JPH09129459A - Ignition coil for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ignition coil for an internal combustion engine, in which the insulation of the secondary coil is improved. SOLUTION: A secondary spool 510 is molded with resin into a bottomed cylinder, and its ends are provided with flanges 510a and 510b, between which flanges 510d, 510e and 510f are provided toward the high-voltage side. The positions of the flanges 510d, 510e and 510f are set according to the potential distribution in a secondary coil 512. Specifically, the secondary voltage in the secondary coil 512 increases with the number of its turns; therefore, the flange 510d is positioned where the number of turns of the secondary coil is reached. The flanges 510e and 510f are positioned in the same way.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an elongated cylinder type ignition coil for an internal combustion engine (hereinafter referred to as "ignition coil").

[0002]

2. Description of the Related Art In recent years, there is a trend to make an ignition coil into an elongated cylindrical shape in order to mount the ignition coil in a plug hole formed in an engine block, for example, an elongated cylindrical type having an outer diameter of 30 mm or less. Ignition coils are required. Therefore, it is necessary to reduce the size and diameter of the secondary coil that generates a high voltage.

As an example of reducing the size and diameter of the secondary coil, the secondary coil is wound in a so-called "oblique double winding", in which wire rods are obliquely overlapped and wound around the outer peripheral surface of the bobbin at a predetermined inclination angle. It is known that the Then, as an example of using the "oblique double winding", there is a method of winding an electromagnetic coil disclosed in Japanese Patent Publication No. 2-18572.

[0004]

However, according to the winding method of the electromagnetic coil disclosed in Japanese Patent Publication No. 2-18572, the wire rod is wound around the winding frame by the oblique heavy winding described above. For example, as the secondary coil becomes smaller and smaller in diameter, the outer diameter of the wire material becomes extremely thin, resulting in a decrease in the degree of alignment of the windings, which easily causes winding collapse during one diagonal reciprocation. In particular, the high voltage generation side of the secondary coil receives a step voltage that bounces off as a reflected voltage when the spark plug is discharged, so if this winding collapse occurs on the high voltage generation side of the secondary coil, the adjacent wire Since the potential difference between the two becomes higher than the designed value, there arises a problem that dielectric breakdown occurs between the wire rods and the dielectric strength of the secondary coil is reduced.

Here, "one diagonal reciprocation" means that the diagonally double-wound wire reciprocates once on a slope inclined at a predetermined inclination angle with respect to the outer peripheral surface of the bobbin. The purpose of the present invention is
An ignition coil for an internal combustion engine that improves the dielectric strength of the secondary coil.

[0006]

The present invention for solving the above problems employs the means described in claim 1. According to this means, the first winding portion is formed on the low voltage generating side of the tubular bobbin, and the second winding portion having a winding width narrower than that of the first winding portion is formed on the high voltage generating side. Of the secondary coil wound around the first winding portion and the second winding portion,
Since the wire rod wound around the first winding portion is diagonally heavy-winding, the secondary coil can be formed without locating the obliquely heavy-winding, which is likely to cause winding collapse, on the high voltage generation side of the secondary coil. Can be configured. Therefore, even if the wire rod is required to have a very small diameter due to the reduction in size and weight of the secondary coil, since the first winding portion located on the low voltage generation side is obliquely and heavily wound, the dielectric strength of the secondary coil is reduced. Has the effect of improving.

Further, by adopting the means described in claim 2, the number of turns of the first winding portion in one diagonal reciprocation is obtained by a potential difference obtained by the number of turns including winding collapse occurring during one diagonal reciprocation. Since the number of turns is set to be smaller than the dielectric breakdown voltage VL between the adjacent wire rods, even if the winding collapse occurs during the oblique heavy winding of the first winding portion, the potential difference between the wires is equal to the dielectric breakdown voltage. Since it is set to be lower than VL, it is possible to prevent a decrease in dielectric strength due to winding collapse or the like. Therefore, there is an effect of improving the dielectric strength of the secondary coil.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. One embodiment of the ignition coil of the present invention is shown in FIGS. As shown in FIG. 2, the ignition coil 2
Is mainly a cylindrical transformer section 5, a control circuit section 7 located at one end of the transformer section 5 for connecting and disconnecting the primary current of the transformer section 5, and a control circuit section 7 located at the other end of the transformer section 5. It is composed of a connecting portion 6 for supplying the secondary voltage of the transformer portion 5 to an ignition plug (not shown).

