JPH0724242B2 - Inductor device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an inductor device such as a fixed coil or a filter having a ferrite core as a magnetic core. More specifically, the present invention relates to an open magnetic circuit type inductor device which has a small inductance change with respect to external stress and can be miniaturized.

2. Description of the Related Art In electronic devices such as televisions, video recorders, and car phones, filters and fixed coils having a ferrite core, which is an oxide magnetic material, as a magnetic core are often used as inductor devices. In this fixed coil or filter, winding is applied to a drum-shaped magnetic core for the purpose of ensuring mechanical strength, improving moisture resistance, maintaining shape retention, etc., and then coating or molding of resin is performed.

However, in such fixed coils and filters provided with resin exterior materials, the ferrite core used as a magnetic core causes a change in inductance due to stress such as hardening and shrinkage of the exterior material, and the amount of exterior resin and the curing temperature However, there is a problem in that the obtained inductance varies depending on the manufacturing conditions, and a high quality product with a small inductance tolerance cannot be obtained.

In order to solve this problem, the shape of the magnetic core is enlarged, or a buffer coat resin is applied to absorb stress, but in both cases, electronic devices are made smaller and thinner,
We were unable to meet design requirements such as cost reduction. Moreover, the problem of inductance variation has not been fully solved.

Therefore, there is a strong demand for the development of a small, thin, highly accurate, low cost inductor device,
To this end, it has been desired to develop a ferrite core that is stable against stress fluctuations in the resin sheath and has a small inductance change.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present invention aims to provide an open magnetic circuit type inductor device that overcomes such conventional drawbacks and uses a ferrite core having a small inductance change with respect to the stress of the resin sheath. It was made.

Means for Solving the Problems The present inventors have conducted various studies to develop an open magnetic circuit type inductor device having a small inductance change with respect to the stress of a resin sheath, and as a result, a predetermined ratio of Fe ₂ O ₃ , ZnO, Cu
It was found that the object can be achieved by using, as a magnetic core, a sintered body of a composition containing PbO in a specific amount ratio as a basic component containing O and NiO, and optionally CoO, and based on this finding. Based on this, the present invention has been completed.

That is, the present invention, Fe ₂ O ₃ 30-50 mol%, CuO 15 mol%
Below, ZnO 35 mol% or less, the basic component consisting of CoO 0 ~ 1.0 mol% and the balance NiO, the sintered body of the composition containing PbO 2.5 ~ 15.0 wt% was used as the magnetic core, and the conductor wire was wound around it for the required number of times. And an open magnetic circuit type inductor device having a synthetic resin coating formed thereon.

Hereinafter, the present invention will be described in detail.

In the present invention, in the magnetic core, Fe ₂ O ₃ 30 to 50 mol%, CuO15
Mol% or less, ZnO 35 mol% or less, CoO 0 to 1.0 mol% and Ni
It is important to use a sintered body of a composition in which PbO2.5 to 15.0% by weight is mixed with the basic component consisting of the balance O.

This sintered body has a high specific resistance (10 ⁵ to 10 ⁹ Ω ・ c
m), which has good high frequency characteristics and can be directly wound into the shape of the magnetic core.

When Fe ₂ O ₃ exceeds 50 mol%, ρ decreases due to Fe ²⁺ precipitation, and when it is less than 30 mol%, magnetic permeability decreases. When CuO is contained, the sinterability is improved, but when it exceeds 15 mol%, the Q is lowered. When ZnO is contained, the magnetic permeability increases, but when it exceeds 35 mol%, the Curie point decreases to 100 ° C. or lower. When CoO is contained, Q increases, but when it exceeds 1 mol%, the cost increases. NiO is Fe ₂ O ₃ , CuO, ZnO, CoO
When the quantity is decided, it is inevitably decided. It is also effective to contain an oxide such as manganese oxide or magnesium oxide.

In the present invention, PbO2.5 to 1
It is important to use a sintered body containing 5.0% by weight for the magnetic core.

