Magnetizer

Abstract

To provide a magnetizer that reliably magnetizes metallic foreign matter in an inspection target object.SOLUTION: A magnetizer is configured by a yoke and a magnet, and includes a first magnetization member and a second magnetization member that face each other across a conveying path. The first magnetization member has a first head portion and a second head portion that are formed so as to protrude to the conveying path, and the second magnetized member has a third head portion and a fourth head portion that protrude into the conveying path. A magnet is provided on the first head portion, a magnet is provided on the third head portion, the first head portion and the third head portion have different poles facing each other across a first region, and the second head portion and the fourth head portion face each other across a second region that straddles the conveying path on the downstream side of the first region in the conveying direction. A magnetic flux circulates through the first head portion, the third head portion, the fourth head portion, the second head portion, and the first head portion in this order.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a magnetizer for use in a foreign object detection device. [Background technology]

[0002] 2. Description of the Related Art Conventionally, in devices for detecting metallic foreign matter using magnetism, magnetizers that magnetize objects to be inspected have been proposed (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-108554 A Summary of the Invention [Problem to be solved by the invention]

[0004] In such an apparatus, it is required to reliably magnetize metallic foreign bodies in the object to be inspected.

[0005] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide a magnetizer that reliably magnetizes metallic foreign matter in an object to be inspected. [Means for solving the problem]

[0006] In order to solve the above problems, the magnetizer of the present invention comprises: A magnetizer arranged on a conveying path of a workpiece to be subjected to foreign object detection, the magnetizer is composed of a yoke and a magnet, and has a first magnetized member and a second magnetized member that face each other across the conveying path, the first magnetized member is formed with a first head portion and a second head portion protruding toward the transport path, the second magnetized member is formed with a third head portion and a fourth head portion protruding toward the transport path, The first head portion is provided with a magnet, The third head portion is provided with a magnet, The first head portion and the third head portion have different poles facing each other across a first magnetized region, the second head portion and the fourth head portion are opposed to each other across a second magnetized region that straddles the conveying path, downstream of the first magnetized region in a conveying direction, the magnetizer is configured such that magnetic flux circulates from the first head portion to the third head portion, the fourth head portion, the second head portion, and the first head portion in this order; It is characterized by:

[0007] This magnetizer can reliably magnetize metallic foreign matter in the object to be inspected.

[0008] Moreover, the magnetizer described above is The second head portion is provided with a magnet that is smaller than the magnet provided in the first head portion, The fourth head may be provided with a magnet that is smaller than the magnet provided in the third head.

[0009] Moreover, the magnetizer described above is the first magnetized member has a fifth head portion formed on an opposite side to the second head portion with a gap therebetween with respect to the first head portion, the second magnetized member has a sixth head portion formed on an opposite side to the fourth head portion with a gap therebetween with respect to the third head portion, The fifth head portion and the sixth head portion may be opposed to each other across a third magnetized region, on the upstream side in the transport direction from the first magnetized region.

[0010] Moreover, the magnetizer described above is The first magnetized region may be larger than the second magnetized region. Effect of the Invention

[0011] According to the present invention, it is possible to provide a magnetizer that reliably magnetizes metallic foreign matter in an object to be inspected. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view showing a magnetizer 1 of the present embodiment. [Diagram 2] FIG. 2 is a side view showing the magnetizer 1. [Diagram 3] FIG. 2 is a schematic diagram showing the state of magnetic flux assumed in the magnetizer 1. [Figure 4] FIG. 1 is a perspective view showing a conventional magnetizer M. [Diagram 5] 5(a) is a diagram showing the state of magnetic flux assumed in the magnetizer M of FIG. 4 from the front side, and FIG. 5(b) is a diagram showing the state of magnetic flux assumed in the magnetizer 4 of FIG. 4 from the side side. [Figure 6] FIG. 13 is a diagram showing a modified example of the magnetizer 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] [Basic configuration of magnetizer] Hereinafter, an embodiment of the magnetizer will be described with reference to the drawings. Fig. 1 is a perspective view showing the magnetizer 1 of this embodiment provided on the work transport path. Fig. 2 is a side view showing the magnetizer 1 of this embodiment provided on the work transport path. In the following description, the transport direction of the work W may be referred to as the front-rear direction. Also, the width direction of the work W perpendicular to the front-rear direction is referred to as the left-right direction, and the direction perpendicular to both the front-rear direction and the left-right direction is referred to as the up-down direction.

[0014] The magnetizer 1 of this embodiment is for magnetizing metallic foreign matter mixed in a sheet-like workpiece W, and has an upper part 11 (corresponding to an example of a first magnetizing member) and a lower part 12 (corresponding to an example of a second magnetizing member) arranged at positions sandwiching the conveying path of the workpiece W. When the metallic foreign matter in the workpiece W is magnetized by this magnetizer 1, the magnetized metallic foreign matter is detected by a magnetic sensor (not shown) provided downstream in the conveying direction. The workpiece W is made of a non-magnetic material (e.g., polyethylene, nonwoven fabric) that does not become magnetized. The upper part 11 and the lower part 12 are composed of a magnet and a yoke, as described later. For the magnetizer 1, magnets made of various materials such as electromagnets and neodymium magnets (e.g., N50, N48) can be used. In addition, as the material of the yoke, it is preferable to use a material with a relatively high saturation magnetic flux density and high magnetic permeability, such as pure iron, stainless steel (e.g., SUS430), or permendur.

