Internal-combustion engines – Starting device – With fuel or intake air control
Reexamination Certificate
2000-08-22
2003-01-14
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Starting device
With fuel or intake air control
C123S406540
Reexamination Certificate
active
06505594
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosures of Japanese Patent Applications No. HEI 11-235947 filed on Aug. 23, 1999 and HEI 11-272804 filed on Sep. 27, 1999 including the specification, drawings and abstract are incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a control apparatus of an internal combustion engine, and more particularly, to a control apparatus of an internal combustion engine for controlling an engine speed to a target value during starting of the engine. This invention is also concerned with a method of controlling an internal combustion engine during starting of the engine.
2. Discussion of Related Art
During starting of the engine, and especially, during cold start of the engine, a combustion state is likely to deteriorate, and the engine speed may become unstable. Such deterioration in the combustion state causes problems such as deterioration in engine-starting capability and exhaust properties, and increases in vibration and noise due to the unstable engine speed after starting.
Consequently, various control apparatuses have been proposed for preventing deterioration in the combustion state during starting of the engine so as to stabilize the engine speed. One example of such control apparatuses is described in Japanese Patent Laid-Open Publication No. 62-3139. This control apparatus sets a throttle opening to a target value according to a temperature of the engine cooling water during starting of the engine (the expression “during starting of the engine” as used herein refers to the period from the start of an engine starting operation, or start of cranking, until the engine is brought into a steady idle state after complete explosion in the engine). After the complete explosion in the engine, the control apparatus sets the throttle opening so that the engine speed reaches a target value. Another example of control apparatus is described in Japanese Patent Laid-Open Publication No. 5-222997. This control apparatus feedback-controls the intake air flow rate and ignition timing of the engine so that the engine speed reaches a predetermined target value during an idling operation after the start of the engine, whereby the idle speed is maintained at a constant value.
If the engine speed is controlled only by adjusting the throttle opening during starting of the engine, as in the control apparatus of the above-mentioned Japanese Patent Laid-Open Publication No. 62-3139, deterioration of the combustion state in the engine cannot be suppressed, but, on the contrary, may be increased. In an engine having a fuel injection valve for injecting fuel into an inlet port of the engine, for example, the fuel injected during cold start of the engine may adhere to a wall of the inlet port in a liquid form, i.e., without being vaporized. Therefore, the mixture may not have a sufficient concentration of vaporized fuel, with the result that the mixture has a lean air-fuel ratio, and the engine operates in a poor combustion state. In such a case, if the throttle opening is increased, a negative pressure of an inlet pipe downstream of the throttle valve is reduced (i.e., an absolute pressure is increased). As a result, the fuel deposited on the wall becomes less likely to be vaporized, whereby the combustion state is further deteriorated. Thus, by adjusting only the throttle opening, the engine speed may not be accurately controlled to the target value during starting of the engine.
In order to solve the above-mentioned problems, a further example of control apparatus has been proposed, which controls the engine speed during starting of the engine by adjusting a throttle opening (i.e., an intake air flow rate of the engine), and switching the engine speed control through adjustment of the throttle opening to engine speed control through adjustment of the ignition timing when the combustion state in the engine is deteriorated.
The control apparatus as described just above is adapted to determine deterioration of the combustion state based on the peak engine speed, fluctuations in the engine speed, or the like, during starting of the engine. When determining that the combustion state is deteriorated, the control apparatus starts performing engine speed control by adjusting the ignition timing, or increasing the fuel injection amount, instead of adjusting the throttle opening, so as to prevent deterioration in the combustion state. In this way, deterioration in the combustion state is suppressed. It should be noted that, hereinafter, controlling the engine speed by adjusting the throttle opening will be simply referred to as “throttle valve control” or “intake air flow control”; controlling the engine speed by adjusting the ignition timing of the engine will be simply referred to as “ignition timing control”; and controlling the engine speed by increasing the fuel injection quantity will be simply referred to as “fuel injection quantity control.”
As a result of subsequent studies, it was reveled that the control apparatus as described above switches the engine speed control from the throttle valve control to the ignition timing control or injection quantity control as soon as it determines a poor combustion state in the engine, and that a favorable result cannot always be obtained in terms of maintaining an excellent exhaust properties.
For example, during starting of the engine, the ignition timing of the engine is generally delayed with respect to that during normal operations, in order to increase an exhaust temperature and quickly raise a temperature of an exhaust purifying catalyst disposed in an exhaust passage to a catalyst-activating temperature. However, if the control apparatus switches the engine speed control from the throttle valve (intake air flow rate) control to the ignition timing control, the ignition timing of the engine is advanced with respect to that during the normal starting. As a result, the exhaust temperature is reduced, and the temperature rise of the catalyst is delayed. Accordingly, if the engine speed control is performed by adjusting the ignition timing during starting of the engine, warm-up of the catalyst is delayed, and the engine is operated for a long time without sufficiently purifying the exhaust. In addition, when the engine speed control is switched from the throttle valve control to the injection quantity control, the amount of unburned components HC and CO in the exhaust is increased, and the exhaust properties are thus degraded. Therefore, in controlling the engine speed during starting of the engine, it is preferable to maintain the throttle valve control as long as possible without switching to the ignition timing or fuel injection quantity control. However, the control apparatus as described above switches to the ignition time or injection quantity control as soon as the combustion state is deteriorated. Such switching may possibly degrade the exhaust properties even if the deterioration in the combustion state could be suppressed only by the throttle valve control.
Moreover, in the control apparatus as described above, the timing of starting the engine speed control during starting of the engine is not sufficiently considered. For example, after the engine starting operation (cranking) is started, the engine speed rapidly increases when combustion is started in all cylinders of the engine. Then, the engine speed reaches a peak value, and is then reduced down to a constant value. During starting of the engine, the engine speed needs to be controlled so that it quickly settles or converges at a predetermined target value. However, with the engine speed changing as described above after the engine starting operation is started, the time required for the engine speed to be settled at the target value after the engine starting operation is started depending upon the timing of starting the engine speed control.
As described above, the control apparatus as described above switches from the intake air flow control to the ignition timing control dependin
Kanamura Masanobu
Katayama Akihiro
Ohnaka Hidemi
Watanabe Satoru
Argenbright Tony M.
Huynh Hai H.
Toyota Jidosha & Kabushiki Kaisha
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