JP2003232272A - Ignition coil for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ignition coil provided with an elastic member with a high degree of design freedom, facilitating the adoption of structure permitting positive engagement and holding of the ignition coil to a spark plug. <P>SOLUTION: This ignition coil for an internal combustion engine is provided with a primary coil; a secondary coil disposed almost concentrically with the primary coil; a coil case 20 for enclosing these coils; a tower case 30 provided below in line with the coil case; and the elastic member having a fixed part 312 fixed to the tower case, and an engaging part 314 which can be elastically engaged with a plug terminal, and applying high voltage boosted by the secondary coil, to the plug terminal. The elastic member has the fixed part and the engaging part in axially different positions, and the ignition coil is held to the spark plug through the elastic member. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, a high voltage is supplied to a spark plug from a mechanical distributor through a high tension cord. At present, a type in which a high voltage is directly supplied to an ignition plug from an ignition coil (ignition coil) independently provided for each cylinder of an internal combustion engine (engine) is becoming mainstream. In the case of such an independent ignition coil, the upper end of each ignition coil has heretofore often been fixed by screwing it to a cylinder head cover or the like. However, recently, there has been proposed a method in which the screwing is eliminated and the ignition coil is directly fixed to the ignition plug itself. Such an ignition coil is disclosed, for example, in Utility Model Registration No. 3068339.

The method of fixing the ignition coil to the spark plug disclosed in that publication is a conventional method of fixing the plug cap. More specifically, first, a locking hole is provided in the peripheral side surface of the electrode 23 housed in the protective cover 22 (tower case). A substantially cylindrical contact spring 24 (elastic member) is mounted on the outer peripheral side of the electrode 23 while the projection is locked in the locking hole. At this time, the protrusion of the contact spring 24 projects further inward beyond the locking hole of the electrode 23 and can be engaged with the annular groove of the plug terminal. In this way, the ignition coil can be fixedly engaged with the ignition plug.

[0004]

However, in the case of this ignition coil, there are a fixed position where the contact spring 24 is fixed to the electrode 23 and an engaging position where the contact spring 24 engages with the plug terminal. , Are on substantially the same horizontal plane where the locking holes and the protrusions are present (on the same plane in the radial direction with the axial line as the normal). Here, since the ignition coil generally has a very small dimensional tolerance in the radial direction as compared with the axial direction, the degree of freedom in designing each member is significantly limited in the radial direction. As a result, a structure (for example, a locking protrusion is provided) that can reliably engage and hold a heavy ignition coil with respect to the ignition plug while providing the above-described positional relationship between the fixed position and the engagement position. In reality, it is extremely difficult to adopt a structure in which the size is increased or the number is increased.

The ignition coil for an internal combustion engine of the present invention has been made in view of such circumstances. That is, the heavy ignition coil is securely engaged with the spark plug,
An object of the present invention is to provide an ignition coil for an internal combustion engine, which can be held and has a large degree of design freedom.

[0006]

Therefore, the present inventor has diligently studied to solve this problem, and as a result of repeated trial and error,
The present invention has been completed by the idea of disposing the fixing portion and the engaging portion of the elastic member so as to be axially displaced from each other. That is, the ignition coil for an internal combustion engine of the present invention has a primary coil in which a primary winding is wound around a primary spool, and a secondary winding in which a secondary spool is wound substantially concentrically with the primary coil. A secondary coil, a coil case for accommodating the primary coil and the secondary coil, a tower case connected under the coil case and capable of accommodating at least a plug terminal of an ignition plug in the center, and a tower case disposed in the tower case. A high voltage boosted by the secondary coil is applied to the plug terminal, which has a fixing portion that is provided and fixed to the tower case and an engaging portion that can elastically engage the plug terminal. An ignition coil for an internal combustion engine, comprising: an elastic member, wherein the elastic member is
It is characterized in that the fixing portion and the engaging portion are provided at different positions in the axial direction, and are held with respect to the ignition plug by interposing the elastic member.

In the ignition coil device of the present invention, the fixing portion of the elastic member with respect to the tower case and the engaging portion that elastically engages the plug terminal are arranged at different positions in the axial direction where the dimension tolerance is relatively large. I set it up. Thereby, the elastic member,
The degree of freedom in design has been increased, and it has become possible to easily adopt a structure that is securely fixed in the tower case and can be firmly engaged with the plug terminal.