[0015] 2, the upper portion 11 has a configuration in which a magnet is provided on an L-shaped yoke 110 that serves as a base. The upper portion 11 is formed with a first head portion 111 that protrudes toward the transport path, and a second head portion 112 that protrudes downstream in the transport direction from the first head portion 111. Of these, the first head portion 111 is provided with a magnet, and the second head portion 112 is a yoke.

[0016] 2, the lower portion 12 has a configuration in which a magnet is provided on an L-shaped yoke 120 that serves as a base. The lower portion 12 is formed with a third head portion 121 that protrudes toward the transport path, and a fourth head portion 122 that protrudes downstream in the transport direction from the third head portion 121. Of these, the third head portion 121 is provided with a magnet, and the fourth head portion 122 is a yoke.

[0017] The first head unit 111 of the upper part 11 and the third head unit 121 of the lower part 12 are disposed in positions where their different poles face each other across the transport path. The second head unit 112 of the upper part 11 and the fourth head unit 122 of the lower part 12 are disposed in positions where they face each other across the transport path. In this embodiment, the N pole of the first head unit 111 and the S pole of the third head unit 121 face each other. These polarities may be reversed.

[0018] [Magnetizing effect by magnetizer 1] Hereinafter, the magnetic field generated in the magnetizer 1 will be described with reference to Fig. 3. Fig. 3 is a schematic side view showing the state of magnetic flux assumed in the magnetizer 1. In Fig. 3, the magnetic flux lines assumed in the magnetizer 1 are indicated by arrows on the side view of the magnetizer 1 shown in Fig. 2.

[0019] In the magnetizer 1 of this embodiment, the magnets provided in the first head portion 111 and the third head portion 121 generate a magnetic flux that circulates from the first head portion 111 through the third head portion 121, the fourth head portion 122, the second head portion 112, and then back to the first head portion 111.

[0020] The first head portion 111 and the third head portion 121 are positioned opposite to each other across the transport path, and any metallic foreign matter inside the workpiece W passing between them is magnetized by the magnetic field between these head portions. Hereinafter, the region on the transport path for the workpiece W that is sandwiched between the first head portion 111 and the third head portion 121 is referred to as a first magnetized region MA1 (corresponding to an example of the first region).

[0021] The second head portion 112 and the fourth head portion 122 are positioned opposite to each other across the transport path, and any metallic foreign matter inside the workpiece W passing between them is magnetized by the magnetic field between these head portions. Hereinafter, in the transport path for the workpiece W, the region sandwiched between the second head portion 112 and the fourth head portion 122 is referred to as a second magnetized region MA2 (corresponding to an example of the second region).

[0022] As shown by the arrows in FIG. 3, the direction of the magnetic field generated in the first magnetization region MA1 is opposite to the direction of the magnetic field generated in the second magnetization region MA2. Also, in FIG. 3, the dotted arrow indicates that a weak magnetic field in the opposite direction to that of the first magnetization region MA1 is generated upstream of the first magnetization region MA1 in the conveying direction. That is, in the magnetizer 1, the workpiece W is magnetized by an upward magnetic field, then by a downward magnetic field in the first magnetization region MA1, and finally by an upward magnetic field in the second magnetization region MA2. Before magnetization in the second magnetization region MA2, the workpiece W is magnetized by a magnetic field in the opposite direction in the first magnetization region MA1. However, if the strength of the magnetic field in the second magnetization region MA2 is sufficient, the metal foreign object in the workpiece W can be magnetized even if it is magnetized by a magnetic field in the opposite direction in the first magnetization region MA1.

[0023] [Differences from conventional magnetizers] An example of a conventional magnetizer will be described below with reference to the drawings. Fig. 4 is a perspective view showing magnetizer M, which is an example of a conventional magnetizer provided on a workpiece transport path. Fig. 5(a) is a front schematic view showing the state of magnetic flux assumed in magnetizer M, and Fig. 5(b) is a side schematic view showing the state of magnetic flux assumed in magnetizer M.

[0024] The conventional magnetizer M shown in Fig. 4 has two magnets MG1 and MG2 arranged on either side of the transport path inside a yoke YO that surrounds the transport path for the workpiece W. In the magnetizer M, as shown in Fig. 5(a), a magnetic flux is generated that circulates from the upper magnet MG1 through the lower MG2, then through the yoke YO to the upper magnet MG1 again. In this magnetizer M, when the workpiece W passes between the two magnets MG1 and MG2, it is magnetized by the downward magnetic field between these magnets MG1 and MG2.

