JPH09329475A - Flapper type flow switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flapper type flow switch which can perform accurate detection of the rate of flow regardless of the installing position. SOLUTION: A supporting part 18 is installed protrusively in a flow path 16 provided in the body part 14. A flapper 12 is arranged so that its one end is installed on the supporting part 18 turnably round the first turning shaft D while the other end turns round the first turning shaft D between the close position to block the flow path 16 and the open position to release it. A stationary magnet 32 is mounted on the supporting part 18 so that the N-pole and S-pole are positioned in point symmetry about the first shaft D. At the first named end of the flapper 12, a movable magnet 36a is attached in such an arrangement that the N-pole and S-pole are in point symmetry about the first shaft D. A repulsive and sucking force are produced between the movable magnet 36a and stationary magnet 32, and an energizing force is applied to the flapper 12 so that its other end always turns in the direction of closing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flapper type flow switch for confirming the flow of liquid inside a pipe or the like.

[0002]

2. Description of the Related Art For example, in a circulating water heater for continuously circulating hot water in a bath or hot spring,
A flow switch is provided to confirm the state of the flow of hot water in the pipe. By confirming the flow of hot water with this flow switch, for example, clogging of a filter for filtration is detected, and ON / OFF control of a heater for heating hot water is performed. Although there is an impeller type flow switch, a flapper type is generally used for detecting hot water such as a bath or hot spring, in which body hair such as hair is less likely to be wrapped. As this flapper type flow switch, for example, there is JP-A-7-294542. As shown in FIG. 9, this flow switch 100 has one end (the right end in the drawing) axially mounted in the flow path 104 of the body portion 102 and the other end (the left end in the drawing) centered on the shaft mounting position A. A flapper 106 that rotates and moves between a closed position B that closes the flow path 104 and an open position C that opens.
It has a movable magnet 108 provided at the other end of the flapper 106. Further, a fixed magnet 110 for attracting the movable magnet 108 is arranged on the wall surface side of one side (downward in the drawing) of the flow path which comes into contact with the other end when the flapper 106 moves to the closed position B, and the flapper 1
A reed switch 112 that is turned on / off by the magnetic force of the movable magnet 108 is arranged outside the other wall surface of the body portion 102 that comes into contact with the other end when 06 is moved to the open position C.

With this configuration, when the fluid is not flowing in the flow path 104, the movable magnet 108 is attracted by the fixed magnet 110 and the flapper 106 is closed at the closed position B.
The movable magnet 10 to the reed switch 112.
The reed switch 112 is in the off state because the influence of the magnetic force of 8 is small. When the fluid flows over a predetermined flow rate, the flapper 106 moves due to the fluid pressure from the fluid.
The fixed magnets 108, 110 are rotated to the open position C against the attraction force between them, and this rotating movement causes the movable magnet 108 to approach the reed switch 112, and the reed switch 112 is turned on. Therefore, the flow path 1 is detected by detecting the on / off state of the reed switch 112.
The flow of fluid in 04 can be confirmed.

[0004]

However, the above-mentioned conventional flapper type flow switch has the following problems. First, since the movable magnet 108 is attached to the rotating tip of the flapper 106, the flapper 1
The gravity of the movable magnet 108 is applied to 06 in addition to the attraction force between the magnets. Therefore, the fluid pressure, that is, the flow rate of the fluid required to rotate the flapper 106 from the closed position B to the open position C changes depending on the direction of the body portion 102, that is, the mounting direction of the flapper 106, and the accurate detection of the flow rate is performed. There was a problem that could not be done. Also,
Since the movable magnet 108 moves between the facing portions of the inner wall surface of the flow path, the moving distance is long. Therefore, the attractive force that the movable magnet 108 receives from the fixed magnet 110 provided at one of the above-mentioned portions greatly changes depending on the rotation angle of the flapper 106. That is, when the distance between the magnets is short, the attraction force is extremely large, and when the magnets are far apart, it is extremely weak. Therefore, the rotational force acting on the flapper 106 also largely changes depending on the rotation angle of the flapper 106, and there is a problem that accurate flow rate detection cannot be performed when the flow rate is detected based on the rotation angle of the flapper.
Further, the magnetic force of the magnet generally varies.
Therefore, when the flapper 106 is rotated by fluid pressure and the movable magnet 108 approaches the reed switch 112, the reed switch 112 is turned on.
Since the rotation angle of 06 also varies, there is a problem that the detected flow rate also varies.

