JP5131815B2 - Ultrasonic flow meter - Google Patents

Description

  The present invention transmits and receives ultrasonic waves in a direction obliquely intersecting the axial direction of the measurement pipe between a pair of ultrasonic sensors attached to the upstream side and the downstream side of the measurement pipe through which the fluid flows. The present invention relates to an ultrasonic flowmeter for measuring a flow rate.

In the conventional ultrasonic flowmeter 1 shown in FIG. 13, bottomed holes 4 and 4 for accommodating the ultrasonic sensors 3 and 3 are formed in the outer surface of the measurement tube 2 so as to be recessed, and the measurement tube is formed at the bottom thereof. Sensor contact surfaces 5 and 5 are provided which are inclined with respect to the axis 2 and to which the ultrasonic sensors 3 and 3 are in close contact. The bottomed holes 4 and 4 are sealed by plug members 6 and 6 fitted and fixed behind the ultrasonic sensors 3 and 3 (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 7-91997 ([0008], FIG. 1)

  However, in the conventional ultrasonic flowmeter 1 described above, the plug fitting portions 4a and 4a into which the plug members 6 and 6 of the bottomed holes 4 and 4 are fitted are perpendicular to the sensor contact surfaces 5 and 5, respectively. I was facing. In other words, since the plug fitting portions 4a, 4a extend in a direction inclined with respect to the axial direction of the measuring tube 2, there is a problem that the entire length of the measuring tube 2 becomes unnecessarily long.

  This invention is made | formed in view of the said situation, and it aims at provision of the ultrasonic flowmeter which can make the full length of a measuring tube shorter than before.

In order to achieve the above object, an ultrasonic flowmeter according to the first aspect of the present invention provides a measuring tube between a pair of ultrasonic sensors attached to an upstream side and a downstream side of a measuring tube through which a fluid flows. An ultrasonic flowmeter that measures the flow rate of a fluid by transmitting and receiving ultrasonic waves in a direction that obliquely intersects the axial direction, and is a depression formed on the outer surface of a measurement tube and accommodates a pair of ultrasonic sensors a sensor housing recess pair, provided at the bottom of each sensor housing recess inclined with respect to the axial direction of the measuring tube, and the sensor contact surface transmitting and receiving surface of the ultrasonic sensor are in close contact, said each sensor housing recess Of these , the plug member that is fitted and fixed to the plug fitting part and sealed with the sensor housing recess can be fitted to the plug fitting part from the direction perpendicular to the axial direction of the measuring tube. The plug member is fitted with a plug body fitted in contact with the inner surface of the plug fitting portion. A sensor pressing surface formed at the tip of the plug body and substantially parallel to the sensor contact surface, and a collar portion protruding laterally from the rear end of the plug body and screwed to the opening edge of the sensor housing recess, An elastic member is provided between the sensor pressing surface and the ultrasonic sensor to compress and press the ultrasonic sensor against the sensor contact surface by the elastic force, and the elastic force applied from the elastic member to the plug member is provided. Of these, a component of force perpendicular to the fitting direction of the plug member is received by the contact between the inner surface of the plug fitting portion and the plug member . Note that the present invention includes one having at least one pair of ultrasonic sensors.

Tip of the invention of claim 2, in the ultrasonic flowmeter according to claim 1, a flow rate computation display for displaying by calculating the flow rate based on the output signal of the ultrasonic sensor, and protrudes from the outer surface of the measuring tube A fixing wall for fixing the flow rate calculation display to the section, a wiring processing recess formed inside the fixing wall and closed by the flow rate display, a wiring processing recess and a sensor receiving recess in the measurement tube, It has a feature in that it has an internal electric wire passage through which a connecting line between the ultrasonic sensor and the flow rate calculation indicator is passed.

The invention according to claim 3 is the ultrasonic flowmeter according to claim 1 or 2, wherein the sensor contact surface is provided with a concave portion and a convex portion, and only the convex portion is brought into close contact with the wave transmitting / receiving surface of the ultrasonic sensor. It has features.

According to a fourth aspect of the present invention, in the ultrasonic flowmeter according to any one of the first to third aspects, the transmission / reception surfaces of the pair of ultrasonic sensors are not parallel when the measurement tube is viewed from the axial direction. And is characterized in that the propagation path of the ultrasonic wave reflected by the transmission / reception surface of one ultrasonic sensor is shifted from the other ultrasonic sensor.

According to a fifth aspect of the present invention, in the ultrasonic flowmeter according to any one of the first to fourth aspects, the fluid is a gas, and one ultrasonic sensor has a fixed directivity angle from the other ultrasonic sensor side. It is characterized in that it is arranged on the side away from the other ultrasonic sensor with respect to the central portion of the region where the ultrasonic wave reception intensity is highest among the receivable ultrasonic wave propagation regions.

