JPH09275026A - Ignition coil in internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ignition coil with good dielectric strength and output voltage high enough to ignite an engine, by improving a magnetic shield effect and increasing an, insulation distance between a secondary coil high voltage part and an exterior core. SOLUTION: An exterior core 13 to be engaged with a circumferential part of a tube-shaped resin case 6 is made up of a plurality of shield tubes 13a to 13c engaged inside and outside. An axial length of the outer shield tube 13c is longer than that of an open magnetic circuit core 3, while each end part of the outer shield tube 13c is elongated from the front and rear ends of the open magnetic circuit core 3 in the tube-shaped case 6. At the same time, an axial length of the inner shield tube 13a is shorter than that of the main winding part of a secondary coil 2, while each end of the inner shield tube 13a doesn't extends beyond each end of the open magnetic circuit core 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention inserts a high-voltage terminal into a plug hole provided in each cylinder of an engine and electrically connects a high-voltage terminal to a head terminal of an ignition plug located at the bottom of the plug hole. The present invention relates to an elongated tubular ignition coil that applies a voltage.

[0002]

2. Description of the Related Art As an ignition coil used in this way,
The open magnetic circuit iron core is inserted into a bobbin whose front end is made of an insulating material, and a primary coil and a secondary coil are concentrically provided outside the bobbin, and these are arranged concentrically in an insulating case. Epoxy resin is cast into the case to open the magnetic core,
JP-A-5-13967 discloses a bobbin in which a primary coil and a secondary coil are fixed in an epoxy resin layer, and a cylindrical outer iron core having a crack, which is formed by rolling a silicon steel plate and the like, is fitted outside an insulating case. Is known from. This exterior iron core
The open magnetic circuit core at the center constitutes a substantially closed magnetic circuit, and protects the ignition coil so that the ignition coil is not magnetically affected from the outside. Moreover, the cracks in the outer core reduce unnecessary eddy currents that are likely to occur on the surface of the outer core during operation of the ignition coil. The high-voltage terminal is attached to the closed front end of the bobbin via an insulating material, and protrudes outward from the front end of the epoxy resin layer.

[0003]

In the ignition coil for an internal combustion engine mounted in the plug hole of the engine, the outer diameter of the ignition coil is 22 because the inner diameter of the plug hole is small.
Since the gap between the inner diameter of the plug hole and the outer diameter of the ignition coil is only 0.5 to 1 mm in addition to being restricted to 25 mm to 25 mm, the magnetic flux of the ignition coil can be applied to the plug hole made of aluminum or iron. Leaks, eddy currents flow in the plug hole, and the spark energy of the ignition coil is attenuated. For this reason, if a 0.35 mm-thick silicon steel plate is used for the outer core, it is necessary to stack at least three sheets to provide sufficient magnetic shielding. However, if the laminated thickness of the outer core is increased in this way, the outer diameter of the ignition coil is restricted, so that the insulation distance between the high voltage part of the secondary coil and the outer core is reduced, resulting in a decrease in insulation. Therefore, it becomes very difficult to generate the high voltage necessary for ignition of the engine within the allowable outer diameter size and to ensure sufficient dielectric strength.
For this reason, an ignition coil that requires about 40 mJ of spark energy for a spark plug, such as a lean burn engine, has not been put into practical use.

[0004]

Means for Solving the Problems] Therefore, the present invention is a magnetic flux distribution of the exterior in the core of the ignition coil are concentrated in the central portion in the axial direction of the outer core, as shown in FIG. 5, the outer core Focusing on the fact that the magnetic flux distribution is extremely small near both ends in the axial direction, increasing the number of stacks in the central portion of the outer core in the axial direction and reducing the number of stacks near both ends in the axial direction of the outer core, The insulating distance between the outer core and the secondary coil high voltage portion located inside the case near one end in the axial direction of the outer core is maintained without impairing the magnetic shield effect of the iron core.

