JP2002181594A - Flow rate control unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce flow rate errors, improve the measurement accuracy, shorten the length of a pipe line and make the pipe line compact and low-cost by lessening effects by a turbulent flow and a drift. SOLUTION: A rectifying part 7 having an inner diameter D3 larger than an inner diameter D of a main pipe line 3 is set between a flowmeter 6 for measuring a flow rate of a fluid 2 and a proportional valve 8 for proportionally controlling the flow rate of the fluid 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow control unit and, more particularly, to an industrial or domestic city gas or LPG.
The present invention relates to a flow rate control unit suitable for controlling the flow rate of a combustion gas such as (liquefied fuel gas).

[0002]

2. Description of the Related Art Conventionally, as a flow control unit of this kind used for controlling a flow rate of a combustion gas such as a city gas or an LPG, a flow meter for measuring a flow rate of a fluid in a main pipe through which a fuel gas flows, 2. Description of the Related Art There is known a device provided with a proportional valve for proportionally controlling a flow rate. In the flow rate measurement, when the flow rate is adjusted by narrowing the flow path of the proportional valve, a turbulent flow is generated on the primary side (upstream side) and the secondary side (downstream side) of the proportional valve unless the opening degree is fully open or close to that. Therefore, the flow rate fluctuates in the flow meter. In addition, if the axis of the flow meter and the axis of the proportional valve are relatively eccentric, a drift occurs, so that the flow rate fluctuates.
Therefore, install the flow meter and the proportional valve at a certain distance or more,
They are not affected by turbulence or drift. The distance between the flow meter and the proportional valve is a distance required for the turbulent flow or the eccentric flow to become a steady flow.
It is necessary to be separated by about D times.

[0003]

As described above, in the conventional flow control unit, the flow meter and the proportional valve are connected to the inner diameter D of the pipe in order to prevent flow fluctuation due to turbulence and drift and to improve measurement accuracy.
Must be arranged at a distance of about 10 to 20 D times, the length of the conduit of the entire unit is inevitably increased, and the apparatus itself cannot be reduced in size, and a large installation space is required. Was. In addition, there is a problem in that the longer the pipe length, the higher the piping cost and the higher the manufacturing cost.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems. It is an object of the present invention to reduce the flow rate error by reducing the influence of turbulence and drift, thereby improving measurement accuracy. It is an object of the present invention to provide a flow control unit capable of shortening a pipe length, reducing the size, and reducing the cost.

[0005]

According to the present invention, there is provided a flow meter for measuring a flow rate of a fluid, and a proportional valve for proportionally controlling the flow rate of the fluid. A rectifier having an inner diameter larger than the inner diameter of the pipe is provided in the pipe between the meter and the meter.

In the present invention, the rectifying section rectifies turbulence and drift. Further, the energy of the reflected wave reflected on the primary side of the proportional valve is absorbed, and the influence on the flow meter is reduced. Therefore, the flow rate fluctuation is small, and the distance between the flow meter and the proportional valve can be reduced.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. 1 is a sectional view showing an embodiment of a flow control unit according to the present invention, FIG. 2 is a sectional view taken along line II-II of FIG. 1, FIGS. FIG. 4 is a cross-sectional view, FIG. 4 is a diagram showing a constant temperature difference circuit of the sensor, and FIG. 5 is a diagram showing a sensor output circuit.

In these figures, a flow control unit, generally designated by the reference numeral 1, has a pipe 4 forming a main pipe 3 for a fluid 2 such as fuel gas, and an upstream opening 5 of the pipe 4 A flow meter 6 is connected via a rectifying unit 7, and a proportional valve 8 and a throttle valve 9 for manually adjusting the valve opening of the proportional valve 8 are provided downstream of the upstream opening 5. The drive of the proportional valve 8 is controlled by the drive signal from the controller 10 based on the detection signal of the total 6.

