To prevent an endless belt from slipping and improve durability of the endless belt by providing an input pulley 10 in a water pump 2 for circulating cooling liquid for an internal combustion engine 1 which contacts with the endless belt 9 for transmitting power from an output shaft 5 of the internal combustion engine to at least an engine accessory 3 so that the water pump is rotated and driven by the endless belt.
A rotatable idler pulley 11 is arranged for a part of the water pump adjacent to the input pulley so as to contact with the endless belt. This idler pulley is operated in accordance with temperature of the cooling liquid so that the endless belt is separated from the input pulley of the water pump when the temperature of the cooling liquid is low and the endless belt is contacted with the input pulley of the water pump when the temperature of the cooling liquid is high.
Tadashi Higashino
Hiroyuki Nishi
Ryuichi Watanabe
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