JP5341642B2 - Integrated plastic magnet - Google Patents

Description

The present invention, connection portions about the integral plastic magnet.

  Magnets are widely used for non-contact switches, motors and the like. For example, the non-contact switch shown in Patent Document 1 has a magnetic sensor arranged in the vicinity of a magnet. The magnetic sensor detects the proximity and separation of a magnetic material that is a detection target through a change in the magnetic field of the magnet. The non-contact switch is turned on / off based on the detection result of the magnetic sensor. In many cases, the magnet is formed in a different shape such as a U shape or a U shape so that a change in the magnetic field can be easily detected by a magnetic sensor. As described above, the magnet is formed into various shapes according to its use and necessity. As the magnet, a plastic magnet (hereinafter referred to as a plastic magnet) obtained by mixing magnetic powder with plastic is widely used because of its high moldability.

JP 2008-21524 A

  By the way, when forming the magnet of the said patent document 1 with a plastic magnet, the molten liquid which mixes magnetic powder with a plastics is inject | emitted in the cavity in a metal mold | die, and it shape | molds. That is, the plastic mug can be formed in a shape corresponding to the shape of the cavity of the mold. Here, the plastic mug formed by solidifying the melt is hard and has low flexibility. For this reason, it is difficult to change the shape after injection molding of the plastic mug, and it is necessary to change the shape of the mold itself when it is desired to form a plastic mug having a different shape.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a connecting part integrated plastic magnet having a high degree of freedom in molding.

Hereinafter, means for achieving the above-described object and its operation and effects will be described.
The invention according to claim 1 is formed of a plastic magnet, a pair of magnet portions that are magnetic poles, and a connection portion that is formed of a plastically deformable material and connects between the pair of magnet portions, The connecting portion is plastically deformed in a manner that includes the magnetic sensor so that a magnetic sensor that detects a magnetic field from the magnet portion is sandwiched and held by the pair of magnet portions. This is the gist.

According to this configuration, the connecting part-integrated plastic magnet is formed by connecting each magnet part to the connecting part. Here, the connecting portion is provided so as to be plastically deformable, and the connecting portion integrated plastic magnet can be formed into a desired shape by bending the connecting portion. Thereby, the freedom degree of shaping | molding of a connection part integrated plastic magnet increases.
Further, the connecting portion is bent so as to hold the magnetic sensor so as to hold the magnetic sensor. Accordingly, it is not necessary to fix the magnetic sensor to the connecting portion integrated plastic magnet with an adhesive or to form the connecting portion integrated plastic magnet and the magnetic sensor integrally.

The gist of the invention described in claim 2 is that, in the plastic magnet integrated with the connecting portion according to claim 1, the connecting portion is made of a soft magnetic material.
According to the configuration, the leakage of magnetic flux passing through the connection portion can be suppressed by forming the connection portion with a soft magnetic material. Thereby, the magnetic characteristics of the plastic magnet integrated with the connecting portion are improved.

According to the present invention, it is possible in plastic magnet to provide a plastic magnet having a high degree of freedom in forming connecting portion integral.

The top view of the yoke frame in this embodiment. Sectional drawing of the metal mold | die which shape | molds the magnet part in this embodiment. The top view of the yoke frame in the state by which the magnet part in this embodiment was shape | molded. The top view of the plastic mug after the cutting | disconnection in this embodiment. The side view of the plastic mug after the cutting | disconnection in this embodiment. The side view of the plastic mug after the bending process in this embodiment. The schematic diagram of a proximity switch in the state where the magnetic body in this embodiment separated. The schematic diagram of the plastic mug magnetized by the magnetizing coil in this embodiment. The schematic diagram of a proximity switch in the state where the magnetic body in this embodiment approached. The top view of the plastic mug in other embodiment. The top view of the plastic mug in other embodiment.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which a connecting part integrated plastic magnet according to the present invention (hereinafter abbreviated as a plastic magnet) is embodied as a proximity switch will be described below with reference to FIGS.

First, the proximity switch 2 will be briefly described with reference to FIG.
The proximity switch 2 includes a U-shaped plastic magnet 5 that generates a bipolar magnetic field (a magnetic field), a magnetic sensor 30 that detects a change in the magnetic field, and a magnetic sensor 30 that approaches and moves away from the magnetic sensor 30. And a magnetic body 19 that causes a change.

  The magnetic sensor 30 installed inside the plastic magnet 5 detects the approach of the magnetic body 19 through a change in the magnetic field. Precisely, the magnetic sensor 30 outputs a voltage corresponding to the magnetic field. Whether the proximity switch 2 is on or off is determined based on whether or not the output voltage of the magnetic sensor 30 exceeds a predetermined threshold value. The magnetic sensor 30 includes a Hall element, an MR (magnetoresistive) element, etc., but may be any type as long as it can detect a change in the magnetic field.

