JP2008021836A - Electromagnetic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnetic device capable of suppressing the occurrence of a crack in a magnetic substance core. <P>SOLUTION: This electromagnetic device comprises a bonded structure wherein a magnetic substance 2 formed of a brittle material is bonded to a bonding object 3 via a gap layer 4 having a predetermined height. In the bonded structure, the magnetic substance 2 and the bonding object 3 are bonded together with a bonding agent 6, and the height of the gap layer 4 is specified by arranging pillar-shaped spacers 51 within the bonding agent 6 and a frame-like spacer 52 having a rigidity lower than that of the pillar-shaped spacer 51 in the periphery of the bonding agent 6. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electromagnetic device, and more particularly to an adhesive structure of a brittle magnetic material typified by a ferrite magnet.

Electromagnetic devices include, for example, a closed magnetic circuit type choke coil in which a coil wound with an insulated wire is housed between upper and lower magnetic cores. Generally, a part of a magnetic path has a magnetic permeability different from that of the core material. A means for adjusting the electrical characteristics such as inductance value and current capacity by forming a layer (hereinafter referred to as a gap layer) is employed. By adjusting the electrical characteristics in the gap layer, it is possible to obtain an electromagnetic device having optimal electrical characteristics for each usage environment while using a common magnetic component.
Usually, an electromagnetic force is applied to the magnetic core of the electromagnetic device during use, and thus sufficient fixing strength is required. Therefore, as a method for producing the gap layer, bonding using a gap gap adjusting spacer and an epoxy adhesive is generally used (see, for example, Patent Document 1).

In an electromagnetic device using such an adhesive structure, it is important to make the magnetic body a ferrite magnet in order to achieve both excellent characteristics and cost. However, since a ferrite magnet is a brittle material unlike magnetic steel or the like, cracks are easily generated and are easily broken from there.
An adhesive such as an epoxy-based adhesive having a high strength is accompanied by a temperature rise during curing, so that a difference in thermal expansion occurs between the adhesive and the magnetic core during curing. Therefore, an electromagnetic device using a brittle magnetic material typified by a ferrite magnet as a magnetic core has a problem that cracks are generated due to the generation of thermal stress due to the above-described thermal expansion difference, and breaks from the cracks. Therefore, for example, in Patent Document 1, a measure is taken to reduce the generated stress due to thermal deformation of the adhesive by filling the hole in the spacer with the adhesive.

Japanese Patent Laid-Open No. 3-19306 (page 3-4, FIG. 2)

The joint structure disclosed in Patent Document 1 is a configuration for reducing the thermal stress generated in the magnetic core due to the fact that the linear expansion coefficient of the adhesive is larger than the linear expansion coefficient of the ferrite magnet constituting the magnetic core. is there.
On the other hand, even when the linear expansion coefficient of the spacer material is large and the difference from the linear expansion coefficient of the magnetic core is large, generation of thermal stress due to the spacer material itself becomes a problem. In particular, the use conditions of the electromagnetic device are severe, which becomes a problem when exposed to a lower temperature environment.
That is, since the spacer defines the height of the gap layer, it is preferable to use a material having high rigidity as the spacer material. However, when the spacer has high rigidity, if the spacer has a large linear expansion coefficient, the magnetic core Is more susceptible to thermal stress due to the spacers, and thus more susceptible to cracking.

  The present invention has been made to solve such problems, and an object of the present invention is to provide an electromagnetic device capable of suppressing the occurrence of cracks in a magnetic core.

  An electromagnetic device according to the present invention is an electromagnetic device including a bonding structure for bonding a magnetic body made of a brittle material to an object to be bonded through a gap layer having a predetermined height, and the bonding structure includes an adhesive. The magnetic body and the object to be bonded are bonded together, a columnar spacer is disposed inside the adhesive, and a frame-shaped spacer having a lower rigidity than the columnar spacer is disposed on the outer periphery of the adhesive, and the gap layer The height is defined.

