JP2006133034A - Metal detection sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal detection sensor capable of preventing internal penetration of water droplets adhering by condensation by a sealing resin part, and preventing breakage of a ferrite core even when thermal expansion or thermal shrinkage is repeated by a sudden temperature change. <P>SOLUTION: The ferrite core 3 comprises a cylindrical part 3b to be inserted into a center aperture of a winding shell part 2a of a coil bobbin 2, and a planar part 3a to be stored in a recessed plane 8 of a collar part 2c of the coil bobbin 2. Since the recessed plane 8 of the collar part 2c is blocked by a substrate surface of a control substrate 4, a sealing resin 5 of the sealing resin part for sealing the body 1 inside is not integrated with the ferrite core 3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a metal detection sensor.

  Conventionally, as a sensor for detecting an object. There is a mechanical contact switch in which the actuator is driven by the object to be detected and the contact is driven, but it can be applied when high reliability is required in terms of contact opening, chattering, contact life, etc. There wasn't.

  On the other hand, there is a photoelectric sensor as a sensor that detects a detection target object by being shielded from light by the detection target object or by an increase in reflected light, but it is likely to malfunction in an environment where dust, dust, molding waste, etc. are floating. The installation environment is limited.

On the other hand, a metal detection (metal identification) sensor is also provided that detects the metal object from the change in the oscillation level of the oscillation circuit caused by the change in the impedance of the coil connected to the oscillation circuit due to the proximity of the metal object. (For example, Patent Document 1).
Japanese Patent Laid-Open No. 10-143703 (FIG. 1, paragraph number 0041)

  By the way, the metal detection sensor shown in Patent Document 1 as described above has a configuration in which the core portion and the coil portion are exposed without considering waterproofing or the like. For this reason, in a use environment, there have been problems such as water droplets or the like invading and causing a malfunction, or a core made of ferrite or the like being damaged by direct impact.

  The present invention has been made in view of the above-described points, and the object of the present invention is to provide a sealing resin that prevents internal penetration of water droplets adhering to the sealing resin portion due to condensation or the like and forms the sealing resin portion. A metal detection sensor that prevents the ferrite core from being damaged even if repeated thermal expansion or contraction due to rapid temperature changes is prevented by preventing the integration of the ferrite core and the coil bobbin and the ferrite core. It is to provide.

  In order to achieve the above object, according to the first aspect of the present invention, there is provided a metal detection sensor for detecting a metal object on the basis of a change in oscillation output caused by a change in impedance of the coil while connecting a high frequency oscillation output to the coil. Is a box-shaped body that constitutes a detection surface, a coil is wound around the winding body, and a coil bobbin made of synthetic resin is disposed on the bottom surface with one end of the winding body facing the bottom surface in the body, A control board that is placed and fixed on the outward end surface of the flange part with the substrate surface facing the outward end surface of the flange part integrally provided on the other end side of the winding body part, and is housed in the body, and the winding A columnar portion serving as a magnetic core of the coil is inserted into the central through hole of the body portion, and the plate-shaped portion having a plate surface that is integrally coupled to one end of the columnar portion and substantially orthogonal to the axis of the columnar portion is the control. Occlusion formed between the substrate and the buttocks A ferrite core disposed inside the body and a sealing resin portion that fills the inside of the body and seals the inside of the body, and connects the coil to a sensor circuit mounted on the control board. Features.

  According to the first aspect of the present invention, since the entire sensor components such as the control board and the coil disposed in the body can be sealed, the body can be used even in an environment where water droplets are likely to adhere, such as a place where condensation is likely to occur. Water droplets can be prevented from penetrating into the inside, so that it is possible to prevent the occurrence of malfunction due to water droplets without problems even in usage environments where water droplets are likely to adhere, and the sealing resin constituting the sealing resin portion is a ferrite core. Therefore, the ferrite core and the sealing resin with different linear expansion coefficients are not integrated, or the coil bobbin and the ferrite core are not integrated via the sealing resin. Repeated heat shrinkage can prevent the fragile ferrite core from being damaged, and the sensor components can be compacted. Miniaturization also becomes possible because that.

