JP4919328B2 - Electromagnetic flow meter - Google Patents

Description

  The present invention relates to an electromagnetic flowmeter in which a pair of detection electrodes and a ground electrode are fixed to a measurement tube and are connected to a liquid flowing through the measurement tube, and the detection electrode and the ground electrode are connected to a signal processing circuit. About.

As the conventional electromagnetic flow meter described above, one in which a thin disk-shaped ground electrode is assigned to both end faces of a measurement pipe connected in the middle of the pipe is known (for example, see Patent Document 1). .
Japanese Patent Laid-Open No. 10-38648 ([0013], FIG. 1)

  By the way, in the conventional electromagnetic flowmeter mentioned above, there existed a possibility that a ground electrode might become trouble in connection with piping.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an electromagnetic flow meter that does not hinder connection with piping.

The electromagnetic flowmeter according to the invention of claim 1 made to achieve the above object is a liquid that flows inside the measurement tube by fixing a pair of detection electrodes and a ground electrode to the measurement tube made of an insulating member. The detection circuit and the ground electrode are connected to the signal processing circuit, and when the magnetic flux is applied to the liquid by the electromagnetic coil, the signal processing circuit detects the flow rate of the liquid based on the potential difference generated between the pair of detection electrodes. In the electromagnetic flow meter for detecting the ground electrode , the ground electrode has a rod-like shape and has a male spiral portion at the distal end portion and a head portion at the proximal end portion, and the measurement tube has a distal end side from the head portion of the ground electrode. An inserted earth electrode insertion hole is formed, and an inner electrode member is provided to cover a part of the inner surface of the measuring tube. The male spiral portion at the tip of the earth electrode is screwed into the spiral hole formed in the inner electrode member. Combine In addition to fixing the inner electrode member to the measuring tube, a coil holder made of sheet metal holding an electromagnetic coil is provided, a through hole is formed in the coil holder, a ground electrode is inserted into the through hole, the head portion and the ground electrode It is characterized in that the coil holder is sandwiched and fixed between the opening edge of the insertion hole .
An electromagnetic flowmeter according to the invention of claim 2 is a method in which a pair of detection electrodes and a ground electrode are fixed to a measurement tube made of an insulating member to conduct a liquid flowing in the measurement tube, and the detection electrode and the ground are connected to each other. In an electromagnetic flow meter in which an electrode is connected to a signal processing circuit and the signal processing circuit detects the flow rate of the liquid based on a potential difference generated between a pair of detection electrodes when a magnetic flux is applied to the liquid by an electromagnetic coil. The electrode has a rod shape and has a head portion at the base end, and the measurement tube is formed with a ground electrode insertion hole in which the tip side of the ground electrode is inserted from the head portion, and the inner surface of the measurement tube An inner electrode member covering a part is provided, and the inner electrode member is fixed to the measurement tube by caulking in a state where the tip of the ground electrode is passed through the fixing hole formed through the inner electrode member, A coil holder made of sheet metal holding a magnetic coil is provided, a through hole is formed in the coil holder, a ground electrode is inserted into the through hole, and the coil holder is sandwiched between the head portion and the opening edge of the ground electrode insertion hole It is characterized by being fixed with.

A third aspect of the present invention, in the electromagnetic flow meter according to claim 1 or 2, a total of Hakakan and provided integrally houses the middle portion of the measurement pipe and casing portion having both ends protruding from the outer surface of the measuring tube And a circuit board having a signal processing circuit is accommodated in the case portion, and a ground electrode is provided in a portion of the measurement tube accommodated in the case portion.

According to a fourth aspect of the present invention, in the electromagnetic flowmeter according to any one of the first to third aspects, a flow rate measurement unit is formed by narrowing a central portion in the axial direction of the measurement tube, and the pair of detection electrodes is a flow rate measurement The ground electrode is characterized in that it is disposed on both sides of the flow rate measuring unit in a pair.

According to a fifth aspect of the present invention, in the electromagnetic flow meter according to any one of the first to fourth aspects, the inner electrode member has a cylindrical shape fitted inside the measuring tube.

According to a sixth aspect of the present invention, in the electromagnetic flowmeter according to any one of the first to fifth aspects, an O-ring mounting recess is formed in an intermediate portion in the axial direction of the ground electrode, and the O-ring is mounted thereon. However, it has characteristics.

