JPS6134911A - Ignition coil for internal-combustion engine - Google Patents

Abstract

PURPOSE:To enable to completely prevent the generation of cracks on cast resin by a hot-and-cold cycle and the damage on the primary bobbin and the like by a method wherein the difference of a linear expansion coefficient is absorbed by moving a core in the primary bobbin within the range of thermal caulking. CONSTITUTION:The cylindrical protrusion 1a located at one end of the primary bobbin 1 is protruded to outside from the open end face of a case 6, and cast resin 7 is poured from the open end of the case 6 located on the open end face of said primary bobbin 1, and the resin is hardened. After the resin 7 is hardened, the primary bobbin protrusion 1a is thermo-caulked into a conical shape as shown by a broken line in the diagram, and the coming off of a core 8 is prevented. By constituting the coil as above-mentioned, the core 8 is separated from the cast resin 7 by the primary bobbin 1, and the core 8 can be moved in the primary bobbin 1 in axial direction within the range of the elastic deformation of the thermally caulked part of the cylindrical protrusion 1a, thereby enabling to improve the cold-heat resisting property of the coil by absorbing the stress generated by the hot-and-cold cycle.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an ignition coil for an internal combustion engine.

[Conventional technology]

Conventional ignition coils are generally made by injecting and hardening casting resin into a case that houses the primary and secondary coils placed around the outer periphery of the core. Since the coefficients of linear expansion of the two materials differ greatly, there was a drawback that cranking occurred in the casting resin during the thermal shock test.

Conventionally, in order to eliminate the above-mentioned drawbacks, it has been considered to cover the outer periphery of the core with a primary bobbin to prevent direct contact between the core and the casting resin (for example, Utility Model No. 58-87317 However, since it is unavoidable that the core moves relative to the primary bobbin, etc. due to the cooling/heating cycle, this relative movement of the core may cause damage to the primary bobbin, etc. that covers the core. There is a disadvantage that it occurs.

[Problem that the invention seeks to solve]

Therefore, the present invention reliably prevents the occurrence of cranking of the casting resin and damage to the primary bobbin due to the cooling/heating cycle.

[Means for solving problems]

Therefore, the present invention provides a core and a
Next, in the ignition coil for an internal combustion engine, which is made by housing the secondary coil in a case and injecting and hardening a casting resin into the case, the core is inserted inside and the core is placed on the outer periphery.
A primary bobbin having a secondary coil wound thereon is provided, the open end of the primary bobbin protrudes from the open end of the case, and
The object of the present invention is to provide an ignition coil for an internal combustion engine in which the protrusion of the primary bobbin is exposed to heat.

[For production]

Thereby, the core moves within the heat range within the primary bobbin, and the difference in linear expansion coefficient can be absorbed.

〔Example〕

The present invention will be described below with reference to embodiments shown in the drawings.

In the figure, 1 is a cylindrical primary bobbin made of synthetic resin, and a cylindrical protrusion 1a is integrally provided at the tip thereof. Further, a large diameter portion (stopper portion) lb is formed in the primary pobbin 1 adjacent to the protruding portion 1a, and furthermore, this large diameter portion 1
A winding recess IC is formed on the outer periphery of the intermediate portion of the primary pobbin 1 adjacent to b, and the primary coil 2 is wound in this winding recess IC. A synthetic resin secondary bobbin 3 has a plurality of grooves formed on its outer periphery, and is arranged on the outer periphery of the primary bobbin 1, and a secondary coil 4 is wound in segments in the winding grooves on the outer periphery. Further, a lid portion 3a is formed at one end of the secondary bobbin 3, and a core positioning protrusion 3b that protrudes axially toward the inside of the primary bobbin 1 is integrated into the center of the inner bottom surface of the lid portion 3a. Further, a terminal fixing projection 3c is integrally formed on the outside of the lid portion 3a. 5
A secondary terminal is fixed to the terminal fixing projection 3c, and has a projection 5a to which the high-voltage end of the secondary coil 4 is connected, and a threaded portion 5b to which the high-voltage cord is connected.