A sixth aspect of the invention is the ultrasonic flowmeter according to any one of the first to fifth aspects, further comprising a pair of sensor mounting convex portions protruding from the outer surface of the measuring tube, and the core portions of the sensor mounting convex portions are provided. It is characterized in that it is depressed to form a sensor receiving recess.

[Invention of Claim 1]
According to the first aspect of the present invention, the ultrasonic sensor is inserted into the sensor receiving recess formed in the outer surface of the measuring tube so as to be in close contact with the sensor contact surface, and is inserted into the sensor receiving recess so as to overlap the ultrasonic sensor. The sensor housing recess is sealed by the fitted plug member. The sensor contact surfaces are provided in advance with an inclination with respect to the axis of the measuring tube, and the pair of ultrasonic sensors are brought into close contact with the sensor contact surface, so that the pair of ultrasonic sensors are ultrasonic waves. Is positioned at a position where wave can be transmitted and received. Between a pair of ultrasonic sensors, ultrasonic waves are transmitted and received in a direction obliquely intersecting the axis of the measurement tube, and the flow rate of the fluid is measured based on the propagation time. And according to invention of Claim 1, since a plug member can be fitted to a plug fitting part from the direction orthogonal to the axial direction of a measurement pipe, a plug fitting part is with respect to the axial direction of a measurement pipe. The total length of the measuring tube can be shortened as compared with the conventional one extending in an inclined manner.

Further, according to the invention of claim 1, the plug member, while compressing the elastic member to and from the sensor pressing surface and the ultrasonic sensor provided at the distal end of the plug body fitted to the stopper engaging portion, It is fixed by screwing a flange projecting laterally from the rear end of the plug body to the opening edge of the sensor housing recess. Thereby, the ultrasonic sensor is pressed against the sensor contact surface by the elastic force of the elastic member.

Here, since the plug body of the plug member is fitted in contact with the inner surface of the sensor receiving recess, the fitting direction of the plug member among the elastic force applied from the elastic member to the plug member The orthogonal force component can be received by the contact between the inner surface of the plug fitting portion and the plug member. Therefore, it is possible to suppress the strength required for the screwed portion between the flange portion and the opening edge of the sensor housing recess.

[Invention of claim 2 ]
According to the second aspect of the present invention, the connection line between the ultrasonic sensor and the flow rate calculation indicator passes through the internal wire passage that penetrates the wall portion between the wiring processing recess and the sensor receiving recess in the measurement tube. Therefore, disconnection of the connection line can be prevented.

[Invention of claim 3 ]
According to the invention of claim 3 , it is possible to reduce the measurement error as compared with the case where the entire transmission / reception surface of the ultrasonic sensor is brought into close contact with the sensor contact surface. The reason is as follows.

  In general, at the boundary surface between the transmission / reception surface of the ultrasonic sensor and the sensor contact surface of the measuring tube, a part of the ultrasonic wave emitted from the ultrasonic sensor on the transmission side is reflected due to the difference in acoustic impedance, and this reflected wave is reflected. Are repeatedly reflected so as to reciprocate between a pair of ultrasonic sensors. This reflected wave becomes a noise component and may cause a measurement error.

On the other hand, according to the invention of claim 3 , since the concave portion and the convex portion are provided on the sensor contact surface, and only the convex portion is brought into close contact with the transmission / reception surface of the ultrasonic sensor, the ultrasonic sensor on the transmission side The wave height when the ultrasonic wave emitted from the receiver is directly received by the ultrasonic sensor on the reception side, and reflected at the boundary surface on the reception side, and further reflected on the boundary surface on the transmission side, and again on the ultrasonic sensor on the reception side It is possible to increase the ratio with the peak value when the reflected wave that has returned to is received. That is, the S / N ratio of the received wave can be increased, and measurement errors can be reduced.

[Invention of claim 4 ]
According to the invention of claim 4 , the transmission / reception surfaces of the pair of ultrasonic sensors are arranged so as to be non-parallel when the measurement tube is viewed from the axial direction, and reflected by the transmission / reception surfaces of one ultrasonic sensor. Since the ultrasonic wave propagation path is shifted from the other ultrasonic sensor, measurement errors caused by the reflected wave can be prevented. In addition, it is preferable that the angle which both transmission / reception surfaces make is 2-10 degrees.

[Invention of claim 5 ]
In general, when ultrasonic waves are emitted into the gas flowing inside the measurement tube through the wall of the measurement tube, the refraction angle of the ultrasonic wave at the interface between the wall of the measurement tube and the gas depends on Snell's law. Very small. Therefore, when a pair of ultrasonic sensors is arranged at a position where the reception intensity is the strongest, the pair of ultrasonic sensors are too close to each other in the axial direction of the measurement tube, so that the gas flow rate is measured. It was difficult to perform accurately.

