JP2769743B2 - Ignition coil for internal combustion engine - Google Patents

Description

Description: 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 ignition coil in which a permanent magnet is interposed in a magnetic path to increase an output voltage.

2. Description of the Related Art Generally, an ignition device for an internal combustion engine interrupts a primary current of an ignition coil, supplies a high voltage generated on a secondary side according to a change in magnetic flux in the coil to an ignition plug, and mixes the mixture in a cylinder. It ignites the mind.

With respect to the above-mentioned ignition coil, an increase in output voltage and discharge energy is required with the recent increase in output of the internal combustion engine. For this reason, it is necessary to take measures such as increasing the cross-sectional area of the core and increasing the number of turns of the secondary coil wound around the core.However, the ignition coil becomes large, which contradicts the demand for miniaturization of the entire ignition device. Becomes

Japanese Utility Model Publication No. 48-49425 also explains that it is necessary to increase the number of turns of the secondary coil or increase the magnetic flux passing through the magnetic core in order to increase the output voltage of the secondary coil. ing. In the same gazette, as a means to solve this,
There has been proposed an ignition coil in which a magnet having a magnetizing force in a direction opposite to the direction of magnetization generated when a switch is closed is inserted in a magnetic path. Similarly, Japanese Patent Publication No. 41-2082 discloses an ignition coil in which a permanent magnet is provided in a magnetic path of an iron core, that is, a magnetic path of a core, which provides a magnetic flux that is different from a magnetic flux of a primary coil, that is, a magnetic flux in an opposite direction. Other JP-A-59-167006,
Japanese Patent Application Laid-Open No. Sho 60-218810 also discloses an ignition coil in which a permanent magnet is arranged in a gap provided in a core.

In any of the above prior arts, one or two gaps are formed in a portion other than a portion where both coils are wound with respect to a core around which a primary coil and a secondary coil are wound, and a permanent magnet is formed in the gap. Is to be interposed.

[Problems to be Solved by the Invention] In the ignition coil in which the permanent magnet is interposed in the magnetic path as described above, the change in magnetic flux when the primary current is interrupted is large, and the output voltage generated in the secondary coil is the same as the conventional ignition coil. Larger than a coil. However, in these ignition coils, since a large amount of leakage magnetic flux is generated when the primary coil is energized, most of the magnetic flux that has increased in angle is canceled out and the increase in magnetic flux is small. JP-A-48-49425 also discloses an ignition coil provided with two permanent magnets, but both are provided at positions most distant from both ends of the coil on the outer side of the core,
No consideration is given to magnetic flux leakage.

Therefore, the present invention relates to an ignition coil mounted on an internal combustion engine, and an object thereof is to suppress the leakage of magnetic flux and increase the output voltage without increasing the size of the ignition coil.

Means for Solving the Problems In order to achieve the above object, the present invention relates to an ignition coil for an internal combustion engine for inducing a high voltage in a secondary coil by interrupting an energizing current to a primary coil. Are arranged at substantially the midpoint of a portion equally divided into a predetermined number in the axial direction, and the same number of permanent magnets as the predetermined number to generate a magnetic flux in the opposite direction to the magnetic flux by the primary coil; and the permanent magnets housed in the primary coil. An internal core comprising a plurality of core members adjacent to each other via a magnet, and an external core joined to both ends of the internal core and arranged around the primary coil and the secondary coil.

The inner core and the outer core may be integrally joined.

When the number of the permanent magnets is an even number, the inside of the primary coil may be arranged at a position equally divided into a number obtained by adding 1 to the number of the permanent magnets. For example, when three equal-sized core members are joined in the axial direction and housed in the primary coil, a permanent magnet is interposed at the joint between the central core member and the core members on both sides thereof. May be.

[Operation] In the ignition coil of the present invention configured as described above, the inner core is constituted by a plurality of core members housed in the primary coil, and between the core members adjacent to each other in the primary coil. Each is provided with a permanent magnet.
The permanent magnet is arranged at a substantially midpoint of a portion equally divided in the primary coil into a predetermined number in the axial direction, and is arranged to generate a magnetic flux in a direction opposite to a magnetic flux generated by the primary coil.

Thus, the intermittent primary current supplied to the primary coil causes a change in magnetic flux in the inner core and the outer core, and induces a high voltage in the secondary coil. At this time, due to the presence of the magnetic flux of the permanent magnet, the change of the linkage magnetic flux of the secondary coil becomes large, and the output voltage becomes large. In addition, since the permanent magnet is arranged at an appropriate position in the primary coil, local magnetic saturation is eliminated, the leakage magnetic flux is reduced, and a predetermined linkage magnetic flux for the secondary coil is secured.

Hereinafter, a preferred embodiment of the ignition coil of the present invention will be described with reference to the drawings.

