JP2000182858A - Ignition coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable securing of insulation distance between primary and secondary windings, even if the tension of the primary winding causes the inside diameter side of a primary spool to be bent and deformed. SOLUTION: A primary winding 20 wound around a primary side spool 19 made of insulating resin is accommodated within a coil case 11, and a secondary winding 22 wound around a secondary side spool 21 made of the insulating resin is accommodated in the inner peripheral side of the case 11. By taking into the tension of the primary winding 20 into consideration bending and deformation of an inner diameter side of the primary spool 19 are produced, the primary spool 19 is formed to have a convex outer peripheral surface having a central area higher than its other areas. By making such a structure, even if the tension of the primary winding 20 causes bending and deformation of the inner diameter side of the primary spool 19, the outer peripheral surface of the primary spool 19 be coming deformed recessed toward its inner diameter side is prevented, or a recessed deformation toward the inner diameter side can be made smaller than that in prior art. Thereby the insulation distance between the primary winding 20 and secondary winding 22 provided on its inner diameter side is secured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called stick type ignition coil which is mounted in a plug hole of each cylinder of an engine.

[0002]

2. Description of the Related Art Generally, a stick type ignition coil is
The primary winding and the secondary winding wound respectively on two resin-made cylindrical spools having different diameters are concentrically housed in a cylindrical coil case together with a columnar central core. Is filled with an insulating filler material such as epoxy resin to insulate and fix each component in the coil case.

[0003]

The stick type ignition coil of this type is mounted in the plug hole of each cylinder of the engine, so that the outer diameter is restricted by the inner diameter of the plug hole. For this reason, in order to secure a winding space for the winding, the thickness of the spool is reduced and the overall length of the spool is increased. As a result, when the winding is wound on the spool, the spool is bent and deformed to the inner diameter side due to the tension of the winding, and the insulation distance between the primary winding and the secondary winding is reduced, and the insulation is reduced. Properties and durability may be reduced. In other words, the insulation distance between the primary winding and the secondary winding is designed to be the minimum necessary to secure the winding space of the winding, so that the amount of deflection deformation of the spool due to the tension of the winding Appears small (20-1 on the primary side)
Although the bending deformation is about 00 μm), the influence on the insulating property is large.

[0004] The present invention has been made in view of such circumstances, and the object thereof is therefore to provide a primary winding and a secondary winding even when the spool bends and deforms to the inner diameter side due to the tension of the winding. It is an object of the present invention to provide an ignition coil capable of securing an insulation distance between the coils and improving insulation and durability.

[0005]

In order to achieve the above object, the ignition coil according to the first aspect of the present invention takes into consideration the fact that the spool is flexed and deformed to the inner diameter side by the tension of the winding, and the primary and secondary coils are provided. The outer peripheral surface of at least one of the spools on the next side is formed in a convex shape in which the central portion is higher.
In other words, if the outer peripheral surface of the spool is formed in a convex shape in consideration of the amount of bending deformation due to the tension of the winding, the outer peripheral surface of the spool may be deformed to the inner diameter side even if the spool is bent and deformed by the tension of the winding. This prevents deformation to a concave shape on the inside, or reduces the amount of deformation to a concave shape on the inner diameter side as compared with the conventional case. As a result, even if the spool bends and deforms to the inner diameter side due to the tension of the winding, the insulation distance between the primary winding and the secondary winding can be ensured, and the insulation and durability can be improved.

In the case where the outer peripheral surface of the spool is formed in a convex shape, if the inner peripheral surface of the spool is formed in a concave shape in accordance with the shape, the inner peripheral surface of the spool is undercut during molding. In the molding method, a mold (middle pin) for molding the inner peripheral surface of the spool cannot be removed, and molding cannot be performed.

Considering this point, it is preferable that the inner peripheral surface of the spool is formed in a cylindrical surface. With this configuration, the spool having a convex outer peripheral surface can be molded by a relatively simple mold, and the molding cost can be reduced.

In general, a relatively thick copper wire is used for the primary winding to pass a relatively large current, so that the tension of the primary winding is increased and the amount of deflection deformation of the spool on the primary side is relatively large. However, since the secondary winding uses a thin copper wire to increase the number of windings and obtain a high voltage, the tension of the secondary winding is reduced, and the amount of bending deformation of the secondary spool is reduced. Relatively small. Either the primary winding or the secondary winding may be arranged on the outer peripheral side. However, many stick-type ignition coils have a structure in which the primary winding on the low voltage side is arranged on the outer peripheral side.

