JP4868444B2 - Electromagnetic flow meter - Google Patents

Description

  The present invention detects a liquid flow rate based on a potential difference generated between a pair of detection electrodes by inserting a pair of detection electrodes into a pair of electrode insertion holes formed in a peripheral wall of a measurement tube through which the liquid flows. It relates to an electromagnetic flow meter.

In the conventional electromagnetic flow meter shown in FIG. 13, the pair of detection electrodes 1, 1 are attached so as to penetrate the peripheral walls of the measurement tube 2 from opposite directions (see, for example, Patent Document 1).
JP-A-9-178522 (FIG. 2)

  However, in the conventional electromagnetic flow meter described above, the pair of detection electrodes 1 and 1 must be assembled from two opposite directions with respect to the measurement tube 2, and the detection electrodes 1 and 1 and a circuit board (not shown). ), It was necessary to connect with lead wires 3 and 3, so the assembly workability was poor.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an electromagnetic flow meter capable of improving the workability of assembly.

The electromagnetic flowmeter according to the invention of claim 1 made to achieve the above object includes inserting a pair of detection electrodes into a pair of electrode insertion holes formed in a peripheral wall of a measurement tube through which a liquid flows, A pair of detection electrodes are arranged opposite to each other in a direction substantially perpendicular to the flow direction of the liquid in the measurement tube, and the flow rate of the liquid is determined based on the potential difference generated between the two detection electrodes by applying magnetic flux to the liquid with an electromagnetic coil. In the electromagnetic flow meter to be detected, the pair of detection electrodes are linear, and the pair of electrode insertion holes are in a state where the pair of detection electrodes extend in parallel to each other and protrude from the measuring tube in the same direction. A circuit board having an electric circuit in which a part protruding from the measurement tube of the pair of detection electrodes penetrates and the detection electrodes are conductively connected is provided at the side portion of the measurement tube. is provided integrally with the measuring tube, The case board is provided with a case part that accommodates the middle part of the road board and the measurement tube inside, and both ends of the measurement tube protrude from the outer surface, and the board assembly opening is formed on the same side as the opening of the electrode insertion hole. And a first lid for closing the substrate assembly opening is provided, and the substrate assembly opening side of the case portion is disposed between the circuit board and the measurement tube, and the measurement tube of the pair of detection electrodes. The portions projecting from each other pass through, and a holding member holding the circuit board is accommodated, and the holding member is characterized in that it is locked to an intermediate portion of the measuring tube .

  According to a second aspect of the present invention, in the electromagnetic flowmeter according to the first aspect, the tip of the pair of detection electrodes is fitted and positioned coaxially with the pair of electrode insertion holes on the inner surface of the measurement tube. It is characterized in that a pair of recesses are formed.

  According to a third aspect of the present invention, in the electromagnetic flowmeter according to the first or second aspect, a measuring portion having a pair of flat inner surfaces parallel to each other is provided in the middle portion of the measuring tube, and each flat inner surface is provided. Each electrode housing groove is formed, a pair of electrode insertion holes are arranged on the extension of the electrode housing grooves, and a part of each detection electrode is housed in the electrode housing groove.

According to a fourth aspect of the present invention, in the electromagnetic flowmeter according to any one of the first to third aspects, an O-ring pressing portion having a stepped shape or a flange shape is provided in the middle of each detection electrode to detect the O-ring. Each electrode insertion hole has a large-diameter portion into which the O-ring and the O-ring pressing portion are inserted, and is disposed behind the large-diameter portion, and the O-ring is connected to the O-ring pressing portion. It is characterized in that it has a small-diameter portion sandwiched between them.

According to a fifth aspect of the present invention, in the electromagnetic flowmeter according to the fourth aspect , the O-ring pressing portion has a flange shape, and the holding member is inserted between the large diameter portion of the electrode insertion hole and the detection electrode. It has a feature in that it has a pressing cylinder portion that is abutted against the O-ring pressing portion and through which a portion protruding from the measuring tube of the detection electrode penetrates.

According to a sixth aspect of the present invention, in the electromagnetic flowmeter according to any one of the first to fifth aspects, the holding member extends toward the measuring tube, and the holding member is accommodated in the case portion. It has a feature in that it includes a plurality of locking flexible pieces that come into contact with the outer surface and elastically deform and are restored when the holding member is accommodated in the case portion and locked to the outer surface of the measuring tube.

