JP3347500B2 - Flow sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow sensor for measuring a flow rate by counting a pulse caused by the rotation of a rotating body provided in a flow path in a case body in a flow path in a case body.

[0002]

2. Description of the Related Art The above-mentioned flow sensor is disclosed in
As disclosed in Japanese Patent Publication No. 171802, a resin impeller as a rotating body or a sphere 20 as shown in FIG. 6 is subjected to a ferromagnetic surface treatment such as iron plating, and a permanent magnet 22 is provided outside the flow path 21. The magnetic field change caused by the rotation of the magnetic sphere 20 or the like is also
Is detected by a magnetic sensor 23 provided in the vicinity of. This is intended to solve the problem that the magnet is provided on the impeller or the like in the flow channel in the related art, so that iron powder in the fluid adheres to the magnet and causes malfunction.

[0003]

However, in the above flow sensor, since the magnet is arranged outside the flow path, it is easily affected by an external magnetic force other than that caused by the rotating body.
There is a problem that a magnetic sensor erroneously detects a pulse due to a change in an external magnetic field.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a flow sensor capable of performing reliable and highly accurate detection without being affected by changes in an external magnetic field, even if a magnet is arranged outside a flow path. The configuration is such that the rotation
Opened toward the body side, with a magnet, or a magnet and a yoke,
Magnetic circuit having magnetic sensor for detecting change in magnetic field
The flow sensor that constitutes the
While the impeller is made up of inner blades,
The contact area of the stone or yoke with the case body is
The contact area is larger than the contact area with the cer . Further, the magnetic circuit may be constituted by two bar-shaped magnets arranged in parallel with one end thereof facing the rotating body, and the magnetic sensor arranged between the other ends of the bar-shaped magnets. desirable. In addition, the bar-shaped magnet referred to in the present invention includes a plate-shaped or round bar-shaped magnet, and a magnet having a slight bent or bent portion.

[0005]

[Action] and impeller having magnetic rotation, the guide vanes of the impeller in a magnetic circuit which is open towards the impeller side is closest, wherein the magnet magnetic sensors closed circuit is configured to detect magnetic force When the guide vanes move away from the magnetic circuit, the magnetic force of the magnet detected by the magnetic sensor becomes weak. The magnitude of this magnetic force is obtained as a flow pulse. Further, since the magnet and the magnetic sensor constitute a magnetic circuit using only the guide blade as a factor for changing the magnetic force, the magnet and the magnetic sensor are hardly affected by an external magnetic field other than the rotation of the impeller . In particular, rotation
Since the body is an impeller consisting of multiple guide blades,
Many pulses are obtained regularly, and the detection accuracy is improved. Sa
In addition, the magnet or yoke in the magnetic circuit on the case body side
Area larger than the contact area with the magnetic sensor
The reaction to the impeller becomes more sensitive,
Good response to change. Further, when the magnetic circuit is composed of the two bar-shaped magnets arranged in parallel and the magnetic sensor, the magnetic force applied to the magnetic sensor in the closed circuit becomes stronger, and the strength of the magnetic force appears clearly.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1 and 2 are explanatory views showing a horizontal cross section and a vertical cross section, respectively, of the flow sensor 1. The upstream side (lower side in FIG. 2) of the cylindrical case main body 2 is provided with a central fixed shaft 3 and an inner wall of the case main body 2. The fixed guide blades 4 are formed radially and twisted helically, and are provided on the downstream side (upper side).
A ring body 8 provided radially from the shaft 5 and connected to the inner cylinder 7 by a plurality of fixing plates 6 and 6 parallel to the axis of the case body 2 is press-fitted. Also, the ring body 8 and the fixed guide vanes 4,
4 is a space storage room 9 in which a steel ball 10 is stored in a free state. Further, two bar-shaped magnets 11, 11 perpendicular to the axial direction of the case main body 2, which are located outside the case main body 2 and above the storage chamber 9, respectively apply the ends 11 a, 11 a of different poles to the outer surface of the case main body 2. A magnetic sensor 12 for detecting a change in a magnetic field using a Hall element is provided between opposite ends 11b, 11b of opposite poles which are arranged in parallel in contact with each other and bent slightly in the opposite direction. Thus, the magnetic circuit unit 14 is configured. In the flow rate sensor 1 configured as described above, the fluid flowing from the upstream becomes a swirling flow by the fixed guide blades 4 and 4, and the swirling flow gives a rotating motion to the iron ball 10 in the storage chamber 9. At this time, the iron ball 10 is pressed against the ring body 8 above the storage chamber 9 by the swirling flow, and a centrifugal force is also applied to the iron ball 10 as shown in FIG.
Rotate along the inner wall of the case body 2 as shown in FIG. When the iron ball 10 is located at the position A closest to the ends 11a of the bar-shaped magnets, the iron ball 10 becomes a yoke and the magnetic force between the ends 11b of the bar-shaped magnet on the magnetic sensor 12 side is the strongest. And conversely, the iron ball 10 is a bar-shaped magnet 11, 1
At a position away from 1, the magnetic force between the ends 11b, 11b is weak. Therefore, the magnetic sensor 12 outputs a pulse signal according to the strength of the Hall voltage generated by the magnetic force applied thereto, and the flow rate is measured by counting the pulse signal. Also, the bar-shaped magnets 11, 11 and the magnetic sensor 12
The magnetic circuit consisting of only the case body 2 side is opened,
Since the closed circuit is formed when the iron ball 10 is at the position A,
The factor of the magnetic force change in this magnetic circuit is only the iron ball 10, which makes it hard to be affected by an external magnetic field, thereby enabling highly accurate detection. Of course, the conventional effect that the rotating body is not magnetized so that iron powder does not adhere thereto and that the rotating body rotates along the inner surface of the case to improve the detection sensitivity can be maintained.

