JPH04118908A - Ignition coil for internal combustion engine use - Google Patents

Abstract

PURPOSE:To arrange a permanent magnet and a core in a prescribed position inside a primary bobbin by a method wherein a tube body is constituted in such a way that the other of one pair of members in which the central core and the permanent magnet have been arranged is bonded to a prescribed position at the inside of one of the pair of members of the primary bobbin. CONSTITUTION:A primary bobbin 23 is composed of members 230, 230, in the same shape, which are formed in such a way that a resin tube body whose cross section is nearly rectangular is divided into two parts in its axial direction. Cores 11 to 13 and permanent magnets 17, 18 are housed at the inside of one of the members 230, 230; after that, the other is bonded; a tube body is constituted. Guard parts 231, 231 are projected and formed at both ends of the members 230; support parts 232, 232 which are provided with projected parts on the same axis as the projected width of the guard parts 231, 231 are formed sequentially at individual positions excluding the center. When the primary bobbin 230 is assembled, a core 12 is arranged in a main body part 234 at the center with reference to one of a pair of the members 230, 230, the permanent magnets 17, 18 are arranged respectively in the center of the support parts 230 on both sides, and the cores 11, 13 are arranged. When the other member 230 is piled up in this state, protruding parts 235 and recessed parts 236 are fitted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ignition coil for an internal combustion engine, and more particularly to an ignition coil that increases output voltage by interposing a permanent magnet in a magnetic path within a primary bobbin.

[Conventional technology]

Ignition systems for internal combustion engines generally intermittent the primary current of the ignition coil, and apply a high voltage generated on the secondary side to the spark plug in response to changes in magnetic flux within the coil to ignite the air-fuel mixture in the cylinder. It is.

Regarding the above-mentioned ignition coil, as the output of internal combustion engines has recently increased, an increase in output voltage and discharge energy is required. 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 coil wound around the core, but this would result in a larger ignition coil, which goes against the demand for miniaturization of the ignition system as a whole. .

Utility Model Application Publication No. 48-49425 also explains that in order to increase the output voltage of the secondary coil, it is necessary to increase the number of windings in the secondary coil or increase the magnetic flux passing through the magnetic core. ing. As a means to solve this problem, the publication proposes an ignition coil in which a magnet having a magnetizing force in the opposite direction to the direction of magnetization generated when the switch is closed is inserted into the magnetic path. Similarly, Japanese Patent Publication No. 41-2082 discloses an ignition coil in which a permanent magnet is provided in the magnetic path of an iron core, which provides a magnetic flux different from the magnetic flux of the primary coil, that is, a magnetic flux in the opposite direction. Other Tokukai Showa 5
No. 9-167006 and Japanese Unexamined Patent Publication No. 60-218810 also disclose ignition coils in which permanent magnets are arranged in gaps provided in the core.

[Problem to be solved by the invention]

In the ignition coil in which a 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 large compared to the conventional ignition coil. However, in these ignition coils, since there is a large amount of leakage magnetic flux generated when the primary coil is energized, much of the increased magnetic flux is canceled out, and the increase in magnetic flux is small. As a means of reducing such leakage magnetic flux, a permanent magnet may be placed inside the primary bobbin around which the primary coil is wound and sandwiched between the cores, but in order to effectively reduce the leakage magnetic flux, it is necessary to It is essential to place the permanent magnet at an appropriate predetermined position. Furthermore, in order to prevent the permanent magnet from being demagnetized by the magnetic force of the primary coil, it is necessary to increase the area of the permanent magnet relative to the cross-sectional area of the core.

