JP3841599B2 - Ultrasonic liquid flow detection sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a clamp-on type ultrasonic liquid flow rate detection sensor that is attached to the outside of a fluororesin pipe through which a fluid to be measured flows and detects a flow rate.
[0002]
[Prior art]
The method of measuring the fluid flowing in the pipe with ultrasonic waves is to place ultrasonic liquid flow rate detection sensors on the upstream and downstream sides of the pipe so as to face each other, transmit and receive ultrasonic pulses, and determine the arrival time. In this method, the flow rate is measured by detecting the flow velocity based on the difference.
[0003]
Conventionally, in the case of this method, materials such as acrylic and epoxy are used for the shoe of the ultrasonic liquid flow detection sensor that comes into contact with the pipe, and this is used as a small-diameter pipe of PFA resin used in semiconductor cleaning devices and the like. When attached, the sound wave entering the PFA resin pipe from the shoe is refracted in the direction perpendicular to the pipe due to the difference in the material of the shoe and the pipe, so the distance (span) between the sensors cannot be increased and the measurement accuracy can be improved. could not.
[0004]
Conventionally, the ultrasonic liquid flow rate detection sensor is fixed to the pipe using a wire band or the like, but in this case, there is an advantage that it can cope with any pipe diameter. There is a problem that alignment must be performed each time. In the ultrasonic flowmeter, the position of the sensor is important, and if the alignment is not performed accurately, the measurement accuracy is greatly affected.
[0005]
Therefore, when measuring a small flow rate with ultrasonic waves, such as in the field of semiconductor substrate cleaning, a dedicated flow rate measuring device as shown in FIG. 8 is used instead of the clamp-on type. In this measuring device, the flow path 81 of the detection unit 80 is formed in a “U” shape, and the liquid flowing in from the inlet 81a is bent 90 degrees, passes through the measuring tube 81b, and is again bent 90 degrees from the outlet 81c. It is configured to flow out. Ultrasonic transducers 82 for transmitting and receiving ultrasonic waves are attached to both ends of the measurement tube 81b, and the flow rate is obtained from the pipe dimensions and the like based on the detection signals from these ultrasonic transducers 82. .
[0006]
[Problems to be solved by the invention]
However, when this flow meter is used, the existing pipe must be cut and connected to the detector, which may introduce impurities into the pipe, and the measuring pipe has a 'U' shape. Therefore, there is a problem that a liquid pool is likely to be generated at the corner portion, and impurities may be accumulated and an aqueous solution may be deposited.
[0007]
An object of the present invention is to provide an ultrasonic liquid flow rate detection sensor that can be installed without cutting existing piping, can have a large span, and can be easily positioned between ultrasonic transducers. .
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the present invention employs the following means.
The ultrasonic liquid flow rate detection sensor according to claim 1 is arranged opposite to the front and back of the pipe formed of fluororesin, and detects the flow rate of the fluid flowing into the pipe from the time difference by transmitting and receiving ultrasonic waves. An ultrasonic liquid flow rate detection sensor having a rectangular parallelepiped shape, a concave portion having a rectangular cross section formed in the longitudinal direction of the back surface thereof, and an engaging portion protruding outward in a portion other than the concave portion, and the engagement A sensor holder having a locking portion formed of a concave portion having the same shape as the portion, and a portion of the concave portion having a square cross section of the sensor holder that is formed of the same fluororesin as that of the pipe, A feature is that a shoe formed on the same curved surface as the outer periphery is inserted .
[0009]
The ultrasonic liquid flow rate detection sensor according to claim 2 is characterized in that, in the invention according to claim 1, the surface to which the ultrasonic transducer of the shoe is attached is set to 50 degrees to 58 degrees with respect to the piping surface. Yes.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment of an ultrasonic liquid flow rate detection sensor according to the present invention will be described with reference to the drawings.
FIG. 1 is a diagram for explaining in principle the state in which the ultrasonic liquid flow rate detection sensor 10 is clamped on the pipe 50, where (a) is a side view and (b) is a front view. However, the lower sensor 10 is omitted in FIG. As shown in the drawing, the pipe 50 has a uniform diameter, and is formed of a chemical-resistant fluororesin (PFA) for transporting a semiconductor-related cleaning liquid. The shoe 11 of the ultrasonic liquid flow rate detection sensor 10 clamped on the pipe 50 is formed of the same fluororesin (PTFE) as the pipe 50, and the portion 11 a that contacts the pipe 50 is the same as the outer periphery of the pipe 50. A curved surface, that is, a curved surface having the same curvature as that of the outer surface of the pipe 50 is formed. For this reason, the shoe 11 is in close contact with the outer surface of the pipe 50. An ultrasonic transducer 12 is attached to the side surface 11 b of the shoe 11, and the side surface 11 b has an inclination angle θ with respect to the outer surface of the pipe 50.
