US Patent 7506622 Valve timing control system

One of retard passages, which supplies working fluid to one of retard chambers, is a dedicated passage. The other remaining retard passages, which supply the working fluid to the other remaining retard chambers, are branch passages, which are branched from a retard passage that serves as a supply passage. With this construction, a flow quantity of working fluid per unit time supplied from the one of retard passages to the one of retard chambers becomes larger than a flow quantity of working fluid per unit time supplied from the other remaining retard passages to the other remaining retard chambers. Thus, the one of retard chambers can be filled with the working fluid earlier than the other remaining retard chambers.