However, it is extremely difficult to arrange the core and permanent magnet at predetermined positions within the primary bobbin. For example, JP-A-60-20
As described in Japanese Patent No. 1607, the core is generally fitted and fixed to the primary bobbin or is formed integrally with the primary bobbin, but in either case, a permanent magnet must be placed at a predetermined position within the primary bobbin. is extremely difficult. In particular, when the area of the permanent magnet is larger than the cross-sectional area of the core, the method is limited to integrally forming the primary bobbin by insert resin molding of the core and permanent magnet, making it difficult to position the core and permanent magnet. Not only that, but the manufacturing process becomes complicated.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an ignition coil for an internal combustion engine that has a simple structure and allows a permanent magnet and a core to be placed at a predetermined position within a primary bobbin regardless of the size of the permanent magnet.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a primary bobbin in which a permanent magnet and a central core are housed in a cylinder and a primary coil is wound around the outer surface of the cylinder; In the ignition coil for an internal combustion engine, the primary bobbin includes a secondary bobbin around which a secondary coil is wound, and an outer core disposed outside the secondary bobbin and joined to the central core. Consisting of a pair of members divided into two in the axial direction,
After the central core and the permanent magnet are arranged at predetermined positions inside one of the pair of members, the other of the pair of members is joined to form a cylinder.

In the above ignition coil for an internal combustion engine, a convex portion is formed on one of the joint surfaces of the pair of members constituting the primary bobbin, and a concave portion is formed on the other, and the concave portion and the convex portion are fitted together. It is preferable to join the pair of members by doing so.

Furthermore, a protrusion extending laterally of the member is formed on the protrusion, and after the protrusion is fitted into the recess, the protrusion is caulked to control the joined state of the protrusion and the recess. can be maintained.

[Operation] In the ignition coil for an internal combustion engine of the present invention configured as described above, a central core and a permanent magnet are located at predetermined positions on the inside of one of the pair of members in which the cylindrical body is divided into two in the axial direction. Placed. The other of the pair of members is joined to this to form a cylindrical primary bobbin. Since the inside of the member constituting the primary bobbin can be formed into various predetermined shapes in advance, even if the area of the permanent magnet is larger than the cross-sectional area of the core,
The inside of the pair of members may be shaped to accommodate a permanent magnet, and the permanent magnet may be fitted from a direction perpendicular to the axis. As a result, the primary current supplied to the primary coil is intermittent, causing a magnetic flux change in the core, and a high voltage is induced in the secondary coil. At this time, a large effective magnetic flux change can be obtained due to the presence of the permanent magnet.

〔Example〕

Hereinafter, preferred embodiments of the ignition coil for an internal combustion engine of the present invention will be described with reference to the drawings.

1 to 5 show an embodiment of the ignition coil of the present invention, in which the ignition coil lO is a primary coil 21 wound around a primary bobbin 23 and a secondary coil wound around a secondary bobbin 24. 22, a magnetic circuit is constituted by cores 11 to 13 and permanent magnets 17.18 housed within these coils, and cores 15.16 arranged around the coils.

In this embodiment, permanent magnets 17 and 18, which are square in plan view, are placed approximately in the middle of the primary bobbin 23, which is divided into thirds in the axial direction, so that the upper part of FIG. 1 is the north pole. The cores 11 to 13, each having a C-shape in front view, are arranged so that the permanent magnets 17 and 18 are sandwiched between the cores. These cores 11 to 13 constitute a central core according to the present invention, and the core 11 and the core 13 have the same shape. That is, the core 11.13 projects outward from the primary bobbin 23 and has projecting end portions 11a, 13b formed therein, and a core 15.
Sixteen arm portions 15a, 15b, 16a, and 16b are joined. The other ends 11b, 13a of the cores 11, 13 and both ends 12a, 12b of the core 12 are formed in a tapered shape that bulges laterally in FIG. It is formed into approximately the same square shape.

The permanent magnets 17 and 18 are arranged so that the direction of magnetic flux generated is the same and opposite to the direction of the magnetic flux formed in the cores 11 to 13 when the primary coil 21 is energized. In addition, permanent magnet 17. ．． 18 has the same thickness, and the width of the negative side is set to a value within the range of 1.5 to 2.5 times the width of one side of the main body of the cores 11 to 13, and in this embodiment, it is approximately 2. It is set to double. Permanent magnet 17
The width of the other side of ゜18 is set to be the same as the width of the other side of the main body of the cores 11 to 13 (same width as both ends), so that it faces any of the cores 11 to 13 of the permanent magnet 17.18. The area of the surface is about twice the area of the cross section perpendicular to the axis of the main body of the cores 11 to 13, within a range of 1.5 to 2.5 times. As the permanent magnet 17.18, samarium-cobalt (Sm-C) has a large residual magnetic flux density and is difficult to demagnetize.
o) Rare earth magnets made of sintered metals are used.