According to a seventh aspect of the present invention, in the electromagnetic flow meter according to any one of the first to sixth 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 8 is characterized in that, in the electromagnetic flow meter of claim 7 , a semi-hard magnetic material is provided in the middle of the magnetic circuit.

[Inventions of Claims 1 , 2, 4 and 5 ]
In the electromagnetic flowmeter according to claims 1 and 2 , since the ground electrode penetrates into and out of the measurement pipe and is not configured to be directed to the end face of the measurement pipe as in the prior art, the ground electrode is connected to the pipe. Will not be a hindrance. Further, since the contact area with the liquid is increased, electrical noise mixed through the liquid can be more effectively prevented. Thereby, the reliability of the flow rate measurement value is improved. Further, according to the first aspect, the inner electrode member is fixed to the measuring tube by the earth electrode, and the earth electrode is prevented from coming off from the earth electrode insertion hole. Further, since both the coil holder holding the electromagnetic coil by the ground electrode and the inner electrode member can be fixed, the assembling work can be reduced and the number of parts can be reduced. Here, the ground electrodes, as in the invention of claim 4, it is rather preferable that disposed on both sides of the flow measuring unit which detects electrode is arranged in a pair, the inner electrode member, according to claim 5 As in the invention, it is preferable to have a cylindrical shape fitted inside the measuring tube.

[Invention of claim 3 ]
Electromagnetic flow meter according to claim 3, A over scan electrodes, because they are located inside the case unit with the signal processing circuit, ground electrodes, provided at both ends of the measuring tube which projects from the outer surface of the case portion Compared to the case, the connection structure between the signal processing circuit and the ground electrode can be simplified.

[Invention of claim 6 ]
According to the sixth aspect of the present invention, it is possible to prevent liquid leakage from the ground electrode insertion hole.

[Inventions of Claims 7 and 8 ]
According to the invention of claim 7 , 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 8 ).

[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. A pipe (for example, a water pipe or a chemical pipe) (not shown) is connected to both end portions 20A and 20B protruding in the opposite direction from the outer surface of the case portion 11 of the measurement pipe 20, so that a liquid flowing through the pipe (water tap) Water or chemical) passes through the measuring tube 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 FIGS. 5 and 6, seal grooves 14, 14 are formed in the peripheral portions of the openings 11 </ b> A, 11 </ b> B of the case portion 11, respectively, and are not shown in the drawings fitted into the seal grooves 14, 14. The seal member is crushed at the peripheral portions of the lid bodies 12 and 13 so that the inside of the case portion 11 is sealed. 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.

  Male screw portions 21 and 21 for connecting the electromagnetic flow meter 10 to the pipe are formed on the outer peripheral surfaces of both end portions 20A and 20B of the measuring tube 20. Moreover, as shown in FIG. 3, the center part accommodated in the case part 11 among the measurement pipe | tubes 20 has a flow-path cross-sectional area narrower than both ends 20A and 20B. Specifically, a flow rate measurement unit 26 having a minimum flow path cross-sectional area in the measurement tube 20 is provided in the central portion in the axial direction of the measurement tube 20. As shown in FIG. 4, the cross-sectional shape of the flow path in the flow rate measurement unit 26 is a flat rectangular shape whose vertical dimension is smaller than that in the width direction (left-right direction in FIG. 4). A pair of detection electrodes 40, 40 to be described later is disposed opposite to the flow rate measurement unit 26 in the width direction.

  On the upstream side of the flow rate measurement unit 26 in the measurement pipe 20, a contraction part 27 constricted so that the flow path cross-sectional area gradually decreases from the end 20 A on the upstream side of the measurement pipe 20 toward the flow rate measurement unit 26. In the downstream side of the flow rate measuring unit 26, there is provided an enlarged portion 28 whose flow path cross-sectional area gradually increases from the flow rate measuring unit 26 toward the downstream end 20B.

  As shown in FIG. 4, a pair of electrode support bosses 29 and 29 stand upright from the upper surface of the flow rate measuring unit 26 in the measurement tube 20. These electrode support bosses 29 and 29 are formed side by side in the width direction (left and right direction in FIG. 4) of the flow rate measuring unit 26, and the outer peripheral surfaces of these electrode support bosses 29 and 29 are connected by a rib wall 29R. (See FIG. 5).