The flow meter 6 measures the flow rate of the fluid 2,
The detection signal is output to the controller 10 and displayed by a liquid crystal display device (not shown).
The first and second flow path forming members 12 and 13 are formed in a cylindrical body having substantially the same shape, and are integrally connected to each other with a porous orifice plate (first restrictor) 11 described later interposed therebetween.
The first and second flow path forming members 12 and 13 have flow path holes 15 (15a, 15b) and 16 (16a, 16a,
16b), and the large-diameter holes 15b, 1
6b are integrally connected to each other so as to communicate with each other through the holes 11a of the porous orifice plate 11. The end of the first flow path forming member 12 on the side of the small-diameter hole 15a forms the upstream end of the flow meter 6 to form the pipe 1
4 is connected. The end of the second flow path forming member 13 on the side of the small-diameter hole 16 a forms the downstream end of the flow meter 6 and is connected to the rectifying section 7.

Further, the first and second flow path forming members 12,
Reference numeral 13 has annular chambers 17 and 18 formed on the joining end faces joined via the porous orifice plate 11 so as to surround the large-diameter holes 15b and 16b. These annular chambers 17 and 18 are connected to the large-diameter holes through gaps 22 and 23 formed between the partition walls 20 and 21 formed between the large-diameter holes 15b and 16b and the porous orifice plate 11, respectively. It communicates with the parts 15b and 16b. Furthermore, these annular chambers 17 and 18 are connected via a diversion channel 25 formed in a third channel forming member 24 fixed on the first and second channel forming members 12 and 13. Communicate with each other. Therefore, a part 2a of the fluid 2 flowing in the first flow path forming member 12 flows into the second flow path forming member 13 through the hole 11a of the porous orifice plate 11, and the remaining part 2b is Annular chamber 17 through gap 22
Shunted. The divided fluid 2b is supplied to the branch flow path 2
5, by flowing into the large-diameter hole portion 16b of the second flow path forming member 13 through the annular chamber 18 and the gap 23, it joins with a part of the fluid 2a passing through the hole 11a of the porous orifice plate 11.

The porous orifice plate 11 has a plurality of holes 11a formed at equal intervals on the same circumference spaced a required distance from the center.
The fluid 2 flowing inside is squeezed.

An orifice (second throttle) 30 and a micro flow sensor 31 are provided in the middle of the flow dividing channel 25. The orifice 30 restricts the fluid 2b flowing through the branch flow channel 25, and maintains the branch ratio of the fluid 2 accurately and stably together with the porous orifice plate 11. The orifice 30 has a perforated or single-hole orifice hole 30a. It is arranged on the upstream side of the micro flow sensor 31.

The micro flow sensor 31 is provided with a fluid 2
Is disposed in the branch flow channel 25 so as to be exposed, and detects heat transfer caused by the fluid 2b flowing through the hole 30a of the orifice 30 and in contact with the measurement unit. Thus, the relative flow velocity is detected at an extremely high response speed and even in a minute flow rate range. Such a micro flow sensor 31
For example, a semiconductor diaphragm type sensor shown in FIG. 3 is used. That is, the micro flow sensor 31 is provided with a diaphragm 34 provided on a silicon substrate 33.
One heating element (heater) 35 and two temperature sensors 36A and 36B constitute an indirectly heated temperature detecting means 37, and an ambient temperature sensor 38 for measuring an ambient temperature is provided outside the diaphragm 34. It is configured. Reference numeral 39 denotes a metal thin film for wiring, and reference numeral 40 denotes an electrode pad.

In FIG. 4, a heating element 35, an ambient temperature sensor 38, and three fixed resistors R1, R2, R3 form a Whiston bridge circuit, and a constant temperature difference circuit is formed by this and OP1. OP1 uses the Whiston bridge circuit, the midpoint voltage of the resistor R1 and the heating element 35 as an inverting input, and the midpoint voltage of the resistors R2 and R3 as a non-inverting input. The output of OP1 is commonly connected to one ends of resistors R1 and R2. The resistance values of the resistors R1, R2, and R3 are set so as to be always higher than the ambient temperature sensor 38 by a constant temperature.