For example, a magnet is used that does not demagnetize even at a temperature of 150° C. until the magnetic flux density in the opposite direction when the primary coil 21 is energized reaches 0.77 (Tesla).

Each of the above-mentioned cores is formed by laminating a plurality of grain-oriented silicon steel plates rolled in the vertical direction in FIG. As is well known, grain-oriented silicon steel sheets exhibit extremely good magnetic properties in the rolling direction, but the magnetic properties deteriorate at angles different from the rolling direction. Therefore, the arm portion 15a perpendicular to the rolling direction of the core 15.16,
The widths of 15b, 16a, and 16b are 1.5 in the rolling direction (longitudinal direction). It is set at 5 to 1.8 times. For example, when a magnetic flux density of 1.77 (Tesla) is allowed in the rolling direction, 1.77 (Tesla) is allowed in a direction at 45° to the rolling direction. Since the magnetic flux density of IT is the limit, the radius Wa of the arms 15a and 16a extending in the direction perpendicular to the longitudinal direction of the core 15.16 is set as Wa=Wbx1.7 with respect to the radius wb of the main body in the longitudinal direction. /1.1. On the other hand, the end 1 of the core 11
1b etc., the smaller the angle of the tapered surface with respect to the end surface that comes into contact with the permanent magnet 17, etc., the lighter it becomes and the longer the winding part of the primary coil 21 becomes, leading to improved performance. However, if the angle is less than a predetermined angle, the magnetic flux is constricted and magnetic resistance increases. becomes large, making it impossible to obtain the desired ignition performance. Therefore, in this embodiment, a tapered surface is formed from the end surface that contacts the permanent magnet 17, etc., leaving a minimum required part (for example, 1 mm) for press processing, and the taper angle is determined to have good ignition performance. It is set to a value of 25° to 356°, which is the minimum angle that can maintain the angle.

The partial bobbin 23 is made up of members 230, 230 of the same shape, each of which is a resin cylinder with a substantially rectangular cross section divided into two parts in the axial direction.

That is, it is divided into two parts, front and rear in FIG. 1, and left and right in FIG. After the cores 11 to 13 and the permanent magnets 17, 18 are housed inside one of these members 230, 230, the other is joined to form a cylinder as shown in FIGS. 1 and 3. .

6 to 14 and 9 are partially enlarged views of the bobbin 23 in which the cores 11 to 13 and the permanent magnets 17 and 18 are accommodated, and the member 230 is shown in the axial direction (see FIGS. 6 and 7). It is formed symmetrically in the vertical direction). In these figures, symmetrical or substantially identical parts are given the same reference numerals. Flange portions 231 and 231 are formed to extend from both ends of the member 230, and extension portions having the same width as the extension portions of the collar portions 231 and 231 are formed at each position except for the center of the four equal parts in the axial direction. A support part 232.232 with a protrusion is formed. The support portion 232 has a predetermined length L in the axial direction, and the side surface of the central portion thereof is open over the axial length l. 6th
As shown by the broken line in the figure, the inner surface of the member 230 is connected to the main body 23.
3, 234 toward the center of the support portion 232 to form an inclined surface. This inclination angle is set to be the same as the angle of the tapered surfaces of the bulging portions of the cores 11 to 13. Furthermore, a convex portion 232a for holding the permanent magnet 17 is formed approximately at the center of the inner surface of the axially central portion of the support portion 232, as shown in FIG. In addition, permanent magnet 17
A recess into which the protrusion 232a fits is formed on the side surface. On the surface of the support portion 232 where the above-mentioned opening does not exist, a sixth
As shown in the figure, a slit 232b is formed in the axial direction.

A convex portion 235 is formed on the side end surface of one side wall of the main body portion 233 of the member 230, and a concave portion 235 is formed on the side end surface of the other side wall.
6 is formed, and a concave portion 236 is formed on the side end surface of one side wall of the main body portion 234, and a convex portion 235 is formed on the side end surface of the other side wall. Therefore, when the pair of members 230.230 are turned upside down and their side end surfaces abut, each main body portion 233.23
The convex portion 235 and the concave portion 236 of No. 4 fit together. In this embodiment, as shown in FIG. 7, the convex portion 235 has a circular tip and a base end smaller in diameter than the convex portion 235, and the concave portion 236 has a circular opening formed at the base end and has a tip smaller in diameter than the convex portion 235. When the two are fitted together, the snap action of the side wall forming the recess 236 ensures that they are joined.