As such an elastic member, for example, a substantially cylindrical leaf spring formed by subjecting a plate material made of spring steel or the like to a predetermined shape by sheet metal working or the like can be used. The leaf spring in this case is
It does not need to be a continuous annular shape, and may be a discontinuous one that is partially interrupted. The fixed part at that time is, for example,
It may be a notch extending in the axial direction that engages with a locking piece that projects from the inner wall of the tower case, or an annular collar that is fitted into an annular recess formed on the inner peripheral side of the tower case. . In any case, it is preferable that the fixing portion has a structure that is firmly fixed to the tower case so as not to wobble. The fixing portion of the elastic member may be directly fixed to the locking piece or the like integrally formed on the tower case, or may be a separate member (metal fitting or the like) provided between the elastic member and the tower case. It may be indirectly fixed to the tower case via the.

Specifically, the engaging portion is, for example,
It may be a plurality of protrusions protruding toward the inner peripheral side. The elastic member, and thus the ignition coil, is held and fixed to the ignition plug by firmly engaging the protrusion with the annular groove (with the annular step) provided on the outer peripheral surface of the plug terminal. This engaging portion is not limited to the case of elastically engaging with the plug terminal, but when elastically engaging with the plug insulator connected below the plug terminal, the elastic member (that is, It is preferable because the ignition coil) is fixed and held. That is, it is preferable that the engaging portion of the elastic member includes a first engaging portion that engages with the plug terminal and a second engaging portion that engages with the plug insulator of the ignition plug.

The second engaging portion that engages with the plug insulator may have a holding function for the spark plug, but at least a part of the first engaging portion needs to apply a high voltage to the plug terminal. Therefore, it is necessary to have conductivity. Here, when the elastic member is made of a metal such as spring steel, there is no particular problem because it usually has electrical conductivity as it is. However, the elastic member is not limited to metal, and may be made of resin or ceramic as long as it has elasticity. Therefore, when the elastic member is made of an insulating material or the like, a conductive film is added to a necessary portion of the elastic member,
It is preferable to impart electric conductivity to the elastic member by molding the elastic member using raw material powder mixed with conductive powder.
Conversely, the engaging portion that does not require conductivity may be an insulating material or the like.

By the way, in order to apply a high voltage from the elastic member to the plug terminal, it is necessary to supply a high voltage from the secondary coil to the elastic member. Therefore, the elastic member
For example, it has a contact part that is connected to the secondary winding and contacts a secondary side terminal to which a high voltage is applied, or contacts a high voltage terminal that is electrically connected to the secondary side terminal. It is preferable to have a contact portion that does. The contact portion may be an elastic contact piece, for example, by bending an end portion of a substantially cylindrical leaf spring from the outer peripheral side to the inner peripheral side. As a result, it is possible to obtain a contact portion that has a simple structure and that can absorb dimensional tolerances and the like and ensure stable conductivity. Incidentally, the vertical relationship in the present specification, the ignition coil side is the upper,
This is for convenience, with the spark plug side facing down. Therefore, the vertical relationship referred to in the present invention has nothing to do with the actual mounting position of the internal combustion engine ignition coil.

Further, the disposition relationship between the primary coil and the secondary coil may be inside or outside of the primary coil as long as they are substantially concentric. Further, the coil case and the tower case referred to in the present invention may be separate bodies, or the coil case and the tower case may be integrally molded. In any case, finally, both need to form the case (housing) of the ignition coil. Therefore, it is to be noted that the coil case and the tower case referred to in the present specification are merely convenient names depending on the arrangement position.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be specifically described with reference to embodiments. (First Embodiment) FIG. 1 shows an ignition coil 100 for an internal combustion engine (hereinafter, referred to as ignition coil 100) according to an embodiment of the present invention. The ignition coil 100 is a so-called stick type ignition coil, and is installed for each cylinder in a plug hole of a cylinder head of an engine (not shown). The ignition coil 100 is not of a type fixed to the upper end of the cylinder head by screwing,
It is a type that is fixedly held to the spark plug by a leaf spring 31 described later. The ignition coil 100 is roughly divided into a control unit 1, a coil unit 2 and a high voltage tower unit 3.

