JP2008267888A - Flow rate sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve flow rate sensing precision of a flow rate sensor 1 by reducing a rotation load of a vane wheel 30, the flow rate sensor 1 having a casing 20 in which a fluid path 200 is provided to penetrate it, the vane wheel 30 supported freely rotatably in the peripheral direction in the fluid path 200, and a rotation detecting means S for detecting the rotational frequency of the vane wheel 30. <P>SOLUTION: A first magnet 34 is provided at the rotation center part of the vane wheel 30, a second magnet 24 is provided from the down stream side of the fluid path 200 while facing to the first magnet 34, and the mutual facing surfaces of the first magnet 34 and the second magnet 24 are set to have same polarity, respectively. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a flow sensor that measures the flow rate of a fluid from the rotational speed of an impeller.

  Among conventional flow rate sensors used by connecting to piping such as a hot water heater or a hot water heater, there is an impeller type that detects the flow rate from the rotational speed of the impeller. This is configured so that the rotational load of the impeller becomes as small as possible from the viewpoint of exhibiting good flow rate detection accuracy.

FIG. 7 is a schematic configuration diagram of a conventional flow rate sensor 7, and a casing 80 in which a fluid passage 800 is provided, an impeller 90 that is pivotally supported in the circumferential direction in the fluid passage 800, and a blade And a magnetic detection element S for detecting a change in the strength of the magnetic field corresponding to the rotational speed of the vehicle 90.
Bearing portions 81a and 81b are formed at the centers of the upstream opening 80a and the downstream opening 80b of the fluid passage 800, and a sphere 84 is fitted into the bearing 81b of the downstream opening 80b. Has been.

The impeller 90 has a configuration in which a plurality of blades 92 made of a magnetic material and magnetized are circumferentially fixed to a rotation shaft 91. Both shaft ends of the rotation shaft 91 are connected to the bearing portions 81a and 81b. So that it can be rotated and slidable in the axial direction. Therefore, when the fluid flows into the fluid passage 800 and the dynamic pressure of the fluid is applied in the downstream direction (in the direction of the downstream opening 80b of the fluid passage 800), the downstream end surface 910 of the rotating shaft 91 is formed on the sphere 84. It rotates at the number of rotations corresponding to the flow rate in the contacted state.
Further, the blades 92 spread radially from the peripheral surface of the rotating shaft 91 to the vicinity of the inner peripheral surface 801 of the fluid passage 800.

On the other hand, the magnetic detection element S has its detection surface S1 facing the inner peripheral surface 801 of the fluid passage 800, and detects the magnetic field at the tip of the blade 92 that passes in front of the detection surface S1 when the impeller 90 rotates. Each time the magnetic field is detected, a pulse signal is output.
In this configuration, when the fluid flows into the fluid passage 800, the impeller 90 rotates by bringing the downstream end surface 910 of the rotating shaft 91 and the sphere 84 into point contact with each other, so that the rotational load is small and relatively stable. The flow rate detection performance is demonstrated.
Japanese Utility Model Publication No. 63-188522

  However, in the conventional device, the rotational load of the impeller 90 is not sufficiently reduced due to the rotational frictional resistance between the downstream end surface 910 and the sphere 84, and thus the flow rate detection performance is still insufficient.

The present invention has been made in view of such points,
In a flow sensor comprising a casing having a fluid passage therethrough, an impeller pivotally supported in the fluid passage in the circumferential direction, and a rotation detecting means for detecting the rotational speed of the impeller. It is an object to improve flow rate detection accuracy by reducing the rotational load of the impeller.

The technical means of the invention according to claim 1 for solving the above-mentioned problem is as follows:
“A first magnet is installed at the center of rotation of the impeller.
A second magnet is provided at a position facing the first magnet from the downstream side of the fluid passage;
The opposing surfaces of the first magnet and the second magnet are set to the same magnetic pole.
According to the above technical means, the opposing surfaces of the first magnet provided at the center of rotation of the impeller and the second magnet facing the first magnet from the downstream side of the fluid passage are between the same magnetic poles. Therefore, the impeller rotates in a state where the rotation center portion and the opposed surface thereof are not in contact with each other, that is, in a state where the rotational frictional resistance is extremely small. As a result, the rotational load of the impeller is reduced as compared with the conventional one.