In consideration of these circumstances, in the structure in which the primary winding is disposed on the outer peripheral side, the outer peripheral surface of the primary side spool located on the outer peripheral side has a convex surface with the central portion being higher. It is good to form in the shape. With this configuration, even when the tension of the primary winding positioned on the outer peripheral side causes the primary spool to be relatively largely bent and deformed to the inner diameter side, the outer peripheral surface of the primary spool is deformed concavely toward the inner diameter side. Or the amount of concave deformation to the inner diameter side becomes smaller than before, and the insulation distance between the primary winding and the inner winding side secondary winding is ensured.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. First, the configuration of the entire ignition coil 10 will be described with reference to FIG. Cylindrical coil case 11
Is formed of an insulating resin, and a connector housing 14 in which a connector pin 13 is insert-molded is assembled by press-fitting or the like in a head case 12 integrally formed at an upper end thereof. An igniter 16 is mounted on a pedestal 15 integrally formed with the connector housing 14, and an ignition signal output from an engine control computer (not shown) is supplied to the igniter 1 via a connector pin 13.
6 is input.

Inside the coil case 11, a columnar center core 18 and a cylindrical outer core 17 are concentrically housed at the center and the outer periphery, respectively. Cylindrical outer core 1
The primary winding 20 wound around a cylindrical primary spool 19 made of an insulating resin is housed on the inner peripheral side of the housing 7. Further, the inner peripheral side of the primary spool 19 is made of an insulating resin made of insulating resin. A secondary winding 22 wound around a cylindrical secondary spool 21 is housed. A terminal plate 25 is attached to the lower end of the secondary spool 21.
One end of the secondary winding 22 is connected.

The center core 18 is housed in the inner diameter of a secondary spool 21 formed in a cylindrical shape with a bottom, and cushion members 23 are provided at upper and lower ends of the center core 18, respectively.
Is addressed. The cushion member 23 is a cushioning material for preventing an excessive stress from acting on the central core 18, and is formed of a heat-resistant elastic material such as a sponge or an elastomer which also serves to prevent magnetostriction. Further, the inside of the coil case 11 and the head case 12 is vacuum-filled with an insulating resin such as an epoxy-based thermosetting resin as the filler 24.

On the other hand, a high-voltage tower 26 is attached to the lower end of the coil case 11 by bonding or the like. At the upper center of the high-pressure tower 26, a terminal cup 28 in which a high-voltage terminal 27 is integrally formed upward is insert-molded or press-fitted, and the high-voltage terminal 27 is pressed against the terminal plate 25 to maintain an electrically conductive state. Have been. When this high-pressure tower section 26 is inserted into a plug hole (not shown) and press-fitted into the upper part of an ignition plug (not shown), a conductive spring 29 locked in a terminal cup 28 causes a terminal of the ignition plug to be connected. , Whereby one end of the secondary winding 22 is electrically connected to the terminal of the ignition plug via the terminal plate 25, the high-voltage terminal 27, the terminal cup 28, and the spring 29.

The stick type ignition coil 10 configured as described above is mounted in the plug hole.
The outer diameter of the coil case 11 is regulated by the inner diameter of the plug hole. Therefore, the primary winding 20 and the secondary winding 22
The primary and secondary spools 19, 21 have a thickness of, for example, 0.4 to 1.0 mm in order to secure a winding space of
The length of the spools 19 and 21 is increased, for example, to about 50 to 150 mm. As a result, when windings 20 and 22 are wound around spools 19 and 21, spools 19 and 21 are wound by the tension of windings 20 and 22.
Is bent and deformed toward the inner diameter side.

Generally, since the primary winding 20 uses a relatively thick copper wire to pass a relatively large current, the tension of the primary winding 20 is relatively large, for example, 1 to 1.
2 kg. As a result, the amount of bending deformation of the primary spool 19 due to the tension of the primary winding 20 is, for example, 20 to
It is about 100 μm.

On the other hand, since the secondary winding 22 uses a thin copper wire to increase the number of turns and obtain a high voltage, the tension of the secondary winding 22 is relatively small. It is about 10 to 100 g. Therefore, the amount of bending deformation of the secondary spool 21 is relatively small, for example, several μm.
About 10 μm.