The ignition coil 2 is provided with a cylindrical case 100 made of a resin material, which is a housing of the ignition coil 2, and a housing chamber 102 formed inside the case 100 is for generating a high voltage. The transformer unit 5, the control circuit unit 7, and the insulating oil 29 that fills the periphery of the transformer unit 5 are accommodated. A control signal input connector 9 is provided at the upper end of the housing chamber 102, and a bottom 104 closed by the bottom of the cup 15 described later is formed at the lower end of the housing chamber 102. The outer peripheral wall of this cup 15 is
It is covered by the connection part 6 located at the lower end of the case 100.

A tubular portion 105 for accommodating an ignition plug (not shown) is formed in the connecting portion 6 by the case 100, and a plug cap 13 made of rubber is attached to the open end of the tubular portion 105. A metal cup 15 is insert-molded in the resin material of the case 100 at the bottom portion 104 located at the upper end of the tubular portion 105. Therefore, the accommodation chamber 102 and the connecting portion 6 are liquid-tightly partitioned.

The spring 17 locked to the bottom of the cup 15 is a compression coil spring, and is composed of a connecting portion 6
An electrode part of a spark plug (not shown) inserted therein is electrically contacted with the other end of the spring 17. The control signal input connector 9 is composed of a connector housing 18 and a connector pin 19. The connector housing 18 is integrally formed with the case 100, and three connector pins 19 located inside the connector housing 18 are insert-molded into the connector housing 18 so as to penetrate the case 100 and be connectable to the outside.

On the upper side of the case 100, the transformer section 5,
An opening portion 100a is formed for accommodating the control circuit portion 7, the insulating oil 29 and the like in the accommodating chamber 102 from the outside of the case 100. The opening 100a is liquid-tightly closed by the metal lid 33 being caulked and fixed to the upper part of the case 100 with the O-ring 32 interposed. Transformer part 5
Is the iron core 502, the magnets 504 and 506, the secondary spool 5
10, a secondary coil 512, a primary spool 514, and a primary coil 516.

The cylindrical iron core 502 is assembled by stacking thin silicon steel plates so that their cross sections are substantially circular. At both ends of the iron core 502, magnets 504, 5 having a polarity opposite to the direction of the magnetic flux generated by being excited by the coil.
06 are fixed by an adhesive tape. The secondary spool 510 as a bobbin is resin-molded,
It has collar portions 510a, b at both ends, and these collar portions 510a, b
It is formed in a bottomed cylindrical shape having flanges 510d, e, f on the high voltage generating side therebetween. In addition, the lower end is the bottom 51
It is almost blocked by 0c. Then, the collar portion 510a
And the flange portion 510b between the low voltage generating side (hereinafter,
It is called the "low voltage side winding part". 531 is formed. Further, a winding portion on the high-voltage generating side (hereinafter referred to as “high-voltage side winding portion”) 532 is provided between the collar portion 510d and the collar portion 510e, and a high-voltage side winding portion is provided between the collar portion 510e and the collar portion 510f. The high voltage side winding portion 534 is formed between the portion 533 and the collar portion 510f and the collar portion 510b, respectively. Here, the low voltage side winding portion 5
Reference numeral 31 corresponds to the "first winding portion" described in the claims, and the high voltage side winding portions 532, 533, 534 correspond to the "second winding portion" described in the claims. Equivalent to each.

The positions where the brim portions 510d, e, f are formed are determined by the potential distribution in the secondary coil 512, as will be described later. That is, the electric potential distribution in the secondary coil 512 is as shown in FIG.
Since the secondary voltage generated in the secondary coil 512 rises as the number of turns of 2 increases, the collar portion 510d is set to be located when the number of turns of the secondary coil 512 reaches a predetermined number.

At the bottom portion 510c of the secondary spool 510,
A terminal plate 34, to which a lead wire (not shown) drawn from one end of the secondary coil 512 is electrically connected, is fixed, and a spring 27 for contacting the cup 15 is fixed to the terminal plate 34. The terminal plate 34 and the spring 27 function as a spool-side conductive member, and the high voltage induced in the secondary coil 516 causes the terminal plate 34, the spring 27, and
It is supplied to the electrode portion of the spark plug (not shown) via the cup 15 and the spring 17.

Inside the secondary spool 510, the iron core 502 and the magnet 506 are housed.
A secondary coil 512 wound by a winding method described later is located on the outer circumference of the above, that is, on the low voltage side winding portion 531 and the high voltage side winding portions 532, 533 and 534 described above.
The resin-molded primary spool 514 has a collar portion 51 at both ends.
It is formed in a bottomed cylindrical shape having 4a and 4b, and a lid portion 5
The upper end is almost closed by 14c. A primary coil 516 is wound around the outer circumference of the primary spool 514.