[0005]

Therefore, the ignition coil for an internal combustion engine according to the present invention has an open magnetic circuit core in the center of an elongated cylindrical case made of synthetic resin having a high voltage terminal at a closed front end, and an external magnetic core. The primary coil and the secondary coil are arranged concentrically, and the open magnetic circuit core, the primary coil and the secondary coil are fixed in a thermosetting insulating resin layer cast in a cylindrical case, and In an ignition coil for an internal combustion engine, wherein a cylindrical outer core made of a magnetic metal plate is provided outside the cylindrical case, the outer core is composed of a plurality of shield cylinders fitted inside and outside, and an axial direction of an outer shield cylinder. The length is longer than that of the open magnetic circuit core, and the front and rear ends of the core are made to project beyond the front and rear ends of the open magnetic circuit core in the cylindrical case, and the axial length of the inner shield cylinder The length is shorter than the main winding part of the secondary coil, and the front and rear ends are So as not to exceed the front end and rear end parts, characterized and outer shield tube, in that a inner shield tube outside of the tubular casing. In this case, the outer casing of the outer core is fitted to the outer periphery of the tubular case,
An outer ring-shaped recess is provided in which the outer peripheral surface of the outer shield tube is flush with the outer surface of the tubular case. It is preferable to provide an annular inner recess whose outer peripheral surface is flush with the outer peripheral surface of the annular outer recess. In addition, an elongated cylindrical case made of synthetic resin is divided into two parts at the front end of the annular outer recessed portion into a head portion having a high-voltage terminal and a cylindrical portion having an outer annular recessed portion and an annular inner recessed portion on the outer periphery. An inner shield cylinder consisting of two semi-cylindrical shaped pieces formed of silicon steel plate is attached to the outer periphery of the recess so as to face each other, and an outer shield cylinder formed by rolling the silicon steel plate into a cylindrical shape is formed on the outer periphery of the annular outer recess. It is preferable to fit from the annular outer recess, which is the front end of the tubular portion, to the rear end of the recess, and to connect and fix the rear end of the head portion and the front end of the tubular portion in series.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In each of the illustrated embodiments, 1 is a primary coil,
Reference numeral 2 indicates a secondary coil, and 3 indicates an open magnetic circuit core. Open magnetic circuit core 3
Is a well-known one formed by laminating a large number of strip-shaped directional or non-oriented silicon steel sheets so that the cross-sectional shape is close to a circular shape, and the axial length L1 is about 70 mm. In the middle of the process, an insulating sheet 4, for example, a heat resistant insulating sheet in which a glass base cloth is impregnated with epoxy resin is wound, and the primary coil 1 is wound on the insulating sheet 4. The secondary coil 2 is wound around the outer periphery of the secondary bobbin 5 in a divided winding, though not shown in the drawing. The axial length of the primary coil is approximately equal to the axial length L2 (about 50 mm) of the main winding portion of the secondary coil. The main winding part of the secondary coil is the main winding part required to output the secondary voltage and spark energy required for the ignition coil, and the high voltage side of the secondary coil during spark discharge. And a small winding part for auxiliary winding to alleviate the high voltage transiently applied to both terminals on the low voltage side, and to connect both terminals on the high voltage side and the low voltage side to the high voltage terminal and the primary terminal. It is a winding part that does not include a trivial winding part to draw out the terminal wire.

In the first embodiment shown in FIG. 1, reference numeral 6 denotes a cylindrical tubular case made of synthetic resin and having an outer diameter of 22 to 25 mm, and a plug engaging tube which is concentric with a closed portion at its front end. 7 protrudes forward, and a high voltage terminal 8 is attached to the through hole of the plug engagement cylinder. Inside this tubular case, 1
A secondary coil wound around a secondary bobbin 5 is concentrically arranged around the closed magnetic circuit core 1 around which the secondary coil is wound around the outer circumference, and the primary terminal 11 is provided on the connector portion 10 protruding from the outer circumference.
The synthetic resin terminal support cylinder 9 with the attached is fitted and fixed to the inner circumference of the rear end of the cylindrical case, and the high voltage terminal 8 and the high voltage side of the secondary coil, the low voltage side of the secondary coil and the primary coil are connected to the primary coil. Terminal 1
1 is electrically connected to the inside of the rear cylinder, a thermosetting insulating resin is vacuum-cast into the cylindrical case from the inside of the rear cylinder, and a primary coil is wound around the cured thermosetting insulating resin layer 12 to form a closed magnetic field. The secondary coil wound around the road core 1 and the secondary bobbin 5 is fixed.

On the outer circumference of the cylindrical case, a thickness of 0.35 to
An exterior iron core 13 is provided which is formed of a 0.5 mm grain-oriented or non-oriented silicon steel plate and which is formed of three cylindrical shield cylinders fitted inside and outside. The axial length of the inner shield cylinder 13a having the smallest diameter may be 50 to 60% of the axial length L2 (about 50 mm) of the main winding portion of the secondary coil described above, for example, about 30 mm. is there. The axial length of the intermediate shield tube 13b, which fits the inner shield tube 13a on the inner circumference, is, for example, 60 mm, which is slightly longer than L2.
The axial length of the outermost shield cylinder 13c having the largest diameter that fits the intermediate shield cylinder 13b on the inner circumference is longer than the axial length L1 (70 mm) of the open magnetic circuit core, for example, 90 mm. is there. The axial lengths of the plurality of shield cylinders that are fitted inside and outside the outer core are selected so that the magnetic flux density of each shield cylinder is as uniform as possible from the distribution state of the magnetic flux.

