JP2830367B2 - Ignition coil for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ignition coil for an internal combustion engine in which a permanent magnet is provided in a magnetic circuit of an iron core.

[Prior Art] Conventionally, by disposing a permanent magnet that repels the magnetic flux of a primary coil in a magnetic circuit of an iron core, as shown in FIG. A technique for improving the size and reducing the size and weight of the ignition coil has been proposed (JP-A 1-257311, US Pat. No. 4,658,799).
Reference).

FIG. 4 shows the relationship between the magnetizing force of the primary coil and the magnetic flux. When a reverse bias magnetic flux is applied to the magnetic circuit by a permanent magnet, the reverse bias magnetic flux is canceled, and the magnetic flux saturation level of the iron core is further reduced. , The magnetizing force of the primary coil increases, and as a result, the amount of accumulated magnetic energy (the portion indicated by the oblique lines in FIG. 4) increases.

[Problems to be Solved by the Invention] However, when the ignition coil is microscopically viewed, the amount of reverse bias by the permanent magnet differs in each part on the iron core, and the reverse bias amount increases as the distance from the permanent magnet increases and decreases as the distance increases. .
This tendency becomes stronger as the magnetic path length of the iron core around which the primary coil is wound becomes longer. For example, as shown in FIG. 5, the first core 100 having a 1-shape and the second core 101 having a U-shape are formed. In the case where an elongated magnetic circuit is formed, the bias magnetic flux density is measured at a point a near the permanent magnet 103 of the first core 100, a point b farther from the permanent magnet 103, and a point c therebetween, as shown in FIG. As shown in the graph, the measured value at the point a near the permanent magnet 103 is the highest, and the measured value at the point b farther from the permanent magnet 103 is the smallest.

Therefore, if the primary coil is uniformly wound around the outer periphery of the first core 100 and the magnetizing force of the primary coil is uniformly applied in the magnetic circuit, the magnetizing force is large at the point that the amount of reverse bias by the permanent magnet 103 is large. At a point where the amount of reverse bias is insufficient or the amount of reverse bias is small, the magnetization force is excessive and the balance is deteriorated. As a result, there is a problem that the performance of the ignition coil is reduced and the physique is increased, and the heat generated by unnecessary windings is increased and reliability is impaired.

The present invention has been made based on the above circumstances, and an object of the present invention is to provide a magnetizing force in accordance with a reverse bias amount by a permanent magnet to improve performance without impairing reliability. It is to provide an ignition coil.

Means for Solving the Problems In order to achieve the above object, the present invention provides a first core in which a primary coil and a secondary coil are wound around an outer periphery, and the first coil is energized by energizing the primary coil. A second core forming a closed magnetic circuit together with the first core; and a permanent magnet disposed between the first core and the second core so as to repel magnetic flux generated in the first core. In the ignition coil for an internal combustion engine, the primary coil has a relatively larger number of turns per unit length in a portion near the permanent magnet than in a portion far from the permanent magnet. Means.

[Functions and Effects of the Invention] The present invention having the above-described structure is advantageous in that one of the portions close to the permanent magnet is provided.
By making the number of turns per unit length of the secondary coil relatively larger than the number of turns per unit length in a distant portion, it is possible to provide a magnetizing force according to the amount of reverse bias by the permanent magnet. That is, in a portion near the permanent magnet having a large reverse bias amount, the number of turns of the primary coil is large, so that the magnetizing force of the primary coil is large. Since the number of turns is small, the magnetizing force by the primary coil becomes small.

Therefore, in each part of the first core around which the primary coil is wound, the balance between the magnitude of the reverse bias by the permanent magnet and the magnitude of the magnetizing force by the primary coil is improved. As a result, compared to the case where the primary coil is wound uniformly, the amount of accumulated magnetic energy increases, and the performance of the ignition coil can be improved. In addition, heat generation due to unnecessary winding can be suppressed to prevent a decrease in reliability, and increase in physique can be prevented.

Embodiment Next, an ignition coil for an internal combustion engine of the present invention will be described based on an embodiment shown in the drawings.

FIG. 1 is a sectional view of an ignition coil for an internal combustion engine (hereinafter abbreviated as an ignition coil).

The ignition coil 1 is energized by an igniter (not shown).
A non-energized primary coil 2, a secondary coil 3 for generating a high voltage when the primary coil 2 is switched from an energized state to an energized stopped state, and an iron core (described later) forming a magnetic circuit; After being housed in the coil case 4 made of resin, a casting resin such as an epoxy resin is injected and cured to be integrally molded.

The iron core is wound around a primary coil 2 and a secondary coil 3, and is energized when the primary coil 2 is energized to generate a magnetic flux. The first core 5 is closed together with the first core 5. A second core 6 forming a path, and two permanent magnets 7 disposed between both ends of the first core 5 and the second core 6;
As shown in FIG. 1, an elongated square-shaped magnetic circuit is formed.

The first core 5 and the second core 6 are obtained by punching a sheet-like magnetic material (for example, soft iron) having particle orientation by a press or the like, and then laminating a plurality of press-formed products and press-caulking. The core 5 is substantially I-shaped, and the second core 6
Is formed in a substantially U-shape.

