JP6349178B2 - Membrane gas meter - Google Patents

Description

  The present invention relates to a membrane gas meter that measures the flow rate of a fluid to be measured such as city gas.

Conventionally, various techniques relating to a membrane gas meter for measuring the flow rate of a fluid to be measured such as city gas have been proposed.
For example, in the membrane gas meter described in Patent Document 1 below, a distribution chamber mounting portion is provided on the upper surface of the lower case. The distribution chamber mounting portion is provided with a non-circular concave portion, for example, a crank base mounting portion having a single positioning hole having an approximately 8 shape.

  A crank base is screwed to the valve seat attached to the distribution chamber attaching portion. On the lower surface of the crank table, for example, an approximately 8-shaped positioning boss is provided so as to be engaged and positioned in the positioning hole of the crank table mounting portion. And a sealing agent is apply | coated to the upper surface of a crank base attaching part or a valve seat, and the lower surface of a crank base. Next, when the positioning boss of the crank base is inserted into the positioning hole of the crank mounting portion and engaged, the valve seat and the crank base are positioned in the distribution chamber mounting portion, and the lower surface of the valve seat is bonded and fixed to the distribution chamber mounting portion. By doing so, the assembly work is completed.

JP 2006-250810 A

  However, in the membrane gas meter described in Patent Document 1 described above, since the crank base is screwed to the valve seat, it is necessary to insert the female screw fitting into the valve seat, which increases the number of parts and increases the cost. In addition, after applying the sealant to the lower surface of the crankcase and valve seat, if the valve seat is to be installed simply by inserting the “positioning boss” of the crankbase into the “positioning hole”, the crankbase is fixed until the sealant is solidified. In addition, it is necessary to prevent the valve seat from being lifted from above, and the assembly work is complicated.

  Accordingly, the present invention has been made to solve the above-described problems, and an object thereof is to provide a membrane gas meter capable of reducing insert molding of a distribution chamber and speeding up assembly work. And

  In order to achieve the above object, a membrane gas meter according to claim 1 includes an upper case forming an inlet of a fluid to be measured and an outlet of the fluid to be measured, and a pressure of the fluid to be measured flowing into the upper case. A lower case forming a pair of measuring chambers separated by a membrane portion reciprocated by the liquid, and a fluid to be measured which is attached to a distribution chamber mounting portion of the lower case and flows in from the inflow port is distributed to the pair of measuring chambers And a crank base that rotatably supports a crank member that converts a reciprocating motion of the membrane portion into a rotational motion via a link mechanism portion, wherein the crank base is circular in cross section. A cylindrical main body portion in which a through-hole is formed in an axial direction and a rotation shaft portion of the crank member is rotatably fitted, and is extended coaxially downward by a predetermined length from a lower end portion of the cylindrical main body portion. The A step portion that is thinner than the main body portion, and a positioning arm portion that extends radially outward from the outer peripheral surface of the lower end portion of the cylindrical main body portion with respect to the central axis, and the lower case is A crank base mounting portion that is disposed adjacent to a lower side by a height substantially equal to the thickness of the positioning arm portion with respect to the upper end surface of the distribution chamber mounting portion, and the upper end surface of the distribution chamber mounting portion. To the portion adjacent to the upper end surface of the crank base mounting portion of the distribution chamber mounting portion and a width substantially equal to the width of the positioning arm portion, and perpendicular to the central axis of the crank base mounting portion. A positioning groove portion that is recessed along the direction and into which the positioning arm portion is fitted from above, and the distribution chamber is inserted through a distribution chamber mounting screw that fixes the distribution chamber to the distribution chamber mounting portion. The step of the crank table By inserting the positioning arm portion into the positioning groove portion while fitting the portion into the crank base attachment portion, and then fixing the distribution chamber to the distribution chamber attachment portion via the distribution chamber attachment screw. The base is fixed to the crank base mounting portion in a state where the positioning arm portion is pressed against the positioning groove by the bottom surface of the distribution chamber.

