JPH0464207A - Ignition coil for internal combustion engine - Google Patents

Abstract

PURPOSE:To reduce cost by using a magnet blank having excellent demagnetization- resistant characteristics as a section having a large demagnetizing field applied at the time of the operation of a primary coil and employing a magnet blank having inferior demagnetization-resistant characteristics as a section having a small demagnetizing field applied at the time of the operation of the primary coil. CONSTITUTION:Demagnetizing fields are applied to permanent magnets 5 disposed in the magnetic circuit of a core 2 at the operation of a primary coil 3, but the outer circumferential side is made smaller than the inner circumferential side in the magnitude of the demagnetizing fields applied to the permanent magnets 5 because the reluctance of the outer circumferential side of the core 2, a magnetic path of which is lengthened, is made larger than that on the inner circumferential side of the core 2 having a short magnetic path. Consequently, a magnet blank 5a having excellent demagnetization-resistant characteristics is used to the inner circumferential side section having the large demagnetizing field applied, and a magnet blank 5b having inferior demagnetization-resistant characteristics is employed to the outer circumferential side section having the small demagnetizing field applied. Accordingly, manufacturing cost as the whole permanent magnets 5 can be reduced.

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 disposed within a magnetic circuit of an iron core.

[Prior Art] Conventionally, in ignition coils for internal combustion engines, in order to improve ignition performance, permanent magnets that repel the magnetic flux of the primary coil are arranged in the magnetic circuit of the iron core to reduce the amount of magnetic energy. Techniques have been proposed to increase the size of the
57311, JP-A-2-37705)
.

[Problems to be Solved by the Invention] However, a demagnetizing field is applied to the permanent magnet disposed in the magnetic circuit of the iron core when the primary coil is operated, but a magnetic field exceeding the knick point of the permanent magnet is applied. As a result, the permanent magnet undergoes irreversible demagnetization, leading to a decrease in coil performance.

This tendency becomes more pronounced as the temperature increases, so it is necessary to use a magnet material with excellent demagnetization resistance for the permanent magnet, resulting in an increase in the cost of the permanent magnet.

The present invention was made based on the above circumstances, and an object of the present invention is to provide an ignition coil for an internal combustion engine in which the cost of permanent magnets is reduced.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes an iron core that forms a closed magnetic circuit by providing an air gap in a part thereof, and a magnetic core that is wound around the iron core and energized. A secondary coil is wound around the iron core and generates an electromotive force as the primary current flows through the primary coil. A permanent magnet is magnetized to repel the magnetic flux generated in the iron core when energized, and the permanent magnet is made of a magnet material with poor demagnetization resistance and a magnet material with excellent demagnetization resistance. A magnet material with poor demagnetization properties is used in a part where the demagnetizing field is small when the primary coil is operated, and a magnet material with excellent demagnetization resistance is used in a part where the demagnetizing field is large when the primary coil is operated. The technical means used in the part.

[Actions and Effects of the Invention] The present invention having the above structure has the following actions and effects.

A demagnetizing field is applied to the permanent magnet inserted into the air gap of the iron core when the primary coil operates, but the magnitude of the demagnetizing field is limited to the short part of the magnetic path (inside the closed magnetic path) in the magnetic circuit of the iron core. The longer part of the magnetic path (the outer periphery of the closed magnetic path (
Ill) is smaller.

Therefore, it is necessary to use a magnet material with excellent demagnetization resistance for the short part of the magnetic path, that is, the part where the large demagnetizing field is applied when the primary coil operates, or to A magnet material with poor demagnetization resistance can be used for the portion where the demagnetizing field applied during operation is small.

This magnet material with poor demagnetization resistance can be manufactured more cheaply than magnet materials with better demagnetization resistance, so it is less expensive to manufacture permanent magnets than if only magnet materials with excellent demagnetization resistance are used. The manufacturing cost of the magnet as a whole can be reduced.

[Example] Next, an ignition coil for an internal combustion engine according to 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.

The ignition coil 1 of this embodiment includes an iron core 2 that forms a closed magnetic path by providing an air gap in a part of the magnetic circuit, a primary coil 3 and a secondary coil 4 that are wound around the iron core 2, and the iron core 2.
It is housed in a resin coil case 6, and is partially molded by injecting and hardening a casting resin 7 such as epoxy resin.

The iron core 2 includes a first core 2a around which a primary coil 3 and a secondary coil 4 are wound, and which is excited when the primary coil 3 is energized, and forms an annular body together with the first core 2a. Second core 2 that closes the magnetic flux generated in the first core 2a
It consists of b.

The primary coil 3 is wound around a primary spool 8 fitted around the outer periphery of the first core 2a, and is switched between energization and de-energization by an igniter (not shown).

The secondary coil 4 is wound around a secondary spool 9 fitted around the outer periphery of the primary spool 8, and generates a high voltage when the primary coil 3 is switched from an energized state to a non-energized state.

The permanent magnet 5 is disposed within the air gap formed between the first core 2a and the second core 2b so as to repel the magnetic flux generated in the first core 2a by energization of the primary coil 3. .

In addition, in the figure, number 10 is a connector connected to the igniter, and number 11 is a high voltage terminal to which a high voltage cord (not shown) is connected.

A demagnetizing field is applied to the permanent magnet 5 disposed in the magnetic circuit of the iron core 2 when the primary coil 3 is operated. Since the magnetic resistance is larger on the outer circumference side, the magnitude of the demagnetizing field applied to the permanent magnet 5 is smaller on the outer circumference side than on the inner circumference side.

