JPH0792395B2 - Area type flow meter with sensor and flow rate measuring method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an area type flow meter,
The present invention relates to a sensor used for recording control of flow rate, remote measurement, and the like.

[0002]

2. Description of the Related Art An area type flow meter measures a flow rate by directly holding a graduated taper pipe and suspending a float by the flow. Therefore, it is widely used as a flow meter. By the way, there are many cases where it is desired to output the flow rate as an electric signal for the purpose of recording the flow rate on a recorder, automatic control, remote measurement, etc. However, there is no definitive one in the area type flow meter at present.

A method of detecting light by blocking the float is well known, and a method in which a single light receiving element is used to follow the float by a servo mechanism, and a plurality of light receiving elements are arranged to detect the position of the float. There are things. This method is excellent in accuracy, but has a drawback that it can be applied only to a transparent fluid. Therefore, although a flow meter of a gas body is good, a flow meter of water, which is most in demand in the case of a liquid, has a problem that the moving body becomes uncertain even if a small amount of water scale adheres to the inside of the tapered pipe.

It is known that a differential transformer is used as a material applicable to an opaque fluid, and this is an iron core of a differential transformer in which a rod is connected to a float and is provided outside the flowmeter. Is bound to. However, this method has a problem that the structure is complicated and there is a large error at a small flow rate due to the reaction reaction force of the differential transformer.

Therefore, various sensors have been proposed and put into practical use. For example, JP-A-62-954
Japanese Unexamined Patent Publication No. 25 discloses a structure in which a ferromagnetic body is used for the float and a plurality of pairs of an exciting coil and a detecting coil are arranged along a tapered tube. This is to know which detection coil position the float exists from the waveform of the voltage generated in the detection coil by passing a rectangular wave excitation current through each excitation coil.

The inventor of the present invention previously disclosed in Japanese Patent Laid-Open No. 3-18832.
The flowmeter described in Japanese Patent No. 4 was invented. In this system, exciting coils that generate magnetic fields in opposite directions are provided at both ends of the taper tube, an alternating current is passed through the coil, and the phase of the voltage induced in the detection coil wound around the taper tube is detected. That is, if an electric conductor such as aluminum is used for the float, an eddy current is generated, so that the magnetic field in this portion is delayed in phase. However, since the magnetic field itself differs depending on the distance from the exciting coil,
Since the phase of the voltage generated in the detection coil also changes according to the position of the float, this is detected.

[0007]

However, in the technique disclosed in Japanese Patent Laid-Open No. 62-95425, not only the pair of exciting coils are arranged along the taper tube, but also an outer cylinder of a ferromagnetic material is provided outside thereof. Since it is necessary to provide the device, the size of the device becomes large. In addition, it is difficult to arrange many coils closely, and there is a limit to the measurement accuracy.

On the other hand, the method disclosed in Japanese Patent Laid-Open No. 3-188324 can obtain a continuous output over the entire flow rate range and can detect a minute change in the flow rate, but the temperature error is rather large and the influence of the temperature is compensated in order to improve the accuracy. I need to do it. Therefore, a device that can measure the flow rate of an opaque fluid without a temperature error with a simpler device is desired.

[0009]

DISCLOSURE OF THE INVENTION The present invention is to solve the above-mentioned problems and provides an area type flow meter in which a float is suspended in a vertically placed taper tube and the flow rate is measured by its position. As a float, use a vertically magnetized permanent magnet or one that encloses it.
Multiple magnetoresistive elements can be magnetized by each magnetoresistive element.
The two directions with the maximum sensitivity to the
It is an area type flow meter with a sensor, which is arranged in parallel with the taper pipe so as to form an angle of 45 degrees with the axis of the pipe .

Further, here, a magnetoresistive element that stores a magnetic field and retains the stored state until a magnetic field in a direction different from the previous one is used, and the magnetoresistive elements are perpendicular to each other and have maximum sensitivity to the magnetism. Based on the position where each of the two directions forms 45 degrees with the axis of the taper tube,
It is also characterized in that the operation gap of the float position detection is adjusted by rotating from now on. Further, the storage area in the magnetic field direction of each magnetoresistive element is discriminated to output either a constant voltage or a zero voltage, and the flow rate is measured by the added value of the output voltages. This is a flow rate measuring method using a flow meter.

[0011]

In the area type flowmeter with sensor of the present invention,
As the float, a vertically magnetized permanent magnet or a permanent magnet enclosed in plastic or the like is used. The magnetic field generated by this is detected by arranging a plurality of magnetoresistive elements in parallel with the taper tube.

