Patent Grant
11189422
This application claims priority on Patent Application No. 2019-001637 filed in JAPAN on Jan. 9, 2019. The entire contents of this Japanese Patent Application are hereby incorporated by reference.
The present invention relates to ignition coils of internal combustion engines.
An ignition coil includes a coil assembly that generates a high voltage, therein. The high voltage from the coil assembly is applied to a spark plug provided in a combustion chamber of an internal combustion engine. By the voltage application, a spark due to discharge from the spark plug occurs to ignite fuel in the internal combustion engine.
The discharge at the spark plug can cause electric noise (conduction noise/radiation noise). When the noise reaches a surrounding circuit of a control device or the like, an erroneous operation of the circuit may occur. In order to prevent such an erroneous operation due to the noise, an ignition coil having a resistor mounted therein is in practical use. In this ignition coil, an output terminal of a coil assembly is connected to one end of the resistor, and the other end of the resistor is connected to the spark plug. A high voltage from the coil assembly is applied to the spark plug via the resistor. The resistor reduces electric noise due to discharge at the spark plug. An ignition coil having a resistor therein is disclosed in Japanese Laid-Open Patent Publication No. 2017-98462.
As described above, one end of the resistor is connected to the output end of the coil assembly, and the other end thereof is connected to the spark plug. The output voltage from the coil assembly is high, and therefore, when this voltage is applied, discharge can occur from one end to the other end of the resistor. When this discharge occurs, the resistor cannot serve the function of reducing electric noise. In the ignition coil described in Japanese Laid-Open Patent Publication No. 2017-98462, the resistor is held in a resistor storage portion by fixation means composed of a plurality of projections and holding means formed by an O ring or the like attached to the fixation means, whereby insulation resin is prevented from leaking out from the resistor storage portion. Thus, the periphery of the outer wall surface of the resistor is covered by the insulation resin, and discharge at the resistor is prevented. However, this structure is complicated, and components for the holding means are also needed. This hampers improvement in efficiency of assembling of the ignition coil, and can also cause increase in assembly cost.
An object of the present invention is to provide an ignition coil that prevents discharge at a resistor with a simple structure while suppressing increase of components.
An ignition coil for internal combustion engine according to the present invention includes: a coil assembly including a primary coil, a secondary coil, and a terminal that outputs a voltage from the secondary coil; a relay electrically connected to the terminal; a resistor having a bar shape and electrically connected to the relay; a case that stores the coil assembly, the relay, and the resistor; and a filler filling a gap inside the case. The case includes a body, an output portion having a cylindrical shape and protruding from the body, and a holding portion which has an annular shape and which protrudes inward from an inner circumferential surface of the output portion and extends in a circumferential direction of the inner circumferential surface, the holding portion being formed integrally with the output portion. A part of the resistor is inserted into the holding portion, and thus a first internal area located on a body side with respect to the holding portion and shut off from outside is formed in an internal area of the output portion. The filler fills the first internal area so as to cover a surface of the resistor.
In the ignition coil according to the present invention, the annular holding portion is formed on the inner circumferential surface of the output portion of the case. A part of the resistor is inserted into the holding portion, and thus the first internal area located on the body side with respect to the holding portion and shut off from outside is formed in the internal area of the output portion. The filler fills the first internal area so as to cover the surface of the resistor. That is, the part, of the resistor, that is on the body side with respect to the holding portion is located in the first internal area shut off from outside, and the surface of the part is covered by the filler. The part, of the resistor, that is on the side opposite to the body with respect to the holding portion is located outside the first internal area. This structure effectively prevents discharge from one end to the other end of the resistor. In this ignition coil, the resistor is inserted into the annular holding portion, whereby the resistor is attached to the output portion and the first internal area to which the filler is to be supplied is formed. This structure is simple. Further, the holding portion is formed as a part of the case and integrally with the output portion, and therefore components are not increased. In this ignition coil, discharge at the resistor is prevented with a simple structure while increase of components is suppressed.
Preferably, a second internal area located on a side opposite to the body with respect to the holding portion is further formed in the internal area of the output portion.
