JP2012088126A - Flaw inspection method and flaw inspection device of magnetic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flaw inspection method and a flaw inspection device of a magnetic component, capable of certainly carrying out total number inspection about the presence/absence of a flaw of the magnetic component, and enabling in-lining.SOLUTION: A flaw inspection device 1 comprises a magnetic holder 10, an induction coil 20, magnetization characteristic measuring means 30, and discriminating means 40. A magnetic component 100 is attached to a magnetic holder 10, and the magnetic holder 10 is combined with the magnetic component 100 to form a closed magnetic circuit. The induction coil 20 applies a magnetic field on the closed magnetic circuit. The magnetic characteristic measuring means 30 measures the magnetization characteristics of the closed magnetic circuit when the magnetic field is applied on the closed magnetic circuit. The discriminating means 40 obtains the measured magnetization characteristics of the closed magnetic circuit from the magnetization characteristic measuring means 30, and discriminates the presence/absence of a flaw of the magnetic component 100 on the basis of the measured magnetization characteristics.

Description

  The present invention relates to a scratch inspection method and a scratch inspection apparatus for magnetic parts. In particular, in the inspection process of magnetic parts, it is possible to reliably inspect in a short time all the presence or absence of scratches (cracks) generated in the manufacturing process of magnetic parts, and the inspecting method and scratches of magnetic parts that can be inlined It relates to an inspection device.

  Conventionally, magnetic parts made of a magnetic material (sometimes referred to as “iron core”, “magnetic core”, and “core”) are used as parts constituting a choke coil, a solenoid valve, and the like. As magnetic parts, those using a ferrite material and those using a dust core in which the surface of a metal magnetic powder is insulated and pressed are known.

  The above-described magnetic component can be mass-produced with a mold, and is usually manufactured by molding into a target shape with a mold. Recently, there is a small one that is integrally formed into a complicated shape. In addition, the “complex shape” here is not a simple shape such as a plate shape, a column shape (bar shape), or a cylinder shape, for example, a shape having a bent portion, a shape having a convex portion or a concave portion, an opening portion, It refers to a so-called three-dimensional shape such as a container shape having a side wall portion and a bottom wall portion.

  The manufactured magnetic component is subjected to flaw detection inspection for inspecting the presence or absence of scratches (cracks) in the final inspection process. From the viewpoint of quality assurance, the flaw detection inspection is preferably a non-destructive inspection. Typical methods for flaw detection inspection on magnetic parts include “eddy current flaw detection method” (for example, refer to Patent Document 1), “ultrasonic flaw detection method” (for example, refer to Patent Document 2), and “magnetic particle flaw detection method” (for example, (See Patent Document 3).

Japanese Patent Laid-Open No. 2002-350406 JP 2004-138392 A JP-A-11-223610

  However, the conventional method for inspecting scratches on magnetic parts has the following problems.

  In the eddy current flaw detection method, an eddy current is generated on the surface of a magnetic component to be inspected, a change in the eddy current is detected, and the presence or absence of a flaw is inspected. This method is easy to handle, can be inspected in a short time, and can be easily inlined. However, since eddy currents flow only on the surface of the magnetic component to be inspected, the inspection range is limited to the vicinity of the surface and is not suitable for detecting internal flaws. That is, with this method, there is a problem that the presence or absence of scratches present inside the magnetic component cannot be reliably detected.

  In the ultrasonic flaw detection method, flaws existing inside are detected by using reflection of ultrasonic waves. Specifically, a transmitting probe that receives ultrasonic waves and a receiving probe that receives ultrasonic waves are arranged on the surface of the magnetic component to be inspected, and the ultrasonic waves incident from the transmitting probe are defective on the surface and inside. The time difference between the reflection and the arrival at the receiving probe is measured, and the presence or absence of scratches is inspected. This method can inspect the inside of the magnetic component. However, since it is indispensable to immerse a magnetic component in a solvent solution for flaw detection for a highly accurate inspection, the configuration becomes complicated and unsuitable for in-line implementation. Moreover, in the magnetic component using the ferrite material or the dust core, there is a concern that the detection sensitivity is remarkably lowered because the powder particle interface exists and the reflection of the ultrasonic wave at the particle interface acts as noise.