  The membrane gas meter according to claim 2 is the membrane gas meter according to claim 1, wherein the crank base has a positioning pin erected on an upper surface of a distal end portion of the positioning arm portion. Has a positioning recess into which the positioning pin is inserted in the bottom surface portion facing the positioning pin, and the distribution chamber is inserted into the distribution chamber mounting portion with the positioning pin inserted in the positioning chamber. It is fixed through a mounting screw.

  The membrane gas meter according to claim 3 is the membrane gas meter according to claim 1 or 2, wherein the distribution chamber is fixed to the distribution chamber mounting portion via the distribution chamber mounting screw. Then, it is bonded and fixed to the distribution chamber mounting portion.

  Furthermore, the membrane gas meter according to claim 4 is the membrane gas meter according to any one of claims 1 to 3, wherein the crank base is made of a synthetic resin containing polyacetal. .

  In the membrane type gas meter according to claim 1, the distribution chamber is fixed to the distribution chamber mounting portion with the distribution chamber mounting screw after the positioning arm portion is inserted into the positioning groove while the stepped portion of the crank base is inserted into the crank base mounting portion. To do. As a result, the crank base is fixed to the crank base mounting portion via the positioning arm portion pressed against the positioning groove by the distribution chamber, so that insert molding of the female screw fitting for mounting the crank base in the distribution chamber may be abolished. it can. In addition, it is only necessary to fix the distribution chamber with the distribution chamber mounting screw after the positioning arm portion is inserted into the positioning groove while the stepped portion of the crank base is inserted into the crank base mounting portion. Can be abolished, and the assembly work can be speeded up.

  In the membrane gas meter according to claim 2, a positioning pin provided upright on the top surface of the distal end portion of the positioning arm portion is fitted into a positioning concave portion formed in the bottom surface portion of the distribution chamber, thereby Positioning can be performed quickly, and the assembly work can be further accelerated with a simple configuration.

  In the membrane gas meter according to the third aspect, the distribution chamber is bonded and fixed to the distribution chamber mounting portion in a state of being fixed to the distribution chamber mounting portion by the distribution chamber mounting screw. Accordingly, the distribution chamber mounting screw can prevent the distribution chamber from being lifted, and it is not necessary to hold the distribution chamber from above until the sealant is solidified, thereby speeding up the assembly operation.

  Furthermore, in the membrane gas meter according to claim 4, the cylindrical main body portion of the crank base is formed of a synthetic resin containing polyacetal. Therefore, even if the bearing is abolished, the frictional force is reduced and the crank member is rotated. The shaft portion can be smoothly rotated.

1 is a partially cutaway front view of a membrane gas meter according to an embodiment. It is a top view at the time of removing an upper case. It is a principal part disassembled perspective view. It is a bottom view of a distribution chamber. It is X1-X1 arrow sectional drawing of FIG. It is a side view of a crank base. It is a top view of a crank base. It is X2-X2 arrow sectional drawing of FIG.

  Hereinafter, based on one embodiment which materialized the membrane type gas meter concerning the present invention, it explains in detail, referring to drawings.

First, a schematic configuration of the membrane gas meter 1 according to the present embodiment will be described with reference to FIGS. 1 and 2.
As shown in FIG. 1, a membrane gas meter 1 according to the present embodiment is a city gas meter that measures a flow rate of a city gas, which is an example of a fluid to be measured, and is connected in the middle of a city gas pipe 2. A meter case 3 having a vertically long rectangular parallelepiped shape is provided.

  The meter case 3 has an inlet 7 and an outlet 8 that are airtightly connected to the pipe 2 projecting from both ends in the longitudinal direction from the upper surface of the upper case 5 constituted by an upper case 5 and a lower case 6. It is provided and communicates with the meter case 3. The city gas is supplied to the inflow port 7 through the pipe 2 and is introduced into the intermediate chamber 9. The upper case 5 includes a pressure sensor that detects the gas pressure supplied to the membrane gas meter 1, a seismic detector that detects earthquake vibration, and a shut-off valve that shuts off the gas supply, and a control for controlling them. A component storage chamber for storing components such as a circuit portion is formed.