Preferably, an outer diameter of the first internal area is larger than an outer diameter of the second internal area.
Preferably, the resistor penetrates through the holding portion, and thus one end of the resistor is located in the second internal area.
Preferably, an outer diameter of the first internal area gradually decreases from the body side toward a holding portion side.
Preferably, a side surface, of the holding portion, that is on the body side is sloped in an inward direction from the body side toward a side opposite thereto.
Preferably, the relay is in contact with the resistor, in the first internal area.
Preferably, the relay has a connection portion that is in contact with a side surface of the resistor.
Preferably, the connection portion has a ring shape, and the resistor is inserted through an inner side of the connection portion. The connection portion may have a cap shape, and one end of the resistor is capped with the connection portion.
The following will describe in detail the present invention based on preferred embodiments with reference to the accompanying drawing.
The case 4 forms an exterior of the ignition coil 2. The case 4 is hollow, and stores therein the coil assembly 6, the igniter 8, the relay 10, the resistor 12, and the filler 14. The case 4 is made from resin. Examples of preferable materials for the case 4 include polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), and polyethylene terephthalate (PET). The case 4 includes a body 20, a connector portion 22, a flange portion 24, an output portion 26, and a holding portion 28.
The body 20 has a box shape and stores the coil assembly 6 and the igniter 8 therein. The connector portion 22 protrudes frontward from the body 20. The connector portion 22 has a cylindrical shape, and a connector terminal 30 is provided on the inner side thereof. When the ignition coil 2 is mounted to a vehicle, the connector terminal 30 is connected to a control device (ECU) of the vehicle. The flange portion 24 protrudes rearward from the body 20. The flange portion 24 has a hole 32 penetrating in the up-down direction. Although not shown, a bolt is inserted into the hole 32 and a hole provided in the internal combustion engine, whereby the ignition coil 2 is fixed to the internal combustion engine.
The output portion 26 protrudes downward from the body 20. In
The holding portion 28 is located on the inner circumferential surface 36 of the output portion 26. The holding portion 28 protrudes inward from the inner circumferential surface 36 of the output portion 26. The holding portion 28 has an annular shape extending in the circumferential direction of the inner circumferential surface 36 of the output portion 26. The holding portion 28 has an inner circumferential surface 38, a first side surface 40 which is a side surface on the body 20 side (upper side), and a second side surface 42 which is a side surface on the side (lower side) opposite to the body 20. As shown in
As shown in
As shown in
The relay 10 extends from the inside of the body 20 of the case 4 to the inside of the output portion 26. The relay 10 is electrically connected to the output terminal 50 of the coil assembly 6, and is also electrically connected to the resistor 12. The output terminal 50 of the coil assembly 6 and the resistor 12 are electrically connected to each other via the relay 10. The relay 10 is made of a metal having excellent conductivity.
The resistor 12 is stored in the output portion 26 of the case 4. The resistor 12 has a bar shape. In the present embodiment, the resistor 12 has a columnar shape. The resistor 12 has an upper portion 12a, a middle portion 12b, and a lower portion 12c. The outer diameters of the upper portion 12a and the lower portion 12c are slightly larger than the outer diameter of the middle portion 12b. As shown in
In the present embodiment, the output terminal 50 of the coil assembly 6 and the arm 52 are formed as separate components. The output terminal 50 may be formed integrally with the arm 52. The output terminal 50 of the coil assembly 6, the arm 52, and the connection portion 54 may be formed integrally with one another.
As shown in
As shown in
As shown in
The filler 14 fills gaps formed inside the case 4 when the coil assembly 6, the igniter 8, the relay 10, and the resistor 12 are stored in the case 4. Typically, the filler 14 is made from thermosetting resin. As shown in
Operation of the ignition coil 2 is as follows. A control signal from a control device of a vehicle is sent to the igniter 8 via the connector terminal 30. In accordance with the control signal, the igniter 8 conducts a current of the primary coil 46 or interrupts the current. Due to change in the current of the primary coil 46, a high voltage is generated on the secondary coil 48. The high voltage generated on the secondary coil 48 is applied to the resistor 12 via the relay 10 from the output terminal 50 of the coil assembly 6, and then applied to the spark plug via the spring 18 from the resistor 12. A spark occurs from the spark plug, to ignite fuel.