According to this invention, when the adhesive and the spacer are used to join the magnetic body made of a brittle material and the object to be bonded through the gap layer having a predetermined height, the linear expansion coefficient of the spacer is Even if it is larger than the linear expansion coefficient of the magnetic material, the thermal stress generated in the magnetic material can be greatly reduced, and the reliability of the electromagnetic device can be greatly improved.
In addition, the gap height can be increased, and the adjustment range of the electrical characteristics can be widened.

Embodiment 1 FIG.
FIG. 1 is a sectional view showing a part of an electromagnetic device according to Embodiment 1 of the present invention, in which a magnetic body 2 and a magnetic body 3 constituting a magnetic core are joined via a gap layer 4 having a predetermined height. This is an electromagnetic device having a joining structure. In FIG. 1, a magnetic body 2 made of a ferrite magnet is installed inside a hollow coil 1 around which an insulated wire is wound, and a magnetic body made of a ferrite magnet is vertically arranged so as to constitute a magnetic path. The body 3 is joined via a gap layer 4 of a certain height.

2 is an enlarged cross-sectional view of a joint portion in the electromagnetic device according to the first embodiment of the present invention, and FIG. 3 is a cross-sectional view taken along the line II of FIG.
In FIG. 2 and FIG. 3, the gap layer 4 is an epoxy adhesive 6 that bonds the spacer 5 that defines the height of the gap layer 4 to the magnetic body 2 and the magnetic body 3 and has an adhesive strength that can withstand electromagnetic force. It is comprised by.
The spacer 5 includes a columnar spacer 51 disposed inside the adhesive 6, a frame-shaped spacer 52 disposed on the outer periphery of the adhesive 6, and a beam 53 that connects the columnar spacer 51 and the frame-shaped spacer 52. It is comprised by.
The spacer 5 has a shape in which the radial width W ₂ of the frame spacer 52 is smaller than the radial width W ₁ of the column spacer 51 and the rigidity of the frame spacer 52 is lower than the rigidity of the column spacer 51. ing. The thinner the frame spacer 52, the better.

Further, the spacer 5 is integrally formed, for example, by cutting, and if the beam 53 connecting the columnar spacer 51 and the frame spacer 52 is provided with the beam 53 and the rigidity of the spacer 5 becomes too high, cracks will occur. Since it becomes easy to generate | occur | produce, it is comprised so that the center part of the spacer 5 may not be passed so that it may suppress that the rigidity of a spacer becomes high too much. Furthermore, they are arranged to be as small as possible and the smallest number.
Further, the beam 53 is provided in the frame-shaped spacer 52 so as to have as few recesses as possible in the shape of the space filled with the adhesive 6. Further, when the adhesive 6 is filled, the beam 53 has a column shape. The adhesive 6 is configured to spread over the entire outer periphery of the spacer 51.
2 and 3, the columnar spacer 51 and the frame spacer 52 are integrally formed with the beam 53, but the beam 53 is not provided and may be separate.

By adopting such a configuration, even if the linear expansion coefficient of the spacer 5 is larger than the linear expansion coefficient of the magnetic bodies 2 and 3, the thermal stress generated in the magnetic bodies 2 and 3 can be greatly reduced. The reliability of the device can be greatly improved.
In addition, the gap height can be increased, and the adjustment range of electrical characteristics as an electromagnetic device can be widened.
In addition, since the gap end portion where high stress is generated becomes a spacer with high molding accuracy, it is possible to manufacture a highly reliable electromagnetic device without variations.

In FIG. 2, the frame spacer 52 is provided with a fillet (protrusion) 54 along the circumferential direction at the junction with the magnetic bodies 2 and 3. The shape of the fillet 54 may be rectangular, but as shown in FIG. 2, a shape that gradually decreases in height as it moves away from the frame-like spacer 52 can reduce the stress at the adhesion portion with the magnetic material, and is desirable.
In FIG. 2, the fillet 54 is provided on both sides of the frame spacer 52, but may be provided only on the outer side or may not be provided.

