Patent Application
20100082219
The present disclosure relates to internal combustion engines, and more particularly, to an engine using glow plug resistance for estimating combustion temperature.
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
In theory, diesel engines and gasoline engines are quite similar. They are both internal combustion engines designed to convert the chemical energy available in fuel into mechanical energy. This mechanical energy moves pistons up and down inside cylinders. The pistons are connected to a crankshaft, and the up-and-down motion of the pistons, known as linear motion, creates the rotary motion needed to turn the wheels of a car.
Both diesel engines and gasoline engines covert fuel into energy through a series of small explosions or combustions. The major difference between diesel and gasoline is the way these explosions happen. In a gasoline engine, fuel is mixed with air, compressed by pistons and ignited by sparks from spark plugs. In a diesel engine, however, the air is compressed first, and then the fuel is injected. Because air heats up when it's compressed, the fuel ignites.
The diesel engine uses a four-stroke combustion cycle just like a gasoline engine. The four strokes are:
Some diesel engines contain a glow plug. When a diesel engine is cold, the compression process may not raise the air to a high enough temperature to ignite the fuel. The glow plug is an electrically heated element that heats the combustion chambers and raises the temperature within the combustion chamber when the engine is cold so that the engine can start. After the engine is heated up, the glow plug is no longer needed during the engine operation.
All functions in a modern engine are typically controlled by the engine control unit communicating with an elaborate set of sensors measuring everything from R.P.M. to engine coolant and oil temperatures and piston position. The engine control unit senses ambient air temperature and retards the timing of the engine in cold weather so the injector sprays the fuel at a later time. The air in the cylinder is compressed more, creating more heat, which aids in starting.
Advanced diesel engine control requires a good knowledge of combustion temperature and exhaust temperature in order to provide efficient engine controls. A temperature sensor placed within or in proximity to the combustion chamber is one known method of detecting the combustion temperature, but is an expensive solution. Further, a regression or model-based temperature model is an alternative solution but requires extensive experimental and calibration work in order to estimate the combustion temperature under a wide range of operating conditions. It is desirable in the internal combustion art to provide a reliable, inexpensive technique for determining the combustion temperature for use in engine control systems.
An internal combustion engine includes an engine block defining at least one cylinder therein. A cylinder head is attached to the engine block and defines a combustion chamber with the at least one cylinder in the engine block. A piston is disposed within the at least one cylinder. A glow plug is disposed within the combustion chamber. A resistance of the glow plug is detected and an estimated combustion temperature is determined based upon the detected resistance of the glow plug. The engine is then controlled based upon the estimated combustion temperature established from the glow plug resistance.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.
With reference to
The glow plug 24 is typically operable for a cold engine start and remains idle after the engine is warmed up. As shown in
It should be understood that other alternative circuits to the circuit 50 can be utilized for determining the resistance of the glow plug 24 in order to allow the engine control unit or other microcontroller 44 to estimate the combustion chamber temperature. The estimated combustion chamber temperature can be determined based upon a correlation map between measured glow plug resistance levels and known combustion chamber temperatures. Furthermore, an additional correlation map can be calculated to provide a correlation between the estimated combustion temperature and the exhaust temperature. The estimated combustion temperature and exhaust temperature can then be utilized by the control unit 44 for controlling the engine operation including fuel injection timing.
With the system of the present disclosure, the glow plug is used to heat up the combustion chamber during low temperature engine start-up in many diesel engines. The heater element is a temperature sensitive resistor. For a given glow plug, the temperature sensitive characteristics such as the resistance can be characterized by a look-up table. During normal operating conditions, the glow plug is not powered, but is heated by the combustion events. With a simple voltage divider circuit, the resistance of the glow plug can be obtained and, therefore, the combustion chamber temperature can be derived. With the system of the present disclosure, existing cylinder pressure sensors and exhaust temperature sensors can be eliminated with very little added cost for the divider circuitry. This system further enables individual cylinder control without significant added expenditure.