Next, a manufacturing method of the plastic mug 5 provided in the proximity switch 2 will be described.
As shown in FIG. 1, when forming the plastic mug 5, the yoke frame 10 is formed with a metal such as soft iron, which is a soft magnetic material. The yoke frame 10 is integrally formed with a U-shaped frame portion 11 that opens downward and a yoke portion 12 that extends in a direction perpendicular to the opening direction. A plurality of yoke portions 12 (four in this example) are provided with a constant interval in the opening direction.

  Each yoke part 12 is formed with a molding part 14 extending in a direction perpendicular to itself. A pair of forming portions 14 are provided at positions serving as a reference in the extending direction of the yoke portion 12. A belt-like bent portion 16 is formed between the molding portions 14 of each yoke portion 12.

  A rectangular magnet portion 20 is injection-molded in the molding portion 14 as indicated by a two-dot chain line in FIG. The magnet unit 20 is formed of a plastic magnet formed by mixing magnetic powder into a resin such as plastic. A plastic magnet is superior to a sintered magnet in that it can be formed into a desired shape by injection molding.

  Specifically, as shown in FIG. 2, the pair of molds 25 and 26 that form the magnet portion 20 are displaced in a direction perpendicular to the surface in which the molding portion 14 is orthogonal to the extending direction of the yoke portion 12. . When both molds 25 and 26 are in contact with each other, a cavity 27 (space) that encloses the molded portion 14 is formed inside thereof. Then, a melt obtained by melting the raw material of the plastic magnet with heat is injected into the cavity 27 through a hot water passage 28 formed on the side of the mold 26. As the melt filled in the cavity 27 is cooled and solidified, the magnet portion 20 is formed integrally with the yoke portion 12 as shown in FIG. In this way, by forming the magnet part 20 on the outer periphery of the forming part 14 orthogonal to the extending direction of the yoke part 12, the forming part 14 functions to prevent the magnet part 20 from coming off. At this time, the magnet unit 20 is not magnetized and is not magnetized.

  Next, the frame part 11 side of the yoke part 12 is cut. Precisely, the yoke portion 12 is cut so as to form the same surface as the side surface of the magnet portion 20 on the frame portion 11 side. As a result, as shown in FIG. 4, the plastic magnet 5 is formed in which both the magnet portions 20 are connected via the yoke portion 12, mainly the bending portion 16.

  As described above, the yoke frame 10 including the bent portion 16 is formed of a metal that can be plastically deformed. Further, as shown in FIG. 5, the bending portion 16 that connects both the magnet portions 20 is formed in a rod shape, more precisely, a long plate shape. For this reason, the bending part 16 can be bent, and the plastic mug 5 can be made into a desired shape. In the present embodiment, as shown in FIG. 6, the bending portion 16 is bent at two right angles at equal intervals in the extending direction of the bending portion 16 in a manner in which the magnet portion 20 is approached. Thereby, the bending part 16 and by extension the plamag 5 are shape | molded in U shape.

  Next, as shown in FIG. 7, the magnetic sensor 30 is assembled to the plastic magnet 5. The magnetic sensor 30 is covered and sealed with a casing 31 made of, for example, epoxy resin (thermosetting resin). In the present embodiment, as shown in FIG. 7, the housing 31 is sandwiched and held between the magnet portions 20. In this way, by bending the bending portion 16, the plastic magnet 5 can be formed into a desired shape, and the magnetic sensor 30 can be assembled to the plastic magnet 5.

  Next, the magnet unit 20 is magnetized through magnetization of the magnet unit 20. As shown in FIG. 8, magnetization is performed by a magnetic field generated by a magnetizing coil 33 formed by winding a conducting wire, for example. A pulse current is passed through the magnetizing coil 33, and a magnetic field is formed accordingly. The opposite side of both magnet portions 20 of the plastic magnet 5 is brought close to one end side (the side from which magnetic flux goes out) of the magnetizing coil 33. Thereby, the plastic magnet 5 has the same magnetic flux direction as the magnetic flux direction of the magnetic field formed by the magnetizing coil 33. That is, both the magnet parts 20 become N poles, and the yoke part 12 on the opposite side of both magnet parts 20 becomes S poles. The magnets 5 may be magnetized using a method of magnetizing with a static magnetic field. The plastic magnet 5 is completed by this magnetization.

  The plamag 5 is formed by interposing a yoke portion 12 (mainly a bent portion 16) made of metal between the magnet portions 20. Here, the metal material is cheaper than the plastic magnet material. For this reason, compared with the plastic mug which shape | molded the whole with the plastic magnet material, the usage-amount of a plastic magnet material can be reduced and the price of the plastic magnet 5 can be held down. As described above, the configuration in which the yoke portion 12, which is not a magnet, is interposed between the magnet portions 20, the magnetic field (magnetic flux density) necessary for the function of the proximity switch 2 can be obtained by the both magnet portions 20. In addition, as described later, the performance of the plastic mug 5 and thus the proximity switch 2 can be improved. Further, since the metal is more elastic than the plastic magnet and is less likely to be chipped, the durability of the plastic magnet 5 can be improved.