The following will describe advantageous effects of the present invention.
In the ignition coil 2 according to the present invention, a part of the resistor 12 is inserted into the holding portion 28, and thus the first internal area 34a shut off from outside is formed in the internal area 34 of the output portion 26. The filler 14 fills the first internal area 34a so as to cover the surface of the resistor 12. That is, a part, of the resistor 12, that is on the body 20 side with respect to the holding portion 28 is located in the first internal area 34a shut off from outside, and the entire surface of the part is covered by the filler 14. The contact part between the resistor 12 and the relay 10 is also covered by the filler 14. On the other hand, the contact part between the resistor 12 and the spring 18 is located outside the first internal area 34a. The contact part between the resistor 12 and the relay 10 and the contact part between the resistor 12 and the spring 18 are isolated from each other by the filler 14 and the holding portion 28. This structure effectively prevents discharge between one end and the other end of the resistor 12. In this ignition coil 2, discharge at the resistor 12 is prevented. This resistor 12 effectively contributes to reduction in electric noise due to discharge at the spark plug. In this ignition coil 2, electric noise is effectively suppressed.
In this ignition coil 2, the bar-shaped resistor 12 is inserted into the annular-shaped holding portion 28, whereby the resistor 12 is attached to the output portion 26 and the first internal area 34a to which the filler 14 is to be supplied is formed. This structure is simple. This contributes to achievement of high assembly efficiency and reduction in assembly cost.
As described above, the holding portion 28 is formed integrally with the output portion 26. In this ignition coil 2, no special components are needed for fixing the resistor 12 and forming the first internal area 34a shut off from outside. In this ignition coil 2, components are not increased. In this ignition coil 2, assembly cost can be further reduced.
There is a method of suppressing discharge at the resistor 12 by increasing the size of the resistor 12. However, increasing the size of the resistor 12 can hamper size reduction and weight reduction of the ignition coil. In this ignition coil 2, it is not necessary to increase the size of the resistor 12, in order to suppress discharge at the resistor 12. This contributes to size reduction and weight reduction of the ignition coil 2. Further, since this ignition coil 2 has a simple structure, it is easy to reduce the size and the weight thereof. In this ignition coil 2, size reduction and weight reduction are achieved while discharge at the resistor 12 is prevented.
As described above, in the present embodiment, the outer diameter of the first internal area 34a of the output portion 26 gradually decreases from the body 20 side toward the holding portion 28 side. In manufacturing of the ignition coil 2, the filler 14 is supplied from the body 20 side to the first internal area 34a. Since the outer diameter of the first internal area 34a gradually decreases from the body 20 side toward the holding portion 28 side, it is possible to spread the filler 14 to every part of the first internal area 34a. The entire surface of a part, of the resistor 12, that is located in the first internal area 34a is covered by the filler 14 without gaps. This effectively prevents discharge at the resistor 12. In this ignition coil 2, electric noise due to discharge at the spark plug is effectively suppressed. Further, since the outer diameter of the first internal area 34a is large on the body 20 side, a certain degree of freedom in the shape of the relay 10 can be obtained.
As described above, in the present embodiment, the first side surface 40 of the holding portion 28 is sloped in the inward direction from the body 20 side toward the side opposite thereto. This enables the filler 14 to be supplied to the deepest part of the corner formed by a side surface of the resistor 12 and the first side surface 40, without gaps. The entire surface of a part, of the resistor 12, that is located in the first internal area 34a is covered by the filler 14 without gaps. This effectively prevents discharge at the resistor 12. In this ignition coil 2, electric noise due to discharge at the spark plug is effectively suppressed.