According to a seventh aspect of the present invention, in the electromagnetic flowmeter according to any one of the first to sixth aspects, an electromagnetic coil is disposed inside the case portion on the side opposite to the circuit board, and the substrate assembly opening in the case portion. A coil assembly opening is formed on the opposite side of the coil, and the coil assembly opening is characterized by being closed by the second lid.

The invention according to claim 8 is characterized in that, in the electromagnetic flow meter according to any one of claims 1 to 6 , an electromagnetic coil is disposed on the same side as the circuit board inside the case portion.

According to a ninth aspect of the present invention, in the electromagnetic flowmeter according to any one of the first to eighth aspects, an excitation current that is intermittent, instantaneous and alternately opposite in direction is passed through the electromagnetic coil that excites the magnetic circuit. The flow rate is calculated based on the potential difference generated between the detection electrodes due to the residual magnetic flux maintained by the magnetic circuit while the exciting current does not flow and the flow of the liquid.

The invention of claim 10 is characterized in that in the electromagnetic flow meter of claim 9 , a semi-hard magnetic material is provided in the middle of the magnetic circuit.

[Invention of Claim 1]
According to the electromagnetic flow meter according to claim 1 configured as described above, a pair of detection electrodes can be inserted from the same direction into an electrode insertion hole formed through the measurement tube. As a result, the assembly workability is improved. In addition, since the pair of detection electrodes can protrude in the same direction, the size of the detection electrodes can be reduced as compared with the case where the detection electrodes protrude in opposite directions.
Also, the case portion has a board assembly opening formed on the same side as the opening of the electrode insertion hole, and when the holding member for holding the circuit board is attached and when the circuit board is accommodated in the case section, the detection electrode Since it can be inserted from the same side, it is excellent in workability. Furthermore, since the board assembly opening is covered with the first lid, the circuit board can be protected.

[Invention of claim 2]
According to the invention of claim 2, when the pair of detection electrodes are inserted into the electrode insertion holes, the tips thereof are fitted into the pair of recesses formed on the inner surface of the measurement tube. As a result, the detection electrodes can be positioned and held in a state where they extend in parallel with each other and protrude from the measuring tube in the same direction.

[Invention of claim 3]
According to the third aspect of the invention, the liquid flowing in the measurement tube smoothly flows in the vicinity of the surface of the detection electrode, so that stable measurement can be performed.

[Invention of claim 4 ]
According to the configuration of the fourth aspect , since the O-ring is crushed in the axial direction or circumferential direction of the detection electrode inside the electrode insertion hole, it is possible to prevent liquid leakage from the electrode insertion hole.

[Invention of claim 5 ]
According to the invention of claim 5 , since the pressing cylinder part formed in the holding member is inserted between the large diameter part of the electrode insertion hole and the detection electrode and is abutted against the O-ring pressing part, the electrode insertion hole In contrast, the detection electrode can be prevented from coming off.

[Invention of claim 6 ]
According to the invention of claim 6 , when the holding member is inserted through the board assembly opening and pushed in, the plurality of locking flexible pieces are locked to the outer surface of the measuring tube and the holding member is assembled. Excellent.

[Invention of Claim 7 ]
According to invention of Claim 7, an electromagnetic coil can be assembled | attached from the coil assembly opening opened to the opposite side to the board | substrate assembly opening among the case parts. Moreover, if the coil assembly opening is closed by the second lid, it is possible to prevent foreign matter from entering the case portion.

[Invention of Claim 8 ]
According to the eighth aspect of the present invention, the electromagnetic coil can be assembled into the case portion from the substrate assembly opening in the same manner as the pair of detection electrodes and the circuit board, and the assembly workability is improved.

[Inventions of Claims 9 and 10 ]
According to the invention of claim 9 , since the exciting current flows intermittently and instantaneously, the power consumption can be extremely reduced. Moreover, it is preferable to provide a semi-hard magnetic material in the middle of the magnetic circuit (invention of claim 10 ).

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. The electromagnetic flow meter 10 of the present invention includes a case portion 11 having a substantially oval container structure, and has a structure in which a measuring tube 20 penetrates a wall portion facing in the longitudinal direction (left-right direction in FIG. 3). Yes. In order to connect the electromagnetic flow meter 10 to a pipe (for example, a water pipe, a chemical liquid pipe, etc.) not shown on the outer peripheral surfaces of both end portions 20A, 20B protruding in the opposite direction from the outer surface of the case portion 11 in the measurement tube 20. Male screw portions 21 and 21 are formed. Then, the electromagnetic flow meter 10 is connected to the pipe, so that the liquid (tap water or chemical) flowing through the pipe passes through the measurement pipe 20 and the flow rate of the liquid is measured. Here, the case part 11 and the measuring tube 20 are integrally formed of an insulating resin.