The permanent magnets 7 and 8 are disposed so as to repel magnetic flux generated when the first core 5 is excited, that is, so that surfaces adjacent to each other have the same polarity. These permanent magnets 7, 8
Rare earth magnets such as neodymium magnets and rare earth-cobalt magnets that generate a large magnetic force even when they are thin are used.

As described above, in the ignition coil 1 in which the permanent magnets 7 and 8 are provided in the magnetic circuit of the iron core, the amount of reverse bias by the permanent magnets 7 and 8 is large in a portion near the permanent magnets 7 and 8 and In portions farther than 8, the amount of reverse bias is small. This tendency becomes stronger as the magnetic path length becomes longer. For example, in the iron core of the present embodiment, each bias magnetic flux density at points A and B at both ends of the first core 5 near the permanent magnets 7 and 8 and at a point C at the center of the first core 5 farther from the permanent magnets 7 and 8. Is measured, the measured value at the point C is smaller than the measured values at the points A and B as shown in FIG.

Therefore, in the present embodiment, in order to balance the amount of reverse bias in each part of the first core 5 and the magnetizing force of the primary coil 1, the primary coil 2 wound around the outer periphery of the first core 5 has:
On both sides of the first core 5 near the permanent magnets 7 and 8, close winding is performed so that the number of turns per unit length increases, and in the central portion of the first core 5 farther from the permanent magnets 7 and 8 per unit length Sparsely wound so as to reduce the number of turns. In FIG. 1, two primary coils 2 are provided around the outer periphery of the first core 5.
The first layer is wound tightly at about 1/3 both ends of the entire length (coil length) of the primary coil 2 and loosely wound at about 1/3 of the center. Have been.

Thereby, the magnetizing force by the primary coil 2 is large in the portion near the permanent magnets 7 and 8 having a large reverse bias amount, and the magnetizing force by the primary coil 2 is large in the portion far from the permanent magnets 7 and 8 having a small reverse bias amount. Magnetizing force decreases. As a result, in each part of the first core 5, the magnetizing force by the primary coil 2 according to the reverse bias amount by the permanent magnets 7 and 8 can be given, and a well-balanced design can be achieved.

As described above, by changing the number of turns of the primary coil 2 per unit length in accordance with the amount of reverse bias by the permanent magnets 7 and 8, the magnetic energy can be reduced as compared with the case where the primary coil 2 is uniformly wound. And the performance of the ignition coil 1 can be improved.

In addition, heat generation due to unnecessary winding can be suppressed to prevent a decrease in reliability, and an increase in physique can be prevented.

In this embodiment, approximately 1/3 of both ends of the primary coil 2 are densely wound, and approximately 1/3 of the center is loosely wound. The core 5 may be wound so that the winding is gradually changed from close winding to loose winding toward the central portion farther from the permanent magnets 7 and 8 from both ends.

 Next, a second embodiment of the present invention will be described.

 FIG. 3 is a sectional view of the ignition coil 1.

The ignition coil 1 of the present embodiment is a case where the number of the permanent magnets 7 provided in the magnetic circuit is one, and a portion near the permanent magnet 7 (a portion of the primary coil 2 having a total length of about 1/3) has: It is wound tightly so that the number of turns of the primary coil 2 per unit length increases, and is loosely wound so that the number of turns of the primary coil 2 per unit length decreases as the distance from the permanent magnet 7 increases. .

Even when the number of permanent magnets provided in the magnetic circuit is three or more, the densely wound portion and the loosely wound portion may be set in the same manner as in the above embodiment.

Also, as a method of changing the number of turns per unit length,
In addition to setting the densely wound portion and the loosely wound portion shown in the embodiment, for example, the winding height (number of winding layers) of the primary coil 2 may be changed.

In the above-described embodiment, an example in which the first core 5 and the second core 6 form a closed magnetic path having a square shape is shown, but a closed magnetic path or an open magnetic path having another shape may be used. For example, a magnetic circuit composed of a first core having a rod shape and a cylindrical second core disposed on the outer periphery of the first core, a T-shaped first core and a square-shaped second core.
Magnetic circuit consisting of a core.

[Brief description of the drawings]

1 and 2 show a first embodiment of the present invention. FIG. 1 is a cross-sectional view of an ignition coil for an internal combustion engine, and FIG. 2 shows a bias magnetic flux density measured at each point of the first core. FIG. 3 is a sectional view of an ignition coil for an internal combustion engine showing a second embodiment of the present invention, FIG. 4 is a graph showing a relationship between a magnetizing force and a magnetic flux of a primary coil, and FIG. It is the side view of the iron core which forms a circuit, and the graph showing the bias magnetic flux density measured in each point of the iron core. In the drawing, 1 ... Ignition coil for internal combustion engine, 2 ... Primary coil 3 ... Secondary coil, 5 ... First core 6 ... Second core, 7, 8 ... Permanent magnet

Claims (1)

(57) [Claims] 1. A first core having a primary coil and a secondary coil wound around an outer periphery thereof and energized by energizing the primary coil, and a second core forming a closed magnetic path together with the first core. An internal combustion engine ignition coil comprising: a permanent magnet disposed between the first core and the second core so as to repel magnetic flux generated in the first core. Wherein the number of turns per unit length near the permanent magnet is relatively larger than the number of turns per unit length farther away.