JP2005249562A - Vortex flowmeter and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily press-in without depending on the experience of a worker and eliminate deformation of a spring plate in pressing-in without shift of the center. <P>SOLUTION: The elastic base metal constituting a part of vortex signal detector of this invention has a spring plate pressed in a spring plate press-in part formed in the upper end press-in part to be pressed-in the upper opening side of a vibration tube and a hollow tip end side of the vibration tube. The vibration tube is provided with a spring plate guide part formed with slightly larger inner diameter than the inner diameter of the spring plate press-in part, in the hollow part inside the vibration tube at the end of the spring plate press-in part corresponding to the inlet position where the spring plate is pressed in the spring plate press-in part. By providing a taper part continuing to the upper end press-in part of the elastic base metal, the taper part is attached before the upper end press-in part of the elastic base metal with larger outer diameter than the corresponding vibration tube inner diameter touches when inserting the elastic base metal. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a vortex flowmeter in which an elastic base material constituting a part of a vortex signal detection unit is press-fitted into a cavity of a vibrating tube at two locations above and below an upper end press-fitting portion and a spring plate press-fitting portion, and a method for manufacturing the same.

  As is well known, the vortex flowmeter is a speculative flow rate that utilizes the fact that the number of Karman vortices generated per unit time from a vortex generator disposed in a flow tube is proportional to the flow velocity within a predetermined Reynolds number range. It is a total.

  A conventional vortex flowmeter will be described with reference to FIG. 7 (see Patent Document 1). The sensor (vortex signal detector) is a part that is press-fitted into the cavity of the vibrating tube, faithfully receives the pressure fluctuation caused by the Karman vortex received by the vibrating tube, converts it into an electrical signal, and outputs it to detect stress and strain. And an elastic base material having a detection element (piezoelectric element) attached thereto.

  When a fluid flows in the flow path and a Karman vortex is alternately generated on the left and right sides of the pressure receiving plate by a vortex generator (not shown) provided in the flow path of the vortex flowmeter body, a fluctuating pressure is generated and the pressure receiving plate is vibrated left and right. . Therefore, the movable tube portion of the vibration tube vibrates with the vibration tube mounting flange as a fulcrum, and this vibration is transmitted to the elastic base material via the spring plate. The elastic base material is pressed into and fixed to the vibrating tube at the upper end, so that it vibrates left and right in a cantilevered manner with the upper end as a fulcrum, generating alternating stress on the piezoelectric element plate and outputting an electrical signal corresponding to the vortex To do.

  As described above, the movable tube portion of the vibration tube vibrates using the vibration tube mounting flange as a fulcrum, and a spring plate is used to transmit this vibration to the elastic base material. The spring plate is a disc-shaped spring portion having radial slits or notches, and the outer diameter is slightly larger than the inner diameter of the locking hole. The spring plate is welded at the center to the tip of the spring plate mounting portion of the elastic base material. It is fixed. The elastic base material to which the spring plate is fixed is press-fitted and fixed in the cavity inside the vibration tube.

  In the conventional press-fitting and fixing of the elastic base material, the elastic base material is manually pushed into the spring plate fixing part of the vibration tube, and the vibration tube and the elastic base material come into contact with each other at the position where it is slightly pushed in the axial direction. I was doing. After that, a bar jig was inserted into the hollow hole of the elastic base material, and press-fitted to serve as centering.

  However, in this method, the operator may press-fit without noticing the deformation of the spring plate, and it is not known until the output is confirmed whether or not the spring plate is deformed. Moreover, since it press-fits using the hollow hole of an elastic base material, there existed a problem that a hollow hole diameter deform | transforms at the time of press-fit, and a jig becomes difficult to come off.

Further, the deformation of the spring plate causes the level of the vortex signal to be reduced or biased even at the same flow rate, and in the worst case, it is processed as a defective product, leading to an increase in cost.
JP 7-294298 A Japanese Patent No. 3153748

  SUMMARY OF THE INVENTION An object of the present invention is to solve such problems and to easily press-fit without depending on the experience of an operator, to prevent misalignment, and to eliminate deformation of a spring plate during press-fitting.

  Another object of the present invention is to reliably detect vibrations in the vortex pressure and stabilize the vortex signal transmitted to the transducer, thereby reducing the defect rate and reducing the cost.

