JPH0670574B2 - Flowmeter - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow meter, and more particularly to a flow meter configured to detect rotation of a rotor with a magnetic sensor.

2. Description of the Related Art A positive displacement flow meter is widely used as a flow meter for measuring the flow rate of fluids such as petroleum, food and chemical liquids. In this type of positive displacement type flow meter, a pair of rotors composed of elliptical gears are rotatably provided in the measuring chamber of the casing body, and as the fluid passes through the measuring chamber, the rotor is rotated according to the volume of the fluid passing through. Is configured to rotate. The rotation of the rotor is electromagnetically detected by a magnetic sensor such as a magnetoresistive element when a magnet embedded in the rotor passes, and the flow rate at that time is based on the signal output from the magnetic sensor. Is calculated. Depending on the piping path in which the positive displacement flow meter is installed, the fluid to be measured that has passed through the flow meter may flow backward. When such a reverse flow occurs, the rotor rotates in the reverse direction, so that the magnetic sensor outputs a signal according to the reverse rotation of the rotor as in the case of the normal rotation of the rotor.

Therefore, in the above flow meter, the measured flow rate is measured again each time a backflow occurs, which causes a measurement error.

Therefore, it is considered to detect whether the rotor is rotating normally or reversely and correct the measurement error due to the reverse flow. As a method of detecting the rotation direction of the rotor, for example, a method of using a two-phase magnetic sensor to find the phase difference between the output signal of the A phase and the output signal of the B phase caused by the rotation direction of the rotor is considered. . However, the two-phase magnetic sensor consumes a large amount of current and needs to be supplied with electric power from the outside. For example, when a flow meter is installed in a place where there is no power outlet nearby, such as in a large factory, it is possible to determine the reverse flow of the fluid to be measured. Therefore, there arises a problem that accurate flow rate measurement cannot be performed.

Then, this invention aims at providing the flowmeter which solved the said subject.

Means for Solving the Problems The present invention provides a rotor that rotates at a rotational speed according to the flow rate of a fluid to be measured, and the rotor that is provided coaxially with the center of rotation of the rotor and that extends in the circumferential direction. An annular magnet in which N poles and S poles are alternately formed, and a detection end portion is provided so as to extend in the circumferential direction of the magnet,
A first magnetic sensor that detects a change in the magnetic field of the annular magnet due to the rotation of the rotor to generate a first output signal; and a position that is offset from the first magnetic sensor in the circumferential direction of the magnet. A second magnetic sensor that is provided integrally with the first magnetic sensor and that detects a change in the magnetic field of the magnet to generate a second output signal; and a second magnetic sensor that is output from the first magnetic sensor. Rotation direction discriminating means for discriminating the forward and reverse rotation directions of the rotor based on the phase difference between the output signal of No. 1 and the second output signal outputted from the second magnetic sensor. .

Action The present invention is based on the phase difference between the output signals output from both magnetic sensors by arranging two magnetic sensors of a current consumption type lower than that of the two-phase magnetic sensor so as to be displaced in the rotation direction of the rotor. This is to accurately determine whether the rotor is rotating normally or reversely (normal or reverse flow of the fluid to be measured) so that it can be operated by a battery regardless of an external power source.

Further, since the pair of magnetic sensors are integrated in a state of being displaced from each other in the circumferential direction, it is possible to reduce the diameter of the annular magnet and the size of the detection unit, and the mounting space for the detection unit is small. Since the assembling work can be performed more easily than attaching two sensors on the body, the productivity can be improved.

Embodiment FIG. 1 to FIG. 4 show a positive displacement flow meter as an embodiment of the flow meter according to the present invention.

In both figures, the positive displacement flow meter 1 is provided with a pair of rotors 4 and 5 rotatably in a measuring chamber 3 of a casing 2. The casing 2 has an inflow path 6 located upstream of the weighing chamber 3 and an outflow path 7 located downstream of the weighing chamber 3. The inflow path 6 and the outflow path 7 open to the measuring chamber 3 from the upper side and the downstream side, respectively, and communicate with each other through the measuring chamber 3. Rotor 4,5
Are meshed with each other by elliptical gears and are supported by rotating shafts 8 and 9. When the fluid to be measured is supplied from the inflow passage 6 into the measuring chamber 3, the pair of rotors 4 and 5 rotate the rotating shafts 8 and 9 due to the pressure of the fluid.
Rotate around. The fluid from the inflow passage 6 is the rotor 4,
With the rotation of 5, the fluid is introduced into the space 11 between the rotors 4, 5 and the inner wall 10 of the measuring chamber 3, and the fluid corresponding to the volume of the space 11 is discharged to the outflow passage 7.