[0025] When two magnets MG1 and MG2 are arranged as in the magnetizer M, not only is there a magnetic field between these magnets, but also a magnetic field in the opposite direction that circulates around the outside of the magnets MG1 and MG2, as shown by the dotted arrow in Figure 5(a). The yoke YO of the magnetizer M serves as a path for this magnetic field circulating around the outside, suppressing the effect of the opposite magnetic field on the workpiece W.

[0026] However, the magnetic field circulating around the outside is also generated in the front-to-back direction as shown by the dotted arrow in Figure 5(b). Because this magnetic field is generated on the transport path, the workpiece W that has been magnetized by the downward magnetic field between magnets MG1 and MG2 will end up being magnetized by the magnetic field in the opposite direction (upward). This causes the magnetization of a metallic foreign object that was once magnetized to weaken, or in some cases, to become weakly magnetized in the opposite direction, which reduces the gain obtained by the magnetic sensor and causes the metallic foreign object to be overlooked.

[0027] The magnetizer 1 of this embodiment uses a yoke adjacent to the magnets to induce a magnetic field to the second magnetization region MA2, and utilizes the magnetic field (second magnetization region MA2) that rotates around the outside of the two magnets for final magnetization. In this embodiment, the direction of the magnetic field changes between the first magnetization region MA1 and the second magnetization region MA2, but after the second magnetization region MA2, the magnetic field merely attenuates and the direction of the magnetic field does not change. Therefore, after the final magnetization, the magnet is not further magnetized by a magnetic field in the opposite direction, and the above-mentioned problems can be prevented.

[0028] [Other applicable configurations] In the magnetizer 1, of the magnetic fields generated by the first head portion 111 and the third head portion 121, the magnetic field (second magnetizing region MA2) circulating on the outer side is used for final magnetization.

[0029] 6(a), for example, a configuration may be adopted in which magnets (sub-magnets) smaller than the magnets (main magnets) of the first head portion 111 and the third head portion 121 are provided in the second head portion 112 and the fourth head portion 122. By appropriately setting the volume ratio of these main magnets to the sub-magnets (for example, 3:1 to 3:2), it is possible to increase the magnetic flux density of the second head portion 112 and the fourth head portion 122 while preventing the generation of a magnetic field in the opposite direction (downward in FIG. 3) on the downstream side of the second magnetization region MA2.

[0030] Also, for example, as shown in Figure 6 (b), head portions 113, 123 may be formed separately facing the transport path on the upstream side of the transport direction, and a magnetic field circulating around the outside of the magnetic field generated by the magnets of the first head portion 111 and the third head portion 121 may be generated between these head portions.

[0031] It is preferable to generate a stronger magnetic field in the second magnetization region MA2 in the magnetizer 1. For example, by making the area of ​​the second magnetization region MA2 narrower than that of the first magnetization region MA1, the magnetic flux density can be made higher than that of the first magnetization region MA1.

[0032] Since the first magnetization region MA1 is not used for final magnetization, it may be, for example, a region where only a part of the workpiece W is magnetized (does not cross the conveying path), or may be a region that includes a region (outside the conveying path) where the workpiece W is not magnetized. When the second magnetization region MA2 is used for final magnetization, it is sufficient that the first magnetization region MA1 is provided upstream of the second magnetization region MA2 in the conveying direction. [Explanation of symbols]

[0033] 1 Magnetizer 11 Top 12 Lower 110, 120 York 111 First head part 112 Second head part 121 Third Head 122 Fourth Head

Claims

1. A magnetizer arranged on a conveying path of a workpiece to be subjected to foreign object detection, the magnetizer is composed of a yoke and a magnet, and has a first magnetized member and a second magnetized member that face each other across the conveying path, the first magnetized member is formed with a first head portion and a second head portion protruding toward the transport path, the second magnetized member is formed with a third head portion and a fourth head portion protruding toward the transport path, The first head portion is provided with a magnet, The third head portion is provided with a magnet, The first head portion and the third head portion have different poles facing each other across a first region, the second head unit and the fourth head unit are opposed to each other across a second region that straddles the transport path, the second head unit and the fourth head unit being located downstream in a transport direction from the first region; the magnetizer is configured such that magnetic flux circulates from the first head portion to the third head portion, the fourth head portion, the second head portion, and the first head portion in this order; A magnetizer characterized by:

2. The magnetizer according to claim 1, The second head portion is provided with a magnet that is smaller than the magnet provided in the first head portion, The fourth head portion is provided with a magnet smaller than the magnet provided in the third head portion. A magnetizer characterized by:

3. The magnetizer according to claim 1 or 2, the first magnetized member has a fifth head portion formed on an opposite side to the second head portion with a gap therebetween with respect to the first head portion, the second magnetized member has a sixth head portion formed on an opposite side to the fourth head portion with a gap therebetween with respect to the third head portion, the fifth head portion and the sixth head portion are opposed to each other across a third region, on the upstream side of the first region in the transport direction; A magnetizer characterized by:

4. The magnetizer according to claim 1 or 2, The first region is larger than the second region. A magnetizer characterized by:

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