  The vortex flowmeter of the present invention includes a vibrating tube having a cylindrical body that is open at one end, and a pressure receiving plate is attached to the end of the vibrating tube so as to be able to receive the vortex fluctuation pressure generated by the vortex generator. And a vortex signal detection unit including an elastic base material press-fitted into the cavity inside the vibration tube. The vortex signal detector detects the vibration of the pressure receiving plate and transmits it to the outside as an electric signal, and the elastic base material is inserted into the upper end press-fitting portion that is press-fitted into the upper opening side of the vibration tube and the cavity tip end side. A spring plate is press-fitted into the formed spring plate press-fitting portion. The vibration tube is a spring plate guide formed at an end of the spring plate press-fit portion corresponding to an inlet position when the spring plate is press-fitted into the spring plate press-fit portion, and having an inner diameter slightly larger than the inner diameter of the spring plate press-fit portion. The portion is provided in the cavity inside the vibrating tube. A tapered portion is provided following the upper end press-fit portion of the elastic base material, and when inserting the elastic base material, the taper portion is inserted before the upper end press-fit portion of the elastic base material having an outer diameter larger than the corresponding inner diameter of the vibration tube comes into contact. It is comprised so that it may contact | abut.

  The manufacturing method of the vortex flowmeter according to the present invention is such that the elastic base material is attached to the vibration tube by both guide portions provided immediately before the upper end press-fitting portion and the spring plate press-fitting portion where the elastic base material is press-fitted into the vibration tube. Then, the press-fitting jig is applied to the horizontal upper surface of the elastic base material, and the press-fitting is completed by pushing it in with the press-fitting machine until it is flush with the upper surface of the vibrating tube.

  According to the present invention, it is possible to press-fit the elastic base material without deforming the spring plate by providing the spring plate guide portion on the vibration tube. Further, since the elastic base material is provided with the tapered portion, it can be centered at the upper and lower two points in cooperation with the spring plate guide portion without depending on the experience of the operator.

  Furthermore, according to the present invention, the deformation of the spring plate is minimized, and the level of the vortex signal is stabilized. In addition, since the signal level is stabilized, the defect rate is reduced and the cost is reduced.

  The press-fitting of the elastic base material does not require the use of a hollow hole inside the elastic base material, and it is possible to press-fit using the upper end surface of the elastic base material that is centered and positioned. Workability is improved.

  Hereinafter, the present invention will be described based on examples. The present invention has a feature in the mounting structure of the elastic base material that constitutes a part of the sensor to the vibration tube. However, before explaining this feature of the present invention, the present invention is applied below. An example of the overall configuration of the vortex flowmeter that can be produced will be described with reference to FIGS. FIG. 1 is a diagram illustrating the overall configuration of a vortex flow meter, where (a) shows a vortex flow meter main body viewed from the upstream side of a flowing fluid, and (b) shows a vortex flow rate in a partial cross section. The overall structure of the total is shown. FIG. 2 is an enlarged cross-sectional view of the main body.

  The illustrated vortex flowmeter includes a main body, a vibration tube attached to the main body, a sensor (vortex signal detector) attached to the vibration tube, a converter, and the converter attached to the main body. It is comprised from the attachment cylinder for. The main body portion includes a cylindrical flow tube portion (flow path) through which a fluid to be measured flows, and a vortex generator having both ends (upper and lower in the figure) fixed thereto is attached in the flow tube portion. On the downstream side of the vortex generator, a pressure receiving plate of the vibration tube projects into the flow tube portion. Here, although the vortex generator and the pressure receiving plate are illustrated as separate components, this pressure receiving plate is combined with the vortex generator so as to protrude into the measurement chamber formed inside the vortex generator. It is also possible to configure (see Patent Document 2). The converter calculates a circuit based on the sensor signal and converts it into a flow rate value, a display for displaying the calculated flow rate value, and for transmitting the flow rate value to a host computer or a downstream device. A transmission circuit, a power supply circuit, and the like are provided.

  The vibrating tube is configured as a cylindrical body having an open end (in the present specification, this is referred to as an “upper end”), and includes a movable tube portion having a bottomed cavity inside the tubular body. A pressure receiving plate is provided on the bottom end side. The vibration tube includes a vibration tube mounting flange disposed on the outer periphery on one end side, and is cantilevered by fixing it to the mounting surface of the vortex flowmeter main body with a mounting bolt. At that time, the vibration tube is liquid-tightly supported with respect to the main body using a gasket.