As a magnetic sensor, the above-mentioned Japanese Patent Laid-Open No. 62-62
There is a solid-state magnetic sensor in addition to the coil-type magnetic sensor used in the device of Japanese Patent Publication No. 95425. Hall elements and magnetoresistive elements are available as the elements of the solid-state magnetic sensor, but the hall element is often used as a general magnetic field detection means. This is considered to be largely due to the inherent polarity discrimination function. On the other hand, since the magnetoresistive element uses the simple principle that the electric resistance of metal or semiconductor changes depending on the magnetic field, it does not inherently have the function of discriminating the polarity of the magnetic pole. Area flow meter flow
Is designed to rotate freely around a vertical axis,
Therefore, in the case of the present invention, the direction of the magnetic pole of the magnet is in the vertical direction.
I have to do it. Therefore, only one pole of the magnet is
Located at the peak of the magnetic field due to this towards the row of anti-elements
The simple method of detecting the magnetoresistive element cannot be taken.
Therefore, use a magnetoresistive element that does not have the ability to determine the polarity.
In this case, for example, separate magnetic resistance elements are used to detect the N pole and S pole.
Discriminate what was put out in some way and check the position of the float
Must be a signal.

Here, in the present invention, a magnetoresistive element is used, but it has been found that the magnetoresistive element has a higher sensitivity in a weak magnetic field than a Hall element and is particularly suitable for the device of the present invention. That is, even if they are provided close to each other, there is no problem of malfunction due to mutual interference, and the fact that there is no polarity discrimination function is because there is no drawback due to the devised usage method in the present invention.
The magnetoresistive element includes one using a semiconductor and one using a ferromagnetic material as the material of the element. In the case of a semiconductor, the electric resistance increases due to the application of a magnetic field, but in the case of a ferromagnetic material, the mechanism of the change in the electric resistance is different, and there is a difference in the characteristics accordingly. For the purpose of the present invention, a material using a ferromagnetic material is particularly suitable because it has a high sensitivity in a low magnetic field and, as will be described later in detail, a memory operation is possible due to the magnetic hysteresis of the ferromagnetic material.

FIG. 2 is a diagram showing a resistor inside the magnetoresistive element. In this way, resistors 10A and 10B having the same characteristics are arranged so that the magnetic flux detection directions X and Y are different by 90 degrees. That is, in the case of a ferromagnetic magnetoresistive element, the magnetic field in the X direction is detected by the resistor of 10 A and the magnetic field in the Y direction is detected by the resistor of 10B because it has sensitivity when the current direction and the magnetic field direction are the same. It This is for temperature compensation, and the influence of temperature can be canceled by measuring the magnetic field with the voltage division ratio when current is passed in series through the two resistors. Therefore, even when measuring a magnetic field in one direction, one having sensitivity in two directions is used, and one element is used as a dummy for temperature compensation.

FIG. 3 shows an example of the circuit at this time.
B is a resistor of the magnetoresistive element 1, and 11A and 11B are resistors provided outside. In this way, a bridge circuit is formed so that a current is passed between the terminals 12 and 13 and the output between the terminals 14 and 15 is set to zero when there is no magnetic field. As a result, if a magnetic field that changes the electrical resistance of one of the resistors 10A and 10B is applied, the terminals 14 and 1
A voltage will appear between the five. Note that some magnetoresistive elements include all the resistors 10A, 10B, 11A, and 11B in FIG. 3 as internal elements.
0A, 11B and 10B, 11A detect magnetic fields in the same direction. Such a material can also be used in the present invention.

FIG. 1 is a diagram showing the principle of an area type flow meter with a sensor according to the present invention. Reference numerals 1A, 1B, 1C, 1D and 1E are magnetoresistive elements which are sensors, and only a part thereof is shown in this figure. . Further, 2 is a taper tube of a flow meter, and 3 is a float in which a magnet 4 is enclosed. In the present invention, the fact that the magnetoresistive element has sensitivity in two directions as described above is utilized to perform reliable detection of the float position. That is, as shown in FIG. 1, the magnetoresistive elements 1A to 1E are arranged so that two mutually perpendicular directions X and Y having the maximum sensitivity to the magnetism of the magnetoresistive element are 45 degrees with respect to the axis of the taper tube 2. Deploy. The magnetoresistive element generally has a shape in which a cube or a rectangular parallelepiped of several mm square is plastic-molded, and there is a magnetoresistive element having the maximum magnetic sensitivity in each diagonal direction of one surface of this outer shape. FIG. 1 shows a case where such a magnetoresistive element is used, and it can be arranged so as to be almost intimately overlapped with an adjacent element. Of course, it is also possible to use the ones that have the maximum sensitivity in the directions parallel to the two sides of the outer shape, and although it takes a little time to work, the individual magnetoresistive elements are mounted side by side in the state rotated by 45 degrees in the plane of the drawing from the position in FIG. Just do it.

