JP4926370B2 - Ignition coil for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ignition coil for an internal combustion engine of an independent ignition type that is attached to each ignition plug of an engine and is directly connected to each ignition plug.
[0002]
[Prior art]
As a conventional internal combustion engine ignition device, a center core, a primary coil, and a secondary coil are housed inside an elongated cylindrical coil case, and these coils are wound around respective bobbins and concentrically around the center core. Arranged above. In this coil, since a high voltage is generated, the insulation between the respective members is ensured by filling and curing epoxy which is an insulating resin. Since such different materials have different linear expansion coefficients, thermal stress is generated under severe temperature conditions, and micro-cracks may be generated in the bobbin and epoxy, resulting in a decrease in insulation. In view of this, for example, as described in Patent Document 1 below, there is a case where stress relaxation is achieved by further disposing an elastic body between the inner side of the secondary bobbin and the center core.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-26267 (page 8, FIG. 1)
[0004]
[Problems to be solved by the invention]
By the way, in the said prior art, only the stress relaxation with respect to thermal shock property is examined, and it does not describe regarding impact resistance. In the actual environment, various impacts are applied to each coil from the outside, and different materials are used for each member, so there are places where stress concentration occurs in various forms, and cracks originating there May occur.
[0005]
The present invention has been made in view of the above-described circumstances, and it is an object to provide a highly reliable ignition coil for an internal combustion engine that not only has excellent thermal shock resistance but also includes external shock resistance. To do.
[0006]
[Means for Solving the Problems]
The ignition coil for an internal combustion engine according to the first aspect of the present invention, which has been made to solve the above problems, is an independent ignition type internal combustion engine that is inserted into a plug hole of the internal combustion engine and is directly connected to each ignition plug. The ignition coil includes a shock absorbing cover that covers a part or the whole of the upper surface of the connector case provided above the coil portion, and the shock absorbing cover is on a portion surrounded by the upper end portion of the connector case. a base wall which is located, together with the provided on the periphery of the base wall, possess a side wall located so as to face the periphery of the side surface of the connector case upper portion, have a clearance between the cover and the connector case It is characterized in that was. According to the present invention having such a feature, since the cover serves to absorb the impact, the impact from the upper surface of the connector case is remarkably reduced as compared with the current case as shown in FIG. It becomes like this. By providing a cover and covering part or all of the upper surface of the connector case, the occurrence of cracks starting from locations where stress concentration is likely to occur is reduced, and a highly reliable ignition coil is obtained.
Also, the clearance plays an effective role in shock absorption. Specifically, as shown in FIG. 2, the stress applied to the coil portion is reduced by providing the clearance.
[0008]
An ignition coil for an internal combustion engine according to a second aspect of the present invention is the ignition coil for an internal combustion engine according to the first aspect , wherein the clearance is at least 0.5 mm. According to the present invention having such characteristics, as shown in FIG. 2, the stress applied to the coil portion is reduced by 48% by providing a clearance of 0.5 mm. The stress is reduced by 41% when the clearance is 0.8 mm, and by 33% when the clearance is 1.0 mm.
[0009]
Ignition coil of the present invention according to claim 3, in the internal combustion engine ignition coil according to claim 1 or 2, with molding the cover with a thermoplastic resin material, the cap having a flexible It is characterized by being formed into a shape. According to the present invention having such characteristics, the impact is absorbed by utilizing the deformation of the cap-shaped cover made of resin. That is, since the cover has flexibility and is not a rigid body, the cover is instantly deformed when subjected to an impact. Thereby, an impact is not immediately transmitted to the connector case side.
[0010]
An ignition coil for an internal combustion engine according to a fourth aspect of the present invention is the ignition coil for an internal combustion engine according to the third aspect , wherein a notch is formed in the cover. According to the present invention having such characteristics, instantaneous deformation upon impact is further accelerated. Thereby, the effect concerning shock absorption can be improved.
