Many internal combustion engines include an electrical generator driven by the engine to generate electrical power. The power generated by the generator can be used to power some engine systems (for example, the ignition and fuel injection systems), and some systems external to the engine (for example, lights and display gauges of a vehicle powered by the engine).
A typical generator for an internal combustion engine has a rotor portion and a stator portion. The rotor includes a plurality of permanent magnets which generate a magnetic field and the stator includes one or more wire coils. The rotor is powered by the engine and is thereby caused to spin with respect to the stator. The relative motion of the magnets and the wire coils induces an electric current in the wire coils. The current can then be transmitted to the various electrical systems that are powered by the generator.
The power output of the generator is typically determined by the internal structure of the generator, such as the arrangement of the magnets and coils, as well as by the rotational speed of the rotor. Thus, although the power consumption of the various electrical systems varies over time, the amount of power produced by the generator at a particular time cannot be conveniently adjusted to correspond to the varying levels of power consumption. Thus, the generator is typically designed to always produce sufficient electrical power to meet the needs of the electrical systems under all operating conditions, to ensure their continuous operation. When the actual power consumption of the electrical systems is less than the power produced by the generator, as is usually the case, the excess power is dissipated by the generator coils, in the form of heat. Thus, cooling must be provided for the generator coils.
One method of cooling the generator coils is to spray them with a coolant, such as oil from the lubrication system of the engine. When the generator coils are in contact with the coolant, they will transfer a portion of their heat to the coolant. The coolant is subsequently transported to a heat exchanger to dissipate the heat into the environment. While this method is effective in cooling the generator coils, it suffers from a number of drawbacks. Because the rotor and stator are located in a confined space, and because the rotor is spinning, it is difficult to provide sufficient coolant to adequately cool the generator coils. In addition, particularly at low speeds, the rotation of the rotor does not adequately distribute the coolant within the generator to cool every part of the generator coils.
Therefore, there is a need for a way of cooling an electrical generator.