined by a welded portion 21 at the outer peripheral edge of each opposing surface, and are integrated as a sensor body 11. Generally, beam welding such as an electron beam or a laser beam is used for welding the upper member 11a and the lower member 11b, but other welding methods other than beam welding can also be used.
For example, in electron beam welding, the joint is irradiated with an electron beam from the lateral direction indicated by an arrow 22 outside the contact point to be the welded portion 21, and this electron beam irradiation is performed over the entire circumference of the contact point, and The contact portions of the lower member 11a and the lower member 11b are melted to join them. When attaching the lower member 11b to a hydraulic device or the like, a plurality of O-rings 23 are provided at required locations between the lower member 11b and the hydraulic device or the like, thereby leaking the pressure fluid to the outside, and Leakage between the passages 19 and 20 through which pressure fluids having different pressures flow are prevented.

In FIG. 1, the upper end of the lower member 11b, on which the welded portion 21 is formed, has a substantially flat surface as a whole. An annular support portion 24 is formed. The annular support portion 24 has, for example, an annular shape, and is formed by giving a predetermined height (h) so as to protrude upward (outward in the mounting structure) from the upper end portion. An annular support portion 24 formed at the upper end of the lower member 11b
When viewed from the side, it projects outward in the form of a convex step.

An end space of the passage 19 is formed at the center (inner area) of the annular support portion 24. An end face of the annular support portion 24 is joined to an annular portion (for example, a circular cylindrical portion) of the diaphragm 13 by welding. In this part welding, beam welding such as the aforementioned electron beam or laser beam is used. 25 is a welding part. Since the annular support portion 24 is formed to have the height (h) as described above, the welded portion 25 of the annular support portion 24 is connected to the upper member 11a formed on the outer periphery of the upper end of the lower member 11b. 1 is located above the welded portion 21 in FIG. The welding portion 25 between the annular support portion 24 and the diaphragm 13 is irradiated with an electron beam from the lateral direction indicated by an arrow 22 to the contact portion, as in the case of the welding portion 21 when using beam welding. The irradiation of the electron beam is performed over the entire circumference of the contact point. Since the position of the contact portion between the annular support portion 24 and the diaphragm 13 is shifted to the "outside position" as compared with the position of the joint portion between the upper member 11a and the lower member 11b, actual beam welding work is performed. Can be easily performed. Here, the “outside position” is the upper side in FIG. 1, and the electron beam emitted from the direction shown by the arrow 22 is not blocked by the lower member 11 b, and the electron beam emitted from the annular support portion 24 and the diaphragm 13 This means the position corresponding to the contact point.

The thickness of the annular support portion 24 is formed to be smaller than the thickness of the annular portion 13a of the diaphragm 13. As a result, the residual strain caused by the beam welding between the diaphragm 13 and the annular support portion 24 escapes to the thin portion of the annular support portion 24, and is welded to the strain-induced portion of the diaphragm 13 by welding. Since the influence of the residual strain can be minimized, a differential pressure sensor with high detection accuracy can be obtained. Thereafter, the differential pressure signal detected by the film forming unit 18 provided on the strain-generating unit of the diaphragm 13 is guided to an amplifier (not shown) via the conductor 14 and the signal input / output line 15 and amplified by the amplifier. Then, it is taken out of the sensor.

Further, according to the thin portion of the annular support portion 24, distortion caused by welding at the weld portion 21 is also reduced.
The escape can be achieved by interposing the thin portion.

Reference numeral 26 denotes a cover member mounted on the upper portion of the sensor body 11. The cover member 26 is an upper member 11a.
Is attached via an O-ring 27. Cover member 2
The internal space 28 of FIG.

An example of a procedure for manufacturing a differential pressure sensor having the above structure will be described. First, the lower member 1 which is a sensor mounting portion
1b, the annular portion 13a of the diaphragm 13 of the double-sided pressure receiving type is arranged on the annular support portion 24 of the lower member 11b, and an electron beam or the like is applied from outside to the contact portion between the annular support portion 24 and the annular portion 13a. And welded by beam welding. Next, an upper member 11a, which is a cylindrical diaphragm housing in which a hermetic member 16 having a signal input / output line 15 is fixed to one opening end, is prepared. Signal input / output line 15
Is connected to a conducting wire 14. The conductive wire 14 is connected to an input / output terminal of a film forming unit 18 formed on a strain-flexing portion of the diaphragm 13, and then the upper member 11a is disposed on an outer end surface of a lower member 11b, The contact portion between the peripheral edge of the outer end surface and the other open end of the upper member 11a is joined by welding from the outside. In the above manufacturing method, the film forming unit 18
The timing of connection of the conducting wire 14 to the input / output terminal of can be arbitrarily determined in relation to the beam joining of the diaphragm 13. That is, the conductor 14 may be connected after performing the beam welding as described above, or the beam welding of the diaphragm 13 may be performed after the connection of the conductor 14.

