JP3358219B2 - Resin sealing method for bobbin coil - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a bobbin wound coil having a structure in which an iron core is buried at the center of a resin bobbin and a coil wire is wound around the outer periphery of the bobbin. A resin sealing method.

[0002]

2. Description of the Related Art As a bobbin-wound coil having the structure described above, for example, there is a sensing coil used for detecting the number of revolutions. This type of coil is put into practical use by sealing it with a resin for its protection.

[0003] The conventional method for sealing is to mainly use a thermosetting resin and form a resin mold layer by potting molding or transfer molding.

[0004] As shown in FIG.
A case 20 is prepared, and a bobbin winding coil (the sensing coil 1 in the figure) is inserted therein (in the case of a sensing coil, the magnet 4 and the yoke 5 are also inserted).
The thermosetting resin 21 is injected into the case and cured.

[0005] In transfer molding, a bobbin-wound coil is placed in a molding die, and a terminal 7 at a coil end shown in FIG.
And a core 23 protruding from the end of the bobbin is held and set, and a thermosetting resin 21 is formed under low pressure to form a mold layer.

[0006]

The sealing by potting molding requires a potting case. In addition, the thermosetting resin used in this method requires a preliminary mixing and stirring step of the main material and the curing agent and a heating and curing step after the injection, so that the sealing operation is complicated and takes time.

The same problem arises in the encapsulation by transfer molding because a thermosetting resin is used. In this method, it is necessary to cover the coil after sealing with a protective case 24 shown in FIG. 4B in order to protect the resin mold layer.

Further, in both methods, after the coil is molded, a protective mold layer 25 for connecting the terminal 7 and the signal line 9 drawn from the coil is provided, and a mounting bracket for fixing the coil to the support is separately provided. It is necessary to prepare and assemble, and the number of parts and the molding and assembling steps are large, which leads to an increase in cost.

An object of the present invention is to eliminate these problems.

[0010]

In order to solve the above-mentioned problems, in the present invention, an iron core embedded at the center of a resin bobbin is projected from one end of the bobbin. In addition, a shaft hole concentric with the iron core is provided on the other end surface of the bobbin, and a support pin is inserted into the shaft hole to support the protrusion of the support pin and the iron core, so that the bobbin-wound coil is placed in a molding die. Position and hold. Then, in this state, a method of introducing a thermoplastic sealing resin into the mold and providing a resin mold layer around the bobbin is adopted.

[0011]

The bobbin-wound coil is positioned and held in the mold cavity by using the projecting portion of the iron core and the support pin inserted into the shaft hole on the other end surface of the bobbin. Can be collectively sealed with resin with high precision, and only one molding step is required. In addition, since the mounting bracket can be provided integrally with the resin mold layer, the number of parts can be reduced.

Further, when a thermoplastic resin is used, the steps of adding and stirring a curing agent and heating and curing the resin become unnecessary, and efficient molding can be performed by an injection molding machine. Less.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIG. 1, one embodiment of a sealing method according to the present invention (an example of sealing a sensing coil) will be described.

FIG. 1 shows a sensing coil. As shown in FIG. 2, the coil 1 has a structure in which an iron core (pole piece) 3 and a magnet 4 are embedded in the center of a bobbin 2 made of a thermoplastic resin, and a winding coil 6 is wound around the bobbin body. It is. 7 is a terminal connected to the winding coil,
Some of them are embedded in bobbins.

The iron core 3 projects outward from one end of the bobbin 2 as shown in the figure. On the other end of the bobbin, a shaft hole 8 having a depth that does not reach the embedded object 5 is provided concentrically with the iron core 3.

The sensing coil 1 thus configured
Is set in a mold (not shown) of the injection molding machine after the signal line 9 is connected to the terminal 7. At this time, the protrusion of the iron core 3 is inserted into the hole of the support block 13 shown in FIG. 1, and the support pin 14 is inserted into the shaft hole 8 on the other surface of the bobbin to hold the sensing coil 1 in a fixed position in the cavity. I do. Then, the thermoplastic resin melted in this state is injected into the cavity to create the resin mold layer 10.

When the mounting bracket 11 is required, the resin mold layer 10 is formed by integrally molding the bracket. Also, the protection and sealing portion of the lead-out opening of the signal line 9 is integrally formed.

As the molding resin, polyamide-based, polyphenylene sulfide-based, polybutylene terephthalate-based and polyester-based resins are suitable. This resin is preferably the same as the resin forming the bobbin 2. If the thermal expansion coefficients of the bobbin 2 and the mold layer 10 are matched, stress due to the difference in thermal expansion is not applied to the interface between them, and the sealing reliability at the interface can be reliably maintained.

In addition, when the support pin 14 is pulled out after the resin molding, a pin hole remains in the resin molding layer 10.
Since this pin hole can be easily closed by the sealing plug 12 made of rubber or the like shown in FIG. 2, there is no influence on the sealing performance.

[0020]

As described above, according to the present invention, the bobbin-wound coil is positioned and held in the mold by the iron core protruding from one end of the bobbin and the support pin inserted into the shaft hole at the other end of the bobbin. As a result, the sealing of the outer periphery and the integral molding of the mounting bracket are made possible, and the steps of adding and stirring a hardener using a thermoplastic resin and heating and curing the resin can be omitted. There is an effect that a high bobbin-wound coil can be easily and inexpensively manufactured without taking time and effort.

Here, a sensing coil is taken as an example of a coil to be sealed, but the method of the present invention can also be used for sealing a solenoid coil used for a relay or other equipment, molding a housing, and the like. .

[Brief description of the drawings]

FIG. 1 shows an example of the sealing method of the present invention.

FIG. 2 is a sectional view showing an example of a sensing head for a rotation sensor manufactured by the method of FIG. 1;

3A is an explanatory view of sealing by potting molding, and FIG. 3B is a cross-sectional view of a rotation sensor sensing head made through a potting molding step;

4A is an explanatory view of sealing by transfer molding, and FIG. 4B is a cross-sectional view of a rotation sensor sensing head made through a transfer molding process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sensing coil 2 Resin bobbin 3 Iron core 4 Magnet 6 Winding coil 7 Terminal 8 Shaft hole 9 Signal line 10 Resin mold layer 11 Mounting bracket 12 Sealing plug 13 Support block 14 Support pin

Continuation of the front page (56) References JP-A-54-153864 (JP, A) JP-A-2-248226 (JP, A) JP-B-41-1887 (JP, B1) JP-B-49-15733 (JP) , B1) JP-B-57-11133 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 45/00-45/84 B29C 33/12-33/18 H01F 27/32 H01F 41/12

Claims (2)

(57) [Claims] 1. A method for sealing a bobbin wound coil comprising winding a coil wire around a body portion of a resin bobbin having a core at its center, wherein the core is projected from one end of the bobbin. A shaft hole concentric with the iron core is provided on the end face, a support pin is inserted into the shaft hole, and the support pin and the protrusion of the iron core are supported to position and hold the bobbin-wound coil in the molding die. Forming a resin mold layer around a bobbin by introducing a thermoplastic sealing resin into a mold. 2. The resin sealing method for a bobbin wound coil according to claim 1, wherein the same resin as the bobbin material is used as the sealing resin.