JPH04353723A - Volume type flowmeter - Google Patents

Abstract

PURPOSE:To obtain a volume type flowmeter which is formed in such a way that corrosive fluid can be stably measured. CONSTITUTION:A volume type flowmeter 1 has elliptical-gear-shaped rotors 4 and 5 which are formed of magnetic stainless steel in a measuring chamber 3 of a casing 2 formed of nonmagnetic stainless steel. A cap 14 sealing the measuring chamber 3 is formed of nonmagnetic stainless steel. An N-pole magnet 15a and an S-pole magnet 15b are provided in the inside. A magnetic sensor 16 is attached to the upper part between the magnets 15a and 15b. The magnetic sensor 16 detects the strength of the magnetic field between the magnets 15a and 15b. The sensor 16 detects the change in magnetic field when a major axis part 4a of the rotor 4 passes the lower part of the magnet 15a at the time of measurement of the flow rate and outputs the pulse corresponding to the flow rate (number of rotation).

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a volumetric flowmeter, and more particularly to a volumetric flowmeter suitable for measuring the flow rate of corrosive fluids.

0002

[Prior Art] For example, in a conventional positive displacement flowmeter, a pair of oval gear-shaped rotors are rotatably provided in a measuring chamber of a casing. Flow rate was measured by detecting rotation. The rotation detecting means for detecting the rotation of the rotor in this manner includes a magnet embedded in the end face of one of the rotors, and a magnetic sensor provided on the casing side facing this end face.

The magnet detected by the magnetic sensor is embedded in the end face of the major diameter portion of the elliptical gear, and the magnetic sensor is provided on the casing side so as to face the position through which the major diameter portion passes. Therefore, the magnet provided on the rotor is always in contact with the liquid when measuring the flow rate.

A magnetic sensor detects changes in the magnetic field from a passing magnet as the rotor rotates, and outputs the signal as a flow rate signal.

When the fluid to be measured is a corrosive fluid, the casing is made of non-magnetic stainless steel (for example, SUS316), and the oval gear-shaped rotor has not only corrosion resistance but also tooth surface wear resistance. In consideration, ferromagnetic stainless steel (for example, SUS630) having high hardness is used.

[0006]

[Problem to be Solved by the Invention] However, in the past, the magnets provided on the rotor were in contact with the liquid, so when corrosive fluid was measured, the magnets were likely to corrode and the magnetic field was weakened.
There is a problem in that the rotation of the rotor cannot be detected by the magnetic sensor.

Furthermore, since the rotor is made of a magnetic material, the magnetic flux of the magnet provided in the rotor is easily absorbed by the rotor, which reduces the sensitivity of the magnetic sensor to detect rotation of the rotor, resulting in a stable flow rate. There is also the issue of not being able to detect it.

[0008] Accordingly, an object of the present invention is to provide a positive displacement flowmeter that solves the above problems.

[0009]

[Means for Solving the Problems] The present invention provides a non-circular rotor that is formed of a magnetic material and rotates at a rotational speed that corresponds to the flow rate flowing through a metering chamber, and a position through which a major diameter portion of the rotor passes. between the N-pole and S-pole magnets that are attached from the outside of the wall surrounding the measuring chamber so as to be close to the measuring chamber, and the N-pole magnet and the S-pole magnet that pass through the long diameter part as the rotor rotates. and a magnetic sensor that detects changes in the magnetic field.

0010

[Operation] Since the magnet is provided outside the measuring chamber, it does not come into contact with the fluid, and the flow rate can be measured satisfactorily even in corrosive fluids. In addition, since the change in the magnetic field is detected when the long diameter part of the rotor, which is made of a magnetic material, passes close to the magnet installed outside the measuring chamber, the detection sensitivity of the magnetic sensor is increased and rotor rotation detection is stabilized. It can be done accurately.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 to 3 show an embodiment of a positive displacement flowmeter according to the present invention.

In each figure, a positive displacement flowmeter 1 includes a pair of rotors 4 and 5 provided within a metering chamber 3 of a casing 2. The casing 2 is made of non-magnetic stainless steel so that corrosive fluid can be measured, and has an inlet passage 6 located upstream of the measuring chamber 3 and an outlet passage downstream of the measuring chamber 3. 7. The inflow passage 6 and the outflow passage 7 open into the measuring chamber 3 from the upper and downstream sides, respectively.
communicated through.

