JPH0820296B2 - Flow transmitter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a flow rate transmitter of a positive displacement flowmeter that estimates a flow rate corresponding to one rotation of a rotor from a partial rotation speed to obtain an instantaneous flow rate.

The flow rate pulse transmitter of a volumetric flowmeter detects the rotation of a rotor that rotates in proportion to the flow rate and transmits it as a flow rate pulse, and the rotation of the rotor is reduced by a gear train. Further, there is a unit transmission system that transmits as a decimal flow rate unit via a correction gear that makes a minute adjustment according to the instrumental difference of the flow meter. The former flow rate pulse of the unitless transmission system is remotely transmitted and electrically corrected to a unit pulse for integration, etc., or is converted into an analog signal to be used as an analog signal for instantaneous flow rate display, control, etc. ,
As a field-installed flow meter, various flow rate calculations that have been remotely transmitted and processed are performed in a counter unit that is integrally mounted with the flow meter main body. On the other hand, the unit system pulse is mounted on a conventional flowmeter installed on site and is mainly transmitted remotely as a flow rate integration signal. Further, when an analog signal is required, it may be transmitted together as a unitless pulse. In recent years, due to the development of electronic technology, it has become easier to perform pulse calculation processing, and the number of flowmeters simply as a flow rate transmitting end for transmitting a unitless flow rate pulse has increased. In these unitless flow rate transmitters, the rotation of the flow meter rotor is generally detected by a detection unit provided in the main body, and electromagnetic and optical types are often used. The electromagnetic method is a method in which a magnet is embedded in a rotor and the rotation of the magnet is detected by a magnetic detection element such as a reed switch, a magnetoresistive element or a Hall element on the main body side and converted into an electric quantity and transmitted. Types of
The electromagnetic method is most widely used for unitless transmission because it has a relatively small effect on temperature and transmits stably. However, in the electromagnetic system, the number of pulses transmitted per rotor rotation is limited by the number of magnets, so that in a small flow meter, only one pulse or two pulses are transmitted per rotor rotation. Contrary to this, in the optical system, an encoder is attached to the end face of the rotor and the change in the light reflection amount is electrically converted to transmit, so the number of transmissions is determined by the number of slits engraved on the encoder, and the resolution is improved. Can be higher. However, in the optical method, the fluid to be measured must be light-transmissive, and in order to improve the resolution, the number of slits in the encoder is increased, so the slit width is also reduced, and this slit width can be discriminated. Since high resolution is required, the optical system will be expensive and adjustment will require skill,
At present, the electromagnetic system is superior as the actual operating volume because of problems such as high cost.

Problems of the prior art In the conventional unitless flow rate transmitter described above, in order to obtain a flow rate signal according to the purpose of flow rate measurement, the flow rate pulse is processed to obtain the instantaneous flow rate, or the flow rate is integrated as a unit flow rate. I got information about what to do. The instantaneous flow rate is displayed or transmitted by shaping the flow rate pulse into a constant peak value and pulse width, integrating the shaped pulse and converting it into an analog quantity, or converting it into a digital quantity proportional to the analog quantity. ing. However, there is a problem that the time delay increases when the flow rate is low and the number of pulses is small. Therefore, in order to increase the number of pulses in order to reduce the time delay, there is no choice but to adopt an optical method. It had to be an expensive detector.

Means for Solving Problems The volumetric flowmeter is a measuring means for measuring the liquid flow rate in many cases, and since the rotor rotates in the measuring chamber and the discharged fluid amount is the measured amount that is the discharge amount by one valve, The reliability of the measured value is high, and it is used for fluid trading and taxable measurement. When the flow rate is constant, since the liquid is incompressible, the rotor rotates with a constant angular velocity. The angular velocity of the rotor at this time is not constant, but the rotational velocity is uniquely determined if the specifications of the rotor are determined. An example of the angular velocity of rotation in the non-circular gear type flow meter is shown in FIG. As is clear from the figure, the rotor angular velocity is a periodic function with a period of 180 °. According to the present invention, this periodic function determines the angular velocity by the angle of the rotor if the specifications of the gear are determined, the average angular velocity, that is, the velocity ratio with the average flow velocity is determined, and in a minute time when the rotor makes one rotation. Is to calculate the velocity of a rotor at a certain angle by using the assumption that the flow rate is constant, and predict the flow velocity of the rotor in one half cycle or one cycle. In particular, the rotation angle section sandwiching P ₁ and P ₂ in FIG. 4 in which the rotation radii of the rotor are equal is a section representing the average flow velocity.

