JPH10340821A - Ignition coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ignition coil capable of improving output performance and suitable for miniaturization. SOLUTION: This ignition coil 21 is provided with a magnetic core 23 and a primary side bobbin 29 and a secondary side bobbin 31, on which a primary coil 25 and a secondary coil 27 are respectively wound. A magnet body 34 composed of plural, two in this case, quadrilateral plate-shape permanent magnets 33 is inserted inside a magnetic gap 23b provided in the magnetic core 23, and the residual magnetization of the magnetic core 23 by the magnetic field of the primary coil 25 is eliminated by the reverse bias magnetic field of the magnet body 34. Since the magnet body 34 is constituted of the plural permanent magnets 33, a strong reverse bias magnetic field is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition coil used for an internal combustion engine of a motor vehicle, and more particularly to an ignition coil of an independent ignition type which can be installed on a cylinder head.

[0002]

2. Description of the Related Art FIGS. 8 and 9 are sectional views of conventional ignition coils 1 and 3. The ignition coils 1 and 3 have a magnetic core 5 formed by laminating electromagnetic steel sheets and an outer peripheral portion of the magnetic core 5. And a primary bobbin 11 and a secondary bobbin 13 around which the primary coil 7 and the secondary coil 9 are wound, respectively. The DC voltage from the battery is intermittently applied to the primary coil 7. When the voltage applied to the primary coil 7 is switched from on to off, an induced voltage is induced in the secondary coil 9. Electric power is taken out as electric power for sparking the spark plug.

When the voltage applied to the primary coil 7 is switched from on to off to extract an electromotive force in this manner, residual magnetization remains in the magnetic core 5 due to the magnetic field generated by the primary coil 7. However, in the ignition coils 1 and 3, a permanent magnet 15 that applies a magnetic field (reverse bias) opposite to the magnetic field generated by the primary coil 7 to the magnetic core 5 is inserted into the magnetic gap 5 a of the magnetic core 5. 1
The remanent magnetization of the magnetic core 5 is canceled by the magnetic field 5 so that a high voltage can be efficiently extracted.

FIG. 10 is a diagram showing a magnetization curve of a magnetic body (magnetic core 5). The principle of improving the output performance of the ignition coils 1 and 3 by inserting a permanent magnet 15 will be described with reference to FIG. The width of change in the magnetic field generated by the primary coil 7 when the voltage applied to the primary coil 7 is switched from on to off is Hw. At this time, the permanent magnet 1
In the case where 5 is not inserted, the magnetomotive force H applied to the magnetic core 5 changes from Hw to zero as the applied voltage is turned off.
Accordingly, the magnetic flux density M of the magnetic core 5 changes from M1 to M2, and the change width of the magnetic flux density M at this time has a small value Mw due to the influence of the residual magnetization of the magnetic core 5.

On the other hand, when the permanent magnet 15 is inserted, the magnetomotive force H applied to the magnetic core 5 changes from, for example, plus Hw / 2 to minus Hw / 2 as the applied voltage is turned off. The magnetic flux density M of the magnetic core 5 changes from, for example, M3 to zero because the coercive force provided by the permanent magnet 15 reduces the residual magnetization of the magnetic core 5. A value Mw ′ larger than Mw is obtained. Further, since the electromotive force that can be extracted from the secondary coil 9 is proportional to the change width of the magnetic flux density M of the magnetic core 5, the output performance of the ignition coils 1 and 3 can be improved by inserting the permanent magnet 15. I have.

[0006]

However, a general property of the permanent magnet is that the magnetic flux density at the central portion is smaller than the magnetic flux density at the outer peripheral portion.
In the above-described ignition coils 1 and 3 using the single-plate permanent magnets 15, the magnetic flux density in the central portion of the permanent magnets 15 becomes small, and in order to obtain the coercive force necessary to remove the residual magnetization of the magnetic core 5. It is necessary to enlarge the permanent magnet 15 by increasing its thickness and surface area (width × depth).
When the size of the permanent magnet 15 increases, the size of the magnetic gap 5a formed in the magnetic core 5 also needs to increase accordingly. FIG.
9, the surface area of the permanent magnet 15 is larger than the cross-sectional area perpendicular to the axis of the coil mounting portion of the magnetic core 5, and the magnetic gap 5 a is formed obliquely with respect to the axis of the magnetic core 5 ( This is dealt with by enlarging the diameter of the magnetic core 5 in the portion where the magnetic gap 5a is formed (FIG. 8) (FIG. 9).

