ELECTRICAL 57 12.13 GLOWPLUG CONTROL UNIT OPERATIONAL DESCRIPTION The aim of Glow Plug control Unit (GCU) is to achieve high degree of flexibility in driving the glow plugs that are included in a standard EMS system for diesel engines. It is evident that the requirement for GCU depends from the driving characteristics required by the glow plugs. In a modern direct injection diesel engine the function developed by glow plug may be summarized as follows: Auxiliary starting device Cold diesel engines due to high levels of internal frictions & thermal losses are reluctant to start. Often need of auxiliary devices like glow plugs are the only method to guarantee engine start. The glow plug power dissipation increases the combustion chamber temperature allowing the air fuel mixture to reach its self-ignition condition. Auxiliary combustion control device The air fuel mixture self-ignition points are mainly influenced by two factors: pressure & temperature inside the combustion chamber. The temperature control in all those condition in which the combustion chamber is relatively “cold” (i.e. during cut-off or during post-start) may improve the reduction of ignition delay with large benefit in terms of emission & combustion efficiency. Auxiliary Power Management device The total power dissipation of glow plug is not negligible (it may vary from 240W to 750W according with glow plug characteristics). In some cases, it may be useful to increase the engine load operating point in order to achieve higher exhaust temperature (e.g. in order to start the regeneration of diesel particulate filter). The glow plug activation in this condition may help either directly, increasing combustion temperature indirectly increasing engine load as required. The features of modern Glow plug control unit must allow the EMS to operate in all of above conditions with possibility to choose the driving method & parameter optimization. Pin Description: Pin 30: Direct battery supply. G1 : Power signal for glow plug no.1 G2 : Power signal for glow plug no.2 G3 : Power signal for glow plug no.3 G4 : Power signal for glow plug no.4 Pin 86: Power supply via main relay ST : Command signal from ECU to glow plug controller. DI : Diagnostic feedback signal from glow plug controller to ECU. Pin 31: GND
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