  As shown in FIGS. 1 to 3, the lower case 6 is provided with a pair of substantially cylindrical measuring chamber forming spaces 12 having a partition wall 11 at the center in the front-rear direction and a partition wall 11 at the bottom. ing. A membrane portion 13 that partitions the front chamber and the rear chamber is provided at the central portion in the front-rear direction of each measurement chamber forming space 12 so as to be reciprocally movable in the front-rear direction. Moreover, the opening part of each measurement chamber formation space 12 is obstruct | occluded by the lid member not shown. Thereby, each measurement chamber forming space 12 is partitioned into a pair of measurement chambers 15 by the film part 13.

  Further, a pair of blade shafts 16 is arranged on one end side in the left-right direction (the left end portion in FIG. 1) corresponding to each measurement chamber forming space 12. Each blade shaft 16 is inserted in an airtight manner through a seal member 18 formed of rubber or the like with each cylindrical boss 17 provided on the lower case 6 with its axial center directed in the vertical direction, A substantially central portion is supported so as to be rotatable. Moreover, the lower end part of each blade axis | shaft 16 is engage | inserted by the recessed part 19 formed in the lower case 6, and is supported so that rotation around an axial center is possible.

  One end of a blade (not shown) is fixed to the lower portion of each blade shaft 16, and the other end of the blade is connected to the center of the membrane portion 13 so as to be swingable by a hinge or the like. And each blade part 16 is comprised so that forward rotation and reverse rotation may be repeatedly performed with the reciprocating movement of each film | membrane part 13 in the front-back direction.

  As shown in FIGS. 1 and 2, a link mechanism portion 21 is provided at the upper end of each blade shaft 16. The link mechanism portion 21 includes two pairs of a large elbow metal 22 and a small elbow metal 23 in which end portions are rotatably connected to each other, and one end of each large elbow metal 22 is fixed to the upper end of each blade shaft 16. It is connected. In addition, the tip of each small elbow 23 is rotatably connected to the pivot shaft 26 of the crank member 25.

  As shown in FIGS. 1 to 3 and 6, the crank member 25 is rotatably fitted in a shaft hole 28 </ b> A of a cylindrical body portion 28 formed in a cylindrical shape of the crank table 27, and serves as an example of a rotating shaft portion. A functioning elongated cylindrical rotary shaft 31, a first arm 32 having a base end fixed to the upper end of the rotary shaft 31, a connecting shaft 33 erected at the distal end of the first arm 32, A second arm 35 having a base end fixed to the upper end of the connecting shaft 33, a pivot shaft 26 erected at the tip of the second arm 35, and a base end at the upper end of the pivot shaft 26. It is comprised from the fixed turning board 36. FIG.

  The central shaft 31A of the rotary shaft portion 31 formed of a hard synthetic resin such as polyacetal passes through the substantially central portion of the half portion on the tip end side of the swivel plate 36. Further, the first arm 32, the second arm 35, and the swivel plate 36 are located on a plane perpendicular to the central axis 31 </ b> A of the rotation shaft portion 31.

  As shown in FIGS. 1 and 3, a distribution chamber 37 is bonded to an upper end portion of the lower case 6 at each end of the link mechanism portion 21 with respect to each boss 17 through which the blade shaft 16 is airtightly inserted. A distribution chamber mounting portion 38 to be fixed is provided. The distribution chamber mounting portion 38 is provided with four gas supply / exhaust ports P1 to P4 communicating with the respective measurement chambers 15 separately. In addition, the gas discharge port Q communicating with the outflow port 8 provided in the upper case 5 is connected between the gas supply / discharge ports P1 and P2 communicating with the pair of measuring chambers 15 facing each other through the membrane portion 13, and each gas. A partition wall 39 partitions the supply / exhaust ports P3 and P4.