As described above, when the magnetic gap 5a becomes large, there is a problem that the magnetic loss when the magnetic core 5 is magnetized by the primary coil 7 becomes large, and the output performance of the ignition coils 1 and 3 is rather deteriorated. In addition, there is a problem that an increase in the size of the permanent magnet 15 causes an increase in the size of the ignition coils 1 and 3.

In view of the above problems, an object of the present invention is to provide an ignition coil which can improve output performance and is suitable for downsizing.

[0009]

A technical means for achieving the above object is to provide a primary coil and a secondary coil around a magnetic core, and change the DC current supplied to the primary coil to change the magnetic field. In an ignition coil in which a high voltage is induced in the secondary coil by changing the amount of magnetic flux passing through the core, a direction opposite to a magnetic field generated by the primary coil is set in a magnetic gap provided in the magnetic core. A plurality of permanent magnets for applying a magnetic field to the magnetic core are inserted in parallel.

[0010] Preferably, the magnetic gap is formed in a direction perpendicular to the axis of the magnetic core, and the plurality of permanent magnets are preferably arranged in a plane in the magnetic gap.

Preferably, the magnetic gap is formed obliquely with respect to the axis of the magnetic core, and the plurality of permanent magnets are arranged in a plane in the magnetic gap.

Preferably, the magnetic gap is formed in a V-shape, and a plurality of the permanent magnets are arranged in the magnetic gap in a V-shape.

[0013]

FIG. 1 is a sectional view of an ignition coil according to an embodiment of the present invention. The ignition coil 21 includes a magnetic core 23 formed by laminating electromagnetic steel sheets, and a primary bobbin 29 and a secondary bobbin 31 around which a primary coil 25 and a secondary coil 27 each made of an enamel wire are wound. In the magnetic gap 23b provided in the magnetic core 23, a plurality of
Here, two quadrangular plate-shaped permanent magnets 33 (rare-earth magnets)
Is inserted. The ignition coil 21 configured as described above is housed in a case (not shown), and a gap in the case is filled with an insulating material such as insulating oil or epoxy resin, and can withstand the output high voltage of the secondary coil 27. Insulation is ensured.

The magnetic core 23 has a loop shape, and a primary bobbin 29 and a secondary bobbin 31 are provided in a part of an outer peripheral portion thereof. It is provided in a stacked state so as to be inside. In addition, the primary and secondary bobbins 2 of the magnetic core 23 are provided.
A portion (coil mounting portion) 23a provided with 9, 31 is provided with a rectangular magnetic gap 23b extending along a direction orthogonal to the axis of the magnetic core 23.

As shown in FIG. 2, each permanent magnet 33 of the magnet body 34 has such a size and shape that it fits exactly in the magnetic gap 23b such that the magnetic gap 23b is divided into two parts in the vertical direction. Each of the permanent magnets 33 applies a magnetic field (reverse bias) in the opposite direction to the magnetic field generated by the primary coil 25 to the magnetic core 23 so that the magnetic gap 23 b
Are installed in the magnetic gap 23b in a state where they are arranged in parallel in a plane along the direction in which they extend. In addition, each permanent magnet 3
3 is manufactured independently. The magnet body 34 constituted by such a permanent magnet 33 has a width W set to 20 mm, a depth D set to 10 mm, and a thickness T set to 0.8 to 2.0 mm (here, 1 mm). Is divided into two at the center.

In the ignition coil 21 of the present embodiment, similarly to the conventional example, the DC voltage from the battery is intermittently applied to the primary coil 25, and the voltage applied to the primary coil 25 switches from on to off. As a result, the electromotive force induced in the secondary coil 27 is taken out as electric power for sparking the spark plug. When the voltage applied to the primary coil 25 is switched from on to off,
Since the magnetic core 23 is reverse-biased by the permanent magnet 33, the influence of the residual magnetization due to the magnetic field generated by the primary coil 25 is removed, and a high voltage can be efficiently extracted.