  2 and 3 show four examples of the number of columnar spacers 51, one may be used. Three or more are desirable for stably defining the height of the gap layer 4.

  In the present embodiment, the bonding structure between the magnetic bodies has been described, but it is natural that the magnetic body is bonded to another bonding target via a gap layer having a predetermined height and receives a thermal history at the bonding portion. Needless to say, the bonding structure of the present invention can also reduce the thermal stress and is effective for the bonding structure.

Next, the effect of the bonding structure of the present embodiment will be described in comparison with a conventional bonding structure.
FIG. 4 shows a cross-sectional shape of the gap layer 4 that has been generally used so far, and FIG. 5 shows a cross-sectional view taken along the line II of FIG. 4 and 5, the adhesive 6 is filled in the center, and a frame-like spacer 50 is installed around the center. Since the height of the gap layer 4 is determined by the dimensional accuracy of the spacer 50, rigidity is required with respect to the load during use during bonding. Therefore, the dimension of the spacer 50 has a certain size. Since the gap layer 4 adjusts the characteristics of the electromagnetic device by utilizing the extremely low permeability compared with the magnetic bodies 2 and 3, a metal cannot be sandwiched between the gap layers 4. The spacer 50 is mainly made of plastic such as polypropylene, which is excellent in cost and rigidity. 4 and 5, when the spacer 50 is made of, for example, plastic, the width in the radial direction is required to be about 3 mm with respect to the spacer 50 having a height of 3 mm and a diameter (outer diameter) of 50 mm.

In general, plastic has a larger coefficient of linear expansion than a ferrite magnet, and therefore a thermal stress may be generated in the ferrite magnet due to a temperature rise when the adhesive is cured, and a crack 7 may be generated. In addition, the high-strength adhesive 6 typified by an epoxy system used for bonding also has a large linear expansion coefficient and a property of shrinking at the time of curing, causing thermal stress and generating cracks 7 in the ferrite magnet. Sometimes.
When the crack 7 is generated in the magnetic body of the electromagnetic device, there are problems that noise due to electromagnetic force is generated, the magnetic body is damaged from the crack 7, and the device characteristics are deteriorated. This crack 7 also occurs when exposed to a low temperature environment, and becomes a factor of lowering the reliability of the electromagnetic device.

  With respect to the conventional configuration, only the configuration of the spacer in the gap layer was changed, and the generation of stress due to the thermal expansion difference was examined using FEM analysis. The linear expansion coefficient of the spacer 50 of the gap layer 4 and the adhesive 6 serving as a generation source of thermal stress is different from that of the magnetic bodies 2 and 3, respectively. Here, the case where the linear expansion coefficient of the spacer 50 and the adhesive 6 is larger than the linear expansion coefficient of the magnetic bodies 2 and 3 and the linear expansion coefficient of the spacer 50 is larger than the linear expansion coefficient of the adhesive 6 is considered. is doing. Moreover, the thermal history which changes in the temperature range from adhesive hardening temperature to low temperature environmental temperature (for example, 150 to -40 degreeC) is always given equally to each spacer structure. Furthermore, in all models, analysis was performed with the same magnetic core mesh size, so that the amount of thermal stress generated could be compared qualitatively.

FIG. 6 is a diagram in which a conventional general gap layer (Comparative Example 1) is modeled, and FIG. 7 is a FEM analysis result when thermal deformation is given to Comparative Example 1 to cause thermal deformation. In FIG. 7, the horizontal axis is the position in the magnetic core 2, and the positions A to D correspond to the positions A to D shown in FIG. 6. The vertical axis represents the generated stress value normalized with the maximum generated stress as 1.
As shown in FIG. 7, it can be seen that high stress is generated in the spacer portion, particularly the outer end portions A and D of the spacer 50.