  The gas supply / discharge ports P2 and P3 communicating with the respective measuring chambers 15 facing each other through the partition wall 11 are partitioned by the partition wall 41 and provided adjacent to each other. On the upper end surface of the partition wall 41, a screw hole 42 into which a distribution chamber mounting screw 40 for fixing the distribution chamber 37 to the distribution chamber mounting portion 38 is screwed is formed at an edge portion on the boss 17 side. Further, the gas discharge port Q at the upper end portion of the partition wall 39 is provided on the upper surface portion in the front-rear direction facing the inlet of the flow path 43 in the upper case 5 communicating with the outflow port 8. A step 45 is formed at the end edge with a predetermined width, for example, a width of about 5 mm.

  As shown in FIG. 1 to FIG. 3, the step 45 has a substantially horizontally long rectangular shape with opposite corners on the opposite side to the distribution chamber 37 so as to close the substantially central portion of the gas discharge port Q in the front-rear direction. Both ends in the longitudinal direction of the bridge 47 extending outward are bonded and fixed. As a result, a substantially pentagonal inlet 46 is formed at a portion facing the flow path 43 in the upper case 5 communicating with the outlet 8. The bridge 47 is a plate-like body made of, for example, aluminum or stainless steel, and the upper surface of the bridge 47 is flush with the upper end surface of the distribution chamber mounting portion 38, that is, the upper end surfaces of the partition walls 39 and 41. Is attached.

  As shown in FIGS. 1 to 5, the distribution chamber 37 bonded and fixed to the distribution chamber mounting portion 38 is formed of a hard synthetic resin molded product such as phenol resin or polyacetal, and corresponds to each gas supply / discharge port P1 to P4. Thus, the gas flow paths R1 to R4 are formed. Further, between the gas supply ports P1 and P2, and between the gas supply ports P3 and P4, corresponding to the gas discharge ports Q, between the gas flow paths R1 and R2, and between the gas flow paths R3 and R4. In addition, the exhaust guide channels T1 and T2 are formed.

  The distribution chamber 37 has a through hole 48 into which the distribution chamber mounting screw 40 is inserted from above at the center of the side edge on the boss 17 side (the upper side in FIG. 4). A deep counterbore 48A having a circular shape in plan view having a diameter substantially equal to the diameter of the head of the distribution chamber mounting screw 40 and a depth substantially equal to the thickness of the head of the distribution chamber mounting screw 40 is formed at the upper end of the through hole 48. Is formed. Further, at a substantially central position between the through hole 48 and the central portion of the outer peripheral end surface of the distribution chamber 37 on the boss 17 side (upper side in FIG. 4), the crank base 27 is depressed by a predetermined depth from the bottom surface portion. A positioning recess 49 is provided in which the positioning pin 51A (see FIG. 6) is fitted over the entire height.

  As shown in FIGS. 1 to 3 and FIGS. 6 to 8, the crank base 27 that rotatably supports the rotating shaft portion 31 of the crank member 25 is formed of a hard synthetic resin such as polyacetal, and has a cylindrical shape. A cylindrical step portion 28B having a slightly smaller outer diameter extends from the lower end portion of the main body portion 28 to the outside in the axial direction with a predetermined length, for example, about 5 mm. A protruding rib 28C protruding radially inward over the entire circumference is formed at the lower end portion of the inner circumferential surface of the stepped portion 28B, and the entire circumference is formed at the lower end portion of the rotary shaft portion 31 fitted into the shaft hole 28A. It is configured to be engageable with an engagement groove 31B formed over the entire area.

