JP2620202B2 - Electromagnetic flow meter detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic flowmeter detector, and more particularly to a small-diameter flangeless electromagnetic flowmeter detector.

[0002]

2. Description of the Related Art The structure of a conventional flangeless electromagnetic flow rate detector is shown in FIGS. FIG. 5 is a sectional view in a direction perpendicular to the axial direction of the measuring tube, and FIG. 6 is a sectional view taken along line YY ′ of FIG. In FIG. 5, the structure of the electromagnetic flow rate detector includes a measurement tube 1, an electrode 2, an exciting coil 3, a core 4, and a case 5. The measuring tube 1 is mounted on the axis of the exciting coil 3.
The excitation a of the core 4 extends to the inside of the excitation coil 3 along the outer peripheral surface. The magnetic pole dimension l ₂ is set to l ₂ = about 0.8D so as to obtain a magnetic flux distribution that reduces an error due to fluid drift. The exciting coil 3 is wound along the outer peripheral surface of the measuring tube 1 to the vicinity of the electrode 2 attached to the measuring tube 1. Although not shown, the outer diameter of the case 5 is determined by a flange standard so as not to hit the bolt case 5 of the piping flange. Thus the cross-sectional area of the excitation coil 3 is the inner diameter of the case 5, the outer diameter of the measuring tube 1, thus determined by the magnetic pole dimension l _2. The magnetic flux density generated by the magnetic field generating portion of the exciting coil 3 and the core 4 has a small number of turns in the limited cross-sectional area of the exciting coil 3, and the wire diameter of the exciting coil 3 is reduced to reduce the number of turns of the exciting coil 3. It is necessary to obtain a necessary value by either increasing the value or increasing the exciting current flowing through the exciting coil 3.

[0003]

However, in the prior art, when the diameter of the exciting coil 3 is reduced, the productivity and the resistance of the exciting coil 3 increase, and a high voltage is required to obtain a necessary exciting current. A method of obtaining a magnetic flux density by increasing the exciting current to a wire diameter of about the same size has been adopted. However, increasing the exciting current has a drawback that the power consumption is large because the power consumption is proportional to the square of the current, and that the power consumption of the converter that supplies the exciting current is also large.

An object of the present invention is to provide an electromagnetic flowmeter detector which can reduce power consumption without lowering the electromotive force generated by the detector and hardly cause an error due to drift of fluid.

[0005]

SUMMARY OF THE INVENTION The present invention provides a case, a cylindrical measuring tube housed in the case, and through which a measuring fluid flows.
A pair of electrodes provided on the measurement tube, a pair of magnetic pole plates provided on an outer periphery of the measurement tube, a core provided on an inner circumference of the case, a magnetic pole connecting the pair of magnetic pole plates and the core, An electromagnetic flowmeter detector including an excitation coil provided so as to be interposed between the pair of magnetic pole plates and the core, wherein the magnetic pole plate has a curved plate shape corresponding to the cylindrical measurement tube. And the axis passing through the pair of magnetic poles is Y
When the axial length of both the X-axis and Z-axis orthogonal to the Y-axis is smaller than any previous SL excitation coil, an arc shape said excitation coil also along the measuring tube of the cylindrical It is characterized by being wound. The electric
In the magnetic flowmeter detector, the outer diameter of the excitation coil is
Those formed larger than the diameter are preferred. Furthermore, the Y of the pole plate
Both the X-axis and Z-axis lengths perpendicular to the axis
Those formed larger than the magnetic pole are preferred .

[0006]

Next, the operation will be described. The pole plate has an X axis (l _{2 in} FIG. 1) orthogonal to the Y axis (YY ′ line in FIG. 1).
Direction) and the Z-axis (the axial direction of the measuring tube in FIG. 2) are both formed larger than the magnetic pole, so that the magnetic pole portion is formed small and the exciting coil is increased accordingly. While it is possible to form the magnetic pole portion, if the magnetic pole portion is formed small, there is a drawback that an error occurs due to the drift of the fluid. However, this point is that the magnetic pole plate is formed large as described above and the magnetic pole plate is substantially Can be compensated.
Further, the magnetic pole plate is formed such that the lengths in both directions of the X axis and the Z axis orthogonal to the Y axis are smaller than the exciting coil, that is, the magnetic pole plate is formed smaller as described above. With the structure that enables the size of the exciting coil to be formed sufficiently large, power consumption can be reduced without reducing the electromotive force generated by the detector.

In particular, according to the present invention, the shape of the pole plate is defined as a curved plate shape, its dimensions are defined as described above in the X-axis and Z-axis directions, and the exciting coil is formed in an arc shape. Leakage of magnetic flux from the end to the core can be almost eliminated, thereby reducing power consumption without lowering the electromotive force generated by the detector. In addition, outside the excitation coil
The diameter of the magnetic pole plate is larger than the inner diameter of the measuring tube.
Leakage of magnetic flux from the end to the core can be further eliminated,
The excitation efficiency of the excitation coil can be further increased .

