Methods and systems for selective engine starting

摘要

Systems and methods for starting an engine are described. In one example, engine cranking speed for an engine of a hybrid vehicle is adjusted in response to operating conditions. The engine cranking speed may be reduced when capability of a battery that supplies power to rotate the engine is less than an amount of power to rotate the engine at a higher speed.

主权项

1. A method for starting an engine, comprising:
determining a state of charge of a battery cell with a state of charge less than other battery cells in a battery; determining a battery power capability based on the state of charge of the battery cell with the state of charge less than other battery cells in the battery, a battery cell lower voltage limit, two internal battery resistance values, and a constant e with an exponent, the exponent based on an internal capacitance of the battery cell; determining an efficiency of a motor; looking up an engine cranking torque via indexing a function via an engine temperature; determining an engine cranking power via multiplying the engine cranking torque with engine cranking speed; multiplying the battery power capability with the efficiency of the motor and comparing a result of the multiplication to a power to crank the engine at a desired engine speed; adjusting the engine cranking speed in response to the comparison; and cranking the engine at the adjusted cranking speed.