Another embodiment shown in FIG. 2 will be described. FIG. 2 shows the upper member 11a and the lower member 11b shown in FIG.
1 shows an example of an actual structure before welding around a welded portion between the diaphragm 13 and an example of an actual structure before welding between the diaphragm 13 and the annular support portion 24. In FIG. 2, substantially the same elements as those shown in FIG. 1 are denoted by the same reference numerals.

In FIG. 2, reference numeral 31 denotes a contact portion between the upper member 11a and the lower member 11b, and a ring-shaped backing member 32 is arranged along the contact portion 31 on the inner surface side of the contact portion 31. . The contact portion between the upper member 11a and the lower member 11b is joined by being irradiated with an electron beam from the outside, and foreign matter such as welding spatter generated at that time is prevented from being mixed into the pressure fluid introduced into the internal space 12. In order to prevent this, a backing member 32 that separates the contact portion 31 from the internal space 12 is disposed. The backing member 31 is inscribed in the upper member 11a and the lower member 11b. Reference numeral 33 denotes an outer peripheral projection for accurately positioning the diaphragm 13 and arranging the diaphragm 13 on the annular support 24 when the diaphragm 13 is joined to the end surface (the upper surface in FIG. 2) of the annular support 24 by beam welding. Department.
The above-mentioned welded portion 25 is formed by irradiating the contact portion between the annular portion 13a of the diaphragm 13 arranged in such a state and the annular support portion 24 from the outside lateral direction. Note that the outer peripheral edge protruding portion may be formed on the side of the diaphragm 13 near the annular joint.

FIG. 3 shows another embodiment of the present invention. 3, elements substantially the same as the elements described in FIG. 2 are denoted by the same reference numerals, and detailed description thereof will be omitted. A characteristic part in this embodiment is that an annular concave portion 34 is formed around the annular support portion 24 at the upper end of the lower member 11b,
That is, the length of the annular support portion 24 in the axial direction is increased. Other configurations are the same as those of the above-described embodiment. In the present embodiment, when the sensor main body 11 is attached to the mounting location of the hydraulic device using the screw portion 29, the sensor main body 1
It is possible to prevent the distortion of the sensor main body 11 due to the tightening torque given to 1 from affecting the diaphragm 13. That is, by forming the concave portion 34 in the vicinity of the location where the distortion occurs due to the tightening, the distance from the location where the main body portion distortion occurs to the diaphragm is kept long, and the length of the annular support portion 24 in the axial direction is increased so that the thin portion is formed. 2
4a, 24b, and these thin portions 24a, 24b
This reduces distortion transmitted to the diaphragm. Thereby, a differential pressure sensor with high detection accuracy is realized.

FIG. 4 shows another embodiment of the present invention. 4, elements substantially the same as the elements described in FIG. 3 are denoted by the same reference numerals, and detailed description will be omitted. In this embodiment, in the annular support portion 24, a thin portion 24c is formed partially in addition to the joint portion with the diaphragm 13. According to this embodiment, the diaphragm 13 is formed in the sensor main body. This makes it possible to obtain a differential pressure sensor that is less affected by the applied strain and has a high detection accuracy.

In each of the above embodiments, the differential pressure sensor has been described. However, by guiding the pressure fluid to only one of the thin portions of the diaphragm 13, it can be used as a general pressure sensor. is there.

As described above, the thin portion is provided at the joint portion to be welded to the diaphragm 13, and the distance from the sensor body to the diaphragm is increased in order to avoid transmission distortion from the tightening portion for mounting the sensor. to take,
A differential pressure sensor with high detection accuracy can be manufactured by appropriately combining any of providing a thin portion in the middle of the strain transmission.

