JPH071186B2 - Flow meter transmitter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a flow meter for optically detecting the rotation of a rotor composed of a pair of non-circular gears that mesh and rotate in proportion to the flow rate in a measuring chamber. Regarding the improvement of the transmitter.

(B) Conventional technology A magnetic detection method is generally used to detect the rotation of a positive displacement flow meter, but in this method, a high-density magnet is embedded in the rotor, As the weight of the child increases, a load torque due to the magnetic force is added, which becomes an impeding factor when improving the small flow sensitivity. On the other hand, in the case of optical detection, a through-hole is bored in the rotor, and a transmission method is used to detect the interruption of the light passing through the through-hole. There is a reflection method for detecting reflected light from the above, and these are excellent in the above-mentioned obstructive factors of the magnetic detection method. Also in the optical detection method, the transmission method is superior to the reflection method in terms of the S / N ratio, but it has a problem that it cannot be detected when powder particles adhere to the through holes.

(C), Problems to be Solved by the Invention On the other hand, in the conventional reflection method, since the method of burying the reflector in the rotor end face is adopted, it takes a lot of work, especially in the case of improving the resolution. However, since the number of buried reflectors is increased, the number of perforations is also increased, and the number of steps is increased, so that the cost cannot be reduced. When the rotor is non-circular, the rotational angular velocity of the rotor is not constant even if the flow rate is constant. Therefore, when the reflectors are arranged at equal intervals around the rotation axis, the reflected light is shaped and output. Since the pulse interval of the pulse signal changes in proportion to the rotational angular velocity, it is meaningless to change the flow rate per pulse and arrange the reflectors at equal intervals to improve the resolution. In order to correct this, it may be possible to adjust the embedding interval of the reflectors and arrange them, but it has been extremely difficult to construct such a structure. Further, when the flow rate is stopped, an incorrect transmission value is generated even if the rotor is displaced due to backlash of the rotor mesh, or the rotor is rotated in the reverse direction due to pulsating flow, so that an accurate measured value cannot be obtained. There was a problem. Also, in order to improve the resolution, the number of reflectors embedded in the rotor end face must be increased, but the number of embedded reflectors is limited due to the size limitation of the reflectors. In order to increase the resolution beyond the range, the size of the reflectors must be reduced and the number of reflectors must be increased. However, if the size of the reflector is reduced, the amount of reflected light is reduced, so that stable detection of reflected light cannot be performed. In order to increase the resolution and increase the amount of reflected light, one condition is to project with a minute light beam and increase the intensity of the projected light, but the optical system to satisfy this is expensive and vibration Due to the fact that it is not possible to attach it to a flowmeter with a large number of reflectors, the conventional reflector multiplication method has a limit in the number of reflectors and cannot detect a flow pulse with high sensitivity and high resolution. .

(D) Means for Solving the Problems The present invention is to solve the problems in the conventional example described above, and includes a pair of meshing rotations in proportion to the flow rate in the measuring chamber into which the measurement fluid flows. In a transmitter of a flowmeter having a non-circular rotor, a thin plate annular light reflector embedded in at least one end face of the non-circular rotor so as to have a surface substantially equal to the end face, A marker installed on the major axis or minor axis of the circular rotor and indicating the position of the major axis or minor axis, and the non-circular rotor when the non-circular rotor rotates at a constant flow rate. A thin plate annular encoder provided with a radial slit having a slit width or interval proportional to the rotational angular velocity of the circular rotor, a first photodetector for projecting and receiving light in the slit, and detecting the position of the slit, From the position of the first photodetector It comprises a second photodetector installed at a position on the slit which is separated by a predetermined position, and a third photodetector which projects and receives light on the marker of the thin plate annular encoder and detects the position of the marker. ,
(1) The photodetector is configured such that a plurality of light emitting / receiving fibers forming a pair with the slit as a reflecting surface are integrally disposed in a pair of cylindrical bodies in the length direction of the slit, or ( 2) The photodetector has a transparent body for transmitting light from a light emitting source, a transparent body for transmitting reflected light, and a semi-cylindrical lens arranged in front of these transparent bodies. The lens is arranged so that the focal point of the light transmitted from the lens is connected to a line parallel to the slit of the thin plate annular encoder, and the reflected light is condensed through the lens, This solves the above problem.

