Engine structure with length-variable connecting rod

The utility model provides an engine structure with a length-variable connecting rod. The upper end of a connecting rod small head is hinged to a piston, a connecting rod large head is hinged to a connecting rod journal, a cavity and an arc-shaped slideway are arranged in the connecting rod large head, an auxiliary connecting rod and a fan-shaped swing block are arranged in the cavity, the upper end of the auxiliary connecting rod is hinged to the lower end of the connecting rod small head, the lower end of the auxiliary connecting rod is hinged to the upper end of the fan-shaped swing block, the inner right end of the arc-shaped slideway is provided with a return spring, the fan-shaped swing block swings along the arc-shaped slideway and enables the right end to be abutted against the left end of the return spring, the left lower end of the fan-shaped swing block is hinged to the upper end of a small connecting rod, a rocking arm is hinged at the lower part of the connecting rod large head, the upper end of