Further, FIG. 8 shows the relationship of the maximum generated stress when the gap height h is changed. The horizontal axis is the ratio of the gap height h to the adhesive width (gap layer width L). The ratio when the adhesive width L and the radial width x of the spacer 50 are constant and the gap height h is changed is shown. It is what I took. The vertical axis is a numerical value obtained by normalizing the maximum generated stress generated in the magnetic core 2 with the maximum generated stress when the gap height / adhesion width is 0.1 as 1. It can be seen that the maximum generated stress increases as the gap height increases.
From this, it can be seen that if the gap height is increased in order to adjust the electrical characteristics of the electromagnetic device, cracks are likely to occur in the magnetic material. For this reason, it has been necessary to limit the adjustment range of the electrical characteristics in the gap shape generally used so far.

Next, as shown in FIG. 9, when the width x of the spacer 50 of Comparative Example 1 is made 70% smaller than that of Comparative Example 1 and the rigidity of the spacer is lowered (Comparative Example 2), the maximum is analyzed. The generated stress decreased to 65% as shown in FIG.
FIG. 10 is a diagram showing FEM analysis results for various spacer shapes, and the vertical axis represents the value of the maximum generated stress normalized with the maximum generated stress in Comparative Example 1 as 1. FIG. The gap layer 4 had the same width (adhesion width), height (spacer height), spacer 5 material, and adhesive 6 material.

  As can be seen from the results of Comparative Example 1 and Comparative Example 2, the thermal stress generated is small if the rigidity of the spacer 50 is low, but if the rigidity is low, the accuracy of the height of the gap layer 4 cannot be obtained. appear.

FIG. 11 is a diagram modeling the gap layer 4 according to the present invention.
FIG. 11 shows a columnar spacer 51 (with the same width as the spacer width of Comparative Example 1) having high rigidity inside the adhesive 6 and a frame-shaped spacer 52 (with a lower rigidity than the columnar spacer 51 on the outer periphery of the adhesive 6. It is the example (Example 1) which has arrange | positioned the same width as the spacer width of the comparative example 2. The gap layer 4 had the same width (adhesion width), height (spacer height), spacer 5 material, and adhesive 6 material.
Similarly to Example 1, the generation of stress due to the difference in thermal expansion was examined using FEM analysis.
As a result, no high stress was generated at the joint between the columnar spacer 51 and the magnetic bodies 2 and 3, and the maximum stress was generated at the joint between the frame-shaped spacer 52 and the magnetic bodies 2 and 3. Further, the maximum generated stress generated was reduced to 55% of the maximum generated stress generated in Comparative Example 1, as shown in FIG.

As described above, when the brittle magnetic body such as a ferrite magnet is bonded, the columnar spacer 51 having high rigidity is provided inside the adhesive 6, and the frame spacer 52 having low rigidity is provided on the outer periphery of the adhesive 6. By disposing, the thermal stress generated in the magnetic bodies 2 and 3 can be greatly reduced. Further, the height of the gap layer 4 can be increased by the columnar spacer 51, and the reliability of the electromagnetic device can be greatly improved.
Furthermore, the gap height can be increased, and the adjustment range of the electrical characteristics can be widened.

FIG. 12 is a diagram modeling a gap layer 4 having another configuration according to the present invention.
FIG. 12A shows a fillet (projection) 54 along the circumferential direction at the junction with the magnetic bodies 2 and 3 as shown in FIG. Is an example (Example 2). The dimensions of the fillet 54 in FIG. 12B are set to 1/3 for a / l and 1/7 for b / h.
Similarly to Example 2, the generation of stress due to the difference in thermal expansion was examined using FEM analysis.
As a result, as shown in FIG. 10, the maximum stress generated at the joint between the frame spacer 52 and the magnetic bodies 2 and 3 was reduced to 42% in Comparative Example 1 and 76% in Example 1.

  The thermal stress greatly depends on the shape of the end of the gap layer 4. In particular, it is possible to reduce the thermal stress by producing the fillet 54 at the end and lowering the rigidity, greatly improving the reliability of the electromagnetic device and increasing the gap height.