In view of this, in the present embodiment, considering that the primary spool 19 in which the amount of bending deformation due to the winding tension is large is arranged on the outer peripheral side, as shown in FIG. 2 or FIG. The outer peripheral surface of 19 is formed in a convex shape in which the central portion is higher. For example, as shown in FIG. 2A, the outer peripheral surface of the primary spool 19 is formed in a curved convex shape such as a barrel shape or a drum shape, or as shown in FIG. The outer peripheral surface of the spool 19 may be formed in a shape having a trapezoidal vertical cross section (a shape having a cylindrical surface at the center). The amount of protrusion of the outer peripheral surface of the primary spool 19 is determined by the amount of bending deformation (for example, 20 to 10) due to the tension of the primary winding 20.
0 [mu] m), for example, it may be set to 20 to 200 [mu] m. 2 and 3, the protrusion amount is exaggerated for easy understanding of the protrusion state of the outer peripheral surface of the primary spool 19. Further, at the time of molding, the spool 19,
The inner peripheral surfaces of the spools 19 and 21 are formed as cylindrical surfaces so that the inner peripheral surface of the spool 21 is not undercut.

In the above-described embodiment, the outer peripheral surface of the primary spool 19 is fixed in consideration of the fact that the primary spool 19 is relatively largely bent and deformed toward the inner diameter side by the tension of the primary winding 20 located on the outer peripheral side. 2 (b) and 3 (b), the primary spool 20 is relatively largely bent and deformed toward the inner diameter side by the tension of the primary winding 20, as shown in FIGS. 2 (b) and 3 (b). Even
The outer peripheral surface of the primary side spool 19 is prevented from being concavely deformed toward the inner diameter side, or the amount of concavely deformed toward the inner diameter side is smaller than before, so that the primary winding 20 and the secondary winding on the inner diameter side are reduced. An insulation distance from the wire 22 is ensured. This allows
The insulation between the primary winding 20 and the secondary winding 22 is improved,
The durability of the ignition coil 10 is improved. Moreover, since the inner peripheral surface of the primary spool 19 is formed as a cylindrical surface, the inner peripheral surface of the spool 19 is not undercut during molding, and the spool 10 having a convex outer peripheral surface is formed by a relatively simple mold. Thus, the molding cost can be reduced.

In the above embodiment, the primary spool 1
Although only the outer peripheral surface of the secondary spool 21 is formed in a convex shape in which the central portion is higher, the outer peripheral surface of the secondary spool 21 may be formed in a convex shape in which the central portion is higher. With this configuration, even if the secondary spool 21 is bent and deformed to the inner diameter side due to the tension of the secondary winding 22, the outer peripheral surface of the secondary spool 21 is prevented from being concavely deformed to the inner diameter side, Alternatively, the amount of deformation to the concave side on the inner diameter side becomes smaller than before, the distance between the secondary winding 22 and the primary winding 20 is kept almost constant, and the electrical characteristics are improved.

In the above embodiment, the primary winding 20
The (primary spool 19) is arranged on the outer peripheral side of the secondary winding 22 (secondary spool 21). On the contrary, the secondary winding 22 (secondary spool 21) is connected to the primary winding 20. (The primary spool 19) may be arranged on the outer peripheral side. In this case, the outer peripheral surface of only the secondary spool 21 may be formed in a convex shape in which the central portion is higher.

Further, a groove extending in the vertical direction may be formed on the outer peripheral surface of the spool formed in a convex shape, and the filler 24 may be injected into the inner peripheral side of the winding by this groove.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an ignition coil showing one embodiment of the present invention.

FIG. 2 shows a first embodiment of a primary spool,
(A) is a partial cross-sectional view schematically showing the shape of the primary spool before the primary winding is wound, and (b) is a schematic view showing the shape of the primary spool after the primary winding is wound. It is a partial sectional view.

FIG. 3 shows a second embodiment of the primary spool,
(A) is a partial cross-sectional view schematically showing the shape of the primary spool before the primary winding is wound, and (b) is a schematic view showing the shape of the primary spool after the primary winding is wound. It is a partial sectional view.

[Explanation of symbols]

Reference Signs List 10: ignition coil, 11: coil case, 17: outer peripheral core, 16: igniter, 18: central core, 19: primary spool, 20: primary winding, 21: secondary spool, 2
2 ... secondary winding, 24 ... filler.

Claims (3)

[Claims] 1. An outer peripheral surface of at least one of a primary side and a secondary side in an ignition coil in which a primary winding and a secondary winding are respectively wound around a resin-made cylindrical spool and arranged concentrically. Characterized by being formed in a convex shape in which the central portion side is higher. 2. The ignition coil according to claim 1, wherein the inner peripheral surface of the spool is formed as a cylindrical surface. 3. The primary winding is arranged on the outer peripheral side of the secondary winding, and the outer peripheral surface of the primary spool is formed in a convex shape in which a central portion is higher. The ignition coil according to claim 1.