JP2820034B2 - Ignition coil - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition coil for an internal combustion engine, and more particularly to an improvement in the winding of a primary coil.

[0002]

2. Description of the Related Art As a conventional technique, Japanese Utility Model Laid-Open No. 4-5911 is disclosed.
There is an ignition device for an internal combustion engine described in Japanese Patent No. The ignition coil in which the secondary coil is wound around the primary coil as disclosed in the above publication has a high voltage at both ends when an ignition plug is directly connected to both ends of the secondary coil. It is necessary to increase the distance from the low-pressure body (primary coil) toward both ends.

FIG. 5 is a sectional view of a conventional ignition coil, showing an example for explaining the distance from a low-pressure body. The same components are denoted by the same reference numerals or symbols throughout the drawings. As shown in FIG. 5, a primary coil 51 wound around an insulating primary spool 50 is housed in the coil case 10. The primary coil 51 is wound in, for example, four layers so as to have a uniform thickness and a uniform outer diameter.

[0004] A secondary coil 61 wound around each of the slots 62 of the insulating secondary spool 60 is located on the outer periphery of the primary coil 51. Both ends of the secondary coil 61 are connected to high-voltage terminals 71 and 72 (see FIG. 6), respectively. FIG. 6 is a view showing the appearance of the conventional ignition coil of FIG. The high-voltage terminal 71 is connected via a high-voltage cord, and the high-voltage terminal 72 is connected via a high-pressure joint 100 to a spark plug (not shown), as shown in FIG. For example, in the case of four cylinders, two ignition coils are used.

When one of the ignition plugs is ignited, a high-pressure compressed air-fuel mixture is contained in an air gap (about 1 mm) of the ignition plug, so that a high voltage, for example, 20 to 30 kV is required at the time of ignition. Become. Since the other spark plug is at a low pressure at this time, it discharges at a low voltage. For this reason, the voltage of the secondary coil has a gradient such that one of the two ends has a high voltage and the other has a low voltage. As the high pressure is alternately switched between the two spark plugs, a high voltage / low voltage is repeatedly generated at both ends of the secondary coil, and the gradient is reversed each time.

[0006] Regarding the insulation of the secondary coil in the generation of voltage, first, the slot 62 of the secondary spool 60 near both ends is made small, and the number of turns of the secondary coil 61 entering the secondary spool 60 is reduced so that the number of turns near the both ends is reduced. The potential difference between the slots is suppressed to prevent dielectric breakdown between adjacent slots 62. Furthermore, in order to keep the slots 62 at both ends of the secondary spool away from the primary coil, as shown in a partially enlarged view of both ends of the secondary coil, the slots near both ends of the secondary spool are raised by "L" to increase the thickness of the insulating layer. Thus, dielectric breakdown with the primary coil is prevented.

The inner core of the primary spool 50 has a laminated core 31
And 32 pass through, and a permanent magnet 40 is installed in a magnetic path between the cores 31 and 32. This permanent magnet 40
Thereby, the saturation of the iron core is reduced. A power transistor unit 80 including an ignition control circuit connected to the connector 20 and sealed in a resin package is housed in the coil case 10. The power transistor unit 80 intermittently supplies current to the primary coil 51. Is shed. The internal components of the case 10 are injected and cured by a casting resin 90 such as an epoxy resin (see FIG. 2), and are integrally molded (indicated by v in the figure).

[0008]

In the above ignition coil,
In order to improve the insulation strength between the primary coil and the secondary coil, the winding space of the secondary coil is reduced by the height of the slot near both ends of the secondary spool, which is disadvantageous for downsizing the coil. There is a point. Further, the measures of the above-mentioned prior art alone were not enough to meet the demand for a higher output voltage.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an ignition coil capable of achieving an improvement in insulation strength between a primary coil and a secondary coil with a simple configuration in view of the above problems. It is a further object of the present invention to provide an ignition coil capable of preventing the winding from being distorted and reliably forming the winding outer diameter with a step when forming the winding outer diameter of the primary coil with a step.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a primary coil wound around a primary spool and a secondary coil wound around an outer periphery of the primary coil. In an ignition coil having a secondary coil and both ends of the secondary coil being connected to an ignition plug, the number of winding layers of both ends of the primary coil opposed to both ends of the secondary coil is the same as that of the secondary coil. The number of windings of the central coil of the primary coil facing the central part excluding both ends of the secondary coil is smaller.