[0012]
As described above, since the shoe 11 made of the same material (PTFE) is used for the fluororesin (PFA) -based pipe 50, the sensitivity of the ultrasonic wave reception that is favorable in measuring the flow rate can be obtained. This is because the acoustic characteristics of the shoe 11 and the pipe 50 are close or the same, so that the reflection of ultrasonic waves between the shoe 11 and the pipe 50 hardly occurs, and the ultrasonic waves are efficiently incident on the liquid in the pipe 50. By. Furthermore, since the speed of sound propagating in the fluororesin is relatively slow, about 1300 m / s, when the object to be measured is specified to have a faster propagation speed than fluororesin such as water or aqueous solution, the midpoint of the pipe 50 is propagated. Since the sound wave path takes the shortest time, the zero gloss point of S1 used for flow rate measurement is not disturbed by the received waves that have propagated through other paths. Therefore, by multiplying an appropriate correction coefficient, it becomes possible to measure the flow rate with higher accuracy.
[0013]
Further, at this time, the incidence angle of the ultrasonic wave is refracted so as to be an acute angle with respect to the central axis of the pipe based on Snell's law, so that the interval between the transmission / reception sensors 10 can be widened. This leads to more accurate flow measurement.
[0014]
As an example, PTFE is used as the material of the shoe 11, PFA is used as the material of the pipe 50, and water is put into the pipe 50, and the relationship between the inclination angle θ of the side surface 11 b of the shoe 11 and the receiving sensitivity of the ultrasonic transducer is tested. The result shown in FIG. 2 was obtained. Stable receiving sensitivity can be obtained when the inclination angle θ of the ultrasonic transducer 12 mounting surface of the shoe 11 is in the range of 50 ° to 58 °. It was found that when the inclination angle was less than 50 °, the span between the ultrasonic liquid flow rate detection sensors 10 could not be obtained, and when it exceeded 58 °, the sensitivity suddenly decreased. The diameter of the pipe 50 is 6.35 mm. Further, since the portion 11a that contacts the pipe 50 of the shoe 11 is formed on the same curved surface as the outer periphery of the pipe 50, the flow rate can be measured with high accuracy by improving the receiving sensitivity and the S / N ratio. .
[0015]
Next, a second embodiment will be described.
This ultrasonic liquid flow rate detection sensor includes a sensor holder 23 shown in FIG. 3 and a shoe 21 to which an ultrasonic transducer 22 shown in FIG. 4 is attached. 3A is a perspective view of the sensor holder 23 as viewed from the bottom, FIG. 3B is a perspective view of the sensor holder 23 as viewed from above, FIG. 4A is a plan view of the shoe 21, and FIG. Sectional drawing by the BB line | wire, (c) is a front view, (a) is seen from the arrow C direction. The sensor holder 23 is made of plastic such as vinyl chloride, and the shape of the sensor holder 23 is substantially a rectangular parallelepiped shape. The sensor holder 23 is provided with grooves 23a that are slightly recessed along both longitudinal ends of the center of the back surface. A recess 23b having a square cross section is formed in the groove 23a. Further, a pair of columnar engaging portions 23 c are provided in the raised portions on both sides of the groove 23 a on the back surface and in the vicinity of the end of the sensor holder 23.
[0016]
Similarly, a locking portion 23d made of a concave portion having the same shape as the engaging portion 23c is formed in the raised portions on both sides of the groove 23a on the back surface and in the middle between the center portion and the end portion of the sensor holder 23. Has been. The locking portion 23d penetrates the front and back of the sensor holder 23. Further, the sensor holder 23 is provided with a circular through hole 23e at the center, a circular through hole 23f with a screw groove formed at the end, and between the side surface and the upper surface. Four rectangular holes 23g that pass therethrough are provided.
[0017]
Next, the shoe 21 fitted into the sensor holder 23 will be described. As shown in FIG. 4, the shoe 21 is composed of a main part 21 a having a trapezoidal shape in a side view and a flat plate-like sub part 21 b extending horizontally from the main part 21 a. One side surface 21c in the longitudinal direction of the main portion 21a is formed perpendicularly, and the other side surface 21d has an inclination angle θ of 58 ° with respect to the bottom surface, and the ultrasonic transducer 22 is bonded thereto. It is attached. Further, as shown in FIG. 4C, the bottom surface portion 21e of the main portion 21a is formed in a curved surface and has a curved surface having substantially the same curvature as the curved surface of the outer surface of the pipe through which the liquid to be measured passes. . Further, a screw hole 21f is provided on the upper surface of the main portion 21a, and the screw hole 21f inserts a screw from the through hole 23e of the sensor holder 23 when the shoe 21 is inserted into the sensor holder 23. The shoe 21 is screwed into the screw hole 21f to fix the shoe 21 to the sensor holder 23.