On the other hand, according to the invention of claim 5 , one ultrasonic sensor receives the ultrasonic wave reception intensity of the ultrasonic wave receivable region that propagates radially from the other ultrasonic sensor side at a certain directivity angle. Is disposed on the side away from the other ultrasonic sensor with respect to the central portion of the region where the height is the highest. Thereby, although the reception intensity becomes weak, the distance between the pair of ultrasonic sensors can be increased in the axial direction of the measurement tube, so that the gas flow rate can be accurately measured.

[Invention of claim 6 ]
When the wall portion constituting the measuring tube is thin, as in the invention of claim 6, a pair of sensor mounting convex portions are projected from the outer surface of the measuring tube, and the core portion is depressed to form a sensor housing concave portion. do it.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the ultrasonic flowmeter 10 includes a measuring tube 20 made of a resin (specifically, hard vinyl chloride) molded article, and a fluid (liquid or gas) flows through both ends thereof. Connection is possible in the middle of a pipe (not shown). A pair of ultrasonic sensors 11, 11 are disposed on the upstream side and the downstream side of the measurement tube 20 with the fluid passage region R <b> 1 interposed therebetween, and between the ultrasonic sensors 11, 11, Ultrasonic waves are transmitted and received in a direction that obliquely crosses the direction of the axis J1.

  Here, since the wall portion constituting the measuring tube 20 is interposed between the ultrasonic sensors 11 and 11 and the fluid passage region R1, the ultrasonic waves transmitted and received between the ultrasonic sensors 11 and 11 are illustrated in FIG. As indicated by the dotted line 1, the light is refracted according to Snell's law at the boundary surface between the wall portion and the fluid passage region R1.

  Based on the difference or reciprocal difference between the propagation time of the ultrasonic wave in the forward direction along the flow of the fluid and the propagation time of the ultrasonic wave in the reverse direction against the flow, the flow rate of the fluid passing through the measurement tube 20 is Measurement is possible. In addition, since the calculation formula which calculates a flow volume based on the difference of propagation time or a reciprocal difference is well-known, description is abbreviate | omitted.

  4 shows a cross section (specifically, an XX cross section in FIG. 5) obtained by cutting the measurement tube 20 along a plane orthogonal to the direction of the axis J1. As shown in the figure, the measuring tube 20 has a cylindrical structure. Further, as shown in FIG. 1, in the fluid passage region R1 penetrating the inside of the measuring tube 20, the upstream inflow port 20A is tapered toward the downstream, and the downstream outflow port 20B is downstream. The inner diameter between the inlet 20A and the outlet 20B is constant.

  Flange walls 21 and 21 are provided at both ends of the measuring tube 20. The flange walls 21 and 21 project laterally over the entire circumference of the measuring tube 20. When the measuring pipe 20 is connected to a feed pipe (not shown), the flange walls 21 and 21 are brought into close contact with the connection surface of the feed pipe.

  As shown in FIGS. 4 to 6, a plurality of rib walls 24 and 25 are provided between the flange walls 21 and 21. That is, a plurality of rib walls 24 and 24 extending in the axis J1 direction of the measuring tube 20 and connecting the flange walls 21 and 21, and a rib wall 25 extending laterally from the intermediate portion of the measuring tube 20 and extending in the circumferential direction. And are provided. The rib walls 24, 24 reinforce the relatively thin flange walls 21, 21.

  As shown in FIG. 6, a fixing wall 22 for fixing the flow rate calculation indicator 18 (see FIG. 3) is provided between the flange walls 21 and 21. The fixing wall 22 has a diamond-shaped frame structure protruding from the outer surface of the measuring tube 20, and the inner side thereof has a wiring processing recess 26 opened to the side of the measuring tube 20 (the front side in FIG. 6). It has become. The wiring processing recess 26 is provided with a cross rib 23 erected from the outer surface of the measuring tube 20, and the cross rib 23 reinforces the fixing wall 22 by connecting two parallel sides of the fixing wall 22. Yes. Note that two sides of the fixing wall 22 parallel to the axis J1 direction of the measuring tube 20 also serve as part of the rib walls 24, 24, and one side of the cross rib 23 connecting the two sides is a rib wall. 25 extension lines are provided.

  A flow rate calculation indicator 18 (see FIG. 3) is detachably fixed to the opening end of the fixing wall 22, thereby closing the wiring processing recess 26. The flow rate calculation display 18 calculates and displays the flow rate based on the output signals from the ultrasonic sensors 11 and 11. A sealing groove 22A is formed at the opening end of the fixing wall 22, and a connecting portion between the flow rate calculation display 18 and the fixing wall 22 is sealed by a sealing member (not shown).

  As shown in FIG. 6, two positions 180 degrees apart in the circumferential direction at positions near both ends of the measuring tube 20 (specifically, two positions 90 degrees apart from the fixing wall 22 in opposite directions in the circumferential direction). The sensor mounting convex portions 30 are formed so as to protrude. These sensor mounting convex portions 30, 30 protrude in a direction (radial direction of the measurement tube 20) orthogonal to the axis J <b> 1 direction of the measurement tube 20. The distance between the sensor mounting convex portions 30 and 30 in the direction of the axis J1 is determined based on Snell's law from the material of the measuring tube 20 and the type of fluid.

