Bicycle crank transmission apparatus

A bicycle crank transmission apparatus comprising:

• a hollow shaft member;
• a base plate having a first side securely coupled to the shaft member and a second side, opposite to the first side, installed securely on a bottom bracket equipped with a spindle;
• a chainring housing which is rotatably coupled to the shaft member and has a ring gear securely fixed to the chainring housing inside the chainring housing;
• a reduction gear unit arranged in a center of the ring gear, including:
• an eccentric guide arranged in the center of the ring gear, securely installed on the shaft member, and having an eccentric hole which has an eccentric center;
• and
• an eccentric gear provided to rotate along an external circumference of the eccentric guide and having eccentric gear teeth each including a first part protruded from an outer circumference of the eccentric gear in a radial direction of the eccentric gear and a second part protruded from the first part in a direction parallel to a centric axis of the eccentric gear,
• wherein the eccentric gear includes a first portion spaced apart from the eccentric center with a first distance, and a second portion opposite to each other and spaced apart from the eccentric center with a second distance longer than the first distance, and
• wherein the external circumference of the eccentric guide engages with an internal circumference of the first portion of the eccentric gear, and the first part of the eccentric gear teeth formed at the second portion of the eccentric gear engages with ring gear teeth formed at an internal circumference of the ring gear;
• a directly-coupled ratchet unit installed on the ring gear, including:
• multiple directly-coupled ratchets, which are installed at intervals on an external circumference of the ring gear and expand in a radial direction of the ring gear, and each having operating protrusions on one side, and
• a directly-coupled ratchet clutch in a circular ring shape in which the multiple directly-coupled ratchets are surrounded, which is located on one side of the ring gear, and having indentations configured to receive the operating protrusions, supports configured to support the operating protrusions, and multiple elastic ratchets provided at intervals on an external circumference of the ratchet clutch, wherein the indentations and the supports are alternately formed at intervals on an internal circumference of the ratchet clutch;
• a crank cover including:
• a coupling shaft formed at a center of the crank cover and coupled to the spindle;
• clutch ratchet teeth formed on an internal wall surface of the crank cover and engaged with the elastic ratchets of the directly-coupled ratchet clutch;
• and
• directly-coupled ratchet teeth formed on the internal wall surface of the crank cover and engaged with the directly-coupled ratchets expanded in the radial direction of the ring gear, wherein the clutch ratchet teeth and the directly-coupled ratchet teeth are arranged next to each other along a circumferential direction of the internal wall surface of the crank cover;
• and
• a sun gear which is installed on the coupling shaft of the crank cover in such a way that the sun gear only rotates in a first circumferential direction and the sun gear is partially engaged with the second part of the eccentric gear teeth formed at the first portion of the eccentric gear.