JPH03123820A - Flow rate sensor and flowmeter for fluid and fluid supply device including them - Google Patents

Abstract

PURPOSE:To accurately meter impulsive fluid by constituting a metering part as a capacity type and providing a valve which is opened above constant pressure at or right behind the exit of the metering part. CONSTITUTION:When fluid which is discharged from a pump 40 exceeds the constant pressure with the internal pressure of the flow rate sensor 20 and flowmeter, the valve 27 provided at or right behind the exit 26 of the sensor 20 and flowmeter is opened, so that the fluid flows out. When the discharging flow velocity of the fluid from the pump 40 decreases owing to pulsation, the internal pressure of the sensor 20 and flowmeter falls to close the valve 27. Then when movable bodies 22 and 23 of the metering part 21 of the sensor 20 and flowmeter are to pass inertially, the fluid on the side of the exit 26 of the metering chamber is compressed by the motion of the movable bodies 22 and 23 because the valve 27 is closed, so the movable bodies 22 and 23 can not move and the excessive movement by inertia is suppressed. The accurate flow rate is sent or displayed without the excessive movement.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a flow rate sensor and a flow meter for measuring the flow rate of pulsating liquid, and a liquid supply device including the same.

[Prior art] Electromagnetic-driven metering pumps are used to inject small amounts of chemical liquids with high precision.The amount of injection is measured with a flow sensor and an electrical signal is sent, or the amount of injection is measured with a flowmeter. There is a desire to monitor the amount of injected liquid by displaying it as an image, but due to the principle of operation of electromagnetic metering pumps, the pulsation of the liquid delivered is large, so a flow rate sensor is required to measure the flow rate with a small error. We were unable to meet the requirements because we did not have a flowmeter or a flow meter.

If an impeller-based or positive displacement type is used as a flow sensor or flow meter, the impeller and flow meter will move excessively due to inertia due to pulsation, resulting in a very large positive measurement error, making it impractical for practical use. This is because it does not become.

Electromagnetic drive type metering pumps have a built-in electronic power circuit that intermittently passes a pulsed drive current to the solenoid coil, which generates an electromagnetic force that attracts the drive plunger. Push out the diaphragm. When the current is turned off, the attractive force disappears, and the action of the spring causes the drive plunger and diaphragm to return to their original positions.

This type of reciprocating movement of the diaphragm opens and closes the valves at the inlet and outlet, and the medicinal solution is repeatedly sucked in and discharged, and is also called a diaphragm two pump.

There are commercially available products that allow two-way control of the discharge amount at a ratio of about 50:1 using a combination of a pulse number adjustment dial and a stroke length adjustment dial.

As an example of a positive displacement flow sensor that can measure minute flow rates,
Twin rotary gear type flow sensors are well known.

In this device, a magnet is attached to the rotor, and a magnetic sensor is installed near the magnet, which moves as the rotor rotates, to convert the rotation of the rotor into an electrical signal and transmit it.
The details of the structure will be explained according to FIGS. 5 to 11.

In FIGS. 5 to 7, 1 is a case molded from thermoplastic resin, and a fluid inlet 2 and outlet 3 are integrally molded. In order to satisfy the strict value of 1/100 mm, which is the internal dimensional tolerance of the metering chamber required for a positive displacement flow sensor, this case 1 has been made to have a uniform wall thickness by sufficiently removing the wall thickness as shown in Figure 5. ing. Rotors 4 and 5 are movable bodies of the measuring section, and are molded from a thermoplastic resin having a coefficient of thermal expansion comparable to that of the case 1. Therefore, the gap with the case can be minimized over a wide temperature range, making it suitable for measuring minute flow rates.

6 and 7 are fixed metal shafts installed in the case 1, and one end (upper end) of each is protruded into the measuring chamber 8. The rotors 4 and 5 are fitted onto these fixed shafts 6 and 7, respectively, and are rotatably supported. Reference numeral 9 denotes an O-ring disposed in a groove provided on the upper surface of the case 1, and 10 denotes a cap which presses the O-ring 9 with its lower surface and abuts against the upper surface of the case 1. 11 and 1
Reference numerals 2 denote reinforcing plates made of metal plates that are in contact with the outside of the case 1 and the cover 10, that is, the bottom surface of the case 1 and the top surface of the cover 10, respectively. The cover 10 is molded from a thermoplastic resin having a coefficient of thermal expansion comparable to that of the case 1 and the rotors 4 and 5, and, like the case 1, is hollowed out to make the wall thickness uniform.