  As shown in FIG. 2, the case portion 11 has two open surfaces that face each other in a direction orthogonal to the axial direction of the measurement tube 20, and the openings 11 </ b> A and 11 </ b> B are respectively provided with the first lid 12 and the second lid. 13 is closed. Further, as shown in FIG. 5, seal grooves 14 and 14 are formed in the peripheral portions of the openings 11 </ b> A and 11 </ b> B of the case portion 11, respectively, and a seal member (not shown) fitted in the seal grooves 14 and 14 is provided. The inside of the case part 11 is sealed by being crushed at the peripheral parts of the lids 12 and 13. Various parts to be described later may be accommodated inside the case part 11 and resin may be molded around these parts.

  Hereinafter, for convenience of explanation, in the present embodiment, it is assumed that the measurement tube 20 extends in the horizontal direction (left and right direction in FIG. 3) and the openings 11A and 11B of the case portion 11 are arranged side by side in the vertical direction. Of course, this is not a limitation.

  As shown in FIG. 3, the central portion of the measuring tube 20 housed in the case portion 11 has a smaller channel cross-sectional area than both end portions 20A and 20B. Specifically, a measurement unit 26 having a minimum flow path cross-sectional area in the measurement tube 20 is provided in the central portion of the measurement tube 20 in the axial direction. As shown in FIG. 4, the cross-sectional shape of the flow path in the measurement unit 26 is a flat rectangular shape whose dimension in the vertical direction is smaller than that in the width direction (the horizontal direction in FIG. 4). A pair of detection electrodes 40, 40 to be described later is disposed opposite to the measurement unit 26 in the width direction.

  Further, on the upstream side of the measurement unit 26 in the measurement tube 20, a contraction unit 27 that is narrowed so that the flow path cross-sectional area gradually decreases from the upstream end 20 </ b> A of the measurement tube 20 toward the measurement unit 26. And an enlarged portion 28 having a channel cross-sectional area that gradually increases from the measurement unit 26 toward the downstream end 20B.

  As shown in FIG. 4, an electromagnetic coil 72 is accommodated in a region below the measurement tube 20 in the case portion 11, and the tip of the shaft-like core 71 that penetrates the electromagnetic coil 72 is formed by a fixing component (not shown). The measurement tube 20, specifically, is fixed in a state of being abutted against the lower surface of the measurement unit 26. A magnetic flux is applied to the liquid passing through the measuring unit 26 by the electromagnetic coil 72, and at this time, the flow rate of the liquid is measured based on a potential difference generated between the pair of detection electrodes 40 and 40.

  The lower surface opening 11 </ b> B of the case portion 11 is closed by the second lid 13 in a state where the above-described electromagnetic coil 72 is accommodated in the case portion 11. As shown in FIG. 2, the second lid body 13 has a substantially oval shape corresponding to the lower surface opening 11 </ b> B, and a plurality (for example, four) of the second lid body 13 from the inner surface (upper surface) toward the inside of the case portion 11. The cylindrical boss 16 stands upright. These cylindrical bosses 16 are opened upward and are fitted to a plurality of boss receiving cylinder portions 17 (see FIG. 5) protruding from the inner wall surface of the case portion 11 from the lower surface side. Then, a screw component (not shown) inserted into each boss receiving cylinder portion 17 from the upper surface opening 11A (corresponding to the “substrate assembly opening” of the present invention) of the case portion 11 is screwed into the axial center portion of each cylindrical boss 16. And the 2nd cover 13 is assembled | attached in the state which closed the lower surface opening 11B.

  Incidentally, the assembly structure of the pair of detection electrodes 40, 40 with respect to the measurement tube 20 is as follows. As shown in FIG. 4, a pair of electrode support bosses 29, 29 stand upright from the upper surface of the measurement unit 26 in the measurement tube 20. These electrode support bosses 29 and 29 are formed side by side in the width direction of the measuring section 26 (left and right direction in FIG. 4), and the outer peripheral surfaces of the electrode support bosses 29 and 29 are connected by a rib wall 29R ( (See FIG. 5).

  An electrode insertion hole 30 is formed in the axial center of each electrode support boss 29. The electrode insertion hole 30 penetrates the upper wall of the measurement unit 26 and extends in the vertical direction, and opens on the upper surface opening 11A side.

