Ignition coil having center core

An ignition coil comprising:

• a primary coil;
• a secondary coil that is arranged substantially coaxially with respect to the primary coil;
• a secondary spool that has a substantially cylindrical shape, the secondary coil being wound around the secondary spool;
• and
• a center core that is located on an inner side of the spool,
• wherein the secondary spool has a tapered inner surface, which is defined at least partially in the secondary spool with respect to an axial direction of the secondary spool,
• the tapered inner surface has a diameter that increases as being distant from a high voltage tip end of the secondary coil, the high voltage tip end of the secondary coil being on a high voltage side of the secondary coil,
• the center core has a tapered outer surface, which is defined at least partially in the center core with respect to an axial direction of the center core,
• the tapered outer surface has a diameter that increases as being distant from the high voltage tip end of the secondary coil, and
• the tapered inner surface of the secondary spool opposes to the tapered outer surface of the center core with respect to a substantially radial direction of the center core.

An ignition coil comprising:

• a primary coil;
• a secondary coil that is arranged substantially coaxially with respect to the primary coil;
• a primary spool that has a substantially cylindrical shape, the primary coil being wound around the primary spool;
• and
• a center core that is located on an inner side of the spool,
• wherein the primary spool has a tapered inner surface, which is defined at least partially in the primary spool with respect to an axial direction of the primary spool,
• the tapered inner surface has a diameter that increases as being distant from a high voltage tip end of the secondary coil, the high voltage tip end of the secondary coil being on a high voltage side of the secondary coil,
• the center core has a tapered outer surface, which is defined at least partially in the center core with respect to an axial direction of the center core,
• the tapered outer surface has a diameter that increases as being distant from the high voltage tip end of the secondary coil, and
• the tapered inner surface of the primary spool opposes to the tapered outer surface of the center core with respect to a substantially radial direction of the center core.

An ignition coil adapted to connecting with a sparkplug for generating spark in a combustion chamber of an internal combustion engine, the ignition coil comprising:

• a primary coil;
• a secondary coil that is arranged substantially coaxially with respect to the primary coil;
• a spool that has a substantially cylindrical shape, one of the primary coil and the secondary coil being an inner coil arranged on an inner side of an other of the primary coil and the secondary coil, the inner coil being wound around the spool;
• and
• a center core that is arranged inside of the spool;
• wherein the spool has a tapered inner surface, which is defined at least partially in the spool with respect to an axial direction of the spool,
• the tapered inner surface has a diameter that increases as being distant axially from the sparkplug,
• the center core has a tapered outer surface, which is defined at least partially in the center core with respect to an axial direction of the center core,
• the tapered outer surface has a diameter that increases as being distant axially from the sparkplug, and
• the tapered inner surface of the spool opposes to the tapered outer surface of the center core with respect to a substantially radial direction of the center core.

An ignition coil that is adapted to connecting with a sparkplug, the ignition coil comprising:

• a cylindrical portion that includes a primary coil, a secondary coil, and a center core, the primary coil and the secondary coil being substantially coaxial with respect to each other;
• and
• a plug holder that is provided to a tip end of the cylindrical portion, the plug holder being adapted to connecting with the sparkplug,
• wherein the center core includes a first end portion, a second end portion, and a center portion,
• the first end portion is located on a side of one end of the center core with respect to an axial direction of the center core,
• the second end portion is located on a side of an other end of the center core with respect to the axial direction of the center core,
• the first end portion occupies 15% or greater in length of the center core,
• the second end portion occupies 15% or greater in length of the center core,
• the center portion is located between the first end portion and the second end portion,
• the first end portion and the second end portion of the center core are formed of a first soft magnetic material,
• the center portion of the center core is at least partially formed of a second soft magnetic material, and
• the second soft magnetic material has a saturation magnetic flux density, which is higher than a saturation magnetic flux density of the first soft magnetic material.

An ignition coil that is adapted to be connecting with a sparkplug, the ignition coil comprising:

• a cylindrical portion that includes a primary coil, a secondary coil, a center core, and an outer core, the primary coil being substantially coaxial with respect to the secondary coil, the center core being arranged on an inner circumferential side of the secondary coil, the outer core being arranged on an outer circumferential side of the primary coil;
• and
• a plug holder that is provided to a tip end of the cylindrical portion, the plug holder being adapted to connecting with the sparkplug,
• wherein the cylindrical portion includes a rear end portion, and
• the center core has a rear end, which at least partially protrude to a rear side axially beyond the outer core in a non-lapping region of the rear end portion of the cylindrical portion,
• the ignition coil further comprising:
• a side plate that at least partially covers the non-lapping region from an outer circumferential side,
• wherein the side plate is formed of a soft magnetic material.