Reference numeral 13 designates screws for assembling the entire flow sensor by applying the reinforcing plates 11 and 12 from both sides of the case 1 and the cover 10, and tightening both reinforcing plates toward each other.

The reinforcing plates 11 and 12 are in contact with the outer peripheral sides of the case 1 and the cover 10, and the end faces of the lips 1a and 10a, respectively, and
and a cover 10, and the entire flow sensor is assembled without distortion.

14 is a magnet inserted into the hole 4a provided in the rotor 4,
It is held by a lid 15 that is fitted into a large diameter hole 4b provided at the entrance of the hole 4a and welded to the rotor, and is fixed so as not to move within the hole 4a.

Reference numeral 16 indicates a magnetic sensor arranged in a hollowed out portion of the cover 10 and adhesively fixed with a filler 16. Reference numeral 18 indicates a cord for extracting an electric signal from the magnetic sensor 16.

As shown in FIGS. 8 and 9, the rotor 4 as a movable body is an elliptical gear-shaped rotor having teeth on the outer periphery, and has a hole 4a that is open at the top and into which a magnet is inserted, and a hole that is slightly larger than this hole. It has a hole 4b into which the lid 15 is inserted. The diameter d of the hole 4a is the diameter of the cylindrical magnet 1, as shown in FIG.
It is set just slightly larger than the diameter of 4. In the same FIG. 10, the hole 4b into which the lid 15 is inserted is located at the entrance of the hole 4a, and its diameter is set to a diameter d2 that is slightly larger than the diameter of the lid 15. Further, the thickness T of the lid 15 is set to be slightly larger than the depth tl of the hole 4b. Then, attach the magnet 14 to the hole 4.
A, the distance L2 from the upper surface of the rotor 4, especially the upper surface 4C of the outer circumference of the hole 4b, to the upper surface of the magnet 14 is set to be equal to or slightly larger than the thickness T of the lid 15.

That is, these dimensions are t, <T≦tZ, d, <D≦d2 They have the following relationship.

The rotor 4 and lid 15 are made of weldable resin,
After inserting the magnet 14 into hole 4a, insert the lid 15 into hole 4.
b, and by ultrasonic welding, the symbol A is shown in Fig. 11.
As shown in , the abutting portions of the rotor 4 and the lid 15 are welded,
The upper end of the hole 4a of the rotor 4 is deformed to press down and hold the shoulder portion of the outer periphery of the upper surface of the magnet 4. At this time, the top surface of the lid 15 and the top surface of the rotor are flush with each other. Although the magnet 14 is magnetized in the diametrical direction, it is held and fixed by the deformed portion of the rotor or the lower surface of the cover 10 in this way, so that its direction does not change.

As shown in FIGS. 8 and 9, the rotor 4 has a rotor hole 4d into which a fixed shaft is fitted, and has stepped large diameter portions 4e and 4f at the upper and lower ends of the hole 4d, respectively. The large diameter portion 4e is
In the assembled state of the flowmeter, it acts as a relief opposite the upper end of the fixed shaft 6. Therefore, the value of the length f is determined so that the upper end of the fixed shaft 6 is located within the range occupied by the axial length P of the large diameter portion 4e. Similarly, the rotor 5 is provided with a large diameter portion 5e as a relief, which faces the upper end of the fixed shaft 7, on the upper surface of the rotor hole 5d. Furthermore, on the upper and lower surfaces of the rotor 4, sliding surfaces 4g' and 4g that can come into contact with the cover 10 and the case 1, respectively, are annularly provided in a small area around the large diameter parts 4e and 4f of the hole 4d. ing.

This sliding surface is slightly convex than the entire upper and lower surfaces of the rotor 4, and contacts the cover 10 and the case 1, respectively, but the contact area is small and the contact portion is close to the fixed shaft. Since it is a portion, it has the effect of reducing the frictional resistance between the rotor 4 and the cover 10 and case 1.