[0011]
The internal combustion engine ignition coil according to claim 5 is the internal combustion engine ignition coil according to any one of claims 1 to 4 , wherein a centering protrusion for the connector case is formed inside the cover. It is characterized by. According to the present invention having such characteristics, the cover is prevented from being biased, and the effect of absorbing the shock can be obtained at any portion. Further, if the cover is prevented from being biased, the appearance is not affected.
[0012]
An ignition coil for an internal combustion engine according to a sixth aspect of the present invention is the ignition coil for an internal combustion engine according to the fifth aspect , wherein the projection for centering is formed in a semicircular arc shape and a tapered shape inward. It is characterized by that. According to the present invention having such a feature, the mountability of the cover is not harmed, and centering is performed near the arcuate apex as the cover and the connector case come closer so that the cover is prevented from being biased. Become. Since the centering protrusion is in point contact with the connector case, there is no problem in terms of stress even with light press-fitting.
[0013]
An ignition coil for an internal combustion engine according to a seventh aspect of the present invention is characterized in that in the ignition coil for an internal combustion engine according to the fifth aspect , the centering protrusions are formed at least at three locations. According to the present invention having such a feature, the backlash of the cover can be reliably suppressed. In addition, positioning is performed with high accuracy.
[0014]
An ignition coil for an internal combustion engine according to an eighth aspect of the present invention is the ignition coil for an internal combustion engine according to any one of the first to seventh aspects, wherein the convex portion for locking is provided on one of the cover and the connector case. In addition, a locking concave portion corresponding to the convex portion is formed on one of the other. According to the present invention having such a feature, the engagement structure is formed by the uneven portion, that is, the cover and the connector case are locked by the so-called hook structure, and when the impact is received, the uneven portion is responded to the impact. Will be separated. Among the structures for attaching the cover, it becomes one of the structures in which the impact is not immediately transmitted to the connector case side.
[0015]
An internal combustion engine ignition coil according to a ninth aspect of the present invention is the internal combustion engine ignition coil according to any one of the first to eighth aspects, wherein a shock absorbing rubber damper is provided inside or outside the cover. It is said. According to the present invention having such a feature, the rubber material also plays a role of absorbing an impact together with the cover. Thereby, the impact from the upper surface of the connector case is further alleviated.
[0016]
An ignition coil for an internal combustion engine according to a tenth aspect of the present invention is the ignition coil for an internal combustion engine according to the ninth aspect , wherein the thickness of the shock absorbing rubber damper is at least 0.5 mm. According to the present invention having such characteristics, it is effective particularly when a rubber material is provided inside the cover.
[0017]
An ignition coil for an internal combustion engine according to an eleventh aspect of the present invention is the ignition coil for an internal combustion engine according to any one of the first to tenth aspects, wherein the inside of the cover is a room-temperature curing type silicon-based shock absorber. The cover is partially fixed by attaching an elastic adhesive for use. According to the present invention having such a feature, the number of steps for attaching the cover is reduced.
[0018]
An ignition coil for an internal combustion engine according to a twelfth aspect of the present invention is the ignition coil for an internal combustion engine according to any one of the first to eleventh aspects, wherein the coil portion is disposed between the inner side of the secondary bobbin and the center core, and It is characterized in that a flexible epoxy resin as a shock absorbing elastic member is filled from 1/4 to the total length of the secondary coil. According to the present invention having such a feature, the impact applied to the entire coil portion is mitigated.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of an ignition coil for an internal combustion engine according to the present invention.
[0021]
In FIG. 1, an independent ignition type internal combustion engine ignition coil (ignition coil) that is inserted into a plug hole of an internal combustion engine and directly connected to each spark plug is used as an external part that is inserted into the plug hole. An elongated cylindrical case (exterior case) 6 having a diameter of φ18 mm to φ27 mm is provided. Inside the outer case 6, the center coil 5, the secondary coil 3 wound around the secondary bobbin 4, and the primary coil 1 wound around the primary bobbin 2 are concentric from the center (inner side) to the outer side. Is arranged. These components are inserted into the outer case 6 and then filled with a thermosetting insulating resin (epoxy resin) 14 to ensure insulation.