The rotors 4 and 5 are each made of ferromagnetic stainless steel and shaped like elliptical gears so that corrosive fluid can be measured. The rotors 4 and 5 have teeth formed on their outer peripheries that mesh with each other, and the rotors 4 and 5 are connected to the rotating shaft 8 through bearings 8a and 9a.
, 9. When the fluid to be measured is supplied into the measuring chamber 3 from the inflow path 6, the pressure of the fluid causes the pair of rotors 4 to
, 5 rotate around rotation axes 8 and 9. The fluid from the inflow passage 6 is introduced into the space 11 between the rotors 4 and 5 and the inner wall 10 of the metering chamber 3 as the rotors 4 and 5 rotate, and the fluid corresponding to the volume of the space 11 flows into the outflow passage 7. be discharged.

A lid 14 for closing the upper opening of the measuring chamber 3 is attached to the upper surface of the casing 2.
Pole and S pole magnets 15a and 15b, and magnets 15a and 15
A magnetic sensor 16 is embedded therein to detect changes in the magnetic field between the two. Further, the lid 14 is made of non-magnetic stainless steel having corrosion resistance. N-pole, S-pole magnet 15a
, 15b are inserted into magnet insertion holes 14b and 14c provided at the bottom of the sensor insertion hole 14a provided on the top surface of the lid 14, respectively. Therefore, the magnets 15a and 15b do not come into contact with fluid, and even when measuring a corrosive fluid, they do not corrode at all and therefore do not deteriorate. In addition, the magnet insertion hole 14
b, 14c are closed by a partition plate 17 made of a non-magnetic material, and held by a holder 18 so that the magnetic sensor 16 is placed on this partition plate 17.

One of the magnet insertion holes 14a is provided on the inner side of the inner wall 10, with the inner wall 10 of the measuring chamber 3 as a boundary, and above the long diameter portion 4a of the rotor 4 of the measuring chamber 3. The other magnet insertion hole 14b is located outside the magnet insertion hole 14a, and is provided so as to face the upper surface 2a of the casing 2 surrounding the measuring chamber 3 outside the inner wall 10. Therefore, the N-pole magnet 15a is provided close to a position through which only the long diameter portion 4a of the rotor 4 passes, and the S-pole magnet 15b is provided close to the upper surface of the casing 2 surrounding the periphery of the upper opening of the measuring chamber 3. It is located in a position where

Therefore, during one rotation of the rotor 4, the long diameter portion 4a of the elliptical gear passes under the N-pole magnet 15a every 180 degrees and passes through the magnetic field between the magnets 15a and 15b.

The magnetic sensor 16 includes a pair of magnets 15a, 15.
magnet 15a.
and 15b at a position where it is easy to detect changes in the magnetic field.

Reference numeral 19 denotes an arithmetic circuit that integrates the pulses output from the magnetic sensor 16 to calculate the flow rate. In addition, the flow rate measurement value calculated by the calculation circuit 19 is output to the integration display section 20 and the path output circuit 21, and is displayed on the display section 20.
is output to.

The measurement operation of the positive displacement flowmeter 1 having the above configuration will now be explained.

[0020] When measuring the flow rate, the fluid flows from the inflow path 6 to the metering chamber 3.
flow inside. A pair of rotors 4 provided in the measuring chamber 3
, 5 are meshed with each other, so that they rotate counterclockwise and clockwise, respectively, at rotational speeds corresponding to the flow rate flowing into the metering chamber 3. The fluid that has flowed into the metering chamber 3 is then transferred to the rotors 4 and 5.
It flows out from the outflow path 7 with the rotation of.

As described above, a magnetic flux 22 is generated between the N-pole magnet 15a and the S-pole magnet 15b provided on the lid 14, as shown in FIG. The short diameter portion 4b of the rotor 4 is the magnet 1
5b, the distance between the short diameter portion 4b and the magnet 15b is long, and the short diameter portion 4b does not block the magnetic flux 22. Therefore, since the magnetic flux 22 is stable, the strength of the magnetic field does not change and the output of the magnetic sensor 16 becomes H level.

However, as shown in FIG. 5, when the long diameter portion 4a of the rotor 4 passes below the N-pole magnet 15a, it is closer to the magnet 15a than the short diameter portion 4b. Since the rotor 4 is a magnetic material, when the long diameter portion 4 passes below the magnet 15a, it absorbs the magnetic flux 22 from the magnet 15a. At that time, the magnetic field between the magnets 15a and 15b weakens, and the magnetic sensor 16
output drops to L level. Therefore, the magnetic sensor 16
The output has a waveform as shown in FIG.

Since the long diameter portion 4a passes under the magnet 15a twice during one rotation of the rotor 4, the magnetic sensor 16 outputs two pulses per rotation of the rotor. In this way, since the fluid does not come into contact with the magnets 15a, 15b when measuring the flow rate, the magnets 15a, 15b are prevented from corrosion even when measuring corrosive fluid, and can always maintain the desired magnetic strength. Therefore, the durability of the flowmeter is improved, and accurate flow measurement can be performed regardless of the corrosive fluid.