When fluid flows from the inlet 2 to the outlet 3 via the metering chamber 8, the rotors 4 and 5 rotate around fixed shafts 6 and 7, respectively, and the rotation of the magnet fixed to the rotor 4 causes the magnetic sensor 16 to rotate. is detected, converted into an electrical signal, and transmitted to the outside through the cord 18.

In addition, the gears on the outer periphery of both rotors 4 and 5 are meshed,
rotate at the same time. Further, the rotor 5 rotates while being supported by the fixed shaft 7 like the rotor 4, and the rotor 5 rotates while being supported by the fixed shaft 7 like the rotor 4.
It has a large-diameter portion 5e that faces the upper end and acts as a relief.

[Problem to be solved by the invention]

In the electromagnetic drive type metering pump (diaphragm pump), liquid is discharged every time the diaphragm makes a reciprocation, so the discharge flow rate pulsates greatly, and as shown in Fig. 12, the solenoid is driven intermittently at a cycle. (i.e. the operating period of the diaphragm) T.

The flow becomes an intermittent flow showing a maximum flow velocity 'IJ'-max at each time.

Therefore, at the outlet of this metering pump, the
When the discharge flow rate from the pump was measured by connecting the conventional twin-rotating gear type flow sensor explained according to Figure 1, the first
As shown in Figure 3, at small flow rates, an instrumental error of 6 to 7% occurred, making it impractical.

In addition, in Fig. 13, the pulse number adjustment diaphragm of the metering pump is set to 100% with the pulse number PC as a parameter.

50% and 10%, and use the stroke length adjustment diaphragm to adjust the stroke length ST to 20%, 50%, and 10%.
The data at each point was changed to 0%, and the numbers in parentheses in the figure indicate the number of pulses and the flow rate at the stroke length at that measurement point in units of lh.

In addition, on the scale of the pulse number adjustment dial, 100% PC is 153 shots/min, 50% is 69 shots/min,
10% corresponds to 16 shots/min.

Figure 13 shows that the smaller the number of pulses, that is, the number of shots per minute, the larger the positive instrumental error becomes, and the smaller the flow rate, that is, the average flow velocity, the larger the positive instrumental error becomes. The relationship between numbers and instrumental differences in the 14th
FIG. 15 shows the relationship between the average flow velocity Q and the instrumental error. The relationship between the maximum flow velocity 'Ifmax and the instrumental error is as shown in FIG. 16.

Figure 13 shows flow rates of 0.08 to 3.70 ffi/h.
Although the actual measured values are in the range of , the instrumental error fluctuates in the range of 1% to 7%, and does not exhibit the small measurement error inherent to the twin-rotating gear flow sensor.

Furthermore, even if a twin-rotary gear type flowmeter is used, in which a display device for displaying the flow rate integrated value is attached to the twin-rotary gear type flow sensor, a large positive meter difference will still occur at a small flow rate.

Also, when using a metering pump, it would be easier and more convenient to use if a flow rate sensor or flow meter that can accurately check the discharge flow rate is attached to the metering pump itself. There was a problem that the feeding device could not be put into practical use.

Therefore, an object of the present invention is to propose a flow rate sensor and a flow meter that can accurately measure pulsating liquid.

Another object of the present invention is to provide a liquid supply device in which a pulsating discharge amount can be accurately confirmed by integrally attaching such a flow rate sensor or a flow meter.

[Means to solve the problem]

In order to achieve the above object, the flow rate sensor for liquid according to the present invention includes means for detecting the movement of the movable body (22, 23) of the measuring section (21), converting it into an electric signal, and transmitting the signal to the outside. In the flow rate sensor (20), the metering part (21) is of a positive displacement type, and an outlet (26) or a valve (27) that opens at a certain internal pressure or more is provided immediately after the outlet.

In addition, in order to achieve the above object, the liquid flowmeter of the present invention includes a display device that integrates and displays the movement of the movable body (22, 23) of the measuring part (21). The measuring part (21) is of a positive displacement type, and is provided with an outlet (26) or a valve (27) that opens at a certain internal pressure or more immediately after the outlet.