[0022]
Several layers of side cores 7 that form a magnetic path with the center core 5 are mounted on the outside of the outer case 6. The side core 7 is formed by rolling a thin silicon steel plate or a directional silicon steel plate having a thickness of about 0.2 to 0.5 mm into a tubular shape, and is configured by stacking 1 to 4 sheets. The side core 7 is provided with at least one cut for preventing one turn of magnetic flux on the circumference of the side core 7.
[0023]
The center core 5 is formed using a silicon steel plate or a directional silicon steel plate having a thickness of 0.2 to 0.7 mm. The center core 5 approaches a cylindrical shape so that its cross-sectional area increases. A large number of set silicon steel plates are press-laminated. Although not particularly shown here, a state in which a core having a high magnetic flux density is used by providing a magnet on one end surface or both end surfaces in the axial direction of the center core 5 and applying a magnetic flux opposite to the magnetic flux generated by the coil. In some cases, magnetic energy may be increased (higher output).
[0024]
A stress-absorbing elastic member 8 (for example, silicone rubber) is provided at the end of the center core 5 (which may be the upper end or the lower end). An elastic member 15 is provided around the center core 5. These are provided in order to relieve the thermal stress (stress caused by the difference in linear expansion coefficient) generated between the secondary bobbin 4 and the center core 5.
[0025]
As the elastic member 15, heat-resistant silicone rubber, flexible epoxy resin (in this example, soft epoxy resin) or the like is used. A soft epoxy resin is an epoxy resin having a glass transition point below normal temperature (20 ° C.) and an elastic soft property (estramer) above the glass transition point, for example, a mixture of an epoxy resin and a modified aliphatic polyamine. . Since the soft epoxy resin has an insulating function between the center core 5 and the secondary coil 3, the soft epoxy resin is injected after being evacuated (for example, 4 Torr or less) so as not to generate voids, and then cured.
[0026]
The primary bobbin 2 is formed of a thermoplastic synthetic resin such as polybutylene terephthalate (PBT), polyphenylene oxide (modified PPO), or polyphenylene sulfide (PPS) with an inorganic filler of 20% by weight or more in order to ensure mechanical strength. The primary coil 1 wound around the primary bobbin 2 is composed of enameled wires having a wire diameter of about 0.3 to 1.0 mm, several tens to hundreds of times per layer, and a total of 100 to 300 over several layers. It is a winding that is laminated and wound about times.
[0027]
The secondary bobbin 4 is also formed of, for example, a thermoplastic synthetic resin such as modified polyphenylene oxide (modified PPO) or polyphenylene sulfide (PPS) in which an inorganic substance is mixed by 20% by weight or more, more preferably 30% by weight or more. The secondary bobbin 4 has a bottomed cylindrical shape, and the above-described stress absorbing elastic member 8 and the center core 5 are received by the bottom of the secondary bobbin. The stress absorbing elastic member 8 and the center core 5 are housed in the secondary bobbin 4.
[0028]
The secondary bobbin 4 is interposed between the center core 5 and the secondary coil 3 and serves to insulate the high voltage generated in the secondary coil 3. And in order to insulate the high voltage which generate | occur | produced in the secondary coil 3, the thickness of the secondary bobbin 4 is 0.5-1.5 mm. Further, in order to prevent electric field concentration and stress concentration between the secondary coil 3 and the center core 5, the center core 5 is injected with an elastic member 15 on the inner peripheral side of the secondary bobbin 4 and cured and fixed. It has become.
