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Method and system for starting an internal combustion engine having an AC starter and a DC starter

IP.com Disclosure Number: IPCOM000009749D
Publication Date: 2002-Sep-16
Document File: 4 page(s) / 29K

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US-6240890-A: PATENT

Abstract

Three methods and a system for starting an internal combustion engine in a vehicle, which comprises a direct current motor and an alternating current motor for starting the internal combustion engine. One of the methods comprises the steps of: activating the direct current motor for starting the internal combustion engine; activating the alternating current motor when a certain speed of the internal combustion engine is reached, at which speed efficiency of the alternating current motor is substantially equal to the efficiency of the direct current motor; deactivating the direct current motor when the alternating current motor has started; and deactivating the alternating current motor when the internal combustion engine is able to run on its own.

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Method and system for starting an internal combustion engine having an AC starter and a DC starter

Technical Field of the Invention

The invention relates to a method and a starting system for starting an IC engine in a vehicle.

Background of the invention

A starting system for an IC engine (Internal Combustion engine) in a vehicle, such as a truck and a car, normally comprises a battery-driven DC motor (Direct Current motor) as a starter motor for the IC engine. An AC motor is not normally appropriate as a starter motor since it requires much more energy to be able to start a stationary IC engine.A minimum rotational speed required to start the IC engine depends on several factors, such as the number of cylinders, engine type, compression, engine temperature and additional loads driven by the IC engine. Also, each discharge at every start decreases the lifetime of a battery unit for the vehicle although it is recharged afterwards. If the battery unit is discharged and recharged a large number of times within a short time period, the capacity of the battery unit is decreased even more.

During so-called stop-and-go traffic, e.g. during rush hour in big cities or on roads having several traffic lights within short distance from each other, a vehicle is stopped to a standstill and driven forward several times within a short time period. In order to reduce the pollution from the IC engine, it would be advantageous to turn off the IC engine during standstill and then start it again as soon as the vehicle should move forward. However, a heavy truck with a large Diesel engine normally requires a relatively powerful DC starter motor, but such a DC-motor would not be able to withstand all the starts in stop-and-go traffic, if the IC engine would be turned off every time the truck is stopped.

In general a starter motor must supply more power as temperature drops due to increased torque being required as well as a higher starting speed. Also, the battery unit supplies less power as the temperature decreases. The battery unit and the DC motor must be able to achieve a cold start, i.e. starting the IC engine after it has been turned off for an extended period of time, in a relatively cold environment. Thus they generally has to be larger in order to be reliable in a cold environment.

DE-19533016-A1 discloses an arrangement for driving a vehicle in stop-and-go traffic without starting an internal combustion engine positioned in the vehicle. In a first and second embodiment, an electric motor is used for starting the combustion engine or driving the vehicle forward without utilising the internal combustion engine during stop-and-go driving. A third embodiment comprises a first electric motor situated on the combustion engine side of a power train and a second electric motor situated on the gear box side of the power train. The first electric motor is used for starting the combustion engine and the second electric motor is used for driving the vehicle. Hence...