FIGS. 1 to 3 show an embodiment of an ignition coil according to the present invention.
21 and a secondary coil 22 are wound, and the inner core 10 includes two permanent magnets 18 and 19 and forms a substantially closed magnetic path with the outer cores 14 and 15. The primary coil 21 is wound around a primary bobbin 23,
The secondary coil 22 is wound around a secondary bobbin 24. The primary bobbin 23 and the secondary bobbin 24 are formed into a small-diameter and a large-diameter spool shape, respectively, of synthetic resin, and are formed such that the former wound with a coil winding is housed in the latter hollow portion. I have. The secondary bobbin 24 is formed with a plurality of flange portions 24a, and the coil winding of the secondary coil 22 is divided while maintaining a mutual connection relationship through the notch 24b of the flange portion 24a shown in FIG. It is wound.

The inner core 10 in this embodiment has three core members 11, 12,
13 and permanent magnets 18, 1 between the mutually adjacent core members.
9 are interposed. The permanent magnets 18 and 19 are set so that the inside of the primary coil 21 is arranged at a substantially middle point of a portion (in the present embodiment, a bisected portion) equally divided by the number in the axial direction. That is, as shown in FIG. 1, the permanent magnets 18 and 19 are arranged on the end sides of the position where the inside of the primary coil 21 is divided into four equal parts, and the rectangular core members 11, 12 and 13 are adjacent to each other via these. Is provided. Accordingly, as shown in FIG. 1, the core member 12 has an axial length 2l, the core members 11 and 13 have an axial length l, and one end of each of them protrudes outward from the primary coil 21. Are located in The permanent magnets 18 and 19 have the same magnetic flux direction,
Are arranged in a direction opposite to the direction of the magnetic flux formed in the internal core 10 when the current is supplied. The permanent magnets 18 and 19 have the same thickness, which is half the thickness required when one permanent magnet is provided.

The primary bobbin 23 includes a core member 11, a permanent magnet 18, and a core member.
12, the permanent magnet 19 and the core member 13 are formed in this order by sequentially disposing them in a resin molding die (not shown) and then insert-molding them with a synthetic resin. Then, the core members 11, 1
The three protruding ends 11a and 13a are gripped, and the coil winding of the primary coil 21 is wound around the primary bobbin 23. These are separately housed in the hollow portion of the secondary bobbin 24 around which the secondary coil 22 is wound, and external cores 14 and 15 are provided therearound and joined to the core members 11 and 13. The outer cores 14 and 15 are formed in a U-shape when viewed from the front, and the end faces of both open ends are joined to the side surfaces of the protruding ends 11a and 13a of the core members 11 and 13, and are magnetically coupled. . As a result, the inner core 10 is
And constitutes a substantially closed magnetic circuit together with the outer cores 14 and 15. Each of the inner core 10 and the outer cores 14, 15 is composed of a laminate of silicon steel sheets. The core members 11, 13 at both ends may be formed integrally with the outer cores 14, 15, respectively. The inner core 10, the outer cores 14, 15, the primary coil 21, and the secondary coil 22 are accommodated in a case 30 made of synthetic resin.

One end of the primary coil 21 is connected to a not-shown battery, and the other end is connected to a not-shown control circuit, commonly called an igniter. One end of the secondary coil 22 is connected to the battery together with one end of the primary coil 21, and the other end is connected to an electrode (not shown) in a secondary connector 32 integrally formed with the case 30, and a spark plug (not shown) or a distributor (not shown) Is electrically connected to Then, the case 30 is filled with a thermosetting synthetic resin and cured to form a resin portion 31. Thereby, the primary coil 21 and the secondary coil 22 are impregnated and fixed, and the insulation property that can withstand the output high voltage of the secondary coil 22 is secured.

A primary current is supplied by a control circuit (not shown) to the primary coil 21 of the ignition coil 1 having the above-described configuration. When the primary current is interrupted at a predetermined frequency, the inner core 10 and the outer core 14, including the permanent magnets 18, 19, Flux change occurs in 15. As a result, a predetermined high voltage is generated in the secondary coil 22, and this high voltage is supplied to the ignition plug directly from the secondary connector 32 or via a power distributor. In this case, the permanent magnet 1 interposed between the core members 11, 12, 13 of the inner core 10
Larger effective magnetic flux changes can be secured by 8,19. Moreover, in this embodiment, since the permanent magnets 18 and 19 are arranged at substantially the midpoint in the primary coil 21 in the axial direction as schematically shown in FIG. 1
8 and 19 are gathered at the center of the primary coil 21 as shown in FIG. 4 (A) or are separated from both ends as shown in FIGS. 4 (D) and 4 (E). Less, inner core 10
, Local magnetic saturation is eliminated. Therefore, the inner core 10 and the outer core 1
The magnetic flux densities at 4, 15 are large, and the discharge energy is maximum as shown in the measurement results of the present embodiment in FIG. 5C. Further, since the change in magnetic flux becomes large, the output voltage of the secondary coil 22 becomes large. The core 10a in FIGS. 4A to 4E simply shows the inner core 10 and the outer cores 14 and 15 in FIG. 1, and A to E in FIG. The output characteristics of the ignition coils of (A) to (E) are shown, and the vertical axis is the discharge energy (mJ).