Next, the characteristics of the magnetized plastic mug 5 will be described.
In FIG. 7, the magnetic body 19 is sufficiently separated so that the magnetic effect is not exerted on the plastic magnet 5. In this state, the magnetic flux of the plastic magnet 5 passes from both N-pole magnet portions 20 through the outside and inside of the plastic magnet 5 to the yoke portion 12 on the S-pole side. Then, the magnetic flux returns to the magnet unit 20 through the yoke unit 12. Here, the yoke portion 12 formed of a soft magnetic material has less magnetic flux leaking to the outside than a magnet such as a plastic magnet. For this reason, for example, the magnetic flux density in the vicinity of both magnet portions 20 can be increased as compared with a plastic magnet formed entirely with plastic magnets. Here, the magnetic flux density is the surface density of the magnetic flux per unit area. Further, when the magnetic flux density is improved, the diffusion of the magnetic flux of the plastic magnet 5 is also suppressed. The improvement in the magnetic flux density of the plastic magnet 5 as described above contributes to the improvement in detection accuracy of the proximity switch 2. Therefore, by passing the yoke portion 12 through the magnet portion 20, it is possible to improve the characteristics of the plastic magnet 5 itself and improve the performance of the proximity switch 2.

Next, the operation mode of the proximity switch 2 will be described.
As described above, the proximity switch 2 is configured by combining the magnetic body 19 with the plastic magnet 5 including the magnetic sensor 30. The magnetic flux from the magnetic body 19 side of the two magnet portions 20 passes through both sides of the plamag 5 in the state of being sufficiently separated so as not to exert a magnetic influence on the plastic magnet 5 shown in FIG. Head to 12. The magnetic sensor 30 outputs a voltage corresponding to the inner magnetic flux of the plastic magnet 5. In this state, the output voltage of the magnetic sensor 30 exceeds a predetermined threshold value, and the switch is turned on.

  Further, as shown in FIG. 9, when the magnetic body 19 approaches the magnet section 20 side of the plastic magnet 5, the magnetic flux from both the magnet sections 20 that are N poles goes to the magnetic body 19. Accordingly, the magnetic flux detected by the magnetic sensor 30 in the state of FIG. 7 is not sufficiently detected. That is, the output voltage of the magnetic sensor 30 becomes a predetermined threshold value or less, and the switch is turned off.

As described above, according to the embodiment described above, the following effects can be obtained.
(1) The plastic magnet 5 is formed by connecting both the magnet portions 20 to the yoke portion 12. Here, the yoke portion 12 is provided so as to be plastically deformable, but by bending the yoke portion 12, the plastic magnet 5 can be formed into a desired shape. Thereby, the freedom degree of shaping | molding of the plastic mug 5 increases.

(2) By forming the yoke portion 12 from a metal that is a soft magnetic material, leakage of magnetic flux passing through the yoke portion 12 can be suppressed. Thereby, the magnetic characteristics of the plastic mug 5 are improved.
(3) The yoke portion 12 is bent so as to hold the housing 31 containing the magnetic sensor 30 so as to hold the magnetic sensor 30. Accordingly, the magnetic sensor 30 is held by the magnet unit 20 via the housing 31. Therefore, it is not necessary to fix the magnetic sensor 30 to the plastic magnet 5 with an adhesive or to newly form the plastic magnet 5 and the magnetic sensor so as to be integrated.

  (4) The plastic magnet 5 can be formed into a desired shape by the step of injection-forming a plurality of magnet portions 20 on the rod-shaped yoke portion 12 and bending the yoke portion 12. Here, the bar shape means various bar shapes such as a columnar bar and a plate bar.

In addition, the said embodiment can be implemented with the following forms which changed this suitably.
In the above embodiment, the bending portion 16 is bent and magnetized after the housing 31 and the magnetic sensor 30 are installed. However, the timing of magnetization is not limited to this. That is, as shown in FIG. 4, the linear plastic magnet 5 before the bending portion 16 is bent may be magnetized. In this case, the magnets 33 are brought close to one end side of the magnetizing coil 33 so that the plastic magnet 5 is along the magnetic flux direction of the magnetizing coil 33. Thereby, one magnet part 20 becomes a south pole, and the other magnet part 20 becomes a north pole. Thereafter, by bending the bent portion 16 into a U shape, as shown in FIG. 10, a U-shaped plamag 5 having N and S poles at both ends is formed. Even in this case, leakage of magnetic flux from the magnet part 20 on the N pole side to the magnet part 20 on the S pole side via the yoke part 12 is suppressed, and the magnetic characteristics of the plastic magnet 5 are improved.