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

  Specifically, each detection electrode insertion hole 30 has a large-diameter portion 30A formed on the opening side, and a small-diameter portion 30B that is disposed on the back side (downward in FIG. 4) of the large-diameter portion 30A and has a stepped shape. And. The detection electrodes 40, 40 are inserted from the openings of the detection electrode insertion holes 30, 30, and the tip portions are arranged in the flow paths in the flow rate measurement unit 26. Here, since the opening edge of each detection electrode insertion hole 30 and 30 is tapering upward toward the upper side, it is easy to insert the detection electrodes 40 and 40.

  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 the holding base 50 described below is abutted against the upper surface of the O-ring pressing portion 42, thereby preventing the detection electrodes 40, 40 from coming off from the detection electrode insertion holes 30, 30. ing. 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 detection electrode insertion hole 30 and the outer peripheral surface of the detection electrode 40. The O-rings 43 and 43 prevent liquid leakage from the detection electrode insertion holes 30 and 30. 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 detection electrode insertion holes 30 and 30.

  Here, as shown in FIG. 7, electrode receiving grooves 26 </ b> B and 26 </ b> B are formed on a pair of flat inner surfaces 26 </ b> A and 26 </ b> A that face each other in the width direction among the inner surfaces of the flow rate measuring unit 26. These electrode housing grooves 26B are provided on the extended lines of the detection 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 flow rate 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 detection electrode insertion holes 30 and 30 and the electrode housing grooves 26B and 26B at the bottom of the inner surface of the flow rate measurement unit 26, and the tip of each detection electrode 40 and 40 is formed here. Are mated. Accordingly, the pair of detection electrodes 40, 40 are arranged in parallel with each other in the width direction of the flow rate measurement unit 26, that is, in the direction orthogonal to the flow direction of the liquid flowing through the flow rate measurement unit 26, and the base end side is the flow rate measurement unit 26. Is positioned so as to protrude upward.

  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, 52 are respectively locked to the plurality of locking protrusions 31, 31 (FIGS. 5 and 6) protruding from the outer surface of the measuring tube 20, and the holding base 50 is connected to the measuring tube. 20 is locked to the outer surface.

  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 press cylinder portions 58 and 58 are inserted between the large diameter portion 30 </ b> A of each detection electrode insertion hole 30 and the detection electrode 40 and are abutted against the upper surface of the O-ring press portion 42 of each detection electrode 40. .

  A circuit board 60 having a signal processing 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, and the potentials detected by the pair of detection electrodes 40 and 40 are input to the signal processing circuit, respectively.

  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.

  As shown in FIG. 4, an electromagnetic coil 72 wound around a shaft-shaped core 71 is accommodated in a region below the measurement tube 20 in the case portion 11. The shaft-like core 71 stands up from a coil holder 73 made of sheet metal, and a tip portion is abutted against the lower surface of the measuring tube 20, specifically, the flow rate measuring unit 26. Magnetic flux is applied to the liquid passing through the flow rate measuring unit 26 by the electromagnetic coil 72, and at this time, the flow rate of the liquid is measured based on the potential difference generated between the pair of detection electrodes 40, 40.

  As shown in FIG. 2, the coil holder 73 includes a long plate-shaped laying sheet metal portion 74 addressed to the lower surface of the measuring tube 20 and a pair of erected sheet metal portions 75 and 75 erected from both sides of the laying sheet metal portion 74. Is provided as a unit. The standing sheet metal parts 75 and 75 have a structure in which a sheet metal piece protruding to the side of the laying sheet metal part 74 is bent at a right angle in the middle and is raised upward. As shown in FIG. 4, the upright portions of the upright sheet metal portions 75 and 75 are arranged in the gaps between the side wall of the case portion 11 and the measuring tube 20, respectively, and sandwich the flow rate measuring portion 26 in the width direction ( (See FIG. 4). When the electromagnetic coil 72 is excited, the magnetic flux passing through the flow rate measuring unit 26 in the flat direction (vertical direction in FIG. 4) from the front end surface of the shaft-like core 71 passes through the pair of upright sheet metal portions 75 and 75. Return to the shaft core 71. That is, the coil holder 73 constitutes a part of the magnetic path.