A lid member 12 for closing the measuring chamber 3 is provided on the upper surface 2a of the casing 2.
Are fixed by tightening bolts 13. A flow rate display unit 14 shown in FIG. 4 is attached to the lid member 12.

This flow rate display unit 14 has a display case 14a on the upper part, and in the display case 14a, a flow rate indicator 15 for displaying a flow rate, a substrate 17 provided with a control circuit 16 and the like, a flow rate indicator 15 and a control circuit A battery 18 and the like for supplying electric current to each part such as 16 and the like is provided. Further, a connector 19 for outputting a flow rate pulse to the outside is provided at an intermediate portion of the flow rate display unit 14, and a sensor unit 20 is provided at a lower portion. As shown in FIG. 5, the sensor unit 20 is integrally attached so that the magnetic sensors 21 and 22 composed of a pair of magnetoresistive elements and the like are overlapped with each other while being displaced in the X direction. (Details will be described later.) As shown in FIGS. 6 and 7, a magnet 23 for detecting rotation is embedded in the center of the upper portion of the rotor 4. The rotors 4 and 5 are both molded of synthetic resin, and the magnet 23 is embedded in the central step portion 4b of the end surface 4a of the rotor 4 by insert molding.

The magnet 23 is formed of a plastic magnet in an annular shape, and a large number of S poles and N poles are alternately magnetized in the circumferential direction. Therefore, the number of pulses per rotation of the rotor 4 is increased, and the flow rate measurement accuracy is improved. In this embodiment, the magnet 23 is magnetized into eight equal parts.

The sensor unit 20 is a magnet embedded in the rotor 4.
It is inserted into the mounting recess 12a of the lid member 12 which closes the measuring chamber 3 so as to be close to the measuring chamber 23.

Here, the sensor unit 20 that constitutes the main part of the present invention will be described.

As described above, the sensor unit 20 is formed by combining the magnetic sensors 21 and 22 shown in FIG. The magnetic sensors 21 and 22 are, as shown in FIG. 6, FIG. 7 and FIG.
22a is provided in the vicinity of the outer periphery 23a of the magnet 23, and to be precise, a joint surface C between the flat plate-shaped magnetic sensors 21 and 22 is provided.
Is provided so as to substantially coincide with a tangent line D extending from the outer circumference 23a of the magnet 23. That is, the sensor unit 20 is mounted so that the radius r of the outer circumference 23a of the annular magnet 23 and the distance l from the central axis O of the rotor 4 to the joint surface C between the magnetic sensors 21 and 22 are approximately r≈l. To be

It has been confirmed by experiments that the magnetic flux density in the vicinity of the outer periphery 23a of the magnet 23 formed in a ring shape is the largest. Therefore, in the present embodiment, in order to further enhance the detection sensitivity of the magnetic sensors 21 and 22, one-dot chain line in FIG. Magnetic sensor 2
1, 22 are arranged so that the detection ends 21a, 22a face each other near the outer circumference 23a of the magnet 23.

Therefore, the magnetic sensor 21 as the first magnetic sensor is provided so that the detection end portion 21a extends in the circumferential direction of the magnet 23, and the magnetic sensor 22 as the second magnetic sensor is arranged such that the magnetic sensor 21 is closer to the magnet 23 than the magnetic sensor 21. Magnetic sensor 21 at a position shifted in the circumferential direction of
It is provided integrally with.

Therefore, since the two magnetic sensors 21 and 22 can be integrated and handled as one component, it is possible to reduce the diameter of the annular magnet 23 and the sensor unit 20 and reduce the size of the sensor unit 20. Since the mounting space is small and the assembly work is easier than mounting two separate sensors, productivity can be improved.

