JP2000346683A - Fluidic gas meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a diaphragm from being deformed largely so as to be reversed to the side of a second space when a valve element in a pressure- change removal means is opened suddenly. SOLUTION: In the gas flow passage of a gas meter body, a pressure-change removal means 37 and a fluidic flowmeter are installed in this order along the passage direction of a gas. One end part 112 of a connecting rod 70 is attached, for as to be rockable, to a valve element 42 which can be seated on a valve seat 82, the other end part is connected to a diaphragm 43, and the diaphragm 43 brings the valve element 42 close to the valve seat 82 as the differential pressure between a pressure on the upstraem side from a valve 41 and a pressure on the side of a gas discharge port becomes small. A radial reverse prevention part 252 is formed at a support member 201 on one side which sandwiches the diaphragm 43. Thereby, it is possible to prevent the deformable part 253 of the diaphragm 43 from protruding to the side of a second space 46 so as to be reversed and deformed and a force in the valave closing direction can be always given to the valve element 42 by the diaphragm 43.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluidic gas meter.

[0002]

2. Description of the Related Art Fluidic gas meters have a fluidic flow meter.
It includes a fluidic element that generates an alternating pressure change by passing gas, and a flow meter that detects the frequency of a fluidic oscillation alternating pressure wave due to the alternating pressure change and calculates a gas flow rate from this frequency. When the supplied gas contains noise of pressure fluctuation, particularly at a small flow rate, it adversely affects the fluidic oscillation of the fluidic element, and when the pressure fluctuation approximates the frequency of the fluidic oscillation, the gas flow rate is correct. Measurement becomes impossible. In order to solve this problem, a pressure fluctuation removing means is arranged upstream of the fluidic flow meter in the gas passage direction, the flow path resistance is increased at a small flow rate, and the pressure fluctuation noise of the gas is reduced by the fluidic flow meter. To be transmitted to the user.

FIG. 22 shows a prior art pressure fluctuation removing means 3.
It is sectional drawing which shows 37. Connecting rod 37 having a horizontal axis
A valve body 342 is attached to one end of the zero, and a throttle opening is obtained by an interval between the valve body 342 and the valve seat 382. A large pressure loss is generated at a small flow rate, and the pressure loss is reduced at a large flow rate. A diaphragm 343 is fixed to the other end of the connecting rod 370 in order to drive such a valve body 342 for displacement. The diaphragm 343 closes the valve body 342 in the valve closing direction (see FIG. 22) by a differential pressure between the first space 345 and the second space 346 communicating with the space downstream of the valve body 342 via the throttle hole 360. (Right). First space 34
5 communicates with the gas outlet. A force in the valve opening direction (leftward in FIG. 22) acts on the valve body 342 due to the differential pressure across the valve body 342. The degree of opening between the valve body 342 and the valve seat 382 is determined by the balance between the force of the diaphragm 343 and the force exerted by the pressure difference between the front and rear of the valve body 342, so that a large pressure loss at a small flow rate can be obtained. Pressure loss at the time of a large flow rate can be reduced.

[0004] In the prior art shown in FIG.
The central support portion 3 is sandwiched by a pair of rigid disk-shaped support members 375a and 375b having the same shape, and the peripheral edge of the diaphragm 343 is fixed to the holding body 344. The diaphragm 343 is connected to the connecting rod 3 in the valve closing direction.
In the normal state of exerting a force on 70, the diaphragm 343 bulges in an arc as indicated by reference numeral 371. When the flow rate of the gas is increased and the valve is rapidly opened, the first and second spaces 3 added to the diaphragm 343 are increased.
Regardless of the pressure difference of 45, 346, the connecting rod 370, the support members 375a, 37
5b and the folds 37 of the diaphragm 343
1, and the valve body 342 comes into contact with the contact piece 396 to be fully opened as shown in FIG.

[0005] The pressure of the gas on the valve body 342 side is, for example, in the fully opened state shown in FIG.
It communicates with the second space 346 via 69. This aperture 36
By the operation of 9, the pressure fluctuation noise of the gas supply port is not transmitted to the second space 346, thereby preventing the diaphragm 343 from vibrating finely and achieving a stable pressure loss by the valve body 342. it can.

Since the second space 346 communicates with the gas supply port through the throttle hole 369, it is a so-called semi-closed space. Therefore, the volume of the second space 346 increases by the amount by which the support members 375a and 375b together with the valve body 342 suddenly move to the left in FIG. 22, and the pressure in the second space 346 decreases accordingly. As a result, the portion 371 of the diaphragm 343 is deformed in a normal state,
As shown by reference numeral 372, the valve body 342 side (FIG. 22)
(To the right) of at least partially protruding and deformed into an inverted shape. When the diaphragm 343 is deformed into the shape of the reference numeral 372, it does not automatically return to the arc shape 371 again, and the inverted shape 372 is maintained. As a result, the force in the valve closing direction by the diaphragm 343 does not act on the connecting rod 370 and the valve body 342. As a result, the valve body 342 is kept in the fully open state, and the original function of the pressure fluctuation removing means cannot be achieved.

In order to solve this problem, a throttle hole 369 is provided.
Instead, it may be easily considered that a relatively large communication hole is formed as shown by reference numeral 373 to connect the second space 346 to the space on the valve body 342 side. In such a configuration, the pressure fluctuation noise of the gas supplied from the gas supply port is transmitted to the second space 346 as it is,
As described above, the diaphragm 343 generates minute vibration, and it is difficult to obtain a stable and large pressure loss at a small flow rate.

A large number of fluidic gas meters are provided.
Since it is used, it is desired that mass production is easy, productivity is improved, and it is realized at low cost.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to make it possible to always apply a stable force in a valve closing direction to a valve body of a pressure fluctuation removing means by means of a diaphragm. It is to provide a fluidic type gas meter capable of performing such operations.

[0010]

According to the present invention, there is provided a gas meter main body having a gas flow path communicating with a gas supply port and a gas discharge port, and (b) a gas meter body interposed in the gas flow path,
A fluidic flow meter that measures the gas flow rate based on an alternating pressure change generated by the passage of gas; and (c) a gas flow path that is interposed upstream of the fluidic flow meter in the gas passage direction and absorbs pressure fluctuations. (C1) a holder having a valve seat communicating with the gas supply port and having a laterally extending valve hole facing the downstream side in the gas passage direction; and (c2) inserting the valve hole into the valve hole. A removable valve element, and (c)
3) a diaphragm that divides the diaphragm chamber of the gas meter main body into a first space communicating with the gas outlet side of the gas flow path and a second space communicating with the gas supply port of the gas flow path;
4) a connecting rod having one end through which the valve element is inserted and the other end through which the diaphragm is inserted; (c5)
(C6) a holding means disposed at the other end and holding the diaphragm between the pair of support members 201 and 202 and fixing the diaphragm to the other end; (C7) the diaphragm bulges in a convex arc shape on the opposite side to the valve body, and
8) One support member 201 on the valve body side extends outward in the direction perpendicular to the axis of the connecting rod more than the other support member on the side opposite to the valve body with respect to the diaphragm, and the diaphragm is displaced toward the valve body. Inversion prevention unit 2 for preventing inversion
(C9) The valve body is opened and closed by a force that presses the diaphragm due to the differential pressure between the first and second spaces and a force that presses the valve body due to the differential pressure across the valve body, and as the maximum flow rate is approached. And a pressure fluctuation removing means for largely separating the valve body from the valve seat.

According to the present invention, the pressure fluctuation removing means and the fluidic flow meter are arranged in this order in the gas flow path of the gas meter main body along the gas passage direction. In order to open and close the laterally extending valve hole formed in the valve body, the valve body is driven in the horizontal direction, for example, in the horizontal direction by the diaphragm, the pressure on the upstream side in the gas passage direction from the valve hole, the pressure on the gas discharge port side, and As the differential pressure increases, the valve element is separated from the valve seat. Conversely, when the differential pressure is small and the flow rate is small, the valve element approaches or sits on the valve seat, and the pressure loss increases.

When the flow rate of the gas is small, an increase in pressure loss caused by the pressure fluctuation removing means prevents adverse effects on the fluidic oscillation of the fluidic element due to the pressure fluctuation noise of the gas whose flow rate is to be measured. .

In particular, according to the present invention, the diaphragm is perpendicular to the axis from the central support portion of the one support member so that the diaphragm always keeps a convexly convex shape on the opposite side to the valve body. An inversion prevention portion extending outward in the direction is formed, thereby preventing the diaphragm from projecting to the second space side and preventing the diaphragm from being inverted. When the valve element is separated from the valve seat at the time of a sudden large flow and is in an open state, the pressure in the second space is reduced by a throttle means such as a throttle hole,
Although the flexible portion of the diaphragm tends to protrude and deform toward the second space, such a reverse deformation of the diaphragm is prevented by the reverse prevention portion. Therefore, by the elastic force of the diaphragm, it is possible to swell to the original arc shape and to automatically return. As a result, the diaphragm can always exert a force in the valve closing direction. The throttle means prevents the pressure fluctuation noise of the gas from the gas supply port from being transmitted to the second space,
It functions to stably generate a large pressure loss due to the valve element at a small flow rate.

Further, the present invention is characterized in that the inversion preventing portions are formed at intervals in the circumferential direction.

According to the present invention, a plurality of the inversion prevention portions may be formed, for example, radially at intervals in the circumferential direction as shown in FIG. 8, or the number of the inversion prevention portions may be a single, thereby connecting. The weight of the movable member that moves together with the rod and the valve body can be reduced, and the responsiveness due to the differential pressure between the first and second spaces acting on the diaphragm can be improved.