  Both ends of the laying sheet metal portion 74 are abutted against the end surfaces of the boss portions 24 and 24 projecting downward from the measuring tube 20 and the rib wall 24R. Through holes 74 </ b> A and 74 </ b> A are formed at both ends of the laying sheet metal portion 74. Ground electrodes 23 and 23, which will be described later, are inserted into the through holes 74A and 74A, and the coil holder 73 is fixed to the lower surface side of the measuring tube 20 by the ground electrodes 23 and 23.

  Specifically, as shown in FIG. 3, in the coil holder 73, the peripheral portions of the through holes 74 </ b> A and 74 </ b> A are sandwiched between the end surfaces of the boss portions 24 and 24 and the head portion 23 </ b> B of the ground electrode 23. Thereby, the coil holder 73 is fixed to the measuring tube 20, and the ground electrodes 23 and 23 and the laying sheet metal portion 74 are in a conductive state.

  One end of a lead wire (not shown) is connected to the laying sheet metal portion 74, and the other end of the lead wire passes through the inside of the case portion 11 and is connected to the signal processing circuit of the circuit board 60.

  In the laying sheet metal portion 74, a positioning hole (not shown) is formed in the vicinity of one through hole 74A, and the positioning convex portion 24T (see FIG. 6) integrally formed with the rib wall 24R of the measuring tube 20 is formed. (See below). As a result, the coil holder 73 is positioned with respect to the measuring tube 20, and an assembly error of the coil holder 73 is prevented. The coil holder 73 is preferably made of a high magnetic permeability material.

  The lower surface opening 11 </ b> B of the case portion 11 is closed by the second lid 13 in a state where the electromagnetic coil 72 and the coil holder 73 described above are 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. 6) protruding from the inner wall surface of the case portion 11 from the lower surface side. Then, a screw component (not shown) inserted through the boss receiving cylinder portion 17 from the upper surface opening 11A of the case portion 11 is screwed into the axial center portion of each cylindrical boss 16, and the second lid 13 closes the lower surface opening 11B. It is assembled to the state.

  Now, metal inner electrode members 22 and 22 are provided inside the both end portions 20A and 20B of the measuring tube 20. The inner electrode members 22 and 22 have, for example, a cylindrical shape and are fitted inside the measurement tube 20. In other words, the entire inner circumference of both end portions 20 </ b> A and 20 </ b> B of the measuring tube 20 is covered with the inner electrode members 22 and 22.

  A spiral hole 22A is formed in the inner wall of the inner electrode member 22 on the inner side of the case portion 11, and a ground electrode 23 penetrating from the side of the outer wall of the measuring tube 20 is screwed to the inner wall. ing.

  Specifically, a pair of boss portions 24, 24 protruding toward the lower surface opening 11 </ b> B of the case portion 11 are integrally formed in a portion of the measuring tube 20 accommodated inside the case portion 11. Ground electrode insertion holes 24A, 24A that pass through the peripheral wall of the measurement tube 20 and open to the lower surface opening 11B side are formed in the axial center portions of the boss portions 24, 24. As shown in FIG. 6, rib walls 24 </ b> R protrude from the outer peripheral surfaces of the boss portions 24 and 24.

  The ground electrodes 23, 23 are inserted into the ground electrode insertion holes 24A, 24A from the lower surface opening 11B side. The tip of the ground electrode 23 is a male spiral portion 23A having a stepped diameter, and the male spiral portion 23A enters the measurement tube 20 and is screwed into the spiral hole 22A of the inner electrode member 22. . As a result, the inner electrode members 22 and 22 are fixed inside the both end portions 20A and 20B of the measuring tube 20, and the pair of inner electrode members 22 and 22 housed inside the measuring tube 20 and the measuring tube 20 are provided. The laying sheet metal portion 74 disposed outside the slab is brought into a conductive state via the pair of ground electrodes 23 and 23. The potential of the liquid flowing through the measuring tube 20 is applied to a signal processing circuit (not shown) provided on the circuit board 60 via the ground electrodes 23, 23, the coil holder 73 (laying sheet metal portion 74), and lead wires. input.