FIG. 13 is a diagram modeling a gap layer 4 having another configuration according to the present invention.
FIG. 13 shows an example (Example 3) in which the columnar spacer 51 and the frame-like spacer are connected and integrated by a beam 53 in the configuration of FIG.
Similarly to Example 3, the generation of stress due to the difference in thermal expansion was examined using FEM analysis.
As a result, even in the structure in which the spacer 5 is integrated, the maximum generated stress generated at the joint between the frame spacer 52 and the magnetic bodies 2 and 3 is 45% of that in Comparative Example 1, as shown in FIG. It decreases to 80% of Example 1, and the stress can be suppressed sufficiently low.

FIG. 14 shows FEM analysis results when thermal history is given to Example 3 and thermal deformation occurs. In FIG. 14, the horizontal axis is the position in the magnetic core 2, and the positions A to H correspond to the positions A to H shown in FIG. 13. The vertical axis represents the generated stress value normalized with the maximum generated stress in Comparative Example 1 as 1.
As shown in FIG. 14, stress is generated around the columnar spacer 51 and the frame spacer 53, and in particular, the maximum generated stress is generated at the outer end portions A and H of the frame spacer 50. Further, it can be seen that the maximum stress generated is significantly smaller than that of Comparative Example 1.

  In addition, since the rigidity is somewhat increased when integrated, the maximum generated stress is somewhat increased as shown in FIG. 10. However, by using an integrated spacer, the manufacturing process can be simplified and at the time of bonding. The thermal stress can be greatly reduced without changing the process and material, the reliability of the electromagnetic device can be greatly improved, and the adjustment range of the electrical characteristics depending on the gap height can be widened.

  Although not shown in FIG. 10, the same effect as that of the third embodiment can be obtained even in a configuration similar to FIG. 2 in which the fillets 54 are provided on both sides.

It is sectional drawing which shows a part of electromagnetic device by Embodiment 1 of this invention. It is an expanded sectional view of the junction part in the electromagnetic device by Embodiment 1 of this invention. It is sectional drawing in the II line | wire of FIG. It is an expanded sectional view of the junction part in the conventional electromagnetic device. It is sectional drawing in the II line | wire of FIG. It is the figure which modeled the conventional gap layer (comparative example 1). It is a figure which shows distribution of the generated stress in the conventional gap layer (comparative example 1). It is a figure which shows the relationship between gap height and generated stress in the conventional gap layer (comparative example 1). It is the figure which modeled the conventional gap layer (comparative example 2). It is a figure which shows the FEM analysis result with respect to various spacer shapes. It is the figure which modeled the gap layer (Example 1) concerning this invention. It is the figure which modeled the gap layer (Example 2) concerning this invention. It is the figure which modeled the gap layer (Example 3) concerning this invention. It is a figure which shows distribution of the generated stress in the gap layer (Example 3) concerning this invention.

Explanation of symbols

  1 Coil, 2, 3 Magnetic body, 4 Gap layer, 5 Spacer, 51 Columnar spacer, 52 Frame spacer, 53 Beam, 54 Fillet, 6 Adhesive, 7 Crack

Claims (5)

An electromagnetic device having a joining structure for joining a magnetic body made of a brittle material to an object to be bonded through a gap layer having a predetermined height, wherein the bonding structure is bonded to the magnetic body and the object to be bonded by an adhesive. In addition, a columnar spacer is disposed inside the adhesive, and a frame-shaped spacer having a lower rigidity than the columnar spacer is disposed on the outer periphery of the adhesive to regulate the height of the gap layer. An electromagnetic device characterized by being. The electromagnetic device according to claim 1, wherein a linear expansion coefficient of the spacer is larger than a linear expansion coefficient of the magnetic substance. The electromagnetic device according to claim 1, wherein the magnetic body is a ferrite magnet. The electromagnetic device according to any one of claims 1 to 3, wherein the frame-shaped spacer has a fillet along a circumferential direction at a joint portion with the magnetic body. The electromagnetic device according to any one of claims 1 to 4, wherein the columnar spacer and the frame-shaped spacer are integrated by connecting with a beam.

Images