  FIG. 5 shows a state in which the measurement tube 20 is viewed from the axial direction of the sensor mounting convex portion 30 (upward in FIG. 6). As shown in the figure, the outer surface of the sensor mounting convex portion 30 forms a cylindrical surface, and a plurality of screwing columns 40 bulge from the cylindrical surface. The screwing columns 40 are evenly arranged on the outer peripheral surface of the sensor mounting convex portion 30 and extend parallel to the sensor mounting convex portion 30 (in the direction orthogonal to the plane of FIG. 5). A screw hole 41 is formed in the core portion of the screw column 40 and is open to the front end surface. The front end surface of the screwing column 40 and the front end surface of the sensor mounting projection 30 are flush with each other and are lower than the rib walls 24 and 24.

  A sensor housing recess 31 for housing the ultrasonic sensor 11 is formed in the core of each sensor mounting projection 30, 30. As shown in FIG. 2, the sensor housing recess 31 is closed on the fluid passage region R <b> 1 side and opened toward the side of the measuring tube 20. In addition, the internal shape of the sensor accommodation recessed parts 31 and 31 is a shape which can open a shaping | molding die in a direction orthogonal to the axis | shaft J1 direction of the measurement pipe | tube 20 (it does not have an undercut).

  As shown in FIG. 1, the ultrasonic sensor 11 is accommodated in an inclined posture with respect to the axis J <b> 1 direction of the measuring tube 20 on the bottom side of the sensor accommodating recess 31, and the ultrasonic sensor 11 is overlapped with the cap on the opening side. 50 (corresponding to the “plug member” of the present invention) is inserted and fitted. A wave washer 59 (corresponding to the “elastic member” of the present invention) is sandwiched between the ultrasonic sensor 11 and the cap 50 in a compressed state. The wave transmitting / receiving surface 16 of the ultrasonic sensor 11 is pressed against the sensor contact surface 35 formed at the bottom of the sensor housing recess 31 by the elastic force of the wave washer 59. The ultrasonic sensor 11 and the sensor contact surface 35 are in close contact with each other via a grease or an adhesive (not shown).

  As shown in FIG. 2, the sensor housing recess 31 corresponds to an opening-side cap fitting portion 32 (“plug fitting portion” of the present invention) by a boundary step surface 34 orthogonal to the axial direction of the sensor mounting projection 30. ) And the sensor housing portion 33 on the bottom side. On the other hand, the cap 50 inserted and fitted into the sensor housing recess 31 protrudes laterally from the rear end of the plug body 51 and the opening of the sensor housing recess 31. It is comprised from the collar part 60 screwed to the edge (refer FIG. 7).

  The flange portion 60 has a disk shape and has substantially the same thickness as the height difference between the sensor mounting convex portion 30 and the rib walls 24 and 24. That is, when the cap 50 is inserted and fitted into the sensor housing recess 31, the flange 60 is flush with the rib walls 24 and 24. Further, four screw insertion holes 61 are formed through at positions separated from each other by 90 degrees in the circumferential direction of the collar portion 60 (only three are shown in FIG. 7A). By screwing four male screw members 62 (for example, tapping screws) penetrating through the screw insertion holes 61 into the screw holes 41 of the screw columns 40, the cap 50 holds the ultrasonic sensor 11 and accommodates the sensor. The recess 31 is fixed in a sealed state (see FIG. 1).

  A sensor contact surface 35 inclined at a predetermined angle (specifically, about 45 degrees) with respect to the axis J1 direction of the measuring tube 20 is provided at the bottom of the sensor housing portion 33 in the sensor housing recess 31. The housing portion 33 is depressed toward the sensor contact surface 35 as a whole (in a direction perpendicular to the sensor contact surface 35). The sensor contact surface 35 has a circular shape (see FIG. 5) having substantially the same diameter as the outer diameter of the ultrasonic sensor 11, and the sensor contact surfaces 35 and 35 are parallel to each other (see FIG. 5). 1). In other words, the transmission / reception surfaces 16 and 16 of the ultrasonic sensors 11 and 11 that are in close contact with the sensor contact surfaces 35 and 35 are parallel to each other. The inclination angle of the sensor contact surface 35 is determined based on Snell's law from the material of the measuring tube 20 and the type of fluid so that the pair of ultrasonic sensors 11 and 11 maintain an appropriate distance. .