  In the magnetic particle flaw detection method, a magnetic component to be inspected is magnetized, magnetic powder is adhered, and the presence or absence of a flaw is inspected by observing a change in the adhered magnetic powder pattern. This method is complicated in configuration, and requires labor, time, and cost, so that 100% inspection is difficult. In addition, in the case of a magnetic part integrally molded into a complicated shape, there is a tendency that a part corresponding to a joint is likely to be damaged in manufacturing. However, when observing a magnetic powder pattern, this part is easily hidden and easily overlooked.

  The present invention has been made in view of the above circumstances, and one of its purposes is to provide a magnetic component capable of inspecting all the presence or absence of scratches on a magnetic component in a short time and capable of being inlined. It is to provide a wound inspection method and a wound inspection apparatus.

The method for inspecting a flaw of a magnetic component according to the present invention is a method for inspecting a flaw of a magnetic component made of a magnetic material, and includes the following steps.
A process of attaching a magnetic component to be inspected to a magnetic holder made of a magnetic material and forming a closed magnetic path with the magnetic component and the magnetic holder.
A step of applying a magnetic field to the closed magnetic path and measuring the magnetization characteristics.
A step of determining the presence or absence of scratches on the magnetic component based on the measured magnetization characteristics.

  A scratch inspection apparatus for magnetic parts according to the present invention is an apparatus for inspecting the presence or absence of scratches on a magnetic part made of a magnetic material, and includes a magnetic holder, an induction coil, magnetization characteristic measurement means, and discrimination means. Features. The magnetic holder is attached with a magnetic component to be inspected and is combined with the magnetic component to form a closed magnetic path. The induction coil applies a magnetic field to the closed magnetic circuit. The magnetization characteristic measuring means measures the magnetization characteristic of the closed magnetic circuit. The discriminating unit discriminates the presence or absence of a scratch on the magnetic component based on the measured magnetization characteristics.

  According to the scratch inspection method and the scratch inspection apparatus for a magnetic component of the present invention, the magnetic component is attached to the magnetic holder, the closed magnetic circuit is formed, the magnetization characteristic of the closed magnetic circuit is measured, and the magnetic component is based on the measured magnetization characteristic. The presence or absence of scratches can be determined. With a simple configuration for measuring the magnetization characteristics, the presence or absence of scratches can be inspected, and inspection in a short time is possible, which is suitable for 100% inspection. Moreover, it can be realized at low cost, and the inspection process can be automated and inlined. Furthermore, it is possible to reliably detect the presence or absence of scratches on the surface and inside of the magnetic component, and it is possible to deal with magnetic components of simple shapes to complex shapes.

  The present invention utilizes the fact that the magnetization characteristics of the magnetic component (closed magnetic path) change depending on the presence or absence of scratches on the magnetic component. Whether or not the magnetic component is scratched is determined by comparing the reference magnetization characteristic (reference value) with the measured magnetization characteristic (measured value). It is possible to determine whether the product is a good product without a scratch. For example, the reference magnetization characteristics may be determined based on the magnetization characteristics when a non-defective non-defective product is used, or determined based on the theoretical magnetization characteristics calculated from the design data of the magnetic component. The “magnetization characteristics” referred to here are, for example, a magnetization curve (BH curve) showing the relationship between the magnetic field (H) and the magnetic flux density (B), permeability (μ) (specific example, maximum permeability). Magnetic permeability (μm), initial permeability (μi, etc.), magnetic flux density when a certain magnetic field is applied (specific example, magnetic flux density B50 when applying a magnetic field of 50 Oersted (Oe), magnetic field of 100 Oersted (Oe) Is a magnetic flux density B100). The magnetic permeability (μ) can be obtained by determining the slope of the magnetization curve. Since the magnetization characteristics serve as an index for determining the presence or absence of a flaw, it is desirable that the change be large depending on the presence or absence of a flaw (that is, a difference easily occurs between a reference value and a measured value). For example, the maximum magnetic permeability (μm) It is preferable to select

  The magnetic holder is not particularly limited as long as it is made of a magnetic material like the magnetic component and forms a closed magnetic path by being combined with the magnetic component. The magnetic holder is preferably formed of a material having a magnetic property equivalent to or higher than that of the magnetic component (for example, magnetic permeability, saturation magnetic flux density, etc.), for example, formed of the same material as the magnetic component.