The control unit 1 comprises a terminal 12 insert-molded in the connector 13 and an igniter 11 connected to the terminal 12. And the ECU
The ignition signal received from (not shown) is transmitted to the igniter 11 via the terminal 12. Based on the ignition signal, the igniter 11 switches a primary current supplied to a primary winding 23, which will be described later, to cause the spark plug P to generate intermittent discharge.

The coil portion 2 includes a coil case 20 forming an outer shell, a primary coil 21 wound around a primary spool 21 which is sequentially arranged inside the coil case 20 from the outside, and a secondary spool 22. The secondary coil 24 is mainly composed of a secondary coil wound around the secondary winding 24, a central core 26 arranged in the center, and an outer peripheral core 25 fitted outside the coil case 20. An open magnetic circuit is formed by these, and the battery voltage (about 12 V) supplied to the primary coil
Is a high voltage (about 30 kV) that can be discharged by the spark plug P
Is boosted in the secondary coil.

The high-voltage tower portion 3 is a tower case 30 which is a part (lower part) of the resin-molded coil case 20.
A rubber plug cap 36, which is attached to the lower end side of the tower case 30 and closely holds the spark plug P disposed in the center of the tower case 30, and a secondary winding which is press-fitted and fixed to the lower end side of the secondary spool 22. Secondary side terminal 2 connected to one end of wire 24
7 and a leaf spring 31 (elastic member) interposed between the secondary side terminal 27 and the plug terminal PT. After assembling the coil portion 2 and the high voltage tower portion 3, the resin insulating material 5 made of epoxy resin is vacuum filled from above the control portion 1 (in the figure). The resin insulating material 5 passes between the primary spool 21 and the secondary spool 22 and reaches each communicating space.
The secondary coil and the primary coil are insulated from each other and each member is fixedly held.

Next, the structure of the high-pressure tower section 3, which is a characteristic part of this embodiment, will be described in detail with reference to FIG. 1 and FIG. 2 which is an enlarged view of the leaf spring 31. 2A is a plan view of the leaf spring 31, FIG. 2B is a front view thereof, and FIG. 2C is a bottom view thereof. Tower case 3
0 has a double cylindrical shape, and the inner cylindrical portion 3 is provided inside thereof.
01 is formed. The outer peripheral side of the secondary side terminal 27 is press-fitted into the upper inner peripheral side of the inner cylindrical portion 301. Then, these press-fitted surfaces serve as sealing surfaces to prevent the resin insulating material 5 filling the internal space of the tower case 30 from leaking to the outside.

Locking pieces 302 project from three uniform locations on the inner peripheral wall of the inner tubular portion 301 and extend in the axial direction. The locking pieces 302 engage with the notches 312 (fixed portions) that are evenly arranged at three positions of the leaf spring 31, and the leaf spring 31 is fixed to the tower case 30. Further, apart from the locking piece 302, a holding piece 303 having a smaller amount of projection than the locking piece 302 projects from three even locations on the inner peripheral wall. The body 313 of the leaf spring 31 is held by the holding piece 303. In this way, the leaf spring 31 is positioned at a predetermined position in the inner tubular portion 301 and is stably fixed.

From three even locations on the top of the leaf spring 31,
A contact piece 317 (contact portion) is bent and formed from the outer peripheral side toward the inner peripheral side. This contact piece 317 is the secondary terminal 2
The lower end surface of 7 elastically abuts. Thus, the inner tubular portion 30
Between the leaf spring 31 attached to No. 1 and the secondary side terminal 27 that is press-fitted and fixed to the lower end side of the secondary spool 22, dimensional tolerance of each part is absorbed and electrical conduction is reliably achieved.
A hemispherical projection 314 (engagement portion) protrudes inward from the center of the lower portion of each body portion 313 of the leaf spring 31. The protrusion 314 engages with the annular groove PT1 of the plug terminal PT. Here, since the body portion 313 provided with the protrusion 314 is held by the holding piece 303 of the tower case 30, the engagement between the annular groove PT1 and the protrusion 314 becomes more stable. Then, the ignition coil 100 is securely held by the spark plug P.

As described above, in this embodiment, the notch 312 that is the fixing portion of the elastic member and the protrusion 3 that is the engaging portion thereof.
Since 14 and 14 are provided at different positions in the axial direction where dimensional tolerance is large, the degree of freedom in designing both can be increased. As a result, the spark plug 100 is securely fixed to the tower case 30, and the protrusions 314 larger than three positions, which have been difficult in the related art, are provided so that the spark plug 100 can operate.
It became possible to hold it firmly against T.