Here, to explain how to assemble the primary bobbin 23, the central body part 23 is attached to one of the pair of members 230 and 230.
Core 12 is placed in core 11.
Place 13. In this state, when the other member 23G is superimposed, the convex part 235 and the concave part 236 fit together, and as shown in FIGS. 6 and 7, the cores 11 to 13 and the permanent magnet 17
．． 18 is sandwiched between a pair of members 230,230. As described above, at least a part of these is accommodated in the widened part of the inner surface of the support part 232, so that they do not fall off, and the snap action of the recessed part 236 allows the parts to be moved between the pair of members 230, 230. is maintained. Part of the winding of the coil 21 is wound around the primary bobbin 23 in two or four layers. At this time, the winding is continuously wound around the main body parts 233 and 234 through the slit 232b of the support part 232.

Both ends of the partial coil 21 are connected to partial terminals 33b and 33c shown in FIGS. 2 and 4, respectively, by soldering or the like. These primary terminals 33b and 33c are molded with insert resin to form a part of the connector 33,
The primary terminal 33b is connected to a battery (not shown), and the primary terminal 33c is connected to a control circuit (not shown), commonly known as an igniter. The winding direction of the primary coil 21 is such that when the primary coil 21 is energized, the permanent magnet 1
It is set to be magnetized in the opposite direction to the magnetization direction of 7.18.

A secondary bobbin 24 around which a secondary coil 22 is wound is disposed outside the primary coil 21 . A plurality of grooves are formed in the secondary bobbin 24 at predetermined intervals in the axial direction, and the winding of the secondary coil 22 is sequentially wound from the upper groove to the lower groove in FIG.

The winding of the secondary coil 22 begins at the primary terminal 33b.
It has the same potential as a battery (not shown). The end of the winding of the secondary coil 22 is connected to a lead 36a at one end of a diode 36 in the lower part of FIG. 4 by soldering or the like.

Arranged around the secondary coil 22 is a core 15.16 molded integrally with the holder 31.32 as described above. That is, cores 15 and 16 are molded with insert resin, and holders 31 and 32 having the same shape as shown in FIG. 5 are formed. Support parts 31a and 31b having a U-shaped cross section are formed at the upper and lower ends of the holder 31, and an insulating part 31c is formed inside the core 15 so as to be continuous with these parts in order to ensure a withstand voltage. The corner portions on both sides of this insulating portion 31c are stepped, and step portions 31d and 31e are formed. still,
The holder 32 also has a similar structure. Thus, between the support portion 31a of the holder 31 and the support portion 32a of the holder 32, the protruding end portion IIa of the core 11 and the arm portion 15 of the core 15.
The joint ends 15c and 16c of a and 16a are sandwiched (see FIGS. 1 and 4), and similarly the joint ends of the protruding end 13b of the core 13 and the arm parts 15b and 16b of the core 15.16 are held together. 15d and 16d are held between the lower support parts 31b and 32b of the holder 31.32.

The width of the upper joint ends 15c, 16C of the core 15.16 is larger than the width of the arms 15a, 16a of the core 15.16, and is coextensive with the protruding end 11a of the core 11. The same relationship holds true for the joint ends 15d and 16d.

As shown in FIG. 1, the protruding end 11a and the joining end 15c
, 16c are provided with holes 15e, 16e, respectively, and the supporting parts 31a, 32 of the holder 31.32 are provided with holes 15e, 16e.
By being heated and pressed from the side of a (from the lower left direction and upper right direction in FIG. 5), the holders 31 and 32 are thermally deformed and enter the holes 15e and 16e, and the cores it and l are heated and pressed.
The upper part of s, 16 is firmly fixed. core 13 and core 1
The lower part of 5.16 is fixed in the same way.