  An inclined arc surface 36 extends from the edge of the sensor contact surface 35 in the sensor housing portion 33 toward the boundary step surface 34. The inclined arc surface 36 is perpendicular to the sensor contact surface 35 and extends inclined with respect to the direction of the axis J1 of the measuring tube 20. An intermediate step surface 37 </ b> A parallel to the sensor contact surface 35 is formed at an intermediate portion between the sensor contact surface 35 and the boundary step surface 34 in the inclined arc surface 36. The sensor contact surface 35 side of the intermediate step surface 37A is a small-diameter circular surface 36B having the same diameter as the sensor contact surface 35. The ultrasonic sensor 11 is received and positioned in a recess formed by the small-diameter arc surface 36B and the sensor contact surface 35 (see FIG. 1).

  Here, the portion of the sensor contact surface 35 opposite to the small-diameter circular arc surface 36B in the radial direction is an upright surface 37B orthogonal to the axis J1 direction of the measuring tube 20 from the edge of the sensor contact surface 35. As a result, as shown in FIG. 5, the entire surface of the sensor contact surface 35 faces the opening of the sensor housing recess 31 in a direction orthogonal to the axis J1 direction of the measuring tube 20, and the sensor contact surface is directly above the sensor housing recess 31. The ultrasonic sensor 11 can be inserted toward the surface 31.

  On the other hand, in the inclined arc surface 36, the boundary step surface 34 side of the intermediate step surface 37A is a large-diameter arc surface 36C having a larger diameter than the small-diameter arc surface 36B. In the large-diameter circular arc surface 36 </ b> C, a concave recess 38 is formed. One opening of the internal electric wire passage 39 (see FIG. 4) is formed in the inner part of the routing recess 38. The internal electric wire passage 39 extends through the wall portion constituting the measuring tube 20 to the inside of the wiring processing concave portion 26 (fixing surrounding wall 22). The lead wire 17 (corresponding to the “connection wire” of the present invention) extending from the ultrasonic sensor 11 is passed from the routing recess 38 to the internal electric wire passage 39, and the flow rate is calculated inside the wiring processing recess 26. It is connected to the processor 18 (see FIG. 3).

  The tip bulging portion 55 formed on the plug body 51 of the cap 50 is received in the rear surface side region of the ultrasonic sensor 11 in the sensor housing portion 33 described above. A sensor pressing surface 56 facing the rear surface of the ultrasonic sensor 11 is formed on the tip bulging portion 55.

  The sensor pressing surface 56 is a surface parallel to the sensor contact surface 35. That is, it is a plane inclined by a predetermined angle (specifically, about 45 degrees) with respect to the direction of the axis J1 of the measuring tube 20. The sensor pressing surface 56 has a circular shape with the same diameter as the rear surface of the ultrasonic sensor 11. A wave washer 59 is compressed between the sensor pressing surface 56 and the ultrasonic sensor 11 (see FIGS. 1 and 2).

  An escape groove 57 is formed in the sensor pressing surface 56 so as to be recessed radially outward from the center (see FIG. 7). The escape groove 57 forms a gap with the rear surface of the ultrasonic sensor 11, communicates between the rear surface of the ultrasonic sensor 11 and the routing recess 38, and extends from the ultrasonic sensor 11. 17 can be led out to the recess 38.

  As shown in FIG. 2, the cap fitting portion 32 of the sensor housing recess 31 has its central axis J2 oriented in a direction perpendicular to the direction of the axis J1 of the measuring tube 20. Specifically, the cap fitting portion 23 has a flat cylindrical fitting inner surface 32A whose depth dimension is small with respect to the diameter, and the fitting inner surface 32A is orthogonal to the axis J1 direction of the measuring tube 20. Standing up in the direction.

  A proximal end fitting portion 52 provided in the cap body 51 of the cap 50 is fitted to the fitting inner surface 32 </ b> A of the cap fitting portion 32. The base end fitting portion 52 has a flat cylindrical shape corresponding to the internal space of the cap fitting portion 32. The outer peripheral surface of the base end fitting portion 52 is fitted in a state in which it is in contact with the fitting inner surface 32A of the cap fitting portion 32 over the entire circumference. Further, an O-ring groove 53 is formed on the outer peripheral surface of the base end fitting portion 52, and the O-ring 54 is crushed and in close contact with the fitting inner surface 32 </ b> A of the cap fitting portion 32. Thereby, the opening of the sensor accommodating recess 31 is sealed in an airtight state.

  In addition, the intersection 52B of the distal end surface 52A of the proximal end fitting portion 52 with the sensor pressing surface 56 is depressed in an arc shape toward the inclination direction of the sensor pressing surface 56 (see FIG. 7C). The part which protruded to the cap fitting part 32 among the ultrasonic sensors 11 is received here (refer FIG. 1).

  The configuration of the ultrasonic flowmeter 10 of the present embodiment is as described above. Next, a method for manufacturing the ultrasonic flowmeter 10 will be described. First, the optimum ultrasonic sensors 11 and 11 are paired based on the characteristic values (impedance, capacitance, etc.) of the ultrasonic sensor 11.