The technical means of the invention according to claim 2 is:
In claim 1,
“The first magnet is fixed to the end of the rotating shaft that projects from the impeller to the downstream side of the fluid passage, and the second magnet is fixed to the bearing that supports the end”.
In this configuration, the first magnet is provided at the end of the rotating shaft of the impeller that is rotatably supported, and the second magnet is provided at the bearing portion that supports the end of the rotating shaft, whereby the above-mentioned repulsion is achieved. The relative positional relationship between the opposing surfaces of the first magnet and the second magnet on which the force acts is unlikely to shift in the direction intersecting the axis of the rotation axis. As a result, the rotation of the impeller is stabilized.

The technical means of the invention according to claim 3 is:
In the claim 1 or 2,
“A spherical convex portion is provided on the facing surface of either the first magnet or the second magnet”.
In this case, when a large amount of fluid flows into the fluid passage and a dynamic pressure in the downstream direction larger than the repulsive force is applied to the impeller, the opposing surfaces of the first magnet and the second magnet are The spherical convex portion makes point contact while maintaining the above repulsive force. In other words, the impeller rotates by making point contact between the rotation center portion and the opposing surface with the spherical convex portion while the above-described repulsive force is maintained.
This not only reduces the rotational load of the impeller, but also suppresses the wear between the opposing surfaces of the first magnet and the second magnet, as compared with the conventional one described above.

Since the present invention has the above configuration, the present invention has the following specific effects.
In the invention according to claim 1, since the impeller rotates without contacting the rotation center portion and the facing surface thereof, the rotation load of the impeller is reduced as compared with the conventional one, so that the flow rate detection is performed. Accuracy is improved.

  In addition, since the impeller rotates without contacting the rotation center portion and the facing surface thereof, the rotation center portion and the facing surface do not wear, and thus an increase in rotational load of the impeller over time can be prevented. The Thereby, the flow rate detection accuracy can be maintained over a long period of time.

  In the invention according to claim 2, since the relative positional relationship between the opposed surfaces of the first magnet and the second magnet is less likely to be shifted, the rotation of the impeller is stabilized, so that the flow rate detection accuracy is further improved. .

  In the invention which concerns on Claim 3, when the impeller receives the dynamic pressure in the downstream direction larger than the above-mentioned repulsive force, the opposing surfaces of the first magnet and the second magnet facing each other on the downstream side of the fluid passage come into contact with each other. Even if it exists, since the abrasion of the contact part is suppressed by the above-mentioned repulsive force, the flow rate detection accuracy can be maintained for a longer period.

Next, the best mode for carrying out the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic configuration diagram of a flow sensor 1 according to an embodiment of the present invention.
The flow rate sensor 1 is an impeller-type flow rate sensor that detects a flow rate from the number of revolutions of the impeller 30, and is used by being connected to a pipe such as a hot water heater or a hot water heater (not shown).
A fluid passage 200 that connects the upstream opening 20a and the downstream opening 20b is provided in the casing 20 of the flow sensor 1, and the impeller 30 rotates in the circumferential direction within the fluid passage 200. It is pivotally supported.

In addition, a magnetic detection element S for detecting a change in strength of the magnetic field is attached to the outer wall 201 of the casing 20.
The magnetic detection element S has a detection surface S1 that is in close contact with the outer wall 201, and detects an outer peripheral magnetic field of a cylindrical magnet 33 (described later) that passes in front of the detection surface S1 when the impeller 30 rotates. In addition, a pulse signal is output as the magnetic field continuously changes.
The “magnetic detecting element S” corresponds to “rotation detecting means” as the invention specifying matter of claim 1 described above.

In addition, bearings 21 a and 21 b that support the rotating shaft 31 of the impeller 30 are formed at the centers of the upstream opening 20 a and the downstream opening 20 b.
A bearing portion (hereinafter referred to as “upstream bearing portion”) 21a provided in the center of the upstream opening 20a is formed in a substantially cylindrical shape that opens from the upstream side to the downstream side, and has an end face 21f on the downstream side. Is inclined in a spiral. And the standing part 21g is formed in this spiral termination.

On the other hand, a bearing portion (hereinafter referred to as a “downstream bearing portion”) 21b provided at the center of the downstream opening 20b is formed in a substantially cylindrical shape that opens to the upstream side. Is embedded with a short cylindrical second magnet 24.
The second magnet 24 is a double-sided bipolar magnet in which one end face is magnetized with N pole and the other end face is magnetized with S pole, and one end face (here, N pole face) 240 will be described later. It faces the first magnet 34.

