JP2597870B2 - Manufacturing method of ignition coil - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an improvement in a method for manufacturing an ignition coil for an internal combustion engine, and more specifically, when a primary coil is energized by inserting a magnetic flux generating means into a core. The present invention relates to a method for producing an ignition coil in which ignition performance is improved by generating a magnetic flux in a direction opposite to the magnetic flux generated in the ignition coil.

(Prior Art) As is well known, a conventional ignition coil of an internal combustion engine is formed of a core (iron core) in which a primary coil and a secondary coil are wound, and the current flowing through the primary coil is intermittently applied to the secondary coil. A voltage is generated to ignite the mixture in the combustion chamber. As an example of such a prior art, a technique described in Japanese Patent Application Laid-Open No. 58-54618 can be mentioned. In the case of this prior art, an ignition coil having a closed magnetic circuit type core is disclosed.

(Problems to be Solved by the Invention) In an ignition coil, the magnetic energy w that the core can store per unit volume is generally (magnetic permeability μ =
When constant), Specifically, it is determined by the saturation magnetic flux density determined by the volume of the core and the material of the core. Thus, the ignition coil is also expected to be reduced in size and weight for reasons such as the layout at the time of mounting on a vehicle. For this purpose, in the conventional case, a material having the highest possible saturation point is mainly selected as a core material. Such a core material is relatively expensive and has relatively poor workability, resulting in inconvenience such as an increase in cost. Therefore, it has been difficult to sufficiently reduce the size and weight of the ignition coil.

Accordingly, an object of the present invention is to solve the above-mentioned disadvantages of the prior art, and an object of the present invention is to provide a method for manufacturing an ignition coil that can reduce the volume of a core and reduce the size and weight.

(Means and Actions for Solving the Problems) In order to achieve the above object, the present invention provides an ignition coil comprising a magnetizable core and a primary coil and a secondary coil wound around the core. A method for manufacturing an ignition coil configured to generate a magnetic flux in a direction opposite to a magnetic flux generated when the primary coil is energized, while providing a closed magnetic circuit core with a permanent magnet interposed, wherein the closed magnetic circuit core includes: A permanent magnetizable magnetic material is inserted at a position where the magnetization direction is orthogonal to the center axis of the ignition coil, and then the magnetic material is magnetized.

In other words, the present inventors sought various ways to reduce the size and weight of the ignition coil, and found that when a permanent magnet was inserted into the core and the primary coil was energized to generate a magnetic flux, the magnetic flux was generated in the opposite direction. The present invention has been found that the porcelain energy that can be extracted from the core increases. That is, it has been found that by generating a magnetic flux in the opposite direction even in a core having the same cross-sectional area, the same material, and the same winding specification, the magnetic energy that can be extracted from the core increases as compared with the case where it is not possible. It has been found that this makes it possible to reduce the sectional area of the core and reduce the size and weight of the ignition coil itself. Thus, in the present invention, a step of inserting a permanent magnetizable magnetic material into the closed magnetic path core at a position where its magnetization direction is orthogonal to the ignition coil and the center axis, and then magnetizing the magnetic material is performed. With such a configuration, the magnetic material can be magnetized without inconvenience such as dielectric breakdown of the coil.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.
Referring to FIG. 2 for convenience, the ignition coil according to the present invention is provided with a flat rectangular closed magnetic circuit type core 10 formed by laminating silicon steel plates or the like, as shown in FIG. Numeral 10 includes a main body composed of a center core 10a and a side core 10b formed integrally therewith, and has an open end into which a plug-in core 10c can be fitted. Thus, a bobbin 12 is provided on the outer periphery of the center core 10a, and the bobbin 12
The primary coil 14 having an appropriate number of turns is wound thereon as is well known. Outside the primary coil 14, there is provided a second
A bobbin 16 is provided, and a secondary coil 18 is similarly wound thereon appropriately (note that the coils 14, 1
The number of turns of 8 has been simplified). A case 20 is mounted outside the secondary coil 18 to protect the coils 14 and 18 from the outside, and an explosion-proof / insulating resin 22 is provided in a gap between the case 20 and the bobbin or coil. Will be filled. Note that ears 28 are formed at appropriate positions of the core main body 10a, and mounting holes 30 are formed therein.