(E), Embodiment FIG. 1 is a plan view (plan view taken along the line II of FIG. 2) for explaining an embodiment of the flowmeter transmitter according to the present invention, and FIG. 2 is a sectional view taken along line II-II of FIG. 1, in which 1 is a flowmeter casing, 2 is a metering chamber, 3 is an inlet, 4 is an outlet, and 5 is O.
Ring groove, 6 and 7 are non-circular rotors, 8 and 9 are rotating shafts, 10
Is an end face plate, and as is well known, the non-circular rotor is rotated in the direction of the arrow by the fluid to be measured, and the flow rate of the fluid to be measured is measured from the number of rotations.

The present invention is to measure the number of rotations of the non-circular rotor in the flow meter as described above using a reflection type optical detector, and the thin plate annular encoder 11 and the photodetector 12 in the figure are therefor, The encoder 11 has a large number of slits 11a and is embedded in at least one end face of the non-circular rotor 6 or 7 so as to have a surface substantially equal to the end face, and faces the slits of the encoder. Is provided with a photodetector 12, the light emitted from the photodetector 12 is reflected by the slit portion of the encoder 11 or a portion between the slits, the reflected light is received by the photodetector 12 and Encoder 11
Measure the number of revolutions of the non-circular rotor.

FIG. 3 is a diagram showing a change in angular velocity when the flow rate of the non-circular rotor is constant, and the angular velocity ω changes according to the meshing position as shown because the rotor is non-circular. However, the average angular velocity is 1.

FIG. 4 is a plan view showing an embodiment of the annular encoder 11, in which 11a is a slit, 11b is a mark, and the slit is a slit.
The pitch of 11a is wide as shown by W ₁ in the portion corresponding to the short diameter of the non-circular rotor, and narrow as shown by W ₂ in the portion corresponding to the long diameter. That is, the slit width or spacing is such that it is a positive function of the rotational angular velocity of the non-circular rotor at a constant flow rate. More specifically, as described above, the non-circular rotor has different rotational angular velocities depending on the meshing position, and the rotational angular velocity ω at the minor axis portion is different.
Is large and becomes small in the long diameter portion, so if the slit pitch is made uniform, the flow rate per pitch movement differs depending on the meshing position, and the number of slit movements can be detected optically as described above. When measuring the flow rate by
The weight per pitch, that is, per pulse differs depending on the meshing position, and the resolution is poor. In the present invention, in order to solve such a problem, the pitch of the slits is made to be a positive function of the rotational angular velocity of the non-circular rotor, and when this is done, the weight per pulse is the same. Become 1
The flow rates per pulse are all equal and the resolution is improved. Note that 11b is a mark indicating the position of the major axis or minor axis of the non-circular rotor (in the illustrated example, the major axis is indicated), and the semi-rotation or 1
Rotation is detected, and an alarm is generated when the number of pulses detected during this half rotation or one rotation exceeds a predetermined value, whereby a mistaken transmission caused by rattling of the rotor mesh is generated. Alternatively, the pulsating flow warns the transmission of an error caused by the rotor vibrating in the forward and reverse directions.

FIG. 5 is a sectional view for explaining one embodiment of the photodetector 12, where (a) is a plane sectional view ((b) or (c)).
(A line cross-sectional view), (B) is a line cross-sectional view of (A), and (C is a cross-sectional view of (A)), in which 12a is an outer cylinder, 12b is a transparent material, and 12c is A molding material, 12d _{1 to} 12d ₆ are optical fibers, and these optical fibers 12d _{1 to} 12d ₆ are arranged in a direction coinciding with the longitudinal direction of the slit and are arranged on the measuring chamber end face plate 10 so as to face the slit. 12d ₁ , 12d ₃ ,
12d ₅ is a light-transmitting (or light-receiving) fiber, 12d ₂ , 12d ₄ , 12d ₆ is a light-receiving (or light-transmitting) fiber, and as shown in the drawing, a plurality of (three in the case of the illustrated example) light-transmitting optical fibers are used. A plurality of (three in the illustrated example) light receiving optical fibers emit light, and the light reflected and returned between the slits of the encoder 11 is received, whereby the amount of reflected light is changed. We are aiming to improve the resolution. The light detected by the light receiving fiber is converted into an electric signal, but since the encoder 11 rotates integrally with the non-circular rotor, an electric pulse is generated according to the rotation. Is uniform in the present invention as described above.