  In the above embodiment, the magnetic sensor 30 is sandwiched and held by the magnet portion 20 of the U-shaped plastic mug 5 via the housing 31. However, a case (not shown) may be injection-molded so as to seal the outer periphery of the plastic mug 5 in a state where the casing 31 is positioned in the plastic mug 5. Thereby, the magnetic sensor 30 becomes completely integrated with the plastic magnet 5. At this time, since the casing 31 is an epoxy resin having excellent heat resistance, the casing 31 is not melted by the heat of the melt that is a raw material of the case when the case is injection molded.

  Alternatively, the magnetic sensor 30 may be installed directly in the U-shaped plastic mug 5 without being covered with the casing 31. In this case, similarly to the above, the magnetic sensor 30 can be formed integrally with the plastic mug 5 by molding a case (not shown) so as to seal the outer periphery of the plastic mug 5. In this case, there is no need to mold the casing 31.

  In the above embodiment, the U-shaped plamag 5 is formed by bending the bent portion 16 into a U-shape. However, the bending method of the bending part 16 is not limited to this. For example, as shown in FIG. 11, the bent portion 16 may be formed in a circular shape. Even in this case, the magnetic flux passes from the magnet part 20 on the N pole side to the magnet part 20 on the S pole side via the yoke part 12. For this reason, the magnetic flux leakage is suppressed and the magnetic characteristics of the plastic magnet 5 are improved.

  In the above embodiment, two magnet portions 20 are formed in each yoke portion 12, but three or more magnet portions 20 may be formed in the yoke portion 12. Thereby, the plastic mug 5 of a more various structure can be shape | molded. For example, N-pole and S-pole magnet portions 20 are formed continuously and alternately on a single yoke portion 12, and the yoke portion 12 is bent into a circle. Thereby, the plastic mug 5 which can be used for a rotary motor can be shape | molded.

  In the above embodiment, the magnetic sensor 30 is held by the plastic magnet 5 via the housing 31, but the magnetic sensor 30 may not be held by the plastic magnet 5. That is, the magnetic sensor 30 may be fixed to the plastic mug 5 or may be located away from the plastic magnet 5. When the magnetic sensor 30 is located away from the plastic magnet 5, the plastic magnet 5 and the magnetic sensor 30 can be integrated by forming a resin case that surrounds the plastic magnet 5 and the outside of the magnetic sensor 30.

-In above-mentioned embodiment, although the bending part 16 was formed in plate shape, the shape of the bending part 16 is not limited to this, For example, a cylindrical shape may be sufficient.
In the above embodiment, the yoke portion 12 is formed of a metal that is a soft magnetic material. However, the yoke portion 12 may be formed of a plastically deformable material other than the soft magnetic material. In this case, the yoke portion 12 functions as the yoke portion 12 that couples both the magnet portions 20, and the plastic magnet 5 can be molded with a high degree of freedom by plastic deformation.

  In the above embodiment, the bending portion 16 is bent after the yoke portion 12 is cut when the plastic magnet 5 is formed. However, cutting and bending may be performed simultaneously by using, for example, a press machine.

Next, the technical idea that can be grasped from the embodiment will be described together with the effects.
(B) in a manner surrounding a plurality of said connecting portion disposed every a constant distance, these same connecting portion and the frame-shaped frame which is integrally formed is provided, the connection between the frame a magnet portion after injection A method of manufacturing a plastic magnet integrated with a connecting part that is separated from the part.

  According to the same configuration, a plurality of connecting part integrated plastic magnets can be formed in one frame by continuously injection-molding the magnet part to a plurality of connecting parts formed integrally with the frame. it can.

  DESCRIPTION OF SYMBOLS 2 ... Proximity switch, 5 ... Plamag (plamag with integral connection part), 10 ... Yoke frame, 11 ... Frame part, 12 ... Yoke part (connection part), 14 ... Molding part, 16 ... Bending part, 19 ... Magnetic body , 20 ... magnet part, 30 ... magnetic sensor, 31 ... housing, 33 ... magnetized coil.

Claims (2)

A pair of magnet portions that are formed of plastic magnets and serve as magnetic poles;
And is formed of a plastically deformable material, and includes a connecting portion that connects between the pair of magnet portions ,
The connecting portion is of a connecting portion integrated type that is plastically deformed in a manner that includes the magnetic sensor so that a magnetic sensor that detects a magnetic field from the magnet portion is sandwiched and held by the pair of magnet portions. Plastic magnet. The plastic part-integrated magnet according to claim 1,
The connecting portion is a plastic magnet integrated with a connecting portion made of a soft magnetic material.

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