Further, according to the present invention, the thickness t
1 is a thickness t2 of the central support portion 251 closer to the axis of the connecting rod than the inversion prevention portion 252 of the one support member 201.
It is characterized in that it is selected smaller than that of.

According to the present invention, the thickness t1 of the inversion prevention portion is provided.
Is selected to be less than the thickness t2 of the central support portion, that is, by making the inversion prevention portion thinner, it is possible to further reduce the weight.

Further, the present invention is characterized in that the surface 252a on the diaphragm side of the inversion prevention portion is provided so as to be displaced from the surface 251a on the diaphragm side of the central support portion 251 in a direction away from the diaphragm. .

According to the present invention, the surface of the one support member on the diaphragm side of the reversal prevention portion is moved away from the diaphragm with respect to the surface of the central support portion, that is, closer to the valve body (see FIGS. 5 and 10). (To the right) in the axial direction. A central portion of the diaphragm is connected to the other end of the connecting rod between the central support portion of the one support member and the other support member. The deformable portion having flexibility and elasticity outside the central portion of the diaphragm can be smoothly deformed according to the pressure difference between the first and second spaces.

Further, according to the present invention, the pressure fluctuation removing means has a magnetic attraction force generating means for generating a magnetic attraction force in a direction in which the valve element approaches the valve seat when the flow rate is small by the valve element and the valve seat. The magnetic attraction force generating means has an annular permanent magnet piece and an annular attraction piece made of a ferromagnetic material and exerting a magnetic attraction with the permanent magnet piece, and one of the permanent magnet piece and the attraction piece is , Fixed to the valve body coaxially, one of the permanent magnet piece or the suction piece is provided in the gas meter body,
When the variation in the holding force of the permanent magnet piece is set to less than ± 8%, the pressure loss is reduced by one by exerting the magnetic attraction force between the permanent magnet piece and the suction piece at a small flow rate by the valve body and the valve seat.
The pressure is generated within the range of 50 to 200 Pa. The diaphragm is given a force for pushing the diaphragm due to the differential pressure between the first and second spaces, a force for pushing the valve body due to the differential pressure across the valve body, and magnetic attraction force generating means. And a magnetic attraction force that acts.

Further, the present invention provides (a) a gas meter main body in which a gas flow path communicating with a gas supply port and a gas discharge port is formed, and (b) an alternating gas generated through the passage of the gas which is interposed in the gas flow path. A fluid flow meter for measuring the gas flow rate based on the pressure change; and (c) a pressure fluctuation removing means interposed in the gas flow path on the upstream side of the fluid flow direction in the gas flow direction and absorbing the pressure fluctuation. So,
(C1) a holder having a valve seat that communicates with the gas supply port and has a valve hole that extends laterally and faces the downstream side in the gas passage direction;
(C2) a valve element that moves close to and away from the valve seat; and (c3) magnetic attraction force generating means that generates magnetic attraction force in a direction in which the valve element approaches the valve seat when the flow rate is small due to the valve element and the valve seat. hand,
(C3-1) an annular permanent magnet piece, and (c3-2) an annular attracting piece made of a ferromagnetic material and exhibiting a magnetic attractive force together with the permanent magnet piece. Or one of the suction pieces is fixed coaxially to the valve body,
(C3-4) Either the permanent magnet piece or the attraction piece is provided in the gas meter main body, and (c3-5) the dispersion of the holding force of the permanent magnet piece is set to less than ± 8%, and (c3-4)
6) magnetic attraction force generating means for generating a pressure loss within a range of 150 to 200 Pa by exerting the magnetic attraction force of the permanent magnet piece and the attraction piece at a small flow rate by the valve body and the valve seat; (C4) The diaphragm chamber is connected to the valve body and partitions the diaphragm chamber into a first space communicating with the gas discharge port side of the gas flow path and a second space communicating with the gas supply port of the gas flow path. The valve body is opened and closed by a force that presses the diaphragm due to the pressure difference between the two spaces, a force that presses the valve body due to the pressure difference between the front and rear of the valve body, and a magnetic attraction force that is provided by the magnetic attraction force generating means. And a diaphragm for largely separating the valve body from the valve seat.

Further, the present invention is characterized in that the variation in the holding force of the permanent magnet pieces is less than ± 5%.

According to the present invention, the magnetic attraction force generating means provided in the pressure fluctuation removing means includes a permanent magnet piece and a suction piece, and one of the permanent magnet piece and the suction piece is coaxial with the valve body. Fixed, the other is provided in the gas meter body, the magnetic attraction force by the permanent magnet piece and the attraction piece,
Acting on the diaphragm, at a small flow rate, when the differential pressure between the upstream side and the downstream side of the valve body in the gas flow direction is small, a magnetic attraction force acts on the valve body in a direction approaching the valve seat. As a result, a large pressure loss can be obtained at a small flow rate, so that external gas pressure fluctuation noise at a small flow rate can be removed, and the accuracy of the gas flow rate by the fluidic flow meter can be improved.

In particular, according to the present invention, the variation in the holding force of the permanent magnet pieces is selected to be less than ± 8%, preferably less than ± 5%, and more preferably less than ± 3%. Thus, there is no need to prepare an expensive permanent magnet piece having a small variation in holding force, and the fluidic gas meter of the present invention can be realized at low cost. In this way, the pressure loss caused by the pressure fluctuation removing means at the time of a small flow rate is set to 1
The pressure can be set within 50 to 200 Pa.

Further, the present invention is characterized in that the permanent magnet pieces are made of ferrite. According to the present invention, the permanent magnet piece is made of ferrite, so that a small and large holding force can be obtained. Therefore, in particular, in a configuration in which the permanent magnet piece is fixed to the valve element, and thus to the diaphragm, it is possible to reduce the weight of the movable part including such a valve element, the diaphragm and the connecting rod, and to obtain an accurate pressure loss corresponding to the flow rate. Will be sure to get.

In the present invention, the suction piece is annular, and has a thickness of 0.8 to 1.2 mm, an inner diameter of 10 to 14 mm, and an outer diameter of 18 mm.
２１21 mmφ.

According to the present invention, the suction piece has an outer diameter of 20 to 21.
mmφ. According to the present invention, when the suction piece is an annular flat plate and its thickness is selected to be 0.8 to 1.2 mm, burrs occur when the ferromagnetic material plate such as iron is manufactured by punching and forging using a die. Therefore, a suction piece having an accurate size and shape can be easily manufactured, and productivity is improved.

According to the present invention, the inner diameter Di of the suction piece is selected to be 10 to 14 mmφ, and the outer diameter Dj is set to 18 to 21 mmφ.
By selecting the outer diameter to be preferably 20 to 21 mmφ, the pressure loss of the pressure fluctuation removing means at the time of a small flow rate can be reduced to a desired value, for example, 160 mm as described with reference to FIGS. To 200 Pa, preferably 180 to 200 Pa. Thus, pressure loss at a small flow rate can be accurately obtained, and it is ensured that external gas pressure fluctuation noise is suppressed.

Further, the present invention is characterized in that the suction piece is formed by stacking a plurality of individual suction pieces having the same size in the axial direction of the valve element.

According to the present invention, a plurality of individual attraction pieces can be overlapped in the axial direction and used as the attraction piece, thereby easily adjusting the magnetic attraction force between the permanent magnet piece and the attraction piece. Can be.

Further, the present invention is characterized in that the permanent magnet piece is fixed to the gas meter main body, and the suction piece is fixed to the valve body.

According to the present invention, the permanent magnet piece is fixed to the gas meter main body, and the suction piece is fixed to the valve body, that is, the diaphragm, so that the suction piece can be made relatively small. The movable part including the valve body, the diaphragm and the connecting rod is made small, and a relatively large pressure loss at a small flow rate can be accurately and easily obtained.

The present invention also relates to a method for assembling the above-mentioned fluidic gas meter, wherein a first permanent magnet piece having a first variation value and a second variation less than the first variation value are provided. And a second permanent magnet piece having the following values is prepared, assembled using the first permanent magnet piece, and a pressure loss at a small flow rate is measured. The measured pressure loss is out of a predetermined range. Sometimes, instead of the first permanent magnet piece, the second
The method of assembling a fluidic gas meter, wherein the assembling is performed by replacing and using the permanent magnet pieces.

According to the fluidic gas meter assembling method of the present invention, the holding force has a first variation value, for example, a value less than ± 8%, or a value in a range of ± 5 ± 8%, The holding force of the second permanent magnet piece has a value of the second variation, and the value of the second variation is less than the value of the first variation, for example, less than ± 3%. At the time of assembling the fluidic gas meter, the fluidic gas meter is once assembled using the first permanent magnet piece having a large variation, and the pressure loss at a small flow rate is measured. When the pressure loss is outside the predetermined range, that is, when the pressure loss is a large value that exceeds the predetermined range, or when the pressure loss is below the predetermined range and is a small value, the assembled fluidic gas meter is disassembled and the first gas meter is disassembled. Instead of the permanent magnet piece, a second permanent magnet piece having a small variation in holding force is replaced and used. Thereby, the pressure loss of the fluidic gas meter using the second permanent magnet piece can be kept within the predetermined range.