The magnetic sensor 21 is a low current consumption type composed of a one-phase magnetoresistive element, and has a characteristic that the peak value of the output voltage becomes large with respect to the magnetic fields from the X direction and the Y direction in FIG. have. Therefore, the magnetic sensor 21 is housed in the flat plate-shaped main body 21b in such a direction that the patterns R _A and R _B shown in FIG. 9 can easily detect the magnetic field entering from the detection end 21a. Further, the bottom of the main body 21b terminal 21c for outputting a magnetic field detection signal (T ₁ ~T ₃₎ protrudes. The other magnetic sensor 22 has the same structure as the magnetic sensor 21 described above, and thus the description thereof is omitted. Further, since both the magnetic sensors 21 and 22 are of low current consumption type, the battery 18
Can operate sufficiently.

Since the magnetic sensors 21 and 22 are one-phase magnetoresistive elements that are manufactured and marketed according to predetermined standards, they can be easily purchased.

The magnetic sensor 21, (22) the pattern R _A as a detection unit consisting of a ferromagnetic material on a semiconductor silicon _{substrate, R B (R C, R} D) will be deposited, integral magnets 23 and the rotor 4 The resistance value of the patterns R _{A to} R _D changes as the magnetic flux density changes with rotation. Therefore, the magnetic sensor
21 and 22 are magnets 23 when a constant voltage is applied to the pattern.
The change in resistance value due to the rotation of is output as an alternating change in voltage according to the number of passing poles of the magnet 23, and as a result, the rotor 4
The rotation speed of can be detected.

The pair of magnetic sensors 21 and 22 are integrally bonded as shown in FIGS. 10 (A) to (C). That is, the magnetic sensors 21, 2
2 is assembled so that the main bodies 21b and 22b overlap each other while being shifted in the X direction, and the terminals 21c and 22c are soldered to the upper and lower surfaces of the board 24, respectively. The terminals 21c and 22c are connected as shown in FIG. That is, two patterns R _A , R _B and R _C , R _D are formed on the magnetic sensors 21 and 22, respectively, and the terminals T ₁ and T ₁ and T ₃ of the magnetic sensors 21 and 22 are formed by the soldering process. And T ₃ are connected respectively, and drive voltage V is applied to terminals T ₁ of magnetic sensors 21 and 22.
_C is applied and the terminals T ₃ of the magnetic sensors 21 and 22 are grounded. Then, the magnetic field of the magnet 23 causes the magnetic sensors 21, 22 to
After passing through, output signals are output from the terminals T ₂ and T ₂ with a phase difference. In addition, a lead wire 25 (connector at the tip is used for outputting detection signals from the magnetic sensors 21 and 22 to the board 24.
25a) is soldered.

Further, the magnetic sensors 21 and 22 are inserted into the mounting holes 26a of the cap 26 as shown in FIG. 11 while being soldered to the substrate 24 as described above. Then, as shown in FIG. 12, after the substrate 24 is adhesively fixed to the cap 26 so that the detection ends 21a, 22a of the magnetic sensors 21, 22 are flush with the end 26b of the cap 26, the cap 26 The mounting holes 26a are filled with a silicone resin 27 or the like to protect the magnetic sensors 21 and 22. In this way, the pair of magnetic sensors 21 and 22 are assembled to the cap 26 in a state of being displaced in the X direction to form a two-phase magnetic sensor.
And the cap 26 is a flow rate display unit as shown in FIG.
Mounted on the bottom of 14.

In the sensor unit 20 having the above configuration, the cap 26 has a lid member.
The pair of magnetic sensors 21 and 22 is inserted into the recess 12a of the rotor 12, and the pair of magnetic sensors 21 and 22 is attached to the rotor 4.
It is close to the position indicated by the one-dot chain line in the figure. That is, the magnetic sensor
21 and 22 have detection ends 21a and 22a near the outer circumference 23a of the magnet 23, respectively.
It is attached so as to face parts A and B (shown in FIG. 9). Further, the sensor unit 20 is connected to the board 17 in the storage case 14a via the lead wire 25, and the board 17 is connected to the 13th board.
As shown in the figure, in addition to the flow rate display section 15 and the control circuit 16, the A phase amplifier 28, the B phase amplifier 29, the A phase output circuit 30, the B phase output circuit 31,
A count correction switch 32 and the like are provided. Also, the control circuit
16 is a forward / reverse discrimination circuit 33 and a count correction circuit 3 as shown in FIG.
4. It has an output frequency dividing circuit 35.