The two temperature sensors 36A and 36B are:
The fixed resistors R4 and R5 form a Whiston bridge circuit as shown in FIG. 5, and are arranged on the upstream side and the downstream side in the flow direction of the fluid 2 with the heating element 35 interposed therebetween. OP2 forms a sensor output circuit.

In such a micro flow sensor 31, the fluid 2 is heated in a state where the heating element 35 is heated to a certain higher temperature than the ambient temperature by energizing the Whiston bridge circuit of the constant temperature difference circuit shown in FIG. When flowing in the direction of the arrow (FIG. 3), a temperature difference occurs between the temperature sensor 36A located on the upstream side of the heating element 35 and the temperature sensor 36B located on the downstream side. By detecting the difference or the resistance value difference, the flow velocity or flow rate of the fluid 2 can be measured.

In FIG. 1, the proportional valve 8 is opened in four directions connected in the middle of a pipe 4 and has an internal passage 42 (4).
2a, 42b) and the valve body 4
3 that is inserted into the cage 3 and controls the opening and closing of the flow passage 42
And a motor 45 with a speed reducer for rotating the cage 44 by a drive signal from the controller 10. The motor 45 is connected to the valve body 43 via a yoke 46.
Fixed on top. The valve body 43 has a cylindrical guide portion 47 provided integrally at the center of the inside and into which the cage 44 is slidably fitted. Openings 48a and 48b are formed to communicate the upstream passage 42a and the downstream passage 42b of the passage 42, respectively.

The cage 44 is formed in a cylindrical body whose lower surface is open and is attached to the lower end of a valve shaft 49. Two openings 50a and 50b (FIG. 2) face each other on the peripheral surface. It is formed so as to have a phase difference of 180 ° in the circumferential direction and correspond to the openings 48a and 48b. When the openings 50a and 50b coincide with the openings 48a and 48b due to the rotation of the cage 44, the proportional valve 8 is fully opened.
When a and b are closed by the peripheral wall of the cage 44, the cage is in a fully closed state. In FIG. 1, the opening 5 of the proportional valve 8
0a and 50b are rotated 90 degrees with respect to the openings 48a and 48b, and the opening degree is set to 0% (fully closed state).

The throttle valve 9 constitutes a composite valve together with the proportional valve 8. The throttle valve 9 uses the valve body 43 as a common component, and has a valve body 51 slidably fitted into the cage 44 from below. And a flow adjusting screw 52 for moving the valve element 51 up and down. The valve element 51 is formed in a cylindrical body and is screwed to the flow rate adjusting screw 52. The flow rate adjusting screw 52 is provided rotatably and vertically immovably through a mounting hole formed in a bottom plate of a cylindrical mounting portion 54 protruding from the center of the lower surface of the valve main body 43, and the valve is provided at the upper end side. Body 5
1 is screwed, and a nut 55 for preventing rotation is screwed on the lower end side. A cover 56 that normally covers the flow rate adjusting screw 52 is detachably attached to the lower surface of the attachment portion 54.

When the flow rate control unit 1 is installed, the cover 56 is removed, the nut 55 is loosened, the flow rate adjusting screw 52 is rotated, and the valve body 51 is moved up and down. , For example, 25% and 50%.

The rectifying section 7 is provided between the flow meter 6 and the pipe 4 and forms a part of a pipe. It is composed of a member 62 and two rings 63 disposed on both sides of the rectifying member 62. The inner diameter D1 of the cylindrical body 61 is set sufficiently larger than the inner diameter D2 of the outlet opening of the second flow path forming member 13 and the inner diameter D of the upstream opening 5 of the pipe 4 (D1> D, D2).

