Methods and system for starting a vehicle

Abstract

Systems and methods for operating an internal combustion engine that may be automatically stopped and started are described. In one example, an engine is rotated in a reverse direction after an engine stop so that a belt integrated starter / generator may rotate the engine in a forward direction and utilize the inertia of the engine to rotate trough top-dead-center compression stroke, thereby starting the engine.

Description

FIELD[0001]The present description relates to methods and a system for starting an engine that includes a belt integrated starter / generator.BACKGROUND AND SUMMARY[0002]A vehicle may include a belt integrated starter / generator (BISG) to start an internal combustion engine and to charge a battery. The BISG may also provide torque to the engine when the engine is operating (e.g., combusting fuel and rotating) to boost driveline output. A BISG and its accompanying battery may be sized to provide robust engine starting when the engine stops at a position that requires a larger amount of torque to rotate the engine in a forward direction and to achieve a cranking speed that is sufficient for engine starting during cold ambient conditions. However, such a BISG may not be cost effective for some engine applications. Therefore, it may be desirable to provide a way of starting an engine with a reduced amount of torque so that a smaller BISG and battery may reliably start an engine without hav...

AI Technical Summary

Benefits of technology

[0002]A vehicle may include a belt integrated starter / generator (BISG) to start an internal combustion engine and to charge a battery. The BISG may also provide torque to the engine when the engine is operating (e.g., combusting fuel and rotating) to boost driveline output. A BISG and its accompanying battery may be sized to provide robust engine starting when the engine stops at a position that requires a larger amount of torque to rotate the engine in a forward direction and to achieve a cranking speed that is sufficient for engine starting during cold ambient conditions. However, such a BISG may not be cost effective for some engine applications. Therefore, it may be desirable to provide a way of starting an engine with a reduced amount of torque so that a smaller BISG and battery may reliably start an engine without having a large excess torque capacity.

[0004]By rotating the engine crankshaft in a reverse direction that is opposite a direction that the engine crankshaft rotates when it is combusting fuel, it may be possible to provide the technical result of starting an engine with a BISG and battery that has a lower output torque capacity. In particular, the engine crankshaft may be rotated in a reverse direction and then stopped. Once an engine start request is issued, the BISG may rotate the engine crankshaft in a forward direction to start the engine. The engine crankshaft angular rotational distance at which the engine exerts a higher compression and friction losses when the engine is rotated in the forward direction may be increased by first rotating the engine in a reverse direction. By increasing the crankshaft angular rotational distance before compression and friction losses increase when the engine is rotated, it may be possible for the engine to reach a higher cranking speed. Rotating the engine at a higher cranking speed may allow the engine's inertia to help the BISG rotate the engine trough top-dead-center compression stroke of a cylinder so that the engine may be started with less BISG torque as compared to if the engine stopped near top-dead-center compression stroke of a cylinder.

[0005]The present description may provide several advantages. In particular, the approach may improve engine starting robustness. Further, the approach may reduce system cost by enabling robust engine starting via a BISG with lower torque output capacity. In addition, the approach may be implemented in several ways that may help to reduce electrical power consumption.

Problems solved by technology

However, such a BISG may not be cost effective for some engine applications.

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