1. Field of the Invention
The present invention relates to an apparatus and method for controlling an electrical starter motor for cranking or starting an internal combustion engine, comprising a circuit means for making an electrical connection between a voltage source and the electrical starter motor, in which the electrical starter motor is coupled with a crank gear of the internal combustion engine by means of a shiftable transmission when the circuit means is energized.
2. Prior Art
It is known that an internal combustion engine in a motor vehicle must be started by means of a starter motor, since it cannot be started alone without other means. Usually an electrically driven starter motor, that is connected with a voltage source by means of a starter relay formed as a so-called engagement or tripping relay, is provided for this purpose. At the same time a pinion of the starter motor is put into engagement with a crown gear usually provided on a flywheel of the internal combustion engine for making an operative connection. Immediately after starting the internal combustion engine the starter motor must be disengaged in order to prevent increased wear and loud noise generation.
The making of the operative connection, which means engagement of the starter pinion at the approximate nominal rotation speed and operation of the starter motor at its nominal voltage causes a comparatively strong torque and a high wear on the crown gear and the starter motor. Especially in starters for commercial motor vehicles increased requirements, because of, for example, more-frequent-than-usual starting for predominantly shorter trips are especially difficult to satisfy with the known starters.
In starter units for buses in which the internal combustion engine is located at the rear end of the bus so that the starting process cannot be clearly heard and thus followed by the driver, additional arrangements that provide for an effective protection for the starter and the crown gear are unavoidable. A so-called electronic starting relay is used for this purpose, by which the starter can be protected from damage in many respects. After successful starting of the internal combustion engine a delay-free shut off of the starter occurs. Furthermore the electronic starter relay prevents activation of the starter when the internal combustion engine is already or still running. In the event that the internal combustion engine is still running or of a false start also a timing switch is activated which prevents a further starting attempt too soon thereafter.
Of course damage caused by incorrect or false operation of the starter relay by the driver can be prevented, but not increased wear caused by frequent operation and/or by many years of operation. In order to provide an altogether increased lifetime and to satisfy requirements due to more-than-average operation of the starter, an over-dimensioning of the electrical starter motor and/or the effective connection with the internal combustion engine cannot be avoided with the known starter devices, which increases both the manufacturing costs and also the vehicle weight.