(Second Embodiment) Next, the secondary spool 2
2, secondary side terminal 27, tower case 30 and leaf spring 3
FIG. 3 shows a high voltage tower section in which the shape of No. 1 is changed and a high voltage terminal 32 is added. In addition, the same code | symbol is attached | subjected to the member of the same name as 1st embodiment. Leaf spring 3 in this case
1 has a cylindrical shape without the above-mentioned notch 312. As described above, the hemispherical projections 314 (engagement portions) equally project from the three places on the lower portion of the leaf spring 31, and are reliably engaged with the annular groove PT1 of the plug terminal PT.

An annular collar 31 is provided on the upper end of the leaf spring 31.
5 (fixed portion, contact portion) are formed. This ring collar 3
15 is fitted into an annular recess 305 formed in the upper end opening of the inner tubular portion 301. Further, the convex high-voltage terminal 32 is pressed into the annular recess 305 from above the annular collar 315. Then, the annular flange 315 is sandwiched between the lower surface of the high voltage terminal 32 and the stepped surface of the annular recess 305. In this way, the leaf spring 31 is positioned and firmly fixed to the inner cylindrical portion 301, and the leaf spring 31 electrically contacts the high-voltage terminal 32. Note that, as in the first embodiment, the resin insulating material 5 is sealed by the press-fitting surfaces of the outer peripheral surface of the high voltage terminal 32 and the inner peripheral surface of the annular recess 305.

The columnar protrusion 325 protruding from the center of the upper portion of the high-voltage terminal 32 has a recess 221 formed at the lower end side of the secondary spool 22 and a secondary side press-fitted and fixed to the lower end side of the secondary spool 22. It is inserted into the insertion hole 271 of the terminal 27. At this time, the end portion of the insertion hole 271 is folded back toward the inner peripheral side to form a barb 271a. Then, the barb 271a is press-fitted and locked to the outer peripheral surface of the columnar protrusion 325. By engaging the barbs 271a and the columnar protrusions 325, the electrical connection between the secondary side terminal 27 and the high voltage terminal 32 is made more reliable. The conductivity between the secondary side terminal 27 and the leaf spring 31 is ensured via the high voltage terminal 32.

(Third Embodiment) In this embodiment, as shown in FIG. 4, the engaging portion of the leaf spring 31 of the second embodiment is changed, and the other portions than the engaging portion are the same as those of the second embodiment. It is the same. Therefore, here, the engagement portion will be mainly described. In addition, in FIG. 4, members having the same names as those in the second embodiment are denoted by the same reference numerals.

In the leaf spring 31 of this embodiment, in addition to the above-mentioned projection 314 (first engaging portion) protruding inward from the body portion 313, a part of the body portion 313 extends downward. On the stopper, a hemispherical protrusion 3 protruding inwardly like the protrusion 314.
16 (second engaging portion). The protrusion 316 engages with the annular groove PG1 of the plug insulator PG that supports the plug terminal PT. In this embodiment, the protrusion 314 and the protrusion 3
16 and 16 are arranged alternately and evenly in two places.
You may arrange | position at four places. According to this embodiment, it is possible to apply a large engaging force to the engaging portion by utilizing a large degree of design freedom in the axial direction. Then, the leaf spring 31 and thus the ignition coil 100 can be more securely held and fixed to the ignition plug P.

(Fourth Embodiment) In the present embodiment, as shown in FIG. 5, while using the leaf spring 31 of the first embodiment, the shape of the secondary side terminal 27 is changed, and a plate spring is provided between them. Spring 31
Is a new addition of the high-voltage terminal 32 that contacts.
Therefore, the secondary terminal 27 and the high voltage terminal 32 will be mainly described here. Note that, in FIG. 5, members having the same names as those in the above-described embodiments are denoted by the same reference numerals. The upper end opening of the inner cylinder portion 301 of the tower case 30 is a small-diameter portion 306 whose outer circumference is slightly reduced in diameter. The crown-shaped high-voltage terminal 32 is press-fitted into the small-diameter portion 306 from above in a crowned manner. The press-fitting surface between the inner peripheral surface of the high voltage terminal 32 and the outer peripheral surface of the small diameter portion 306 seals the resin insulating material 5.
It is similar to the above-described embodiment.