The first permanent magnet piece has a relatively large variation in holding force, and therefore can be manufactured at low cost. A fluid gas meter can be manufactured at low cost by using such an inexpensive first permanent magnet piece. Can be manufactured. Due to the variation of the instrumental difference of the fluidic gas meter, the pressure loss in the configuration using the first permanent magnet piece may be out of the predetermined range relatively infrequently.
In such a case, a second permanent magnet piece having a smaller variation value is used. Therefore, the pressure loss in the pressure fluctuation removing means of the fluidic gas meter using the second permanent magnet piece can be kept within the predetermined range. Thus, an inexpensive fluidic gas meter can be easily obtained in mass production.

[0036]

FIG. 1 is a longitudinal sectional view of a pressure fluctuation removing means 37 included in a fluidic gas meter 31 according to one embodiment of the present invention, and FIG. 2 is a pressure fluctuation removing means shown in FIG. It is a longitudinal cross-sectional view which shows the whole structure of the fluidic gas meter 31 provided with the means 37. The fluidic gas meter 31 has a gas supply port 32 and a gas discharge port 33, and a gas meter body 35 in which a gas flow path 34 communicating between the gas supply port 32 and the gas discharge port 33 is formed. A fluidic flow meter (measuring means) 36 which is interposed in the passage 34 and measures a gas flow rate based on an alternating pressure change generated by the passage of the gas; and a gas flow direction upstream of the fluidic flow meter 36 in the gas passage direction. A pressure fluctuation removing means 37 interposed in the flow path 34 for absorbing pressure fluctuation transmitted from the upstream pipe, and a fluid sensor 36 between the fluidic flow meter 36 and the pressure fluctuation removing means 37 in the gas flow path 34, for example. A shut-off valve 38 for shutting off the gas flow path 34 when abnormalities such as earthquakes, excessive flow rates, under-flow rates, and temperature rises detected by the Etc. 8 and various sensors described below and a battery for supplying driving power.

The pressure fluctuation removing means 37 opens the valve hole 41 when the pressure difference between the pressure P1 on the gas supply port 32 side and the pressure P3 on the gas discharge port 33 side of the gas passage 34 increases.
And a valve element 42 for closing the valve hole 41 when the pressure difference between the pressure P1 on the gas supply port 32 side and the pressure P3 on the gas discharge port 33 side of the gas flow path 34 is reduced. And a diaphragm 43 made of a resilient material such as rubber and the like. The diaphragm 43 partitions the diaphragm chamber 44 into a first space 45 communicating with the gas discharge port 33 of the gas flow path 34 and a second space 46 communicating with the gas supply port 32 of the gas flow path 34, The pressure P1 in the second space 46 and the pressure P3 in the first space 45
The valve element 42 is opened and closed by the displacement of the diaphragm 43 due to the pressure difference (P1-P3). Valve chamber 6 described later
7, a passage 58, a valve chamber 59, a valve hole 60, and a passage 61.
The gas that has passed through becomes the pressure P2 in the passage 62, and the pressure P3 in the first space 45 is the same pressure as the pressure on the gas outlet 33 side after passing through the fluidic element 50 described later.

The valve body 42 and the diaphragm 43
The operation direction is horizontal with respect to the predetermined arrangement state of the gas meter main body 35, that is, the arrangement state in which the upper part 47 is vertically upward and the lower part 48 is vertically downward and the gas supply port 32 and the gas discharge port 33 face downward. It is provided so that The first space 45 is provided with the pressure introduction passage 4 in the gas outlet 33.
9 and thus the gas outlet 33 and the first space 45 are at the same pressure. On the front side of the gas meter main body 35 shown in FIG. 2, a vibration detecting sensor 51 for detecting an alternating pressure change due to fluidic oscillation generated by the fluidic element 50 is provided. 51 and the fluid flow meter 36 is constituted. Although the fluidic flow meter 36 can measure a flow rate of 150 L / h or more, it cannot detect a small flow rate of less than 150 L / h. A flow sensor 52 capable of measuring a flow rate in a range of up to 250 L / h is provided.

The gas meter body 35 has a gas supply port 32
Storage space 57, passage 58, valve body 6 of shut-off valve 38 in which pressure fluctuation removing means 37 is fitted and stored in close proximity to
The valve chamber 59, the valve hole 60, the passage 61, and the passage 6 in which
The second storage space 63 in which the second and fluidic elements 50 are stored is formed in this order, and forms the gas flow path 34.

The pressure fluctuation removing means 37 communicates with the passage 58 which constitutes a part of the gas flow path 34, and has a valve chamber 67 in which the valve element 42 is stored and a diaphragm chamber 44 in which the diaphragm 43 is stored. A partition 68 that separates the valve chamber 67 and the diaphragm chamber 4 from each other.
4 and a throttle hole 69 which is a through hole for limiting the operation speed of the diaphragm 43 is formed. The valve body 42 and the diaphragm 43 are coaxially connected by a connecting rod 70 serving as a valve rod, and a sleeve 71 through which the connecting rod 70 is displaceably inserted along the axis thereof is integrally formed on the partition wall 68. In the sleeve 71, a sliding thrust bearing 72 made of a straight cylindrical metal having good slipperiness, for example, a material such as brass or iron galvanized on the surface, or a synthetic resin, is housed. It is movably held in the axial direction in a close state.

The peripheral edge of the diaphragm 43 is
8 is hermetically fitted and held on a peripheral wall 84 of a bottomed cylindrical first holding member 83 having a bottom portion 8. The peripheral wall 84 has a large-diameter portion 85a into which the peripheral portion of the diaphragm 43 fits, and a small-diameter portion 85b coaxially connected to the large-diameter portion 85a and integrally forming the partition wall 68. One end in the axial direction of the substantially cylindrical second holding body 86 fits on the outer peripheral surface of the small diameter portion 85b. The second holder 86 has a valve chamber 67.
And a gas outlet hole 8 communicating with a passage 58 which is a gas flow path downstream of the pressure fluctuation removing means 37 in the gas passage direction.
7 is formed. The first holder 83 and the second holder 86
Thus, a cylindrical body 89 is formed.

A radial hole 90 is formed near the other end in the axial direction of the second holding body 86, and an annular recess into which an O-ring 92 is fitted is formed between the radial hole 90 and each of the gas outlet holes 87. Groove 9
3 is formed. The O-ring 92 is provided with the pressure fluctuation removing unit 3.
7 is mounted in the first storage space 57 of the gas meter main body 35 and resiliently contacts the inner peripheral surface defining the first storage space 57 over the entire circumference in the circumferential direction, thereby achieving airtightness and gas leakage. Can be prevented.

The partition wall 68 also has an annular, substantially right cylindrical shape that surrounds a part of the connecting rod 70 projecting into the valve chamber 67, a part of the sleeve 71, and a part of the bearing 72. The contact piece 96 is formed integrally. The outer diameter of the contact piece 96 is selected to be about １ ／ of the outer diameter of the valve element 42, and the valve element 42 in the fully opened state can be stably supported on the valve chamber 67 side. At the end of such a contact piece 96, a notch 97 is formed in which a part in the circumferential direction is cut. Even when the valve element 42 is in contact with and supported by the contact piece 96 in the fully opened state by the notch 97, the valve chamber 67 and the contact piece 96
The internal space surrounded by the valve chamber 67
And the second space 46 can be communicated through the through hole 69.

One end 112 in the axial direction, which is arranged on the valve chamber 67 side of the connecting rod 70, is connected through the valve body 42.

FIG. 3 is a sectional view of the valve element 42. Valve body 4
2 is a bottomed cylindrical body 13 that can be inserted into and removed from the valve hole 41 of the holding body 86.
1 and an annular projection 132 provided on the cylindrical body 131. The cylindrical body 131 includes a disk-shaped bottom 133 and a cylindrical portion 13.
And 4. The outer shape of the cylindrical portion 134 is a straight cylindrical shape.
Contact surface 135 of annular convex portion 132 that can contact valve seat 82
Is perpendicular to the axis of the valve element 42.

The inner diameter Wv of the valve hole 41 and the cylindrical body 1 of the valve body 42
According to an experiment conducted by the inventor of the present invention, the gap d1 between the outer diameter Wp of the cylindrical portion 134 and the cylindrical portion 131 is selected to be, for example, d1 = 0.7 mm. Considering 0.1 mm, for example, d1 = 0.7 ±
0.2 mm is selected. Wp = Wv-d1 (1)

The length Tp of the cylindrical body 131 is 3.0 to 4.0.
mm, and the length Tv of the valve hole 41 is 3.0 to 4.0.
mm and thus the length Tp of the cylinder and the length T of the valve hole
v is chosen to be approximately equal. The lengths Tp and Tv are
Preferably, it is selected to be 3.5 mm. Furthermore, in the experiment of the present inventor, the inner diameter Wv of the valve hole 41 is, for example, 41.0 to 41.0.
41.5 mm. This inner diameter Wv is fixed, and the outer diameter Wp, and therefore the value of (Wv-Wp), and the lengths Tp, Tp
Optimize each value of v. As the outer diameter Wp of the cylindrical body 131 is selected to be small, when the gas flow rate is small, the valve body 42
Can be moved in the fully open direction. Cylinder 1
When the length Tp of 31 is small, for example, 1 mm,
The pressure loss gradually decreases, and the pressure loss can be sufficiently reduced. By increasing the length Tp to 3 mm, the slope of the pressure loss can be made steeper, and the pressure loss in the large flow rate region becomes relatively small.