  According to a second aspect of the present invention, in the first aspect of the present invention, the collar is provided with an elastic expansion / contraction portion that expands and contracts in a direction parallel to the outward end surface and in a direction perpendicular to the end surface.

  According to the invention of claim 2, the shock when the metal detection sensor is dropped is absorbed by the expansion and contraction of the elastic expansion and contraction portion of the flange portion of the coil bobbin, and the flat plate portion of the fragile ferrite core is damaged by the shock. Can be prevented.

  The invention of claim 3 is characterized in that, in the invention of claim 1 or 2, an air vent hole communicating with the inside and the outside is provided on the bottom surface of the body.

  According to the invention of claim 3, when the sealing resin is poured into the body and sealed, the air bubbles accumulated on the bottom surface in the body can be discharged out of the body from the air vent hole. Air bubbles can be prevented from being ejected to the sealing surface on the opening side, and as a result, no bubble marks remain on the sealing surface of the sealing resin portion, and the appearance is beautiful.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, a part of the ground-side coil terminal of the pair of coil terminals connected to the tip of the coil can be seen from the detection surface side of the body. It is provided as follows.

  According to the invention of claim 4, static electricity can be discharged to the coil terminal on the ground side provided so that the charged metal object can be seen on the detection surface when approaching the detection surface. It is possible to prevent the elements of the sensor circuit section being damaged from being damaged by electromagnetic induction.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the substrate surface opposite to the element mounting surface of the control substrate is connected to the ground and substantially covers the entire substrate surface. An electromagnetic shielding pattern made of a conductive metal foil is provided.

  According to the invention of claim 5, it is possible to prevent the magnetic flux of the high frequency magnetic field generated by the coil from leaking in the direction opposite to the detection surface.

  The present invention can seal the entire sensor components such as control boards and coils arranged in the body, so that water droplets can enter the body even in environments where water droplets are likely to adhere, such as places where condensation is likely to occur. Therefore, it is possible to prevent the occurrence of malfunction due to water droplets without problems even in the usage environment where water droplets are likely to adhere, and the sealing resin constituting the sealing resin portion does not contact the ferrite core, The ferrite core and the sealing resin with different linear expansion coefficients are not integrated, or the coil bobbin and the ferrite core are not integrated via the sealing resin. Therefore, thermal expansion and contraction are repeated due to a rapid temperature change. Can prevent the fragile ferrite core from being damaged, and the sensor components can be gathered in a compact size. There is an effect that it is possible.

  The present invention will be described below with reference to an embodiment.

  In this embodiment, as shown in FIGS. 1 and 2, a coil bobbin 2, a ferrite core 3, and a sensor circuit are formed on the bottom of a resin-made box-shaped body 1 that is flat and has one surface opened and the bottom side is a sensor detection surface. In a state in which the block of the sensor component constructed by assembling the control board 4 in the order of the mounting of the control board 4 is housed, the entire inside of the cylindrical body 1 is removed from the sealing resin 5 such as epoxy resin or urethane resin. The lead wire 20 sealed with a resin sealing portion and connected to the circuit pattern of the control board 4 is led out to the outside.

  The body 1 has a pair of outer corners on one diagonal line as a recess 6 that is recessed inward from the back side of the flange 1a formed on the opening side of the body 1 to the bottom of the body 1. It is used as the escape part of the attachment screw (not shown) inserted in the attachment hole 7 provided in the flange 1a.

