JP4237481B2 - 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 characterized by a method of electrically connecting a secondary coil and an ignition plug.
[0002]
[Prior art]
FIG. 4 is a longitudinal sectional view of the ignition coil 100 that directly supplies a high voltage to the spark plug, and FIG. 5 is an enlarged view of the plug connection portion of FIG. The ignition coil 100 includes a central iron core 170, a secondary coil 120 that is wound around the secondary bobbin 121 on the outer periphery of the central iron core 170, and a primary bobbin 111 that is disposed coaxially with the secondary coil 120. A primary coil 110 wound around, an exterior iron core 160 provided outside the primary coil 110, and a case 130 for housing them.
[0003]
At the upper position of the ignition coil 100, a power transistor 180 for turning on / off the current of the primary coil 110, a power supply terminal 131 to the power transistor 180, and the like are arranged. On the other hand, a high voltage tower 132 is formed at a lower position of the ignition coil, and the secondary high voltage terminal 122 is built in the high voltage tower 132. The secondary high voltage terminal 122 is electrically coupled to the spring 140 and transmits a high voltage generated in the secondary coil 120 to the spark plug 191.
[0004]
The operation of the above-described internal combustion engine ignition coil will be described. The current input from the power supply terminal 131 generates a magnetic flux through the primary coil 110 and generates a high voltage from the electromagnetically coupled secondary coil 120. The high voltage passes through the secondary high voltage terminal 122 attached to the high voltage tower 132 and is applied to the spark plug 191 through the spring 140. Here, the spark plug 191 has a built-in resistor for suppressing ignition noise that adversely affects electronic devices for controlling the engine, communication devices such as car radios and automobile telephones.
[0005]
[Problems to be solved by the invention]
By the way, when the spring 140 is mounted on the high-voltage terminal 122, the ignition coil having the above-described configuration fixes the spring 140 in the groove in the inner diameter portion of the high-voltage terminal 122 using the elasticity in the radial direction of the spring 140.
[0006]
However, the work of attaching the spring to the ignition coil is complicated and requires a long working time, and therefore, a smooth manufacturing process is pressed. Further, in an extreme case, the spring is dropped because the mounting method is bad, and as a result, it can be assembled into the engine without the spring, resulting in a malfunction or inability to start.
[0007]
In addition, when a user replaces the spark plug, there is a possibility that the electronic device malfunctions due to ignition noise when a spark plug without resistance is attached even though the spark plug with built-in resistance is designated. Furthermore, the contact between the spring and the head terminal of the spark plug is lowered, and the electrical connectivity between the output terminal of the ignition coil and the head terminal of the spark plug may be lowered.
[0008]
On the other hand, a configuration in which a spring is not used to connect the secondary coil and the spark plug is also known. For example, in the ignition coil disclosed in the following patent document, an epoxy resin is a main component, and a conductive filler is contained therein. The conductive adhesive is used.
[0009]
[Patent Document 1]
JP-A-7-260103
However, in this configuration, there is a problem that when a high voltage is applied to the ignition plug, ignition noise generated from the high voltage terminal of the secondary coil cannot be sufficiently suppressed by the conductive adhesive. As a result, the configuration using such a conductive adhesive may adversely affect electronic devices that control the operation of the engine and other communication devices such as car radios and automobile phones. In addition, there was a risk of engine ignition failure due to ignition noise.
[0011]
The present invention has been made in view of the above problems, and an object of the present invention is to eliminate engine troubles, reduce work processes, and effectively suppress ignition noise in an ignition coil for an internal combustion engine that supplies a high voltage to an ignition plug. .
[0012]
[Means for Solving the Problems]
The present invention for solving the above problems includes an iron core portion, a secondary coil portion in which a secondary winding is wound around a secondary bobbin, and a primary coil portion in which a primary winding is wound around a primary bobbin . A cylindrical internal combustion engine ignition coil that is configured to be housed in a case body and is directly connected to a spark plug when housed in a plug hole, and has a large-diameter portion on the proximal end side and a small-diameter on the distal end side The conductive elastomer formed in a substantially cylindrical shape as a whole is locked to the inner peripheral protrusion of the case body where the boundary between the large diameter portion and the small diameter portion can pass only the small diameter portion. The distal end cylindrical hole formed and positioned on the distal end side of the small diameter portion receives the head terminal of the spark plug, while the proximal end cylindrical hole formed on the proximal end side of the large diameter portion A bobbin cylindrical portion having a diameter larger than that of the proximal cylindrical hole that forms the forefront of the secondary bobbin Is accommodated, a lead wire to be connected to the spark plug, whereby along the outer peripheral surface of the bobbin cylindrical portion, by way of the electrically conductive elastomer, the electrical connection of said spark plug and said secondary coil unit It is characterized by having realized.