As a general property of the permanent magnet, there is a property that the magnetic flux density in the central portion is smaller than that in the peripheral portion. In the present embodiment, the magnet body 34 is composed of a plurality of permanent magnets 33. By doing so, a stronger reverse bias can be obtained. This is because, when the magnet body is constituted by a single permanent magnet, the effective area (hatched area) where a large magnetic flux density can be obtained is only the peripheral area of the magnet body as shown in FIG. However, in the case where the magnet body 34 is constituted by a plurality of permanent magnets 33, as shown in FIG.
Of the magnet body 3 in the effective area.
This is because the ratio of No. 4 on the surface increases.

In order to show this concretely, a magnet body 35 (see FIG. 4A) constituted by a single permanent magnet,
The distribution of the magnetic flux density with the magnet body 34 (see FIGS. 4B and 4C) constituted by two or four permanent magnets 33 was measured. FIG. 5 shows the measurement results.
4A to 4C show the magnetic flux density distribution and the average magnetic flux density on the surfaces of the magnet bodies 34 and 35, respectively. The horizontal axis indicates the distance from one end to the other end of the magnet body 34 along the width direction, and the vertical axis indicates the magnitude of the magnetic flux density. In the figure, A1 to A3 correspond to FIG.
FIG. 3 is a graph showing magnetic flux density distributions of the magnet bodies 34 and 35 of (a) to (c), wherein B1 to B3 are average magnetic flux densities on the surfaces of the magnet bodies 34 and 35 of FIGS. FIG. From the graphs B1 to B3, it can be seen that a stronger reverse bias can be obtained with the magnet body 34 including the plurality of permanent magnets 33 than with the magnet body 35 including the single plate permanent magnet. Here, the magnet body 34,
The size of the magnet body 34 shown in FIG.
Was set equal to the size.

As described above, according to the present embodiment, since the magnet body 34 for applying a reverse bias to the magnetic core 23 is constituted by a plurality of magnets 34 arranged in parallel, here two permanent magnets 33, a conventional magnet is used. As compared with using a single permanent magnet, a stronger reverse bias magnetic field can be generated.

Therefore, the thickness and the area (width W × depth D) of the magnet body 34 and the magnetic gap 23b can be reduced while ensuring a sufficient coercive force to reduce the residual magnetization of the magnetic core 23. , Ignition coil 2
1 can be improved in output performance and downsized.
That is, conventionally, as shown in FIGS. 8 and 9, the area of the permanent magnet and the magnetic gap is reduced by the coil mounting portion 23 of the magnetic core.
In the present embodiment, the area of the magnet body 34 and the magnetic gap 23b can be set to be equal to the cross-sectional area perpendicular to the axis of the coil mounting portion 23a of the magnetic core 23. I have.

The magnetic core 23 has a magnetic gap 23b.
The magnetic core 23 may be used without inserting the magnet body 34 in this manner, but by reducing the thickness and the area of the magnetic gap 23b in this way, the magnetic core 23 is used when the magnet body 34 is not inserted. Can be reduced, and the output performance of an ignition coil using the magnetic core 23 in which the magnet body 34 is not inserted can be improved.

Further, since the plurality of permanent magnets 33 are arranged in parallel in the magnetic gap 23b, the magnetic core 23 can be uniformly reverse-biased. Therefore, the magnetic core 23
Can be canceled without unevenness, and the output performance of the ignition coil 21 can be improved.

FIG. 6 is a sectional view showing a first modification of the above-described ignition coil 21. In the ignition coil 41, the magnetic gap 23b is formed in a straight line obliquely to the axis of the coil mounting portion 23a of the magnetic core 23, and the magnet body 3 is provided in the magnetic gap 23b.
4 are inserted in a state where the two permanent magnets 33 are arranged in a plane.

FIG. 7 is a sectional view showing a second modification of the above-described ignition coil 21. As shown in FIG. In the ignition coil 51, the magnetic gap 23b is substantially flat
The magnetic core 23 has a V-shape and is formed to be symmetrical with respect to the axis of the coil mounting portion 23a of the magnetic core 23. In the magnetic gap 23b, two permanent magnets 33 constituting the magnet body 34 are inserted in a state of being arranged in a V-shape in parallel. Here,
Although the magnetic gap 23b has a V-shape symmetrical with respect to the axis, the magnetic gap 23b does not necessarily have to be a V-shape with symmetry.