As described above, in the present embodiment, the inner diameter of the first internal area 34a is larger than the inner diameter of the second internal area 34b. In the first internal area 34a, the resistor 12 and the relay 10 are located. Since the inner diameter of the first internal area 34a is larger, the filler 14 readily flows into the first internal area 34a even though the resistor 12 and the relay 10 are located therein. The filler 14 can fill the inside of the first internal area 34a without gaps. This effectively prevents discharge at the resistor 12. In this ignition coil 2, electric noise due to discharge at the spark plug is effectively suppressed. Further, since the inner diameter of the first internal area 34a is larger, a certain degree of freedom in the shape of the relay 10 can be obtained.
As described above, in the present embodiment, in the internal area 34, the second internal area 34b is provided on the side opposite to the body 20 with respect to the holding portion 28. The end surface 56 of the lower portion 12c of the resistor 12 is located in the second internal area 34b. Thus, the contact part between the resistor 12 and the spring 18 can be located in the second internal area 34b. This effectively protects the contact part between the resistor 12 and the spring 18. In addition, since the lower portion 12c of the resistor 12 extends to the second internal area 34b, the resistor 12 and the spring 18 can be easily and reliably brought into contact with each other.
As described above, in the present embodiment, the contact part between the resistor 12 and the relay 10 is located in the first internal area 34a. Thus, the contact part between the resistor 12 and the relay 10 can be reliably covered by the filler 14 without gaps. This effectively prevents discharge at the resistor 12. In this ignition coil 2, electric noise due to discharge at the spark plug is effectively suppressed.
As described above, in the present embodiment, the connection portion 54 of the relay 10 has a ring shape, and the resistor 12 is inserted through the connection portion 54. The connection portion 54 is in contact with the side surface of the resistor 12. Thus, the relay 10 can be reliably fixed to the resistor 12, and the contact area between the connection portion 54 and the resistor 12 can be increased. Thus, the contact resistance between the relay 10 and the resistor 12 can be stably reduced. This effectively prevents discharge at the resistor 12. In this ignition coil 2, electric noise due to discharge at the spark plug is effectively suppressed.
The relay 66 is stored in the case 62. The relay 66 extends from the inside of a body 72 of the case 62 to the inside of the output portion 74. The relay 66 is electrically connected to the output terminal of the coil assembly 64, and is also electrically connected to the resistor 68. The output terminal of the coil assembly 64 and the resistor 68 are electrically connected to each other via the relay 66. The relay 66 is made from a metal having excellent conductivity.
The resistor 68 is stored in the output portion 74 of the case 62. The resistor 68 has a bar shape. In the present embodiment, the resistor 68 has a columnar shape.
In the present embodiment, the output terminal of the coil assembly, the arm 76 and the connection portion 78 are formed as separate components. The arm 76 may be formed integrally with the connection portion 78. The output terminal of the coil assembly may be formed integrally with the arm 76, and the connection portion 78 may be attached thereto. The output terminal of the coil assembly, the arm 76, and the connection portion 78 may be formed integrally with one another.
As described above, in the present embodiment, the connection portion 78 of the relay 66 has a cap shape, and the resistor 68 is capped with the connection portion 78. The connection portion 78 is in contact with the side surface 80 and the upper end surface 82 of the resistor 68. Thus, the relay 66 can be reliably fixed to the resistor 68, and further, the contact area between the connection portion 78 and the resistor 68 can be increased. This enables the contact resistance between the relay 66 and the resistor 68 to be stably reduced. This effectively prevents discharge at the resistor 68. In this ignition coil 60, electric noise due to discharge at the spark plug is effectively suppressed.
As described above, according to the present invention, it is possible to obtain an ignition coil that prevents discharge at a resistor with a simple structure while suppressing increase of components. Thus, advantages of the present invention are clear.
The ignition coil described above is applicable to various types of internal combustion engines.
The above descriptions are merely illustrative examples, and various modifications can be made without departing from the principles of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP2019-001637 | Jan 2019 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 20180342347 | Ide | Nov 2018 | A1 |
| Number | Date | Country |
|---|---|---|
| 2017-98462 | Jun 2017 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20200219650 A1 | Jul 2020 | US |