  Further, the lower end portion of the cylindrical main body portion 28 protrudes from the outer peripheral surface to the outer side in the radial direction with respect to the center axis by a predetermined length, for example, a length of about 5 mm, with a width narrower than the diameter of the shaft hole 28A. A positioning arm 51 having a substantially rectangular parallelepiped shape that is long in the radial direction is provided. A positioning pin 51A having a predetermined height formed in a columnar shape, for example, a height of about 3 mm, is erected at the distal end of the positioning arm 51 so as to face the cylindrical main body 28 from the upper end surface. ing.

  In the lower case 6, a stepped portion 28B is fitted from above, and a cylindrical crank base mounting portion 53 for positioning the crank base 27 with respect to the distribution chamber mounting portion 38 is opposed to the partition wall 41. It is provided adjacent to the outside of the distribution chamber mounting portion 38. The height from the upper end surface of the crank base mounting portion 53 to the upper end surface of the distribution chamber mounting portion 38, that is, the upper end surfaces of the partition walls 39 and 41, is slightly lower than the thickness of the positioning arm portion 51 of the crank base 27. For example, the height is reduced by about 0.1 mm to 0.3 mm.

  In addition, at the edge of the partition wall 41 on the side of the crank base attaching portion 53, the crank base is attached from the upper end surface of the partition wall 41 along a straight line connecting the center of the crank base attaching portion 53 and the center of the screw hole 42. A positioning groove 55 that is recessed in a substantially U shape in plan view at a depth reaching the upper end surface of the portion 53 is formed. The positioning groove portion 55 is formed to have a width substantially equal to the width of the positioning arm portion 51 of the crank base 27. When the step portion 28B of the crank base 27 is fitted into the crank base mounting portion 53, the positioning arm portion 51 is moved upward. It is formed in a length that can be fitted over the entire length.

  Accordingly, when the stepped portion 28B of the crank base 27 is fitted into the crank base attaching portion 53 and the positioning arm portion 51 is fitted into the positioning groove portion 55 from above, the upper end surface of the positioning arm portion 51 is above the partition wall 41. It protrudes upward from the end surface by a predetermined height, for example, a height of about 0.1 mm to 0.3 mm. Further, when the stepped portion 28B of the crank base 27 is fitted into the crank base attaching portion 53 and the positioning arm portion 51 is fitted into the positioning groove portion 55 from the upper side, the distance between the centers of the positioning pin 51A and the screw hole 42 is as follows. The distribution recess 37 is formed so as to be substantially equal to the center-to-center distance between the positioning recess 49 and the through hole 48.

  Next, a mounting method for bonding and fixing the crank base 27 and the distribution chamber 37 thus configured to the distribution chamber mounting portion 38 will be described with reference to FIGS. As shown in FIGS. 1 to 3, first, both longitudinal ends of the bridge 47 are bonded and fixed to the respective steps 45 of the distribution chamber mounting portion 38. And the level | step-difference part 28B of the crank base 27 is inserted in the crank base attachment part 53, and the positioning arm part 51 is inserted in the positioning groove part 55 from the upper side. A sealant may be applied to the outer peripheral surface of the stepped portion 28B of the crank base 27.

  Subsequently, a sealant is applied to the upper surface of the distribution chamber mounting portion 38 and the bridge 47 or the bottom surface of the distribution chamber 37. Then, the positioning recess 49 formed in the bottom surface portion of the distribution chamber 37 is fitted into the positioning pin 51A of the crank table 27, and the distribution chamber 37 is placed on the distribution chamber mounting portion 38. Thereafter, the distribution chamber mounting screw 40 is fitted into the through hole 48 of the distribution chamber 37 from above, and is screwed into the screw hole 42 formed in the upper end surface of the partition wall 41 to be fixed.

  As a result, the distribution chamber 37 is positioned with respect to the crank base mounting portion 53 while being pressed against the distribution chamber mounting portion 38 via the distribution chamber mounting screw 40, and is adhesively fixed to the distribution chamber mounting portion 38. The Further, the crank base 27 is fixed to the crank base attaching portion 53 in a state where the upper end surface of the positioning arm portion 51 fitted in the positioning groove portion 55 is pressed by the bottom surface portion of the distribution chamber attaching portion 38.

