Ignition coil for internal combustion engine
An ignition coil has primary and secondary coils, a coil casing having a casing body, an accommodating part and a high voltage tower shaped part of a cylindrical shape, a resistance member arranged as a movable member in a tower through hole of the high voltage tower, a high voltage cap, and an insulation resin member with which the accommodating part is filled. A proximal end part of the tower through hole has an inner diameter which is greater than an outer diameter of a maximum outer diameter part of the resistance member. A distal end part of the tower through hole has an inner diameter which is less than the outer diameter of the maximum outer diameter part of the resistance member. A vent part is formed, through which the proximal end part of the tower through hole communicates with the distal end part of the tower through hole.
1. An ignition coil comprising:
a primary coil;
a secondary coil;
a coil casing comprising a casing body, an accommodating part formed in the casing body and a high voltage tower shaped part having a cylindrical shape, the accommodating part accommodating the primary coil and the secondary coil, the high voltage tower shaped part being formed projecting toward the outside of the casing body, a proximal end part of the high voltage tower shaped part being arranged in contact with a bottom surface of the accommodating part, a tower through hole being formed in the high voltage tower shaped part;
a resistance member having a cylindrical shape arranged as a movable member in the tower through hole;
a high voltage cap arranged at the proximal end part of the high voltage tower shaped part so as to prevent communication between the tower through hole and the accommodating part, and the high voltage cap electrically connecting the resistance member with a high voltage terminal connected to the secondary coil; and
an insulation resin member with which the accommodating part is filled, wherein
a proximal end part of the tower through hole has an inner diameter which is greater than an outer diameter of a maximum outer diameter part of the resistance member, and a distal end part of the tower through hole has an inner diameter which is less than the outer diameter of the maximum outer diameter part of the resistance member, and
a vent part is formed, through which the proximal end part of the tower through hole communicates with the distal end part of the tower through hole when the resistance member is arranged at a maximum distal end position in the tower through hole.
2. The ignition coil for an internal combustion engine according to claim 1 , wherein the vent part is a groove formed on an inner peripheral surface of the tower through hole along an axial direction of the tower through hole.
3. The ignition coil for an internal combustion engine according to claim 2 , wherein the vent part is formed at two or more parts on the inner peripheral surface of the tower through hole along an axial direction (X) of the tower through hole.
4. The ignition coil for an internal combustion engine according to claim 3 , wherein a cross sectional area of the vent part, which is perpendicular to the axial direction of the tower through hole, located at an opening part formed at the distal end part of the tower through hole, and an inside volume of a proximal end chamber formed at the proximal end part in the tower through hole, satisfy a relationship expressed by an equation of S/∛(V)≥0.006 (mm).
5. The ignition coil for an internal combustion engine according to claim 2 , wherein a cross sectional area of the vent part, which is perpendicular to the axial direction of the tower through hole, located at an opening part formed at the distal end part of the tower through hole, and an inside volume of a proximal end chamber formed at the proximal end part in the tower through hole, satisfy a relationship expressed by an equation of S/∛(V)≥0.006 (mm).
6. The ignition coil for an internal combustion engine according to claim 1 , wherein the vent part is one of a cut part and a groove formed on an outer peripheral surface of the resistance member along an axial direction of the resistance member.
7. The ignition coil for an internal combustion engine according to claim 6 , wherein the vent part is formed at two or more parts on the outer peripheral surface of the resistance member along an axial direction (X) of the resistance member.
8. The ignition coil for an internal combustion engine according to claim 7 , wherein a cross sectional area of the vent part, which is perpendicular to the axial direction of the tower through hole, located at an opening part formed at the distal end part of the tower through hole, and an inside volume of a proximal end chamber formed at the proximal end part in the tower through hole, satisfy a relationship expressed by an equation of S/∛(V)≥0.006 (mm).
9. The ignition coil for an internal combustion engine according to claim 6 , wherein a cross sectional area of the vent part, which is perpendicular to the axial direction of the tower through hole, located at an opening part formed at the distal end part of the tower through hole, and an inside volume of a proximal end chamber formed at the proximal end part in the tower through hole, satisfy a relationship expressed by an equation of S/∛(V)≥0.006 (mm).
10. The ignition coil for an internal combustion engine according to claim 1 , wherein a cross sectional area of the vent part, which is perpendicular to the axial direction of the tower through hole, located at an opening part formed at the distal end part of the tower through hole, and an inside volume of a proximal end chamber formed at the proximal end part in the tower through hole, satisfy a relationship expressed by an equation of S/∛(V)≥0.006 (mm).