An embodiment of the present invention will be described with reference to FIGS. First, the configuration of the present invention will be briefly described. A case 5, a cylindrical measurement tube 1 accommodated in the case 5 and through which a measurement fluid flows, and a pair of electrodes 2 and 2 provided in the measurement tube 1 are described.
And a pair of magnetic pole plates 6 provided on the outer circumference of the measuring tube 1.
6, a core 4 provided on the inner periphery of the case 5, and magnetic poles a connecting the pair of magnetic pole plates 6, 6 to the core 4.
and a, an electromagnetic flowmeter detector with an excitation coil 3 provided as interposed between the core 4 and the pair of pole plates 6,6, the pole plate 6,6, said Cylindrical shape
As well as a curved plate shape corresponding to the measurement tube 1, the pair of magnetic poles a, when the axis passing through the a and the Y-axis, the length of both the X-axis and Z-axis orthogonal to the Y-axis is either It is smaller than the previous SL exciting coil 3, the exciting coil 3 both before
It is characterized by being wound in an arc shape along the cylindrical measuring tube 1 . Further to the electromagnetic flow meter detector
In this case, the outer diameter of the exciting coil 3 is larger than the inner diameter of the measuring tube 1.
A well-formed one is preferred. Furthermore, the Y of the pole plates 6 and 6
Both the X-axis and Z-axis lengths perpendicular to the axis
It is preferable that the magnetic poles are formed larger than the magnetic poles a .

A pair of electrodes 2 are mounted on the diameter axis of the inner surface of the measuring tube 1. Mounted along. A core 4 covers the excitation coil 3 over the entire circumference outside the excitation coil 3, and a magnetic pole a of the core 4 extends to the inside of the excitation coil 3 on the axis of the excitation coil 3. A magnetic pole plate 6 is attached to the end face of the magnetic pole a along the outer peripheral surface of the measuring tube 1. Illustrated dimensions l ₂ is greater than the dimension l ₁ of the pole a, which is the same as the magnetic pole dimension l ₂ of the conventional structure diagram 5. That is, the cross-sectional area of the magnetic pole plate 6 is configured to be much larger than the cross-sectional area of the magnetic pole a.

A detector is constructed by fixing a case 5 having a restricted outer diameter to the outer peripheral surface of both side flanges C of the measuring tube 1 on the outer periphery of the core 4 by a full-circumferential welding similarly to the conventional structure. .

A measuring tube 1 flows a fluid to be measured, and an electrode 2 detects an electromotive force induced in the fluid. The excitation coil 3, the core 4, and the magnetic pole plate 6 are a magnetic field generating unit that applies a magnetic field to the fluid, and the case 5 seals the entire body with a waterproof seal.

The excitation coil 3, which is one of the magnetic field generation units,
As described above, the sectional area is limited by the inner diameter of the case 5, the outer diameter of the measuring tube 1, and the magnetic pole size, but the cross sectional area of the exciting coil 3 is increased by reducing the dimension l _{1 of the} magnetic pole a. Here, simply reducing the dimension l _{1 of the} magnetic pole a increases the error due to the drift of the fluid. However, by attaching the magnetic pole plate 6 having the dimension l ₂ larger than the dimension l ₁ of the magnetic pole a to the magnetic pole a, the magnetic pole a has a function of providing a magnetic field path similarly to the core 4 and the magnetic pole plate 6 becomes a substantial magnetic pole. In addition, errors due to fluid drift are eliminated.

The dimension l ₁ of the magnetic pole a having the same function as that of the core 4 may be twice as large as the flow of the magnetic flux of the core 4, but the mechanical dimensions for mounting the magnetic pole plate 6 and the productivity of the exciting coil 3 are reduced. Considering this, it was set to about 0.39D (D = measurement tube inner diameter).

Next, an increase ratio of the sectional area of the exciting coil 3 which is wider than that of FIG. 3 is obtained. FIG. 3 is a cross-sectional view of the exciting coil 3 before the exciting coil 3 of FIG. 1 is formed into a saddle shape, and its dimensions are as illustrated. Outer diameter 1.3D FIG. 1, the same outer diameter in Fig. 5, 0.9D is l ₂ dimensions (0.8D) of the length of the arc, the arc of 0.4D is l ₁ dimension (0.39D) , The increase ratio of the cross-sectional area of the exciting coil 3 becomes W ₂ / W ₁ .