  Next, as shown in FIGS. 1 to 3, a valve 57A having a substantially fan shape in plan view is placed on the upper side of the gas flow paths R1, R2 and the exhaust guide flow path T1 of the distribution chamber 37, and the gas flow paths R3. , R4 and a valve 57B having a substantially fan shape in plan view are placed on the upper side of the exhaust guide passage T2. Each valve 57A, 57B is formed of a hard synthetic resin such as a phenol resin. Then, each valve guide 59 in which a male screw is erected at the lower end portion of the cylindrical shaft portion is fitted into the mounting through hole 58 formed in the base end portion of each valve 57A, 57B, and the distribution chamber 37 Screw into each female screw fitting 61 (see FIG. 4) provided by insert molding in the vicinity of the bridge 47 side of each exhaust guide passage T1, T2. Thus, the valves 57A and 57B are provided on the distribution chamber 37 so as to be swingable.

  Further, one end portions of the two crank rods 62 are rotatably connected to the connecting shaft 33 of the crank member 25, respectively. The other end of one crank rod 62 is rotatably connected to a pin 63A provided upright on the upper end surface of the valve 57A. The other end of the other crank rod 62 is rotatably connected to a pin 63B provided upright on the upper end surface of the valve 57B.

  Then, when the pair of membrane portions 13 reciprocate once in the front-rear direction, each blade shaft 16 rotates at a predetermined angle, and the rotation shaft portion 31 can rotate in the shaft hole 28A of the crank table 27 along with the rotation. The inserted crank member 25 is rotated once by the link mechanism portion 21. As a result, the valves 57A and 57B connected to the crank member 25 via the crank rods 62 swing while sliding with respect to the distribution chamber 37, and the city gas that is the fluid to be measured with respect to each measuring chamber 15 is swung. Supply and discharge are controlled.

  As described above in detail, in the membrane gas meter 1 according to this embodiment, the stepped portion 28B of the crank base 27 is fitted into the crank base attaching portion 53 and the positioning arm portion 51 is fitted into the positioning groove portion 55, and then the distribution is performed. The chamber 37 is fixed to the distribution chamber mounting portion 38 with the distribution chamber mounting screw 40. As a result, the crank base 27 is fixed to the crank base attaching part 53 via the positioning arm part 51 pressed against the positioning groove part 55 by the distribution chamber 37, so that the female screw fitting for attaching the crank base 27 to the distribution chamber 37 is provided. Insert molding can be abolished.

  Further, the distribution chamber 37 may be fixed by the distribution chamber mounting screw 40 after the positioning arm portion 51 is inserted into the positioning groove portion 55 while the stepped portion 28B of the crank base 27 is inserted into the crank base mounting portion 53. The screwing operation for fixing the base 27 can be eliminated, and the assembly operation can be speeded up. Further, the positioning chamber 51 is quickly positioned with respect to the crank table 27 by fitting the positioning pin 51A erected on the top surface of the distal end of the positioning arm 51 into the positioning recess 49 formed on the bottom surface of the distribution chamber 37. This can be done and the assembly operation can be further speeded up with a simple configuration.

  The distribution chamber 37 is fixedly bonded to the distribution chamber mounting portion 38 in a state where the distribution chamber 37 is fixed to the distribution chamber mounting portion 38 by the distribution chamber mounting screw 40. Thereby, it is possible to prevent the distribution chamber 37 from being lifted by the distribution chamber mounting screw 40, and it is not necessary to hold the distribution chamber 37 from above until the sealant is hardened, and the assembly work can be speeded up. Further, since the cylindrical main body portion 28 of the crank base 27 is formed of a hard synthetic resin such as polyacetal, even if the bearing is abolished, the frictional force is reduced and the rotating shaft portion 31 of the crank member 25 is made smooth. Can be rotated.