  The coil bobbin 2 is composed of a cylindrical winding body 2a around which a coil 10 for generating a high-frequency magnetic field for detection is wound on the outer periphery, and outward flanges 2b and 2c integrally formed at both ends of the winding body 2a. The outer shape of the flange 2b arranged on the bottom side of the body 1, which is a molded product, escapes from the inner corner bulged into the body 1 corresponding to the recess 6 and corresponds to the recess 6 A pair of inner corners on a diagonal line that is not matched is shaped so that it does not rattle when the collar 2b is placed on the bottom of the body 1. Moreover, the site | part matched with the above-mentioned inner corner part protrudes on both sides of the winding drum part 2a, and the coil terminal 9 which connects the wire end of the coil 10 is connected to the protruding part in parallel with the winding drum part 2a. Moreover, it is erected by insert molding so as to pass through the side of the flange portion 2c. The coil terminal 9 is also protruded on the side of the flange 2b facing the bottom of the body 1. As shown in FIG. 5, a hole 21 for inserting the protruding tip is passed through the bottom of the body 1.

  The flange portion 2b arranged on the opening side of the body 1 has a disc shape, and the outer end surface of the disc-shaped flat plate portion 3a of the ferrite core 3 is formed on the outer end surface on the opening side of the body 1 as the inner periphery. A concave plane 8 is formed to be stored and placed along the surface. On this concave plane 8, as shown in FIG. 3 (a), a plurality of concentric annular grooves 11 (back) are formed, and the outer peripheral surface of the peripheral wall 8a surrounding the periphery is formed. As shown in FIG. 3B, a plurality of (two in the embodiment) annular grooves (recesses) 12 are formed in the vertical direction over the entire circumference. As shown in FIG. 4 (b), the groove 11 of the concave plane 8 is ridged in the same direction when a force in a direction parallel to the concave plane 8 (X and Y directions in FIG. 3 (a)) is applied to the flange portion 7c. The part 7c is bent, and the elastic expansion-contraction part which absorbs the impact of this direction is comprised. Further, the groove 12 of the peripheral wall 8a bends the peripheral wall 8a in the same direction when a force is applied in the vertical direction of the peripheral wall 8a (Z direction in FIG. 4A) as shown in FIG. 3B. The elastic expansion and contraction part which absorbs the impact of is constituted. The cross sections of both grooves 11 and 12 are still U-shaped.

  The ferrite core 3 is composed of a thin circular plate-shaped portion 3a and a columnar portion 3b integrally formed at the center of the back surface of the plate-shaped portion 3a. The cylindrical portion 3b is inserted into the center through hole 13 of the winding body portion 2a of the coil bobbin 2 when the flat plate-like portion 3a is placed on the concave plane 8 in the center of the surface of The columnar portion 3 a becomes the magnetic core of the coil 10. Here, the thickness of the flat plate portion 3a is smaller than the height of the peripheral wall 8a of the concave plane 8, so that it does not jump out of the concave plane 8 as shown in FIG.

  The control board 4 has an outer shape that corresponds to the planar shape of the bottom of the body 1, and an oscillation circuit that generates a high-frequency electric field by applying a high-frequency signal to the coil 10 of the coil bobbin 2 and a metal object are present in the high-frequency electric field. An element such as an IC 14 that constitutes a sensor circuit including a signal processing circuit that detects the presence of a metal object by detecting that the amplitude of a high-frequency signal accompanying a change in impedance of the coil 10 has decreased or that oscillation has stopped is provided on the body 1. The conductive metal foil layer for magnetic shielding (for example, copper foil layer) is mounted on the opening side surface of the body 1 and prevents the magnetic flux generated by the coil 10 from leaking to the opening side of the body 1 on the bottom side surface of the body 1. The ground pattern 15 is formed on the back surface of the control board 4 so as to cover the entire back surface as shown in FIG. And the back surface side is mounted on the end surface of the surrounding wall 8a of the concave plane 8 of said collar part 2c, and the concave plane 8 is made into a closed space. Further, the tips of the coil terminals 9, 9 protruding from the flange 2 b of the coil bobbin 2 are inserted into the land corresponding to the connection pattern of the non-ground side output of the oscillation circuit (not shown) in the sensor circuit and the ground pattern 15. The sensor component is blocked by being inserted into the hole 16 and soldered to the coil bobbin 2 by soldering the tip of the coil terminal projecting to the surface side and simultaneously connected to the coil 10. Yes. By connecting the control board 4 and fixing the control board 4 using such coil terminals 9, 9, the assembly workability is improved and the manufacturing cost is reduced. In FIG. 15, 17 indicates solder.