Further, the N pole surface 240 of the second magnet 24 is formed in a spherical shape.
The entire surface of the “N pole surface 240” formed in a spherical shape corresponds to the “spherical convex portion” as the invention specific matter of the third aspect.

  The impeller 30 is formed by integrally forming a plurality of blades 32 on a rotating shaft 31 extending from the upstream side to the downstream side of the fluid passage 200, and the upstream shaft of the rotating shaft 31 protruding upstream from the root portion of the blade 32. The end portion 31a can turn to the upstream bearing portion 21a, and the downstream shaft end portion 31b of the rotating shaft 31 protruding from the root portion of the blade 32 to the downstream side can rotate with respect to the downstream bearing portion 21b and in the axial direction thereof. It is inserted in a slidable state.

A cylindrical magnet 33 having a smaller diameter than the inner diameter of the fluid passage 200 is provided around the tip end side of the blade 32.
The cylindrical magnet 33 is an outer peripheral multipolar magnet in which a plurality of N poles and S poles are alternately magnetized along the outer periphery thereof, and the inner peripheral surface of the fluid passage 200 when the impeller 30 rotates. And the magnetic field around the detection surface S1 is continuously changed.

  On the other hand, a step surface 31f is formed at the base of the upstream shaft end 31a of the rotary shaft 31. The step surface 31f is inclined in a spiral shape, and a standing portion 31g is formed at the end of the spiral.

  Accordingly, when the fluid flows backward from the downstream opening 20b into the fluid passage 200 and the impeller 30 slides in the upstream direction (in the direction of the upstream opening 20a of the fluid passage 200), the rising portion 31g and the upstream The upright portion 21g of the side bearing portion 21a is engaged, and the impeller 30 is prevented from rotating.

A short columnar first magnet 34 is fixed to the downstream shaft end 31 b of the rotating shaft 31.
The “tip” of the downstream shaft end portion 31b corresponds to the “rotation center portion” as the invention specific matter of claim 1 described above.
The first magnet 34 is a double-sided, two-pole magnet in which one end face is magnetized with an N pole and the other end face is magnetized with an S pole, and one end face (here, the N pole face) 340 is the first pole. Two magnets 24 are faced. That is, the opposing surfaces of the first magnet 34 and the second magnet 24 are set to have the same magnetic pole.

  Therefore, the N pole surface 340 of the first magnet 34 and the N pole surface 240 of the second magnet 24 are biased in a direction away from each other by the repulsive force between the same magnetic poles. This repulsive force is larger than the dynamic pressure in the downstream direction applied to the impeller 30 when a fluid having a preset maximum flow rate (for example, 30 liters / minute) flows into the fluid passage 200. Is set.

Further, the N pole surface 340 of the first magnet 34 is formed in a planar shape.
In this configuration, when the fluid flows from the upstream opening 20a into the fluid passage 200, dynamic pressure is applied to the impeller 30 in the downstream direction. At this time, the second pressure provided in the downstream bearing portion 21b is applied. The N pole surface 240 of the magnet 24 and the N pole surface 340 of the first magnet 34 provided at the downstream shaft end portion 31b are biased in a direction away from each other by the repulsive force between the same magnetic poles.

  Accordingly, the impeller 30 is in a state where the end surface of the downstream shaft end portion 31b (N pole surface 340 of the first magnet 34) and its opposing surface (N pole surface 240 of the second magnet 24) are not in contact, that is, the rotation. It rotates with a very small dynamic frictional resistance. Thereby, the rotational load of the impeller 30 is reduced compared with the conventional one, and the flow rate detection accuracy is improved.

  In addition, the above-described repulsive force prevents wear on the end surface of the downstream shaft end portion 31b (N pole surface 340 of the first magnet 34) and its opposing surface (N pole surface 240 of the second magnet 24). An increase in the rotational load of the impeller 30 over time is also prevented. Thereby, the flow rate detection accuracy can be maintained over a long period of time.

  Furthermore, by providing the second magnet 24 at the downstream bearing portion 21b and the first magnet 34 at the downstream shaft end portion 31b, the N pole surface 340 of the first magnet 34 and the N pole surface of the second magnet 24 are provided. Since the relative positional relationship between 240 hardly shifts in the direction intersecting the axis of the rotation shaft 31, the rotation of the impeller 30 is stabilized. Thereby, the flow rate detection accuracy is further improved.