  As one form of the flaw inspection method of the present invention, a gap member made of a non-magnetic material is disposed on the mounting surface of a magnetic holder to which a magnetic component is mounted.

  As one form of the flaw inspection apparatus of this invention, providing the gap member which consists of a nonmagnetic material arrange | positioned at the attachment surface of the magnetic holder in which a magnetic component is attached is mentioned.

  The magnetization characteristics of the closed magnetic circuit also change depending on the size of the gap existing in the closed magnetic circuit. When a magnetic part is directly attached to the magnetic holder, the mounting state (contact state) between the magnetic part and the magnetic holder changes due to variations in manufacturing of the magnetic part, and an inevitable unintended gap between the two. If there is a gap due to this gap in the closed magnetic circuit, the measured magnetization characteristics are affected. According to the above configuration, when the magnetic component is attached to the magnetic holder and the two are combined, the gap by the gap member is formed in the closed magnetic path, so that the gap of the entire closed magnetic path becomes large, and the gap existing in the closed magnetic path The gap due to the gap is relatively small. In other words, even if the contact state between the magnetic component and the magnetic holder changes with each measurement, that is, the size of the gap may change, the effect of the gap due to the gap that easily changes depending on the contact state can be reduced. Therefore, the measurement accuracy for each measurement can be stabilized.

  The gap member is not particularly limited as long as it is made of a nonmagnetic material. For example, a resin adhesive tape (specific example, cellophane tape or polyimide tape) may be used as the gap member, and the gap member may be attached to the attachment surface of the magnetic holder. In addition, the gap member may be formed using a ceramic such as alumina, or a resin such as polyimide or glass epoxy. Here, the thickness of the gap member may be set as appropriate so that the leakage magnetic flux does not become too large, for example, 1 μm to 1000 μm.

  One form of the flaw inspection method of the present invention includes pressing a magnetic component against a magnetic holder.

  As one form of the flaw inspection apparatus of this invention, providing the pressing means which presses a magnetic component with respect to a magnetic holder is mentioned.

  As described above, if the contact state between the magnetic component and the magnetic holder changes for each measurement, the measurement accuracy for each measurement is not stable. According to the above configuration, the contact state between the magnetic component and the magnetic holder can be stably maintained, so that the measurement accuracy for each measurement can be stabilized.

  The pressing method (means) is not particularly limited as long as the magnetic component is pressed against the magnetic holder, that is, the magnetic component and the magnetic holder are brought into close contact with each other. For example, it can be realized by urging at least one toward the other by gravity by a weight or elastic force by a spring.

  One aspect of the flaw inspection method of the present invention is to use a magnetic component as a dust core.

  The dust core has a higher magnetic flux density than when a ferrite material is used, and is suitable for magnetic parts such as a choke coil and an electromagnetic valve.

  The method and apparatus for inspecting a flaw of a magnetic part according to the present invention can reliably inspect all the flaws of a magnetic part in a short time and can be inlined.

It is the schematic explaining the magnetic component used in Embodiment 1 of this invention, (A) is a perspective view of a magnetic component, (B) is a longitudinal cross-sectional view of a magnetic component. It is a schematic perspective view explaining the wound inspection apparatus which concerns on Embodiment 1 of this invention. It is a schematic block diagram explaining the wound inspection apparatus which concerns on Embodiment 1 of this invention. It is a schematic block diagram explaining the wound inspection apparatus which concerns on Embodiment 2 of this invention.