Therefore, the present invention has been made to solve the above problems, and an object of the present invention is to accurately detect the flow rate without being influenced by the mounting position and to detect the flow rate based on the flapper rotation angle. It is an object of the present invention to provide a flapper type flow switch that can easily perform the above-mentioned operation and can easily correct the variation in the flow rate detection due to the variation in the magnetic force of the magnet.

[0006]

The present invention has the following constitution in order to achieve the above object. That is, a body portion in which a flow path is formed, a support portion projecting in the flow passage, and one end side of which is attached to the support portion so as to be rotatable about a first rotation shaft, In the flapper type flow switch, the other end side includes a flapper that rotates about the first rotation axis between a closed position that closes the flow path and an open position that opens the flow path, wherein the support portion is provided. A fixed magnet attached such that the N pole and the S pole are point-symmetrical about the first rotation axis, and N on the one end side of the flapper about the first rotation axis. The pole and the S pole are attached so as to be point-symmetrical, and a movable magnet that constantly urges the other end side of the flapper in the closing direction by a repulsion / attraction force between the fixed magnet and the fixed magnet is provided. Characterize.

With this structure, since the movable magnet is mounted so that the N pole and the S pole are point-symmetrical about the first rotation axis of the flapper, gravity acting on the movable magnet causes the flapper to move. The influence on the rotation is reduced. Therefore, the flow rate can be accurately detected even if the mounting direction of the flapper is changed. Further, the fixed magnet is also attached to the supporting portion so that the N pole and the S pole are point-symmetrical about the same first rotation axis, and the fixed magnet and the movable magnet are separated even if the flapper rotates. Do not separate. Therefore, a repulsion / attractive force for constantly rotating the flapper is generated between the fixed magnet and the movable magnet, and the degree of change in the rotational force that acts on the flapper due to the rotation angle of the flapper is reduced. Therefore, more accurate flow rate detection can be performed when the flow rate is detected based on the rotation angle.

Further, it is attached to the outer side surface of the body portion so as to be rotatable about the first rotating shaft, and a part of the edge is formed in an arc around the first rotating shaft. The arc portion meshes with the worm gear, a rotation base formed on a worm gear, a magnetic sensor attached to the rotation base for detecting that the movable magnet has rotated to a preset position, and the worm gear. If a worm that rotates the rotary base is provided, the positional relationship between the movable magnet and the magnetic sensor that detects the rotation angle of the movable magnet can be changed easily and accurately. Therefore, there are variations in the magnetic force of the movable magnet and the fixed magnet,
Even if the flow rate is constant, the rotation angle of the flap usually changes for each flow sensor, but the position of the magnetic sensor with respect to the movable magnet is finely adjusted by finely rotating the rotation base with respect to the body part, and the detected flow rate is accurate. It is possible to set a predetermined flow rate. In addition, it is also possible to correct variations in the sensitivity of the magnetic sensor.

Similarly, on the outer side surface of the body,
A rotary base mounted rotatably around the first rotary shaft, and a magnetic sensor mounted on the rotary base for detecting that the movable magnet has rotated to a preset position. It may be configured to include a fixing unit that fixes the rotary base at an arbitrary position. When a reed switch is used for the above magnetic sensor, the reed switch may be attached such that its center is on the first rotation axis and is close to the movable magnet.

Further, if the flapper is made of a synthetic resin material having a specific gravity which is substantially the same as the specific gravity of the liquid flowing through the flow path, the flow rate can be detected more accurately without being influenced by the posture and direction of the flapper.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a flapper type flow switch according to the present invention will be described in detail below with reference to the accompanying drawings. First, flapper type flow switch 10
The flapper 12 and the attachment structure of the flapper 12 will be described with reference to FIGS. 1 and 2. Reference numeral 14 denotes a synthetic resin body portion having a flow passage 16 formed therein. Liquid flows in the flow path 16 in the direction of the arrow. Reference numeral 18 denotes a synthetic resin support portion projecting in the flow path 16. The detailed structure of the support portion 18 is, for example, as shown in FIGS. 3 and 4, formed by planes whose both side surfaces are parallel to each other along the liquid flowing direction, and the flapper 12 is axially mounted between the both side surfaces. An insertion hole 22 through which the shaft 20 is inserted is formed. Further, a first long groove 24 centering on the insertion hole 22 is formed on one side surface (left side surface in FIG. 4).