An auxiliary core 508 having a slit (not shown) is mounted on the outside of the primary spool 514 around which the primary coil 516 is wound. This auxiliary core 508 is
A thin silicon steel plate is wound in a tubular shape, and a slit is formed in the axial direction because the winding start end and the winding end end are not connected, and this slit is formed from the outer peripheral position of the magnet 504 to the magnet 50.
It has an axial length that extends over 6 outer peripheral positions. This reduces the short-circuit current generated in the circumferential direction of the auxiliary core 508.

A storage chamber 1 in which the transformer section 5 and the like are stored
The inside of 02 is filled with insulating oil 29 leaving a slight air space at the upper end of the accommodation chamber 102. The insulating oil 29 has an opening 514d formed in the lower opening end of the primary spool 514, an opening 514d formed substantially in the center of the lid 514c of the primary spool 514,
It penetrates through the upper open end of the secondary spool 510 and an opening (not shown) to ensure electrical insulation between the iron core 502, the secondary coil 512, the primary coil 516, the auxiliary core 508, and the like.

The structure of the secondary coil 512 will be described with reference to FIG. As shown in FIG. 1, the secondary spool 5
Ten low voltage side winding parts 531 and high voltage side winding parts 532, 53
The secondary coil 512 wound around 3, 534 is configured by winding a wire whose outer periphery is covered with an insulating film made of, for example, amide imide, a predetermined number of times.

In the low voltage side winding portion 531, the wire 521 is obliquely double-wound to form a low voltage generating side of the secondary coil 512. Then, the high voltage side winding portion 532,
The high-voltage generating side of the secondary coil 512 is configured by continuously winding the wire 521 wound around the low voltage side winding portion 531 around the slots 533 and 534 by slot winding. In FIG. 1, reference numerals 522, 523, and 524 represent wire rods wound around the high-voltage side winding portions 532, 533, and 534, respectively. In this way, the secondary coil 5
The high voltage generating side of 12 is divided into a plurality of high voltage side winding portions and is configured by slot winding in order to make it difficult to cause winding collapse of the secondary coil 512 on the high voltage generating side.

Here, the high voltage side winding portions 532, 533, 5
The position formed by the brim portions 510d, e, and f that divide 34 will be described. As shown in FIG. 3, the secondary coil 5
The voltage generated at 12 increases as the number of turns of the secondary coil 512 increases, and this is shown in the characteristic curve. Since the slope of the characteristic curve gradually increases as the number of turns of the secondary coil 512 increases, the distance between the wire rods wound around the secondary spool 510 toward the high voltage generation side of the secondary coil 512 shown in FIG. The voltage of will also increase gradually.

Specifically, in the low voltage side winding portion 531 wound by oblique heavy winding, one reciprocating layer A corresponding to the hypotenuse of a right-angled triangular cross section forming the winding end portion 541 of oblique heavy winding is provided. The potential difference between lines becomes the highest. That is, since the potential difference between the wire rod 521a and the wire rod 521b shown in FIG. 1 is the highest, it is necessary to set the number of turns of this one reciprocating layer A so that this potential difference becomes lower than the dielectric breakdown voltage VL.
Here, the "dielectric breakdown voltage VL" means the minimum applied voltage at which two wire rods whose outer circumferences are covered with an insulating coating are electrically short-circuited when the two wire rods are adjacent to each other. It is determined by the material of the insulation coating.

By determining this dielectric breakdown voltage VL, the low voltage side winding portion 5 can be obtained from the characteristic curve shown in FIG.
The number of turns ΔNsmax of one reciprocating layer A of 31 can be obtained. Since the number of turns ΔNsmax obtained from this FIG. 4 is expected to have a winding collapse due to the oblique heavy winding, one reciprocating layer A between the wire rods 521a and 521b can be constituted by the number of turns ΔNsmax. When the winding position of the one reciprocating layer A is set according to FIGS. 3 and 4, the collar portion 510d is located slightly on the high voltage generating side of the secondary spool 510 from the turning point of the one reciprocating layer A. I understand that it is good. The other reciprocating layers of the low-voltage side winding portion 531 can be configured with the number of turns ΔNsmax or less because the line potential difference between each of them is lower than the line potential difference between the wire rods 521a and 521b.

The position where the brim portion 510e is formed is at the brim portion 5e.
10e is the high voltage winding portion 53 together with the above-mentioned collar portion 510d.
Since 2 is formed, it is set as follows. The number of turns ΔN ₂₃ shown in FIG. 4 is the same as the number of turns ΔNsmax described above.
The number of turns when the potential difference between the wire rods 522a and 522 having the highest line potential difference among the wire rods 522 slot-wound around the high voltage side winding portion 532 reaches the dielectric breakdown voltage VL is shown. That is, the wire 522b located on the outermost periphery of the high voltage side winding portion 532 and the wire 522 located one step inside thereof.
The number of turns that can be wound in one round trip of a is determined by the number of turns ΔN ₂₃ . Therefore, this number of turns ΔN
_Since half the number of turns of ₂₃ corresponds to the number of turns from the flange portion 510d to the flange portion 510e, it is sufficient to form the flange portion 510e at a position advanced to the high voltage generation side by the number of turns obtained from ΔN 23/2. I understand.