In the inner shield cylinder 13a, the front and rear ends of the main winding portion of the secondary coil in the cylindrical case protrude from the front and rear ends of the shield cylinder 13a by substantially the same length. It is arranged on the outer circumference of the cylindrical case so that Further, the front and rear ends of the intermediate shield tube 13b are connected to each other within the tubular case.
It is arranged on the outer circumference of the inner shield cylinder 13a so as to project from the front and rear ends of the main winding portion of the next coil by approximately the same length. The front and rear ends of the outer shield cylinder 13c are arranged on the outer periphery of the intermediate shield cylinder 13b so as to protrude from the front and rear ends of the open magnetic circuit core in the tubular case by approximately the same length. The front and rear ends of the open magnetic circuit iron core are made to protrude from the front and rear ends of the main winding portion of the secondary coil by substantially the same length.

These three shield cylinders 13a, 13b, 1
Since 3c is arranged on the outer circumference of the cylindrical case as described above, the outer shield cylinder is fitted to the outer circumference of the cylindrical case,
An annular outer concave portion 14c whose outer peripheral surface is flush with the outer peripheral surface of the tubular case is formed. An intermediate shield cylinder is fitted to the outer peripheral surface of the annular outer concave portion, and the outer peripheral surface is the outer peripheral surface of the annular outer concave portion. Forming an annular intermediate recess 14b on the same surface as, and the inner shield tube is fitted to the outer periphery of the annular intermediate recess,
An annular inner recess 14a whose outer peripheral surface is flush with the outer peripheral surface of the annular intermediate recess 14b is provided.

Then, the three shield cylinders 13a, 13
For b and 13c, two molded pieces each formed of a silicon steel plate into a semi-cylindrical shape are used.
The two semi-cylindrical shaped pieces that form a
Is bonded to the outer circumference of the shield, and then the middle shield cylinder 13b
The two semi-cylindrical molded pieces that form the
The two semi-cylindrical molded pieces that form the outer shield cylinder 13c are adhered to the outer periphery of the annular middle recess 14b so as to face each other, and the two outer semi-cylindrical molded pieces are adhered to the outer shield of the annular outer recess 14c so as to face each other. Assemble the iron core 13. As a result, the outer peripheral surface of the outer shield cylinder 13c has the cylindrical case 6
It is flush with the outer peripheral surface of. The outer core 13 may be assembled before the open magnetic circuit core and the secondary coil are housed in the cylindrical case and the thermosetting resin is cast.

The cracks 13 'of the outer core for reducing unnecessary eddy currents which are likely to occur on the surface of the outer core are formed between the opposed semi-cylindrical molded pieces forming the inner, middle and outer shield cylinders. The positions of the cracks in the inner shield tube, the intermediate shield tube, and the outer shield tube are preferably arranged in the circumferential direction.

The second embodiment shown in FIG. 2 is a cylindrical case 6
Is divided into two parts at the front end of the annular outer recess 14c, the head part 6A having the plug engagement cylinder 7 and the high-voltage terminal 8, and the cylinder part 6B having the terminal support cylinder 9 attached to the rear end thereof. The portion and the front end portion of the tubular portion 6B can be fixed to each other in a series by fitting the male and female together and adhering.

As in the first embodiment of FIG. 1, an annular intermediate recess 14b is provided on the outer periphery of the annular outer recess 14c in the tubular portion 6A, and an annular inner recess 14a is provided on the outer periphery of the annular intermediate recess 14a. The outer core 13 is assembled to the tubular portion 6a before being fixed to the portion 6A. It has an inner shield tube 13
For the two a and the intermediate shield cylinder 13b, the two inner half shield cylinders 13a are formed by using two half-cylindrical molded pieces made of silicon steel plate in the same manner as in the first embodiment. The two semi-cylindrical molded pieces are bonded to the outer circumference of the annular inner recessed portion 14a so as to face each other, and then the two intermediate semi-cylindrical molded pieces are formed. Adhere facing to. The outer shield cylinder 13c is formed by rolling a silicon steel plate into a cylindrical shape, and is fitted from the annular outer recess 14c at the front end of the cylinder 6a to the rear end of the annular outer recess via the outer periphery of the intermediate shield cylinder 13b. The rear end portion of the head portion 6A and the front end portion of the tubular portion 6B are male and female fitted and bonded to each other to form a series of tubular cases 6. Since the front end of the cylindrical outer shield cylinder 13c abuts the rear end of the head portion 6A in a series, the outer shield cylinder need not be bonded to the annular outer recess or the outer periphery of the middle shield cylinder. If necessary, they may be bonded. In this way, in the second embodiment, the outer core can be assembled, and the outer peripheral surface of the outer shield cylinder 13c is flush with the outer peripheral surface of the tubular case 6. The cylindrical outer shield cylinder 13c tightly binds the intermediate and inner shield cylinders, to which the two semi-cylindrical molded pieces on the inner side are attached so as to be firmly fixed.