[0015]

(Equation 1)

When the cross-sectional area of the exciting coil 3 increases by 2.25 times, the number of turns of the coil increases 2.25 times as much as the increase rate of the cross-sectional area of the exciting coil 3 when the coil wire diameter is fixed.

Next, while keeping the magnetic flux density constant, the ratio of power consumption is determined. The magnetic flux density is determined by the following equation (Equation 2). Here, B = magnetic flux density, N = coil winding number, I = excitation current, μg = attraction ratio of air, and lg = distance between magnetic poles.

[0018]

(Equation 2)

[0019] The magnetic flux density of the conventional type which does not increase the number of coil turns and B _0, can be expressed by the following equation (3). Where N ₀
= Conventional coil winding number, I ₀ = conventional exciting current.

[0020]

(Equation 3)

Next, assuming that B _{0 is} constant, the number of coil turns is 2.25 times (2.25 N ₀ ), and the exciting current at that time is I ₁ , the following equation (Equation 4) is obtained.

[0022]

(Equation 4)

The conventional power consumption P ₀ is P ₀ = I ₀ ² R ₀ (8) where R ₀ = conventional coil resistance, and the power consumption P ₀ ′ of this structure is P ₀ = ^{_{I 1 2 R 1 ...... (9}} ) where a coil resistance R ₁ = present invention structure.

Although the number of turns of R ₁ is 2.25 times greater than that of R ₀ , the resistance value of one turn is small and about 1.8 times that of R ₀ because only the inside of the coil is increased. Therefore R ₁ = 1.8
Since R ₀ , I ₁ = (1 / 1.8) I ₀ , the equation (9) is as shown in the following equation (5).

[0025]

(Equation 5)

From the equations (8) and (10), the power consumption is as follows. That is, the power consumption is reduced by 45%.

[0027]

(Equation 6)

The cross-sectional area of the exciting coil 3 in the axial direction of the measuring tube in FIG. 2 also becomes a limited space in the case 5, but the number of coil turns can be increased by attaching the magnetic pole plate 6 as in FIG. Can be. The pole plate 6 shown in FIG. 1 is attached to the pole a, but as shown in FIG.
The same effect can be obtained by attaching the magnetic pole plate 6, the magnetic pole a and the core 4 separately to the core 4 integrally with the core 4.

[0029]

According to the present invention, the shape of the pole plate is changed to a curved plate.
Shape and the dimensions are as described above for the X-axis and Z-axis directions.
And the excitation coil has an arc shape.
Magnetic flux from the end of the pole plate to the core
And reduce the electromotive force generated by the detector.
Power consumption can be reduced . Furthermore, the outer diameter of the exciting coil
Is larger than the inner diameter of the measuring tube,
The leakage of magnetic flux from the section to the core can be further eliminated,
The excitation efficiency of the magnetic coil can be further increased .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view in a direction perpendicular to a measurement tube axis of a detector for explaining an embodiment of the present invention.

FIG. 2 is a sectional view taken along line YY 'of FIG.

FIG. 3 is an explanatory view before the exciting coil 3 of FIG. 1 is formed into a saddle shape.

FIG. 4 is a cross-sectional view illustrating a modification of the embodiment of the present invention.

FIG. 5 is a cross-sectional view corresponding to FIG. 1 of a conventional type.

FIG. 6 is a sectional view taken along line YY ′ of FIG. 5;

[Explanation of symbols]

 1 Measuring tube 2 Electrode 3 Excitation 4 Core 5 Case 6 Magnetic pole plate a Magnetic pole c Measuring tube flange

Claims (3)

(57) [Claims] 1. A case, a cylindrical measurement tube housed in the case, through which a measurement fluid flows, a pair of electrodes provided on the measurement tube, a pair of magnetic pole plates provided on an outer periphery of the measurement tube, and the case. An electromagnetic flowmeter comprising: a core provided on the inner periphery of a magnetic pole, a magnetic pole connecting the pair of magnetic pole plates and the core, and an excitation coil provided so as to be interposed between the pair of magnetic pole plates and the core. In the detector, the magnetic pole plate has a curved plate shape corresponding to the cylindrical measurement tube, and when an axis passing through the pair of magnetic poles is a Y axis, an X axis orthogonal to the Y axis and the length of both the Z-axis is smaller than the previous SL excitation coil either, electromagnetic flowmeter detector, characterized in that also the exciting coil is wound in a circular arc shape along the measuring tube of the cylindrical shape. 2. An outer diameter of an exciting coil according to claim 1,
Electromagnetic characterized by being formed larger than the inner diameter of the measuring tube
Flow meter detector. 3. The magnetic recording medium according to claim 2, wherein the magnetic pole plate is perpendicular to the Y axis.
Both the X-axis and Z-axis directions are longer than the magnetic pole.
Flowmeter detection characterized by a large size
Bowl .