A resin cover 35 consisting of a mounting portion 35a and a support portion 35b having a U-shaped cross section (as shown in FIG. 4) is sandwiched at the bottom of the support portions 31b and 32b. As shown in FIG. 4, the support portion 35b has a grooved protrusion 35c that protrudes downward.
, 35d are formed, and leads 36a and 36b of the diode 36 are sandwiched and fixed in these grooves. Further, the bent legs provided on both sides of the plate 37 are press-fitted into holes formed on both end surfaces of the support portion 35b,
A connecting portion 37a of the plate 37 is connected to a lead 36b of the diode 36 by soldering or the like.

These holders 31, 32, primary coil 21, secondary coil 22, core 11, etc. are arranged in a case 3 as shown in FIG.
It is contained in 0. The case 30 has vertical wall portions 30a, 30
b are arranged in parallel to form an accommodating portion between them, flange portions 30c and 30d are formed at the upper end, and a secondary connector portion 30e of a bottomed cylindrical body is formed at the lower end. Steps (30f represents the four steps) are formed on both sides of the vertical walls 30a and 30b, and a step 31d of the holder 31, 32 or the like is fitted into this step 30f. It is configured to fit closely together. A secondary terminal 34 is accommodated in the secondary connector portion 30e, and a protrusion 34a formed on the top surface thereof extends toward the core 13 through the bottom surface of the secondary connector portion 30e. Then, the protrusion 34a of the secondary terminal 34 is press-fitted into a circular hole bored in the center of the plate 37, and electrical connection is established. case 30
The space defined by the holders 31 and 32 is filled with a thermosetting synthetic resin, such as an epoxy resin, and cured to form the resin portion 38.

Thereby, the primary coil 21 and the secondary coil 22 are impregnated and fixed, and insulation that can withstand the high voltage output from the secondary coil 22 is ensured. The epoxy resin flowing into the cylinder of the secondary bobbin 24 during filling with the epoxy resin can reach the bottom via the slit 232b without being blocked by the support portion 232 of the primary bobbin 23 shown in FIG.

In the ignition coil IO, the upper part of the permanent magnet 17.18 is the N pole as shown in FIG. It is a closed loop that branches to .16 and returns to the core 13. There is almost no leakage of magnetic flux in this state. When the primary coil 21 is energized by a control circuit (not shown) and a primary current is supplied, the magnetic flux flows in a closed loop from the core 11 to the core 13 in the opposite direction to the magnetization direction of the permanent magnets 17,18. At this time, from core 11 to core 15.16,
From core 15.16 to core 13 and then core! 2 and the core 15, 16 occurs. When the primary current is cut off, a back electromotive force is induced in the secondary coil 22 and a high voltage of 30 to 40 kV is generated. This high voltage is applied to a spark plug (not shown) via a diode 36, a plate 37, and a secondary terminal 34.

The diode 36 prevents the spark plug from flying out due to the voltage of 1 to 3 kV generated when the primary coil 21 is energized.

In the ignition coil IO of this embodiment, cores 11 to 1
A large change in effective magnetic flux can be ensured by the permanent magnet I7.18 interposed between each core of No. 3. In particular, since the permanent magnets 17 and 18 are housed within the primary coil 21 and placed at appropriate positions, magnetic flux concentration reduces leakage magnetic flux compared to the past, eliminating local magnetic saturation in the cores 11 to 13. . Moreover, since the area ratio of the permanent magnet 17.18 to the cross section orthogonal to the axis of the main body of the cores 11 to 13 is approximately twice, the magnetic field from the secondary coil 21 reaches the demagnetization limit of the permanent magnet 17.18. The cores 11 to 13 reach the saturation magnetic flux density before reaching the permanent magnet 17.1.
8 is never demagnetized. Therefore, the magnetic flux density formed in the primary coil 21 increases with respect to the magnetomotive force caused by the supply of the primary current, and the discharge energy increases. Moreover, since the magnetic flux change becomes large, the output voltage of the secondary coil 22 becomes large.

1O and 11 show a pair of members 2 of the primary bobbin 23.
30. Another example of the joining means between 30 and 230 is shown. In this embodiment, as shown in FIG.
35 is integrally formed with a protrusion 237 that extends laterally of the member 230.

