Non-uniform stroke duration apparatus and engine provided with the same

An engine comprising:

• a crankshaft including a first main crankshaft and a second main crankshaft coaxially disposed with the first main crankshaft and constantly rotating at the same speed as the first main crankshaft and having a predetermined crankshaft rotation center;
• a first pin journal portion including a first crank pin and a large diameter portion protruding in a crankshaft direction;
• a second pin journal portion including a second crank pin, a third crank pin and first and second journal shafts protruding in both directions in the crankshaft direction;
• a third pin journal portion including a fourth crank pin and a large diameter portion protruding in the crankshaft direction;
• a first eccentric unit disposed between the first main crankshaft and the first pin journal portion, including a first internal bracket that rotates around a first eccentric axis formed by a pivot angle in a predetermined first direction and is spaced apart from the crankshaft rotation center by a predetermined first eccentric distance, and changing a relative rotation speed of the first pin journal portion with respect to the crankshaft;
• a second eccentric unit disposed between the first pin journal portion and the second pin journal portion, including a second internal bracket that rotates around a second eccentric axis formed by a pivot angle in a predetermined second direction and is spaced apart from the crankshaft rotation center by a predetermined second eccentric distance, and changing a relative rotation speed of the second pin journal portion with respect to the first pin journal portion;
• a third eccentric unit disposed between the second pin journal portion and the third pin journal portion, including a third internal bracket that rotates around a third eccentric axis formed by a pivot angle in the predetermined first direction and is spaced apart from the crankshaft rotation center by the predetermined second eccentric distance, and changing a relative rotation speed of the third pin journal portion with respect to the second pin journal portion;
• and
• a fourth eccentric unit disposed between the third pin journal part and the second main crankshaft, including a third internal bracket that rotates around a fourth eccentric axis formed by a pivot angle in the predetermined second direction and is spaced apart from the crankshaft rotation center by the predetermined first eccentric distance, and changing a relative rotation speed of the second main crankshaft with respect to the third pin journal portion.