Here, the operation when measuring the flow rate will be described. The fluid flows into the measuring chamber 3 through the inflow passage 6 as shown by the arrow in FIG. 1, rotates the pair of rotors 4 and 5, and flows out to the outflow passage 7. Therefore, the rotors 4 and 5 rotate at the number of rotations corresponding to the flow rate, and the rotation of the rotor 4 is detected by the magnetic sensors 21 and 22 incorporated in the lid member 12.

That is, the magnetic sensors 21 and 22 detect changes in the magnetic field of the magnet 23 that rotates with the rotor 4, and output a detection signal according to the number of magnetized magnetic poles of the magnet 23 per one rotation of the rotor 4. . The individual output voltages of the magnetic sensors 21 and 22 usually have a sine waveform as shown in FIG. However, in the present embodiment, as described above, the pair of magnetic sensors 21, 22 are provided in a state of being displaced in the X direction, so that the magnetic field of the magnet 23 passes through the A-phase magnetic sensor 21, and then the B-phase. Will pass through the magnetic sensor 22. The output signal of the magnetic sensor 21 is waveform-shaped and amplified by the A-phase amplifier 28 and input to the control circuit 16, and the output signal of the magnetic sensor 22 is waveform-shaped and amplified by the B-phase amplifier 29 and input to the control circuit 16. .

Since the magnetic sensors 21 and 22 are provided so that the joint surface C coincides with the vicinity of the outer circumference 23a of the magnet 23 having the largest magnetic flux density as described above, the detection sensitivity is enhanced and a larger output signal is output. be able to. Therefore, the magnetic sensor
The rotation of the rotor 4 is reliably detected by 21,22.

The control circuit 16 calculates the flow rate based on the output signal from the magnetic sensor 21 or 22. Further, the forward / reverse determination circuit 33 provided in the control circuit 16 determines the rotation direction of the rotor 4 based on the advance or delay of the phases of the A-phase output signal and the B-phase output signal.

Then, the coefficient correction circuit 34 makes a correction based on the coefficient set by the locking correction switch 32. Further, the signal output from the coefficient correction circuit 34 is frequency-divided by the output frequency dividing circuit 35 and supplied to the output circuits 30 and 31.

As the magnet 23 rotates, the signals obtained by the magnetic sensors 21 and 22 are input to the amplifiers 28 and 29 as signals having a phase difference, and the signals input from the amplifiers 28 and 29 to the control circuit 16 are the 17th signal. As shown in the figure. Amplifier 2 in the forward / reverse discrimination circuit 33
When signals with a phase difference are input from 8, 29, the processing of the control circuit 16 is interrupted at the falling and rising edges of the A-phase pulse,
At that time, the output states of the A-phase and B-phase pulses are read to determine whether the rotor 4 is forward or reverse. The judgment condition in that case is the 18th
Shown in the figure. Therefore, in this embodiment, if the output of the B-phase is "H" when the fall of the output of the A-phase is "L", it is determined that the rotor 4 is rotating normally. When the output of the A phase is “H” and the output of the B phase is “H”, the rotation 4
Is reversed, that is, it is determined that the fluid is flowing backward.

Then, the control circuit 16 supplies a signal from the output frequency dividing circuit 35 to the flow rate indicator 15 to display the flow rate when the rotor 4 is rotating normally.

Further, when the rotor 4 rotates in the reverse direction, the control circuit 16 stores the pulse number in the reverse rotation and subtracts that amount from the integrated flow rate.

It should be noted that in the above embodiment, the positive displacement type flow meter is described as an example, but it is needless to say that the present invention is not limited to this and can be applied to other types of flow meters.