  Of the ground electrode 23, an O-ring groove 23 </ b> C (corresponding to an “O-ring mounting recess” according to the present invention) having a diameter reduced stepwise over the entire circumference is provided on the head 23 </ b> B side from the male spiral portion 23 </ b> A. The O-ring 25 is fitted in the O-ring groove 23C. The O-ring 25 is crushed between the inner peripheral surface of the ground electrode insertion hole 24A. Thereby, the space between the ground electrode insertion hole 24A and the ground electrode 23 is sealed, and liquid leakage from each of the ground electrode insertion holes 24A and 24A is prevented. The inner electrode members 22 and 22 and the ground electrodes 23 and 23 in contact with the liquid are preferably made of stainless steel, hastelloy, monel, titanium, tantalum, platinum or the like having excellent corrosion resistance. The functions of the ground electrodes 23 and 23 are the same as those of a ground ring (a liquid contact ring) that is generally provided in a conventional electromagnetic flow meter, and thus detailed description thereof is omitted.

  This is the end of the description of the configuration of the electromagnetic flow meter 10 of the present embodiment. The electromagnetic flow meter 10 is connected in the middle of a water pipe or a chemical liquid pipe. The signal processing circuit takes in the potentials of the two detection electrodes 40 and 40 when the liquid passes through the flow rate measuring unit 26 using the potential of the liquid detected by the ground electrodes 23 and 23 as a reference potential, and both the detection electrodes 40 and 40. The flow rate is calculated from the potential difference between them. Thereby, the influence of the electric noise which propagates in the liquid can be effectively prevented, and an accurate flow rate can be measured.

  As described above, according to the electromagnetic flow meter 10 of the present embodiment, the ground electrodes 23, 23 penetrate the peripheral wall constituting the measuring tube 20 inward and outward, and are configured to be directed to the end face of the measuring tube as in the related art. Therefore, the ground electrodes 23 and 23 do not hinder the connection with the piping. Further, since the ground electrodes 23 and 23 are disposed inside the case portion 11 together with the signal processing circuit, the ground electrodes 23 and 23 are provided at both end portions 20A and 20B of the measuring tube 20 projecting from the outer surface of the case portion 11. Compared to the case, the connection structure between the signal processing circuit and the ground electrodes 23 and 23 can be simplified. Further, since both the coil holder 73 holding the electromagnetic coil 72 and the inner electrode members 22 and 22 can be fixed by the ground electrodes 23 and 23, the assembling work can be reduced and the number of parts can be reduced. .

[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. 8, 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 integrally.

  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. 8, the magnetic circuit excited by the electromagnetic coil 72 is indicated by a broken line, and as shown in FIG. 8, 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 in the electromagnetic coil 72 is + Hp and -Hp is a curve shown in FIG. However, when the excitation 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 flow path of the measurement pipe 20 does not have to be narrowed as it approaches the flow rate measurement unit 26, and the cross-sectional area of the flow path may be constant in the axial direction of the measurement pipe 20.

(2) In the above embodiment, the inner electrode members 22 and 22 have a cylindrical shape . However, as shown in FIGS. 10A and 10B, a so-called half-pipe shape in which a cylindrical body is vertically divided may be used. Alternatively, as shown in FIGS. 11A and 11B , a flat strip shape may be used.

(3) In the above embodiment, the inner electrode members 22 and 22 are fitted inside the measuring tube 20, but the inner electrode members 22 and 22 are not necessarily required, and FIG. 12 (A) and FIG. 12 (B). As shown in FIG. 9, a configuration in which only the ground electrode 23 is provided and no inner electrode member is provided may be employed. In this case, the measuring tube 20 and the ground electrodes 23 and 23 may be integrally provided by insert molding. In addition, since the contact area with the liquid becomes larger when the inner electrode members 22 and 22 are provided, the influence of electrical noise can be effectively prevented, and the reliability of the flow rate measurement value is improved.

  (4) In the above embodiment, the measurement pipe 20 is configured to be spirally connected to the pipe. However, flange portions are formed at both ends of the measurement pipe 20 to be flange-connected to the pipe. You may comprise as follows.

  (5) In the above embodiment, the ground electrode 23 and the inner electrode member 22 are screwed together. However, a fixing hole is formed in the inner electrode member 22 so that the tip of the ground electrode 23 is fixed therefor. The inner electrode member 22 may be fixed to the measurement tube 20 by caulking (smashing) in a state of penetrating the hole.

  (6) The tip side of the ground electrode 23 from the head portion 23B is composed of a large diameter portion 23D and a small diameter portion 23E as shown in FIG. 13, and a step portion between the large diameter portion 23D and the small diameter portion 23E (the present invention). The O-ring 25 may be attached to the “O-ring attachment recess”.