Further, since the N pole surface 240 of the second magnet 24 is formed in a spherical shape, the flow rate in the fluid passage 200 exceeds the preset maximum flow rate, and the dynamic pressure in the downstream direction applied to the impeller 30 is the above-described. When the impeller 30 is larger than the repulsive force of the second magnet 24, the impeller 30 maintains the N-pole surface 240 of the second magnet 24 and the N-pole surface 340 of the first magnet 34 while maintaining the repulsive force. It turns with point contact.
This not only reduces the rotational load of the impeller 30 but also suppresses the wear of the N pole surface 240 of the second magnet 24 and the N pole surface 340 of the first magnet 34 compared to the conventional one described above. Therefore, the flow rate detection accuracy can be maintained for a longer period.

[Others]
In the above embodiment, the short columnar first magnet 34 is fixed to the downstream shaft end 31b of the rotating shaft 31, but as shown in FIG. A rod-shaped first magnet 34 may be embedded at the tip, and the N pole surface 340 on the downstream end side of the first magnet 34 may be opposed to the N pole surface 240 of the second magnet 24.

  Further, like the impeller 30 shown in FIG. 3, the rotating shaft 31 itself is made of a magnetic material, and the downstream shaft end 31b is magnetized with the N pole and the upstream shaft end 31a is magnetized with the S pole. It may be. In this case, the rotating shaft 31 corresponds to the “rotation center” and the “first magnet” as the invention specifying matters of the first aspect.

Furthermore, in the above embodiment, the upstream end surface 240 of the second magnet 24 is formed into a spherical shape, and the downstream end surface 340 of the first magnet 34 is formed into a flat shape, but FIG. As shown, the upstream end surface 240 of the second magnet 24 may be formed in a planar shape, and the downstream end surface 340 of the first magnet 34 may be formed in a spherical shape, or as shown in FIG. The upstream end surface 240 of the second magnet 24 may be formed in a flat shape, and the spherical protrusion 341 may be provided on the downstream end surface 340 of the first magnet 34.
In this case, the entire spherical surface of the “downstream end surface 340” in FIG. 4A and the “spherical protrusion 341” in FIG. Part.

[Flow sensor 1B according to another embodiment]
The flow rate sensor 1 in the above embodiment includes shaft ends 31a and 31b of the rotating shaft 31 protruding from the root portion of the blade 32 to the upstream side and the downstream side, and the centers of the upstream side opening 20a and the downstream side opening 20b. Is supported by the bearing portions 21a and 21b provided in the shaft, but the impeller 50 can be rotated around the main shaft 41 fixed in the fluid passage 400 as in the flow rate sensor 1B shown in FIG. The thing of the structure inserted in the state may be sufficient.

The main shaft 41 has a downstream shaft end 41 b fixed at the center of the downstream opening 40 b of the casing 40, and extends to the upstream side of the fluid passage 400. A cylindrical second magnet 44 is fixed to the upstream shaft end 41c.
The upstream end face (here, the N pole face) 440 of the second magnet 44 is formed in a planar shape and faces the first magnet 54 described later.

  On the other hand, a sleeve 51 into which the main shaft 41 is inserted is formed at the center of rotation of the impeller 50, and a short columnar first magnet 54 is embedded at the upstream end of the sleeve 51. .

An end face (here, an N pole face) 540 on the downstream side of the first magnet 54 is formed in a spherical shape and faces the second magnet 44. That is, the opposing surfaces of the first magnet 54 and the second magnet 44 are set to have the same magnetic pole.
The “back end” on the upstream side of the sleeve 51 corresponds to the “rotation center” as the invention specific matter of the first aspect of the invention, and the entire surface of the “N pole surface 540” formed in a spherical shape. Corresponds to the “spherical convex portion” as the invention specifying matter of claim 3 described above.

A cylindrical support shaft 51a is projected from the upstream end of the sleeve 51 so as to be rotatable with respect to a bearing portion 41a formed at the center of the upstream opening 40a of the casing 40. It is supported.
In this configuration, the impeller 50 is connected to the rear end (first magnet) on the upstream side of the sleeve 51 by the repulsive force between the same magnetic poles of the N pole surface 440 of the second magnet 44 and the N pole surface 540 of the first magnet 54. 54 N pole surface 540) and its opposite surface (N pole surface 440 of the second magnet 44) are rotated without contacting each other, so that the flow rate detection accuracy is improved as in the above embodiment, and for a long time. The flow rate detection accuracy can be maintained.