Reference numeral 6 denotes a synthetic resin case, in which a partition wall 6a is integrally formed to partition the ignition coil side and the control circuit side, and a mounting stay 6b is integrally formed on the outer wall. Further, a primary terminal connector part 6C and a high voltage cord cylinder part 6d are integrally formed on the bottom wall so as to communicate with the inside of the case 6, and the threaded part 5b of the secondary terminal 5 is connected to the high voltage cord cylinder part 6d. It is placed protruding inside. 7 is a thermosetting resin that is vacuumed and injected into the case 6 and then cured, and the cylindrical protrusion 1a of the primary bobbin 1 is made to protrude into the resin 7 and outside from the open end of the case 6. be.

8 is approximately the same diameter as the inner diameter of the primary bobbin 1b (slightly smaller diameter is better), and has a length shorter than the dimension from the protrusion 1a of the primary bobbin 1 to the tip of the core positioning protrusion 3b of the secondary bobbin 3. This cylindrical core is inserted inside the primary bobbin 1, and the end surface of this core 8 is arranged at approximately the same height as the open end of the case 6. Further, the core positioning protrusion 3b of the secondary bobbin 3 is in contact with the end surface of the core 8, and the core 8 and the primary bobbin 1 are positioned and shifted in the axial direction with respect to the secondary bobbin 3. The distance between the high-voltage side (secondary terminal side) of the coil 4 and the core 8 and primary coil 2 is set so that sufficient withstand voltage can be obtained even when downsized.

Reference numeral 9 denotes a control circuit section for intermittent current flowing through the primary coil 2 of the ignition coil, and is housed in the case 6 separated from the ignition coil side via a partition wall 6a.

Reference numeral 13 denotes a printed circuit board on which each electric circuit component of the control circuit section 9 is mounted, and 14 indicates a printed circuit board 1 that is press-fitted and fixed to the printed circuit board 13 and is arranged in the connector section C for the primary terminal.
Next terminal.

15 is a bushing made of an elastic material such as rubber attached to the outer periphery of the base side of the terminal 14, and the outer periphery is provided with folds 15.
a is integrally formed in a ring shape. This bushing 15 is press-fitted into a circular hole 6e formed at the base of the primary terminal connector part 6c so as to communicate with the inside of the case 6.
This is to prevent the casting resin 7 from leaking from the bottom. .

In the above configuration, the cylindrical protruding portion 1a at one end (open end side) of the primary pobbin 1 located on the open end side of the case 6 projects outward from the open end surface of the case 6. A casting resin 7 is injected into the case 6 from the open end of the case 6, which is the open end of the primary bobbin 1, and is hardened. This results in
The casting resin 7 does not flow into the inside of the primary bobbin 1 from the open end side of the primary bobbin 1. After the casting resin 7 has hardened, the cylindrical protrusion 1a on the open end surface of the primary bobbin 1 is heated in a conical shape as shown by the broken line in the figure, thereby preventing the core 8 from being pulled out.

With this configuration, the core 8 has the primary pobin 1
The core 8 is separated from the casting resin 7 by , and the core 8 can move in the axial direction within the range of the elastic deformation of the heat-fastened portion of the cylindrical protrusion H1a within the primary bobbin 1.
It can absorb stress caused by cold and hot cycles and improve cold and heat resistance.

In the above-described embodiment, the ignition coil and the control circuit are housed in one case 6, but the present invention can also be applied to a case where only the ignition coil is housed in the case 6.

〔Effect of the invention〕

As described above, in the present invention, the core moves within the heat range within the primary bobbin and absorbs the difference in linear expansion coefficient, which prevents the occurrence of cranking of the casting resin due to the cooling/heating cycle. This has the excellent effect of reliably preventing damage to the primary bobbin, etc.

[Brief explanation of drawings]

The figure is a longitudinal sectional view showing an embodiment of the coil of the present invention. 1... Primary bobbin, 1a... Cylindrical protrusion, 2...
Primary coil, 4... Secondary coil, 6... Case, 7
... Thermosetting resin forming the casting resin, 8... Core.

Claims (1)

[Claims] In an ignition coil for an internal combustion engine, a core and primary and secondary coils arranged around the outer periphery of the core are housed in a case, and a casting resin is injected and hardened into the case, and the core is inserted inside. and a primary bobbin having the primary coil wound around its outer periphery, the open end of the primary bobbin protrudes from the open end of the case, and the protruding portion of the primary bobbin is heated to produce internal combustion. Engine ignition coil.