  Furthermore, a sensor (vortex signal detection unit) that detects vibration and transmits it as an electrical signal is inserted into the cavity inside the vibration tube. The sensor is a part that faithfully receives pressure fluctuations caused by Karman vortices received by the vibrating tube, converts it into an electrical signal, and outputs it. It has an elastic base material with a detection element (piezoelectric element) that detects stress and strain. doing.

  The element cover is a cylindrical body that seals the detection element portion, and is attached to the upper end surface of the vibration tube. Further, the upper end portion of the element cover is connected to the outer periphery of the sheath pipe that inserts the lead wire in an airtight manner. Two lead wires are inserted into the sheath pipe and led out toward the converter.

  In FIG. 2, when a fluid flows in the flow path and Karman vortices are alternately generated on the left and right sides (in the direction perpendicular to the paper surface), fluctuating pressure is generated, causing the pressure plate to vibrate left and right. Therefore, the movable tube portion of the vibration tube vibrates with the vibration tube mounting flange as a fulcrum, and this vibration is transmitted to the elastic base material via the spring plate. The elastic base material shown in the figure is pressed into and fixed to the vibrating tube at the upper end, so that it vibrates left and right in a cantilevered manner with the upper end as a fulcrum, generating alternating stress on the piezoelectric element plate, and an electrical signal corresponding to the vortex Is output.

  FIG. 3 is an enlarged view of an elastic base material (a) constituting a part of the sensor, a vibration tube (b) in which the elastic base material is press-fitted and fixed, and a spring plate fixed to the tip of the elastic base material ( c) respectively.

  The elastic base material is a columnar body that is press-fitted into the cavity in the vibration tube and faithfully transmits the displacement of the vibration tube that is alternately displaced by receiving the vortex fluctuation differential pressure acting on the vibration tube. The elastic base material is composed of a small-diameter portion to which a spring plate is attached at the tip, a large-diameter portion on the opposite side (upper end side), and an intermediate-diameter portion located in the middle, and the uppermost end portion of this large-diameter portion And an upper end press-fitting portion on the elastic base material side that is press-fitted to the upper end opening side of the vibration tube, and a taper portion following the upper end press-fitting portion. This taper part is comprised so that a diameter may be continuously enlarged from a large diameter part to an upper end press-fit part. In the elastic base material, the inside of the large diameter part and the medium diameter part is configured as a hollow hole in order to facilitate vibration.

  As can be seen from the upper side view shown on the left side of FIG. 3A, the upper end side large-diameter portion of the vibration tube is formed with two chamfers, and vibration detection elements such as piezoelectrics are formed on each surface. The element is affixed. The piezoelectric element is polarized in the thickness direction, and an electrode plate made of a porous plate is attached to the non-attached surface. The piezoelectric element constitutes a parallel type bimorph having an elastic base material as one output end and the electrode plates on both sides connected to the other output end.

  The outer diameter of the small-diameter portion located at the bottom end of the elastic base material is reduced to the outer diameter, or is cut into a taper shape toward the lower end surface, and a spring plate is attached to the tip by spot welding or screwing. Or after fixing using welding members, such as a rivet, this welding member is fixed by carrying out spot welding. Since the outer diameter of the medium diameter portion and the large diameter portion of the elastic base material is slightly smaller than the inner diameter of the vibration tube, it is not in contact with the vibration tube. This elastic base material is press-fitted and fixed only at the two positions of the upper end press-fitting portion and the spring plate position.

  The spring plate is for transmitting the vibration to the elastic base material when the movable tube portion of the vibration tube vibrates with the vibration tube mounting flange as a fulcrum. As shown in the enlarged view of FIG. 3 (c), the spring plate has a disk shape whose outer diameter is slightly larger than the inner diameter of the spring plate press-fitting portion of the vibration tube, and has a plurality of radial slits or cuts. A notch is bored to form a plurality of support pieces (each part divided by a slit or the like). The spring plate has a spring action that allows the elastic base material to be displaced in the axial direction. When the spring plate is press-fitted into the spring plate press-fitting portion at the bottom of the vibration tube, it is easily inserted by bending in the approach direction, and the vibration displacement of the vibration tube can be faithfully transmitted to the elastic base material.