The length Tv of the valve hole 41 is set to the above-mentioned 2-3 mm.
If the length Tp of the cylinder 131 is not zero, the outer peripheral surface of the cylinder 131 and the valve hole 41 are shorter or longer.
The gap d1 with the inner peripheral surface of the valve body 42 remains unchanged until the cylinder 131 of the valve body 42 overlaps the valve seat 82 in the axial direction to the left in FIG. Therefore, the flow rate Q of the pressure loss
Can be changed by these lengths Tp and Tv. For example, the length Tv of the valve hole 41
May be selected to be, for example, 1 to 5 mm.

The outer diameter Dw of the annular projection 132 is 44 mm, and the length L1 of the annular projection 132 is 3 mm. Further, the inner diameter D1 of the insertion hole 141 of the valve body 42 is 3.25 mm. Further, the length L2 of the insertion hole 141 formed by the mounting cylinder 142 is 9.0 mm.

The valve body 42 abuts on a step 116 which is a receiving portion of the one end 112 of the connecting rod 70, and the valve body 42 is
Can be pressed to sit on.

The peripheral portion 143 corresponding to the valve hole 41 of the cylindrical body 131 of the valve body 42 has an arc shape tapering toward the valve hole 41. In this embodiment, an arc shape of about a quadrant is used. And the radius Rp is 1.5 to 2.5 mm, preferably 2.0 mm. Further, the inner peripheral surface 144 of the valve hole 41 that continues to the valve seat 82 has an inner diameter that increases as the position approaches the valve seat 82, that is, toward the left in FIG. 3.
The inner peripheral surface 144 has an arc shape of about a half circle, and has a radius Rp1 = 0.5 mm.

FIG. 4 is a perspective view of a part near the one end 112 of the connecting rod 70. The outer peripheral surface of the one end portion 112 has a uniform cross section in the axial direction (the left-right direction in FIG. 4). For example, the one end portion 112 has a straight cylindrical shape in this embodiment, and a straight cylindrical shape in another embodiment. The shape may be a prism, a prism, or the like. The one end portion 112 has a smaller diameter than the connecting rod main body 111, thereby forming the above-described step 116.

Referring to FIG. 3 again, the cylindrical body 131 has mounting cylindrical parts 142a, 142 extending on both axial sides of the bottom 133.
42b (sometimes collectively indicated by reference numeral 142) is formed. The mounting cylinder portion 142a is formed so as to protrude from the cylinder body 131 toward the diaphragm 43 (to the left in FIG. 10). The mounting cylinder portion indicated by reference numeral 142b protrudes on the opposite side (to the right in FIG. 3) from the diaphragm 43. The mounting cylinder 142 projects from the bottom 133 of the cylinder 131 toward the valve hole 41 from the bottom 133 of the cylinder. This mounting cylinder 1
The outer diameter of 42b increases as it approaches the bottom 133 of the cylindrical body 131, and the radius R5 shown in FIG. 3 may be, for example, 5 to 8 mm to prevent gas turbulence. The peripheral portion 143 of the bottom 133 of the cylindrical body 131 is formed in an arc shape, and more preferably, the inner peripheral surface 144 of the valve seat 82 is formed in an arc shape.
Further, when the valve body 41 is displaced inward in the axial direction of the valve hole 41 (to the right in FIG. 3), the valve body 42 is smoothly guided by the valve hole 41, and the abutment surface 135 is accurately seated on the valve seat 82. it can.

Insertion hole 1 for mounting cylinders 142a, 142b
The difference ΔD (= D1−D1) between the inner diameter D1 of the connecting rod 41 and the outer diameter D3 of the one end 112 of the connecting rod 70 inserted through the insertion hole 141.
D3) is about 0.05 to 0.05 when the standard value is 0.25 mm and the dimensional tolerance required for manufacturing is ± 0.1 mm.
Choose 0.45 mm. Using the difference ΔD as a standard value,
By selecting 0.25 mm, connecting rod 70 and valve body 4
2, and in other embodiments of the invention, the difference ΔD may be selected to be between 0.25 and 0.45 mm.

The center of gravity G of the valve element 42 is located within the mounting cylinder 142 on the axis of the mounting cylinder 142. Therefore, in a state where one end of the connecting rod 70 is inserted through the cylinder 131 of the valve element 42, the axis of the connecting rod 70 and the axis of the valve element 42 match, and the bottom of the connecting rod 70 and the cylindrical body 131 of the valve element 42. 133
Means that a substantially vertical state is maintained and the valve body 4
2 is attached to one end 112 of the connecting rod 70 in a stable posture, the bottom 133 of the cylinder 131 of the valve body 42 is kept perpendicular to the axis of the connecting rod 70, and the bottom 133 is connected to the connecting rod 70. It can be prevented from being supported at an angle other than perpendicular to the 70 axis. Therefore, the bottom 133 of the cylindrical body 131 can be accurately seated on the valve seat 82,
Or it can be very close to the valve seat 82. Therefore, when the opening of the valve is small in a small flow rate range, an accurate pressure loss can be obtained, thereby eliminating the pressure fluctuation noise of the gas whose flow rate is to be measured, and using the fluidic flow meter 36 to measure the gas pressure. The flow rate can be measured accurately.

In particular, in the embodiment of FIG.
42 a and 142 b are formed to protrude from the bottom 133 of the cylindrical body 131 on both axial sides of the valve body 42. Therefore, the mounting cylinder portions 142a and 142b are
1 is formed to protrude from both sides in the axial direction from the bottom 133,
That is, the projection extends toward the inside of the valve hole 41 in the axial direction (to the right in FIG. 3) facing the valve seat 82, and also extends to the side of the diaphragm (to the left in FIG. 3). In this way, the center of gravity G of the valve body 42 can be accurately located on the axis of the mounting cylinder 142.

The mounting cylinder 142 of the valve element 42 is attached to the step 116.
In the state where the end face of a is in contact as shown in FIG.
One end 112 of the connecting rod 70 is attached to the mounting cylinder 1 of the valve body 42.
42b to the side opposite to diaphragm 43 (right side in FIG. 3)
At a predetermined length Yj. This length Yj is
According to the experiment of the present inventor, it is 4 to 6 mm. The connecting rod 70 has a substantially horizontal axis, and the gas pressure on the gas supply port 32 side in FIG. 3 is higher than the pressure of the gas in the valve chamber 67, so that the valve body 42 exerts a leftward force in FIG. Due to frictional resistance between the inner peripheral surface of the insertion hole 141 of the valve body 42 and the outer peripheral surface of the one end portion 112, etc.
The valve body 42 is not largely displaced rightward in FIG. 3 on the gas supply port 32 side. By setting the length Yj to an appropriate value as described above, the valve element 42 is connected to the one end 11.
2 can be prevented more reliably.
If the length Yj is less than 4 mm, the valve body may be detached from the one end, and if it exceeds 6 mm, the weight of the connecting rod increases and the movement of the connecting rod is not smooth, and the length Yj Need not be set longer than 6 mm.

FIG. 5 is an enlarged sectional view showing a structure for fixing the diaphragm 43 to the other end 76 of the connecting rod 70. The connecting rod 70 is closer to the valve body than the other end 76 (rightward in FIG. 5).
A support flange 201, which is one of the support members, is formed. The support flange 201 is formed in a disk shape centering on the axis of the connecting rod main body 111 of the connecting rod 70, and an end face facing the diaphragm 43 is perpendicular to the axis of the connecting rod 70.

An insertion hole 203 is formed in the annular flat holding member 202 which is the other support member, and the other end 76 of the connecting rod 70 is inserted. The support member 202 is located on the opposite side of the support flange 201 (left side in FIG. 5).
3. A mounting member 78 containing a permanent magnet piece 77 is fixed to the other end 76 of the connecting rod 70. The connecting rod 70, the holding member 202, and the mounting member 78 are made of Duracon resin, ABS resin or other synthetic resin material, are manufactured by injection molding, and in another embodiment of the present invention, other materials that are non-magnetic. Or it may be made of a non-magnetic metal material such as aluminum.

The second space 4 of the sleeve 71 shown in FIG.
An annular spacer 73 made of a non-magnetic material and an annular suction piece 7 made of a ferromagnetic material such as iron
4 is fitted. The suction piece 74 and the permanent magnet piece 77
The magnetic attraction means 81 is constituted. With such a magnetic attraction means 81, even when the valve element 42 tries to open due to pressure fluctuation due to disturbance or the like while the valve element 42 is seated on the valve seat 82 surrounding the valve hole 41, the valve element 42 is seated on the valve seat 82. The state can be maintained, whereby the pressure fluctuation can be attenuated, and the accuracy of measurement by the fluidic flow meter 36 is prevented from lowering.

The supporting flange 201 has a diaphragm 4
3 are formed. An O-ring is fitted into the annular concave grooves 205 and 206 and resiliently comes into contact with the end face of the diaphragm 43 to achieve airtightness. Further, the supporting member 202 is also formed with annular concave grooves 207 and 208 in the same manner, and an O-ring is fitted therein, thereby achieving airtightness. In this way, the airtightness of the first and second spaces 45 and 46 on both sides of the diaphragm 43 is reliably achieved, and the displacement of the diaphragm 43 due to pressure fluctuation is accurately realized.