The feature of the ignition coil according to the present invention in the above configuration is that the magnetic material 320 is inserted into the core 10 and magnetized to form the permanent magnet 32 to generate a magnetic flux. Is characterized in that the insertion position of the magnetic material for the permanent magnet in the core is a position orthogonal to the center axis of the coil. First, the first point will be described with reference to FIGS. 1 and 3. The primary coil wound around the core 10 will be described.
A power supply voltage is supplied to the battery 14 from a battery 40 via an ignition key (not shown), and the current is cut off by a switch 42 including a contact point or an igniter (both not shown). A high voltage is generated in the secondary coil 18 and sparks in the discharge unit 44. The configuration up to this point is not different from the prior art. Thus, in the present invention, by inserting the permanent magnet 32 into the core 10, the direction (indicated by a in FIG. 1) opposite to the direction of generation of the magnetic flux Φc of the primary coil generated by the connection of the switch 42 (see FIG. 1). (Similarly denoted by reference character b)). That is, as shown in FIG. 3, when the conventional core uses only the magnetic flux Φc in the plus direction as shown by the broken line, in the present invention, the core 10 generates the magnetic flux −Φm in the minus direction as shown by the dashed line. As a result, a magnetic flux Φc is generated in the positive direction while receiving the magnetic flux, and as a result, a magnetic flux change of Φc − (− Φm) = Φc + Φm occurs as shown by a solid line, and the magnetic flux change increases by Φm as compared with the conventional example. Is what you do. The reason why the output is improved by generating a magnetic flux in the opposite direction will be described with reference to FIG. 4. FIG. 4 shows actual measurement data (Mg in the figure indicates a permanent magnet). Magnetic field strength H
This is because the permeance P does not decrease in the actual use range where the ampere turn AT is large. That is, the magnetic energy w is different from the above equation. (L: inductance, I: current when the magnetic permeability μ = constant), it can be seen from this equation that the magnetic energy w increases with an increase in the inductance L. The inductance L is represented by L = μSN ² / l [H] (2) (μ: magnetic permeability, S: sectional area, N: number of turns, l: magnetic path length). Further, since the permeance P is P = μS / l (3), the inductance L is L = PN ² [H] (4) from the equations (2) and (3), and the magnetic energy w becomes It can be seen that it increases in proportion to the permeance P. That is, as shown in FIG. 4, by generating the magnetic flux Φm in the reverse direction, the permeance does not become small in the actual use range, so that a large magnetic energy can be obtained. Equations (1) and (2)
From (3), if the magnetic energy w is μ = constant, w = μSN ² I ² / 2l [J] (5) can be rewritten. If the magnetic permeability μ is an increment magnetic permeability (μ = ΔB / ΔH), the magnetic permeability μ is BH
Since the BH curve is determined by the slope of the curve, if the BH curve does not enter the saturation region, that is, if μ = constant, the magnetic energy w increases in proportion to the square of the current I, The output can be improved.

Next, an experimental example of the ignition coil according to the present invention will be described.

First, the conversion efficiency of magnetic energy of a 10 × 10 mm core (made of silicon steel plate) to a spark plug was calculated from FIG. In this case, the magnetic energy of the magnetized core is , And the hatched portion in FIG. In this case, the core dimensions were magnetic energy ignition energy efficiency 10 × 10 mm 47.6 mJ 32.0 mJ 67%.

Subsequently, the cross-sectional area and shape of the core were determined. That is, the sixth
As shown in the figure, as a result of conducting an experiment before and after inserting permanent magnets into cores of various sizes, permanent magnets (10 x 10 x 2 mm thick) were used for the same winding specification.
Since core area S Using it can be reduced by about 40% was found to, S = 8 × as 60% of 10 × 10 = 100mm ²
8 was determined to be 64 mm ² .

Next, the magnetic energy of a core of this size when no permanent magnet was inserted was calculated from FIG.
It was 34.4 mJ.

Next, the permeance coefficient was calculated from the following equation by the provisional magnetic path method.