  Specifically, each electrode insertion hole 30 includes a large-diameter portion 30A formed on the opening side, and a small-diameter portion 30B disposed on the back side (downward in FIG. 4) of the large-diameter portion 30A and reduced in a stepped shape. It has. And the detection electrodes 40 and 40 are inserted from the opening of each electrode insertion hole 30 and 30, and the front-end | tip part is arrange | positioned in the flow path in the measurement part 26. FIG. Here, since the opening edge of each electrode insertion hole 30 and 30 is tapering upward toward the upper side, the detection electrodes 40 and 40 can be easily inserted.

  Each of the detection electrodes 40, 40 has a round bar shape with a circular cross section as a whole. Specifically, the tip of the detection electrode 40 is tapered, and a terminal portion 41 having a stepped diameter is formed at the base end. Further, a flange-shaped O-ring pressing portion 42 is formed at an intermediate portion in the axial direction of the detection electrode 40. A pressing cylinder portion 58 of a holding base 50 (corresponding to a “holding member” of the present invention) described below is abutted against the upper surface of the O-ring pressing portion 42, and thereby the electrode insertion of each detection electrode 40, 40 is performed. The holes 30 and 30 are prevented from coming off. The detection electrodes 40, 40 are made of stainless steel, hastelloy, monel, titanium, tantalum, platinum or the like having excellent corrosion resistance.

  As shown in FIG. 4, an O-ring 43 is inserted in the middle of each detection electrode 40, and the O-ring 43 is addressed to the lower surface of the O-ring pressing portion 42. The O-ring 43 is crushed from the circumferential direction between the inner peripheral surface of the large-diameter portion 30 </ b> A of the electrode insertion hole 30 and the outer peripheral surface of the detection electrode 40. Here, the O-ring pressing portion 42 may be pressed downward by the pressing cylinder portion 58 of the holding base 50, and the O-ring 43 may be crushed between the step surfaces 30 </ b> C and 30 </ b> C of the electrode insertion holes 30 and 30. . The O-rings 43 and 43 prevent liquid leakage from the electrode insertion holes 30 and 30.

  Here, as shown in FIG. 6, among the inner surface of the measurement unit 26, a pair of flat inner surfaces 26 </ b> A and 26 </ b> A opposed in the width direction are formed with electrode receiving grooves 26 </ b> B and 26 </ b> B, respectively. These electrode housing grooves 26B are provided on the extension lines of the electrode insertion holes 30 and 30 and have a semicircular cross section. The electrode housing grooves 26B and 26B receive about a half circumference of the arc wall of each of the detection electrodes 40 and 40, and the remaining half circumference is exposed in the flow path of the measuring unit 26 and can be in contact with the liquid. It has become. By adopting such a configuration, the flow of the liquid flows smoothly without being disturbed in the vicinity of the surfaces of the detection electrodes 40, 40, and stable flow rate measurement can be performed.

  Further, a pair of recesses 26C and 26C are formed on the coaxial line of the electrode insertion holes 30 and 30 and the electrode receiving grooves 26B and 26B at the bottom of the inner surface of the measuring unit 26, and the tips of the detection electrodes 40 and 40 are fitted therein. Match. Accordingly, the pair of detection electrodes 40, 40 are arranged in parallel with each other in the width direction of the measurement unit 26, that is, in the direction orthogonal to the flow direction of the liquid flowing through the measurement unit 26, and the base end side is above the measurement unit 26. It is positioned in a protruding state.

  As shown in FIG. 4, a holding base 50 is accommodated in an upper region of the measurement tube 20 in the case portion 11. The holding base 50 is made of, for example, resin, and is attached to the outer surface of the measuring tube 20 in an overlapping manner. As shown in FIG. 2, the holding base 50 includes a substantially rectangular substrate receiving base 51 that is elongated in the axial direction of the measuring tube 20, and a plurality of latches are formed from both sides of the substrate receiving base 51 in the short direction. The flexible pieces 52, 52 have a structure extending toward the measuring tube 20. The locking flexible piece 52 is provided with an arrowhead-shaped locking claw portion 52B at the tip of a band plate portion 52A orthogonal to the substrate receiving base 51. The plurality of locking flexible pieces 52 and 52 are respectively locked to the plurality of locking protrusions 31 and 31 (see FIGS. 4 and 5) protruding from the outer surface of the measuring tube 20, so that the holding base 50 is The outer surface of the measuring tube 20 is locked.

