Measuring and testing – Simulating operating condition – Marine
Reexamination Certificate
2003-08-14
2004-10-19
Lefkowitz, Edward (Department: 2855)
Measuring and testing
Simulating operating condition
Marine
Reexamination Certificate
active
06804997
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
Not Applicable
FEDERALLY SPONSORED RESEARCH
Not Applicable
SEQUENCE LISTING
Not Applicable
BACKGROUND OF THE INVENTION
FIELD OF INVENTION
The present invention is directed to an intake air pressure sensor assembly for an internal combustion engine, and in particular, a fuel-injected engine that communicates with a controller for controlling the fuel injectors and ignition timing based on detected air pressure fluctuations.
In all fields of engine design there is emphasis on fuel economy, engine performance, and most notably, engine-out emissions. Increased emissions restrictions have led to the necessity of a more accurate fuel metering process. Fuel injection systems have emerged as an accurate way to control the air and fuel mixture in an internal combustion engine and thus keep emissions low. The trend towards fuel injection has not been without added costs, and as such has limited the applications of this technology in price sensitive markets. To apply fuel injection to an engine, one must add an engine controller, a more complex fuel system, and multiple sensors. In addition, engines often need to be redesigned to allow for the application of these control electronics. All of these components add costs and complexity to the engine system. Many manufacturers simply cannot be competitive with the added costs of fuel injection in their product line, and as such are delaying its implementation until emissions regulations mandate its use. It would be ideal to have an accurate system for controlling an internal combustion engine that is less complex and less costly to implement on current engine technology.
A four-stroke engine must rotate two complete rotations for one full engine cycle. This cycle is comprised of the intake, compression, power, and exhaust strokes. The four-stroke cycle is based on a 720° cycle, or two complete rotations of the crankshaft. In relation to four-stroke engines, the engine phase determines which half of the 720° cycle the engine is on. For example, if a four-stroke engine is “in phase” on a 720° cycle, it is considered synchronous, and the engine controller can correctly determine which stroke the engine is on. If the four-stroke engine is not synchronous, the engine controller can only determine engine position on a 360° cycle. Many systems must determine engine phase to obtain the appropriate timing on four-stroke engines. A two-stroke engine must only rotate one complete rotation for a complete engine cycle. No phase information must be obtained from this engine cycle. This will be referred to as a 360° engine cycle.
Typically, a fuel injection system utilizes a plurality of sensors on the engine to determine engine operating conditions. For example, a fuel-injected engine may be equipped with a crankshaft position sensor, cam position sensor, intake air pressure sensor, and barometric air pressure sensor in addition to other sensors. The engine controller monitors these sensory inputs to determine the appropriate ignition timing, injection timing, and quantity of fuel to be injected. It would be beneficial to reduce the number of sensors necessary to operate an engine, yet maintain accurate control. This would result in fewer components, less complexity, and reduced costs.
One of the various types of data monitored by these sensory inputs to the engine controller is the determination of the intake air pressure. This measurement process can be quite complex. This challenge can be complicated further by monitoring intake air pressure in engines with few cylinders. It is well known in the art that intake pressures fluctuate with the opening and closing of the intake valves during the intake stroke. If there is a plurality of cylinders there will be more intake events per crankshaft rotation and traditionally less overall intake air pressure fluctuations. However, if few cylinders are present as in small engines, there will be fewer intake events per crankshaft rotation and large intake air pressure fluctuations will be apparent. If the average intake pressure were to be obtained, it will not be an accurate indication of actual cylinder intake air pressures due to these fluctuations.
Air pressure sensors have been used in the calculation of intake air mass seen by reference to U.S. Pat. No. 6,453,897 to Kanno. In this approach, the intake air pressure of the engine is sampled just once per engine crankshaft revolution. It is generally understood in the art that the air pressure can be used for intake air mass calculations in fuel injection control. Kanno presents a system that has increased accuracy for measuring intake air pressure and therefore increased accuracy in obtaining intake air flow rate and desired air/fuel ratio in the engine. This example presents no applications to determining engine phase or crankshaft position through the air pressure fluctuations. Instead, this approach strictly pertains to a single air pressure measurement at a predetermined crankshaft position. The timing of this measurement is determined through the use of a crankshaft position sensor and engine control unit.
In some applications, the mass air flow rate into the engine is estimated in part by measuring the absolute pressure within the induction manifold (Manifold Absolute Pressure, or “MAP”). A mass air flow rate is the mass of air drawn into an engine over a particular period of time. Air density, or mass per unit volume, is proportional to air temperature, pressure, and humidity of the air drawn into the engine. This data is used to calculate the mass air flow rate of the engine, or mass of the incoming air. Such calculations are known as volume-density or speed density calculations.
With crankshaft position measurement, a toothed wheel is typically used in conjunction with a pickup to detect positional movement. These devices are traditionally hall effect devices or variable reluctance devices. In automotive applications, the toothed wheel consists of multiple teeth or “timing slugs” evenly spaced on the crankshaft. The number of teeth is traditionally a whole divisor of 360°. As the number of teeth is increased, resolution of the system is increased. In many applications, there is a missing tooth to indicate a predetermined position on the crankshaft itself. An automotive standard of today is known as a “36-1” pattern. This pattern evenly spaces 36 gear teeth on a ring, and has one of the 36 teeth removed to indicate a predetermined angular position. From this input, engine rpm and crankshaft position can be directly measured. Unfortunately, the crankshaft rotates twice for a complete 720° cycle in four stroke engines. A crankshaft position sensor can not indicate engine phase on a four-stroke engine because of this. The crankshaft will be in the exact same position twice during the engine cycle. Additional sensory information is required to synchronize to a 720° cycle, if the engine controller is to operate in a synchronous manner. If the crankshaft is keyed to indicate its position, it is only possible to determine engine position based on 360° cycle, or a single crankshaft rotation without additional sensory information.
Many small engines utilize a crankshaft trigger mechanism for indicating a predetermined crankshaft position for ignition purposes. With this mechanism an ignition spark is emitted every 360° of crankshaft rotation. This type of system is similar to a crankshaft position sensor with the distinction of having only a single signal indicating pulse per crankshaft revolution. A system of this nature typically is not in communication with an engine control device, but is rather part of a stand-alone ignition system. As such, there is little or no memory from one cycle to the next. These systems cannot predict engine timing for fuel injection purposes due to crankshaft acceleration and deceleration. They can however consistently trigger an ignition system at a fixed crankshaft angular position.
To determine engine phase on four stroke engines, an additional sensor is typically used in conjunction with
Lefkowitz Edward
Miller Takisha
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