The required amount of PbO depends on the amount of ZnO used together. Generally, when the amount of ZnO is large, the amount of PbO may be small, and when the amount of ZnO is small, the amount of PbO is increased. There is a need. Figure 1 shows the basic composition Fe ₂ O ₃ 48.5 mol%, CuO4.0
3 is a graph showing the inductance change rate with respect to external stress when the PbO amount ratio is changed for mol%, ZnO 18.0 mol% and Ni 29.5 mol%. FIG. 2 is a graph showing the rate of change in inductance with respect to external stress when drum-shaped magnetic cores made of various materials are used.

As is clear from FIG. 2, in the conventional product, the change in the inductance is large with respect to the change in the external stress as shown in the section B, whereas in the product of the present invention, the change in the inductance is changed with respect to the change in the external stress. It is preferable to use a material that is small and has many flat portions such as the portion A, for example, X1, X2, and X3.

Next, as the shape of the magnetic core, one that can form an open magnetic path after winding, such as a round bar core or a drum core, is effective.

Next, in the present invention, it is necessary to wind a conducting wire around such a magnetic core a required number of times and further coat a synthetic resin thereon.

It is not uncommon for a conventional ferrite core to fluctuate by 10% or more with respect to variations in external stress applied from the exterior resin or the like, but the magnetic core of the present invention can easily obtain an inductance change rate of 2% or less. The upper limit of the PbO content is not critical, but if it exceeds 15% by weight, the magnetic permeability will decrease. It should be noted that various characteristics deterioration due to the decrease in magnetic permeability can be easily adjusted by increasing the number of windings of the winding.

The reason why the effect of the present invention is obtained is not fully understood, but in the process of producing a sintered ferrite containing PbO, PbO is precipitated at the crystal grain boundary to form an open magnetic path. It is presumed that the magnetic characteristics are stabilized against the stress because the external stress is easily absorbed in combination with the possible shape.

In the present invention, the synthetic resin used as the coating material may be either a thermoplastic resin or a thermosetting resin. Examples of such materials include polyolefin resin, polyester resin, polyamide resin, polycarbonate resin, polyurethane resin, phenol resin, urea resin, epoxy resin and the like.

The coating with these synthetic resins may be performed by dipping, coating, spraying, or the like, or by molding such as injection molding or casting.

Next, the structure of the inductor device of the present invention will be described with reference to the accompanying drawings.

FIG. 3 is a partial cross-sectional view showing an example in which an insulating coating 5 is formed by immersing a structure in which a polyurethane copper wire 2 is wound around a predetermined magnetic core 1 into which epoxy coating is used as a synthetic resin. It is shown by. In addition, 3 is a lead wire and 4 is a contact opening copper foil.

FIG. 4 is a partial cross-sectional view of an example in which a polyurethane copper wire 2 is wound around a predetermined magnetic core 1 in which a lead wire 3 is connected to an end, and an epoxy coating is applied on the polyurethane copper wire 2 to form an insulating coating 5. It is shown.

FIG. 5 shows an example in which a coil 2 is formed by winding a copper wire around a predetermined magnetic core 1, and an exterior resin 5 is applied by injection molding onto a structure having a metal terminal 6 at the end of the magnetic core. It is a partial cross-sectional perspective view.

Advantageous Effects of Invention The inductor device of the present invention has a small inductance change with respect to the stress of the resin sheath, and even if there is a change in the conditions such as curing of the resin sheath, shrinkage force, and coating thickness when performing resin sheathing, the magnetic core. The magnetic property of is stable, which is a characteristic that cannot be predicted from the conventional inductance.

That is, FIG. 6 shows the results of examining the temperature characteristics of the inductor of the present invention and the commercially available inductor, which have substantially the same level of temperature characteristics after winding and before resin coating, after the same resin coating. In the case of the inductor of the present invention (broken line), the inductance change rate after resin coating is significantly higher than that before resin coating (chain line), whereas in the case of the inductor of the present invention ( On the contrary, the solid line shows that the rate of inductance change is significantly smaller after the resin coating.

Since the inductor of the present invention has stable magnetic characteristics as described above, process control is facilitated, and a narrow tolerance inductor device with small variation in inductance can be easily manufactured and can be miniaturized. It has a significant industrial effect such as becoming.