  As described above, the vibrating tube shown in FIG. 3B has a movable tube portion having a bottomed cavity portion, a pressure receiving plate provided on the bottom end side of the movable tube portion, and a mounting surface of the vortex flow meter main body portion. And a vibration tube mounting flange disposed on the outer periphery on one end side. A hollow cavity portion is formed inside the movable tube portion so that the elastic base material is press-fitted and fixed, and a small-diameter spring plate press-fit portion for locking the spring plate is provided at the bottom of the cavity portion. Yes. The vibration tube cavity has an inner diameter slightly larger than that corresponding to the medium diameter portion and the large diameter portion of the elastic base material, and when the elastic base material is press-fitted into the vibration tube, the spring plate Except for the position and the base material side upper end press-fitting portion, it is configured to be in non-contact with the vibrating tube.

  Further, a spring plate guide portion is provided at the upper end of the spring plate press-fitting portion of the vibration tube into which the spring plate is press-fitted. The spring plate guide portion is formed to have an inner diameter slightly larger than the inner diameter of the spring plate press-fitting portion at the end of the spring plate press-fit portion corresponding to the inlet immediately before the spring plate is press-fitted. For example, with respect to a spring plate having a thickness of 0.2 mm and an outer diameter of 4.075 mm, the inner diameter of the spring plate press-fit portion is 4.0 mm, and the inner diameter of the spring plate guide portion is 4.1 mm.

  Next, the press-fitting and fixing of the elastic base material to the vibration tube will be described. Since the inner diameter of the spring plate press-fitting portion into which the spring plate is press-fitted is slightly smaller than the outer diameter of the spring plate, it is difficult to center and position the spring plate. However, as described above, the exemplified vibration pipe is provided with a spring plate guide portion having a diameter slightly larger than the inner diameter of the spring plate press-fitting portion. By setting the inner diameter of the guide portion to the same diameter as the outer diameter of the spring plate, or preferably slightly larger than that, the elastic base material can be positioned without applying a load to the spring plate at the tip side.

  On the other hand, since the elastic base material is provided with a tapered portion following the upper end press-fitting portion on the upper end press-fitting side opposite to the spring plate position, when inserting the elastic base material, the corresponding inner diameter of the movable tube portion The taper portion comes into contact before the base material side upper end press-fit portion having a larger outer diameter comes into contact. As a result, positioning can be performed on the upper end side of the elastic base material without causing misalignment. In other words, the tapered portion forms a guide portion at a position immediately before press-fitting on the upper end side of the elastic base material.

  In this way, with the elastic base material being easily centered and positioned by the two upper and lower guide portions on both the front end side and the upper end side, the press-fitting jig is applied to the horizontal surface of the upper surface of the elastic base material. Then, press-fitting is completed by pushing in until it is flush with the upper surface of the vibrating tube.

  FIG. 4 is a view for explaining the state of the spring plate after press-fitting according to the present invention. (A)-(c) has each shown sectional drawing (left side) of the elastic base material, and the figure (right side) of the spring board seen from the front end side. As shown in FIG. 4A, although the spring plate is fixed to the tip of the elastic base material, the spring plate is naturally not deformed before the press-fitting. FIG. 4B is a view showing a state after press-fitting according to the present invention, and shows normal press-fitting. According to this, the outer peripheral side of all the support pieces of the spring plate after press-fitting is evenly curved. FIG. 4 (c) shows, for comparison, a bad state that is caused by the prior art and becomes defective. According to this, the support piece is unevenly curved.

  5 and 6 are diagrams for explaining the axial positional relationship between the spring plate guide portion and the tapered portion, respectively, showing a state at the start of press-fitting (left side view) and a state after completion of press-fitting (right side view). ing. FIG. 5 illustrates a case where an elastic base material having a maximum axial length that may be generated due to manufacturing dimensional tolerances is press-fitted into a vibration tube having a minimum axial length, and FIG. The case where the elastic base material with the minimum length is press-fitted into the vibration tube with the maximum length is illustrated. As described above, according to the present invention, the axial position is determined so that the spring plate guide portion provided in the vibration tube on the distal end side of the elastic base material and the taper portion on the upper end side of the elastic base material function together. I have to keep it.

  First, it is desirable to position the spring plate so that it is at the inlet end of the spring plate guide portion when the tapered portion contacts the vibrating tube. Second, when the press-fitting portion of the elastic base material is in contact with the vibration tube following the taper portion, the spring plate is positioned so as to have already entered the spring plate guide portion, and the length and angle of the taper portion. Is set.

