Internal-combustion engines – Combustion chamber means having fuel injection only – Combustible mixture stratification means
Reexamination Certificate
2001-05-08
2002-11-05
Solis, Erick (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
Combustible mixture stratification means
C123S179400
Reexamination Certificate
active
06474294
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. 2000-136046 filed on May 9, 2000 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a control apparatus and a control method of a direct injection type internal combustion engine in which fuel delivered from a fuel pump is directly injected into a combustion chamber from a fuel injection valve and the thus-formed mixture is ignited by an ignition plug. In particular, the invention relates to a direct injection type internal combustion engine control apparatus that automatically stops a direct injection type internal combustion engine if during operation of the internal combustion engine, the operating state of the engine meets an automatic stop condition, and that automatically starts operation of the engine if an automatic start condition is met.
2. Description of Related Art
A conventional direct injection type internal combustion engine is known which realizes lean burn when the engine is in a low load state, for example, during idling or the like, and thereby achieves both high output and reduced fuel consumption and also reduces emissions of carbon dioxide and the like (Japanese Patent Application Laid-Open No. 10-299543). In order to ensure that the mixture will be ignited without fail during lean burn, such a direct injection type internal combustion engine performs stratified charge combustion in which fuel is injected during the compression stroke to provide a fuel-rich mixture stratified around the ignition plug before being ignited to burn. In a case where the combustion is to be performed at a stoichiometric air-fuel ratio, the engine performs uniform combustion in which fuel is injected during the intake stroke to produce a state in which fuel is uniformly dispersed in the entire combustion chamber before being burned.
An automatic stop/start apparatus for an automotive internal combustion engine, that is, a generally-termed economy running system, is known which, for the purpose of improving fuel economy or the like, automatically stops the internal combustion engine at the time of a stop of the motor vehicle at an intersection or the like, and then automatically starts the engine by turning the starter upon an operation for starting the vehicle so that the vehicle can be pulled off (Japanese Patent Application Laid-Open No. HEI 10-47104).
Therefore, by combining this automatic stop/start apparatus with the above-described direct injection type internal combustion engine, a further fuel economy improvement can be expected.
For fuel injection during the compression stroke of a direct injection type internal combustion engine, fuel needs to be injected into a high-pressure combustion chamber. Therefore, a typical direct injection type internal combustion engine employs a high-pressure fuel pump to highly pressurize fuel and deliver high-pressure fuel toward the fuel injection valve side.
However, when such a direct injection type internal combustion engine is automatically stopped by the automatic stop/start apparatus, the high-pressure fuel pump also stops. Therefore, during the automatic stop, high-pressure fuel is not supplied to the fuel injection valve side. Even though the fuel injection valve side, including the fuel piping, is tightly closed, fuel gradually leaks. Therefore, during the automatic stop, the accumulated fuel pressure drops.
After that, at the time of an automatic start, the driving of the fuel pump is started. However, if the fuel pressure is insufficient for the compression-stroke fuel injection due to a fuel pressure decrease occurring during the automatic stop, it is inevitable to perform uniform combustion in which fuel is injected during the intake stroke during which good injection is possible even at low fuel injection pressure, until a sufficient fuel pressure is recovered. Therefore, even if the operating state of the engine other than the fuel pressure allows stratified charge combustion upon automatic start, the uniform combustion must be performed. Hence, the improvement in fuel economy and the like may become insufficient.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a direct injection type internal combustion engine control apparatus capable of maintaining a sufficient fuel pressure for the compression-stroke fuel injection for a long time even after the internal combustion engine has been stopped by an automatic stop function, and capable of increasing the frequency of performing the compression-stroke injection after the engine is automatically started. Operation and advantages obtained by the invention will be described.
A control apparatus of. a direct injection type internal combustion engine in which an air-fuel mixture formed by injecting a fuel delivered from a fuel pump, directly from a fuel injection valve into a combustion chamber, is ignited by an ignition plug, the control apparatus is provided with an automatic stop permitting unit that permits an automatic stop of the internal combustion engine if during an operation of the internal combustion engine, an operating state of the internal combustion engine meets an automatic stop condition, an automatic start permitting unit that permits an automatic start of the internal combustion engine if the operating state of the internal combustion engine meets an automatic start condition, and a fuel pressure raising unit that raises a fuel pressure on a fuel injection valve side during a first period of time_prior to the automatic stop permitted by the automatic stop permitting unit.
The fuel pressure raising unit raises the fuel pressure on the fuel injection valve side immediately prior. to the automatic stop. Therefore, after the delivery of high-pressure fuel from the fuel pump stops upon the automatic stop of the direct injection type internal combustion engine, the fuel pressure starts to gradually decrease from a higher fuel pressure, in comparison with the conventional art in which the engine is stopped with an ordinary fuel pressure state. As a result, a long time of engine stop is allowed before the fuel pressure decreases to a pressure that makes it impossible to perform appropriate fuel injection into the combustion chamber during the compression stroke.
Therefore, the possibility that a fuel pressure sufficient for the compression-stroke fuel injection will be maintained immediately after a subsequent automatic start is increased. If such a fuel pressure is maintained, the stratified charge combustion can be accomplished by performing the compression-stroke injection immediately after the subsequent automatic start provided that the internal combustion engine is in an operating state that allows the stratified charge combustion. Thus, the frequency of performing the compression-stroke injection following an automatic start can be increased, and sufficient improvements in fuel economy and the like can be achieved.
The fuel pressure raising unit raises the fuel pressure on the fuel injection valve side during the first period of time prior to the automatic stop by adjusting an amount of the fuel delivered from the fuel pump to a maximum.
Thus, by maximizing the amount of delivery from the fuel pump, the fuel pressure can be quickly brought to a sufficiently high pressure state. As a result, the frequency of performing the compression-stroke injection following an automatic start is further increased, and a fuel economy improvement and the like will become more effective.
The internal combustion engine includes a relief valve that opens and discharges the fuel from the fuel injection valve side when the fuel pressure on the fuel injection valve side reaches at least a predetermined valve opening pressure. During the first period of time prior to the automatic stop, the fuel pressure raising unit raises the fuel pressure on the fuel injection valve side so as to temporarily open the relief valve by adjusting the amount of the fuel delive
Kurata Naoki
Sugiyama Masanori
Yamazaki Daichi
Solis Erick
Toyota Jidosha & Kabushiki Kaisha
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