Patent ID: 7730863

Claim:
A warm-up apparatus for an internal combustion engine, the warm-up apparatus comprising: a latent heat type heat storage material accommodated in the internal combustion engine, undergoing phase transition between a liquid phase including a supercooled state and a solid phase, and increasing volume as temperature increases in the liquid phase; and a nucleation device arranged in the heat storage material and operated to accelerate phase transition of the heat storage material in the supercooled state to release heat, wherein the nucleation device includes: a nucleation portion for nucleating and changing the phase of the heat storage material in the supercooled state; a hammer movable toward the nucleation portion and away from the nucleation portion along a predetermined axial direction; a target member for applying impact to the nucleation portion by abutting against the hammer when the hammer moves forward in a first direction along the axial direction; a spring urging the hammer in the first direction along the axial direction, the spring being compressed when the hammer moves backward in a second direction along the axial direction by making use of the increase in the volume of the heat storage material when heat is received from the internal combustion engine and phase transition from the solid phase to the liquid phase occurs; and a lock mechanism restraining the hammer at a predetermined position in the axial direction in a state in which the spring is compressed when the temperature of the heat storage material in the liquid phase is low and the volume of the heat storage material is decreased, the lock mechanism being released by vibrations generated when the internal combustion engine is started so that the hammer is abutted against the target member by the urging force of the spring to apply an impact to the nucleation portion in order to activate the nucleation device and cause phase transition of the heat storage material in the supercooled state.