  A pair of electrode holding holes 53 and 53 are formed in the central portion of the substrate receiving base 51 in the longitudinal direction. These electrode holding holes 53, 53 are arranged side by side in the short direction of the substrate receiving table 51, and the detection electrodes 40, 40 projecting upward from the measuring tube 20 pass therethrough (see FIG. 4). ).

  In the substrate receiving table 51, cylindrical pressing cylinder portions 58, 58 protrude from the opening edges of the electrode holding holes 53, 53 toward the electrode support bosses 29, 29. These pressing cylinder portions 58 and 58 are inserted between the large diameter portion 30 </ b> A of each electrode insertion hole 30 and the detection electrode 40 and are abutted against the O-ring pressing portion 42 of each detection electrode 40.

  A circuit board 60 having an electric circuit (not shown) is superposed and held on the upper surface of the board receiving base 51 of the holding base 50. The circuit board 60 is placed on a plurality of rib walls 57, 57 formed on both sides of the holding base 50 in the short direction, and is held in a state of floating from the upper surface of the board receiving table 51.

  The circuit board 60 has a substantially rectangular shape that is elongated in the axial direction of the measuring tube 20, and a pair of terminal holes 61, 61 are formed through the center in the longitudinal direction. These terminal holes 61 and 61 are formed side by side in the short direction of the circuit board 60, and the terminal portions 41 and 41 of the pair of detection electrodes 40 and 40 pass through the terminal holes 61 and 61, respectively. The terminal portions 41 and 41 are soldered to the circuit board 60, for example.

  The upper surface opening 11 </ b> A of the case portion 11 is closed by the first lid 12 in a state where the pair of detection electrodes 40, 40, the holding base 50 and the circuit board 60 are accommodated in the case portion 11. The first lid 12 has a substantially rectangular shape corresponding to the upper surface opening 11A. Then, with the peripheral wall portion of the first lid 12 being directed to the edge of the upper surface opening 11A of the case portion 11, the first lid 12 is formed by male screw parts (not shown) penetrating the four corners of the case portion 11. Is assembled in a state in which the upper surface opening 11A of the case portion 11 is closed.

  The description of the configuration of the electromagnetic flow meter 10 has been described above. By the way, this electromagnetic flow meter 10 is assembled by the following procedure.

  First, the electromagnetic coil 72 is inserted from the lower surface opening 11 </ b> B of the case portion 11, and the shaft-like core 71 is fixed to the lower surface of the measuring unit 26 by a fixing component (not shown). Then, the second lid 13 is screwed to the lower surface opening 11B, and the lower surface opening 11B is closed.

  Next, a pair of detection electrodes 40, 40 fitted with an O-ring 43 is attached to the measurement tube 20. That is, the detection electrodes 40 and 40 are inserted into the electrode insertion holes 30 and 30 from the upper surface opening 11 </ b> A of the case portion 11. At this time, each detection electrode 40 is guided by the electrode insertion hole 30 and the electrode housing groove 26B, and the tip is fitted into the recess 26C. As a result, the pair of detection electrodes 40, 40 are arranged to face each other in parallel in the width direction of the measurement unit 26 (direction perpendicular to the liquid flow direction), and the terminal unit 41 protrudes from the upper surface of the measurement unit 26. Kept in a state.

  Next, the holding base 50 is inserted from the upper surface opening 11 </ b> A of the case portion 11 and assembled to the measurement tube 20. In the process in which the holding base 50 moves toward the measuring tube 20, the locking flexible pieces 52 and 52 extending below the holding base 50 come into contact with the corresponding locking protrusions 31 and 31, respectively. When the holding base 50 is pushed in, the locking flexible pieces 52 and 52 bend outward while being in sliding contact with the locking protrusions 31 and 31, and when the locking claw 52 B gets over the locking protrusion 31. The locking flexible pieces 52 and 52 are restored, and the locking claw portion 52B and the locking projection 31 are locked. As a result, the holding base 50 is accommodated in the case portion 11 and is locked to the outer surface of the measuring tube 20.

  Here, in the process until the holding base 50 is locked to the measuring tube 20, the detection electrodes 40, 40 protruding above the measuring tube 20 are respectively inserted into the electrode holding holes 53, 53 formed in the holding base 50. When inserted and the holding base 50 is locked to the measuring tube 20, the terminal portions 41, 41 provided in the detection electrodes 40, 40 protrude to the upper surface side of the substrate receiving table 51.