The outer peripheral surface of the primary spool has a larger diameter at both ends than at the center of the outer peripheral surface, a step is provided at a boundary between both ends and the central portion, and the outer periphery is wound around the both ends. The outer circumference of the primary coil may be smaller in diameter than the outer circumference of the primary coil wound around the central portion. Furthermore, it has a primary coil wound on a primary spool and a secondary coil wound on a secondary spool provided on the outer periphery of the primary coil, and both ends of the secondary coil are connected to a spark plug. In the primary coil, the primary spool has a small-diameter portion and a large-diameter portion formed on an outer peripheral surface thereof, and the large-diameter portion faces an end of a secondary coil to which a spark plug is connected, and has a small diameter portion. The number of windings of the primary coil is larger than the number of windings of the primary coil in the large diameter portion, and the outer periphery of the primary coil facing the end of the secondary coil to which the ignition plug is connected is located in another part of the secondary coil. It is formed smaller in diameter than the outside of the opposed primary coil.

[0012]

According to the ignition coil according to the first aspect of the present invention,
The number of winding layers of both ends of the primary coil facing both ends of the secondary coil is smaller than the number of winding layers of the center coil of the primary coil facing the center excluding both ends of the secondary coil. Thereby, the insulation strength between the primary coil and the secondary coil can be improved with a simple configuration.

Further, the outer peripheral surface of the primary spool is formed so that both ends are larger in diameter than the central portion of the outer peripheral surface, a step is provided at a boundary between both ends and the central portion, and the primary spool is wound around both ends. By making the outer circumference of the primary coil smaller in diameter than the outer circumference of the primary coil wound in the center, when forming the outer diameter of the winding of the primary coil with a step, it is possible to prevent winding collapse. Become.

Further, according to the ignition coil of the present invention, the primary spool has a small diameter portion and a large diameter portion formed on the outer peripheral surface thereof, and the large diameter portion is connected to the ignition plug. Facing the end of the secondary coil, and facing the end of the secondary coil to which the ignition plug is connected by making the number of windings of the primary coil in the small diameter part larger than the number of windings of the primary coil in the large diameter part The outer circumference of the primary coil is formed to have a smaller diameter than the outside of the primary coil facing the other part of the secondary coil, so that the winding is distorted due to the difference in the number of winding layers of the primary coil while ensuring insulation for the secondary coil. Can be prevented.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of an ignition coil according to an embodiment of the present invention, schematically illustrating winding of a primary coil and a secondary coil, and FIG. 2 is a diagram illustrating another cross section of the ignition coil of FIG. It is. The ignition coil according to the embodiment of the present invention is an improvement based on the ignition coil of FIG. 5, and the components different from the ignition coil of FIG. 5 are a primary coil 151, a secondary spool 160, and a secondary spool 160. The coil 161.

In the primary coil 151, the number of windings at both ends is smaller than the number of windings at the center.
The number of winding layers is four at the center. Along with this, the insulation thickness of the secondary spool is made uniform at both the center and both ends, and it is possible to avoid providing a raised portion in the slots at both ends as in the conventional case. In other words, the distance between the secondary coil and the primary coil, with the number of windings of the primary coil at both ends being smaller than the central part, and the outer diameter of the primary coil being smaller at both ends than the central part, It is larger at both ends than at the center. For this reason, according to the configuration of this embodiment, it is easy to secure insulation against a high voltage generated at both ends with a relatively simple configuration. A conventional secondary spool may be used.

FIG. 3 is a partially broken view for explaining in detail the winding of the primary coil 151 of FIG. The primary coil 151 is
It has a large diameter portion 151a at the center and small diameter portions 151b at both ends. The primary coil 151 is wound on the first layer to the end of the winding width of the primary spool 50, and is folded. The second layer is folded on the way without winding to the end, and the third layer is folded on the way without winding to the end. After that, there are four layers up to the turning point of the second layer, and then there are two layers with two steps. As a result, only the large diameter portion 151a at the center of the primary coil 151 is wound in four layers, and the small diameter portions 151b at both ends are wound in two layers. That is,
The winding height of the small diameter portions 151b at both ends is lower by two layers than the large diameter portion 151a at the center. Therefore, FIGS.
As shown in (2), the distance between the both ends of the secondary coil where the voltage is high and the primary coil can be secured with respect to the central part by the distance corresponding to two layers of the primary coil.

