Synchronization of internal combustion engine

Details Synchronization of internal combustion engine Synchronization of internal combustion engine

1999-10-01

2001-06-26

Dolinar, Andrew M. (Department: 3747)

Data processing: vehicles, navigation, and relative location

Vehicle control, guidance, operation, or indication

With indicator or control of power plant

C701S112000, C701S113000, C123S487000, C123S491000

Reexamination Certificate

active

06253145

ABSTRACT:

TECHNICAL FIELD
The present invention relates to the synchronization of an internal combustion four-stroke engine during engine startup.
BACKGROUND ART
When a fuel injection internal combustion engine is started, it is desirable to supply fuel and, for a gasoline engine, sparks to each cylinder in turn at the correct time in order to optimize performance and engine emissions. There are two common ways of determining the state of the engine cycle, either with a single sensor detecting the rotational position of the camshaft, or with a pair of sensors, one on the camshaft and the other on the crankshaft. The single sensor on the camshaft is relatively expensive, and also has to be timed in order to provide the required accuracy. The alternative approach uses cheaper sensors that do not have to be timed in, but the provision of two sensors adds manufacturing cost.
Ideally, it would be desirable to use just one sensor, which does not need to be timed in: that is, a crankshaft sensor alone. The crankshaft sensor gives an accurate signal according to the angular position of the crankshaft, but in a four-stroke engine cannot unambiguously determine engine cycle. For example, in a four-cylinder engine, the crank signal cannot discriminate between cylinder pairs
1
and
4
, or
2
and
3
.
Patent documents U.S. Pat. No. 5,425,340 and U.S. Pat. No. 5,613,473 disclose ways of addressing the problem of determining engine cycle when there is just a crankshaft sensor. In both of these disclosures, an engine management system purposely causes a misfire on one or more cylinders. This causes a drop in engine power immediately following the misfire, and a consequent small drop in engine speed, which can be detected from the crankshaft signal. Although this approach is effective in determining engine cycle, the misfiring is noticeable to the driver, who will interpret such misfires upon startup of the engine as an engine fault.
Furthermore, such misfires adversely affect the emissions performance of a motor vehicle engine. Although such misfires during cranking of the engine may not affect rated emissions performance in the case where this performance is measured during steady running of the engine, such misfires will affect the rated performance for stricter regulations including the period from when an engine is first started.
DISCLOSURE OF INVENTION
It is an object of the present invention to provide a more convenient way of synchronizing an internal combustion engine upon startup of the engine. According to the invention, there is provided a four-stoke internal combustion engine, comprising a number of cylinders with pistons linked to a crankshaft, means to provide a series of pulses on each cycle of the engine, and an engine management system that includes: a memory; and means to determine the engine cycle after the engine is cranked; characterized in that the engine management system comprises means to count thereafter the series of pulses until the engine comes to a stop in order to determine the engine cycle of the engine when subsequently stopped so that data representative of the engine cycle may be stored in the memory.
The means to determine the engine cycle after the engine is cranked may include a means to determine the engine cycle during running of the engine, for example, some time after cranking of the engine.
The means to determine the engine cycle after the engine is cranked may also include a memory that stores data representative of the engine cycle of the engine before the engine was cranked.
The means to measure the rotation of the engine may include a sensor that measures the revolution of the crankshaft, said sensor producing as an output the series of pulses on each revolution of the crankshaft.
The memory is preferably a non-volatile memory such as an EEPROM or flash memory, and may optionally be integrated with the engine management system.
The sensor may be arranged to measure directly the rotation of the crankshaft. For example, the crankshaft may have a toothed wheel, the sensor being arranged to detect the passage of said teeth as the crankshaft rotates.
The sensor may be any type of sensor, preferably a non-contact type of sensor such as a Hall Effect sensor or a variable reluctance sensor. A Hall Effect sensor has the benefit of producing an output, even as the speed of the crankshaft reaches zero. Variable reluctance sensors are less expensive but provide an output signal with an amplitude that varies in direct proportion with the crankshaft rotational speed. In this latter case, the means to count the pulses includes predictive means to extrapolate from the falling frequency and amplitude of the pulses the engine cycle for the last pulse.
The predictive means may be an empirically derived algorithm, or a lookup table, constructed according to the measured performance of the sensor arrangement.
It is, therefore, possible to compensate for the variability in pulse amplitude such that the final resting position of the crankshaft may be determined, for example, to an accuracy defined by the number of pulses output per revolution of the crankshaft.
In a preferred embodiment of the invention, the means to count pulses as the engine comes to a stop determines in addition to the engine cycle, the engine angle of the stopped engine, so that data representative of the stopped engine angle may be stored in the memory.
When the engine is started, the engine management system may use the series of pulses, for example pulses output from the crankshaft sensor, and said data stored in the memory, to synchronize fuel delivery to the cylinders. In the case of a direct or indirect injection engine, the synchronization may include timing of fuel injection events. Similarly, for a spark ignition engine, the synchronization may include cylinder spark events. Synchronization may therefore be achieved rapidly upon startup of the engine, so improving engine performance including emissions performance as the engine is started.
Also according to the invention, there is provided a method of synchronizing a four-stoke internal combustion engine, the engine comprising a number of cylinders with pistons linked to a crankshaft, means to provide a series of pulses on each cycle of the engine, and an engine management system that includes: a memory; means to determine the engine cycle after the engine is cranked; and means to count the series of pulses; comprising the steps of:
a) providing a series of pulses on each cycle of the engine;
b) supplying the series of pulses to the engine management system; and
c) determining the engine cycle; characterized in that the method comprises the steps of:
d) thereafter counting the series of pulses until the engine comes to a stop in order to determine the engine cycle of the subsequently stopped engine; and then
e) storing data representative of the engine cycle of the stopped engine in the memory.
Step c) may involve determining the engine cycle during running of the engine, for example some time after cranking of the engine.
Step c) may also involve storing in memory data representative of the engine cycle of the engine before the engine was cranked.
Optionally, step c) may include determining the engine angle of the stopped engine, in which case step e) will include storing in the memory data representative of the engine angle of the stopped engine.
When the engine is to be subsequently started, the data previously stored in memory may be recalled. Then when the engine is cranked, the engine management system can thereafter track or count the series of pulses in order to keep track of the engine cycle. This permits the fuel delivery to the cylinders to be synchronized according to the recalled data and the output from the means to provide a series of pulses.
Optionally, in the case where the engine is a spark ignition engine, cylinder spark events may be synchronized according to the recalled data and the means to provide the series of pulses.


REFERENCES:
patent: 5425340 (1995-06-01), Petitbon et al.
patent: 5604304 (1997-02-01), Kokubo et al.

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