FAIL-SAFE THERMOSTAT DEVICE FOR VEHICULAR COOLING SYSTEMS

摘要

A fail-safe thermostat device (19) for a vehicle cooling system includes a main spring (40) and a valve assembly (37) disposed on an end portion of the main spring (40). A spring retainer (30) is affixed to a thermal actuator (32) and bonded to a poppet valve portion (34) by an eutectic alloy interface (36). A fail-safe spring (38) is compressively disposed between the spring retainer (30) and the poppet valve portion (34). When an engine temperature reaches a value greater than a pre-determined maximum engine operating temperature, the eutectic alloy interface (36) degrades. The compressive force stored in the fail-safe spring (38) overcomes a shear strength associated with the degraded eutectic alloy interface (36) and is sufficiently greater than a tensile force exerted by the main spring (40) on the poppet valve assembly (37). The fail-safe spring (38) then actuates to compress the main spring (40), opening the fail-safe thermostat device (19). This allows coolant to flow freely through the vehicular cooling system, preventing engine damage.