Permeance coefficient ∝S / l ≒ 5.3 Next, the magnetic energy Δw of the core to be increased by interposing the permanent magnet was calculated from the above.

Δw = 47.6−34.4 = 13.2 mJ From FIG. 8, the increase ΔB of the magnetic flux density B is ΔB = 0.23 [T].

Next, based on the experimental data shown in FIGS. 8 (a) to (d) and FIG. 6, the size of the permanent magnet was changed to 7 × 8 × 2 mm in thickness.
It was tentatively decided. The permanent magnet material is a samarium / cobalt magnet CORMAX-2300 (Sumitomo Special Metals,
Product name).

Next, the operating point of this permanent magnet was confirmed. The condition under which the permanent magnet operates stably is as shown in FIG. 9: Hc-worst> Hd + Hi (6). In this case, Hc: coercive force Hc-worst: worst value of coercive force Hc in consideration of ambient temperature, conditions, manufacturing variations, etc. Hd: self-demagnetizing field Hi: magnetic field generated in the magnet by the coil, Hi = k · AT / lg
(AT: magnetomotive force (ampere turn), k: magnetomotive force loss coefficient, l
g: gap length) As a result, the values calculated from FIG. 9 are Hd = 1.6K0e, Hi
= 3.9K0e, Hc-worst = 8.8K0e (temperature 140 ° C, catalog value). Therefore, from equation (6), 8.8> 1.6 + 3.9, which was judged to be satisfactory. Also, it was confirmed from FIG. 9 that the magnetic energy increased by ΔB = 0.4 [T], and the increase was as follows: w = (ΔB ′ / ΔB) · Δw = 0.4 / 0.23 × 13.2 = 23.0 mJ, and the total magnetic energy was 34.4 + 23.0 = 57.4 mJ, so it could be judged to be satisfactory.

The results of the experiment described above are summarized in FIG. 10, and the measured values are as follows.

As described above, the values obtained through the experiment also show that the magnetic energy and the ignition energy are significantly increased by the insertion of the permanent magnet, and are increased by 50% in the experimental example.
Accordingly, the core size can be reduced, and the size of the ignition coil itself can be reduced in size and weight, so that the layout at the time of mounting on a vehicle is facilitated, and further, there is an advantage that costs such as material costs are reduced. Incidentally, in the above, as shown in FIG. 9, the permanent magnet is Hc (preferably Hc-wors) at the operating temperature.
t) Use within the range of> Hd + Hi, and use it as long as the permanent magnet is not destroyed by the magnetic field Hi due to the primary coil. From that point, as described above, Hc
Rare earth / iron magnets, such as samarium / cobalt magnets, are preferred. Further, the permanent magnet inserted into the air gap portion has a significantly lower magnetic permeability than the material of the core (silicon steel plate or the like), so that it can function not only as a magnetic flux generating means but also as an original air gap means. It goes without saying that you can do it.

Thus, a second feature of the present invention resides in that such a permanent magnet magnetic material (hard material) is inserted at a position where its magnetization direction is orthogonal to the center axis of the coil. No.
Referring to FIG. 11, as shown in FIG. 11A, a permanent magnetizable magnetic material (hard material) 32 is formed in an air gap portion 26 formed between the insertion core 10c and the side core 10b.
Then, as shown in FIG. 3B, the ignition coil, into which the magnetic material has been assembled, is
In 0, the switch 102 is turned on to excite the magnetizing coil 106 from the magnetizing power supply 104 for a short time, and the magnetic material 320 is magnetized into the permanent magnet 32. Thus, in this case, the magnetization yoke 100
A magnetic flux path as shown by an arrow 108 is formed between the N and S poles. In this case, there is a coil portion composed of the primary coil 14 and the secondary coil 18 near the magnetic material 320, and when the magnetic flux passes through such a coil, the primary coil and the secondary coil change in the magnetic flux per unit time. An electromotive voltage corresponding to the amount dΦ / dt is induced, and in a severe case, there is a disadvantage that the coil is broken down. Thus, such an induced electromotive voltage is generated according to a change in magnetic flux passing through the coil, and in the method of manufacturing an ignition coil according to the present invention, the magnetization direction of the magnetic material 320,
That is, the air gap portion 26 is formed between the insertion core 10c and the side core 10b so that the magnetic flux path 108 of the magnetized yoke and the center axis 110 of the primary coil and the secondary coil are orthogonal to each other. Since the magnetic material 320 is arranged and magnetized, such a disadvantage does not occur. That is, as shown in FIG. 12, when the air gap portion is formed at an appropriate position of the side core 10b and the magnetic material 320 is inserted therein, the magnetization direction of the magnetic material (arrow 108) and the center axis 110 of the coil Are parallel to each other and the magnetic flux penetrates through the coil, causing problems such as dielectric breakdown.In the present invention, since the magnetizing direction and the center axis of the coil are arranged so as to be orthogonal to each other, it is possible to prevent such a problem. You can do it.