[0007] The magnetic circuit is not limited to the two rod magnets 11 and 11 and the magnetic sensor 12 as described above.
If a closed circuit including a rotating body as a part can be formed, as shown in FIG. 3, a partially open magnetic circuit can be formed by using one bar-shaped magnet 13 and a plurality of yokes 15, 15. Design changes are possible. Further, an electromagnet may be used instead of the rod-shaped magnets 11 and 13. Furthermore, in these magnetic circuits, if the contact area of the magnet and yoke on the case body side is made larger than the contact area on the magnetic sensor side, the reaction to the rotating body becomes more sensitive, and the response to changes in magnetic force It will be good. On the other hand, the rotating body is also formed of a magnetic material such as iron as shown in FIG.
If an impeller 17 composed of a plurality of guide blades 16 or 16 is used, or if the guide blades 16 and 16 are made of resin and a magnetic body is fixed to the tip thereof, the same effects as described above can be obtained, and more. Are obtained regularly, and the detection accuracy is improved. Even when the iron ball 10 is used, a plurality of pulses can be obtained in the same manner as described above by disposing the iron ball 10 between the guide blades 16a of the resin impeller 17a. Alternatively, the surface of the resin sphere or the guide vane may be plated with a magnetic material to reduce the weight.

[0008]

As described above, according to the present invention, the blade having magnetism
By configuring the magnetic circuit using only the vehicle as a factor of the magnetic force change, it is hardly affected by the magnetic field outside the case body, and the flow rate can be detected with high accuracy. Of course, the conventional effect that the impeller is not magnetized so that iron powder does not adhere thereto and that the impeller rotates in the state closest to the magnetic circuit to improve the detection sensitivity can be maintained. Especially with the use of impellers,
More pulses are obtained regularly to improve detection accuracy,
Contact of magnet or yoke with case body side in magnetic circuit
The contact area is larger than the contact area with the magnetic sensor
This makes the reaction to the impeller more sensitive,
The response is good.

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view of a flow sensor in the embodiment.

FIG. 2 is an explanatory longitudinal sectional view of a flow sensor in the embodiment.

FIG. 3 is an explanatory diagram showing a modified example of a magnetic circuit.

FIG. 4 is an explanatory view showing a modified example of a rotating body.

FIG. 5 is an explanatory view showing a modified example of a rotating body.

FIG. 6 is an explanatory view showing a conventional flow sensor.

[Explanation of symbols]

1. Flow sensor, 2. Case body, 3. Fixed shaft, 4. Fixed guide blade, 5. Shaft, 6. Fixed plate, 7
··· Inner cylinder, 8 ··· Ring body, 9 ··· Storage room, 10 ··· Iron ball, 11, 13 ··· Rod magnet, 12 ··· Magnetic sensor,
14. magnetic circuit unit, 15 yoke.

Continuation of the front page (56) References JP-A-62-168022 (JP, A) JP-A-2-107021 (JP, U)

Claims (2)

(57) [Claims] A flow path in a case body includes a rotating body having magnetism that rotates by a flow of a fluid, and is provided outside the flow path toward the rotating body side, and includes a magnet,
Is a flow sensor having a magnetic circuit having a magnet, a yoke, and a magnetic sensor for detecting a change in a magnetic field.
The rotating body is an impeller composed of a plurality of guide blades.
The magnet or yoke of the magnet in the magnetic circuit.
The contact area with the main body side is
A flow sensor characterized by being larger than the contact area . 2. The magnetic circuit includes two rod-shaped magnets arranged in parallel with one end facing the rotating body, and the magnetic sensor arranged between the other ends of the rod-shaped magnets. The flow sensor according to claim 1, wherein