FIG. 6 is a cross-sectional view for explaining another embodiment of photodetection in which the amount of reflected light is increased, and (a) is a plane cross-sectional view of the photodetector 12 ((b) or (c)). -A line sectional view, (B) is a line sectional view of (A), and (C) is a line sectional view of (A). In the figure, 12e is a light-transmitting (or light-receiving) transparent body. , 12f is a light-receiving (or light-transmitting) transparent body, 12j is a light-shielding film, 12h is a semi-cylindrical lens, and the photodetector is arranged so that the focus of the semi-cylindrical lens is substantially equal to the surface of the encoder, and Similarly to the photodetector shown in FIG. 5, it is used by being attached to the end face plate 10 of the measuring chamber so that the longitudinal axis of the transparent body 12f for receiving (or transmitting) light coincides with the longitudinal axis of the slit.

In the present invention, by attaching the above-mentioned photodetector, it is possible to detect a flow rate pulse having a constant flow rate weight when the non-circular rotor is rotating at a constant flow rate. However, one photodetector cannot determine whether the flow rate is flowing in the forward direction or the reverse direction. To detect the flow in the forward and reverse directions, two photodetectors described above are required. That is, the first photodetector for detecting the slit at the predetermined position of the thin plate annular encoder 12 and the predetermined phase from the slit position detected by the first photodetector with respect to the position of the first photodetector. A second photodetector is disposed at a position on the slit which is spaced apart, and as described below,
The positive / negative flow is detected by the positive / negative of the phase difference signal when the signals of the first photodetector and the second photodetector are detected as electrical pulses.

FIG. 7 is a diagram showing a waveform of an output signal from each photodetector when two photodetectors are arranged with a predetermined phase difference as described above, in which A ₁ is one Is an output signal from the (first) photodetector, B ₁ is an output signal from a second photodetector arranged with a predetermined phase difference φ with respect to the first photodetector. , I shows the output signal waveform at the time of forward rotation, and II shows the output signal waveform at the time of reverse rotation. That is, during positive rotation, the output signal B ₁ from the second photodetector rises when the output signal A ₁ from the first photodetector is positive. Therefore, by monitoring this relationship, a non-circular shape can be obtained. It can be detected that the rotor is rotating normally. On the other hand, during reverse rotation, when the output signal A _{1 of the first} photodetector is positive, the output signal from the second photodetector is
Since B ₁ falls, it can be detected from this relationship that the non-circular rotor is reversed, that is, the fluid to be measured is flowing backward.

FIG. 8 is an electric circuit diagram for performing the signal processing as described above, and FIG. 9 is a time chart for explaining the operation of the electric circuit of FIG. 8. In the figure, 21a, 21b, 22a, 22b are shown. Is an amplifier, and 23a and 23b are D flip-flop circuits, and the signal waveforms of respective parts in the circuit are as shown in FIG. However, in FIG. 9, I is a waveform at the time of forward rotation, and II is a waveform at the time of reverse rotation, and the output signals of the flip-flop circuits 23a and 23b are supplied to the addition / subtraction counter (not shown) via the amplifiers 22a and 22b, respectively. The net flow rate of the fluid to be measured can be measured by counting with the addition / subtraction counter.

Furthermore, in the present invention, a third photodetector is provided in addition to the first photodetector and the second photodetector. The third photodetector is a detector for detecting the marker 11b,
This is a photodetector having the same structure as the first and second photodetectors having the optical fiber for transmitting and receiving light or the transparent body shown in FIGS. The third detector is the marker 11b as described above.
To output a signal for detecting half rotation or one rotation of the non-circular rotor, and to generate an alarm when the number of pulses detected during this half rotation or one rotation is a predetermined number or more. Therefore, it is possible to warn of a mistaken transmission caused by the backlash of the non-circular rotor or a mistaken transmission caused by the non-circular rotor vibrating in the forward and reverse directions due to pulsation or the like. it can.