Furthermore, in order to achieve the above object, the liquid supply device of the present invention includes an inlet (25) of the flow rate sensor (20) according to claim 1 at the discharge port of the fluid pump (40) whose discharge flow rate is pulsating.
), and the flow rate sensor (20) was integrally attached to the fluid pump (40).

The liquid supply device may use the flow meter according to claim 2 instead of using the flow rate sensor according to claim 1.

[Effect]

When the liquid discharged from the pump reaches a certain pressure or higher due to the internal pressure of the flow rate sensor or flow meter, a valve provided at or immediately after the outlet of the flow rate sensor or flow meter opens and the liquid flows out.

When the discharge flow rate from the pump decreases due to pulsation, the internal pressure in the metering chamber of the flow rate sensor or flow meter decreases and the valve closes. After this, if the movable body of the metering part of the flow rate sensor or flowmeter tries to move too far due to inertia, the valve will be closed, and the liquid on the outlet side of the metering chamber will be compressed by the movement of the movable body, causing the movable body to move. This prevents overshooting due to inertia. Therefore, an accurate flow rate without excess is transmitted or displayed.

Even if the flow rate sensor according to claim 1 or the flow meter according to claim 2 is attached to a pump for liquid whose discharge flow rate is pulsating, the same operation will be performed, so that the discharge amount of the pump can be confirmed.

〔Example〕

In FIG. 1, reference numeral 20 indicates the entire flow rate sensor, 21 is a twin-rotary gear type measuring section with a large capacity, and two rotors 22.
23 mesh and rotate within the measuring chamber 24.

25 is the inlet, 26 is the outlet, and 27 is the outlet side 2 of the measuring chamber 24.
A valve that opens when the internal pressure of 4a exceeds a certain level (1 kgf/cnl) and allows liquid to pass from the outlet 2G to the outside (to the right in the figure), and is provided at the outlet 26 and cooperates with the seat section 28. It is composed of a ball 29 and a spring 30 that presses the ball 29 against the seat portion 28. The details of the structure of the measuring section 21 are the same as the conventional twin-rotating gear type flow sensor, and the movement of the magnet attached to the rotor is detected by a magnetic sensor and converted into an electric signal, and the rotation of the rotor is transmitted to the outside. (The corrective structure is also the same, but these are omitted in Figure 1.

The embodiment of FIG.
The valve casing 31 is screwed onto the outlet 26.Although a valve 27 is disposed immediately after the outlet 26, its operation is almost the same as that of the embodiment shown in FIG. It is clear from the above description of the operation that in any of the embodiments, the smaller the volume of the passage 32 communicating with the outlet side 24a of the metering chamber 24 up to the valve 27 is, the more effective it is.

The embodiment shown in FIG. 3 shows a liquid supply device and its performance test device of the present invention, and 20 is a flow rate sensor equipped with a valve 27, which opens at a constant internal pressure of 1 kgf/ca or more to drain the liquid from the outlet. Pass downstream. Reference numeral 40 denotes a diaphragm pump, and the flow rate sensor 20 is integrally attached to this pump, and the inlet of the flow rate sensor 20 is connected to the discharge port of the pump 40. This diaphragm pump uses the diaphragm pump mentioned and explained in the [Prior Art] section and the [Problem to be Solved by the Invention] section. 41 is a water storage tank, 42 is a suction pipe; A strainer 43 is attached to the inlet end, and the supply pipe is placed into water in the water storage tank 41. 44 is a supply pipe, one end of which is connected to the outlet of the valve 27 provided on the flow rate sensor 20, and the opening of the other end is connected to the metering tank 45. 46 measures the amount of water in the measuring tank using an electronic scale.

The flow rate sensor 20 provided with the valve 27 and the diaphragm pump 40 together constitute a liquid supply device 50 .

In this liquid supply device 50, the pulse number PC was changed with the pulse number adjustment dial of the diaphragm pump 40, and the stroke length ST was changed with the stroke length adjustment dial, and the instrumental error under several conditions was measured. As shown in the figure, it was within ±1%.

Comparing this result with the performance of the prior art shown in FIG. 13, the improvement effect of the present invention is clear.