The rectifying member 62 is provided between the flow meter 6 and the pipe 4.
A flow velocity component in a direction perpendicular to the flow direction of the fluid 2 guided to the main conduit 3 to rectify the fluid 2 and a honeycomb structure having a large number of hexagonal holes or a thin corrugated plate Is used in a spiral form. The ring 63 has an appropriate width and an inner diameter D3, and is located between the downstream opening of the second flow path forming member 13 and the rectifying member 62 and between the rectifying member 62 and the upstream opening 5 of the pipe 4. Space 63
Is formed. The inner diameter D3 of the ring 63 is
2 and is set to be larger than the inner diameters D and D2 (D3> D, D2).

In such a flow control unit 1, the rectifying unit 7 is provided between the flow meter 6 and the proportional valve 8.
Of the flow generated when the opening of the flow meter is deviated from the center of the flow meter 6 and the influence of the turbulence generated when the flow is large when the flow rate is adjusted by narrowing the flow path by the proportional valve 8.
Function so as not to affect Therefore, the flow rate fluctuation of the fluid 2 flowing in the flow meter 6 is small, the flow rate can be measured with high accuracy, and the reliability of the flow rate control by the flow rate control unit 1 can be improved. The rectification unit 7
Is provided, the pipe length L between the flow meter 6 and the proportional valve 8 is reduced to about 3 to 5 times the diameter D of the upstream opening 5 of the pipe 4 (3D ≦ L ≦ 5D). Also, the influence of the turbulence is small, the flow control unit 1 can be reduced in size, and the manufacturing cost can be reduced.

FIG. 6 is a graph comparing the flow rate error between the flow rate control unit according to the present invention and a conventional flow rate control unit without a rectification unit. The measurement conditions were as follows: the valve opening of the proportional valve 8 was 30 °, and the opening of the throttle valve 9 was 25%. A curve a indicates a measurement error of the flow control unit 1 including the rectification unit 6 according to the present invention, and a curve B indicates a flow error of the conventional flow control unit without the rectification unit.

As is apparent from this figure, when there is no rectifying section, the opening (valve opening or throttle opening) of the proportional valve 8 is narrow, and when the flow rate exceeds 5 Nm ³ / h, the flow rate error rapidly increases. The flow rate is reduced from the actual flow value flowing through the flow meter 6. When the rectification unit 7 was provided, even if the flow rate increased, the flow rate error could be suppressed to within 3.5%.

[0026]

As described above, the flow control unit according to the present invention comprises a flow meter for measuring the flow rate of a fluid, and a proportional valve for proportionally controlling the flow rate of the fluid. Since a rectifying section having an inner diameter larger than the inner diameter of the flow path is provided in the pipe between the rectifying section and the rectifying section, the flow rate error due to turbulence and drift is reduced. Accuracy can be improved. In addition, the length of the conduit between the flow meter and the proportional valve can be reduced, and the size and cost of the device can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a flow control unit according to the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

3A and 3B are a plan view and a cross-sectional view of a micro flow sensor.

FIG. 4 is a diagram showing a constant temperature difference circuit of the flow sensor.

FIG. 5 is a diagram showing a sensor output circuit.

FIG. 6 is a graph comparing flow rate errors between a flow control unit according to the present invention and a conventional flow control unit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Flow control unit, 2 ... Fluid, 3 ... Main pipeline, 4 ... Piping, 6 ... Flow meter, 7 ... Rectifier, 8 ... Proportional valve, 9 ... Throttle valve, 10 ... Controller.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G01F 15/00 G01F 1/68 202A F-term (Reference) 2F030 CA10 CC13 CF01 CF05 CF08 CF09 2F031 AB09 2F035 EA05 EA08

Claims (1)

[Claims] 1. A flowmeter for measuring a flow rate of a fluid, and a proportional valve for proportionally controlling the flow rate of the fluid, wherein a pipe between the proportional valve and the flowmeter is provided with an inner diameter of the pipe. A flow control unit comprising a rectifying section having a large inner diameter.