JP2883928B2 - Area type flow meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an area type flow meter for measuring a flow rate of a fluid to be measured by a position of a float provided in a flow pipe.

[0002]

2. Description of the Related Art In a vertically disposed tubular flow path, a movable element, that is, a floating element having a specific gravity higher than that of a fluid to be measured, is provided in a vertically movable manner. A flow meter that has a structure in which the cross-sectional area of a passage is increased and flows a fluid from below to above a flow passage to obtain a flow rate from the position of a float is called an area flow meter, and is widely used in practice.

[0003] These are structurally broadly classified into two types shown in Figs. 8 and 9, and the type shown in Fig. 8 is a tapered flow pipe 1 having an open top.
There is a float 2 inside, and the one shown in FIG.
There is a ring-shaped throttle 4 inside, and the float 5 is formed in a tapered shape. In both types, the float rises as the flow increases, and the flow is measured by the height of the float.

If the flow passage tube is not translucent, a means for knowing the height of the float from the outside of the flow tube is required, and in order to output the flow rate as an electric signal, the height of the float is measured by an electric signal. Means for converting to signals are required. The conventional means for converting the height of the float into an electric signal is generally an indirect method of converting the amount of vertical movement of the float into an electric signal by a transducer connected to a mechanism outside the channel pipe by magnetic coupling. It is.

FIGS. 10 and 11 show typical examples, and FIG.
Numeral 0 designates a magnet 8 provided at the upper end of the float mounting shaft 6 in the tapered flow pipe 1, that is, at the upper end facing the lead pipe 7 provided at the upper end of the flow pipe. An arm 9 that follows and rotates is provided outside the flow path tube, and the flow rate is grasped by the rotation angle of the arm 9. FIG.
It is configured to convert the rotation angle of the rotor 12 that follows the direction of the line of magnetic force 11 created by the magnet into the rotation.

On the other hand, several types of means for directly extracting the height of the float as an electric signal without using a mechanism such as an arm or a rotor have been devised. To give an example,
FIG. 12 shows a differential transformer in which a coil 13 is wound around the upper lead pipe 7 of the tapered flow pipe 1 and a magnetic core 14 at the upper end of the lead pipe in the floating shaft 6 is a movable core.

FIG. 13 shows that a number of magnetically responsive switches 15 are arranged outside the straight flow pipe 3 in parallel with the flow pipe, and each switch is opened and closed by a magnet 16 in the float 5 which moves up and down, and is closed. In this configuration, the height of the float is obtained by detecting the position of the formed switch by scanning.

[0008]

The structure shown in FIGS. 10 and 11 has an advantage that the height of the float can be visually observed as the angular displacement of the shaft of the arm or the rotor, but the height of the float is obtained as an electric signal. For this purpose, it is necessary to provide a transducer for converting an angular displacement into an electric signal on the axis of the arm or the rotor, and its structure becomes complicated. In addition, since the arm and rotor follow the movement of the float with the attraction of the magnets, the frictional force of the suction acts on the float when the float moves up and down, reproducing the relationship between the height of the float and the flow rate. There is a problem that the property is deteriorated. Further, in the configuration shown in FIG. 12, the diameter of the coil differs for each diameter of the lead pipe of the flow path pipe, so that the productivity is poor, and the substantial magnetic permeability changes depending on the type and temperature of the fluid. However, the configuration shown in FIG. 13 requires a number of magnetically sensitive switches to obtain high resolution, is difficult to mount, and has high costs. No.

The present invention eliminates the above-mentioned drawbacks of the conventional structure, has a simple structure for extracting the position of the float as an electric signal, can reduce the manufacturing cost, and yet has a highly accurate and reliable area type flowmeter. Available now.

[0010]

The area type flow meter according to the present invention is provided with a float having a specific gravity larger than that of the fluid to be measured in a vertical flow pipe so as to be movable up and down. The structure is such that the flow path area in the flow path tube changes accordingly, and in an area type flow meter that measures the flow rate when the fluid flows from the bottom to the top in the flow path by the position of the float, it is magnetized in the direction of movement of the float. A magnet that produces magnetic lines of force that are substantially axisymmetric about an axis parallel to the direction of movement of the float is provided at the float or at a portion cooperating with the float, and a flat surface perpendicular to the axis of symmetry of the magnet is provided.
Outside the flow tube on the plane and at approximately the same distance from the axis of symmetry
Section has a plurality of Hall elements, and among these Hall elements
For at least two Hall elements, the sensitivity of the Hall element
The angle formed by the magnetic surface and the axis of symmetry of the magnet is different from each other, and the flow rate is obtained by obtaining the vertical relative position between the plane on which the Hall element is provided and the magnet from the magnetic flux density signals detected by these Hall elements . Continuous
Are you in so that is measured.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to FIGS. 1 to 3 show the principle of the present invention. In FIG. 1, a magnet 23 vertically magnetized is provided at the float 22 or at a position vertically displaced in the flow pipe 21 in accordance with the flow rate together with the float. The magnet has an axially symmetric shape with respect to an axis L parallel to the moving direction, and the magnetic flux density has an axially symmetric distribution with respect to the axis of symmetry L.