As described above, by arranging the magnetoresistive elements as the sensors, the electric resistance changes in the sensor near the permanent magnet of the float, and the position of the float can be known by detecting this. That is, in FIG. 1, the magnetic field generated by the float permanent magnet 4 is generated as indicated by F, and therefore the magnetic resistance element of 1B detects the magnetic field in the X direction (the direction does not matter because polarity is not determined). Then, the magnetic field in the Y direction is detected. In the meantime, the 1C magnetoresistive element is in a neutral state because the magnetic fields in the X and Y directions have almost the same strength. On the other hand, when the magnetic resistance element 1B is separated from the element 1A, the magnetic field X is slightly deviated from the direction of the magnetic field X, and the Y direction is slightly increased. This tendency is further increased in the element further away, but the magnetic field itself is weakened.
The detection states in the X direction and the Y direction are never reversed. The same applies to the opposite element 1E and the element further away.

As a means for detecting the position of the float, for example, the outputs of the elements may be sequentially checked to detect which number of the elements the output appears to change. To perform this method automatically, signal processing may be performed digitally using a microcomputer or the like. As a simple display function, for example, lamps and light-emitting diodes can be arranged as many as the number of sensors and only the sensor having an output can be turned on. For industrial instruments, analog display,
Since recording is often required, the digital signal is D / A converted.

Further, as a suitable method for directly obtaining an analog signal, it is preferable to use a magnetoresistive element for storing the direction of the magnetic field. This uses a ferromagnetic thin film having a large residual magnetic flux density as an element, and the magnetization is retained and stored by the magnetoresistive effect. Therefore, if you store a magnetic field in a certain direction to maintain a certain output from the sensor and then add a magnetic field in another direction with a strength that cancels it, the previous memory state will be restored and the output from the sensor will be different. It becomes the state of.

By using the magnetoresistive element for storing the direction of the magnetic field as a sensor in this way, when the float rises from the bottom to the top in FIG. 1, a magnetic field in the Y direction is generated in each sensor below the float. When the float returns from the top to the bottom, the memory of the magnetic field in the Y direction is erased and the magnetic field in the X direction is stored.
In this case, when the float moves from the bottom to the top and when the float moves in the opposite direction, there will be some deviation in the operating position corresponding to the length of the magnet, but there is some operating gap. It is preferable that chattering does not occur in the upper and lower portions of the float.

Regarding the operating clearance, the directions X and Y having the maximum sensitivity of the magnetoresistive element are set to 45 with the axis of the taper tube.
It has been experimentally confirmed that it is possible to adjust in the direction of narrowing by rotating and shifting from the degree position. Therefore, if there is a demand to reduce the operation gap, it is possible to design it accordingly.

In this way, for example, if a high level output is detected from the magnetization in the Y direction and a low level output is detected from the magnetization in the X direction, it is possible to output digital signals from the circuits of the magnetoresistive elements. The circuit makes it possible to indicate which sensor position has the float. Further, if the output voltage is set to a constant voltage V in the high level state and zero in the low level state, and the output from each magnetoresistive element is input to the adder circuit, the nth from the bottom is obtained. If there is a float at the sensor position, n × V output is obtained. Therefore, an analog output can be directly obtained without using a D-A conversion circuit, which simplifies the circuit and is preferable in terms of device reliability.

In storing the position of the float, in addition to the above-mentioned magnetoresistive element itself having a storage function, a flip-flop circuit or the like may be provided and stored for each magnetoresistive element. In the storage of the magnetic field direction of each magnetoresistive element in the present invention, the storage by the storage function added to the outside of the element is not excluded. However, the method using the magnetoresistive element itself having a memory function is excellent because the memory operation is performed even when the element is not energized. That is, even if the flowmeter is started to operate with the fluid already flowing into the flowmeter and the float is floating, the flowmeter will operate normally, and there is no problem even if the power supply to the flowmeter is interrupted while the flowmeter is in use. .