The rest of the configuration is the same as the previous embodiment. Thus, the pair of members 230 and 230 are overlapped, and the convex portion 235 becomes the concave portion 23.
6, as shown in FIG.
When pressing the protrusion 237 while heating it, the protrusion 2
37 is thermally deformed and widened. As a result, the convex portion 235 is firmly fixed to the concave portion 236, resulting in the configuration shown in FIGS. 6 and 7.

12 and 13 show a pair of members 2 of the primary bobbin 23.
30 and 230. In this embodiment, the member 230 is not formed with convex portions and concave portions as in the above-mentioned embodiments, and the main body portion 233 is
．． The 2340 side end surface is a flat surface. In this embodiment, after the pair of members 230, 230 are joined, the gap formed between the side end surfaces of both members is filled with adhesive 238 and fixed. According to this, adhesive 2
38 is required, but since the member 230 has a simple structure, the mold for manufacturing it becomes easy and inexpensive.

〔Effect of the invention〕

Since the present invention is configured as described above, it produces the effects described below.

That is, according to the ignition coil of the present invention, the permanent magnet and core can be arranged at predetermined positions within the primary bobbin to reduce leakage magnetic flux and prevent demagnetization of the permanent magnet with a simple structure. , a large effective magnetic flux change is obtained, and ignition performance is improved.

Moreover, since it is easy to manufacture and assemble, it can be produced at low cost.

In particular, in the case where a protrusion and a recess are formed on the joining surfaces of a pair of members and the two are fitted together, the protrusion formed on the protrusion is caulked to ensure that the pair of members are reliably joined and the joined state is maintained. Therefore, stable ignition performance can be ensured.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view of an ignition coil according to an embodiment of the present invention, Fig. 2 is a plan view of the ignition coil, and Fig. 3 is a -
■A line sectional view, FIG. 4 is a vertical cross-sectional view of an ignition coil according to an embodiment of the present invention as seen from the side, FIG. 5 is an exploded perspective view of an ignition coil according to an embodiment of the present invention, and FIG. FIG. 7 is a front view of a partial bobbin in which the core and permanent magnet are housed in an ignition coil according to an embodiment of the invention; FIG. 7 is a side view of the primary bobbin;
Figure 8 is a sectional view taken along the line A-A in Figure 7, and Figure 9 is a cross-sectional view taken along line B in Figure 7.
-B sectional view, FIG. 10 is a front view of a part of a bobbin according to another embodiment of the present invention, FIG. 11 is a side view of a part of the primary bobbin, and FIG. FIG. 13 is a front view of a part of a bobbin according to still another embodiment of the invention, and FIG.
-C line sectional view. lO...Ignition coil. 11.12.13...Core (central core). 5.16...Core (outer core) 7.18...Permanent magnet. ■...Primary coil 3...Primary bobbin. 0... Case 30... Member. 36... recess. 22...Secondary coil. 24...Secondary bobbin. 31.32...Holder. 35...Protrusion. 37...protrusion

Claims (3)

[Claims] (1) A primary bobbin in which a permanent magnet and a center core are housed in a cylindrical body and a primary coil is wound around the outside surface of the cylindrical body, and a primary bobbin is housed in a cylindrical body and a secondary coil is wound around the outside surface of the cylindrical body. In an ignition coil for an internal combustion engine, which includes a rotated secondary bobbin and an outer core disposed outside the secondary bobbin and joined to the central core, the primary bobbin has a cylindrical body divided into two parts in the axial direction. It is characterized in that the center core and the permanent magnet are arranged at predetermined positions inside one of the pair of members, and then the other of the pair of members is joined to form a cylinder. Ignition coil for internal combustion engines. (2) A convex portion is formed on one of the joining surfaces of the pair of members constituting the primary bobbin, a concave portion is formed on the other, and the concave portion and the convex portion are fitted, so that the pair of members The ignition coil for an internal combustion engine according to claim 1, wherein the members are joined together. (3) A protrusion extending laterally of the member is formed on the protrusion, and after the protrusion is fitted into the recess, the protrusion is caulked to maintain the bonded state between the protrusion and the recess. The ignition coil for an internal combustion engine according to claim 2, characterized in that the ignition coil is configured to:.