JPH01185907A - Ignition coil - Google Patents

Abstract

PURPOSE:To reduce the volume of a core and to make the core small-sized and lightweight by a method wherein a flux generation means is arranged at the core, the magnetic flux in the direction opposite to the magnetic flux to be generated when electricity is applied to a primary coil is generated and the flux generation means is arranged in a position other than a region where a coil is wound. CONSTITUTION:A flux generation means 32 is arranged at a core 10; the magnetic flux is generated in the direction opposite to the magnetic flux to be generated when electricity is applied to a primary coil 14; the flux generation means 32 is arranged in a position other than a region where coils 14, 18 are wound on the core 10. Accordingly, it is possible to increase magnetic energy from which only the magnetic flux in the opposite direction can be taken out from the core 10; the magnetic energy can be increased as compared with a case where the flux generation means is not provided at the core of the same cross-sectional area. By this setup, it is possible to reduce a cross-sectional area of the core and to make the core small-sized and lightweight.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to improving an ignition coil for an internal combustion engine, and more specifically to improving the magnetic flux generated when a permanent magnet is inserted in the core and the primary coil is energized. This invention relates to an ignition coil that improves ignition performance by generating magnetic flux in the opposite direction.

(Prior Art) As is well known, the ignition coil of a conventional internal combustion engine consists of a core (iron core) around which a primary coil and a secondary coil are wound. It generates voltage to ignite the air-fuel mixture in the combustion chamber. An example of such a conventional technique is the technique described in Japanese Patent Laid-Open No. 58-54618, which discloses an ignition coil having a closed magnetic circuit type core.

(Problem to be solved by the invention) By the way, in the ignition coil, the magnetic energy W that the core can store per unit volume is generally (when magnetic permeability μ = constant), w = j: HdB ''4BH (J). Specifically, it is determined by the saturation magnetic flux density, which is determined by the volume of the core and the material of the core.The ignition coil is also expected to be smaller and lighter due to the layout when mounted on the vehicle. However, in order to do this, in the conventional case, the core material had to be selected with the highest possible saturation point, and as such core materials are relatively expensive and have relatively poor workability, However, it has been difficult to sufficiently reduce the size and weight of the ignition coil.

Therefore, an object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and it is an object of the present invention to provide an ignition coil that can be made smaller and lighter by reducing the volume of the core.

(Means and operations for solving the problems) In order to achieve the above object, the present invention provides an ignition coil comprising a magnetizable closed magnetic circuit core and a primary coil and a secondary coil wound around the core. A magnetic flux generating means is disposed in the core to generate a magnetic flux in the opposite direction to the magnetic flux generated when the primary coil is energized, and the magnetic flux generating means is placed in a position in the core other than the area where the coil is wound. It was configured as follows.

That is, the inventors of the present invention have searched various ways to reduce the size and weight of the ignition coil, and found that by inserting a magnetic flux generating means, such as a permanent magnet, into the core, when the primary coil is energized to generate magnetic flux, the magnetic flux is generated in the opposite direction. The present invention was made based on the discovery that the magnetic energy that can be taken out from the core increases by generating magnetic flux in the core. In other words, by generating magnetic flux in the opposite direction even in cores with the same cross-sectional area, the same material, and the same winding specifications, the magnetic energy that can be extracted from the core increases compared to the case otherwise. They discovered that this allows the ignition coil itself to be made smaller and lighter by reducing the cross-sectional area of the core. The present invention was made based on the discovery that by selecting a position outside the coil winding area of the core as the insertion position of the permanent magnet, the magnetic energy that can be extracted from the core can be further increased.

(Example) Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. For convenience, the ignition coil according to the present invention will be described with reference to FIG. has a main body portion consisting of a center core 10a and a side core lOb, and is configured such that an insertion core 10c can be freely fitted into the open end thereof. A bobbin 12 is provided around the outer periphery of the center core 10a, and a primary coil 14 having an appropriate number of turns is wound on the bobbin 12 as is well known.

