Empty switch
Empty gas switch (short: LGS in the automotive and engine industry) is a switch or pulse generator that is used to control the injection system in internal combustion engines. The objective is to recognize the overrun mode and thus the implementation of the overrun cut-off for the purpose of reducing fuel consumption.
technical description
The detection of overrun - d. H. the vehicle drives the engine - based on two basic assumptions:
- There is no gas
- The engine speed is significantly higher than the self-maintenance speed (idling)
The empty gas switch is located in the intake duct of the combustion air and is in direct connection with the throttle valve . In the case of mechanical injection pumps, the empty gas switch is equipped with an NC or NO contact . A lifting magnet, which is connected to the injection pump via a linkage , is actuated according to the position of the accelerator pedal .
In modern injection systems controlled by an engine control unit, LGS and a digital pedal value transmitter (PWG) switch their values (position of the accelerator pedal) to a memory register. These counted values are compared with a setpoint adjusted to the engine characteristics. If the signals from the pedal value from the PWG transmitter and the contact of the empty gas switch are plausible, the corresponding injection value is released.
How it works using the example of a mechanical injection system
When the accelerator pedal is in the idle position and the throttle valve is closed (engine speed <1000 / min), the empty gas switch cuts off the power supply to a lifting magnet. The lifting rod then closes the fuel supply. This operating state is known as overrun fuel cutoff .
In engines in connection with automatic transmissions , the empty gas switch is often coupled with a kickdown switch, which is located under the accelerator pedal. If the pedal is suddenly depressed from the idle position, the throttle valve opens fully. The contacts of the empty gas switch and the kickdown switch close, the lifting magnet picks up and the lifting rod releases the full injection quantity.
Applications
Mercedes-Benz used such an additional device in its USA vehicles in the 1970s. For this purpose, the mechanical injection pump had a stop magnet that could pull the control rod to zero delivery. Temperature switch on the cylinder head, an oil pressure switch (automatic transmission) and an empty gas switch on the throttle body controlled the stop magnet.
Web links
Individual evidence
- ↑ Empty gas switch in: Ralf Deußen: Master knowledge in the automotive trade. Vogel, Würzburg 2003, p. 381. ISBN 3834331031