  Further, in the process until the holding base 50 is locked to the measuring tube 20, the pressing cylinder portions 58 and 58 protruding from the lower surface of the substrate receiving base 51 are connected to the large diameter portions 30 </ b> A and 30 </ b> A of the electrode insertion holes 30 and 30. When the holding base 50 is inserted between the detection electrodes 40 and 40 and the holding base 50 is locked to the measuring tube 20, the pressing cylinder portions 58 and 58 abut against the O-ring pressing portions 42 and 42 of the detection electrodes 40 and 40. Thus, the detection electrodes 40 and 40 are held in a state of being prevented from being detached from the measuring tube 20 and are crushed in the circumferential direction between the inner peripheral surface of the large-diameter portion 30A and the outer peripheral surface of the detection electrode 40. Liquid leakage is prevented. Here, the O-rings 43, 43 may be crushed in the axial direction between the O-ring pressing portions 42, 42 and the step surfaces 30 </ b> C, 30 </ b> C of the electrode insertion holes 30, 30.

  Next, the circuit board 60 is attached. That is, the circuit board 60 is inserted from the upper surface opening 11 </ b> A of the case portion 11 and placed on the substrate receiving table 51 of the holding base 50. Then, the terminal portions 41, 41 of the detection electrodes 40, 40 protruding from the upper surface of the substrate receiving table 51 pass through the terminal holes 61, 61 formed in the circuit board 60. In this state, the terminal portions 41 and 41 are soldered to the circuit board 60 to be conductively connected. The terminal portions 41 and 41 are preferably pre-soldered or previously surface-treated with copper or nickel having high solder wettability.

  Finally, when the first lid 12 is placed on the upper surface opening 11A, the four corners thereof are screwed, and the upper surface opening 11A is closed, the electromagnetic flow meter 10 is completed.

  The electromagnetic flow meter 10 assembled in the above-described procedure is connected in the middle of a water pipe or a chemical liquid pipe. Then, the flow rate of the liquid is calculated based on the potential difference generated between the pair of detection electrodes 40 and 40 when the liquid passes through the measurement unit 26.

  Thus, according to the electromagnetic flow meter 10 of the present embodiment, the pair of detection electrodes 40, 40 are inserted in the same direction with respect to the electrode insertion holes 30, 30, that is, from the upper surface opening 11A side of the case portion 11. The holding base 50 and the circuit board 60 can also be assembled from the upper surface opening 11 </ b> A side of the case portion 11, similarly to the detection electrodes 40 and 40. Further, the circuit board 60 and the detection electrodes 40 and 40 can be directly conductively connected (soldered) without using lead wires, and the work related to the conductive connection can be performed through the upper surface opening 11A of the case portion 11. it can. Thereby, the workability of the assembly of the electromagnetic flow meter 10 can be improved. In addition, since the pair of detection electrodes 40 and 40 can be projected in the same direction (upper surface opening 11A side), the size of the detection electrodes 40 and 40 can be reduced compared to those projecting in opposite directions, and the installation space can be narrower than the conventional one. It becomes possible to install.

[Second Embodiment]
A second embodiment of the present invention will be described with reference to FIGS. In the present embodiment, the technique described in Japanese Patent Publication No. 59-7930 is applied to the configuration of the first embodiment.
As shown in FIG. 7, the shaft-like core 71 penetrating the electromagnetic coil 72 has a structure in which a yoke 71A and a magnet body 71B are arranged coaxially and are connected together.

  The yoke 71A is made of a high permeability material (for example, electromagnetic soft iron or silicon steel plate) having a high permeability and a small residual magnetic flux, and the magnet body 71B has, for example, a semi-hard magnetic material (having a high permeability, It is a magnetic material that is easily magnetized and has a certain degree of coercive force (coercive force), and is made of, for example, ordinary steel. An electromagnetic coil 72 is wound around the outer periphery of the magnet body 71B, and an excitation circuit (not shown) is connected to the electromagnetic coil 72 so that an excitation current that is intermittent, instantaneous, and alternately opposite in direction flows. It is configured to be. The flow rate is calculated based on the potential difference generated between the detection electrodes 40.40 due to the residual magnetic flux maintained by the magnetic circuit and the flow of the liquid while the excitation current does not flow. Here, in FIG. 7, the magnetic circuit excited by the electromagnetic coil 72 is indicated by a broken line, and as shown in FIG. 7, a magnet body 71B made of a semi-hard magnetic material is provided in a part of the magnetic circuit. ing. The electromagnetic coil 72 is relatively thick and has a small total resistance value.