The flapper 12 made of synthetic resin has a support portion 18
The first rotation axis D (which is also the central axis of the shaft 20)
One end side (the right end side in the drawing) is rotatably mounted around, and the other end side (the left end side in the drawing) closes the flow path 16 around the first rotation axis D as a closing position E. And an open position F that opens the flow path 16 are rotatable. Flapper 12
As an example, the detailed structure of is formed in a wide plate shape as shown in FIG. 3 and FIG. Mounting pieces 26a and 26b are provided in parallel. A through hole 28 through which the shaft 20 can be inserted is provided in each of the mounting pieces 26a and 26b.
Further, a second long groove 30 having the same shape as the first long groove 24 provided in the substantially support portion 18 is formed on the outer surface of each of the mounting pieces 26a and 26b. A fixed magnet 32 is mounted in the first long groove 24, and is mounted on the support portion 18 so that the N pole and the S pole are point-symmetrical with respect to the first rotation axis D. The fixed magnet 32 is provided with a through hole 34 that communicates with the insertion hole 22 when the fixed magnet 32 is attached to the first long groove 24 and allows the shaft 20 to be inserted therethrough.

36a and 36b are movable magnets,
It is formed in substantially the same shape as the fixed magnet 32 and is mounted in the second long groove 30 of the pair of mounting pieces 26a, 26b.
Is attached to the flap 12 so that the N pole and the S pole are point-symmetrical with respect to the rotation axis D. In addition, the fixed magnet 3 is also attached to the central portion of the movable magnets 36a and 36b.
As with No. 2, the through hole 28 when mounted in the second long groove 30.
A through hole 34 that communicates with the shaft 20 and allows the shaft 20 to be inserted therethrough is provided. The angle of attachment of the movable magnet 36 to the flapper 12 is set so that the other end of the flapper 12 is constantly urged toward the closed position E by the repulsion / attraction force between the movable magnet 36 and the fixed magnet 32. Specifically, when the flapper 12 moves to the closed position E, the magnets 36a, 36b are arranged so that the north and south poles of the movable magnets 36a, 36b substantially match the south and north poles of the fixed magnet 32, respectively. 36b is attached. Therefore, when the flapper 12 rotates from the closed position E to the open position F, the N and S poles of the movable magnets 36a and 36b also rotate about the first rotation axis D and the fixed magnet 32.
Since it deviates from the S pole and N pole of the fixed magnet 32
An attractive force is generated from the S and N poles of the movable magnets 36a and 36b to the N and S poles. Flapper 1
2 is always urged in the closed position E direction. In addition,
In addition to the attractive force, repulsive force also acts on the N and S poles of the movable magnets 36a and 36b from the N and S poles of the fixed magnet 32.

Reference numeral 38 denotes a movable magnet 36 of the body portion 14.
It is a reed switch as an example of a magnetic sensor provided on the outer surface on the a side. The reed switch 38 is also mounted such that its center is on the first rotation axis D and is orthogonal to the first rotation axis D. Further, the mounting direction is, for example, arranged so as to substantially coincide with the longitudinal direction of the movable magnet 36a when the flapper 12 is rotated to the open position F. As a result, the flapper 12 is rotated to the open position F, the movable magnet 36a is rotated with respect to the fixed magnet 32 and is displaced, and when it becomes substantially parallel to the reed switch 38, the reed switch 38 is turned on. That is, the tips of the two terminals (not shown) inside the reed switch 38, which are normally separated, have different magnetic poles depending on the N pole and the S pole at both ends of the movable magnet 36a when the movable magnet 36a becomes parallel to the reed switch 38. Is magnetized. Then, due to the suction force generated between the tips of both terminals, the tips of the terminals approach and abut against each other against the elastic force of the terminals themselves, and the terminals are turned on. The flapper 12 is at the closed position E, and the movable magnets 36a and 36b and the fixed magnet 3 are
When the two are substantially overlapped, both magnets 36a, 36
Since the magnetic flux of b leaks little to the outside, the magnetic flux reaching the reed switch 38 is also small, and the reed switch 38 is in the off state.

