| 摘要 |
A control for modulating the duty cycle of diesel engine glow plugs has two heat sensitive, normally closed switches each thermally coupled to a respective positive temperature coefficient (PTC) of resistivity heater in turn thermally coupled to and mounted on a common heat sink. The heat sensitive switches are serially connected to each other, to an ignition switch and to a glow plug relay. The PTC heaters are connected to a point between the heat sensitive switches and the relay and to ground. A third PTC heater is mounted on the heat sink intermediate the first and second heaters and thermally coupled to the heat sink. The third heater is connected to an alternator and serves to cut off power to the glow plugs after a selected after glow stage. The two heat sensitive switches can be selected to open at approximately the same temperature for a random operating mode or at slightly different temperatures for a sequential operating mode. The random operating mode is a redundant high reliability operating mode whereas the sequential operating mode, using slightly different temperatures allows one switch to control the cycling and the second to be a back up safety control. In one preferred embodiment a "wait" lamp is connected between the ignition switch and a double pole relay used to latch the lamp in the deenergized state when the first "off" time of the heat sensitive switches occurs. In a second embodiment the "wait" lamp is connected between the alternator and the coil of the glow plug relay with a diode serially connected to the lamp to preclude alternator current from energizing the lamp.
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