EXAMPLES Next, the present invention will be described in more detail by way of examples.

Example 1 molar component ratio of _{Fe 2 O 3: NiO: CuO} : ZnO = 48.5: 31.5: 5: The Ni-Cu-Zn ferrite is 15 created by conventional conventional methods.
Add 10% by weight of PbO to this ferrite, mix it, and then
mm, 3 mm long drum core is pressure-molded, 950-1200 ℃
Then, it was fired for 2 hours to obtain a drum type magnetic core made of an oxide magnetic ferrite sintered body. This magnetic core and the commercially available Ni-Cu-Zn
A magnetic core having the same shape as the magnetic core made of a system ferrite sintered body,
After winding 100 pieces of material so that an inductance value of 30 μH can be obtained, paint with epoxy resin to a thickness of 1.5 mm,
Dried and baked. With respect to the inductor device thus obtained, the inductance was measured and the rate of change of the inductance was investigated. When using a commercial product, the average value of the inductance change rate is -6.5% and the variation range is
The average value of the inductance change rate is +0.2 in the product of the present invention using the PbO-containing magnetic core, while it is 5.4 μH.
%, The variation range was 1.5 μH, which was a remarkable improvement.

Example 2 Both the outer shape and the length of the drum type magnetic core in Example 1 are
An inductor device was prepared in the same manner as in Example 1 except that the resin sheath was formed by a resin molding method with a larger external stress, the inductance was measured, and the rate of change of the inductance was examined. The average value of the inductance change rate when using a commercial product is -8.7% and the variation range is 7.5 μH, whereas the average value of the inductance change rate of the present invention product using the PbO-containing magnetic core is -8.7%. At 1.5%, the variation range was 2.1 μH, showing a remarkable improvement.

Thus, it can be seen that the product of the present invention is extremely stable against external stress due to the shrinkage of the resin and is sufficiently practical.

Example ₃ Fe ₂ O 3 47 mol%, CuO8 mol%, relative to the basic composition consisting of ZnO29 mol% and NiO16 mol%, using a material obtained by blending 0-15% by weight of PbO, outer diameter 5 mm, length A 6 mm round bar-shaped magnetic core was created, and a copper wire was wound 100 times around this, and then epoxy paint was applied to a thickness of 1.5 mm to manufacture an open magnetic circuit type inductor.

Separately using the same material, outer diameter 2.0 mm, inner diameter 1.5 mm, height 0.3 m
After making a toroidal magnetic core and winding a copper wire in the same manner, the same epoxy paint was applied to a thickness of 1.5 mm to manufacture a closed magnetic circuit type inductor.

The following table shows the results of obtaining the inductance change rates before and after resin coating for each of these inductors.

As is clear from this table, the addition of PbO reduces the inductance change in the open magnetic circuit, but no effect is observed in the closed magnetic circuit.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the PbO content and the inductance change rate in the magnetic core of the present invention, FIG. 2 is a graph showing the relationship between the external stress and the inductance change rate, and FIG. 3 is the structure of the inductor of the present invention. A partial sectional side view showing an example,
FIG. 4 is a partial cross-sectional side view of another example, FIG. 5 is a partially broken perspective view of yet another example, and FIG. 6 is a graph showing a difference in temperature characteristics between the inductor of the present invention and a commercial inductor. . In the figure, reference numeral 1 is a magnetic core, 2 is a winding wire, 3 is a lead wire, and 5 is a synthetic resin insulating coating.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area C04B 35/30

Claims (2)

[Claims] 1. Fe ₂ O ₃ 30 to 50 mol%, CuO 15 mol% or less, Zn
O35 mol% or less, the basic component consisting of CoO 0 ~ 1.0 mol% and the balance NiO, the sintered body of the composition containing PbO 2.5 ~ 15.0 wt% was used as a magnetic core, and the conductor wire was wound around the core a required number of times. An open magnetic circuit type inductor device having a synthetic resin coating on top of it. 2. The open magnetic circuit type inductor device according to claim 1, wherein an inductance change rate with respect to an external stress is within 2%.