Although a specific example of the flow meter of the present invention and a liquid supply device using the flow meter is not shown, the present invention can be realized by providing a well-known flow rate integration display to the flow rate sensor shown in FIGS. 1 and 2. If the flow meter of the invention can be realized, the flow meter is integrally attached to a liquid pump, and the inlet of the flow meter is connected to the discharge port of the pump, the liquid supply device according to claim 4 can be realized.

In the above explanation, we have given an example of a twin-rotary gear type using an elliptical gear as a flow rate sensor or flow meter with a volumetric measuring part, but there are also positive displacement types such as Roots type and rotary piston type. You can also use

[Effect of idea]

Since the present invention is configured as described above, the movable body of the measuring section is prevented from moving too far due to the pulsation of the liquid, and as a result, the flow rate of the pulsating liquid is accurately measured, transmitted, and displayed. It became possible to do so.

In addition, a liquid supply device that can accurately measure and confirm the discharge amount of a pulsating liquid pump has been realized.

[Brief explanation of drawings]

FIGS. 1 and 2 show different embodiments of the flow rate sensor of the present invention, both of which are top views with the cover removed, and some of which show horizontal cross sections. FIG. 3 is a partial longitudinal perspective view of the liquid supply device of the present invention and its performance test device, FIG. 4 is a line diagram showing the performance test results of the device of FIG. 3, and FIGS. An example of a flow rate sensor, Fig. 5 is a longitudinal sectional view, Fig. 6 is a top view, Fig. 7 is a side view, Fig. 8 is an enlarged top view of the rotor, Fig. 9 is an enlarged longitudinal sectional view of the rotor, and Fig. 9 is an enlarged longitudinal sectional view of the rotor. Figure 10 is an enlarged vertical cross-sectional view illustrating the assembly of the magnet and lid to the rotor, Figure 11 is an enlarged vertical cross-sectional view of the part where the magnet is assembled to the rotor, and Figure 12 is the pulsation of the liquid discharged from the diaphragm pump. Figure 1 showing
Figure 3 is a diagram showing the instrumental error when measuring pulsating flow with a conventional flow sensor, and Figures 14, 15, and 16 show the number of pulses and pulses when measuring pulsating flow with a conventional flow sensor. FIG. 3 is a diagram showing the relationship between instrumental error, average flow velocity and instrumental error, and the relationship between maximum flow velocity and instrumental error, respectively. 20...Flow rate sensor, 21...Measuring part, 22.23
...Movable body (rotor), 25...Inlet, 26...
Outlet, 27...Valve, 40...Liquid pump (diaphragm pump), 50...Liquid supply device i? in Figure 1 of the drawing. )] Fig. 2 20...Gain amount sensor 21...Needle amount section 22.23...Rotor 24...Blind amount 1 Otsu 25...Inlet 26...Outlet 27...Valve 40...Diaphragm pump 50...Diaphragm pump 50...Fig. Figure 8 Figure 9 Figure 10 Figure 11 Figure 5 November 17, 1999

Claims (1)

[Claims] 1. In a flow rate sensor (20) equipped with a means for detecting the movement of the movable body (22, 23) of the measuring section (21), converting it into an electric signal and transmitting it to the outside, the measuring section ( 21) is a positive displacement type, and is provided with an outlet (26) or a valve (27) that opens immediately after the outlet at a certain internal pressure or higher. 2. In a flowmeter equipped with a display that integrates and displays the movements of the movable bodies (22, 23) of the measuring section (21), the measuring section (21) is of a positive displacement type, and the outlet (26) or A fluid flowmeter equipped with a valve (27) that opens when the internal pressure exceeds a certain level immediately after the outlet. 3. Connect the inlet (25) of the flow rate sensor (20) according to claim 1 to the discharge port of the fluid pump (40) whose discharge flow rate is pulsating, and connect the flow rate sensor (20) to the fluid pump (40).
0) is integrally attached to the fluid supply device. 4. The inlet (25) of the flow meter according to claim 2 is connected to the discharge port of the fluid pump (40) whose discharge flow rate is pulsating, and the flow meter is integrally attached to the fluid pump (40). Liquid supply device.