FIG. 4 shows a primary coil 151 according to another embodiment.
It is a partially broken view explaining winding. As shown in this figure,
At the center of the primary spool 50, a concave portion 50a is provided as a small diameter portion for one layer of the winding, and the primary coil 151 is wound in four layers corresponding to the concave portion 50a. In this case, the small-diameter portions 151b at both ends of the primary coil 151 are connected to the central large-diameter portion 151a.
There is only one step in the middle, but due to a step in the middle of the winding provided by the concave portion 50a, the central large-diameter portion 151a
Can be prevented from being broken, and a stable winding can be achieved.

Generally, a small-diameter portion and a large-diameter portion are formed on the outer peripheral surface of the primary spool 50, and a portion closer to the high-voltage output end of the secondary coil is defined as a large-diameter portion, and the primary coil 151 in the small-diameter portion is formed. And the number of windings of the primary coil in the large-diameter portion are set to be smaller on the side closer to the high-voltage output end of the secondary coil, whereby the outer diameter of the primary coil 151 is reduced by the high-voltage output of the secondary coil. It is formed so as to have a smaller diameter nearer the end.

[0020]

As described above, according to the present invention, at both ends of the primary coil opposed to both ends of the secondary coil connected to different ignition plugs, the number of winding layers of the coil is
Since the number of windings is smaller than the number of windings of the central coil, the distance from the secondary coil can be increased and the edge strength can be secured. Furthermore, by providing a small diameter part and a large diameter part on the primary spool,
As described above, even when the number of winding layers of the primary coil is made different, it is possible to prevent winding collapse.

Further, a small-diameter portion and a large-diameter portion are formed on the outer peripheral surface of the primary spool, the large-diameter portion is opposed to an end of a secondary coil to which a spark plug is connected, and the primary coil in the small-diameter portion is formed. The number of winding layers is larger than the number of winding layers of the primary coil in the large-diameter portion, and the outer periphery of the primary coil facing the end of the secondary coil to which the ignition plug is connected faces the other portion of the secondary coil. By being formed with a diameter smaller than the outer circumference of the coil, it is possible to prevent winding collapse due to a difference in the number of winding layers of the primary coil while ensuring insulation for the secondary coil.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an ignition coil according to an embodiment of the present invention, schematically illustrating winding of a primary coil and a secondary coil.

FIG. 2 is a diagram showing another cross section of the ignition coil of FIG. 1;

FIG. 3 is a diagram for explaining winding of a primary coil 151 in FIG. 1 in detail;

FIG. 4 is a diagram illustrating another winding of the primary coil 151 of FIG. 3;

FIG. 5 is a cross-sectional view of a conventional ignition coil, illustrating an example for explaining a distance from a low-pressure body.

FIG. 6 is a diagram showing an appearance of the conventional ignition coil of FIG.

[Explanation of symbols]

 Reference numeral 50: primary spool 151: primary coil 150a: center coil 150b: both end coils 160: secondary spool 161: secondary coil

Claims (3)

(57) [Claims] 1. A primary coil wound around a primary spool, and a secondary coil wound around a secondary spool provided on an outer periphery of the primary coil, and both ends of the secondary coil are spark plugs. In the ignition coil, the number of winding layers of both ends of the primary coil opposed to both ends of the secondary coil is the center of the primary coil opposed to the center excluding both ends of the secondary coil. An ignition coil characterized in that the number of windings is smaller than the number of windings of the partial coil. 2. An outer peripheral surface of the primary spool has a larger diameter at both ends than a central portion of the outer peripheral surface, a step is provided at a boundary between both ends and the central portion, and the outer peripheral surface is wound around the both ends. The ignition coil according to claim 1, wherein an outer periphery of the primary coil has a smaller diameter than an outer periphery of the primary coil wound around the central portion. 3. A primary coil wound around a primary spool, and a secondary coil wound around a secondary spool provided on an outer periphery of the primary coil, and both ends of the secondary coil are spark plugs. In the ignition coil, the primary spool has a small-diameter portion and a large-diameter portion formed on the outer peripheral surface thereof, and the large-diameter portion faces an end of the secondary coil to which the ignition plug is connected, and The number of windings of the primary coil in the small-diameter portion is larger than the number of windings of the primary coil in the large-diameter portion, so that the outer periphery of the primary coil facing the end of the secondary coil to which the ignition plug is connected is the same as the secondary coil. Characterized in that it is formed to have a smaller diameter than the outer circumference of the primary coil facing the portion.