Further, in the above-described embodiment, the joint surface C of the pair of magnetic sensors 21 and 22 is arranged to face the outer circumference of the magnet 23. However, the position of the pair of magnetic sensors 21 and 22 is not limited to this, and the joint portion is not limited thereto. The surface C may be opposed to the inner circumference of the magnet 23 or between the inner circumference and the outer circumference.

EFFECTS OF THE INVENTION As described above, the flowmeter according to the present invention forms a two-phase magnetic sensor by combining magnetic sensors of low current consumption type, and the rotor is based on the phase difference of the output signals from the pair of magnetic sensors. Since the rotation direction can be determined, the flow rate pulse when the fluid flows backward can be accurately corrected, and the accuracy of the flow rate measurement value can be improved. Moreover, since it consumes less current, it can be operated by a battery, and even if it is installed outdoors or in a large facility such as a factory where external power cannot be supplied, flow rate correction due to backflow of fluid can be accurately performed. Further, since the pair of magnetic sensors are integrated in a state of being displaced from each other in the circumferential direction, it is possible to reduce the diameter of the annular magnet and the size of the detection unit, and the mounting space for the detection unit is small. Assembling work is easier than attaching two sensors on the body, which has the advantage of improving productivity.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of an embodiment of a flow meter according to the present invention, FIG. 2 is a side view with a part cut away from FIG. 1, and FIG. 3 is a cross-sectional view of a casing with a flow rate display unit removed. 4 and 5 are side sectional views of the flow rate display unit, FIG. 5 is a bottom view of the sensor unit, and FIGS. 6 and 7 are vertical sectional views and plan views of the rotor.
8 is an external view of the magnetic sensor, FIG. 9 is a configuration diagram showing the pattern of the magnetic sensor and the positional relationship between the magnetic sensor and the magnet,
FIG. 10 is a view showing a state in which a pair of magnetic sensors are integrally assembled, and FIGS. 11 and 12 are perspective views for explaining the assembled state of the sensor unit, a partially cutaway sectional view, FIG. 13 is a circuit diagram of a circuit provided on the substrate of the flow rate display unit,
FIG. 14 is a block diagram of a control circuit, FIG. 15 is an output waveform diagram of a one-phase magnetic sensor, FIG. 16 is an output waveform diagram of signals output from a pair of magnetic sensors, and FIG. 17 is an A-phase pulse. FIG. 18 is a waveform diagram for explaining the discriminating operation of the normal rotation and the reverse rotation of the rotor based on the phase difference of the B-phase pulse, and FIG. 18 is a diagram showing the forward / reverse discrimination condition of the forward / reverse discrimination circuit. 1 ... Positive displacement type flow meter, 2 ... Casing, 3 ... Measuring chamber, 4,5 ... Rotor, 14 ... Flow rate display unit, 15 ...
Flow rate display, 16 ... Control circuit, 18 ... Battery, 20 ... Sensor unit, 21, 22 ... Magnetic sensor, 23 ... Magnet, 24 ...
... Board, 25 ... Lead wire, 26 ... Cap, 28 ... A phase amplifier, 29 ... B phase amplifier, 30 ... A phase output circuit, 31 ...
… B-phase output circuit, 32 …… coefficient correction switch, 33 …… forward / reverse discrimination circuit, 34 …… coefficient correction circuit, 35 …… output divider circuit.

Claims (1)

[Claims] 1. A rotor that rotates at a rotational speed according to the flow rate of a fluid to be measured, and a rotor that is provided on the rotor so as to be coaxial with the center of rotation of the rotor and has a north pole and a south pole in the circumferential direction. Annular magnets alternately formed, and the detection end portion is provided so as to extend in the circumferential direction of the magnet,
A first magnetic sensor that detects a change in the magnetic field of the annular magnet due to the rotation of the rotor to generate a first output signal; and a position that is offset from the first magnetic sensor in the circumferential direction of the magnet. A second magnetic sensor that is provided integrally with the first magnetic sensor and that detects a change in the magnetic field of the magnet to generate a second output signal; and a second magnetic sensor that is output from the first magnetic sensor. Rotation direction discriminating means for discriminating the forward and reverse rotation directions of the rotor based on the phase difference between the output signal of No. 1 and the second output signal outputted from the second magnetic sensor. Flowmeter.