  Embodiments of the present invention will be described with reference to the drawings. Here, a case where a magnetic component having the shape shown in FIG. 1 is an inspection target will be described as an example.

<Embodiment 1>
(Magnetic parts)
A magnetic component 100 shown in FIG. 1 includes a substantially cylindrical inner wall portion 101, a substantially cylindrical outer wall portion 102, and a substantially annular bottom wall portion 103 that connects one end sides of both the inner and outer wall portions. Have. This magnetic component 100 has a double inner wall portion 101 and outer wall portion 102, is surrounded by the inner wall portion 101, the outer wall portion 102, and the bottom wall portion 103, and has an opening at the other end of both the inner and outer wall portions. It is the container shape in which the space which has was formed.

  The magnetic component 100 is a dust core and is manufactured by integrally molding with a mold. Since the magnetic component 100 has a so-called complicated shape, it corresponds to a seam in manufacturing (in this example, a connection portion between the inner wall portion 101 and the bottom wall portion 103, a connection portion between the outer wall portion 102 and the bottom wall portion 103). A part (a part surrounded by a dotted line in FIG. 1B) is easily damaged (cracked).

(Scratch inspection device)
The wound inspection apparatus 1 according to Embodiment 1 shown in FIGS. 2 and 3 includes a magnetic holder 10, an induction coil 20, a magnetization characteristic measurement unit 30, and a determination unit 40. Hereinafter, the configuration of the apparatus 1 will be described in detail. In FIG. 3, the magnetic component 100 and the magnetic holder 10 are shown in cross section (the same applies to FIG. 4 described later).

  The magnetic holder 10 is formed of the same powder magnetic core as the magnetic component 100, and forms a closed magnetic path when combined with the magnetic component 100. In this example, the magnetic holder 10 has an annular shape, with the bottom wall 103 side of the magnetic component 100 being the upper side and the opening side being the lower side, and the end surfaces of the inner wall 101 and the outer wall 102 of the magnetic component 100 are the magnetic holder 10. It attaches so that it may touch the upper surface of. That is, the attachment surface 11 of the magnetic component 100 is provided on the upper surface of the magnetic holder 10. Further, as shown in FIG. 3, a groove 12 is formed on the upper surface of the magnetic holder 10 at a location corresponding to the opening of the magnetic component 100, and a part of the induction coil 20 described later is accommodated. ing. The magnetic holder 10 is fixed on the stage 50 as shown in FIG.

  As shown in FIG. 3, the closed magnetic path is formed by attaching the magnetic component 100 to the magnetic holder 10 and combining them. In this example, a closed magnetic path is formed in which the magnetic flux passes through the outer wall 102, the bottom wall 103, and the inner wall 101 of the magnetic component 100, passes through the magnetic holder 10, and returns to the outer wall 102 (arrow in FIG. 3). Indicates the direction of the magnetic flux). Note that the direction of the magnetic flux varies depending on the magnetic field applied by the induction coil 20.

  The induction coil 20 is means for applying a magnetic field to the closed magnetic circuit. The induction coil 20 is connected to a power source (not shown), and current is supplied from the power source. In this example, the induction coil 20 is connected to a DC power supply, and the intensity of the applied magnetic field can be varied by adjusting the current supplied from the power supply. When the magnetic component 100 is attached to the magnetic holder 10 and the induction coil 20 is combined, the induction coil 20 is surrounded by the magnetic component 100 (the inner wall portion 101, the outer wall portion 102 and the bottom wall portion 103) and the magnetic holder 10. It will be in the state stored in space.

  The induction coil 20 is formed by winding a winding having an insulating coating on the surface of a conductor. The number of turns of the induction coil 20 and the conductor diameter (conductor cross-sectional area) are appropriately determined according to the applied magnetic field necessary for measuring the magnetization characteristics. Since the magnetic field is proportional to the number of turns and the current, it is easy to obtain the applied magnetic field strength necessary for measurement by increasing the number of turns or increasing the conductor diameter to facilitate the flow of current. In this example, in consideration of the storage space of the induction coil 20, the induction coil 20 is formed by winding 50 turns of a wire having a diameter of 0.35 mm on which the enamel coating is applied. The induction coil 20 is wound and held around a bobbin 21 as shown in FIG.