(F), Effect of the Invention As is apparent from the above description, according to the present invention, since the thin plate annular encoder is embedded in the surface of the non-circular rotor and the reflected light from the encoder is detected, Compared to the conventional method of embedding a reflector in a non-circular rotor,
It is very easy to manufacture and can be manufactured at low cost. In addition, the pitch interval of the slits of the encoder is set to be a positive function with respect to the rotation angular velocity of the non-circular rotor, and 1
Since the weight per pulse is made equal, the resolution of the measuring instrument can be improved. Furthermore, an alarm is easily issued for a mistaken transmission caused by the backlash of the rotor mesh when the flow rate is stopped, or for a mistaken transmission caused by the rotor oscillating in the forward and reverse directions by the pulsating flow. There are advantages such as being able to. Furthermore, by using a plurality of pairs of light emitting / receiving fibers or by using a semi-cylindrical lens, the amount of reflected light can be increased, and thereby the resolution can be improved.

[Brief description of drawings]

1 is a plan sectional view for explaining an embodiment of a flowmeter transmitter according to the present invention, FIG. 2 is a sectional view taken along line II-II of FIG. 1, and FIG. 3 is a non-circular rotor. FIG. 4 is a plan view showing an example of an encoder, FIGS. 5 and 6 are sectional views showing examples of photodetectors, and FIG. FIG. 8 is a diagram showing a waveform example of an output signal from the detector, FIG. 8 is a diagram showing an example of a signal processing circuit, and FIG. 9 is a time chart for explaining the operation of the circuit of FIG. 1 ... Casing, 2 ... Measuring chamber, 3 ... Inlet, 4 ...
… Outlet, 6,7 …… Non-circular rotor, 8,9 …… Rotary axis, 10…
… End plate, 11 …… Encoder, 12 …… Photodetector.

Front Page Continuation (72) Inventor Hiroshi Yamamoto 3-10-8 Kamiochiai, Shinjuku-ku, Tokyo Within Oval Equipment Industry Co., Ltd. (56) Reference JP 59-60215 (JP, A) JP 59- 143918 (JP, A) Actual development Sho 52-53755 (JP, U) Actual public Sho 29-3482 (JP, Y1)

Claims (2)

[Claims] 1. A transmitter of a flowmeter having a pair of non-circular rotors which mesh with each other in proportion to a flow rate in a measuring chamber into which a fluid to be measured flows, wherein at least one end face of the non-circular rotor has A thin plate annular light reflector buried so as to be substantially the same surface as the end face, which is installed on the major axis or minor axis of the non-circular rotor and indicates the position of the major axis or minor axis. A thin plate annular encoder provided with a radial slit having a slit width or interval proportional to the rotation angular velocity of the non-circular rotor when the non-circular rotor is rotated at a constant flow rate, as the marker reference position, A first photodetector for projecting and receiving light to and from the slit to detect the position of the slit, and a second photodetector installed at a position on the slit separated by a predetermined phase from the position of the first photodetector. And the thin plate annular encoder And a third photodetector for projecting and receiving light on the marker to detect the position of the marker, the photodetector having a light projecting and receiving fiber paired with the slit as a reflecting surface in the length direction of the slit. A flowmeter transmitter characterized by being integrally arranged in a plurality of pairs of cylindrical bodies. 2. A transmitter of a flowmeter having a pair of non-circular rotors that mesh with each other in proportion to a flow rate in a measuring chamber into which a fluid to be measured flows, wherein at least one end face of the non-circular rotor is provided with the non-circular rotor. A thin plate annular light reflector buried so as to be substantially the same surface as the end face, which is installed on the major axis or minor axis of the non-circular rotor and indicates the position of the major axis or minor axis. With the marker as a reference position, a thin plate annular encoder provided with radial slits having a slit width or interval proportional to the rotational angular velocity of the non-circular rotor when the non-circular rotor rotates at a constant flow rate, A first photodetector that projects and receives light on the slit to detect the position of the slit, and a second photodetector installed at a position on the slit that is separated from the position of the first photodetector by a predetermined phase. Container and the thin plate annular enco And a third photodetector for detecting the position of the marker, the photodetector transmitting a light from a light emitting source and a transparent body transmitting a reflected light. And a semi-cylindrical lens disposed on the front surface of these transparent bodies, and the lens is formed so that the focal point of the light transmitted from the light emitting source is aligned on a line parallel to the slit of the thin plate annular encoder. Is arranged so that the reflected light is condensed through the lens.