  5 and 6, it is assumed that the axial length of the guide portion is set to 0.6 mm. In FIG. 5, the guide portion enters 0.49 mm and is at a position of 0.11 mm to the boundary of the press-fit portion. Similarly, in FIG. 6, the guide portion enters 0.18 mm and is located at a position of 0.42 mm to the boundary of the press-fit portion. Thus, in either case shown in FIG. 5 and FIG. 6, when the elastic base material is inserted, the upper end surface of the vibration pipe passes through the upper end surface of the vibration base material, and the upper end press-fit portion of the elastic base material is When the upper end surface is reached, that is, when press-fitting is started, it indicates that the spring plate must have entered the inside of the guide portion.

It is a figure which illustrates the whole structure of a vortex flowmeter, (a) shows the vortex flowmeter main-body part seen from the upstream of the flowing fluid, and (b) is the whole structure of a vortex flowmeter in a partial cross section. Is shown. It is sectional drawing which expands and shows the main-body part shown in FIG. An enlarged view (c) of an elastic base material (a) constituting a part of the sensor, a vibration pipe (b) to which the elastic base material is press-fitted and fixed, and a spring plate fixed to the tip of the elastic base material, respectively. It is a figure illustrated. It is a figure explaining the state of the spring board after press-fitting by this invention. It is a figure explaining the axial direction positional relationship of a spring-plate guide part and a taper part, and has illustrated the case where the elastic base material of the largest axial direction length is press-fitted in the vibration pipe of the smallest axial direction length. It is a figure explaining the axial direction positional relationship of a spring-plate guide part and a taper part, and has illustrated the case where the elastic base material of minimum length is press-fit in the vibration pipe of maximum length. It is a figure explaining the vortex flowmeter of a prior art.

Claims (3)

A vibration tube having a cylindrical body having an open end is provided, and a pressure receiving plate is attached to the end of the vibration tube so as to be able to receive the vortex fluctuation pressure generated by the vortex generator, and the inside of the cavity inside the vibration tube A vortex signal detecting unit including an elastic base material press-fitted into the vortex signal detecting unit, the vortex signal detecting unit detecting vibration of the pressure receiving plate and transmitting the vibration to the outside as an electric signal; and In the vortex flowmeter having an upper end press-fitted portion that is press-fitted into the upper opening side and a spring plate that is press-fitted into a spring plate press-fitted portion formed on the distal end side of the cavity portion of the vibration tube,
The vibration tube is a spring formed with an inner diameter slightly larger than the inner diameter of the spring plate press-fit portion at the end of the spring plate press-fit portion corresponding to the inlet position when the spring plate is press-fitted into the spring plate press-fit portion. A plate guide portion is provided in the cavity inside the vibration tube, and a tapered portion is provided following the upper end press-fitting portion of the elastic base material. When the elastic base material is inserted, the plate guide portion is larger than the corresponding vibration tube inner diameter. A vortex flowmeter comprising a configuration in which a tapered portion is brought into contact with the upper end press-fitted portion of an elastic base material having an outer diameter. A vibration tube having a cylindrical body having an open end is provided, and a pressure receiving plate is attached to the end of the vibration tube so as to be able to receive the vortex fluctuation pressure generated by the vortex generator, and the inside of the cavity inside the vibration tube A vortex signal detecting unit including an elastic base material press-fitted into the vortex signal detecting unit, the vortex signal detecting unit detecting vibration of the pressure receiving plate and transmitting the vibration to the outside as an electric signal; and In a method of manufacturing a vortex flowmeter having a top plate that is press-fitted into the upper opening side and a spring plate that is press-fitted into a spring-plate press-fitted portion that is formed on the distal end side of the cavity of the vibration tube,
The elastic base material is centered and positioned at two locations above and below the vibrating tube by both guide portions provided at positions immediately before the upper end press-fitting portion and the spring plate press-fitting portion, respectively,
Press the press fitting tool against the elastic base material, and press it to the specified position with the press machine to complete the press fitting.
A method of manufacturing a vortex flowmeter comprising: The both guide portions are formed from an inner diameter of a spring plate press-fitting portion provided in a hollow portion inside the vibration tube at an end portion of the spring plate press-fit portion corresponding to an inlet position when the spring plate is press-fitted into the spring plate press-fit portion. The vortex flowmeter manufacturing method according to claim 2, wherein the spring plate guide portion has a slightly larger inner diameter and a tapered portion provided after the upper end press-fitting portion of the elastic base material.

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