The cracks 13 'of the outer core for reducing unnecessary eddy currents that are likely to occur on the surface of the outer core are formed by the inner shield cylinder and between the opposed semi-cylindrical molded pieces forming the intermediate shield cylinder. It occurs between the opposite ends of the outer cylindrically rolled shield tube. The positions of the cracks in the inner shield tube, the intermediate shield tube, and the outer shield tube are preferably arranged in the circumferential direction.

As described above, the head portion 6A and the tubular portion 6B.
After assembling the outer cores by fixing them in series, the secondary coil wound around the closed bobbin core 1 around the closed magnetic circuit core 1 around which the primary coil is wound around the outer circumference of the secondary coil is wound inside the cylindrical case. Are arranged concentrically, and the terminal support cylinder 9 made of synthetic resin, in which the primary terminal 11 is attached to the connector portion 10 protruding from the outer circumference of the terminal support cylinder 9, is fitted and fixed to the inner circumference of the rear end of the tubular case, The high-voltage terminal 8 and the high-voltage side of the secondary coil, the low-voltage side of the secondary coil, and the primary coil are electrically connected to the primary terminal 11, and the thermosetting insulating resin is vacuumed from the inside of the rear tube into the tubular case. A closed magnetic circuit core 1 having a primary coil wound around the outer periphery of a thermosetting insulating resin layer 12 which has been cast and cured, and 2 wound around a bobbin 5.
Fix the next coil.

In each of the ignition coils of the first and second embodiments, a cylindrical boot 15 made of, for example, synthetic rubber, which is electrically insulative and elastic, is fitted to the plug engagement cylinder 7 and held in an extended shape. The cylindrical boot is inserted into the plug hole 16 of the engine, with the cylindrical boot as the head, and the cylindrical boot is elastically fitted to the outside of the insulator of the ignition plug 17 protruding from the bottom of the plug hole, so that the high voltage terminal 8 is coil spring 19. The head terminal 18 of the spark plug is pressed into contact with the spark plug and electrically connected, and a high voltage is applied to the spark plug.

In the illustrated embodiment, the outer iron core is composed of three shield cylinders of the outer side, the middle side and the inner side. However, it is essential that the outer core and the inner shield be provided with two shield tubes of different axial lengths. It suffices to provide the intermediate shield tube or not to provide it, and when providing the intermediate shield tube, it is also optional how much the intermediate shield tube is provided.

[0019]

The magnetic flux distribution in the outer core of the ignition coil is
As shown in FIG. 5, concentrated in the central portion of the exterior iron core in the axial direction,
The distribution of magnetic flux is extremely small near both ends in the axial direction of the outer core. In response to this, the present invention provides a magnetic shield effect of the armor core by increasing the laminated thickness by the inner and outer shield cylinders at the central portion in the axial direction of the armour core and by only the outer shield cylinders near both ends. It is possible to prevent the secondary voltage of the ignition coil and the reduction of the ignition energy without damaging the above. And the axial length of the inner shield tube is only 50 to 60% of the axial length of the main winding portion of the secondary coil, and this shield tube is of the main winding portion of the secondary coil. It is located at the center of the axial length and does not face the high voltage end of the secondary coil on the high voltage terminal side. The outer shield tube faces the high-voltage end portion, and is separated by at least the thickness of the inner shield tube. If the inner shield cylinder has the same axial length as the outer shield cylinder,
The insulation distance between the inner shield cylinder and the high voltage end of the secondary coil is 1.5 to 2.0 mm, but the axial length of the inner shield cylinder is the main winding portion of the secondary coil. By arranging it shorter than the above and arranging it in the center of the open magnetic circuit core, the insulation distance between the outer shield cylinder and the high-voltage end of the secondary coil is increased by the thickness of the inner shield cylinder. Sa is 0.35
Even if it is as small as ~ 0.5 mm, the insulation distance is increased by 20%, so that the dielectric strength is sufficiently increased, and it is possible to provide a highly reliable ignition coil that generates a high voltage required for engine ignition. .