That is, as shown in FIG. 1, at a point on the circumference 25 which is on the plane 24 orthogonal to the axis of symmetry and is at an equal distance from the axis of symmetry, the magnetic flux density E on the plane perpendicular to the line of magnetic force 26, The angle between the line of magnetic force and the axis of symmetry, that is, the tangent angle φ of the line of magnetic force is equal at any point.

The geometric shape of the magnetic field lines of the magnet magnetized only in one direction hardly changes even if the magnetic force of the magnet slightly increases or decreases.
The tangent angle φ of the magnetic force line at the upper point is always kept substantially constant even if the magnetic force of the magnet slightly changes due to a temperature change or the like, and the tangent angle φ is determined by the relative position h between the plane in FIG. .

That is, when FIG. 1 is viewed from the side, FIG. 2 is obtained. When the relative position h is changed while keeping the radius r of the circumference constant, the tangent angle φ of the magnetic force line corresponds to h as shown in FIG. Will change. This condition does not change even if the float rotates about the center axis, provided that the center axis of the float matches the symmetry axis of the magnet.

The gist of the present invention is to utilize the physical properties of the magnet described above to determine the tangent angle φ of the line of magnetic force, thereby detecting the position of the magnet, ie, the float, determining the height of the float, and determining the flow rate. Is to be measured.

Hereinafter, embodiments of the present invention will be described in detail. The radius r is selected so that the circumference of FIG. 1 is located outside the flow path tube made of a non-magnetic material, and two e having uniform characteristics on this circumference.
A rule element is provided.

As shown in FIG. 5, one Hall element A is provided with its magnetically sensitive surface perpendicular to the symmetry axis of the magnet, and the other Hall element B is provided with its magnetically sensitive surface parallel to the symmetry axis of the magnet. A signal conversion circuit is provided for each of these so that these outputs A _O and B _O have a gain K that is proportional to the magnetic flux density on the magneto-sensitive surface of the Hall element and equal. That is, the magnetic flux densities on the magneto-sensitive surfaces of the elements A and B are represented by E _A ,
Assuming that E _B , A _O = K · E _A and B _O = K · E _B hold.

Since the angle φ between the line of magnetic force and the axis of symmetry at a point on the circumference and the magnetic flux density E on the plane perpendicular to the line of magnetic force are constant at all points on the circumference as described above, the output A
_O, B _O is determined by the angle of the sensitive surface and the magnetic field lines of the Hall _{element, A O = K · E A} = K · Ecosφ B O = K · E B = K · Esinφ However, K: be represented by a constant it can.

The magnetic flux density E from the above equation thus, clearing the constants _{K, B O / A O =} tanφ ········ (1) φ = tan -1 (B O / A O) ··· (2) where the angle φ of the line of magnetic force is determined from the outputs A _O and B _{O of the} two Hall elements , regardless of the magnetic flux density E, and based on the plane 24 provided with the Hall elements as described above. Ma
The relative position h of the gnet is determined. In addition, Hall element
Using a magnetoresistive element instead of
Since the output is a scalar without polarity (positive or negative),
You can know the distance between the element and the magnet,
Is the magnet above or below the magnetoresistive element?
Cannot be determined, and the vertical position of the magnet is determined.
To separate them, it is necessary to provide a separate electronic circuit
You. However, the output of the Hall element in the flow meter of the present invention
A _O and B _O have polarities (positive and negative), and are positive in the direction of the magnetic field lines.
Since the vector quantity changes the polarity of the polarity in reverse,
The magnet 10 moves up and down with respect to the plane 24 on which the
The output is determined by the sign of the output.
It is not necessary to provide another electronic circuit for discriminating
No.

As is apparent from FIG. 2, when applied to a flow meter, h changes by several centimeters, so that the magnetic flux density E at the sensor installation point greatly varies depending on the height h. Therefore, even if the magnetic flux density greatly changes as in the present invention, it cannot be put to practical use unless the angle φ of the lines of magnetic force is accurately determined.

Since the relationship between φ or tan φ and the position h of the magnet depends on the specifications of the magnet and the position (radius r) of the Hall element, it is known by performing calculations or experiments in advance. Therefore, when used in a flow meter, by obtaining the signal outputs A _O and B _O from the Hall elements and performing the calculation of the above equation (1) or (2), φ is obtained and the position h of the magnet is obtained.

[0022] or more signal processing and calculation is readily performed when using analog-digital converter and a microprocessor, also because it is easy to perform the linearization processing on the signals from the Hall elements, Hall The signal output of the element itself does not necessarily have to be proportional to the magnetic flux density.

In a normal area flow meter, the relationship between the height of the float and the flow rate is generally non-linear, and varies depending on the specification of the fluid. Therefore, a complicated calculation is required when obtaining the flow rate from the position h of the magnet. However, these operations can be processed by a common microprocessor, which is extremely advantageous in terms of cost.