FIG. 6 is a front view of the mounting member 70 as viewed from the left in FIG. 5, and FIG. 7 is a sectional view of the mounting member 78. The attachment member 78 has an insertion hole 209 through which the end 76 of the connecting rod 70 is inserted. This insertion hole 209
Inside, projections 211 which are elongated in the axial direction of the attachment member 78 (perpendicular to the paper surface of FIG. 6 and vertical in FIG. 7) are formed at equal intervals in the circumferential direction. In this embodiment, a total of three protrusions 211 are formed at 120 degrees apart in the circumferential direction. The attachment member 78 has an inner cylinder 212, an outer cylinder 213, and an end 214, and has a storage hole 215 for storing the permanent magnet piece 77. Storage hole 215
Is opened facing the holding member 202 and is formed in an annular shape concentric with the axis of the connecting rod 70. The permanent magnet piece 77 is stored in the storage hole 215 as described above. In another embodiment of the present invention, the attraction piece 74 may also be a permanent magnet piece that generates a magnetic attraction force. In still another embodiment of the present invention, the suction piece 74 may be stored in the storage hole 215, and the permanent magnet piece 77 may be fixed to the sleeve 71.

The insertion hole 20 of the inner cylinder 212 of the mounting member 78
The protrusion 211 formed on the inner surface that forms the
The projection 211 is formed with an inclined portion 216. The inclined portion 216 is an end on the downstream side (downward in FIG. 7) in the insertion direction 217 where the end 76 of the connecting rod 70 is inserted into the insertion hole 209, and is located downstream in the insertion direction 217 (downward in FIG. 7). The projections 211 are formed so as to become lower as they become smaller. As a result, the end portion 76 can be easily inserted into and fixed to the insertion hole 209, and the manufacturing is easy. Connecting rod 70
The mounting member 78 is made of a synthetic resin as described above, and the projection 211 is elastically contacted and fixed to the outer peripheral surface of the end 76 by the elastic force of the synthetic resin material.

6 and 7, the length y1 of the portion parallel to the axis of the projection 211 is 0.5 to 2.0 mm, preferably 1.0 to 2.0 mm. This projection 2
11, the width y2 = 0.5 to 1.0 mm. Insertion hole 20
9 is Ds = Ds1 + ε1, where Ds1 is the inner diameter of a circle concentric with the insertion hole 209 passing through the radially innermost end of the projection 211. ε1 = 1.0 to 2.0 mm. Ds
1 = D76−ε2, where D76 is the outer diameter of the end 76 of the connecting rod 70, and ε2 = 0.3 to 0.4 mm.

FIG. 8 is a sectional view of the support flange 201 taken at right angles to the axis as viewed from the left in FIG. Support flange 20
In 1, the central support portion 201 in which the above-described annular concave grooves 205 and 206 are formed is formed in a flat disk shape, and is integrally connected to the connecting rod main body 111. The center support member 201 is formed with radially extending reversal preventing portions 252 extending radially outward in the direction perpendicular to the axis of the connecting rod 70 (vertical direction in FIG. 5) at equal intervals in the circumferential direction. The inversion prevention unit 252 includes:
The width W252 is formed so as to increase toward the outside in the radial direction. As a result, the deformable portion 253 having flexibility and resilience radially outward of the holding member 202 of the diaphragm 43 is supported on the valve body 42 side.

FIG. 9 shows the support flange 20 shown in FIG.
FIG. Thickness t1 of reversal prevention part 252
Is selected to be smaller than the thickness t2 of the central support portion 251 (t1 <t2). For example, t1 = 0.5 to 1.0
mm, and t2 = 1.5 mm. Inversion prevention unit 25
2 are formed at equal intervals, for example, 5 or 6 in the circumferential direction, and one or more other 2 may be provided. Support flange 201 having inversion prevention portion 252
May be, for example, 37.5-39.0 mm. Also, the outer diameter D251 of the central support portion 251
Is, for example, 30 mm.

The surface 252 a of the inversion prevention portion 252 on the diaphragm 43 side (left side in FIG. 5) is
Direction away from the diaphragm 43 from the surface 251a on the side of the diaphragm 43 (to the right in FIG. 5, below in FIG. 9).
, That is, the surfaces 252a, 251a
Has a step Δt (Δt = t2−t1).

When the valve element 42 is suddenly separated from the valve seat 82 and greatly displaced, the pressure in the second space 46 is reduced by the action of the throttle hole 69, and the diaphragm 43 is deformable in an arcuate shape as shown in FIG. The portion 253 protrudes at least partially toward the valve body 42, that is, toward the second space 46, and is deformed.

FIG. 10 is a cross-sectional view for explaining a state in which the deformable portion 253 of the diaphragm 43 is deformed in the prior art in which the inversion prevention portion 252 is not formed, and for explaining the operation of the embodiment of the present invention. is there. In the prior art, since the inversion prevention portion 252 is not formed and the outer diameter of the support flange 201 is substantially equal to the outer diameter of the holding member 202, as shown by the imaginary line 255, the second space 4.
6 and a portion 257 that protrudes and remains on the first space 45 side.
0, that is, when the valve element 42 is
In the state in which it is in contact with 6, the valve 43 is stopped as it is, and the force in the valve closing direction by the diaphragm 43 does not act on the connecting rod 70.

According to the present invention, in order to solve this problem, an inversion preventing portion 252 is formed.
Achieves the function of preventing the portion 256 of the deformed diaphragm 43, which is indicated by the imaginary line 255, from projecting toward the second space 46 and inverting, to the inversion. As a result, the diaphragm 43 maintains a stable arcuate shape as indicated by reference numeral 253 even when the pressure in the second space 46 is relatively largely reduced, and thus applies a force in the valve closing direction to the connecting rod 70.

FIG. 11 is a view showing a pressure loss ΔP depending on the flow rate Q of the pressure fluctuation removing means 37 in the embodiment shown in FIGS. As shown in FIG. 11, in the range of less than the flow rate Q1 (800 L / h), the fluidic flow meter 36 is easily affected by the fluctuation of the pressure of the supplied gas. A high pressure loss can be obtained in a range of not less than the allowable value ΔP1 and less than the pressure loss ΔP2 effective for pressure fluctuation noise. At a large flow rate equal to or higher than the predetermined flow rate Q2, the pressure loss can be rapidly reduced. Valve seat 82
Therefore, the inner diameter Wv of the valve hole 41 is about 41 mm,
The gap d1 with Wp is set to about 0.7 mm. As shown in FIG. 3, when an opening degree, which is a distance of the valve body 42 from the valve seat 42 in the axial direction, is α, the protrusion 13
The annular flow path cross-sectional area S1 between the valve seat 2 and the valve seat 82 is as follows: S1 ≒ π · Wv · α (2) The second flow path cross-sectional area S2 formed by the gap d1 between the outer peripheral surface of the cylindrical body 131 of the valve body 42 and the inner peripheral surface of the valve hole 41 is given by: S2２ (π / 4) · (Wv ² −Wp ²⁾ ) (3)

When the valve element 42 is separated from the valve seat 82 to the left in FIG. 3 and the flow rate Q increases and the opening degree α becomes equal to or larger than the predetermined value αc, the flow rate Q2 becomes as shown in FIG. As shown, the second flow path cross-sectional area S1 is larger than the first flow path cross-sectional area S1.
2 is smaller and the magnitude relationship is reversed, so that the pressure loss of the pressure fluctuation removing means 37 is equal to the second flow path cross-sectional area S2
Will be determined by The flow rate Q2 is, for example, 1800 L / h as described above, and in a large flow rate range equal to or higher than the flow rate Q2, the second flow path cross-sectional area S2 becomes dominant with respect to the pressure loss. The bottom 133 of the valve body 42 is
When the cylinder portion 134 is in the valve hole 41 without separating from the valve body 41, the second flow path cross-sectional area S2 does not increase even if the valve body 42 is displaced to the left in FIG. When the bottom 133 is separated from the valve seat 82, the flow path cross-sectional area between the valve body 42 and the valve seat 82 increases rapidly according to the displacement of the valve body 42 to the left in FIG. Decreases sharply. The position of the valve body 42 is determined by the balance of forces described below. The force in the direction in which the valve element 42 opens away from the valve seat 82 is F0, and the valve element 42 is
Assuming that the force in the closing direction approaching 2 is Fc, the following equation holds. F0 = Sb · ΔP (4) Sb = (π / 4) · Wv ² (5) Fc = fmg + fd (6)

Sb is the flow path cross-sectional area of the valve hole 41. f
mg is the permanent magnet piece 7 attached to the diaphragm 43.
7 and a magnetic attraction force between the magnetic attraction piece 74 and fd
Is the rightward force in FIG. 3 where the diaphragm 43 is about to return. The balance of power is as follows. F0 = Fc (7) Sb × ΔP = fmg + fd (8) (π / 4) · Wv ² · ΔP = fmg + fd (9) Q1 may be set to, for example, a value less than 1200 to 2500 L / h. .

The force fmg is a magnetic attraction force between the permanent magnet piece 77 and the magnetic attraction piece 74 shown in FIG. 11 (3), and rapidly decreases due to the separation movement of the valve body 42 from the valve seat 82. . That is, for example, 1800 which is the flow rate Q2
In a large flow rate range of L / h or more, the magnetic attraction force fmg is sufficiently small, the differential pressure ΔP is sufficiently small, and the valve element 42 separates from the valve seat 82 and is fully opened. Thus, in the large flow rate region equal to or higher than the flow rate Q2, the pressure loss ΔP can be rapidly reduced. From the central support portion 251 of the support flange 201 to the inversion prevention portion 252, a straight frustoconical inclined surface 257 smoothly connects.