As described above, the fixed magnet 32 and the movable magnets 36a and 36b for applying the biasing force to the flapper 12 in the closing position E direction are located on the first rotation axis D, which is the center of rotation of the flapper 12, at the above-mentioned position. By arranging in a relationship, the gravity acting on the movable magnets 36a and 36b does not affect the rotation of the flapper 12, and the flow rate can be accurately detected even when the mounting direction of the flapper 12 is changed. The fixed magnet 32 is also attached to the support portion 18,
The fixed magnet 32 and the movable magnets 36a and 36b are not separated from each other even when the flapper 12 rotates, and the fixed magnet 32 is disposed so as to be on the same first rotation axis D.
Of the movable magnets 36a, 36 within a strong magnetic field
b, the flapper 12 generated between the movable magnets 36a and 36b and the fixed magnet 32 is closed at the position E.
The turning force for returning to the above condition becomes more uniform than the conventional example. Therefore, the flapper can be accurately rotated with respect to the flow rate, and the accuracy of flow rate detection is improved.

Further, since the reed switch 38 provided on the outer surface of the body portion 14 only detects that the flapper 12 is in the open position F in the above-described embodiment, only one flap switch 12 is required. In order to detect that the vehicle is at a predetermined rotational position between the closed position E and the open position F, another movable magnet 36b provided on the flapper 12 is used. Another on / off-controlled reed switch 40 may be provided on the outer surface of the body portion 14 opposite to the reed switch 38. In this case, the other reed switch 40 is mounted such that it is substantially parallel to the movable magnet 36b when the flapper 12 reaches the rotation angle to be detected. In this way, by disposing the two reed switches 38 and 40 on both side surfaces of the body portion 14 while changing the mounting angle about the first rotation axis D, the flapper 12 is placed at two different rotation positions. Can be detected, resulting in a liquid flow rate of 2
Stage detection is possible. If it is only necessary to detect that the flapper 12 is in the open position F, it suffices to provide the second long groove 30 only on one attachment piece 26a of the flapper 12 and attach the movable magnet 36a.

Further, as described in the conventional example, the magnetic forces of the movable magnets 36a and 36b and the fixed magnet 32 have variations, so that a predetermined amount of fluid flows in the flow passage 16. Also, the rotation angle of the flapper 12 varies for each individual flow switch 10.
Therefore, in order to accurately set the flow rate to be detected, the reed switch 38 that detects the rotation angle of the flapper 12 is used.
Is preferably configured so that it can be arbitrarily rotated with respect to the body portion 14 about the first rotation axis D and can be fixed at the rotation position. With this configuration, the reed switches 38 and 40 are individually rotated about the first rotation axis D in a state in which a predetermined flow rate of fluid is flown in advance in the flow path 16, and the switch state is changed from OFF to ON. When fixed in position, even if the magnetic force of the magnets varies and the rotation angle of the flapper 12 varies for each flow switch 10 at a given flow rate, the lead can be detected accurately so that the given flow rate can be detected. The mounting angle of the switch 38 with respect to the body portion 14 can be set.

Next, one embodiment of a specific structure for rotatably attaching the reed switches 38 and 40 to the body portion 14 will be described with reference to FIGS. First, the outer peripheral surface of the cylindrical body portion 14 is provided with a box-shaped protruding portion 44 in which a space portion 42 forming a part of the flow path 16 is formed. Both side surfaces 46a and 46b of the protruding portion 44 are formed on planes orthogonal to the first rotation axis D. Reference numerals 48a and 48b are rotary tables made of synthetic resin, and are external side surfaces 46a and 46b of the body portion 14.
Are rotatably attached about the first rotation axis D. Further, a part of the end edges (upper edge in FIG. 6) of the turntables 48 a and 48 b is formed in an arc shape, and this arc portion is formed in the worm gear 50. The inner surfaces of the turntables 48a and 48b on the side of the protrusion 44 are shown in FIG.
As shown in FIG. 5, the reed switches 38 and 40 are attached so that their centers coincide with the first rotation axis D.
The reed switches 38, 40 are reed switches 38,
Circuit board 5 together with electric wire 52 for taking out the signal of 40 to the outside
The circuit board 54 is soldered to the rotary table 48a,
It is attached to the 48b using a screw as an example.
That is, the reed switches 38 and 40 are fixed to the rotary bases 48 a and 48 b via the circuit board 54. In addition,
Reference numeral 56 in FIG. 6 is a circuit pattern formed on the circuit board 54 for electrically connecting the electric wire 52 and the reed switches 38 and 40.