[0032]

As is apparent from the above description, according to the present invention, the assembly and manufacture of the differential pressure sensor does not employ a bolted structure, and at least uses electron beam welding or laser beam welding at the joint of the diaphragm. Since the beam welding such as welding is used, downsizing of the differential pressure sensor can be achieved. Regarding the joining of the diaphragm accommodating portion and the sensor attaching portion forming the sensor main body and the joining of the diaphragm and the annular supporting portion, the position of the joining portion of the diaphragm and the annular supporting portion is projected from the end of the sensor attaching portion. The end
Higher is formed than collision from the end than the position of the junction of the diaphragm housing portion and the sensor attachment portion when viewed from the side
Beam welding can be easily performed by setting it to a position where the beam is projected.

The thickness of the annular support portion is made smaller than the thickness of the annular portion of the diaphragm, or an annular concave portion is formed around the annular support portion to increase the axial length of the annular support portion. Thus, it is possible to prevent the distortion caused by the above and the distortion due to the tightening torque for mounting the sensor from affecting the diaphragm. Thereby, the detection accuracy of the differential pressure sensor can be improved.

Since the backing member is used in welding for joining the sensor mounting portion and the diaphragm accommodating portion, it is possible to prevent foreign matters generated by the welding from being mixed into the pressure fluid introduced into the internal space. Can be.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an internal structure of an example of a differential pressure sensor according to the present invention.

FIG. 2 is an enlarged longitudinal sectional view showing a practical structure of a main part of the differential pressure sensor.

FIG. 3 is a longitudinal sectional view showing another embodiment of the differential pressure sensor.

FIG. 4 is a longitudinal sectional view showing another embodiment of the differential pressure sensor.

FIG. 5 is a longitudinal sectional view showing the internal structure of a conventional differential pressure sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Sensor main body part 11a Upper member (diaphragm accommodating part) 11b Lower member (sensor attaching part) 13 Diaphragm 15 Signal input / output line 16 Hermetic member 18 Differential pressure detecting film forming part 19, 20 Passage 21, 25 Welding part 24 Annular support Department

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Fujio Sato 650 Kandamachi, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd. (72) Inventor Nobuyuki Toda 650 Kandamachi-cho, Tsuchiura-shi Ibaraki Hitachi Construction Machinery Within the Tsuchiura Plant (72) Inventor Kiyoshi Tanaka 650, Kandamachi, Tsuchiura-shi, Ibaraki Prefecture Inside the Tsuchiura Plant, Hitachi Construction Machinery Co., Ltd. 72) Inventor Toshio Honma Nagano Keiki Seisakusho Co., Ltd., 1-3-4 Higashimagome, Ota-ku, Tokyo (56) References JP-A-7-311111 (JP, A) JP-A-7-128171 (JP, A) JP-A-7-35635 (JP, A) JP-A-7-20539 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01L 9/04 101 G01L 19/00 G01L 13/06 H01L 29/84

Claims (4)

(57) [Claims] 1. A double-sided pressure receiving type diaphragm having a differential pressure detecting portion provided on one surface of a strain generating portion, and fluids of different pressures taken in from a fluid passage portion are provided on both sides of the strain generating portion of the diaphragm. In a differential pressure sensor having first and second introduction passages to be introduced, an annular support portion having a columnar shape provided with a mounting screw portion on an outer peripheral portion and to which the diaphragm is joined is provided at a central portion of an outer end surface portion. The first introduction passage is formed in a convex stepped shape, and the first introduction passage is formed so as to communicate with an inner region of the annular support portion, and the second introduction passage is communicated with an outer region of the annular support portion. A sensor mounting portion fixed to the fluid passage portion by a screw portion; a cylindrical shape; one opening end is welded to a peripheral portion of the outer end surface portion of the sensor mounting portion by welding; Signal input / output line at the end A diaphragm housing in which a fixed hermetic member is fixed and in which a space for accommodating the diaphragm therein and accommodating the pressure fluid introduced by the second introduction passage is formed; A differential pressure sensor, comprising: a conductor connecting between a terminal and the signal input / output line; wherein the annular support portion and the annular portion of the diaphragm are joined by beam welding over the entire circumference. 2. The differential pressure sensor according to claim 1, wherein the thickness of the annular support portion is smaller than the thickness of the annular portion of the diaphragm. 3. The differential pressure sensor according to claim 1, wherein said sensor mounting portion and said diaphragm housing portion are inwardly contacted with respective walls of said sensor mounting portion and said diaphragm housing portion inside a joint portion between said sensor mounting portion and said diaphragm housing portion. And a backing member for isolating the space of the diaphragm accommodating portion from the joint portion. 4. The differential pressure sensor according to claim 1, wherein an annular concave portion is formed around the annular support portion.