  The magnetic flux density B generated between the magnetic poles (upper and lower ends of the shaft-like core 71) when the strength of the magnetic field generated in the magnetic circuit by the exciting current flowing through the electromagnetic coil 72 is + Hp and -Hp is a curve shown in FIG. However, when the exciting current becomes zero, the permeance between the magnetic poles is small, so that the strength of the magnetic field passes through the point of zero and stabilizes at the point p or p ′ in FIG. The residual magnetic flux density B in this state is represented by a line segment Ob or Ob 'in FIG.

  In order to increase the residual magnetic flux density, it is a good idea to increase the permeance by narrowing the gap between the magnetic poles. An excitation device (not shown) and a flow rate calculation device (not shown) provided on the circuit board 60 are both a control device (not shown) that generates a required signal based on a pulse of an oscillator (not shown). ) To periodically operate while maintaining a constant relationship with each other in time, and as a result, performs a predetermined action.

  According to the electromagnetic flow meter of the present embodiment, the same effect as that of the first embodiment can be obtained, and since the exciting current flows intermittently and instantaneously in the electromagnetic coil 72, the power consumption can be extremely reduced. it can.

[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 cross-sectional shape of the flow path in the measurement unit 26 is not limited to a rectangular shape, and may be an oval shape having flat inner surfaces 26A and 26A parallel to each other as shown in FIG. In addition, the flow channel of the measurement tube does not have to be narrowed as it approaches the measurement unit, and the cross-sectional area of the flow channel may be constant in the axial direction of the measurement tube.

  (2) The detection electrodes 40, 40 are not limited to a round bar shape, and may be a prismatic shape or a flat plate shape.

  (3) Although the O-ring pressing portion 58 provided in the detection electrodes 40, 40 has a flange shape, the diameter of the detection electrodes 40, 40 is increased in a stepped manner with respect to the tip portion, and the step surface 30C The O-rings 43 and 43 may be crushed between them. Further, as shown in FIG. 10, an annular groove 44 is formed in the middle part of each detection electrode 40, 40 and O-rings 43, 43 are fitted therein, and between the inner peripheral surface of the electrode insertion hole 30. It may be crushed.

  (4) As shown in FIG. 11, the electromagnetic coil 72 may be disposed on the same side as the circuit board 60. In this way, not only the pair of detection electrodes 40, 40, the circuit board 60 and the holding base 50, but also the electromagnetic coil 72 can be inserted and assembled from the upper surface opening 11A of the case portion 11. Will improve.

  (5) In the second embodiment described above, the yokes 71A and 71B are provided at the upper end of the shaft-shaped core 71. However, the following configuration may be used. As shown in FIG. 12, a sheet metal coil holder 73 made of a high magnetic permeability material is coupled to the lower end portion of the magnet body 71B of the shaft-shaped core 71, and this coil holder 73 is provided as a yoke. . The coil holder 73 includes magnetic path forming walls 75 and 75 that stand upright at both sides of the axial core 71 and sandwich the measuring tube 20 in a direction orthogonal to the liquid flow direction. The magnetic flux generated by the current flowing through the electromagnetic coil 72 passes through the pair of magnetic path forming walls 75 and 75. In this way, the efficiency of electromagnetic induction is improved compared to the configuration of the second embodiment, and power consumption is suppressed.

  (6) Examples of desirable semi-hard magnetic materials include those shown in Table 1 below.

The perspective view of the electromagnetic flowmeter which concerns on 1st Embodiment of this invention. Disassembled perspective view of electromagnetic flow meter Side view of electromagnetic flow meter Front view of electromagnetic flow meter Top view of the case Cross section of measuring tube Front sectional view of electromagnetic flow meter according to second embodiment Graph for explaining the remanence of the magnet body Front sectional view of an electromagnetic flow meter according to another embodiment (1) Front sectional view of an electromagnetic flow meter according to another embodiment (3) Front sectional view of an electromagnetic flow meter according to another embodiment (4) Front sectional view of an electromagnetic flow meter according to another embodiment (5) Cross section of a conventional electromagnetic flow meter