Furthermore, the magnets 15a and 15b are attached to the fixed side lid 14.
Since it is embedded in the rotors 4 and 5, it is attached to the magnetic sensor 16 in a more stable state than when it is installed in the rotors 4 and 5, so that the output of the magnetic sensor 16 is more stable. Moreover,
Only when the long diameter portion 4a of the rotor 4 passes, the magnet 15a,
Since the magnetic field strength between 15b is reduced, the magnetic sensor 16 can detect changes in the magnetic field with high sensitivity.

FIG. 7 shows a modification of the present invention. Note that FIG. 7 is a cross-sectional view of the casing 2, and the lid 14 is omitted so that the position of the magnet can be easily seen.

In the figure, two sets of magnets 15a, 15b (15a', 15
b'), and magnets 15a, 15b (15a', 15
Magnetic sensors 16, 16' are arranged above between b').

That is, one set of magnets 15a, 15b is for detecting the rotation of the rotor 4, and the other set of magnets 15a', 15
b' is for detecting the rotation of the rotor 5. a pair of rotors 4,
5 rotate at a phase of 90 degrees so that the long diameter part and the short diameter part mesh with each other, so one set of magnets 15a, 15b is provided on the inlet 6 side, and the other set of magnets 15a', 15b ' is provided on the outflow port 7 side. And the N-pole magnet 15a,
15a' is embedded in the lid 14 so as to be located above the measuring chamber 3 with the inner wall 10 of the measuring chamber 3 as a border, and the S-pole magnet 15
b, 15b' are embedded in the lid 14 so as to face the outside of the inner wall 10, that is, the upper surface of the casing 2 surrounding the measuring chamber 3.

Therefore, the long diameter portion 4a of the rotor 4 is connected to the magnet 15.
When the rotors 4 and 5 further rotate 90 degrees after passing under the magnet 15a', the long diameter portion 5a of the rotor 5 passes under the magnet 15a'. In this way, a total of four pulses are output from the pair of magnetic sensors 16, 16' during one rotation of the rotors 4, 5.

[0029] Therefore, the number of pulses per rotation of the rotors 4 and 5 increases, and the measurement accuracy is further improved.

Although the above embodiment has a configuration having an elliptical gear-shaped rotor, the present invention is not limited to this and can of course be applied to a roots-type positive displacement flowmeter having a cocoon-shaped rotor.

Further, the magnets 15a and 15b may be provided inside the wall of the casing 2 surrounding the measuring chamber 3 other than the lid 14.

[0032]

Effects of the Invention As described above, the positive displacement flowmeter of the present invention can prevent the magnet from coming into contact with the fluid by providing the magnet for rotation detection outside the measuring chamber. It is possible to prevent the magnet from corroding even when measuring the amount of fluid, and the flow rate of corrosive fluids can be measured in the same way as normal fluids. Moreover, since the magnetic sensor can detect changes in the magnetic field of the magnet fixedly installed outside the metering chamber as the rotor, which is made of a magnetic material, rotates, the detection sensitivity of the magnetic sensor is increased and the rotor It has features such as being able to stably detect rotation.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of one embodiment of a positive displacement flowmeter according to the present invention, cut in a direction perpendicular to a flow path direction.

FIG. 2 is a longitudinal cross-sectional view showing the positive displacement flowmeter shown in FIG. 1, cut in the flow path direction.

FIG. 3 is a cross-sectional view of the positive displacement flowmeter shown in FIG. 1.

FIG. 4 is a diagram for explaining a rotation detection (flow rate detection) operation when the short diameter portion of the rotor passes a magnet.

FIG. 5 is a diagram for explaining a rotation detection (flow rate detection) operation when the long diameter portion of the rotor passes a magnet.

FIG. 6 is an output waveform diagram of a magnetic sensor.

FIG. 7 is a cross-sectional view showing a modification of the present invention.

[Explanation of symbols]

1 Positive displacement flowmeter 2 Casing 3. Weighing room 4,5 Rotor 14 Lid 15a, 15b magnet 16 Magnetic sensor 19 Arithmetic circuit

Claims (1)

[Claims] 1. A non-circular rotor formed of a magnetic material and rotating at a rotational speed corresponding to the flow rate flowing through the metering chamber;
N-pole and S-pole magnets are attached from the outside of the wall surrounding the measuring chamber so as to be close to the position where the long diameter portion of the rotor passes, and an N pole magnet is attached from the outside of the wall surrounding the measuring chamber so as to be close to the position where the long diameter portion of the rotor passes, and the N pole is generated by passing the long diameter portion as the rotor rotates. A positive displacement flowmeter comprising: a magnetic sensor that detects changes in the magnetic field between the magnet and the S-pole magnet.