Technology, easily understood:

So that a combustion engine can always generate sufficient power, the fuel has to be transported from the tank to the engine continuously. This takes place behind the scenes, often with the assistance of dependable, maintenance-free components from Siemens VDO. Fuel delivery systems with return feeds are still widely used. These systems pump a constant amount of fuel to the engine, enough to enable the car to achieve maximum engine output if needed. If the power needed is less than that, the excess fuel flows back to the tank via a return conduit so that not a drop is wasted.

The heart of the delivery system is the fuel pump, which is either designed as a flow pump or a gerotor pump. A flow pump works with a paddlewheel – like the steamers that used to ply the Mississippi. With a gerotor pump, the fluid is compressed, and thus pushed forward, by a cogwheel that rotates within another cogwheel. So that any small impurities that may be added to the fuel during this process do not damage the engine, the fuel also has to pass through an ultra-fine filter on its way.

For the future, Siemens VDO has developed fuel delivery systems controlled by demand – using electronic controls, the pump always delivers only as much fuel as is needed in a certain driving situation. This reduces the wasted output of the pump, increases the pump’s lifetime, reduces noise, and finally, saves fuel.

A display in the cockpit ensures that the driver always knows how much fuel remains in the tank. A data link provides it with information on the fill status. Nowadays, the fill level is mainly measured by a float gauge connected via a lever arm to a thick-film network. In this network, the electrical resistance changes depending on the position of the lever arm – thereby also changing the signal received by the fuel gauge. As an alternative to this, so-called tubular tank sensors are also being installed worldwide. Two resistance wires are tensed in the tube, with a float gauge sinking down the tube in accordance with the level of fuel. Finally, the electronic system determines the fuel level on the basis of the different resistance sensed depending on the position of the float gauge.

Siemens VDO also makes it possible for its customers to measure fill levels using its magnetic passive position sensor (MAPPS), which has been launched in series production. Despite its complicated name, the concept is very simple: The sensor, about four centimeters long, is encapsulated and installed upright in the tank. The core of the sensor is made up by 52 pliable metal guides arranged next to one another like the keyboard of a piano. The lever arm moved by the float gauge works here on a magnet two millimeters in size. If the tank is full, the float gauge is at the top – and so is the magnet. As the amount of gasoline is reduced, the magnet slowly moves toward the bottom. The magnet is installed so closely to the sensor that it exerts a pull on the metal guides. When pulled, the guides make contact with a metal bar. The location where contact is made corresponds to a characteristic electrical resistance from which the system concludes the fill status directly. The MAPPS is a so-called “closed contact system.” This means that the sensor does not come directly into contact with the fuel itself. In this way, a vehicle with MAPPS technology reliably shows the vehicle operator how much fuel is left in the tank, even after years of hard use in construction work, using different fuels.

These developments from the fuel experts at Siemens VDO do not take center stage. And yet they are responsible for keeping today’s cars, construction vehicles, and tractors moving.

There is a photo to go with this press release. The image and the press release are available for downloading online at http://www.siemensvdo.com/press.

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