JP3369524B2 - Molded ignition coil for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molded ignition coil for an internal combustion engine which supplies a high voltage to generate spark discharge in a spark plug of, for example, an automobile engine. [0002] The present applicant has filed a Japanese Patent Application No. 11-144203.
Endless outer ring core, and a closed magnetic path formed with the outer ring core by traversing the inside surrounded by the outer ring core, and a straight line passing through the concentrically fitted primary and secondary coils. An iron core-coil assembly comprising a center iron core and a high voltage terminal connected to a spark plug are held at the bottom, and the core
A bottomed insulating case that horizontally accommodates the coil assembly therein; and a solidified layer of a thermosetting insulating resin that is cast inside the insulating case and embeds and fixes the core-coil assembly inside. A mold-type ignition coil for internal combustion engines equipped with is proposed. [0003] The ignition coil constructed as described above is often mounted on, for example, an engine of an automobile. In that case, the size of the plug hole and the engine rocker cover are severely restricted, and the size of the ignition coil has been reduced due to the mounting space. In the ignition coil constructed as described above, a center core, an outer ring core, a primary coil, and a secondary coil are housed in a case, and then a thermosetting resin is cast. Cracks are generated in the solidified layer of the thermosetting resin due to the difference in linear expansion coefficient between the iron core and the solidified layer of the thermosetting insulating resin, and it is difficult to prevent the progress of the cracks. When proceeding to the vicinity of terminals and secondary coils, insulation breakdown occurs through cracks,
The ignition coil becomes fatal. SUMMARY OF THE INVENTION The present invention has been developed with the object of solving the above-mentioned problem. The present invention relates to an iron-coil assembly inside an insulation case of a molded ignition coil. A bag-like structure is provided by a shielding wall below the horizontally supported portion, and cracks generated in a solidified layer of the thermosetting insulating resin are isolated by the bag-like structure, whereby the shielding wall of the bag-like structure is formed. Function as a weir to prevent the propagation of cracks to the outside of the bag-shaped structure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the illustrated embodiment, reference numeral 10 denotes an iron core-coil assembly, which is an annular outer ring iron core 13, a center iron core 14 crossing the inside of the outer ring iron core, and an outer periphery of the center iron core. And a secondary coil 12 fitted and supported outside of the primary coil. The outer ring core comprises a C-shaped core 13a and open ends of the C-shaped core. Although it is composed of the I-shaped iron core 13b to be connected, it may be composed of two opposing U-shaped iron cores having a semicircular shape. Further, the iron core composed of the outer ring core and the center core is an E-shaped core having the center arm as the center arm among the three arms, and an I-shaped core which connects the three arms of the E-shaped core at right angles. In any case, an annular outer ring core and a primary, secondary, outer and inner concentrically fitted outer and inner cores are fitted concentrically.
What is necessary is just to have the center iron core which penetrates and supports both the following coils. Between a part of the inner circumference of the outer ring core 13 and one end of the center core 14 facing a part of the inner circumference, a permanent magnet is connected in series with a closed magnetic path formed by the outer ring core and the center core. A magnetic bias is applied by arranging the piece 15 to assemble the ignition coil. During use as a product, the amount of change in the magnetic flux of the iron core is increased when the current flowing through the primary coil is interrupted. It is preferable to increase the voltage of a high voltage that causes sparks in the spark plug to increase the output of the ignition coil. This core-coil assembly 10 has an insulating case formed of a bottomed synthetic resin having an open upper surface 20 'having a downward high-pressure cylinder 21 holding a high-voltage terminal 22 for connecting to a spark plug at the bottom. A flat annular insole 23 on which the outer ring iron core 13 of the iron core coil assembly is horizontally mounted at the middle stage of the inner periphery of the inner core 20 and a primary recessed downward from the inner periphery of the annular insole and supported by the center iron core therein. A high-voltage terminal 22 is held in a high-pressure cylinder 21 that has a recess 24 for accommodating the lower halves of both secondary coils. When molding the insulating case, a primary terminal is attached to the side wall of the insulating case 20 in a penetrating manner by insert molding, and a primary terminal socket 25 surrounding the primary terminal is provided outside the side wall at the same time. In the recess 24 of the insulating case 20, a shielding wall which stands upright from the bottom of the case and whose upper end is in contact with or close to the end of the center iron core 14 projecting outward from one end of both the primary and secondary coils. 26 is formed, and a bag-like structure 27 is formed inside the depression 24. In the illustrated embodiment, the upper end of the shielding wall 26 is in contact with or close to the end of the center core (inside of the permanent magnet piece 15), which is in contact with the inner circumference of the outer ring core 13 via the permanent magnet piece 15. A thermosetting insulating resin such as an epoxy resin is cast into the inside of the insulating case 20 including the bag-like structure portion 27, and a solidified layer 28 of the resin is used to cast the core-coil assembly 10
Is fixed and insulated. As described above, according to the present invention, the thermosetting resin caused by the difference in linear expansion coefficient between the solidified layer 28 of the thermosetting resin and the center iron core 14 and the outer ring iron core 13. The cracks X generated in the solidified layer of the above are dropped into the bag-like structure portion 27 disposed in the insulating case 20, so that the progress of the cracks X can be prevented by the shielding wall 26. For this reason, there is no concern about the dielectric breakdown of the ignition coil caused by the crack X generated in the solidified layer of the thermosetting resin, and a highly reliable product can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing a state in which a crack has occurred in an ignition coil according to an embodiment of the present invention. FIG. 2A is a plan view of an insulating case of the ignition coil of the above, and FIG. 2B is a cross-sectional view taken along line bb of FIG. FIG. 3 is an exploded perspective view of an iron core-coil assembly. [Description of Signs] 10 Iron core-coil assembly 11 Primary coil 12 Secondary coil 13 Outer ring iron core 14 Center iron core 20 Insulating case 21 High pressure cylinder 22 High voltage terminal 23 Annular middle bottom 24 Depression 25 Primary terminal socket 26 Shielding wall 27 Bag-shaped structure 28 Solidified layer of insulating resin X Crack

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Takahiro Kamata 2-1-26-1 Tsutodori, Nada-ku, Kobe-shi, Hyogo Inside Hanshin Electric Co., Ltd. (56) References JP-A-4-206511 (JP, A) Kaihei 4-77220 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01F 38/12 F02P 15/00 303

Claims (1)

(57) [Claim 1] An endless outer ring core and a closed magnetic path are formed with the outer ring core so as to cross the inside surrounded by the outer ring core,
An iron core-coil assembly comprising a linear center iron core which penetrates and supports both primary and secondary coils fitted concentrically, and a high voltage terminal connected to a spark plug is held at a bottom portion, A bottomed insulating case for housing the assembly horizontally therein, and a solidified layer of a thermosetting insulating resin cast inside the insulating case and embedding and fixing the core-coil assembly therein. In the molded ignition coil for an internal combustion engine provided, a bag-like structure portion is provided by a shielding wall below a portion where the iron core coil assembly is horizontally supported inside the insulating case, and the solidified layer of the thermosetting insulating resin is provided. A molded ignition coil for an internal combustion engine, wherein generated cracks are isolated by the bag-shaped structure so as to prevent the crack from spreading outside the bag-shaped structure.