[0013]
In the present invention, it is possible to provide an ignition coil for an internal combustion engine that ensures reliability by using a conductive member other than a metal that does not use a spring for electrical connection between the secondary coil and the spark plug. . In addition, the positional relationship among the iron core portion, the primary coil portion, and the secondary coil portion may not be as in the embodiment.
[0014]
In addition, a conductive elastomer means what has flexibility among conductive resins, and is a concept except a conductive adhesive. As an elastomer, rubber can be illustrated as a typical example. A method for realizing the electrical conductivity is not particularly limited, but it is preferable to contain conductive fine particles in the resin material. Here, examples of the conductive fine particles include metals, carbon, and conductive polymers, but carbon, particularly carbon black is preferable. Appropriate conductivity (resistance value) can be realized depending on the type and amount of carbon black. As the resin, silicone is preferable, and conductive silicone rubber is most preferable.
[0015]
The conductive elastomer is preferably set to a resistance value of 1 to 10 KΩ, more preferably about 3 to 7 KΩ, and most preferably about 5 KΩ. In addition, a cylindrical hole for receiving the secondary coil portion and the terminal end portion of the spark plug is formed at both ends in the length direction of the conductive elastomer, and the cylindrical hole is the entire head terminal of the spark plug. It is formed to a depth that covers. In this case, electrical connection is ensured, and engine ignition failure can be prevented.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, based on the ignition coil CL for internal combustion engines which concerns on an Example, embodiment of this invention is described in detail. Here, FIG. 1 shows a longitudinal sectional view of the ignition coil CL for an internal combustion engine according to the embodiment, and FIG. 2A shows an enlarged view of the plug connecting portion of FIG. FIG. 1 shows a state in which the ignition coil CL is inserted into the plug hole 90 of the internal combustion engine. The illustrated ignition coil CL is in close contact with the ignition plug 91 and is electrically coupled thereto. .
[0017]
The illustrated ignition coil CL for an internal combustion engine is configured to be accommodated in a synthetic resin case 30. When the case 30 is roughly classified, a cylindrical case body 30a and an upper portion of the case body 30a are formed. It is divided into a case base end 30b that is provided continuously and a small-diameter high-pressure tower 30c that is provided continuously below the case body 30a.
[0018]
A substantially cylindrical conductive member 40 (FIG. 2A) is housed inside the high-pressure tower 30c, while a protector 50 is fitted on the outer periphery of the high-pressure tower 30c. Here, the protector 50 prevents the high voltage of the ignition coil CL from leaking into the metal portion of the plug hole 90 and is formed in a substantially cylindrical shape that covers the protruding end portion of the ignition brag 91 together with the high-voltage tower 30. Has been. The conductive member 40 will be further described later.
[0019]
The case base end portion 30b accommodates a power supply unit 80 including a power transistor PTr and a power supply terminal 80a to the power transistor PTr. As shown in FIG. 2B, the power transistor PTr is turned on / off based on a signal from the power supply terminal 80a to drive the primary coil unit 10. Therefore, a high voltage pulse voltage is generated from the secondary coil unit 20 electromagnetically coupled to the primary coil unit 10. The pulse voltage generated from the secondary coil unit 20 is supplied to the spark plug 91 via the high voltage diode D.
[0020]
As shown in FIG. 1, in the case main body portion 30 a located at the center in the axial direction, there are a central iron core portion 70, a secondary coil portion 20 provided outside the central iron core portion 70, and a secondary coil portion. The primary coil part 10 provided on the outside of 20 and the exterior iron core 60 fitted on the outside of the primary coil part 10 are arranged coaxially, respectively, and an insulating material injected into each gap (for example, The whole is integrated by curing the thermosetting epoxy resin).
[0021]
Specifically, the central iron core portion 70 includes a central iron core 70a made of a magnetic steel plate such as a silicon steel plate, a buffer tape 70b made of a polyester film covering the outer periphery of the central iron core 70a, and upper and lower ends of the central iron core 70a. And a permanent magnet 70c that suppresses magnetic saturation. Although not shown, the permanent magnet 70c is covered with a silicone cushioning material formed in a cap shape.
[0022]
The secondary coil part 20 is comprised by the secondary bobbin 20a located in the outer side of the center iron core part 70, and the secondary winding 20b wound by this. Moreover, the primary coil part 10 is comprised by the primary bobbin 10a located in the outer side of the secondary coil part 20, and the primary winding 10b wound by this.
[0023]
FIG. 3A is a perspective view showing the tip protrusion 23 of the secondary bobbin 20a of the secondary coil portion, and FIG. 3B is a plan view showing the lowermost surface of the tip protrusion 23. As shown in FIG. FIG. 3C illustrates the lead terminals (D ₁ and D ₂ ) of the high-voltage diode D, and FIG. 3D is a partial cross-sectional view illustrating the tip protrusion 23.