A columnar protrusion 325 projects from the center of the upper portion of the high voltage terminal 32. The columnar protrusion 325 is
Similar to the second embodiment, the recess 221 is formed in the lower end side of the secondary spool 22 and the insertion hole 271 of the secondary terminal 27 press-fitted and fixed to the lower end side of the secondary spool 22. At this time, the end portion of the insertion hole 271 is folded back toward the inner peripheral side to form a barb 271a. And
The barb 271a is press-fitted and locked to the outer peripheral surface of the columnar protrusion 325. By engaging the barbs 271a and the columnar protrusions 325, the electrical connection between the secondary side terminal 27 and the high voltage terminal 32 is made more reliable. The conductivity between the secondary side terminal 27 and the leaf spring 31 is also secured via the high voltage terminal 32. As described above, various embodiments of the present invention can be considered, and as long as the fixing portion and the engaging portion of the elastic member are arranged at different axial positions, the present invention is not limited to the above embodiment. It goes without saying that this is not the case.

[0028]

According to the ignition coil for an internal combustion engine of the present invention, the fixing portion and the engaging portion of the elastic member that play an important role in holding and fixing the ignition coil to the ignition plug are arranged in the axial direction. Arranged in different positions. For this reason, the degree of freedom in designing the elastic member is increased, and it has become possible to easily adopt a structure in which engagement and retention with respect to the ignition plug can be reliably performed as compared with the conventional case.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an entire ignition coil according to an embodiment of the present invention.

2A and 2B are views showing a leaf spring according to the first embodiment, FIG. 2A is a plan view thereof, FIG. 2B is a front view thereof, and FIG. 2C is a bottom view thereof. It is a figure.

FIG. 3 is a cross-sectional view showing a high pressure tower section of an ignition coil according to a second embodiment.

FIG. 4 is a cross-sectional view showing a high pressure tower section of an ignition coil according to a third embodiment.

FIG. 5 is a cross-sectional view showing a high pressure tower section of an ignition coil according to a fourth embodiment.

[Explanation of symbols]

1 control unit 2 coil part 3 High voltage tower section 20 coil case 21 Primary spool 22 Secondary spool 23 Primary winding 24 secondary winding 27 Secondary side terminal 30 tower case 31 leaf spring 312 Notches (fixed part) 314 Locking piece (engaging part) 317 Contact piece (contact part) 100 Ignition coil for internal combustion engine

Claims (6)

[Claims] 1. A primary coil having a primary winding wound on a primary spool; and a secondary coil having a secondary winding wound on a secondary spool arranged substantially concentrically on the primary coil, A coil case for accommodating the primary coil and the secondary coil, a tower case connected under the coil case and capable of accommodating at least a plug terminal of an ignition plug in the center, and a tower case disposed in the tower case and arranged in the tower case. An internal combustion engine having a fixing portion fixed to the plug terminal and an engaging portion capable of elastically engaging the plug terminal and applying a high voltage boosted by the secondary coil to the plug terminal. An ignition coil for an engine, wherein the elastic member has the fixing portion and the engaging portion at different axial positions, and is held with respect to the ignition plug by way of the elastic member. Characteristic internal combustion engine Use the ignition coil. 2. The elastic member further has a contact portion which is connected to the secondary winding and contacts a secondary side terminal to which a high voltage is applied, or a high voltage terminal which can conduct with the secondary side terminal. An ignition coil for an internal combustion engine according to claim 1. 3. The elastic member is a substantially cylindrical leaf spring, and the fixing portion is a notch extending in the axial direction that engages with a locking piece protruding from an inner wall of the tower case. Item 1
An ignition coil for an internal combustion engine as described. 4. The elastic member is a substantially cylindrical leaf spring, and the fixing portion is an annular collar that is fitted into an annular recess formed on the inner peripheral side of the tower case. Ignition coil for internal combustion engine. 5. The ignition coil for an internal combustion engine according to claim 1, wherein the elastic member is a substantially cylindrical leaf spring, and the engaging portion is a plurality of protrusions protruding inward. 6. The engaging portion of the elastic member comprises a first engaging portion that engages with the plug terminal and a second engaging portion that engages with a plug insulator of the ignition plug. An ignition coil for an internal combustion engine according to.