  The magnetization characteristic measuring means 30 is a means for measuring the magnetization characteristic of the closed magnetic path when a magnetic field is applied to the closed magnetic path. In this example, a BH analyzer is used as the magnetization characteristic measuring means 30. This magnetization characteristic measuring means 30 includes a detection coil (not shown), and is configured such that the detection coil detects a magnetic field generated in a closed magnetic path. The magnetization curve is measured by measuring the induced voltage generated in the detection coil. Further, the magnetization characteristic measuring means 30 can also obtain various magnetization characteristics such as maximum magnetic permeability (μm), initial magnetic permeability (μi), B50 and B100 from the magnetization curve.

  Like the induction coil 20, the detection coil is formed by winding a winding. In this example, the same coil as the induction coil 20 is wound 10 times on the outer periphery of the induction coil 20 to form a detection coil.

  The discriminating unit 40 is a unit that obtains the measured magnetization characteristic of the closed magnetic circuit from the magnetization characteristic measuring unit 30 and discriminates whether or not the magnetic component 100 is damaged based on the measured magnetization characteristic (measured value). In this example, an electronic computer (computer) is used as the discrimination means 40. The discriminating means 40 stores a reference value of the magnetization characteristic, and the discriminating means 40 discriminates whether or not the magnetic component 100 is scratched by comparing the reference value with the measured value. Also, in this example, the maximum permeability (μm) is selected as the magnetization characteristic that serves as an index for determining the presence or absence of scratches, and based on the maximum permeability when using a magnetic component that has been confirmed to be good in advance. If the value is within the specified range of the reference value, it is determined as a non-defective product.

  Furthermore, the apparatus 1 includes a pressing unit that presses the magnetic component 100 against the magnetic holder 10. In this example, as shown in FIG. 2, after attaching the magnetic component 100 to the magnetic holder 10, a weight 55 placed on the magnetic component 100 (the surface on the bottom wall 103 side of the magnetic component 100) constitutes a pressing means. Yes. Further, the weight 55 is formed with a guide hole 56 inserted through a guide shaft 51 extending upward from the stage 50, and the weight 55 is slidably guided. By this guide, the load acting on the magnetic component 100 is easily applied evenly without being biased. In this example, the weight 55 made of copper and having a weight of 4 kg is used.

[Example 1]
Five magnetic parts 100 shown in FIG. 1 were manufactured, and these were used as samples 1 to 5. And the flaw inspection apparatus 1 which concerns on Embodiment 1 was evaluated using each sample. Specifically, each sample was inspected for damage several times, and the maximum magnetic permeability (μm) obtained by measurement in each inspection was examined. Table 1 shows the range of measured values of the maximum magnetic permeability (μm) and the average value.

  Moreover, the presence or absence of a flaw was confirmed about each sample after an inspection by cross-sectional observation. As a result, no scratch was confirmed for sample 1, but cracks were confirmed at the connection between outer wall 102 and bottom wall 103 for samples 2-5. When the crack lengths in Samples 2 to 5 were measured, they were as follows: Sample 2: 0.3 mm, Sample 3: 0.8 mm, Sample 4: 1.6 mm, and Sample 5: 2.2 mm.

  From the above results, there is a difference in the magnetization characteristics (in this case, maximum magnetic permeability (μm)) measured depending on the presence or absence of scratches on the magnetic component 100, and the magnetization characteristics may also vary depending on the size of the scratches. I understand. From this, it is possible to determine the presence or absence of scratches on the magnetic component 100 by measuring the magnetization characteristics of the closed magnetic circuit formed by the magnetic component 100 and the magnetic holder 10 when the magnetic component 100 is attached to the magnetic holder 10. You can see that For example, in this example, if the discriminating means 40 of the flaw inspection apparatus 1 sets the reference value range to 320 ± 2, the presence or absence of flaws on the magnetic component 100 can be determined.