According to the second aspect, even if the outer core is composed of a plurality of shield cylinders made of magnetic metal plates fitted inside and outside, the outer peripheral surface of the outer shield cylinder is flush with the outer peripheral surface of the cylindrical case. Therefore, the outer diameter of the ignition coil, that is, the outer diameter of the cylindrical case does not increase, and it can be accommodated within the restriction dimension to be mounted in the plug hole.

Further, according to the third aspect, the outer shield cylinder can be formed by rolling a silicon steel plate into a cylindrical shape, and the outer cylindrical shield cylinder forms two molded pieces in a semi-cylindrical shape. It is possible to tightly bind and tightly secure the shield cylinders inside that which are installed facing each other.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a first embodiment of an ignition coil of the present invention in use.

FIG. 2 is an enlarged sectional view taken along line BB of FIG.

FIG. 3 is a vertical cross-sectional view of a second embodiment of the ignition coil device of the present invention in use.

FIG. 4 is an enlarged sectional view taken along line BB of FIG.

FIG. 5 is an explanatory diagram of a magnetic flux distribution state of the outer core.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Primary coil 2 Secondary coil 3 Open magnetic circuit iron core 4 Insulation sheet wound on open magnetic circuit iron core 5 Secondary bobbin 6 Synthetic resin tubular case 6A Cylindrical case head section 6B Cylindrical case tubular section 7 Synthetic Plug case of resin cylindrical case 8 High-voltage terminal 9 Terminal support cylinder 10 Connector part of terminal support cylinder 11 Primary terminal 12 Thermosetting insulating resin layer 13 Exterior iron core 13a Shield cylinder inside the exterior iron core 13b Exterior iron core Intermediate shield tube 13c Shield tube outside the outer core 14a Annular inner recess provided in the tubular case 14b Annular intermediate recess provided in the tubular case 14c Annular outer recess provided in the tubular case 15 Cylindrical boot 16 Engine plug Hole 17 Spark plug 18 Spark plug head terminal 19 Coil spring

Claims (3)

[Claims] 1. An open magnetic circuit core at the center of an elongated cylindrical case made of synthetic resin having a high-voltage terminal at a closed front end.
A primary coil and a secondary coil are arranged concentrically outside of that,
The open magnetic circuit core, the primary coil and the secondary coil are fixed in a thermosetting insulating resin layer cast in a tubular case, and a cylindrical outer casing made of a magnetic metal plate is provided outside the tubular case. In an internal combustion engine ignition coil provided with an iron core, the outer iron core is constituted by a plurality of shield cylinders fitted inside and outside, and the axial length of the outer shield cylinder is longer than that of the open magnetic circuit core, and before and after that. The end portions of the above are projected beyond the front end and the rear end of the open magnetic circuit core in the tubular case, and the axial length of the inner shield tube is made shorter than the main winding part of the secondary coil, Ignition for an internal combustion engine, characterized in that the outer shield cylinder and the inner shield cylinder are arranged outside the cylindrical case so that the front and rear ends do not exceed the front and rear ends of the main winding part. coil. 2. The ignition coil for an internal combustion engine according to claim 1, wherein a shield cylinder outside the outer core is fitted to the outer periphery of the cylindrical case, and the outer peripheral surface of the outer shield cylinder is the cylindrical case. Provide an annular outer recess that is flush with the outer peripheral surface, and
On the outer circumference of this annular outer recess, an inner shield cylinder is fitted into the outer core, and an inner inner recess is provided so that the outer peripheral surface of the inner shield cylinder is flush with the outer peripheral surface of the outer outer recess. Ignition coil for internal combustion engine. 3. The ignition coil for an internal combustion engine according to claim 2, wherein an elongated cylindrical case made of synthetic resin is divided into two parts at a front end of the annular outer recessed portion to have a high voltage terminal, an annular outer recessed portion, and an annular outer recessed portion. The inner shield cylinder is divided into two parts, the inner concave part and the cylindrical part having the outer periphery. The inner shield cylinder made of two semi-cylindrical molded pieces made of silicon steel plate is attached to the outer periphery of the annular inner recess so as to face each other. Is fitted with an outer shield cylinder formed by rolling a silicon steel plate into a cylindrical shape from an annular outer recess, which is the front end of the cylinder, to the rear end of the recess, and the rear end of the head and the front end of the cylinder are connected in series. An ignition coil for an internal combustion engine, which is connected and fixed.