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Epoxy system for diesel valve encapsulation

27 February 2009

Robert Bosch is a global supplier of technology and services to the automotive and consumer goods manufacturing industries and the construction industry. A key area for the company is the supply of automotive components to many of the leading marques including Audi, BMW, Daimler, Ford, Peugeot, Porsche, Renault and Volvo. Components range from ignition coils, power diodes and ABS-modules to generators and diesel magnet valves.

During the manufacture of these components, a range of epoxy based materials supplied by Huntsman Advanced Materials are used for encapsulation, impregnation, bonding and sealing applications.

However, for the production of Bosch diesel magnet valves or solenoids, used in several diesel injectors for heavy goods vehicles and yachts, Bosch and Huntsman have worked together to develop a unique material - a single component, mineral filled epoxy - able to meet the very specific mechanical and environmental demands placed on these components.

Diesel injectors have comparatively few moving parts but what does move does so in a complex way. The magnet valve controls the metering, timing and distribution of fuel delivery in the fuel channel .

Because of its position within the diesel injectors, the magnet valves are continually exposed to diesel fuel and temperatures up to 150°C, so the encapsulation and impregnation materials used on this component must be absolute.

“We worked with Huntsman to develop the formulation for this special epoxy based product for us,” explains Jens Rapp, head of manufacturing at Robert Bosch, Diesel Systems. “We needed a system with very good flow to ensure even impregnation around the valve and good sealing properties. Critically, it also had to have excellent chemical resistance to hot diesel oil to cope with the environmental conditions inside the injection pump.

“To make sure the system could do this, we ran tests on the encapsulated valves immersing them for 1000 hours in diesel oil heated to 160ºC - and they completed the tests successfully.”


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