The Tribology of Internal Combustion Engines

Citation

Wilson, B. (1998), "The Tribology of Internal Combustion Engines", Industrial Lubrication and Tribology, Vol. 50 No. 5. https://doi.org/10.1108/ilt.1998.01850eae.003

The Tribology of Internal Combustion Engines

The Tribology of Internal Combustion EnginesCollected papers from the one day seminar and evening meeting held at the University of Birmingham on 7 November 1996

Mechanical Engineering PublicationsLondon1997133 pp.ISBN 1 86058 071 8 (hard covers)Price £45-00 (+10% for customers outside the UK)

Keywords: Combustion, Engine, Tribology

Environmental legislation past, present and future was the topic of the presentation by J.J. Toulmin, Rover Group. The impact of vehicles on the environment is becoming a major factor in determining the design of engine. Design changes include four values per cylinder, electronic ignition, evaporative emission control and exhaust gas recirculation. The first emissions legislation was introduced in California in 1963, followed two years later by US federal emissions legislation. The clean air act requiring a 90 per cent reduction in vehicle exhaust emissions was first applied to new motor vehicles in 1968. The target has now become better than a 99 per cent reduction by the year 2003. Europe has lagged behind the USA, taking 15 years to achieve what the USA did in seven. Table I gives a summary. Noise pollution in Europe has been reduced since 1970 from 82dB(A) to 74dB(A) today and a predicted 71 in 2003/2004 for passenger cars. The corresponding values for heavy trucks are from 91 to 80 today with 76 dB(A) predicted in the future. There are no US federal noise standards for cars. To ensure the maintenance of emission standards on-board diagnostics have been found necessary and there is a move towards harmonisation to reduce the waste resulting from the differing requirement of the major markets. The EU Commission has proposed that 85 per cent of vehicles should be recycled by the year 2003 and 95 per cent by 2015. Only 5 per cent of this can be recycled energy through incineration.

Pistons and cylinders

The contribution from Dr Mike Wilcock, AE Goetze, comprised mainly his presentation illustrations and tables together with some comments on them. These included damage to the top piston ring groove referred to as "ring weld", protective coatings for pistons grooves and skirts, diesel and petrol engine piston design, materials development and piston cooling. Reducing the top land (the part of the piston above the top ring) below 3mm has been shown ineffective in reducing emissions because below this the top land crevice volume is less significant than other crevices such as gasket and valve pockets. The provision of cast-in oil cooling galleries in light vehicle diesel (LVD) pistons can reduce local temperatures by as much as 30ºC and result in an increase in the life of the piston by a factor of five. As piston assemblies can account for up to 44 per cent or more of total engine friction, reduced piston friction can reduce specific fuel consumption.

John S. Lenthal, GKN Sheepbridge Stokes, described the evolution of cylinder bore surface finishing methods since the 1970s to meet the current needs. Today sophisticated, multi-stage honing machines are used to minimise oil consumption and the emission of particulate materials (PM).

Cylinder bores are coarse turned with carbide tools, fine turned with a single ceramic tool. Free ferrite in the cast iron should be avoided if cubic boron nitride (CBN) tools are used because it reduces the performance of the CBN. Compared with traditional cross-hatched cylinder bore surface finish 1990's bores have smoother, flatter surface topography plateaux with narrower, shallower oil retaining valleys of a controlled depth to reduce oil retention and therefore oil consumption. This is illustrated by changes in plateau surface specifications shown in Table II.

Bore finishing methods aim to minimise surface deformation and expose graphite flakes. There is renewed interest in induction hardened bores to resist the abrasive wear caused by recirculation of hard particulate materials.

DIN 4776 and Euro 1 and 11 cylinder bore specification parameters are detailed.

Bearings

Developments affecting the performance and manufacture of the widely used aluminium tin silicon alloy lined crankshaft bearings are detailed in the chapter by W.P. Brown, Glacier Vandervell Europe.

Camshaft and follower

The performance and developments in camshaft technology were described by A.C. Brooks, Ford Motor Company. The advantages and drawbacks of the different types, including push rod, overhead cam, finger and roller follower, compound valve head, direct acting baucket, roller rocker arm, mechanical and hydraulic lash adjusters were outlined. Conventional materials and their permissible stresses for sliding and rolling contacts were listed. Future developments were hollow camshafts, assembled shafts, lightweight components, and the operation of two valves by one cam lobe and four valves per cylinder by a single camshaft were. The aim is to reduce friction and weight by moving away from sliding contacts, hydraulic lash adjusters and heavy solid cast iron components.

Ring zone lubrication

Professor Fox, De Montfort University's paper described the work of the Lubricant Research Centre sampling oil from the pistons of petrol and diesel engines reviewed elsewhere. He found that the lubricant in the ring zone was substantially degraded compared to oil in the sump.

Automotive lubricants

Dr A.J. Moore, BP Oil Technology, reviewed the role of oil and its quality approval, covering aspects such as fuel efficiency performance, zinc and soluble molybdenum compound additives and viscosity control.

Jaguar AJ/V8 engine

The final paper described the conception, development and performance of the new Jaguar 4 litre 4 valve per cylinder engine and reproduced the illustrations used in the evening presentation on the 7 November 1996. Advantages over existing comparable Toyota, BMW and Mercedes engines were stressed. Cylinder bores are Nikasil nickel silicon carbide electroplated aluminium alloy with a surface finish of 3mm Ra. The engine develops 54kW per litre, delivers a peak torque of 393Nm at 4,250rpm and weighs 200kg. The complex engine management system is described in detail.

This publication is a permanent record of the very successful meeting which stimulated a great deal of revealing discussion. It is unfortunate that the points raised could not be included, but even without them this book is excellent value for the engine specialist, tribologist and interested professional.

Bill Wilson