  Next, the paired ultrasonic sensors 11 and 11 are inserted into the sensor housing concave portions 31 and 31 of the sensor mounting convex portions 30 and 30 from the direction orthogonal to the axis J1 direction of the measuring tube 20. At that time, the lead wire 17 of the ultrasonic sensor 11 is passed through the wave washer 59 in advance, and the lead wire 17 is routed and inserted into the internal wire passage 39 from the recess 38, and the inside of the wiring processing recess 26. Derived in In this state, the ultrasonic sensor 11 is positioned by the small-diameter arc surface 36 </ b> B provided at the bottom of the sensor housing recess 31 and the sensor contact surface 35.

  Next, with the wave washer 59 placed on the rear surface of the ultrasonic sensor 11, the cap 50 is inserted into the sensor housing recess 31 from a direction orthogonal to the axis J <b> 1 direction of the measuring tube 20. Then, the sensor pressing surface 56 of the cap 50 faces the rear surface of the ultrasonic sensor 11 with the wave washer 59 interposed therebetween.

  Next, the cap 50 is pushed into the sensor housing recess 31 and screwed. That is, the male screw member 62 is passed through each screw insertion hole 61 of the flange portion 60 and screwed into the screwing hole 41 of the screwing column 40. Then, the wave washer 59 is compressed between the cap 50 (specifically, the sensor pressing surface 56) and the rear surface of the ultrasonic sensor 11, and the wave receiving / transmitting surface 16 of the ultrasonic sensor 11 is sensor-contacted surface 35 due to its elastic force. It is fixed in a state of being pressed against and in close contact with.

  When the pair of ultrasonic sensors 11 and 11 and the caps 50 and 50 are attached as described above, the lead wires 17 and 17 led out from the respective sensor housing recesses 31 and 31 into the wiring processing recess 26 are displayed as a flow rate calculation. The flow rate calculation indicator 18 is fixed to the fixing wall 22 by connecting to an electric circuit (not shown) provided in the vessel 18. Thereby, the wiring process recessed part 26 is obstruct | occluded and the ultrasonic flowmeter 10 is completed.

  Thus, according to the present embodiment, the center axis J2 of the cap fitting portion 32 that is a fitting portion with the cap 50 in the sensor receiving recess 31 is set in a direction perpendicular to the direction of the axis J1 of the measuring tube 20. Therefore, the total length of the measuring tube 20 can be shortened compared to the conventional one in which the plug fitting portion is inclined with respect to the axial direction of the measuring tube.

  Further, the cap main body 51 (specifically, the proximal end fitting portion 52) of the cap 50 is fitted in a state of being in contact with the fitting inner surface 32A of the cap fitting portion 32. The component of the force perpendicular to the axial direction of the plug main body 51 among the elastic force applied to the cap 50 can be received by the contact between the fitting inner surface 32 </ b> A of the cap fitting portion 32 and the cap 50. Therefore, the strength required for the flange 60 and the male screw member 62 that are screwed portions between the flange 60 and the opening edge of the sensor housing recess 31 can be suppressed.

  Further, the lead wire 17 connecting the ultrasonic sensors 11, 11 and the flow rate calculation display 18 penetrates the wall portion of the measuring tube 20 between the sensor housing recess 31 and the wiring processing recess 26 to store the sensor. Since the inner wire passage 39 that connects the inside of the recess 31 and the inside of the wiring processing recess 26 is passed, the disconnection of the lead wire 17 can be prevented.

[Other Embodiments]
The present invention is not limited to the above-described embodiment. For example, the embodiments described below are also included in the technical scope of the present invention, and various other than the following can be made without departing from the scope of the invention. It can be changed and implemented.

  (1) The pair of ultrasonic sensors 11 and 11 may not be arranged with the fluid passage region R1 interposed therebetween as in the above-described embodiment. For example, as shown in FIG. Further, it may be arranged in parallel with the axis J1 direction of the measurement tube 20 on the downstream side so that the ultrasonic wave is reflected by the inner surface of the measurement tube 20 one or more times and transmitted and received.

  (2) A plurality of pairs of ultrasonic sensors 11 and 11 may be provided to transmit and receive ultrasonic waves through a plurality of survey lines (ultrasonic propagation paths). For example, two survey lines may be arranged in the same plane so as to intersect, two survey lines may be arranged in two planes intersecting at right angles, or a plurality of survey lines may be arranged in parallel planes.

  (3) The ultrasonic sensor 11 has, for example, a structure in which a filler 14 is filled around the ultrasonic vibrator 13 in a state where the ultrasonic vibrator 13 is housed in a metal case 12 as shown in FIG. When the bottom surface of the metal case 12 is the wave transmitting / receiving surface 16, the following phenomenon may occur. That is, due to the difference in acoustic impedance between the metal case 12 constituting the wave transmitting / receiving surface 16 and the resin constituting the sensor contact surface 35, a part of the ultrasonic waves emitted from the ultrasonic sensor 11 on the transmission side is 16 and the sensor contact surface 35, and the reflected wave is repeatedly reflected so as to reciprocate between the pair of ultrasonic sensors 11 and 11. When the sensor contact surface 35 is in surface contact with the entire surface of the transmission / reception surface 16, the reflected wave reciprocating between the pair of ultrasonic sensors 11 and 11 is relatively difficult to attenuate.