Next, assembly and manufacturing of the sensor device of this embodiment will be briefly described.
First, the coil bobbin 2 is prepared in such a manner that the coil 10 is wound around the winding body 2 a in advance and the wire end of the coil 10 is connected to and fixed to the coil terminal 9, and then the central penetration of the winding body 2 a of the coil bobbin 2 is prepared. While the cylindrical portion 3b of the ferrite core 3 is inserted into the light 13, the flat plate portion 3a of the ferrite core 3 is placed on the concave plane 8 of the flange portion 2c. And this control board 4 is piled up on the collar part 2c so that the back surface may be put on the surrounding wall 8a of the concave plane 8, and the concave plane 8 may be obstruct | occluded. At this time, the coil terminals 9 and 9 are inserted into the insertion holes 16 provided in the control board 4 and protruded to the front surface side, and the protruding portions are soldered and fixed to lands provided on the front surface side of the control board 4. As a result, a sensor block in which the coil bobbin 2, the ferrite 3 and the control board 4 are sequentially stacked is obtained. This sensor block is housed in the body 1 so that the flange 2b of the coil bobbin 2 is placed on the bottom of the body 1. At this time, the projecting tip of the coil terminal 9 projecting toward the body 1 is inserted into the hole 21. The opening periphery of the hole 21 on the bottom surface side of the body 1 protrudes upward as shown in FIG. 5, and the projection 2a is connected to the protrusion 2a side corresponding to the protrusion 21a. A recess 22 is provided so that the position, that is, the positional relationship between the protruding tip of the coil terminal 9 and the hole 21 does not change.

  Now, after the sensor block is housed in the body 1 in this way, a sealing resin 5 such as an epoxy resin or a urethane resin is injected and filled from the opening side of the body 1 and thermally cured to seal the inside of the body 1. Sealed to waterproof structure. Of course, the lead wire 20 connected to the control board 4 is led out of the body 1 at the time of sealing.

  By the way, if the sealing resin 5 does not reach the bottom side of the body 1 sufficiently and a space is generated, bubbles are ejected to the sealing surface at the time of thermosetting, and when cured in that state, the opening is on the opening side of the body 1. Although the bubble mark remains on the exposed sealing surface and looks bad, in this embodiment, since the hole 21 is provided on the bottom surface of the body 1, the sealing resin 5 has not reached the inside of the space formed. The air can be discharged out of the body 1 through the hole 21, and therefore, resin sealing can be performed without leaving bubble marks on the sealing surface (opening side surface of the body 1). That is, the hole 21 becomes an air vent hole.

  Moreover, in this embodiment, since the ferrite core 3 is stored in the concave plane 8 and the concave plane 8 is closed by the control substrate 4, the sealing resin 5 does not flow into the ferrite core 3 side. The ferrite core 3 and the sealing resin 5 or the ferrite core 3 and the coil bobbin 2 having different linear expansion coefficients are not integrated, and the ferrite core 3 is in an environment where thermal expansion and contraction are repeated due to a rapid temperature change. Can be prevented from being damaged.

  When the resin sealing is completed as described above, the sensor device of this embodiment is completed.

  And in the sensor device of the present embodiment, even when a slight impact is applied from the outside during use or installation work, it can be absorbed by the grooves 11 and 12 formed in the coil bobbin 2, An impact is not transmitted to the ferrite core 3 accommodated in the concave plane 8, and the ferrite core 3 can be prevented from being damaged.