Explanation of symbols

10 Electromagnetic flow meter 11 Case 11A Upper surface opening (Board assembly opening)
11B Bottom opening (Coil assembly opening)
12 First lid 13 Second lid 20 Measuring tube 26 Measuring portion 26A Flat inner surface 26B Electrode receiving groove 26C Recess 30 Electrode insertion hole 30A Large diameter portion 30B Small diameter portion 40 Detection electrode 42 O-ring pressing portion 43 O-ring 50 Holding base (Holding member)
58 Pressing cylinder 60 Circuit board 71B Magnet body (semi-hard magnetic material)
72 Electromagnetic coil

Claims (10)

A pair of detection electrodes are respectively inserted into a pair of electrode insertion holes formed through the peripheral wall of the measurement tube through which the liquid flows, and the pair of detection electrodes are substantially orthogonal to the flow direction of the liquid in the measurement tube. In an electromagnetic flowmeter that detects the flow rate of the liquid based on a potential difference generated between the two detection electrodes by applying a magnetic flux to the liquid with an electromagnetic coil.
The pair of detection electrodes are linear.
The pair of electrode insertion holes are formed so that the pair of detection electrodes extend in parallel with each other and are protruded from the measuring tube in the same direction,
A side of the measurement tube is provided with a circuit board having an electric circuit through which the portions protruding from the measurement tube of the pair of detection electrodes penetrate, and the detection electrodes are conductively connected ,
Provided integrally with the measurement tube, including a case portion that accommodates the circuit board and the middle portion of the measurement tube inside, and both end portions of the measurement tube protrude from the outer surface,
In the case portion, a substrate assembly opening is formed on the same side as the opening of the electrode insertion hole, and a first lid for closing the substrate assembly opening is provided,
The case assembly is disposed between the circuit board and the measurement tube on the substrate assembly opening side, and a portion of the pair of detection electrodes protruding from the measurement tube penetrates the circuit portion. A holding member holding the substrate is accommodated,
The electromagnetic flow meter according to claim 1, wherein the holding member is locked to an intermediate portion of the measuring tube.   The pair of recesses, in which the tip ends of the pair of detection electrodes are fitted and positioned on the inner surface of the measurement tube, are coaxial with the pair of electrode insertion holes. The electromagnetic flow meter according to 1.   A measuring portion having a pair of flat inner surfaces parallel to each other is provided in the middle portion of the measuring tube, and an electrode receiving groove is formed on each of the flat inner surfaces to extend the electrode receiving grooves. The electromagnetic flow meter according to claim 1 or 2, wherein a pair of electrode insertion holes are arranged, and a part of each of the detection electrodes is accommodated in the electrode accommodation groove. In the middle of each of the detection electrodes, a stepped or flanged O-ring pressing part is provided, and an O-ring is inserted through the detection electrode,
In each of the electrode insertion holes, a large-diameter portion into which the O-ring and the O-ring pressing portion are inserted together, and a rear side of the large-diameter portion, the O-ring is connected to the O-ring pressing portion. The electromagnetic flowmeter according to any one of claims 1 to 3, further comprising a small-diameter portion sandwiched therebetween. The O-ring pressing part has a flange shape,
The holding member is inserted between the large-diameter portion of the electrode insertion hole and the detection electrode and is abutted against the O-ring pressing portion, and a portion of the detection electrode protruding from the measurement tube passes therethrough. The electromagnetic flowmeter according to claim 4, further comprising a pressed cylinder portion. The holding member extends toward the measurement tube and elastically deforms by contacting the outer surface of the measurement tube in a process in which the holding member is accommodated in the case portion, and the holding member is accommodated in the case portion. 6. The electromagnetic flow meter according to claim 1, further comprising a plurality of locking flexible pieces that are restored and locked to the outer surface of the measuring tube. Inside the case portion, the electromagnetic coil is disposed on the opposite side of the circuit board,
The coil assembly opening is formed on the opposite side of the case portion from the substrate assembly opening, and the coil assembly opening is closed by a second lid. The electromagnetic flow meter according to any one of the above. The electromagnetic flowmeter according to claim 1, wherein the electromagnetic coil is disposed on the same side as the circuit board inside the case portion. The electromagnetic coil that excites the magnetic circuit is intermittently and instantaneously and every time an exciting current having an opposite direction is alternately flowed, and the residual magnetic flux and the liquid flow that the magnetic circuit maintains while the exciting current does not flow. The electromagnetic flowmeter according to claim 1, wherein the flow rate is calculated based on a potential difference generated between the detection electrodes due to the above. The electromagnetic flow meter according to claim 9, wherein a semi-hard magnetic material is provided in the middle of the magnetic circuit.

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