| 摘要 |
A glow plug or plugs for a Diesel engine is energized directly or indirectly through the normally closed contacts of a thermally operated switch, preferably a bimetal switch, in thermal communication with the engine and a local electric heater that is energized by the same source as the glow plug and controlled in unison with the glow plug. The bimetal switch is arranged to switch off at a temperature of the order of 80 DEG C. which, at an initial engine temperature of the order of -18 DEG C., permits the glow plug to heat to the order of 900 DEG C. The hysteresis in the bimetal switch is arranged to close the switch when the glow plug has cooled to the order of 810 DEG C., thus the glow plug is cycled between the order of 800 DEG C. and 900 DEG C. It has been found that the glow plug temperature rise at elevated temperatures is substantially less than proportional to heat input. As a consequence, the effect of lower engine temperature is to produce increased glow plug temperature less than proportional to the bimetal temperature rise over engine temperature prior to switch opening, and the effect of increased engine temperature is to lower the glow plug temperature less than in proportion to the lesser bimetal temperature rise over engine temperature. With proper selection of the bimetal switch characteristics, the variation of glow plug temperature with engine temperature substantially matches the engine requirement for ease of start. Further, the glow plugs are initially heated at a very rapid rate and reach temperatures suitable for engine crank more quickly than with conventional, continuous, glow plug energization. |
