Verifying engine cycle of an injection IC engine

Details Verifying engine cycle of an injection IC engine Verifying engine cycle of an injection IC engine

1999-10-01

2001-06-12

Yuen, Henry C. (Department: 3747)

Internal-combustion engines

Engine speed regulator

Idle speed control

C073S114220

Reexamination Certificate

active

06244248

ABSTRACT:

TECHNICAL FIELD
The present invention relates to verifying the cycle of a fuel injection internal combustion engine during running of the engine.
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 optimise 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 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 start up 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 fuel injection internal combustion engine, comprising a number of cylinders with pistons linked to a crankshaft, an exhaust conduit, one or more engine operating condition sensors including an exhaust gas sensor in an exhaust conduit, and an engine management system that includes timer means and fueling means for controlling the air/fuel ratio for at least one cylinder, the engine management system being arranged to receive from the sensors respective signals representative of engine operating conditions including exhaust gas condition, wherein the engine management system is capable of verifying the engine cycle by first altering the air/fuel ratio for one cylinder relative to the other cylinders, then timing a time delay until a signal is received from the exhaust gas sensor indicating a change in exhaust gas condition attributable to exhaust from the one cylinder and then comparing this delay against an expected delay according to the engine operating conditions.
Also according to the invention, there is provided a method of verifying the engine cycle of a four-stroke fuel injection internal combustion engine, the engine comprising a number of cylinders with pistons linked to a crankshaft, an exhaust conduit, one or more engine operating condition sensors including an exhaust gas sensor in the exhaust conduit, and an engine management system that includes timer means and fueling means for controlling the air/fuel ratio for at least one cylinder, the engine management system being arranged to receive from the sensors respective signals representative of engine operating conditions including exhaust gas condition, wherein the method comprises the steps of:
a) altering the air/fuel ratio for one cylinder relative to the other cylinders;
b) using the timer means to time a time delay until a signal is received from the exhaust gas sensor indicating a change in exhaust gas condition attributable to exhaust from the one cylinder;
d) comparing this delay against an expected delay according to the engine speed in order to verify the engine cycle.
The expected time delay will have several components: for example an injection delay and/or induction delay, a combustion delay, an exhaust gas transport delay depending of the gas flow from the cylinder exhaust port to the sensor, and a sensor response delay.
If the engine cycle is thereby verified, then the engine management system can return the air/fuel mixture of the one cylinder to the original condition. In the case of an engine which has been warmed up and which is operating under normal load condition, such operation is usually sub-stoichiometric, i.e., slightly lean, with &lgr;=0.99. Therefore, in most cases, the change in air/fuel mixture will be to a rich composition, for example with &lgr;=1.01.
If the engine cycle is not verified, then the engine management system changes the timing of fuel injection events preferably just for the one cylinder by one full cycle of the engine, i.e., by a full 360° of crankshaft rotation. If the engine management system changes the engine cycle for all cylinders, then preferably this is phased over a few engine cycles in order to minimize any engine roughness perceived by the driver. The engine management system then performs again the steps of verifying the engine cycle for the one cylinder. When the engine cycle is verified, if necessary the engine cycle for the other cylinders is corrected, and again preferably in a phased manner so that not all cylinders change cycle at the same time.
In a preferred embodiment of the invention, the exhaust sensor is an exhaust gas oxygen sensor capable of indicating a change in exhaust gas oxygen level attributable to exhaust from the one cylinder. Alternatively, another sensor could be used, for example an exhaust gas temperature sensor.
The delay component for the time taken for exhaust gas to travel to the exhaust sensor will depend on a number of factors, including exhaust gas temperature, the volume and pressure of air drawn into all the cylinders, the amount of fuel supplied to all the cylinders, and the engine speed.
One sensor may, therefore, be an engine speed sensor, wherein the delay is compared against an expected delay according to engine speed. Such a sensor may be in proximity with a toothed flywheel on the engine crankshaft to sense movement of the teeth as the flywheel rotates. The sensor may then be arranged to supply to the engine management system with a series of pulses on each revolution of the crankshaft.
If the engine is a gasoline engine with a throttle for the cylinders, means may be provided by which the throttle position is known to the engine management system. The delay can then be compared against an expected delay according to throttle position.
The means by which the throttle position is known may be a sensor that senses movement in the throttle. However, the throttle may be controlled directly by the engine management system, in which case there may be no need to sense independently the movement of the throttle.
Altering the air/fuel mixture may have some small affect on engine power output. Optionally, therefore, the engine management system alters the timing of fuel injection events for the one cylinder in order to balance the power output of the cylinder relative to the other cylinders.
Similarly, when the engine is a spark ignition engine, the engine management system may alter the timing of spark events for the one cylinder in order to balance the power output of the

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