[0024]

[Example] The moving distance of the float in the measuring range is 60
The flow rate was measured using the sensor of the present invention in an area flow meter of mm. As shown in Fig. 1, the float has a length of 10
A mm permanent magnet was enclosed, and 32 magnetoresistive elements were mounted side by side along the taper tube over the measurement range. The magnetoresistive element has a function of storing the direction of the magnetic field, and four resistors are connected to the bridge as shown in FIG. It has a characteristic of being magnetically saturated in a magnetic field of about 0.02T.

FIG. 4 is a diagram showing a circuit for measuring the flow rate, in which the number of sensors and the like are omitted. 20A to 20H are sensors, that is, magnetoresistive elements, and the power input terminals are omitted. The output from each sensor is the comparator 21A.
When the output from the sensor is in the state where the magnetic field in the Y direction is detected, a constant voltage is output, and when the magnetic field in the X direction is detected, the output is zero.

The outputs of these are input to the operational amplifiers 23A and 23B and added. 22A-22H and 24A, 24B
Is a calculation resistance. In FIG. 4, operational amplifiers 23A, 23
This is because two Bs are used, but if the outputs from all the sensors, for example, 32 sensors are added by one operational amplifier, the linearity becomes worse. In this embodiment, the outputs from the 32 sensors are divided into 8 outputs and input to 4 operational amplifiers. Further, similarly, each of these operational amplifiers 23
The outputs of A and 23B are added by the operational amplifier 25 and finally become one output.

As a result, an output proportional to the number of sensors below the float position can be obtained. Generally, the input and output of the industrial measuring instrument is a signal having a full scale between 4 mA and 20 mA DC, and therefore the voltage output from the operational amplifier 24 may be further converted by the current output conversion circuit. In this way, in this embodiment using 32 sensors, a good linearity is obtained in the relationship between the position of the float and the output current, and there is virtually no temperature error, and a flow signal generator having excellent characteristics is obtained. Was given.

[0028]

According to the present invention, a permanent magnet is used for the float of the area type flow meter, and the magnetic field of the permanent magnet is detected by a magnetoresistive element. The magnetoresistive element has a good detection sensitivity in a low magnetic field, and a small element is closely attached. Even if they are arranged side by side, there is no mutual interference, and it is preferable to use the function of detecting the magnetic fields in two directions so that the float position can be surely detected. Further, since the element itself has a temperature error compensating circuit, there is no problem of temperature error.

If a magnetoresistive element that stores a magnetic field and continuously outputs an output is used, the output voltage is output from, for example, all the sensors below the float position as a boundary. Zero output can be obtained from the upper sensor, and the float position can be directly obtained as an analog output by adding outputs from all the sensors. Therefore, it is possible to obtain an analog signal that is generally required as an industrial instrument with a relatively simple circuit, and the magnetic resistance element of the sensor itself is a mass-produced product and is relatively inexpensive. A generator can be obtained, and the industrial benefit is great.

[Brief description of drawings]

FIG. 1 is a diagram showing a main part of an area type flow meter with a sensor according to the present invention.

FIG. 2 is a diagram showing a configuration of a magnetoresistive element.

FIG. 3 is a diagram showing a circuit of a magnetoresistive element.

FIG. 4 is a circuit diagram showing an example of a flow rate measuring method of the present invention.

[Explanation of symbols]

 1, 1A, 1B, 1C, 1D, 1E Magnetoresistive element 2 Tapered tube 3 Float 4 Magnet 10A, 10B Magnetoresistive element

Claims (1)

[Claims] 1. An area type flow meter in which a float is suspended in a vertically placed taper tube and the flow rate is measured by the position of the float, wherein a permanent magnet magnetized in the vertical direction as the float or a magnet in which the magnet is enclosed. And use multiple magnetoresistive elements for the magnetism of each magnetoresistive element.
Two directions at right angles to each other with maximum sensitivity are tapered tubes
An area type flow meter with a sensor, which is arranged in parallel with the taper pipe so as to form an angle of 45 degrees with the axis . 2. An area type flowmeter with a sensor according to claim 1, wherein a magnetic field element is used as a magnetoresistive element that stores a magnetic field and retains the memory state until a magnetic field in a direction different from the previous direction is applied. 3. An operating gap for float position detection by rotating from the position where two mutually perpendicular directions having maximum sensitivity to magnetism of the magnetoresistive element form 45 degrees with the axis of the taper tube. The area type flow meter with a sensor according to claim 1 or 2 , characterized in that: 4. The magnetic state of each magnetoresistive element is discriminated from each other to output a constant voltage or a zero voltage, and the flow rate is measured by the added value of the output voltages. A flow rate measuring method using the area type flow meter with a sensor according to 1 , 2, or 3 .