In the case where an even number of permanent magnets are arranged as in the present embodiment, as shown in FIG. 4 (B), the inside of the primary coil 21 is equally divided by the number obtained by adding 1 to the number of permanent magnets. Location
That is, in this embodiment, when the permanent magnets are arranged at three equally divided positions, the discharge energy (shown by C in FIG. 5) in the case of FIG. 4 (C) as shown by B in FIG. Equivalent discharge energy is obtained.

In the above embodiment, two permanent magnets are provided, but when one or three permanent magnets are provided,
The output characteristics of the secondary coil 22 according to the arrangement of the permanent magnets in the primary coil 21 shown in FIGS. 6 and 8 are as shown in FIGS. 7 and 9, respectively. First, in an ignition coil in which only one permanent magnet 17 is arranged in the primary coil 21,
As shown in FIG. 6 (C), the discharge energy when the permanent magnet 17 is arranged in the axial center of the primary coil 21 is maximum. That is, as shown in FIG. 6A, the discharge energy of the ignition coil in which the permanent magnet 17 is disposed only at the end of the primary coil 21 (shown by A in FIG. 7), and as shown in FIG. The discharge energy (indicated by B in FIG. 7) of the ignition coil in which the permanent magnet 17 is disposed at the end of the position where the inside of the primary coil 21 is divided into four equal parts in the axial direction is compared with that of FIG. The discharge energy of the ignition coil (indicated by C in FIG. 7) has the largest value.

When three permanent magnets 17, 18, and 19 are arranged in the primary coil 21 as shown in FIG. 8, the output characteristics are as shown in FIG. That is, as shown in FIG.
The discharge energy of the ignition coil (shown by A in FIG. 9) in which permanent magnets 17, 18, and 19 are arranged at the center and both ends in the axial direction,
And the discharge energy (shown by C in FIG. 9) of the ignition coil in which the permanent magnets 17, 18, and 19 are concentrated in the axial center of the primary coil 21 as shown in FIG. 8 (C). As shown in FIG. 9B, the discharge energy when the permanent magnets 17, 18, and 19 are disposed at the respective midpoints of the three equally divided portions in the primary coil 21 as shown in FIG. Will be the largest. In addition, permanent magnet
The thicknesses of 17, 18, and 19 are reduced to one-third when only one permanent magnet 17 is provided as shown in FIG.

[Effects of the Invention] The present invention is configured as described above, and has the following effects.

That is, according to the ignition coil of the present invention, the internal core composed of a plurality of core members is accommodated in the primary coil, and the permanent magnets are provided between the adjacent core members. Is large, and a large output voltage is obtained. In addition, since the permanent magnet is disposed at an appropriate position in the primary coil, local magnetic saturation is eliminated, the leakage magnetic flux is reduced, and the output voltage is secured. Therefore,
For example, even when the ignition coil is mounted near the magnetically responsive signal generator, the signal generator does not malfunction and a stable output signal can be secured. Also,
Since the leakage of magnetic flux can be suppressed without providing a special member, the ignition coil does not become large.

[Brief description of the drawings]

1 is a longitudinal sectional view of an ignition coil according to one embodiment of the present invention, FIG. 2 is a sectional view taken along line II-II in FIG. 1, and FIG. 3 is III-I in FIG.
4 (A), (B), (C), (D) and (E) show an ignition coil according to an embodiment of the present invention and two permanent magnets are provided in a primary coil. FIG. 5 is a front view schematically showing an example of the arrangement when the ignition coil is turned on, FIG. 5 is a graph showing the discharge energy of the ignition coil in each example of the arrangement shown in FIG. 4, FIG.
(B) and (C) are front views schematically showing an arrangement example when one permanent magnet is provided in the primary coil, and FIG. 7 shows discharge energy of the ignition coil in each arrangement example in FIG. 8 (A), 8 (B) and 8 (C) are front views schematically showing an arrangement example when three permanent magnets are provided in the primary coil, and FIG. 9 is each of FIG. It is a graph which shows the discharge energy of the ignition coil in the example of arrangement. 1 ... Ignition coil, 10 ... Inner core, 11, 12, 13 ... Core member, 14,15 ... Outer core, 17,18,19 ... Permanent magnet, 21 ... Primary coil, 22 ... 2 Primary coil, 23 …… primary bobbin, 24 ……
Secondary bobbin, 30 …… Case, 31 …… Resin part

Claims (2)

(57) [Claims] 1. An ignition coil for an internal combustion engine for inducing a high voltage in a secondary coil by interrupting an electric current flowing through a primary coil, wherein a substantially middle point of a portion equally divided in the axial direction of the primary coil into a predetermined number. The predetermined number and the same number of permanent magnets that are arranged in the primary coil and generate a magnetic flux in the opposite direction to the magnetic flux generated by the primary coil, and an internal core including a plurality of core members housed in the primary coil and adjacent via the permanent magnet, And an outer core joined to both ends of the inner core and arranged around the primary coil and the secondary coil. 2. The ignition coil for an internal combustion engine according to claim 1, wherein said inner core and said outer core are integrally joined.