<Embodiment 2>
The flaw inspection apparatus 2 according to the second embodiment shown in FIG. 4 is that the gap member 13 made of a nonmagnetic material is arranged on the mounting surface of the magnetic holder 10 according to the flaw inspection apparatus according to the first embodiment shown in FIG. Different from 1. In this example, a polyimide tape is used for the gap member 13, and the gap member 13 is disposed by being attached to the mounting surface of the magnetic holder 10. The thickness of the gap member 13 is about 40 μm.

  The effect of the presence or absence of the gap member 13 on the measurement accuracy was verified. Specifically, using the same magnetic component 100, the maximum magnetic permeability obtained by performing the inspection for the presence or absence of flaws 10 times both when the gap member 13 is arranged and when it is not arranged, and by measurement in each inspection (Μm) was examined. Table 2 shows each measured value of the maximum magnetic permeability (μm).

  From the results of Table 2, it can be seen that when the gap member is arranged, the variation in the measured value for each measurement is small as compared with the case where the gap member is not arranged. From this, it can be seen that the measurement accuracy can be stabilized by arranging the gap member 13.

  Note that the present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the gist of the present invention. For example, the shape and size of the magnetic component and the magnetic holder, the material, and the magnetization characteristics serving as an index can be changed as appropriate. Alternatively, an alternating current may be supplied to the induction coil, and an alternating magnetic field may be applied to the closed magnetic circuit to measure the magnetization characteristics of the closed magnetic circuit.

  The flaw inspection method and flaw inspection apparatus for magnetic parts of the present invention can be suitably used for inspection of magnetic parts.

1,2 Scratch inspection device
10 Magnetic holder
11 Mounting surface 12 Groove 13 Gap member
20 induction coil 21 bobbin
30 BH Analyzer (Measuring characteristic measurement means)
40 Electronic computer (discrimination means)
50 Stage 51 Guide shaft
55 Weight (pressing means) 56 Guide hole
100 Magnetic parts
101 Inner wall 102 Outer wall 103 Bottom wall

Claims (7)

A method for inspecting magnetic parts for inspecting the presence or absence of scratches on magnetic parts made of a magnetic material,
Attaching the magnetic component to be inspected to a magnetic holder made of a magnetic material, and forming a closed magnetic path with the magnetic component and the magnetic holder;
Applying a magnetic field to the closed magnetic path to measure magnetization characteristics;
Determining the presence or absence of scratches on the magnetic component based on the measured magnetization characteristics;
A method for inspecting a flaw of a magnetic component, comprising:   The method for inspecting a flaw of a magnetic component according to claim 1, wherein a gap member made of a nonmagnetic material is disposed on a mounting surface of the magnetic holder to which the magnetic component is mounted.   The method for inspecting a flaw of a magnetic component according to claim 1 or 2, wherein the magnetic component is pressed against the magnetic holder.   The method for inspecting a flaw of a magnetic component according to any one of claims 1 to 3, wherein the magnetic component is a dust core. A magnetic component scratch inspection apparatus for inspecting the presence or absence of scratches on a magnetic component made of a magnetic material,
The magnetic part to be inspected is attached, and a magnetic holder that forms a closed magnetic path by being combined with the magnetic part;
An induction coil for applying a magnetic field to the closed magnetic path;
Magnetization characteristic measuring means for measuring the magnetization characteristic of the closed magnetic path;
Discriminating means for discriminating the presence or absence of scratches on the magnetic component based on the measured magnetization characteristics;
A flaw inspection apparatus for magnetic parts, comprising:   6. The apparatus for inspecting a flaw of a magnetic part according to claim 5, further comprising a gap member made of a non-magnetic material disposed on an attachment surface of the magnetic holder to which the magnetic part is attached.   The flaw inspection device for a magnetic part according to claim 5 or 6, further comprising pressing means for pressing the magnetic part against the magnetic holder.

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