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METHOD OF STARTING AN INTERNAL COMBUSTION ENGINE

IP.com Disclosure Number: IPCOM000021327D
Publication Date: 2004-Jan-14
Document File: 8 page(s) / 187K

Publishing Venue

The IP.com Prior Art Database

Abstract

A method of starting an internal combustion engine which minimizes the power needed to rotate the engine until it starts. The method comprises the steps of rotating an engine in the reverse direction until a predetermined load torque level for rotating the engine is obtained and then immediately switching the direction to the normal rotational direction, thereby accelerating the rotation of the engine.

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METHOD OF STARTING AN INTERNAL COMBUSTION ENGINE

The present invention relates to a method of starting an internal combustion engine which minimizes the power needed to rotate the engine until it starts.


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BACKGROUND OF THE INVENTION

Starters are used in all modern vehicles for rotating the engine until the combustion is started such that the engine runs by itself. For larger engines such as diesel engines having a plurality of pistons, the power required to overcome the compression of the pistons in order to rotate the engine is quite significant.

This in turn requires large starters which have to be dimensioned to handle "worst-case" forces. This further puts high demands on the power source of the starter, ie. the batteries, and also on the cables and connections between starter and batteries. The problem becomes even more pronounced when the vehicle is to be equipped with a combined starter /generator, which has gained some interest during recent years. For smaller vehicles these are quite applicable but some problems have arisen for larger vehicles, mainly due to the forces and torques required to rotate the engines. Because this type of starter/generator apparatus is rather complex regarding its construction and because of the dual application it has proven difficult to obtain an apparatus that can provide sufficient power as a generator within the normal revolution range when driving and at the same time provide sufficient torque for starting the engine. In practice it has shown that the starter function or power tends to be somewhat inadequate when optimizing the generator function, thus leading to difficulties in starting the engine, especially when the crankshaft is in a unfavourable starting position.

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A few attempts have been made to reduce the power needed to rotate and start an engine. Document DE 198 17 497 discloses a method comprising using the starter to first rotate the engine crank shaft in either a direction opposite to the starting direction or in the same direction in order to position the crankshaft in a favourable rotational position in relation to the work cycle of the engine, ie. to have a certain rotational distance before the compression builds up in one of the cylinders in order to obtain a momentum that reduces the power needed to overcome the compression.

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US 5,458,098 discloses a similar method where rotational positions of the crankshaft are mapped with load torque needed to rotate crankshaft in order to position the start point so that a certain rotational distance is obtained before compression. The rotation in both directions also reduces the frictional forces in that oil films are built up between moving parts before start.

However non of the disclosed methods fully utilizes the possibilities that the engine possesses for reducing the power needed to rotate the engine. Also, however a lesser problem, both methods require the need for finding and st...