A second bobbin 16 having comb-like protrusions is disposed outside the primary coil 14, and a secondary coil 18 is similarly wound thereon with an appropriate number of turns. These coils 14, 18 are connected to an external circuit through terminals (not shown) in a known manner (note that the number of turns of the coils 14, 18 is simplified for ease of illustration). A case 2 is provided outside the secondary coil 18.
0 is attached to protect the coils 14 and 18 from the outside, and the gap between the case 20 and the bobbin or coil described above is filled with an explosion-proof/insulating resin 22. When assembling the core 10, the center core 10a is inserted into the inner cavity of the bobbin 12, and then the insertion core 10c is fitted and integrated.
As shown in FIG. 3, an air gap portion 26 is formed between c and the side core lOb. Additionally, ears 28, 2B are formed at the ends of the center core and side cores, and mounting holes 30, 30 are bored therein.

In the above configuration, the ignition coil according to the present invention is characterized in that a permanent magnet is inserted into the core 10 as a magnetic flux generating means. That is, in the case of this embodiment, as clearly shown in FIG. 3, the permanent magnet 32 is arranged in the air gap 26 formed between the side core 10b and the insertion core 10c. To explain this point with reference to FIGS. 1 and 4, power supply voltage is supplied to the primary coil 14 wound around the core 10 from the battery 40 via an ignition key (not shown). The secondary coil 1 is cut off by a switch 42 consisting of a contact point or an igniter (both not shown), etc.
A high voltage is generated at 8, causing sparks at the discharge section 44. The configuration up to this point is no different from the prior art. Accordingly, in the present invention, by inserting the permanent magnet 32 into the core 10, the direction of generation of the magnetic flux ΦC of the primary coil generated by the connection of the switch 42 (indicated by the symbol A in FIG. 1) is controlled.
The structure is such that the magnetic flux Φ- is generated in the opposite direction (also indicated by the reference sign). That is, as shown in Fig. 4, in the conventional core, the magnetic flux ΦC in the positive direction is
In the present invention, as shown by the dashed line, the core lO receives the magnetic flux -Φm in the negative direction and generates the magnetic flux ΦC in the positive direction, and as a result, as shown by the solid line, Φc-(- The amount of change in magnetic flux is Φm)=Φc+Φm, and the amount of change in magnetic flux is increased by Φm compared to the conventional example. The reason why the output is improved by generating magnetic flux in the opposite direction will be explained with reference to Figure 5. Although the figure is actually measured data (Mg in the figure indicates a permanent magnet), it is clear from this that the output is improved by generating magnetic flux in the opposite direction. This is because the permeance P does not become small in the practical use range where the magnetic field strength H is large, that is, the ampere turn AT is large. In other words, the magnetic energy W is calculated separately from the above formula by w=S LJdl ='4L I'' [J co・・
・ ・ ・ ・ ・ ・ ・ ・ (1
) (where magnetic permeability μ is constant, L: inductance, I: current), and it can be seen from this equation that magnetic energy W increases as inductance L increases. This inductance is L=μSNz/I [H] ・
It is represented by (2) (μ: magnetic permeability, S: cross-sectional area, N: number of turns, l: magnetic path length). Also, the permeance P is P=μS/l (3), so from equations (2) and (3), the inductance L is L=
PN'' [H] ・・・・・・・・・・・・(4) From this, it can be seen that the magnetic energy W increases in proportion to the permeance P. In other words, as shown in Fig. 5, the magnetic flux increases in the opposite direction. By generating Φm, the permeance does not become small in the actual usage range, so it is possible to obtain large magnetic energy.Equations (1), (2), and (3).
), if the magnetic energy W is μ-constant, then W-μSN"1" /21 [J] ...
It can be rewritten as (5). If this magnetic permeability μ is an incremental magnetic permeability (μ−ΔB/ΔH), then the magnetic permeability μ
is determined by the slope of the B-H curve, so if the B-H curve is kept from entering the saturation region, that is, if μ is constant, the magnetic energy W increases in proportion to the square of the current ■. (
This means that 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 size 1010×10 core (made of silicon steel plate) into a spark plug was calculated from FIG. In this case, the magnetic energy possessed by the magnetized core is expressed as W-S g' HaB, and the shaded area in the figure corresponds to it. In this case, Core dimensions Magnetic energy Ignition energy Efficiency 101
0X10 47.6mJ 32. OmJ 67
%Met.

■Next, the cross-sectional area and shape of the core were determined.

That is, as shown in Figure 7, as a result of preliminary experiments with and without inserting permanent magnets into cores of various sizes, we found that with the same winding specifications, permanent magnets (10xl
If you use OxJt (2 cylinders), the core cross-sectional area S will be approximately 40%.
Since it was found that it is possible to reduce
It was determined that S = 8 x 8 = 64 mm'' as 60% of 0 Sir 2.