In addition to the above embodiment, the present invention is also effective in the following embodiments.

(1) Position of the magnet Since the magnet may be moved up and down integrally with the float,
It does not have to be in the flow path pipe as shown in FIG. 6, or even in a position eccentric from the center axis of the float as shown in FIG.
In short, it may be provided at a portion that cooperates with the float.

[0026] (2) In the angle embodiment of the Hall element, is used a Hall element perpendicular Hall element parallel to the axis of symmetry of the magnet, the angle with respect to the two axes of symmetry of the magnetic sensitive surface of the Hall elements from each other if not equal, (it may not be parallel and vertical) which can be determined the angle φ of the principle of magnetic force lines.

(3) Number of Hall Elements At least two Hall elements are required, but more than two may be used. In particular, as shown in FIG.
Using two sets of Hall elements (total of four), each axially symmetric pair A
The average output of A ₁ , A ₂ and B ₁ , B ₂ is determined, and A _O , B
_{When O} is set, there is an advantage that even when the magnet moves in the horizontal direction, a difference occurs in the angle of the magnetic field lines at the installation point of the Hall element , the error factors cancel each other out, and high accuracy can be maintained. When the output of one Hall element is small, it is possible to increase the detection sensitivity by providing a plurality of Hall elements having the same angle between the symmetry axis and the magneto-sensitive surface, and taking the sum of these outputs. is there.

[0028] (4) When the position Hall element of the Hall element is two, and ideally is optimal the same place, it is desirable generally to close the small hall element dimensions are installed. However, as long as the amount of horizontal movement of the magnet is smaller than the distance between the magnet and the Hall element , it may be anywhere on the circumference of FIG.

(5) Material of Flow Pipe The flow pipe may be made of any material as long as it is made of a non-magnetic material. When the fluid is at a high or low temperature, a heat insulating structure may be provided on the outer periphery of the flow pipe, and a Hall element may be placed outside the heat insulating structure.

[0030]

The flow meter of the present invention described above has the following effects. (a) It is sufficient to use at least two general-purpose Hall elements , which is advantageous in cost. (b) Since the Hall element is small and takes up little space, the entire flowmeter can be made compact. (c) Since the attractive force of the magnet does not act on the float,
There is no frictional force caused by the suction force, and it is excellent in accuracy. (d) Even if the magnetic force of the magnet changes due to temperature change, aging, etc., it does not affect the accuracy of the flowmeter. (e) Since a heat insulating structure can be provided between the channel tube and the Hall element , the applicable fluid temperature range is wide. (f) The output of the Hall element has polarity (positive or negative)
It is a vector quantity whose polarity changes depending on the direction.
In, the magnet bets is vertical to the plane in which a Hall element
It can be determined by the sign of the output.
It can, have not necessary to provide another electronic circuit for vertical determination
There are also advantages.

[Brief description of the drawings]

FIG. 1 is a basic principle diagram of the present invention.

FIG. 2 is a magnetic flux distribution diagram.

FIG. 3 is a diagram showing a relationship between a position of a magnet and a tangent angle of a line of magnetic force.

FIG. 4 is a diagram showing a basic mode of the present invention.

FIG. 5 is a diagram of a first embodiment of the present invention.

FIG. 6 is a diagram showing a second embodiment of the present invention.

FIG. 7 is a diagram showing a third embodiment of the present invention.

FIG. 8 is a principle diagram of an area type flowmeter using a tapered tube.

FIG. 9 is a principle diagram of an area type flow meter using a straight pipe.

FIG. 10 is an example of a conventional example in which the position of a float is captured by a magnetic coupling using a tapered tube.

FIG. 11 is an example of a conventional example in which the position of a float is captured by a magnetic coupling in a straight pipe.

FIG. 12 is a diagram showing a conventional one in which the position of a float is captured by a transducer.

FIG. 13 is a diagram showing a conventional one in which the position of a float is captured by scanning means.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 Flow pipe 22 Float 23 Magnet 24 Plane 25 Circumference 26 Line of magnetic force L Symmetry axis

Claims (1)

(57) [Claims] 1. A float having a specific gravity greater than that of a fluid to be measured is provided in a vertical flow pipe so as to be movable up and down, and the flow area in the flow pipe changes as the float moves. In an area type flowmeter that measures the flow rate when a fluid flows from the bottom to the top in a flow path by the position of the float, the area-type flowmeter is magnetized in the direction of movement of the float, and is substantially axial with respect to the axis parallel to the direction of movement of the float. provided a magnet to produce a symmetrical magnetic field lines cooperating portion between the float or float, the axis of symmetry of the magnet
Flows on a vertical plane and at approximately the same distance from the axis of symmetry
A plurality of Hall elements are provided outside the duct,
Holes for at least two Hall elements
The angle formed between the magneto-sensitive surface of the element and the axis of symmetry of the magnet is different from each other, and the vertical relative position between the plane on which the Hall element is provided and the magnet is obtained from the magnetic flux density signals detected by these Hall elements . area flow meter flow rate was so that continuously measured by.