FIG. 12 is a sectional view showing the vicinity of a support flange 201 according to another embodiment of the present invention. This embodiment is similar to the above-described embodiment, and corresponding portions are denoted by the same reference numerals. It should be noted that in this embodiment, a total of three inversion prevention portions 258 are formed at equal intervals in the circumferential direction. The inversion preventing portion 258 is formed to have a tapered shape as it goes away from the axis of the connecting rod 70, that is, as it goes radially outward. According to such a configuration, the weight of the support flange 201 and the connecting rod 70 can be further reduced.

FIG. 13 is a sectional view of the vicinity of the support flange 201 shown in FIG. The inversion prevention portion 258 is formed to be thinner than the central support portion 251, and the weight is reduced.

In the above embodiment, the connecting rod 70
Although the support flange 201 is integrally formed, the number of parts can be reduced, but in another embodiment of the present invention, the support member that performs the function of the support flange 201 is different from the connecting rod 70. Manufactured separately, the end 76
To be attached to the connecting rod 70. The central portion 259 of the diaphragm 43 is also provided by the other clamping configuration or the mounting configuration in addition to the above-described embodiments in which the diaphragm 43 is clamped by a pair of support members and attached to the connecting rod 70. 259 may be fixed to the connecting rod 70.

FIG. 14 is a sectional view of the suction piece 74 constituting the magnetic suction means 81. FIG. 15 is a plan view of the magnetic attraction piece 74. The suction piece is made of a ferromagnetic material, such as iron, as described above, is an annular plate, and has a thickness t3.
Is 0.8 to 1.2 mm, and a mounting hole 79 into which the sleeve 71 is inserted is formed. Inner diameter D of mounting hole 79
i is, for example, 10 to 14 mmφ, and the outer diameter Dj is
For example, the diameter is 18 to 21 mmφ, preferably the outer diameter Dj.
Is 20 to 21 mm.

The permanent magnet piece 77 for generating magnetic attraction together with the attraction piece 74 has a configuration similar to that of the attraction piece 74 shown in FIGS. 22 and 15, is annular, and has a thickness of, for example, 3 μm. ７7 mm, and the inner diameter of the mounting hole through which the hitting cylinder 212 of the mounting member 78 is inserted is, for example, 14
mmφ, and the outer diameter is, for example, 20 mmφ.

By the magnetic attraction force of the attraction force piece 74 and the permanent magnet piece 77, the valve body 42 is connected to the valve seat 82 via the connecting rod 70.
, That is, in the valve closing direction. If the flow rate is small and the valve element 42 is in a substantially closed state, a relatively large pressure loss occurs, and the valve element 42 has a gas pressure on the upstream side and the downstream side of the valve body 42 in the gas flow direction. The difference causes a force in the valve opening direction. The force in the valve opening direction, the magnetic attraction force, and the first and second spaces 45, 45 of the diaphragm 43.
The degree of opening by the valve body 42 is determined by the pressure difference between the valves 46.
The magnetic force of the permanent magnet pieces 77, that is, the coercive force differs between individuals, and there is a variation. This results in a different magnetic attraction, and thus a variable pressure loss due to the valve element 42.

The pressure loss at a small flow rate by the pressure fluctuation removing means 37 using the valve element 42 must be reliably kept within the range of 150 to 200 Pa, preferably 160 to 200 Pa.
It must be kept within the range of 200 pa, and if it is out of this range, it will be defective. If the pressure loss is less than 150 Pa,
External gas pressure fluctuation noise cannot be sufficiently suppressed by the pressure fluctuation removing means 37, and thus a large error occurs in the measurement result of the gas flow rate by the fluidic flow meter 36. When the pressure loss exceeds 200 Pa, the pressure loss at a small flow rate is too large, and it becomes impossible to supply gas such as city gas at an appropriate gas pressure to gas consuming equipment downstream of the gas meter 31. Even if the variation in the holding force of the permanent magnet pieces 77 is relatively large, it is desired that the pressure loss at the time of a small flow rate be within the above-described range, whereby the permanent magnet pieces 77 can be obtained at low cost.

The range ± a% in which the variation in the holding force of the permanent magnet pieces 77 is allowed will be considered. The standard set pressure loss by the pressure fluctuation removing means 37 at the time of a small flow rate is X0 (P
a). When the variation ± a of the holding force of the permanent magnet piece 77 is large, the variation ± Δx of the standard set pressure loss X0 is also large. The distance Δy along the axis of the connecting rod 70 between the suction piece 74 and the permanent magnet piece 77 is appropriately determined, and the standard set pressure loss X0 is selected within a range of 150 to 200 Pa, for example, X0 = 190 Pa. it can.

The magnetic attraction force between the attraction piece 74 and the permanent magnet piece 77 is F1, the standard magnetic attraction force at the pressure fluctuation removing means 37 of the standard fluidic gas meter is F2, and the permanent magnet piece 77 is held. It is assumed that the variation of the force has a variation of ± a% with respect to the value of the standard product. At this time, Equation 10 is established. F1 = F2 · (1 ± a / 100) (10)

When the flow rate is small and the valve element 42 is close to the valve seat 82, the axial force of the connecting rod 70 is balanced with the magnetic attraction force F1 in the direction to close the valve element 42, The force in the direction in which the valve element 42 is opened, that is, the force Fx of Formula 2, which is represented by the product Sv · X of the pressure loss X due to the valve element 42 and the pressure receiving cross-sectional area Sv of the valve element 42, is governed. Fx = Sv · X (11) Fx = F1 (12)

Therefore, based on equations 10 to 12, equation 13
Is obtained, and the pressure loss X is obtained as in Expression 14. Fx = Sv · X = F2 · (1 ± a / 100) (13) ∴X = F2 · (1 ± a / 100) / Sv (14)

In the standard product of the pressure fluctuation removing means 37, the force F3 in the direction in which the valve element 42 opens is the product of the predetermined standard pressure loss X0 and the pressure receiving sectional area Sv (= X0 · Sv).
Therefore, equation 15 holds. F3 = X0 · Sv = F2 (15)

Therefore, Expression 16 is established. X = F3 · (1 ± a / 100) Sv = X0 · Sv · (1 ± a / 100) Sv = X0 · (1 ± a / 100) (16)

When the variation ± a of the holding force of the permanent magnet piece 77 is changed, the pressure loss X of the pressure fluctuation removing means 37 by the valve element 42 can be obtained by the calculation of Expression 16 as shown in Table 1 below. it can.

[0089]

[Table 1]

In the embodiment shown in FIGS. 1 to 15, the thickness t3 of the suction piece 74 is 1.0 mm,
Inner diameter Di = 14 mmφ, outer diameter Dj = 20 mmφ, along the axial direction of the connecting rod 70 between the suction piece 74 and the permanent magnet piece 77 when the valve body 42 is seated on the valve seat 82 and in the closed state. The separation distance Δy = 5.0 mm.

Variation in holding force of permanent magnet piece 77 ± a =
Table 2 shows a comparative example at 10%.

[0092]

[Table 2]

FIG. 16 is a diagram showing the above-described experimental results shown in Tables 1 and 2. If the variation ± a of the holding force of the permanent magnet pieces 77 increases, the range of the value of the pressure loss X at a small flow rate increases. Standard setting pressure loss X0 = 190
Pa, and the maximum allowable value of the pressure loss X at a small flow rate is about 19
In order to make the pressure less than 5 Pa, it is preferable that the variation ± a is less than ± 3%. According to the present invention, since the pressure loss X at a small flow rate is about 160 Pa or more, the variation ± a
= ± 8%, more preferably ± a = ± 5%. Thus,
It is possible to prevent a decrease in the measurement accuracy of the gas flow rate of the fluid flow meter 36 due to external gas pressure fluctuation noise on the upstream side of the fluidic gas meter.

In another embodiment of the present invention, the permanent magnet piece 77 is selected so that the variation ± a satisfies a ≦ ± 2%, and the standard set pressure measurement X0 is set to X0 = 195 Pa. May be set. At the time of assembly, the permanent magnet piece 77
However, the pressure loss X at the time of a small flow rate of the fluidic gas meter completed by selecting and using the one in which the variation a is 0 to + 2% exceeds 195 Pa, for example, even if it is outside the predetermined range. When the permanent magnet piece 7
7 may be replaced with a variation a = 0 to -2% and reassembled.

In yet another embodiment of the present invention, the fluidic gas meter 31 is selected by selecting a permanent magnet piece 77 having a variation in holding force of the first variation ± a1, for example, ± 8%. Assembling and measuring the pressure loss at the time of the small flow rate, and when the measured pressure loss is out of the predetermined range, that is, for example, 160 to 195P
When the value is outside the range of a, the value of the second variation ± a2 which is less than the value of the first variation ± a1 (where | a1 | ≧
| A2 |) is, for example, ± 3%, replaced, used, and assembled. Thus, an inexpensive permanent magnet piece 77 having a large first variation value is used, so that a permanent magnet having a small variation second variation value is obtained only when the pressure loss at a small flow rate is outside a predetermined range. Reassemble using the magnet pieces 77. Thus, an inexpensive fluidic gas meter can be manufactured.

The thicker the thickness t3 of the suction piece 74 (see FIG. 22 described above), the more difficult it is to perform punching press working using a mold, that is, the larger the force required for punching, and the larger the press machine becomes. , Driving costs increase,
In addition, since the wear of the mold becomes severe, the life of the mold is shortened and the cost is increased. When the suction piece 74 becomes thin, distortion deformation tends to occur. In the present invention, the thickness t3
Is selected to be 0.8 to 1.2 mm, especially about 1 mm.
When the thickness t3 is less than 0.8 mm, punching is easy, but burrs are generated and distortion deformation is apt to occur.
Further, there is a problem that the magnetic attraction with the permanent magnet piece 77 is reduced. If the thickness t3 exceeds 1.2 mm, punching becomes difficult.