■Next, we calculated the magnetic energy from Figure 8 for a core of this size without inserting a permanent magnet, and found that
It was 34.4 mJ.

(2) Next, the permeance coefficient was calculated using the temporary magnetic path method using the following formula.

Permeance coefficient ■S/1ζ5.3 ■Next, from the above ■■, the magnetic energy ΔW of the core to be increased by inserting a permanent magnet was calculated.

6w = 47.6-34.4 = 13.2 m J
From Figure 8, the increase ΔB in magnetic flux density B is ΔB=0.23
It became [T].

-〇 Next, from the experimental data shown in Figures 9 (a) to (d) and Figure 7, the size of the permanent magnet was determined to be 7 x 8 x thickness 2.
It was tentatively determined to be 11IIIl. In addition, the material of the permanent magnet is samarium cobalt magnet CORMAX-230.
0 (manufactured by Sumitomo Special Metals, trade name) was selected.

■Next, the operating point of this permanent magnet was confirmed. The conditions for this permanent magnet to operate stably are as shown in Figure 10.
). In this case, Hc: Coercive force Hc-worst: Worst value of coercive force Hc taking into consideration operating ambient temperature, conditions, manufacturing variations, etc. Hd: Self-demagnetizing field Hl: Magnetic field generated within the magnet by the coil, Hi = - AT/Ig (AT: Magnetomotive force (ampere turns)
, k: magnetomotive force loss coefficient, 1g: gap length) As a result, the calculated value from Figure 10 is Hd = 1°6
KOe, Hi =3.9 KOe,, Hc-wors
t = 8.8 KOe (temperature 140°C, catalog value)
It became. Therefore, from equation (6), 8.8 > 1.6 +
The score was 3.9, which was judged to be satisfactory. Also, from Figure 10, it was confirmed that the magnetic energy was amplified by an increase of ΔB = 0.4 [T], so the increase was w = (ΔB'/ΔB) ・ΔW = 0.410.23X
13.2 = 23.0 m J, and the total magnetic energy is 34.4 + 23.0
= 57.4 mJ, so it was judged to be satisfactory.

The experimental results for the above are summarized as shown in Figure 11, and the actual measured values were as follows:
Magnetic energy [mJ] Actual value Calculated value 10 x 10 without magnet 47.6. - 8 magnets without 8 magnets 34.4 - 8 magnets with 8 magnets 51.1 57.4 Magnetic flux density increase ΔB [T] Actual value Calculated value to With magnet 0.25 0.4 Ignition energy [
mJ] Actual value Calculated value 10 magnets 10 without magnets 32.0 - 8 magnets without 8 magnets 20.0 23.08 with 8 magnets 33.0 34.2 (Ignition energy calculation value is calculated by multiplying magnetic energy by efficiency As described above, the values obtained through experiments also indicate that by inserting the magnetic generation means, the magnetic energy and ignition energy can be significantly improved, by 50% in the case of the experimental example. Therefore, it is possible to reduce the core size and make the ignition coil itself smaller and lighter, which facilitates the layout when mounted on a vehicle, and also simplifies the installation method and reduces costs such as materials. Benefits arise. In addition, as mentioned above with reference to FIG. 10, the permanent magnet has Hc (preferably Hc -worst)> at the operating temperature.
It is used within the range of Hd+Hi and as long as the permanent magnet is not destroyed by the magnetic field Hi caused by the primary coil. From this point of view, as mentioned above, currently H
Rare earth/iron based magnets such as samarium/cobalt based magnets have a large c value.

The permanent magnet inserted into the air gap has a much lower magnetic permeability than the core material (silicon steel plate, etc.).
Although it can function not only as a magnetic flux generating means but also as an original air gap means, a further feature of the present invention is that the near gap formation position, that is, the insertion position of the permanent magnet, is located in the coil winding area. There is a point left out. To explain this point with reference to FIG. 12, an air gap portion is formed in the center core region (indicated by diagonal lines in the figure) around which the primary coil 14 and the secondary coil 18 are wound in the core 10. It is constructed so that a permanent magnet is not inserted there, and is inserted in other areas. That is, the present inventors have developed a center core 10a as shown in FIG.
When an air gap is formed in the coil winding area and a permanent magnet is inserted therein (indicated by ■ in the figure), when an air gap is formed in the side core 10b and a permanent magnet is inserted there (indicated by ■ in the figure) As a result of experiments, we found the following cases: Actual measurements were obtained.