Reference numeral 58 denotes an adjusting male screw as a worm, which is used for each of the worm gears 5 of the turntables 48a and 48b.
It is arranged at the upper part of the protrusion 44 so as to mesh with 0 along the both side surfaces 46a and 46b of the protrusion 44. As an example, the adjusting male screw 58 is made of a metal material, but a synthetic resin material may be used. A pressing plate 60 is formed using a metal flat plate. A rectangular extension portion is provided on the upper portion of the pressing plate 60, and the extension portion is L
It is bent 90 degrees in a letter shape. Further, a shaft hole 64 into which the support shaft 62 projecting from the center of the rotating bases 48a and 48b can be inserted is provided in the substantially central portion, and the shaft hole 64 and the extending portion are provided with a shaft hole 64. An arcuate hole 66 extending along the circumference centered on the hole 64 is provided. This holding plate 6
0 is screwed onto both outer side surfaces 46a, 46b of the protrusion 44 so as to cover the rotary bases 48a, 48b and the adjusting male screw 58, so that the rotating bases 48a, 48b and the adjusting male screw 58 project. It is attached to both outer side surfaces 46a, 46b of the portion 44 so as to be rotatable and non-pullable. Further, 68 is a fixing screw as a fixing means, which is screwed from the outside of the pressing plate 60 through the arc hole 66 into the screw holes 70 of the turntables 48a and 48b provided corresponding to the arc hole 66. There is.

With the above structure, when the adjusting male screw 58 as a worm is rotated by a driver or the like, the rotating bases 48a and 48b meshing with the adjusting male screw 58 are supported by the support shaft 62, that is, the first rotating shaft. Rotate around D. As a result, the reed switch 38 also rotates with respect to the body portion 14 about the first rotation axis D. After rotating by a predetermined angle, the fixing screw 68 is tightened to hold the pressing plate 60 between the inner surface of the head of the fixing screw 68 and the rotating bases 48a and 48b, and external force is applied to the rotating bases 48a and 48b. This prevents the rotation bases 48a and 48b from rotating when they are added and the flow rate detection setting from deviating. In the present embodiment, the fixing screw 68 is separately provided in order to reliably prevent the turning bases 48a and 48b from turning after the flow rate detection setting, but the adjusting male screw 58 may be provided without the fixing screw 68. The rotating table 48a, 48
The rotation of b can be suppressed to some extent. If the flow rate of the fluid detected by the flapper 12 is to detect only one flow rate value, the rotary bases 48a and 48b, the reed switch 38, the adjusting male screw 58 and the pressing plate 60 are as described above. Even if two sets are not provided, only one set is required.

If the flapper 12 is made of a synthetic resin material having a specific gravity that is substantially the same as the specific gravity of the liquid flowing through the flow path 16, the gravity applied to the flapper 12 in the fluid and the buoyancy applied to the flapper 12 from the fluid are obtained. The flow rate is substantially the same, and the predetermined flow rate can be detected even if the installation angle or direction of the flow switch 10 is changed. Further, in the above embodiment, the flapper 12, that is, the rotational position of the movable magnet 36 is detected by using the reed switch, which is an example of the proximity switch. A magnetic detection means such as an element may be used.

In the above embodiment, as shown in FIG. 7, the opening 7 communicating with the space 42 is formed on the upper surface of the protrusion 44.
2 is provided, and the supporter 18 and the flapper 12 attached to the supporter 18 are mounted in the space 42 through the opening 72. After that, the opening 72 is closed with the lid 74, and the wide portion 76 of the support 18 is sandwiched between the lid 74 and the rim of the opening 72 to fix the support 18 to the protrusion 44. However, the support portion 18 may be directly extended to the inner wall surface of the body portion 14.

Although various preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and many modifications can be made without departing from the spirit of the invention. Of course.