FIGS. 17 and 18 are graphs showing the experimental results of the present inventor. Fluidic gas meter 11
A pressure loss ΔP is generated in accordance with the flow rate Q of the pressure fluctuation.
j, and the distance Δy between the suction piece 74 and the permanent magnetic piece 77 in the closed state in which the valve body 42 is seated on the valve seat 82.
Depends on.

[0098]

[Table 3]

In the experimental results shown in FIGS. 17 to 19 and Table 3, the thickness t3 of the suction piece 74 was 1.0 mm,
9, the inner diameter Di is 14 mmφ, and the permanent magnet piece 77 is
It has a thickness of 5 mm, an inner diameter of 10 mm, and an outer diameter of 20 mm. In FIG. 17, the distance Δy = 4.8 mm, and in FIG. 18, the distance Δy = 5.0 mm,
In FIG. 19, the separation distance Δy = 5.2 mm.

FIG. 20 is a graph of experimental results showing the relationship between the outer diameter Dj of the suction piece 74 and the pressure loss ΔP at a small flow rate obtained from the experimental results of FIGS. 17 to 19 and Table 3. The lines d48, d50 and d52 are shown in FIGS.
This corresponds to 9 experimental results. At this small flow rate, the flow rate Q =
500 Lh. From these experimental results, the inner diameter Di of the suction piece 74 is 10 to 14 mmφ so that the pressure loss ΔP at a small flow rate is in the range of 160 to 200 Pa,
The outer diameter Dj is 18 to 21 mmφ, and the outer diameter Dj is
Preferably it is 20 to 21 mmφ.

In another embodiment of the present invention, the suction piece 74
Are fixed to the sleeve 71 by stacking a plurality of individual suction pieces having a small thickness in the axial direction of the sleeve 71, thereby facilitating the production of each individual suction piece,
It is also possible to increase the magnetic attraction force between the pressure and the pressure loss at a low flow rate of, for example, about 180 Pa.

FIG. 21 is a sectional view of a pressure fluctuation removing means 37 according to another embodiment of the present invention. In this embodiment,
Similar to the embodiment of FIGS. 1 to 20 described above, corresponding parts are denoted by the same reference numerals. It should be noted that in this embodiment, the suction piece 74 is fixed to the end 76 of the connecting rod 70, and the permanent magnet piece 77 is fixed by being fitted into a mounting recess 80 formed in the sleeve 71. Diaphragm 4
3 is fixed to the suction piece 74, which is smaller and lighter than the permanent magnet piece 77, so that the diaphragm 43 and the connecting rod 70 are fixed.
The displacement of the movable part comprising the valve element 42 and the valve body 42 can be easily carried out, which ensures that the desired exact pressure loss at low flow rates is obtained. Since the second space 46 facing the permanent magnet piece 77 faces the valve chamber 67 through the throttle hole 9 of the partition 66, a large amount of rust such as iron powder contained in the gas adheres to the permanent magnet piece 77. Is prevented.

The portion 91 of the sleeve 71 near the end on the permanent magnet piece 77 side is formed to be larger than the outer diameter of the connecting rod 70 to form a gap 94. The gap 94 is provided in the valve body 4
2, the inner diameter becomes smaller, and reference numeral 95 indicates that
The connecting rod 70 is guided in the axial direction. Other configurations are the same as those of the above-described embodiment.

[0104]

According to the first aspect of the present invention, the pressure fluctuation removing means and the fluidic flow meter are provided in this order in the gas flow path of the gas meter body along the gas passage direction. In the removing means, for example, the diaphragm, and thus the connecting rod and the valve body, are displaced in the horizontal direction, for example, in the horizontal direction by a differential pressure between the pressure on the upstream side of the horizontally extending valve hole and the pressure on the gas outlet side, At low flow rates, the valve body approaches the valve seat and increases pressure loss, thereby preventing pressure fluctuation noise of the gas whose flow rate is to be measured from propagating to the fluidic flow meter. As described above, since the connecting rod and the valve element are driven to be displaced laterally by the diaphragm, there is no need to increase the pressure receiving area of the diaphragm in order to increase the force acting on the diaphragm due to its own weight. Can be miniaturized.

In particular, according to the present invention, the second space is communicated with the gas supply port by the restricting means, so that the transmission of gas pressure fluctuation noise to the second space is suppressed, and the diaphragm vibrates slightly. Is prevented, and stable pressure fluctuation by the valve body can be realized. In addition, the diaphragm is supported by the inversion prevention portion of the one support member, and can prevent the flexible and resilient deformable portion of the diaphragm from projecting toward the second space and inverting. . Therefore, even when the valve body suddenly moves away from the valve seat and is displaced, the deformable portion of the diaphragm is prevented from being deformed toward the second space, and the diaphragm causes the connecting rod and the valve body to move in the valve closing direction. A force can be exerted and axial displacement of the connecting rod and valve body is always possible.

According to the second aspect of the present invention, the reversal prevention portions are formed at intervals in the circumferential direction, so that the weight can be reduced, and therefore the valve body can be moved smoothly with excellent responsiveness. Can be made possible.

According to the third aspect of the present invention, the thickness of the reversal preventing portion is made thinner than that of the central support portion, thereby reducing the weight and thereby also improving the responsiveness of the valve body. Movement can be achieved.

According to the fourth aspect of the present invention, by disposing the surface of the reversing prevention portion on the diaphragm side in a direction away from the diaphragm, that is, displaced toward the valve body,
Smooth deformation of the deformable portion of the diaphragm due to the differential pressure in the first and second spaces is enabled, and smooth deformation of the diaphragm by the inversion prevention portion in normal operation is not suppressed.

According to the fifth and sixth aspects of the present invention, the variation in the holding force of the permanent magnet pieces of the magnetic attraction force generating means provided in the pressure fluctuation removing means is set to less than ± 8%, thereby providing a highly accurate The pressure loss of the pressure fluctuation removing means at a small flow rate can be reduced by 1 without using a permanent magnet piece having a predetermined holding force.
It is easily possible to set it within the range of 50 to 200 Pa. This facilitates the manufacture, and the fluidic gas meter is manufactured at low cost.

According to the present invention, the variation in the holding force of the permanent magnet pieces is less than ± 5%, more preferably ± 3%.
%, The pressure loss due to the pressure fluctuation removing means at the time of a small flow rate can be accurately reduced to the above-mentioned desired predetermined range of 150 to 200 Pa, thereby improving productivity. Quality is improved.

According to the eighth aspect of the present invention, since the permanent magnet piece is made of ferrite, a desired necessary holding force can be realized by a small and lightweight permanent magnet piece. Can be reduced in size. In particular, the permanent magnet piece is made small in size and light in the movable part including the valve body, and thus the diaphragm and the connecting rod, and it becomes easier to accurately obtain the pressure loss at a small flow rate.

According to the ninth and tenth aspects of the present invention, the thickness of the annular suction piece is set to 0.8 to 1.2 mm to prevent the occurrence of burrs at the time of punching, so that the deburring operation is omitted, and , And mass production becomes possible.

The inner diameter of the suction piece is 10 to 14 mmφ, and the outer diameter is 18 to 21 mmφ, preferably 20 to 21 mmφ.
It was confirmed by the experiment of the present inventor that it was possible to obtain an appropriate pressure loss at a small flow rate by selecting φ.

According to the eleventh aspect of the present invention, the attraction piece is constituted by a plurality of individual attraction pieces, so that it is easy to select and adjust the distance Δy between the permanent magnet piece and the attraction piece to an appropriate value. This makes it possible to realize a fluidic gas meter capable of obtaining an appropriate pressure loss at a small flow rate even when a permanent magnet piece having a large variation in holding force is used. , Making it easier to manufacture.

According to the twelfth aspect of the present invention, the permanent magnet piece is fixed to the gas meter main body, and the suction piece is fixed to the valve body. The movable parts including the body, the diaphragm, the connecting rod and the like can be reduced in weight, and accurate pressure loss can be easily obtained.

According to the manufacturing method of the thirteenth aspect of the present invention,
Once the gas meter is assembled using the first permanent magnet piece having a small variation in holding force, the pressure loss at the time of the small flow rate is
When it is out of the predetermined range, the second permanent magnet piece having a smaller variation is replaced and used, and thus the number of relatively expensive second permanent magnet pieces having a small variation is suppressed,
Inexpensive fluidic gas meters can be easily mass-produced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a pressure fluctuation removing unit 37 included in a fluidic gas meter 31 according to one embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing the entire configuration of a fluidic gas meter 31 including the pressure fluctuation removing means 37 shown in FIG.

FIG. 3 is a cross-sectional view of the valve element 42.

FIG. 4 is a perspective view of a part near one end 112 of the connecting rod 70;

FIG. 5 is an enlarged sectional view showing a configuration for fixing the diaphragm 43 to the other end 76 of the connecting rod 70.

6 is a front view of the mounting member 70 as viewed from the left in FIG.

FIG. 7 is a cross-sectional view of the mounting member 78.

8 is a sectional view of the support flange 201 taken at right angles to the axis in FIG. 5;

9 is a sectional view of the vicinity of a support flange 201 shown in FIG.

