JPH0418716A - Ignition coil for internal combustion engine - Google Patents

Abstract

PURPOSE:To increase the quantity of stored magnetic energy, and to improve the efficiency of ignition coil by a method wherein the number of turns per unit length of the primary coil of the part close to a permanent magnet is relatively made larger than the number of turns per unit length of the part on the further side from the permanent magnet. CONSTITUTION:The primary coil 2, to be wound around the outer circumference of a first core 5, is closely wound in such a manner that the number of turns per unit length becomes larger on both side plates of the first core 5 which is located close to permanent magnets 7 and 8, and the coil 2 is coarsely wound in such a manner that the number of turns per unit length becomes smaller on the center part of the first core 5 which is located further from the permanent magnets 7 and 8. As above-mentioned, by changing the number of turns of the primary coil 2 per unit length in proportion to the amount of inverted bias by the permanent magnets 7 and 8, the efficiency of ignition coil 1 is improved by increasing the quantity of accumulation of magnetic energy when compared with the case where the primary coil 2 is uniformly wound. Also, the deterioration of reliability can be prevented by suppressing the generation of heat on the unnecessary winding, thus obtaining a slim ignition coil.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ignition coil for an internal combustion engine in which a permanent magnet is arranged in a magnetic circuit of an iron core.

[Prior Art] Conventionally, by arranging a permanent magnet that repels the magnetic flux of the primary coil in the magnetic circuit of the iron core, as shown in Fig. 4,
Improving ignition performance by increasing the amount of magnetic energy stored - 11
, and techniques for reducing the size and weight of ignition coils have been proposed (Japanese Unexamined Patent Publication No. 1-257311, U,
S, P, 46J 8799'': see publication).

Figure 4 shows the relationship between the magnetizing force and the magnetic flux of the primary coil. By applying a reverse bias magnetic flux by a permanent magnet to the magnetic circuit, the reverse bias magnetic flux is canceled out, and the iron core By applying magnetic flux until the magnetic flux saturation level is reached, the magnetizing force by the primary coil increases, and as a result, the amount of stored magnetic energy (the shaded area in FIG. 4) increases.

[Problem to be solved by the invention] However, when looking at the ignition coil microscopically, the amount of reverse bias due to the permanent magnet differs in each part on the iron core, and the closer to the permanent magnet the larger the amount of reverse bias is, and the farther away from the permanent magnet, the smaller the amount of reverse bias. This tendency becomes stronger as the magnetic path length of the core around which the primary coil is wound becomes longer.For example, as shown in FIG. 101, when measuring the bias magnetic flux density at point a near the permanent magnet 103 of the first core 100, point b farther from the permanent magnet 103, and point 0 in between,
As shown in the graph of FIG.
The measured value at point b is the highest, and the measured value at point b, which is farther from the permanent magnet 103, is the smallest.

Therefore, if the primary coil is evenly wound around the outer circumference of the first core 100 and the magnetizing force of the primary coil is uniformly applied to the magnetic circuit, the magnetization If the force is insufficient, or if the amount of reverse bias is small, the magnetizing force may be excessive, resulting in poor balance. As a result, the performance of the ignition coil deteriorates, the size of the ignition coil increases, and the heat generated by unnecessary windings increases, which impairs reliability. It was...

The present invention has been made based on the above circumstances, and its purpose is to improve performance without impairing reliability by providing a magnetizing force according to the amount of reverse bias by a permanent magnet. An object of the present invention is to provide an ignition coil for an internal combustion engine.

[Means for Solving the Problems] In order to achieve the above object, the present invention has a primary coil and a secondary coil wound around the outer periphery, and a primary coil that is excited when the primary coil is energized. a second core that forms a closed magnetic path together with the first core; and a second core that is disposed between the first core and the second core so as to repel the 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 close to the permanent magnet than in a portion farther from the permanent magnet. as a technical means.

[Function and Effects of the Invention] The present invention, which consists of a 1-magnet structure,
The number of turns per medium length of the next coil is 111 in the far part.
By increasing the number of turns per length,
A magnetizing force corresponding to the amount of reverse bias by the permanent magnet can be applied. In other words, in the part near the permanent magnet with a large amount of reverse bias, the magnetizing force of the primary coil is large due to the large number of turns of the primary coil, and in the part far from the permanent magnet with a small amount of reverse bias, the magnetizing force of the primary coil is large. The smaller the number of turns, the smaller the magnetizing force by the primary coil.

Therefore, in each part of the first core around which the primary coil is wound, the balance between the magnitude of the reverse bias amount due to the permanent magnet and the magnitude of the magnetizing force due to the primary coil is improved. As a result, compared to the case where the secondary coil is wound uniformly, the amount of magnetic energy stored increases, and the performance of the ignition coil can be improved to 4.

In addition, it is possible to suppress heat generation due to unnecessary windings, thereby preventing problems in reliability, and it is also possible to improve the physique.

[Example] Next, an internal combustion R-opening ignition coil of the present invention will be described based on an example shown in the drawings.

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

The ignition coil 1 includes a primary coil 2 that is switched between energized and de-energized by an igniter (not shown), and a secondary coil 3 that generates a high voltage when the primary coil 2 switches from an energized state to a de-energized state. It consists of an iron core (described later) that forms a magnetic circuit, and after being housed in a resin coil case 4, it is integrally molded by injecting and hardening a casting resin such as epoxy resin.