  Further, since the N-pole surface 540 of the first magnet 54 is formed in a spherical shape, the impeller 50 is not limited to the above-described repulsive force even when the dynamic pressure in the downstream direction applied to the impeller 50 becomes larger than the above-described repulsive force. The N pole surface 440 of the second magnet 44 and the N pole surface 540 of the first magnet 54 are rotated in a point contact manner while the repulsive force is maintained, and thus, as in the above embodiment, further Flow rate detection accuracy can be maintained over a long period of time.

[Flow sensor 1C according to another embodiment]
Further, as in the flow sensor 1C shown in FIG. 6, a configuration in which the impeller 70 is rotatably inserted in the main shaft 61 fixed in the fluid passage 600 may be used.
The main shaft 61 has an upstream shaft end 61 a fixed at the center of the upstream opening 60 a of the casing 60, and extends to the downstream side of the fluid passage 600. A cylindrical second magnet 64 is fixedly provided at the center of the downstream opening 60b of the casing 60.
The upstream end face (here, the N pole face) 640 of the second magnet 64 is formed in a planar shape and faces the first magnet 74 described later.

On the other hand, a sleeve 71 into which the main shaft 61 is inserted is formed at the center of rotation of the impeller 70, and a short columnar first magnet 74 is embedded at the downstream end of the sleeve 71.
An end surface (here, N pole surface) 740 on the downstream side of the first magnet 74 is formed in a spherical shape and faces the second magnet 64. That is, the opposing surfaces of the first magnet 74 and the second magnet 64 are set to have the same magnetic pole.
Incidentally, the “downstream end portion” of the sleeve 71 corresponds to the “rotation center portion” as the invention specific matter of the first claim, and the entire surface of the “N pole surface 740” formed in a spherical shape is formed. This corresponds to the “spherical convex portion” as the invention specific matter of claim 3 described above.

  In this configuration, the impeller 70 is connected to the downstream end (first magnet 74) of the sleeve 71 by the repulsive force between the same magnetic poles of the N pole surface 640 of the second magnet 64 and the N pole surface 740 of the first magnet 74. The N-pole surface 740) and the opposite surface (N-pole surface 640 of the second magnet 64) are rotated without being in contact with each other. The flow rate detection accuracy can be maintained.

  Further, since the N-pole surface 740 of the first magnet 74 is formed in a spherical shape, the impeller 70 is not affected by the above-described repulsive force when the dynamic pressure in the downstream direction applied to the impeller 70 is larger than the above-described repulsive force. In this state, the N pole surface 640 of the second magnet 64 and the N pole surface 740 of the first magnet 74 are rotated in point contact with each other, so that the repulsive force of the second magnet 64 is maintained. Flow rate detection accuracy can be maintained over a long period of time.

1 is a schematic configuration diagram of a flow sensor 1 according to an embodiment of the present invention. Explanatory drawing of the 1st magnet 34 of the flow sensor concerning other embodiments of the present invention. Explanatory drawing of the impeller 30 of the flow sensor which concerns on other embodiment of this invention. Explanatory drawing of the 2nd magnet 24 and the 1st magnet 34 of the flow sensor concerning other embodiments of the present invention. Schematic configuration diagram of a flow sensor 1B according to another embodiment of the present invention. Schematic configuration diagram of a flow sensor 1C according to another embodiment of the present invention. Schematic configuration diagram of a conventional flow sensor 9

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Flow sensor 20 ... Casing 200 ... Fluid passage 24 ... 2nd magnet 30 ... Impeller 34 ... 1st magnet S ... Rotation detection means

Claims (3)

In a flow sensor comprising a casing having a fluid passage therethrough, an impeller that is pivotally supported in the fluid passage so as to be rotatable in the circumferential direction, and a rotation detecting means for detecting the rotation speed of the impeller.
A first magnet is provided at the center of rotation of the impeller,
A second magnet is provided at a position facing the first magnet from the downstream side of the fluid passage;
The flow rate sensor in which the opposing surfaces of the first magnet and the second magnet are set to the same magnetic pole. The flow sensor according to claim 1,
The first magnet is fixed to an end portion of a rotating shaft that protrudes from the impeller to the downstream side of the fluid passage, and the second magnet is fixed to a bearing portion that supports the end portion. The flow sensor according to claim 1 or 2,
A flow sensor in which a spherical convex portion is provided on the facing surface of either the first magnet or the second magnet.

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