FIG. 10 shows a deformable portion 253 of the diaphragm 43.
Is a cross-sectional view for explaining a state of deformation in the prior art in which the inversion preventing portion 252 is not formed, and for explaining an operation of the embodiment of the present invention.

FIG. 11 is a diagram showing a pressure loss ΔP depending on the flow rate Q of the pressure fluctuation removing unit 37 in the embodiment shown in FIGS. 1 to 10;

FIG. 12 shows a support flange 20 according to another embodiment of the present invention.
FIG.

13 is a sectional view of the vicinity of a support flange 201 shown in FIG.

FIG. 14 is a sectional view of a suction piece 74 constituting the magnetic suction means 81.

15 is a plan view of a magnetic attraction piece 74. FIG.

FIG. 16 is a diagram showing the above experimental results shown in Tables 1 and 2.

FIG. 17 is a graph showing experimental results of the present inventor.

FIG. 18 is a graph showing another experimental result of the present inventor.

FIG. 19 is a graph showing still another experimental result of the present inventor.

FIG. 20 is a graph of experimental results showing the relationship between the outer diameter Dj of the suction piece 74 and the pressure loss ΔP at a small flow rate obtained from the experimental results of FIGS. 17 to 19 and Table 3.

FIG. 21 is a sectional view of a pressure fluctuation removing unit 37 according to another embodiment of the present invention.

FIG. 22 is a sectional view showing a prior art pressure fluctuation removing means 337;

[Explanation of symbols]

 REFERENCE SIGNS LIST 31 gas meter 32 gas supply port 33 gas discharge port 34 gas flow path 35 gas meter main body 36 fluidic flow meter 37 pressure fluctuation removing means 41 valve hole 42 valve body 43 diaphragm 50 fluidic element 70 connecting rod 83 first holding body 86 second Holder 89 Cylindrical body 111 Connecting rod body 201 Support flange 202 Nipping member 251 Center support portion 252, 258 Inversion prevention portion 253 Deformable portion

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Makoto Okabayashi 4-1-2, Hirano-cho, Chuo-ku, Osaka-shi, Osaka Inside Osaka Gas Co., Ltd. (72) Shuichi Okada 4-chome, Hirano-cho, Chuo-ku, Osaka-shi, Osaka 1-2-2 Inside Osaka Gas Co., Ltd. (72) Inventor Kazuichi Tomoda 4-7-131 Nishiiwata, Higashi-Osaka-shi, Osaka Inside Kansai Research Laboratory, Kinmon Manufacturing Co., Ltd. (72) Inventor Masanari Imazaki Higashi-Osaka, Osaka 4-7-31 Nishiiwata Kansai Research Laboratories, Kinmon Manufacturing Co., Ltd. (72) Inventor Masanobu Namimoto 10 Kanoda Gas Meter Co., Ltd., Nakadoji, Shimogyo-ku, Kyoto, Kyoto Prefecture (72) Inventor Eiji Nakamura Kyoto, Kyoto Prefecture F-term (reference) in Kansai Gas Meter Co., Ltd. 10 Kanoda-cho, Shimoda-ku, Shimogyo-ku

Claims (13)

[Claims] (A) a gas meter main body having a gas flow path communicating between a gas supply port and a gas discharge port; and (b) an alternating pressure change which is interposed in the gas flow path and generated by passage of gas. (C) pressure fluctuation removing means interposed in the gas flow path on the upstream side in the gas passage direction with respect to the gas flow direction to absorb the pressure fluctuation, and c1) a holding member having a valve seat that communicates with the gas supply port and extends laterally and faces the downstream side in the gas passage direction; (c2) a valve member that can be inserted into and removed from the valve hole; A) a diaphragm for partitioning the diaphragm chamber of the gas meter body into a first space communicating with the gas discharge port side of the gas flow path, and a second space communicating with the gas supply port of the gas flow path; And one end through which the valve is inserted A connecting rod having the other end through which the diaphragm is inserted; and (c5) holding means arranged at the other end, for holding the diaphragm between the pair of support members 201 and 202 and fixing the diaphragm to the other end. And (c6) throttle means for communicating the second space with the gas supply port on the downstream side of the valve body. (C7) The diaphragm bulges in a convex arc shape on the opposite side to the valve body. (C8) One support member 201 on the valve body side extends outward in the direction perpendicular to the axis of the connecting rod more than the other support member on the opposite side to the valve body with respect to the diaphragm, and the diaphragm moves toward the valve body. And (c9) a force that pushes the diaphragm due to the differential pressure between the first and second spaces and a force that pushes the valve element due to the differential pressure between the front and rear of the valve element. Open and close the valve to approach the maximum flow rate Take it,
A fluid fluctuation type gas meter comprising: a pressure fluctuation removing means for largely separating the valve body from a valve seat. 2. The fluidic gas meter according to claim 1, wherein the inversion prevention portions are formed at intervals in a circumferential direction. 3. The thickness t1 of the inversion prevention portion 252 is selected to be smaller than the thickness t2 of the central support portion 251 closer to the axis of the connecting rod than the inversion prevention portion 252 of the one support member 201 is. The fluidic gas meter according to claim 1 or 2, wherein 4. A surface 25 on the diaphragm side of the reversal prevention portion.
2a is the diaphragm-side surface 2 of the central support portion 251;
The fluidic gas meter according to any one of claims 1 to 3, wherein the fluidic gas meter is provided so as to be shifted from the diaphragm in a direction away from the diaphragm. 5. The pressure fluctuation removing means includes a magnetic attraction force generating means for generating a magnetic attraction force in a direction in which the valve element approaches the valve seat at a small flow rate between the valve element and the valve seat. The generating means includes an annular permanent magnet piece, and an annular attracting piece made of a ferromagnetic material and exerting a magnetic attractive force together with the permanent magnet piece. One of the permanent magnet piece and the attracting piece is a valve body. The other one of the permanent magnet piece and the attraction piece is provided on the gas meter main body, and the variation in the holding force of the permanent magnet piece is set to less than ± 8%. Due to the magnetic attraction force of the permanent magnet piece and the attraction piece, a pressure loss is generated within a range of 150 to 200 Pa, and the diaphragm has a force to push the diaphragm due to a differential pressure between the first and second spaces. , Due to the differential pressure across the valve Fluidic gas meter according to the magnetic attraction force provided by the force and the magnetic attraction force generating means for pressing the valve body, one of claims 1 to 4, wherein the act. 6. A gas meter body in which a gas flow path communicating between a gas supply port and a gas discharge port is formed, and (b) an alternating pressure change which is interposed in the gas flow path and caused by the passage of gas. (C) pressure fluctuation removing means interposed in the gas flow path upstream of the fluid flow direction in the gas flow direction to absorb the pressure fluctuation, and (C1) a holder having a valve seat that communicates with the gas supply port and has a horizontally extending valve hole and faces the downstream side in the gas passage direction; (c2) a valve body that moves close to and away from the valve seat; (C) a magnetic attraction force generating means for generating a magnetic attraction force in a direction in which the valve element approaches the valve seat at a small flow rate by the valve element and the valve seat; -2) Made of ferromagnetic material, together with permanent magnet pieces (C3-3) one of the permanent magnet piece and the attraction piece is coaxially fixed to the valve body, and (c3-4) the permanent magnet piece or the attraction. One of the other pieces is provided in the gas meter main body. (C3-5) The variation in the holding force of the permanent magnet piece is set to less than ± 8%. (C3-6) When the flow rate is small due to the valve body and the valve seat, (C4) a magnetic attraction force generating means for generating a pressure loss within a range of 150 to 200 Pa by exerting the magnetic attraction force between the magnet piece and the attraction piece; A first space communicating with the gas outlet of the gas flow path and a second space communicating with the gas supply port of the gas flow path;
The valve body is opened and closed by a force that pushes the diaphragm due to the differential pressure in the space, a force that pushes the valve body due to the differential pressure across the valve body, and a magnetic attraction force that is given by the magnetic attraction force generating unit,
A pressure fluctuation removing means having a diaphragm for largely separating the valve body from the valve seat as the flow rate approaches the maximum flow rate. 7. The variation in the holding force of the permanent magnet pieces is set to ± 5.
%. The fluidic gas meter according to claim 5 or 6, wherein the gas content is less than 10%. 8. A fluidic gas meter according to claim 5, wherein the permanent magnet pieces are made of ferrite. 9. The suction piece is annular, and has a thickness of 0.8 to 1.2 mm, an inner diameter of 10 to 14 mm, and an outer diameter of 18 to 21 mm.
Fluidic gas meter according to one of the claims. 10. The fluidic gas meter according to claim 9, wherein the suction piece has an outer diameter of 20 to 21 mmφ. 11. The fluidic gas meter according to claim 9, wherein the suction piece is formed by stacking a plurality of individual suction pieces having the same size in the axial direction of the valve element. 12. The fluidic gas meter according to claim 6, wherein the permanent magnet piece is fixed to the gas meter main body, and the suction piece is fixed to the valve body. 13. The method for assembling a fluidic gas meter according to claim 1, wherein a first permanent magnet piece having a first variation value and a second variation value less than the first variation value are provided. A second permanent magnet piece having a value is prepared, assembled using the first permanent magnet piece, and a pressure loss at a small flow rate is measured. When the measured pressure loss is out of a predetermined range, A method for assembling a fluidic gas meter, wherein a second permanent magnet piece is replaced and used instead of the first permanent magnet piece.