[0024]

When the flapper type flow switch according to the present invention is used, the movable magnet is attached so that the N pole and the S pole are point-symmetrical about the first rotation axis of the flapper. Gravity acting on the magnet does not affect the flapper rotation. Therefore, the flow rate can be accurately detected even if the mounting direction of the flapper is changed. Further, the fixed magnet is also attached to the supporting portion so that the N pole and the S pole are point-symmetrical about the same first rotation axis, and the fixed magnet and the movable magnet are separated even if the flapper rotates. Do not separate. Therefore, a repulsion / attractive force for constantly rotating the flapper is generated between the fixed magnet and the movable magnet, and the degree of change in the rotational force that acts on the flapper due to the rotation angle of the flapper is reduced. Therefore, more accurate flow rate detection can be performed when the flow rate is detected based on the rotation angle. Further, if the magnetic sensor is attached to the outer side surface of the body portion on a turntable rotatable about the first turning shaft, the magnetic sensor for detecting the turning angle of the movable magnet and the movable magnet are provided. The positional relationship of can be changed easily and accurately. Therefore,
There is variation in the magnetic force of the movable magnets and fixed magnets, and the rotation angle of the flap usually changes from flow sensor to flow sensor even when the flow rate is constant. By finely adjusting the position of the magnetic sensor, it becomes possible to accurately set the detected flow rate to a predetermined flow rate. In addition, it also has a remarkable effect that variations in sensitivity of the magnetic sensor can be corrected.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a main part of a side view showing a structure of a flapper and a supporting portion of a flapper type flow switch according to the present invention (a state in which a flapper receives fluid pressure and largely rotates).

FIG. 2 is a cross-sectional view of a main part of the side showing a state where the fluid pressure is reduced from the state of FIG. 1 and the flapper rotation angle is small.

FIG. 3 is a side view showing a structure of a support portion and a flapper.

FIG. 4 is a front exploded view showing an assembly structure of a support portion and a flapper.

FIG. 5 is a plan view showing the structure of an embodiment of a flapper type flow switch.

6 is a side view of FIG.

7 is a sectional view taken along line GG of FIG.

FIG. 8 is a sectional view taken along line HH of FIGS. 5 and 6;

FIG. 9 is a side sectional view showing the structure of a conventional flapper type flow switch.

[Explanation of symbols]

 10 Flapper type flow switch 12 Flapper 14 Body part 16 Flow path 18 Support part 32 Fixed magnet 36a, 36b Movable magnet 38 Reed switch

Claims (5)

[Claims] 1. A body portion having a flow passage formed therein, a support portion projectingly provided in the flow passage, and one end side of the support portion rotatably about a first rotation shaft. A flapper type flow switch having a flapper attached to the other end thereof, the flapper rotating between the closed position closing the flow path and the open position opening the flow path about the first rotation axis. An N pole and an S pole centered on the first rotation axis are provided on the support portion.
A fixed magnet mounted so that its poles are point-symmetrical; and a fixed magnet mounted on the one end side of the flapper such that the N-pole and the S-pole are point-symmetrical about the first rotation axis, and A flapper type flow switch comprising: a movable magnet that constantly urges the other end side of the flapper in the closing direction by a repulsion / attraction force between the fixed magnet and the fixed magnet. 2. An outer side surface of the body portion is rotatably attached about the first rotation shaft, and
A part of the edge is formed in an arc centered on the first rotation axis, and the arc part is attached to the rotation base formed on the worm gear, and the movable magnet is preset. The flapper type flow switch according to claim 1, further comprising: a magnetic sensor that detects that the rotary table is rotated to a different position, and a worm that meshes with the worm gear to rotate the rotary table. 3. A rotary base mounted on the outer side surface of the body so as to be rotatable around the first rotary shaft, and a movable magnet which is mounted on the rotary base and is preset. The flapper type flow switch according to claim 1, further comprising: a magnetic sensor that detects that the rotary base is rotated to a different position, and a fixing unit that fixes the rotary base at an arbitrary position. 4. A reed switch is used for the magnetic sensor, and the reed switch is mounted such that its center is on the first rotation axis and is close to the movable magnet. The flapper type flow switch according to claim 2 or 3. 5. The flapper type flow switch according to claim 1, wherein the flapper is formed by using a synthetic resin material having a specific gravity substantially the same as the specific gravity of the liquid flowing in the flow path. .