  In addition, this invention is not limited to the said embodiment, Of course, various improvement and deformation | transformation are possible within the range which does not deviate from the summary of this invention. For example, the following may be used.

  For example, the outer shape of the cylindrical main body 28 of the crank base 27 may be a polygon such as a square cross section, a hexagon cross section, an ellipse, or the like. However, the shaft hole 28A has a circular cross section, and the rotation shaft portion 31 is rotatably fitted therein.

DESCRIPTION OF SYMBOLS 1 Membrane gas meter 3 Meter case 5 Upper case 6 Lower case 7 Inlet 8 Outlet 13 Membrane part 15 Measuring chamber 21 Link mechanism part 25 Crank member 27 Crank base 28 Cylindrical main body part 28B Step part 31 Rotating shaft part 37 Distribution room 38 Distribution chamber mounting portion 40 Distribution chamber mounting screw 48 Through hole 49 Positioning recess 51 Positioning arm portion 51A Positioning pin 53 Crank base mounting portion 55 Positioning groove portion

Claims (4)

An upper case forming an inlet of the fluid to be measured and an outlet of the fluid to be measured;
A lower case that forms a pair of measuring chambers defined by a membrane portion that reciprocates by the pressure of the fluid to be measured flowing into the upper case;
A distribution chamber that is attached to the distribution chamber mounting portion of the lower case and distributes the fluid to be measured flowing from the inflow port to the pair of measurement chambers;
A crank base that rotatably supports a crank member that converts a reciprocating motion of the film portion into a rotational motion via a link mechanism portion;
In a membrane gas meter equipped with
The crank stand is
A cylindrical main body portion in which a through hole having a circular cross section is formed in the axial direction and the rotation shaft portion of the crank member is rotatably fitted;
A stepped portion that is narrower than the cylindrical main body portion, which extends coaxially a predetermined length downward from the lower end of the cylindrical main body portion;
A positioning arm portion extending radially outward from the outer peripheral surface of the lower end portion of the cylindrical main body portion with respect to the central axis;
Have
The lower case is
A crank base mounting portion that is disposed adjacent to the lower side of the upper end surface of the distribution chamber mounting portion by a height substantially equal to the thickness of the positioning arm portion and into which the stepped portion is inserted;
The crank base having a depth from an upper end surface of the distribution chamber mounting portion to a portion adjacent to the upper end surface of the crank base mounting portion of the distribution chamber mounting portion, and a width substantially equal to the width of the positioning arm portion. A positioning groove that is recessed along the direction perpendicular to the central axis of the mounting portion and into which the positioning arm portion is fitted from above;
Have
The distribution chamber has a through hole into which a distribution chamber mounting screw for fixing the distribution chamber to the distribution chamber mounting portion is inserted.
The distribution chamber is fixed to the distribution chamber mounting portion via the distribution chamber mounting screw after the positioning arm portion is inserted into the positioning groove while the stepped portion of the crank base is inserted into the crank base mounting portion. Thus, the crank base is fixed to the crank base mounting portion in a state where the positioning arm portion is pressed against the positioning groove by the bottom surface of the distribution chamber. The crank base has a positioning pin erected on the upper surface of the distal end portion of the positioning arm portion,
The distribution chamber has a positioning recess into which the positioning pin is fitted in a bottom surface portion facing the positioning pin,
The membrane gas meter according to claim 1, wherein the distribution chamber is fixed to the distribution chamber mounting portion via the distribution chamber mounting screw in a state where the positioning pin is fitted in the positioning recess.   3. The distribution chamber according to claim 1, wherein the distribution chamber is adhesively fixed to the distribution chamber mounting portion in a state of being fixed to the distribution chamber mounting portion via the distribution chamber mounting screw. Membrane gas meter.   The membrane gas meter according to any one of claims 1 to 3, wherein the crank base is made of a synthetic resin containing polyacetal.

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