[0029]
The secondary coil 3 is divided and wound in a multi-layered structure between a plurality of secondary bobbins 4 using a enameled wire having a wire diameter of about 0.03 to 0.06 mm for a total of about 10,000 to 30,000 times.
[0030]
The epoxy resin 14 inserts the secondary coil 3 wound around the secondary bobbin 4 and the primary coil 1 wound around the primary bobbin 2 into the outer case 6, and further supplies the igniter unit 10 to the connector case 17. After the terminal of the igniter unit 10 is fixed to the connector terminal by welding, the igniter unit 10 is injected in a vacuum state. Then, the epoxy resin 14 is cured by heating to ensure insulation and mechanical strength.
[0031]
The outer case 6 is formed of a thermoplastic synthetic resin such as polyphenylene sulfide (PPS), and is formed so that the coil portion can be accommodated and fixed and the epoxy resin 14 can be cast.
[0032]
Although not indicated in particular, FIG. 1 shows a pre-ignition prevention high voltage diode, ita spring, high voltage terminal, spark plug connection spring, spark plug connection plug seal (silicone rubber), plug hole seal rubber. A noise prevention capacitor is illustrated.
[0033]
Reference numeral 18 in FIG. 1 indicates a cover which is the gist of the present invention. The cover 18 is formed of a thermoplastic synthetic resin. The cover 18 is formed in a cap shape that covers the whole or part of the upper surface of the connector case 17. In this embodiment, it is formed so as to cover a portion (corresponding to the above part) surrounded by the connector case upper end portion 17a. That is, the cover 18 is coupled to the base wall located on the portion surrounded by the connector case upper end portion 17a and the periphery of the base wall, and is positioned so as to face the periphery of the side surface of the connector case upper end portion 17a. And an annular side wall. The cover 18 has flexibility.
[0034]
A clearance C is provided in the connector case upper end 17a and the cover inner surface 18a. When an impact is applied to the cover 18, the cover 18 is deformed using the clearance C so as to absorb the impact. As shown in FIG. 2, when the clearance C is 0.5 mm or more, the stress applied to the coil portion is reduced to 1/2 or less (specifically, 48% at 0.5 mm and 41 at 0.8 mm). %, Reduced by 33% at 1.0 mm). This has been confirmed by experiments.
[0035]
As shown in FIG. 3, the cover 18 includes a convex portion 18 b provided on a part of the annular side wall of the cover 18 and a concave portion 17 b provided on a part of the side surface of the connector case upper end portion 17 a of the connector case 17. It has a locking structure that stops, in other words, a hook structure E. Thereby, the impact force (see arrow) at the time of impact application is also absorbed by the lateral deformation of the cover 18 (see broken line), and the impact absorption effect is enhanced. Although not particularly illustrated, the same effect can be obtained even if a concave portion is provided in the cover 18 and a convex portion is provided on the connector case 17 side. Further, it is assumed that a sufficient fixing strength of the cover 18 can be obtained by providing two or more hook structures E.
[0036]
The cover 18 is provided with a centering projection 9 as shown in FIG. 4 so that the cover 18 is not attached to the connector case 17 in a biased manner. The centering projection 9 is provided on the cover inner surface 18a (specifically, the inner surface of the annular side wall). Since the position of the cover 18 is determined if there are three centering projections 9, three or more positions are required.
[0037]
As shown in FIG. 5, the centering protrusion 9 has a semicircular arc shape and a tapered shape toward the cover inner surface 18 a (toward the base wall). With such a shape, centering is performed in the vicinity of the arcuate apex 9a as the cover inner surface 18a and the connector case upper end portion 17a approach each other without impairing the mountability of the cover 18. Since the centering protrusion 9 is in point contact with the connector case upper end portion 17a, it is assumed that there is no problem in terms of stress even if light press-fitting is performed. Therefore, the centering projection 9 can suppress the backlash of the cover 18 and can be positioned with high accuracy.
[0038]
Next, the concept of the present invention will be described with reference to FIG.