(Effects of the Invention) The present invention provides a closed magnetic path core by inserting a permanent magnet into the core of an ignition coil including a magnetizable core and a primary coil and a secondary coil wound around the core, In a method of manufacturing an ignition coil configured to generate a magnetic flux in a direction opposite to a magnetic flux generated when a current is applied to a primary coil, a magnetization direction of the closed magnetic path core is orthogonal to a center axis of the ignition coil. Since the magnetic material capable of being permanently magnetized is interposed at the position and then the magnetic material is magnetized, the magnetic energy that can be extracted from the core by the amount of the magnetic flux in the opposite direction can be increased. As a result, in a core having the same cross-sectional area, the magnetic energy can be increased as compared with the conventional case, so that the cross-sectional area of the core can be reduced and the ignition coil itself can be reduced in size and weight. Further, since a magnetic material that can be permanently magnetized is inserted into the closed magnetic path core at a position where its magnetization direction is orthogonal to the center axis of the ignition coil, and then the magnetic material is magnetized, the magnetic material is attached. There is an advantage that inconvenience such as dielectric breakdown of the coil does not occur when magnetized.

[Brief description of the drawings]

1 is an explanatory view schematically showing an ignition coil according to the present invention, FIG. 2 is an explanatory longitudinal sectional view showing a more detailed configuration of the ignition coil of FIG. 2, and FIG. 3 is an ignition coil according to the present invention. FIG. 4 is a permeance-AT characteristic diagram for explaining the reason, and FIG. 5 is a BH curve used for calculating the magnetic energy of a 10 × 10 mm core in an experimental example. FIG. 6, FIG. 6 shows previous experimental data obtained by examining magnetic characteristics of cores of various sizes with and without a permanent magnet interposed therebetween, FIG. 7 shows a BH curve diagram used in the above experimental example, FIG. 8 (a) to 8 (d) are explanatory diagrams showing the relationship between the thickness of the permanent magnet used in the experimental example and the permeance coefficient, etc. FIG. 9 is a demagnetization curve diagram of the permanent magnet used in the experimental example, FIG. FIG. 10 is a BH curve diagram showing the measurement results of the experimental example, and FIG. 11 ( ) To (b) is an explanatory view and FIG. 12 shows a step of a method for manufacturing an ignition coil according to the present invention is an explanatory diagram showing a characteristic of an ignition coil according to the present invention. 10 cores (10a center core, 10b side cores,
10c: Insert core), 12, 16: Bobbin, 14: Primary coil, 18: Secondary coil, 26: Air gap, 32:
Permanent magnet, 100 ... magnetized yoke, 104 ... magnetized power supply, 106
…… Magnetized coil, 320 …… Magnetic material

Claims (1)

(57) [Claims] 1. An ignition coil comprising a magnetizable core and a primary coil and a secondary coil wound around the core, a permanent magnet is inserted into the core to form a closed magnetic circuit core, and power is supplied to the primary coil. In the method of manufacturing an ignition coil configured to generate a magnetic flux in a direction opposite to a magnetic flux generated thereby, a.A magnetizing direction of the closed magnetic path core is set at a position orthogonal to a center axis of the ignition coil. Interposing a permanent magnetizable magnetic material; and b. Then magnetizing the magnetic material.