An ignition coil adapted to connecting with a sparkplug, the ignition coil comprising:

• a cylindrical portion that includes a primary coil, a secondary coil, a spool, and a center core, the primary coil and the secondary coil being substantially coaxial with respect to each other, one of the primary coil and the secondary coil being an inner coil arranged on an inner side of an other of the primary coil and the secondary coil, the inner coil being wound around the spool having a substantially cylindrical shape, the center core being on an inner circumferential side of the spool;
• and
• a plug holder that is provided to a tip end of the cylindrical portion, the plug holder being adapted to connecting with the sparkplug;
• wherein the spool has a tapered inner surface, which is defined at least partially in the spool with respect to an axial direction of the spool,
• the tapered inner surface has a diameter that increases as being distant axially from the plug holder,
• the center core has a tapered outer surface, which is defined at least partially in the center core with respect to an axial direction of the center core,
• the tapered outer surface has a diameter that increases as being distant axially from the plug holder,
• the tapered inner surface of the spool opposes to the tapered outer surface of the center core with respect to a substantially radial direction of the center core,
• the center core includes a first end portion, a second end portion, and a center portion,
• the first end portion is located on a side of one end of the center core with respect to an axial direction of the center core,
• the second end portion is located on an axially opposite side of the first end portion with respect to the center portion,
• the first end portion occupies 15% or greater in length of the center core,
• the second end portion occupies 15% or greater in length of the center core,
• the first end portion and the second end portion of the center core are formed of a first soft magnetic material,
• the center portion of the center core is at least partially formed of a second soft magnetic material, and
• the second soft magnetic material has a saturation magnetic flux density, which is higher than a saturation magnetic flux density of the first soft magnetic material.

An ignition coil adapted to connecting with a sparkplug, the ignition coil comprising:

• a cylindrical portion that includes a primary coil, a secondary coil, a spool, a center core, and an outer core, the primary coil being substantially coaxial with respect to the secondary coil being wound around the spool having a substantially cylindrical shape, the center core being arranged on an inner circumferential side of the spool, the outer core being arranged on an outer circumferential side of the primary coil;
• and
• a plug holder that is provided to a tip end of the cylindrical portion, the plug holder being adapted to connecting with the sparkplug,
• wherein the spool has a tapered inner surface, which is defined at least partially in the spool with respect to an axial direction of the spool,
• the tapered inner surface has a diameter that increases as being distant axially from the sparkplug,
• the center core has a tapered outer surface, which is defined at least partially in the center core with respect to an axial direction of the center core,
• the tapered outer surface has a diameter that increases as being distant axially from the sparkplug,
• the tapered inner surface of the spool opposes to the tapered outer surface of the center core with respect to a substantially radial direction of the center core,
• the cylindrical portion includes a rear end portion on an axially opposite side of the plug holder, and
• the center core has a rear end, which at least partially protrude to the axially opposite side of the plug holder axially beyond the outer core in a non-lapping region of the rear end portion of the cylindrical portion,
• the ignition coil further comprising:
• a side plate that at least partially covers the non-lapping region from an outer circumferential side,
• wherein the side plate is formed of a soft magnetic material.

An ignition coil that is adapted to connecting with a sparkplug, the ignition coil comprising:

• a cylindrical portion that includes a primary coil, a secondary coil, a center core, and an outer core, the primary coil being substantially coaxial with respect to the secondary coil, the center core being arranged on an inner circumferential side of the secondary coil, the outer core being arranged on an outer circumferential side of the primary coil;
• and
• a plug holder that is provided to a tip end of the cylindrical portion, the plug holder being adapted to connecting with the sparkplug,
• wherein the center core includes a first end portion, a second end portion, and a center portion,
• the first end portion is located on an axially opposite side of the second end portion with respect to the center portion,
• the first end portion occupies 15% or greater in length of the center core,
• the second end portion occupies 15% or greater in length of the center core,
• the first end portion and the second end portion of the center core are formed of a first soft magnetic material,
• the center portion of the center core is at least partially formed of a second soft magnetic material,
• the second soft magnetic material has a saturation magnetic flux density, which is higher than a saturation magnetic flux density of the first soft magnetic material,
• the cylindrical portion includes a rear end portion on an axially opposite side of the plug holder, and
• the center core has a rear end, which is at least partially protrude to an axially opposite side of the plug holder axially beyond the outer core in a non-lapping region of the rear end portion of the cylindrical portion,
• the ignition coil further comprising:
• a side plate that at least partially covers the non-lapping region from an outer circumferential side,
• wherein the side plate is formed of a soft magnetic material.