[0039]
For example, when an impact such as a drop is applied to the upper surface of the connector case 17, a maximum stress is generated on the opposite side H to which the impact is applied, and the magnitude is applied to the entire center of gravity position G and the impact. It is represented by the product of the distance L to the location K and the impact force F. In order to relieve this stress, it is effective to relieve the entire impact force with the impact absorber, shorten the distance L, or provide a relaxation structure inside. Therefore, the cap-type cover 18 which provides a clearance C between the cover inner surface 18a of the thermoplastic resin and the connector case upper end 17a as shown in FIG.
[0040]
Next, another embodiment will be described. First, it demonstrates using FIG.
[0041]
In FIG. 7, as a method for suppressing the impact application force, the thermoplastic resin cover 18 is provided with notches 18c (specifically, a plurality of notches 18c are provided on the annular side wall). Therefore, a spring force can be given by the notch 18c, and the entire impact application force can be reduced.
[0042]
In FIG. 8, an elastic body such as a rubber material, that is, a rubber damper (A) 11 is disposed on the upper surface of a cover 18 made of thermoplastic resin. In FIG. 9, the rubber damper (B) 12 is also disposed on the lower surface of the thermoplastic resin cover 18. In any case, the impact can be more effectively absorbed by the rubber dampers (A) 11 and (B) 12. In the case of FIG. 9, since the rubber damper (B) 12 is covered with the cover 18, the appearance is good. The thickness of the rubber damper (B) 12 is preferably 0.5 mm or more.
[0043]
In addition, instead of the rubber damper (B) 12 shown in FIG. 9, an adhesive 13 having elasticity as shown in FIG. 10 (for example, a silicon-based adhesive) may be used. By using such an elastic adhesive 13, the cover 18 can be bonded and fixed and the impact can be absorbed by the elastic body. Furthermore, by making this elastic adhesive 13 a room temperature curing type, it is possible to bond without using a high temperature curing process, and it becomes possible to increase productivity without impairing workability.
[0044]
In FIG. 11, the elastic member 23 is cast from the low voltage side to the upper side of the secondary coil 3 so as not to crack inside the moment where the moment is applied (from 1/4 of the total length of the secondary coil 3 to the upper surface side). Has been cast). Since the upper surface of the secondary coil 3 has a low potential, the withstand voltage is not severe, and the outer case 6 has rigidity, so that it can sufficiently withstand vibration from the engine side even if the elastic member 23 is contained inside. Can do. In this embodiment, an elastic member 15 covering the periphery of the center core 5 is used as the elastic member 23. In addition, since the elastic member 15 is vacuum-cast, there is no fear that voids are formed therein.
[0045]
FIG. 12 shows an example of a result obtained by analyzing each example by the finite element method as an effect of the present invention. The maximum principal stress acting on the coil portion can be reduced to about 55 to 30% of the current state.
[0046]
In addition, it goes without saying that the present invention can be variously modified without departing from the spirit of the present invention.
[0047]
【Effect of the invention】
As described above, there is an effect that it is possible to provide a highly reliable ignition coil for an internal combustion engine that is excellent in thermal shock resistance and excellent in external impact resistance.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of an ignition coil for an internal combustion engine according to the present invention.
FIG. 2 is a graph for explaining an effect.
FIG. 3 is a cross-sectional view of a main part.
FIG. 4 is a bottom view of the cover.
FIG. 5 is an explanatory diagram of a centering protrusion.
FIG. 6 is an explanatory diagram of the concept of the present invention.
FIG. 7 is a perspective view showing another example of a cover.
FIG. 8 is a cross-sectional view showing another embodiment (second example) of the ignition coil for an internal combustion engine according to the present invention.
FIG. 9 is a cross-sectional view showing another embodiment (third example) of the ignition coil for an internal combustion engine according to the present invention.