  On the other hand, if the sensor contact surface 35 is provided with a concave portion and a convex portion 35A and only the convex portion 35A is partially brought into close contact with the wave transmitting / receiving surface 16, the boundary surface for reflecting the ultrasonic wave becomes small. Sound waves are gradually attenuated each time they are reflected at the interface. Specifically, for example, the ultrasonic wave emitted from the ultrasonic sensor 11 on the transmission side is directly reflected by the ultrasonic sensor 11 on the reception side and reflected on the boundary surface on the reception side, and further transmitted. It is possible to increase the ratio with the peak value when the reflected wave that has been reflected at the boundary surface on the side and returned to the ultrasonic sensor 11 on the receiving side is received again. That is, the S / N ratio of the received wave can be increased, and the measurement error can be reduced.

  Here, as the shape of the convex portion 35A capable of producing the above-described effect, a circular shape (see FIG. 10 (A)) or an annular shape (see FIG. 10 (D)) that is in close contact with only the central portion of the transmission / reception surface 16; Further, a linear shape (see FIG. 10C) or a cross shape (see FIG. 10C) extending in the radial direction of the transmission / reception surface 16 may be mentioned.

  (4) In the above embodiment, the transmission / reception surfaces 16 and 16 of the ultrasonic sensors 11 and 11 are planes parallel to each other. However, as shown in FIG. 11, at the same angle θ1 with respect to the axis J1 direction of the measurement tube 20. While being inclined, they are made to be non-parallel to each other when viewed from the axis J1 direction of the measuring tube 20, and the propagation path of the ultrasonic waves reflected by the wave transmitting / receiving surface 16 of one ultrasonic sensor 11 is from the other ultrasonic sensor 11. It may be shifted. Specifically, the angle θ2 formed by both the wave transmitting / receiving surfaces 16 and 16 may be set to 2 to 10 degrees. According to this embodiment, it is possible to prevent measurement errors caused by reflected waves.

(5) Although not shown, the transmission / reception surfaces 16 and 16 of the pair of ultrasonic sensors 11 and 11 are arranged so as to be non-parallel when the measurement tube 20 is viewed from a direction orthogonal to the axis J1 direction. Thus, even if the propagation path of the ultrasonic wave reflected by the transmitting / receiving surface 16 of one ultrasonic sensor 11 is shifted from the other ultrasonic sensor 11, measurement errors due to the reflected wave can be prevented.

  (5) Generally, when the fluid to be measured is a gas, the refraction angle of the ultrasonic wave at the boundary surface between the wall portion of the measurement tube 20 and the fluid passage region R1 (the angle with respect to a straight line orthogonal to the axis J1 of the measurement tube 20). ) Is very small due to Snell's law. For example, the refraction angle when entering from the measurement tube 20 made of hard vinyl chloride (sound speed 2270 m / s) into the air (sound speed 340 m / s) at an incident angle of 45 degrees is about 6 degrees. Therefore, when the pair of ultrasonic sensors 11 and 11 are arranged at positions where the reception intensity is the strongest, the ultrasonic sensors 11 and 11 are too close to each other in the axis J1 direction of the measurement tube 20. It was difficult to accurately measure the gas flow rate.

  Therefore, when measuring the gas flow rate, the ultrasonic sensors 11, 11 may be arranged as follows. That is, as shown in FIG. 12, the ultrasonic sensor 11 on the receiving side has an ultrasonic wave reception area Z1 that propagates radially from the ultrasonic sensor 11 side on the transmitting side at a certain directivity angle. What is necessary is just to arrange | position on the side away from the ultrasonic sensor 11 by the side of a transmission with respect to the area | region center part Z2 where the receiving intensity of a sound wave becomes the highest. In this way, although the reception intensity is weakened, the distance between the pair of ultrasonic sensors 11, 11 can be increased in the direction of the axis J1 of the measurement tube 20, so that the gas flow rate can be accurately measured. Is possible.

  (6) In the above embodiment, since the wall portion constituting the measuring tube 20 is relatively thin, the sensor housing recessed portions 31 are formed in the core portions of the sensor mounting protruding portions 30 that protrude from the outer surface of the measuring tube 20. However, when the wall part which comprises the measurement pipe | tube 20 is thick enough, it is not necessary to provide the sensor attachment convex parts 30 and 30. FIG.

  (7) Instead of the wave washer 59, a disc spring or a rubber ring may be used.

