For decades now, Pierburg GmbH has been developing vacuum pumps for brake boosters, and the new EVP 40 operates on demand, is rugged and extremely durable, with a life-span of up to 1200 hours. The pump is in a high volume-production for a leading global OEM.
The development of a new product for the auto industry poses enormous challenges for engineers and developers on each occasion. From the initial concept, product development is like a journey through various topic areas and stations. These include, to name but a few, issues of design and configuration, simulations, the analysis of temperature measurements as well as accelerated ageing tests.
Emphatic downsizing has been a dominant trend in engine design over the past decade, with smaller engines, in particular, being turbocharged. However, under zero-load conditions, these modern gasoline engines cannot ensure the vacuum in the intake pipe necessary for the brake booster. And the demand for more efficiency and progressing electrification entails the need to come up with completely new systems for the auxiliary units. Vacuum brake boosters are cost effective, but they do need an efficient, engine-independent source for the necessary vacuum to be called up at any time. It is precisely with this in mind that Pierburg has developed the EVP (Electric Vacuum Pump).
Life-span, endurance strength, efficiency
Pierburg's extensive experience in developing mechanical pumps proved to be of vast value in the design of the EVP. During the development phase, special emphasis was placed on reliability and life-span. After all, vehicle performance must be assured at all times, and the brake system, in particular, assumes top priority from in this respect. Other important aspects were endurance strength and performance reproducibility. The pump was required to undergo an extensive testing regime, including temperatures ranging from -40 °C to +120 °C. A specifically developed non-electronic robust brush motor was designed to provide the necessary efficiency.
Noise, Vibration and Harshness (NVH)
The electric vacuum pump is just as much at home in hybrid and electric vehicles as in vehicles with conventional drivelines. The objective was for the pump system to be barely audible when driving, especially important on electric and hybrid vehicles which are, by their very nature, quiet running. Since pump and integrated motor were specifically developed inhouse for this project, Pierburg engineers were able to devise cost-effective mounting solutions with no need for costly vibration insulation. In fact, the entire pump system has outstanding structure-borne noise insulation and low air-borne noise emissions. It can thus be mounted on body parts without causing distracting vibrations in the vehicle's structure.
An integrated check valve delivers additional customer value and makes it easier and less costly for the EVP to be installed in the vehicle. Straightforward mounting, independent of the other assemblies, allows installation-space conflicts to be resolved.
Background info: electric vacuum pumps
Though less costly, mechanical vacuum pumps directly connected to the IC engine have the drawback that they are continuously running along with the vehicle, irrespective of whether this is necessary and, depending on the operating mode, even at high RPM. Conversely, electric vacuum pumps switch off when the brakes are not applied. In this way, fuel consumption and emissions are curbed. The fact that there is no mechanical pump also means less work for the engine lubrication system, as no extra oil is needed for lubricating the vacuum pump. This means the oil pump can have more compact dimensions which, in turn, boosts engine efficiency. Another asset: the oil pressure rises at the spot at which a mechanical vacuum pump would normally be mounted, which is the cylinder head in most cases.
On hybrid vehicles, electric vacuum pumps allow all-electric motion with the IC engine switched off. At the same time, the power braking function is fully available. This type of pump also allows the vehicle to run in coasting mode, with the engine switched off and disconnected for additional fuel savings thanks to reduced drive train resistance (extended start-stop operation)