Therefore, in this embodiment, as shown in Fig. 2 (showing the demagnetizing characteristics of the magnet), the inner circumferential portion where the applied demagnetizing field is large is made of magnet material 5at (which has excellent demagnetizing resistance characteristics). The magnet material 5b, which has poor demagnetization resistance, was used in the outer circumferential portion where the applied demagnetizing field was small.

This magnet material 5b with poor demagnetization resistance can be manufactured at a lower cost than the magnet material 5a with excellent demagnetization resistance. Therefore, when the permanent magnet 5 is manufactured only with the magnet material 5a with excellent demagnetization resistance. Therefore, the manufacturing cost of the permanent magnet 5 as a whole can be reduced.

By the way, when a magnet with a general rectangular cross section is magnetized, as shown by the broken line in Figure 3, there is a neutral plane at the equal road shoulder from the upper and lower magnetized planes, and the sides of the magnet also have 5 neutral planes. They are magnetized to different poles with each other in between.

When magnets magnetized in this way are arranged on the same plane in a magnetic circuit, as shown in Figure 3, the sides of adjacent magnets have the same polarity across their neutral planes. Since the comrades face each other, their magnets repel each other, making it difficult to assemble them. As a result, it becomes necessary to bond each magnet or to form four parts for inserting the magnets into the iron core 2, which increases the cost.

However, when the side surfaces of adjacent magnets are machined diagonally with respect to the magnetization direction and then magnetized, as shown in Figure 4, the diagonally machined side surfaces become one of the magnetized surfaces (IJ!! It is magnetized to have the same polarity as the surface that forms an obtuse angle with the first surface.

Therefore, after the above-mentioned magnet materials 5a and 5b have their side surfaces in contact with each other obliquely processed with respect to the magnetization direction, they are magnetized by a magnetization coil 12, as shown in FIG.

At this time, in order to change the polarity of magnetization on the sides of the magnet material 5a and the magnet material 5b, the magnet material 5a and the magnet material 5b
and are placed upside down and magnetized.

Note that the number of sheets to be magnetized to -degrees is appropriately determined depending on the capacity of the magnetizing coil.

As a result, the contact surfaces of the magnet material 5a and the magnet material 5b are magnetized to different polarities, and even if they are arranged on the same plane, the repulsion of the magnets can be reduced.

Therefore, as described above, it is possible to easily assemble the iron core 2 without gluing the magnet teeth or forming a recess for inserting the magnet, and the work can be carried out without increasing costs. can improve sex.

FIG. 6 shows a second embodiment of the invention.

In the ignition coil 1 of this embodiment, the iron core 2 forming a closed magnetic path consists of a T-shaped first core 2a and a mouth-shaped second core 2b. An air gap is formed between the upper end portion) and the inner peripheral surface of the second core 2b.

In this iron core 2, the first core 2a is arranged inside the center of the second core 2b, and two closed magnetic paths are formed.

Therefore, since the magnetic path passing through the center of the permanent magnet 5 disposed in the air gap is longer than the magnetic path passing through both ends of the permanent magnet 5, the demagnetizing field applied to the permanent magnet 5 is The center portion of the magnet 5 is smaller than both ends.

Therefore, in this embodiment, the permanent magnet 5 is divided into three parts, and a magnet material 5b with poor demagnetization resistance is used in the center of the permanent magnet 5, and magnets with excellent demagnetization resistance are used in both ends of the permanent magnet 5. Material 5a was used.

In addition, each magnet material 5a, 5b is 4' magnetized after machining the mutual contact surfaces diagonally, as shown in FIG.
The contact surfaces of each magnet material 5a, 5b can be magnetized to any polarity.

As a result, as in the first embodiment, the cost of the permanent magnet 5 can be reduced, and its assembly is easy to assemble.

[Brief explanation of drawings]

1 to 5 show a first embodiment of the present invention, in which FIG. 1 is a cross-sectional view of an ignition coil for an internal combustion engine, FIG. 2 is a graph showing the demagnetization characteristics of a magnet, and FIG. 3 is a graph showing the demagnetization characteristics of a magnet. 4 is an explanatory diagram showing the black magnetic state of the magnet, FIG. 5 is an explanatory diagram showing the method of magnetizing the magnet, and FIGS. 6 and 7 are diagrams showing a second embodiment of the present invention. FIG. 6 is a sectional view of the ignition coil for starting the internal combustion engine, and FIG. 7 is an explanatory diagram showing the magnetized state of the magnet. In the figure 1...Ignition coil for internal combustion engine 2...Iron core 2b...
・Second core 2a...First core 3...Primary coil 5...Permanent magnet 5a...Magnet material 5b with excellent demagnetization resistance properties...Magnet material 4 with poor demagnetization resistance properties... Secondary coil agent Kenji Ishiguro 1...Ignition coil for internal combustion engine 2...Iron core 2a...First core 2b...Second core 3...Primary coil 4...Secondary coil 5...・Permanent magnet 5a... Magnet material with excellent demagnetization resistance 5b... Magnet material with poor demagnetization resistance I 5 causes

Claims (1)

[Scope of Claims] 1) (a) An iron core with an air gap formed in a part to form a closed magnetic path; (b) A primary coil wound around this iron core and exciting the iron core by being energized. (c) a secondary coil that is wound around the iron core and generates an electromotive force as the primary current flows through the primary coil; A permanent magnet is magnetized to repel the magnetic flux generated in the iron core when energized, and the permanent magnet is made of a magnet material with poor demagnetization resistance and a magnet material with excellent demagnetization resistance. A magnet material with poor demagnetization properties is used in a part where the demagnetizing field is small when the primary coil is operated, and a magnet material with excellent demagnetization resistance is used in a part where the demagnetizing field is large when the primary coil is operated. An ignition coil for an internal combustion engine, characterized in that it is used in a part.