The iron core has a primary coil 2 and a secondary coil 3 wound around its outer periphery, and a first core 5 which is excited and generates magnetic flux when the primary coil 2 is energized, and a closed magnet together with the first core 5. a second core 6 forming a path, and two permanent magnets 7.8 disposed between both ends of the first core 5 and the second core 6;
As shown in FIG. 1, it forms an elongated, square-shaped magnetic circuit.

The first core 5 and the second core 6 are each made by punching a thin plate-like magnetic material (for example, soft iron) with oriented particles using a press, and then stacking a plurality of press-formed products and pressing them together. Thus, the first core 5 is shaped like a letter ■, and the second core 6
is formed into a substantially U-shape.

The permanent magnets 7.8 are arranged so as to repel the magnetic flux generated when the first core 5 is excited, that is, so that their adjacent surfaces have the same polarity. This permanent magnet 7.8 is a rare earth neodymium magnet that generates a large magnetic force even though it is thin.
Cold class magnets such as cobalt magnets are used.

1, in the ignition coil 1 in which the permanent magnet 7.8 is arranged in the magnetic circuit of the iron core, the amount of reverse bias due to the permanent magnet 7.8 is large in the part near the permanent magnet 7.8, and the permanent magnet The amount of reverse bias becomes small in a portion farther than 7.8. This tendency becomes stronger as the magnetic path length becomes longer. For example, in the iron core of this embodiment, each bias magnetic flux density at points A and B at both ends of the first core 5 near the permanent magnet 7.8, and at point 0 at the center of the first core 5 far from the permanent magnet 7.8. When measured, the measured value at point 0 is smaller than the measured values at points A and B, as shown in FIG.

Therefore, in this embodiment, in order to balance the amount of reverse bias in each part of the first core 5 and the magnetizing force by the primary coil 2, the primary coil 2 wound around the outer circumference of the first core 5 or the permanent The parts on both sides of the first core 5 near the magnet 7.8 are tightly wound to increase the number of turns per unit length, and the central part of the first core 5 farther from the permanent magnet γ,8 has a large number of turns per unit length. It is loosely wound to reduce the number of turns. In addition, in FIG. 1, the primary coil 2 is wound in two layers around the outer periphery of the first core 5, and the second layer is the entire length of the primary coil 2 (
Approximately 1/3 of each end side of the coil length is tightly wound, and approximately 1/3 of the center is loosely wound.

As a result, the magnetizing force of the primary coil 2 is large in the part near the permanent magnet 7.8 with a large amount of reverse bias, and the magnetizing force of the primary coil 2 is large in the part far from the permanent magnet 7.8 with a small amount of reverse bias. Magnetizing force becomes smaller. As a result, in each part of the first core 5, the magnetizing force by the primary coil 2 can be applied in accordance with the amount of reverse bias by the permanent magnet 7.8, resulting in a well-balanced design.

In this way, the number of turns of the primary coil 2 per unit length is
By changing the amount of reverse bias caused by the permanent magnet 7.8, compared to the case where the primary coil 2 is wound uniformly,
The performance of the ignition coil 1 can be improved by increasing the amount of stored magnetic energy.

In addition, it suppresses heat generation due to unnecessary windings, resulting in low T-
It is possible to prevent ', as well as to prevent an increase in physique.

In addition, in this embodiment, approximately 1./3 on both ends of the primary coil 2
The portions of the first core 5 are wound tightly, and approximately 1/3 of the center portion is loosely wound. The winding may be gradually changed from close winding to loose winding.

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 this embodiment has one permanent magnet 7 disposed in the magnetic circuit, and in the part near the permanent magnet 7 (1/3 of the total length of the primary coil 2), The primary coil 2 is wound tightly so that the number of turns per unit length increases, and the winding is loosely wound so that the number of turns per unit length of the primary coil 2 decreases as the distance from the permanent magnet 7 increases. There is.

Note that even when three or more permanent magnets are disposed in the magnetic circuit, the densely wound portion and the sparsely wound portion may be set using the same concept as in the embodiment described in -F.

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

In the embodiment described above, an example was shown in which the first core 5 and the second core 6 formed a closed magnetic path in the shape of an opening, but other shapes of open magnetic paths or open magnetic paths may be used. For example, a magnetic circuit consisting of a rod-shaped first core and a cylindrical second core arranged around the first core, a magnetic circuit consisting of a T-shaped first core and a square-shaped second core. circuits etc.

[Brief explanation of the drawing]

Figures 1 and 2 show a first embodiment of the present invention. Figure 1 is a cross-sectional view of an ignition coil for an internal combustion engine, and Figure 2 shows the bias magnetic flux density measured at each point of the first core. 3 is a cross-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 the relationship between the magnetizing force and magnetic flux of the primary coil, and FIG. 1 is a side view of an iron core forming a circuit and a graph showing bias magnetic flux density measured at each point of the iron core. In the diagram

Claims (1)

[Claims] 1) A first core around which a primary coil and a secondary coil are wound, and which is excited when the primary coil is energized; and a closed magnetic path is formed together with the first core. An ignition coil for an internal combustion engine, comprising: a second core; and a permanent magnet disposed between the first core and the second core so as to repel the magnetic flux generated in the first core; An ignition coil for an internal combustion engine, wherein the primary coil has a relatively larger number of turns per unit length in a portion close to the permanent magnet than in a portion farther from the permanent magnet.