The position where the brim portion 510f is formed is at the brim portion 5f.
It is set similarly to the position of 10e. Number of turns ΔN shown in FIG.
₂₂ is a wire rod 5 that is slot-wound around the high voltage side winding portion 533.
23, the wire 523a having the highest line potential difference,
The number of turns when the potential difference between b reaches the dielectric breakdown voltage VL is shown. Half the number of turns ΔN ₂₂ is the flange 510.
This corresponds to the number of turns from e to the flange portion 510f. Therefore, it can be seen that it is sufficient to form a flange portion 510f to a position advanced in number of coils bamboo high voltage generating side obtained from ΔN _22/2.

The position at which the collar portion 510b is formed is also at the collar portion 51.
It is set similarly to the positions of 0e and f. Number of turns Δ shown in FIG.
N ₂₁ is a wire rod 524 having the highest line-to-line potential difference among the wire rods 524 slot-wound around the high voltage side winding portion 534.
The number of turns when the potential difference between a and b reaches the dielectric breakdown voltage VL is shown, and half the number of turns ΔN ₂₁ is the collar portion 5.
This corresponds to the number of turns from 10f to the flange portion 510b.
Therefore, it can be seen that it is sufficient to form a flange portion 510b to the advanced position to the number of coils bamboo high voltage generating side obtained from ΔN _21/2.

According to this embodiment, the secondary spool 510 forming the secondary coil 512 is formed with the low voltage side winding portion 531 and the high voltage side winding portions 532, 533 and 534, and the low voltage side winding portion 531 is formed. Winding the wire rod 521 by diagonal double winding,
Wires 522, 5 are attached to the high voltage winding portions 532, 533, 534.
By winding 23 and 524 by the slot winding, the diagonal heavy winding in which the winding collapse easily occurs is formed in the secondary coil 512.
Secondary coil 512 without being positioned on the high voltage generating side of
Can be configured. As a result, the high voltage side winding portion 5
Since the wire material is wound around the slots 32, 533, and 534 by slot winding, the high voltage generation side of the secondary coil 512 can be configured without causing winding collapse such as oblique double winding. Further, the winding width of the low voltage side winding portion 531 is set so that the potential difference between lines becomes lower than the dielectric breakdown voltage VL even if the winding collapse occurs in the middle of the oblique heavy winding due to the formation position of the flange portion 510d. Therefore, it is possible to prevent a decrease in dielectric strength due to winding collapse. Therefore, even if the diameter of the wire rod is required to be extremely small due to the reduction in size and weight of the secondary coil 512, the low-voltage side winding portion 53 that is obliquely heavy-wound.
No. 1 does not cause winding collapse due to insulation breakdown, and therefore has the effect of improving the dielectric strength of the secondary coil.

[Brief description of the drawings]

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

FIG. 2 is a vertical sectional view of an ignition coil in which a secondary coil of this embodiment is assembled.

FIG. 3 is a characteristic diagram showing a potential distribution in a secondary coil.

FIG. 4 is an enlarged view of a one-dot chain line IV shown in FIG. 3 within a circle.

[Explanation of symbols]

 2 Ignition coil 5 Transformer part 6 Connection part 100 Case (housing) 510 Secondary spool (bobbin) 512 Secondary coil 516 Primary coil 531 Low voltage side winding part (first winding part) 532 High voltage side winding part (first 2 winding part) 533 high voltage side winding part (second winding part) 534 high voltage side winding part (second winding part)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masami Kojima 1-1-1, Showa-cho, Kariya city, Aichi prefecture Nihon Denso Co., Ltd.

Claims (2)

[Claims] 1. An ignition coil for an internal combustion engine, wherein a high voltage is generated in the secondary coil by a mutual induction effect generated between a primary coil and a secondary coil housed in a cylindrical housing. A tubular bobbin that forms a first winding portion on the voltage generation side and forms a second winding portion having a winding width narrower than that of the first winding portion on the high voltage generation side; A wire rod wound around the winding portion and the second winding portion to form the secondary coil, the wire rod being diagonally double-wound around the first winding portion. Ignition coil for internal combustion engine. 2. The number of turns of the first winding part in one diagonal reciprocation is such that the potential difference obtained by the number of turns including winding collapse that occurs during one diagonal reciprocation is a dielectric breakdown voltage V between the adjacent wire members.
The ignition coil for an internal combustion engine according to claim 1, wherein the number of turns is set to be smaller than L.