  In addition, as shown in FIG. 6, even when the metal object M is actually detected, the static electricity is discharged through the coil terminal 9 on the ground side facing the detection surface through the hole 21 even if the metal object M is charged. The IC 14 connected to the coil 10 is prevented from being broken by electromagnetic induction. That is, the hole 21 also serves as a discharge hole.

  6 schematically shows a high-frequency magnetic flux generated from the carp 10, and β schematically shows an eddy current flowing on the surface of the metal object M by interlinking this magnetic flux α. Detects that the magnetic flux α of the coil 10 is decreased by the generation of the eddy current β and the impedance of the coil 10 is changed, and that the change in impedance causes the oscillation to stop and the amplitude of the high-frequency signal to be applied to the coil 10 to be reduced. Thus, the metal object M is detected.

  In the present embodiment, the annular groove 11 is formed in the concave plane 8 for absorbing the shock, but a plurality of arc-shaped grooves (recesses) formed at predetermined intervals on the circumference as shown in FIG. ) 11 ′ or a plurality of round recesses 11 ″ formed at predetermined intervals on the circumference as shown in FIG. 7B.

(A) is a partially broken perspective view of one embodiment, (b) is an enlarged cross-sectional view taken along the line B-B 'in (a). (A) is a perspective view of one embodiment, (b) is an exploded perspective view of one embodiment, and (c) is a perspective view of a ferrite core. (A) is an enlarged plan view of the coil bobbin used for one embodiment, (b) is an enlarged side view of the coil bobbin used for one embodiment. (A) is a perspective view of the coil bobbin used for one Embodiment, (b) is C-C 'expanded sectional drawing of (a). It is D-D 'expanded sectional drawing of Fig.1 (a). It is an expansion perspective view of the use condition of one Embodiment. (A) is a top view of another example of the coil bobbin used for one embodiment, (b) is a top view of the other example of the coil bobbin used for one embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Body 1a Flange 2 Coil bobbin 2a Winding trunk | drum 2b, 2c collar part 3 Ferrite core 3a Flat plate part 3b Cylindrical part 4 Control board 5 Resin 6 Mounting hole 7 Recessed part 8 Concave plane 8a Circumferential wall 9 Coil terminal 10 Coils 11, 12 Groove 13 Center through hole 14 IC

Claims (5)

In a metal detection sensor that connects a high-frequency oscillation output to a coil to generate a high-frequency magnetic field from the detection surface side and detects a metal object based on a change in oscillation output caused by a change in the impedance of the coil, the bottom surface forms the detection surface A coil-shaped body, a coil wound around the winding drum, a coil bobbin made of synthetic resin disposed on the bottom with one end of the winding drum facing the bottom of the body, and the winding drum A control board that is placed and fixed on the outward end surface of the flange portion with the substrate surface facing the outward end surface of the flange portion integrally provided on the end side and housed in the body, and a central through hole of the winding drum portion A plate-like portion having a plate surface that is integrally coupled to one end of the column-shaped portion and substantially perpendicular to the axis of the column-shaped portion is inserted into the control board and the flange portion. Placed in a closed cavity formed between A metal having a ferrite core and a sealing resin portion filled in the body and sealing the inside of the body, wherein the coil is connected to a sensor circuit mounted on the control board. Detection sensor. The metal detection sensor according to claim 1, wherein the flange portion is provided with an elastic expansion / contraction portion extending and contracting in a direction parallel to the outward end surface and in a direction perpendicular to the end surface. The metal detection sensor according to claim 1, wherein an air vent hole communicating with the inside and the outside is provided in the bottom surface of the body. 4. A part of the ground-side coil terminal of the pair of coil terminals connected to the tip of the coil is provided so as to be visible from the detection surface side of the body. Metal detection sensor. The board surface opposite to the element mounting surface of the control board is provided with an electromagnetic shielding pattern made of conductive metal foil connected to the ground and formed so as to substantially cover the whole board surface. The metal detection sensor according to any one of claims 1 to 4.

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