Example FIG. 2 is a plan view (II-II in FIG. 3) for explaining an example of mounting a transmitter in a positive displacement flow meter to which the present invention is applied.
FIG. 3 is a sectional view taken along line III-III of FIG.
In the figure, 1 is a flow meter casing, 2 is a metering chamber, 3 is an inlet, 4 is an outlet, 5 is an "O" ring groove, 6 and 7 are non-circular gear rotors (hereinafter referred to as rotors), 8 As is well known, the rotors 6 and 7 which receive the rotational torque by the fluid to be measured rotate in the direction of the arrow, and the fluid flows from the outlet 4 to the fluid outlet 4 in accordance with the rotation. Eject more. The flow rate is measured by multiplying the discharge amount by the rotation speed of the rotor. To rotate the rotor, a strip-shaped light reflecting plate 11 is fixed to the end face of one of the rotors 6 by adhesion or spot welding so that the light reflecting plate 11 is flush with the end face of the rotor 6. The reflected light is detected by the photodetector 12 as a pulsed optical signal. The photodetector 12 has the functions of light projection and light reception, and the received optical signal is converted into an electric pulse signal by a photoelectric converter (not shown).
The pulse width of the electric pulse signal is inversely proportional to the rotational angular velocity ω of the rotor 6. The rotation angular velocity ω of the rotor 6 is the photodetector 12
Is detected as a ratio with the average angular velocity according to the phase at the mounting position. When the photodetector 12 is arranged at the illustrated position on the fixed shafts 8 and 9, it is detected at an angular velocity of about 1.23. The pulse signal photoelectrically converted from the above optical signal is the input terminal of FIG.
The signal is input to 21, and the pulse is shaped by the amplification and shaping circuit 22 to open the AND gate 24. The AND gate 24 has an oscillator 23
The timing pulse output from the
Is counted by the integrator 27, and the count value C is input to the arithmetic circuit 29. In the arithmetic circuit 29, a reference value N corresponding to 1/2 of the rotor or the discharge amount per one rotation is set in the setting circuit 28 in advance. The arithmetic circuit 29 differentiates the input pulse that has been rectangularly shaped by the amplification and shaping circuit 22 in advance by the differentiating circuit 25, and resets the differentiated pulse at the rising portion of the input shaped pulse by the pulse signal shaped by the monomulti circuit 26. There is. Further, the rising signal of the input shaping pulse differentiated by the differentiating circuit 25 is made into a positive pulse by the inverter 30, and this is shaped into a minute width pulse by the monomulti 26,
The calculation result calculated in the previous cycle is reset, and the calculation result N / C of this time is newly set and stored via the monomulti 32 after a delay time td slightly longer than the calculation time, and the display circuit
Display or transmit to 34. When the flow rate is stopped or when the flow rate is extremely low, the photodetector 11 is stopped or is substantially stopped. Therefore, the signal from the photodetector 12 causes the gate 24 to open and counter.
27 overflows due to the timing pulse. As a result, the arithmetic unit 29 becomes inoperable. Overflow detector
Reference numeral 35 is for preventing this, and gives an instruction to the arithmetic unit 29 to detect an overflow and set the arithmetic result N / C = 0 of the arithmetic unit 29. In the above, the reference value N is selected as a value corresponding to the angular velocity of the rotor 6 at the detection position. However, when the meshing position between the rotors 6 and 7 is a meshing radius ρ ₁ = ρ ₂ as shown in FIG. Is the angular velocity ω in Fig. 4 P ₁
Since it indicates the average angular velocity of the position, if the light reflector 111 having the center with respect to the P ₁ position is attached to the end face of the rotor 6, the average angular velocity can be detected without correction. Second
In Fig. 5 and Fig. 5, a light reflector for detecting a representative angular velocity
Although 11 and 111 are used, a through hole that transmits light may be formed. In this case, the photodetector 12 is the light reflector 11 of the rotor 6.
Alternatively, it becomes a photodetector 12 (not shown) that emits and receives light through a hole passing through a through hole formed at the position 111. Further, a magnet may be embedded at the position of the light reflector 11 or 111, and a magnetic detecting means such as a Hall element for detecting a magnetic flux emitted from the magnet may be used. In either case, the rotation of the rotor may be detected within a partial phase angle range of the rotor. Further, although the present invention has been described as a non-circular gear type flow meter as a positive displacement flow meter, the present invention is not limited to this, and is also applicable to a loop flow meter, a vane type flow meter and the like.

Effect In the flow rate transmitter according to the present invention, the flowmeter rotor has an angular velocity / position curve in which the areal velocity is constant with respect to the constant flow rate discharged every 1/2 or one revolution according to the cycle of the curve. The rotational speed at which the rotor partially rotates,
The instantaneous flow rate can be displayed instantaneously by estimating and calculating the flow rate as the representative rotation speed in 1/2 or 1 rotation, and the instantaneous flow rate was calculated through several pulses by the transmission pulse with a low flow rate and a large pulse transmission interval. It is remarkably improved as compared with the prior art, and since the instantaneous flow rate is improved in response, many features such as cost reduction can be obtained without the need for an expensive pulse oscillator with high resolution.

[Brief description of drawings]

FIG. 1 is an electrical block diagram for explaining an embodiment of a flow rate transmitter according to the present invention, and FIGS. 2 and 3 are views for explaining an example of a positive displacement flow meter to which the present invention is applied. 4 and 5 are views showing the relationship of angular velocity phases for explaining the rotational angular velocity of the non-circular gear type flow meter, and FIG. 5 is a schematic diagram for explaining another embodiment of the present invention. 1 …… Flowmeter casing, 2 …… Weighing chamber, 3 …… Inlet, 4…
… Outlet, 5 …… “O” ring groove, 6,7 …… Non-circular gear rotor, 8,9 …… Rotating shaft, 10 …… End face plate, 11 …… Light reflector, 12…
… Photo detector.

Claims (3)

[Claims] 1. A flow rate transmitting element, which is disposed on the end faces of a pair of rotors that rotate in proportion to the flow rate of a fluid flowing into the measuring chamber of a volumetric flow meter, faces the transmitting element. Then, the time to pass through the detection element fixed to the main body is measured, and the flow rate corresponding to the measured time is stored and displayed or transmitted as a representative flow rate during one or two revolutions of the rotor. A characteristic flow transmitter. 2. The flow rate transmitter according to claim 1, wherein the rotor is a non-circular gear. 3. The flow rate according to claim 1, wherein the pair of non-circular gears meshing with the flow rate transmitting element are embedded at positions having the same radius vector. Transmitter.