On-demand pumps to save fuel

Modularity facilitates their introduction

Essentially, all pump motors can benefit from on-demand control because Continental has opted for graduated modularity. Pulse-width modulation makes on-demand control a possibility even for conventional DC motors. However, brushless motors (EC motors) whose electrical rotational field is generated in the control electronics are more efficient. These motors alone can further reduce CO2 emissions by approximately 0.3g/km from petrol engines and 0.5 g/km from diesel engines, respectively.

EC motors do not only exhibit dramatically reduced mechanical wear, they are also more impervious to variations in fuel grades. Contaminated fuel, colloquially referred to as ‘bad fuel’, can cause carbon brushes to burn out rapidly. Consequently, brushless motors are ideal for aggressive fuel up to and including E 100, i.e. pure alcohol. As a result of consistent modularity, Continental’s family of EC motors can be exchanged one for one for traditional motors. Here, too, the production part approval process and series production have begun.

Speed is the trump card

For cost reasons, when installed in vehicles, EC motors do not include speed sensors. Because of this, when the engine is started up, there is a brief pause until the engine speed can be calculated from the engine’s electrical counter-pulses. However, since the precise fuel feed pressure needs to be attained as quickly as possible, Continental also incorporates an ASIC module in the control electronics.

This reduces the time before speed synchronisation is reached to just 100ms. Other designs without ASICs need longer synchronisation times – up to 500ms, considerably in excess of what the OEMs specify. Combined with pressure-proof pumps, check valves and pressure relief valves, the inclusion of an ASIC produces a fuel feed system which helps to meet even the most stringent emission requirements despite frequent engine starts.

Modularised fuel feed units

Modularity plays a similarly major role in integral fuel feed units. Since today’s fuel tanks come in the widest possible variety of shapes, some of them complex, every feed unit needs to be tailored to the flange size, height and diameter of the installation space available. Continental achieves this with a modular system which ensures standardisation below the flange. This means that Continental can cover 70 to 80 percent of all applications – at no extra cost.

The company’s tradition of fuel tank system know-how has proved to be an advantage. Continental’s detailed knowledge allows the company to assume total responsibility for fuel feed, including all the feed unit sub-system interfaces to the tank.

“Continental has brought its entire electronics, engine, sensor, valve and filter know-how under a single roof. This means that we can cater for the complete range, from a ‘best cost’ system for the Tata Nano to a twin pump system for ‘high power’ engines,” said Distelhoff. “With over 90 million pumps sold already, we are not only the market leader in Europe but one of the world’s two leading specialists in this area.”

Systematic exploitation of the pump’s control electronics is paving the way for additional benefits. One example is the option of moving to wear-free sensors for measuring the fuel level in the tank. Current systems are generally based on level sensors with sliding contacts. In contrast, analysis by whole-life sensors, such as ultrasound sensors or capacitive gauges, can be very easily integrated into the pump electronics. In order to be able to supply a solution for every requirement, Continental’s frictionless MAPPS fuel level sensor provides a wear-free solution for applications in which no control electronics are yet available.

However, as efficiency becomes a significant factor, ever more vehicles will be equipped with control electronics. This advance can be used, for example, to monitor pump wear. If the feed ratio drops due to ageing, the electronics can adjust it and compensate for any drift. Diagnostic programs can proactively detect wear at the pump stage or identify a blocked fuel filter and issue a service alert. A further important possibility is for the on-board diagnostics (OBD II) to detect fuel tank leaks. At present, this function has to be realised separately whereas, in future, it could be more simply integrated into the fuel pump control electronics.