FIG. 10 is a sectional view showing another embodiment (fourth example) of the ignition coil for an internal combustion engine according to the present invention.
FIG. 11 is a sectional view showing another embodiment (fifth example) of an ignition coil for an internal combustion engine according to the present invention.
FIG. 12 is a graph for explaining the effect of the finite element method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Primary coil 2 ... Primary bobbin 3 ... Secondary coil 4 ... Secondary bobbin 5 ... Center core 6 ... Outer case 7 ... Side core 8 ... Stress absorbing elastic member 9 ... Centering protrusion 9a ... Arc-shaped vertex 10 ... Ignator unit 11 ... Rubber damper A
12 ... Rubber damper B
13 ... Elastic adhesive 14 ... Insulating resin (epoxy resin)
15 ... Elastic member 17 ... Connector case 17a ... Connector case upper end 17b ... Recess (connector case recess)
18 ... Cover 18a ... Cover inner surface 18b ... Convex part (cover convex part)
18c ... Notch 23 ... Elastic member C ... Clearance E ... Hook structure F ... Reaction force G by impact G ... Center of gravity H ... Stress generating part K ... Impact application point

Claims (12)

In an independent ignition type internal combustion engine ignition coil that is inserted into a plug hole of an internal combustion engine and directly connected to each ignition plug,
A shock absorbing cover that covers a part or the whole of the upper surface of the connector case provided above the coil portion,
The shock absorbing cover is provided on a base wall located on a portion surrounded by the upper end portion of the connector case, and on a peripheral edge of the base wall, and is positioned so as to face the periphery of the side surface of the upper end portion of the connector case. have a and a side wall which,
An ignition coil for an internal combustion engine , wherein a clearance is provided between the cover and the connector case . The ignition coil for an internal combustion engine according to claim 1,
An ignition coil for an internal combustion engine, wherein the clearance is at least 0.5 mm . The ignition coil for an internal combustion engine according to claim 1 or 2,
An ignition coil for an internal combustion engine, wherein the cover is molded using a thermoplastic resin material and is formed into a flexible cap shape . The ignition coil for an internal combustion engine according to claim 3 ,
An ignition coil for an internal combustion engine, wherein a notch is formed in the cover . In claims 1 to an ignition coil for an internal combustion engine in accordance with claim 4,
An ignition coil for an internal combustion engine , wherein a projection for centering with respect to the connector case is formed inside the cover. The ignition coil for an internal combustion engine according to claim 5 ,
The ignition coil for an internal combustion engine, characterized in that the centering protrusion is formed in a semicircular arc shape and a tapered shape inward . The ignition coil for an internal combustion engine according to claim 5 ,
An ignition coil for an internal combustion engine, wherein the centering protrusions are formed in at least three locations . The ignition coil for an internal combustion engine according to any one of claims 1 to 7 ,
An ignition for an internal combustion engine, wherein a locking projection is formed on one of the cover and the connector case, and a locking recess corresponding to the projection is formed on the other. coil. The ignition coil for an internal combustion engine according to any one of claims 1 to 8,
An internal combustion engine ignition coil, characterized in that an impact absorbing rubber damper is provided inside or outside the cover. The ignition coil for an internal combustion engine according to claim 9 ,
An ignition coil for an internal combustion engine, wherein the thickness of the shock absorbing rubber damper is at least 0.5 mm . The ignition coil for an internal combustion engine according to any one of claims 1 to 10,
An ignition coil for an internal combustion engine , wherein a normal temperature curing type silicon-based elastic shock absorbing elastic adhesive is attached to a part of the inside of the cover to partially fix the cover . The ignition coil for an internal combustion engine according to any one of claims 1 to 11,
An internal combustion engine characterized in that a flexible epoxy resin as a shock absorbing elastic member is filled between the inner side of the secondary bobbin and the center core in the coil portion and from 1/4 to the upper surface side of the total length of the secondary coil. Ignition coil for engine.

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