■ ■ ■ Secondary generated voltage [kV] 26.5 32.7
33.3 Ignition energy [mJ] 24.4 3
2.4 34.9 Primary inductance [mH] 7.1
9 11.98 12.05 In the above case, it can be seen that the ignition energy is relatively low in the case of ■.
In the case of , since there are coils on both sides of the insertion position, the leakage magnetic flux in the air gap is blocked by the magnetic field generated when current flows through the coil, and a magnetic flux path is only formed in an area equal to the core cross section. It is thought that the permeance decreases, and as a result, the inductance decreases as shown in equation (4) above, and the magnetic energy also decreases. On the other hand, in the case of ■■, the magnetic flux path formed in the air gap exceeds the area corresponding to the core cross section and extends to the outside, as shown by the arrow attached to ■, so the leakage magnetic flux acts effectively. without degrading permeance.
As a result, it is thought that the magnetic energy also increases.

For the above reasons, in this embodiment, as shown in FIG.
The air gap part 26 is formed at the position (3), and the permanent magnet 32 is inserted therein, thereby further improving the ignition performance.

(Effects of the Invention) The ignition coil according to the present invention includes a magnetizable closed magnetic circuit core, a primary coil and a secondary coil wound around the core, and a magnetic flux generating means is disposed in the core. Since magnetic flux is generated in the opposite direction to the magnetic flux generated when the coil is energized, and the magnetic flux generating means is arranged in a position other than the area where the coil is wound in the core, the magnetic flux in the opposite direction is generated. This makes it possible to increase the magnetic energy that can be taken out from the core. Therefore, in a core with the same cross-sectional area, it is possible to increase the magnetic energy compared to the case without conventional magnetic flux generation means, so it is possible to reduce the cross-sectional area of the core and make the ignition coil itself smaller and lighter. I can do it. Furthermore, since the magnetic flux generating means is arranged so as to be inserted into the core outside the coil winding area, there is an advantage that the increased magnetic energy can be used more effectively.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram schematically showing an ignition coil according to the present invention, Fig. 2 is an explanatory longitudinal cross-sectional view showing a more detailed configuration of the ignition coil in Fig. 1, and Fig. 3 is a permanent FIG. 4 is a B-H curve diagram explaining the increase in magnetic energy of the ignition coil according to the present invention, and FIG. 5 is a permeance-AT characteristic diagram explaining the reason. , Figure 6 is a B-H curve diagram used to calculate the magnetic energy of a 10 x 10 mm core in the experimental example, and Figure 7 is a diagram of cores of various sizes with and without permanent magnets inserted. Figure 8 shows the B-H curve diagram used in the above experimental example, and Figure 9 shows the previous experimental data in which the magnetic properties were investigated.
Figures (a) to (d) are explanatory diagrams showing the relationship between the thickness of the permanent magnet used in the experimental example and the permeance coefficient, etc.
The figure is a demagnetization curve diagram of the permanent magnet used in the above experimental example.
Figure 1 is a B-H curve diagram showing the measurement results of the above experimental example.
FIG. 2 is an explanatory diagram showing the insertion position of the permanent magnet in the core, and FIG. 13 is an explanatory diagram showing the experiment. 10...core, 12.16...bobbin, 14...
Primary coil, 18...Secondary coil, 26...Air gap portion, 32...Permanent magnet (magnetic flux generating means) Applicant: Honda Motor Co., Ltd. Agent
Patent Attorney Yoshi 1) Yutaka Figure 1 Figure 3 M IIJIAJ [First Figure 6 Figure 8 B Figure 9 11\□ Mg4v □Puni ノ1\□M9 Thick--Forked; = Figure 10 Figure 11 figure

Claims (2)

[Claims] (1) In an ignition coil consisting of a magnetizable closed magnetic circuit core and a primary coil and a secondary coil wound around the core,
A magnetic flux generating means is disposed in the core to generate a magnetic flux in a direction opposite to the magnetic flux generated when the primary coil is energized, and the magnetic flux generating means is placed at a position in the core other than the area where the coil is wound. An ignition coil characterized in that it is configured such that it is arranged in (2) The ignition coil according to claim 1, wherein the magnetic flux generating means is a permanent magnet.