  (8) The entire cap 50 may be formed of an elastic member, and may be in close contact with the fitting inner surface 32 </ b> A of the sensor housing recess 31 by being fitted inside the sensor housing recess 31 while being elastically deformed.

Sectional drawing of the ultrasonic flowmeter which concerns on one Embodiment of this invention. Sectional view of sensor housing recess Front view of measuring tube XX sectional view in FIG. Side view of measuring tube Side view of measuring tube (A) perspective view, (B) side view, (C) cross-sectional view of the cap Conceptual diagram showing the arrangement of ultrasonic sensors according to a modified example Sectional drawing of the ultrasonic sensor which concerns on a modification The conceptual diagram which shows the contact state of the sensor contact surface and transmission / reception surface which concern on a modification Conceptual diagram showing the arrangement of ultrasonic sensors according to a modified example Sectional drawing of the ultrasonic flowmeter which concerns on a modification Cross-sectional view of a measuring tube equipped with a conventional ultrasonic flowmeter

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Ultrasonic flowmeter 11, 11 Ultrasonic sensor 12 Metal case 13 Ultrasonic vibrator 16 Transmission / reception surface 17 Lead wire (connection line)
18 Display 20 Measuring tube 22 Fixing wall 26 Wiring processing recess 30, 30 Sensor mounting convex 31, 31 Sensor housing recess 32 Cap fitting 32A Fitting inner surface 35, 35 Sensor contact surface 39 Wiring insertion path 50, 50 Cap (plug member)
51 Cap plug (plug body)
56 Sensor holding surface 59 Wave washer (elastic member)
60 Cap collar (buttock)
62 Male thread member J1 Measuring tube axis

Claims (6)

Between a pair of ultrasonic sensors attached to the upstream side and the downstream side of the measurement pipe through which the fluid flows, ultrasonic waves are transmitted and received in a direction obliquely intersecting the axial direction of the measurement pipe to thereby control the flow rate of the fluid. An ultrasonic flow meter for measuring,
A pair of sensor receiving recesses that are recessed in the outer surface of the measuring tube to store the pair of ultrasonic sensors, and provided at the bottom of each sensor receiving recess and inclined with respect to the axial direction of the measuring tube And a sensor abutting surface to which the transmitting and receiving surfaces of the ultrasonic sensors are in close contact, and a plug member that is fitted and fixed to the plug fitting portion of the sensor receiving recesses to seal the sensor receiving recess. In things,
The plug member can be fitted into the plug fitting portion from a direction orthogonal to the axial direction of the measuring tube,
In the plug member, a plug main body fitted in a state of being in contact with the inner side surface of the plug fitting portion, a sensor pressing surface formed at the tip of the plug main body and substantially parallel to the sensor contact surface, A flange that protrudes laterally from the rear end of the plug body and is screwed to the opening edge of the sensor receiving recess;
Between the sensor pressing surface and the ultrasonic sensor, there is provided an elastic member that is compressed and presses the ultrasonic sensor against the sensor contact surface by its elastic force,
A component of the force perpendicular to the fitting direction of the plug member among the elastic force applied from the elastic member to the plug member is received by the contact between the inner surface of the plug fitting portion and the plug member. An ultrasonic flowmeter characterized by that. A flow rate calculation display for calculating and displaying the flow rate based on an output signal of the ultrasonic sensor;
A fixing wall for protruding from the outer surface of the measuring tube and fixing the flow rate calculation indicator at the tip,
A wiring processing recess formed inside the fixed wall and closed by the flow rate display;
An internal electric wire passage that passes through a wall portion between the wiring processing recess and the sensor housing recess in the measurement tube and through which a connection line between the ultrasonic sensor and the flow rate calculation indicator is passed. The ultrasonic flowmeter according to claim 1. The ultrasonic flowmeter according to claim 1, wherein a concave portion and a convex portion are provided on the sensor contact surface, and only the convex portion is partially brought into close contact with a wave transmitting / receiving surface of the ultrasonic sensor. . The transmission / reception surfaces of the pair of ultrasonic sensors are arranged so as to be non-parallel when the measurement tube is viewed from the axial direction, and the propagation path of the ultrasonic waves reflected by the transmission / reception surfaces of one of the ultrasonic sensors The ultrasonic flowmeter according to claim 1, wherein the ultrasonic flowmeter is shifted from the other ultrasonic sensor. The fluid is a gas;
One of the ultrasonic sensors is located in the center of the region where the ultrasonic wave reception intensity is highest among the ultrasonic wave receivable regions propagated radially from the other ultrasonic sensor side at a certain directivity angle. The ultrasonic flowmeter according to claim 1, wherein the ultrasonic flowmeter is disposed on a side away from the other ultrasonic sensor. 6. A sensor mounting convex portion that protrudes from an outer surface of the measuring tube is provided, and the sensor receiving concave portion is formed by recessing a core portion of the sensor mounting convex portion. The ultrasonic flowmeter described in 1.

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