[0018]
FIGS. 5A and 5B show the ultrasonic liquid flow rate detection sensor 20 in a state where the shoe 21 is inserted into the sensor holder 23, where FIG. 5A is an exploded view and FIG. 5B is a diagram showing a completed state. The shoe 21 is fitted into the recess 23 b of the sensor holder 23 and fixed with screws 24. At this time, both sides of the sub part 21 b of the shoe 21 are supported by a part of the groove 23 a of the sensor holder 23. Further, the wiring 25 connected to the ultrasonic transducer 22 is drawn out through the center of a cap 26 that closes the hole 23 f of the sensor holder 23.
[0019]
Next, a method of using the ultrasonic liquid flow rate detection sensor 20 will be described. As shown in FIG. 6, the pair of ultrasonic liquid flow rate detection sensors 20 are turned upside down so as to sandwich the pipe 50, and the engaging portions 23 c are inserted into the mating locking portions 23 d. The pipe 50 is sandwiched from both sides by the bottom surface portion 21e of the shoe 21 of the sensor 20 on both sides. Thus, the positioning of the ultrasonic liquid flow rate detection sensor 20 arranged to oppose the upstream side and the downstream side can be easily performed with one touch.
[0020]
Subsequently, as shown in FIG. 7, the two sensors 20 are tightened through the band 30 in the holes 23 g formed in the sensor holder 23 so as not to be detached. The band 30 may be used when bundling a large number of wires. If the band 30 can be locked and unlocked, the band 30 can be removed when the measurement of the flow rate is completed, which is more convenient.
[0021]
As described above, the sensor 20 can be attached to the pipe 50 very easily and the mounting accuracy is improved, and the shape of the sensor holder 23 is the same on both the upstream side and the downstream side. Since the mounting structure is used, only one type of mold for forming the sensor holder 23 is required, and the cost can be reduced.
[0022]
【The invention's effect】
As described above, since the ultrasonic liquid flow rate detection sensor according to the present invention is a clamp-on type, the flow rate detection work becomes easier and the flow rate detection work becomes easier than the conventional semiconductor cleaning liquid level detection sensor that is cut and installed on the existing piping. Since the same fluororesin is used for the pipe, the span can be increased due to the reflection and refraction of sound waves, and the flow rate can be measured with high accuracy.
[0023]
Moreover, since the attachment to the piping is simple and the positioning is easy, the working time can be shortened. Furthermore, since the upstream and downstream sensor holders can be made from one type of mold, the cost can be reduced.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram in which a first embodiment of an ultrasonic liquid flow rate detection sensor according to the present invention is attached to a pipe, (a) is a side view, and (b) is a front view.
FIG. 2 is a diagram showing a relationship between an angle of an ultrasonic transducer mounting surface of a shoe and received wave sensitivity.
3A is a perspective view of the sensor holder as viewed from the bottom, and FIG. 3A is a perspective view of the sensor holder as viewed from the top.
4A and 4B show the shape of a shoe, where FIG. 4A is a plan view, FIG. 4B is a cross-sectional view taken along line BB in FIG. 4A, and FIG.
FIG. 5 is an exploded view of the shoe and the sensor holder, and FIG.
6 is a view for explaining a state in which the ultrasonic liquid flow rate detection sensor of the second embodiment shown in FIG. 5 is attached to a pipe.
FIG. 7 is a diagram in which an ultrasonic liquid flow rate detection sensor is attached to a pipe and fastened with a band.
FIG. 8 is a diagram showing an operation principle of a detector for measuring the flow rate of a semiconductor cleaning liquid that has been used conventionally.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Ultrasonic liquid flow rate detection sensor 11 Shoe 11a Part which contact | abuts piping 12 Ultrasonic vibrator 20 Ultrasonic liquid flow rate detection sensor 21 Shoe 22 Ultrasonic vibrator 23 Sensor holder 23b Recess 23c Engagement part 23d Engagement part 50 Piping

Claims (2)

An ultrasonic liquid flow rate detection sensor that is arranged opposite to the front and back of a pipe formed of fluororesin, detects the flow rate of the fluid flowing in the pipe from the time difference by transmitting and receiving ultrasonic waves,
A rectangular parallelepiped-shaped recess having a rectangular cross section in the longitudinal direction of the back surface, and having an engaging portion projecting outward in a portion other than the recessed portion, and comprising a recess having the same shape as the engaging portion. A shoe that is formed of the same fluororesin as that of the pipe, and a portion that contacts the pipe is formed on the same curved surface as the outer periphery of the pipe. An ultrasonic liquid flow rate detection sensor which is inserted and inserted . 2. The ultrasonic liquid flow rate detection sensor according to claim 1 , wherein a surface of the shoe to which the ultrasonic vibrator is attached is set to 50 ° to 58 ° with respect to a piping surface .

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