| 摘要 |
A thermostatic valve 20 is provided for controlling coolant flow through an exhaust gas recirculation (EGR) cooler 16 in an engine cooling system. The valve 20, termed an EGR mixer valve, is in an engine cooling system having a radiator 8, a pump 2 to circulate coolant through an engine supply line SL to the engine 3, from the engine 3 through an engine return line ER to the radiator or through a bypass BL. Coolant from the radiator 8 is returned to the pump 2 through a radiator return line RR and a main thermostat 5 which is also connected to the bypass such that it blocks radiator return flow until bypass temperature has risen to a temperature just below the normal engine running temperature. The EGR mixer valve 20 has a first inlet 31 connected to the engine return line, a second inlet 32 connected to the radiator return line and an outlet connected to the EGR cooler. In one embodiment, valve 20 has a biassed shuttle having a valve member (25, fig 2) which at lower coolant temperatures closes off the second inlet 32 to prevent the flow of coolant at ambient temperature from the radiator return line while permitting flow of warmer coolant from the engine return line through to the EGR cooler. The second inlet 32 is opened at higher temperatures when a wax thermal actuator (19, fig 2) pushes the shuttle towards the first inlet 31 to unseat the valve member. The wax actuator has a casing exposed to coolant at both inlets 31, 32 so that the sensed temperature is a weighted average of the temperature at the first inlet and ambient temperature at the second inlet 32 and this provides ambient compensation. In other embodiments, temperature is sensed by other means such as bi-metallic expansion or thermocouples. |