In the above-described embodiment, the magnet body 34 is constituted by two permanent magnets 33. However, the number of permanent magnets is not limited to two, and the magnet body 34 may be constituted by an arbitrary number of permanent magnets.

[0026]

As described above, according to the first to fourth aspects of the present invention, a plurality of magnetic fields, which are opposite to the magnetic field generated by the primary coil, are applied to the magnetic gap provided in the magnetic core. Since the permanent magnets are inserted in parallel, a stronger reverse bias magnetic field can be generated than in the case of using a single permanent magnet as in the related art.

As a result, the thickness and area of the permanent magnet and the magnetic gap can be reduced while securing a coercive force sufficient to reduce the residual magnetization of the magnetic core, thereby improving the output performance of the ignition coil and reducing the size of the ignition coil. Can be achieved.

The magnetic core is sometimes used without inserting a permanent magnet into the magnetic gap.
By reducing the thickness and area of the magnetic gap in this manner, the magnetic loss of the magnetic core when used without inserting a permanent magnet can be reduced, and an ignition using a magnetic core without a permanent magnet inserted can be performed. The output performance of the coil can also be improved.

Furthermore, since a plurality of permanent magnets are arranged in parallel in the magnetic gap, a reverse bias magnetic field can be uniformly applied to the magnetic core. For this reason, the residual magnetization of the magnetic core can be canceled without unevenness, and the output performance of the ignition coil can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of an ignition coil according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a configuration of a magnetic gap of a magnetic core and permanent magnets used in the ignition coil of FIG. 1;

3A is a diagram showing an effective area on the surface of a magnet body composed of a single permanent magnet, and FIG. 3B is a diagram showing an effective area on the surface of a magnet body composed of two permanent magnets. FIG.

4A is a diagram showing a magnet body composed of a single permanent magnet, FIG. 4B is a diagram showing a magnet body composed of two permanent magnets, and FIG. FIG. 4 is a diagram showing a magnet body composed of four permanent magnets.

FIG. 5 is a diagram showing a magnetic flux density distribution and an average magnetic flux density on the surface of the magnet body of FIGS. 4 (a) to 4 (c).

FIG. 6 is a cross-sectional view showing a first modification of the ignition coil of FIG. 1;

FIG. 7 is a sectional view showing a second modification of the ignition coil of FIG. 1;

FIG. 8 is a cross-sectional view showing an ignition coil according to a first related art.

FIG. 9 is a cross-sectional view showing an ignition coil according to a second related art.

FIG. 10 is a diagram showing a magnetization curve of a magnetic body (magnetic core).

[Explanation of symbols]

 21, 41, 51 Ignition coil 23 Magnetic core 23b Magnetic gap 25 Primary coil 27 Secondary coil 33 Permanent magnet

Claims (4)

[Claims] A primary coil and a secondary coil are provided around a magnetic core, and a DC current supplied to the primary coil is changed to change an amount of magnetic flux passing through the magnetic core, so that a high voltage is applied to the secondary coil. In an ignition coil adapted to induce a voltage, a plurality of permanent magnets for applying a magnetic field opposite to a magnetic field generated by the primary coil to the magnetic core are inserted in parallel into a magnetic gap provided in the magnetic core. An ignition coil, characterized in that: 2. The magnetic gap according to claim 1, wherein the magnetic gap is formed in a direction perpendicular to an axis of the magnetic core, and a plurality of the permanent magnets are arranged in a plane within the magnetic gap. 2. The ignition coil according to 1. 3. The magnetic gap according to claim 1, wherein the magnetic gap is formed obliquely to an axis of the magnetic core, and the plurality of permanent magnets are arranged in a plane in the magnetic gap. 2. The ignition coil according to 1. 4. The ignition coil according to claim 1, wherein the magnetic gap is formed in a V shape, and a plurality of the permanent magnets are arranged in a V shape in the magnetic gap. .