[0024]
As shown in FIG. 3A, a secondary winding 20 b is wound around a secondary bobbin 20 a provided with a bobbin ridge 21. More specifically, the tip protruding portion 23 of the secondary bobbin 20a is configured by connecting a first cylindrical portion 24 and a second cylindrical portion 25 that are gradually reduced in diameter from the bobbin main body. As shown in FIGS. 2B and 3C, the cylindrical portions 24 and 25 have a high voltage diode D connected to the high voltage side of the secondary winding 20b. The parts 24 and 25 are accommodated in the axial direction.
[0025]
As shown in FIG. 3A, the secondary winding 20 b led out to the outer periphery of the first cylindrical portion 24 extends upward from the first cylindrical portion 24 and reaches the power feeding portion 80. It is connected to the. The secondary winding 20b connected to the connection wire 26 is a low-voltage side winding of the secondary coil portion 20, while the high-voltage side winding is a high-voltage diode included in the cylindrical portions 24 and 25. It is connected to the cathode side lead wire D ₁ of the D.
[0026]
As shown in FIG. 3A, the first cylindrical portion 24 and the second cylindrical portion 25 are formed with one notch groove 27 in the axial direction, whereby the second cylindrical portion 25 is radially inward. Allows for shrinkage. Of course, the inner peripheral surface of the second cylindrical portion 25 does not press the high voltage diode D even in the maximum contracted state.
[0027]
The second cylindrical portion 25, more particularly, is composed of a main body portion 25a and the distal tapered portion 25b (FIG. 3 (d)), the anode-side lead wire D ₂ of the high-voltage diode D is derived from the tip tapered portion 25b ing. The derived lead wire D ₂ is bent and folded along the outer peripheral surface of the second cylindrical portion 25. Here, the folded lead wire D ₂ has the terminal end of the lead wire D ₂ from the conductive member 40 even when the second cylindrical portion 25 is completely accommodated in the conductive member 40 (FIG. 2A). The length is set so as to protrude outside.
[0028]
As shown in FIG. 3B, a total of four protrusions 28 for guiding the lead wire 8b are provided on the end face 25c of the second cylindrical portion 25 at positions orthogonal to the notch groove 27, and the lead The folding direction of the line 8b is positioned. That is, the lead wire D ₂ is correctly folded back in the direction perpendicular to the notch groove 27, guided by the pair of protrusions 28 and 28.
[0029]
The high pressure tower 30c will be described with reference to FIGS. 1 and 2A. The high pressure tower 30c includes a first cylindrical portion 31 on the proximal end side and a second cylindrical portion having a smaller diameter than the first cylindrical portion 31. 32. The second cylindrical portion 32 is formed with an inner peripheral ridge 33 and an outer peripheral ridge 34.
[0030]
As shown in FIG. 2A, the inner peripheral protrusion 33 is a protrusion protruding inward in the radial direction from the inner peripheral surface of the first cylindrical portion 31 of the high-pressure tower, and receives and locks the conductive member 40. It is a part to do. On the other hand, the outer peripheral ridge 34 is a ridge that protrudes radially outward from the outer peripheral surface of the second cylindrical portion 32 of the high-pressure tower, and is a portion that engages with the protector 50 and ensures the mounting of the protector 50. is there.
[0031]
The conductive member 40 is configured in a substantially cylindrical shape as a whole by a large-diameter portion 41 on the proximal end side and a small-diameter portion 42 on the distal end side. The outer diameter of the large-diameter portion 41 is formed to be slightly larger than the inner peripheral diameter of the cylindrical first portion 31, while the outer diameter of the small-diameter portion 42 is substantially the same as the opening diameter of the inner peripheral protrusion 33 (slightly Small).
[0032]
Therefore, when the conductive member 40 is press-fitted downward from the upper part of the case 30, the boundary portion between the small diameter portion 42 and the large diameter portion 43 of the conductive member 40 is locked and positioned by the inner peripheral protrusion 33. Become. In addition, since the outer diameter of the large diameter part 41 is formed a little larger than the inner peripheral diameter of the cylindrical first part 31, the press-fitted large diameter part 41 is positioned in a slightly contracted state.
[0033]
As shown in FIG. 2A, on the proximal end side of the large diameter portion 41, a slightly small diameter cylindrical hole 41a having a depth and shape corresponding to the second cylindrical portion 25 of the secondary bobbin 20a is formed. ing. The second cylindrical portion 25 of the secondary coil unit 20, since the inserted push the the cylindrical bore 41a, in a state where the cylindrical hole 41a has accepted the second cylindrical portion 25, the lead wire D ₂ of the high-voltage diode D The conductive member 40 is reliably contacted.