  (7) 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 Bottom 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 (A) Front view, (B) Partial side sectional view of an electromagnetic flowmeter according to another embodiment (2) (A) Front view, (B) Partial side sectional view of an electromagnetic flowmeter according to another embodiment (2) (A) Front view, (B) Partial side sectional view of an electromagnetic flowmeter according to another embodiment (3) Partial sectional side view of an electromagnetic flow meter according to another embodiment (6)

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Electromagnetic flowmeter 11 Case part 20 Measuring tube 22 Inner electrode member 22A Spiral hole 23 Ground electrode 23A Male spiral part 23B Head part 23C O-ring groove (O-ring mounting recess)
24A Ground electrode insertion hole 25 O-ring 26 Flow rate measuring unit 40 Detection electrode 60 Circuit board 72 Electromagnetic coil 73 Coil holder 74A Through hole

Claims (8)

A pair of detection electrodes and a ground electrode are fixed to a measurement tube made of an insulating member so that the liquid flowing through the measurement tube is conducted, and the detection electrode and the ground electrode are connected to a signal processing circuit, and an electromagnetic coil In the electromagnetic flowmeter in which the signal processing circuit detects the flow rate of the liquid based on a potential difference generated between the pair of detection electrodes when a magnetic flux is applied to the liquid by:
The ground electrode has a rod shape and has a male spiral portion at the distal end thereof and a head portion at the proximal end portion,
The measurement tube is provided with an inner electrode member that covers a part of the inner surface of the measurement tube, and is formed with a ground electrode insertion hole in which the tip side of the ground electrode is inserted from the head portion.
While fixing the inner electrode member to the measuring tube by screwing the male spiral portion of the tip of the earth electrode into the spiral hole formed in the inner electrode member,
A coil holder made of sheet metal that holds the electromagnetic coil is provided, a through hole is formed in the coil holder, the ground electrode is inserted into the through hole, and between the head portion and the opening edge of the ground electrode insertion hole An electromagnetic flowmeter characterized in that the coil holder is fixed with a clamp . A pair of detection electrodes and a ground electrode are fixed to a measurement tube made of an insulating member so that the liquid flowing through the measurement tube is conducted, and the detection electrode and the ground electrode are connected to a signal processing circuit, and an electromagnetic coil In the electromagnetic flowmeter in which the signal processing circuit detects the flow rate of the liquid based on a potential difference generated between the pair of detection electrodes when a magnetic flux is applied to the liquid by:
The ground electrode has a rod-like shape and has a head portion at its base end,
The measurement tube is provided with an inner electrode member that covers a part of the inner surface of the measurement tube, and is formed with a ground electrode insertion hole in which the tip side of the ground electrode is inserted from the head portion.
While fixing the inner electrode member to the measurement tube by caulking in a state where the tip of the ground electrode is passed through a fixing hole formed through the inner electrode member,
A coil holder made of sheet metal that holds the electromagnetic coil is provided, a through hole is formed in the coil holder, the ground electrode is inserted into the through hole, and between the head portion and the opening edge of the ground electrode insertion hole An electromagnetic flowmeter characterized in that the coil holder is fixed with a clamp . A circuit board that is provided integrally with the measurement tube, includes a case portion that accommodates an intermediate portion of the measurement tube, and both ends of the measurement tube protrude from the outer surface, and has the signal processing circuit inside the case portion Is housed,
3. The electromagnetic flow meter according to claim 1, wherein the ground electrode is provided in a portion of the measurement tube accommodated in the case portion. 4. A flow rate measurement part is formed by narrowing the central part in the axial direction of the measurement pipe,
The pair of detection electrodes are arranged in the flow rate measurement unit,
The electromagnetic flowmeter according to any one of claims 1 to 3, wherein the ground electrodes are arranged on both sides of the flow rate measuring unit in a pair. The inner electrode member, an electromagnetic flowmeter according to any one of claims 1 to 4, characterized in that a cylindrical shape is fitted to the inside of the measuring tube. 6. The electromagnetic flow meter according to claim 1, wherein an O-ring mounting recess is formed in an intermediate portion in the axial direction of the ground electrode, and an O-ring is mounted thereon. 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 flow meter 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 flowmeter according to claim 7, wherein a semi-hard magnetic material is provided in the middle of the magnetic circuit.

Images