[0034]
Similarly, a cylindrical hole 42 a having a depth and a shape corresponding to the upper terminal portion of the spark plug 91 and having a smaller diameter than the upper terminal portion of the spark plug 91 is formed on the distal end side of the small diameter portion 42. Therefore, in the state where the ignition coil CL is mounted, the upper terminal of the spark plug 91 pushes the cylindrical hole 42a to be press-fitted, and the cylindrical hole 42a covers the entire terminal portion.
[0035]
The material of the conductive member 41 having the above shape is not particularly limited as long as it is an elastomer having conductivity, but in the case of the embodiment, conductive fine particles (metal, carbon, conductive) are formed on a silicon resin. Functional polymer). Preferably, carbon black is added to silicone rubber to provide conductivity, and is molded into a required shape by compression molding or injection molding.
[0036]
The resistance value of the conductive member 40 varies depending on the type and amount of the conductive fine particles contained, but should preferably be set to about 1 to 10 KΩ, more preferably about 3 to 7 KΩ, and most preferably about 5 KΩ. Is set. When carbon black is contained in the silicone rubber, the resistance value can be changed depending on the type of carbon black and the amount added, but in the case of the example, the resistance value is set to about 5 kΩ.
[0037]
In general, electronic devices that control the engine and communication devices such as car radios and car telephones are affected by ignition noise and induce noise, but by setting the conductive member 40 to a resistance value of about 5 kΩ. High voltage can be supplied to the spark plug without leaking ignition noise to the outside. Therefore, by interposing this conductive member, the secondary coil 20 and the terminal portion of the spark plug 91 can be kept in contact with each other without using a spring, and electrical connectivity can be reliably ensured. it can.
[0038]
【The invention's effect】
According to the ignition coil for an internal combustion engine of the present invention, it is not necessary to use a high voltage terminal and a spring as in the prior art, and the ignition plug and the secondary coil can be reliably electrically connected and ignition noise can be prevented. Ignition failure can be prevented. In addition, the process of attaching the spring can be eliminated and the cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of an internal combustion engine ignition coil according to an embodiment.
2 is an enlarged view (a) of a plug connecting portion in FIG. 1 and a circuit configuration diagram of an ignition coil. FIG.
FIG. 3 is a view for explaining contact between a tip portion of a secondary coil portion and a conductive member.
FIG. 4 is a longitudinal sectional view of a conventional ignition coil for an internal combustion engine.
FIG. 5 is an enlarged view of the plug connection portion of FIG. 4;
[Explanation of symbols]
CL Internal combustion engine ignition coil 10 Primary coil part 20 Secondary coil part 40 Conductive member 30 Case 70 Iron core part

Claims (4)

An iron core portion, a secondary coil portion in which a secondary winding is wound around a secondary bobbin, and a primary coil portion in which a primary winding is wound around a primary bobbin are accommodated in a case body and are configured as plug holes. Is a cylindrical ignition coil for an internal combustion engine , the tip of which is directly connected to the spark plug,
The conductive elastomer formed in a substantially cylindrical shape as a whole with a large-diameter portion on the base end side and a small-diameter portion on the distal end side allows the boundary portion between the large-diameter portion and the small-diameter portion to pass only the small-diameter portion. Locked to the inner peripheral ridge of the case body and positioned ,
While the tip cylindrical hole formed on the tip side of the small diameter portion receives the head terminal of the spark plug ,
The base end cylindrical hole formed on the base end side of the large diameter portion accommodates a bobbin cylindrical portion having a diameter larger than that of the base end cylindrical hole, which forms the forefront of the secondary bobbin.
By connecting the lead wire to be connected to the spark plug along the outer peripheral surface of the bobbin cylindrical portion, the electrical connection between the secondary coil portion and the spark plug is realized via the conductive elastomer. An ignition coil for an internal combustion engine. The bobbin cylindrical portion accommodates a diode connected to the secondary winding,
The ignition coil for an internal combustion engine according to claim 1 , wherein a lead wire of the diode is led out to an outer peripheral surface of the bobbin cylindrical portion . 3. The internal combustion engine for an internal combustion engine according to claim 2, wherein the lead wire of the diode is led out along the outer peripheral surface after being led out to a tip end of the bobbin cylindrical portion, and a terminal end thereof is exposed from the base end cylindrical hole . Ignition coil. The conductive elastomer is set to a resistance value of 1 to 10 KΩ, and the large diameter portion of the conductive elastomer is disposed in a slightly contracted state by the inner peripheral surface of the case body. 2. An ignition coil for an internal combustion engine according to 1.

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