Internal-combustion engines – Combustion chamber means having fuel injection only
Reexamination Certificate
2001-09-28
2003-04-22
Vo, Hieu T. (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
C123S090110, C123S295000
Reexamination Certificate
active
06550444
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an auto-ignition type internal combustion engine and contrail method particularly to an apparatus and a method of controlling ignition timing in an auto-ignition type internal combustion engine.
Japanese Patent Application Laid-Open No. 7-332140 and Japanese Patent Application Laid-Open No. 7-150948 propose a gasoline engine in which a premixed mixture in a combustion chamber is automatically ignited by increasing the compression ratio higher than a common compression ratio without using any spark plug.
This auto-ignition type engine has merit in that its pumping loss is so little as to improve its efficiency at low load operation because the engine has no throttle valve which is used in a common gasoline engine in order to control a quantity of intake air. The load controlling method at that time is performed by controlling the fuel injecting rate similar to that in a diesel engine, and the ignition of the mixture is performed by the auto-ignition caused by the effect of the compression ratio set to a value higher than the common value.
In a case of spark plug ignition, NO
x
is apt to be exhausted because a high temperature portion is locally formed. However, the auto-ignition takes place at many points not just a single point. As a result, the mixture is ignited and burned at many points as if many spark plugs were arranged in the combustion chamber, and the engine has accordingly an advantage that the NO exhaust concentration can be lowered to several ppm because no local high temperature portion cannot be formed in the combustion chamber.
In the above referent embodiment, it is described timing to inject fuel to the intake port is set from 10 degrees before timing of closing the intake valve to 110 degrees before timing of opening the intake valve, amount of fuel directly injected into the combustion chamber is set to 15 to 25% of the total amount of the injected fuel, and the injecting timing is set to 8 to 30 degrees before the top dead center.
The compression-ignition internal combustion engine described above is expected as a next generation vehicle engine which can satisfy low fuel consumption and low emission at one time. However, the intake air flow rate and the fuel flow rate are changed every cycle. The change in air flow rate is caused by surge inside the intake pipe and difference in intake air flow rate distribution among the cylinders. In the intake port injection engine, the change in fuel flow rate is caused by the fact that fuel attached onto the wall surface inside the intake port is supplied to the combustion chamber in delaying over several combustion cycles.
Therefore, the problem of the change in fuel flow rate can be solved to a certain degree by directly injecting the fuel into the cylinder. However, it is impossible to eliminate, for example, the change in air flow rate to each of the cylinders due to difference in length of the intake pipe or the change in air flow rate due to difference in shape of the intake passage.
In the compression-ignition engine, the ignition phenomenon is caused by increase in temperature and pressure of the air or the mixture compressed by the engine, and the occurrence timing of the ignition phenomenon must be singly determined to a value when the temperature, the pressure and the air-to-fuel ratio are kept constant. However, the ignition timing is changed every cycle due to the cyclic changes in air flow rate and fuel flow rate described above. The change in ignition timing relates to change in generated torque to causes ands vibration of the engine.
Accordingly, it is preferable that the ignition timing is kept constant or the changing width of the ignition timing is kept small when the operating condition is constant. Further, a non-throttle engine is apt to be affected by an effect of pressure change due to atmospheric pressure change or altitude difference. Therefore, in the compression-ignition internal combustion engine, it is insufficient from the viewpoint of controlling the ignition timing to control only the injection timing and the injection flow rate of fuel.
SUMMARY OF THE INVENTION
In order to solve the above-mentioned problem, a first object of the present invention is to improve a compression-ignition internal combustion engine by properly controlling auto-ignition timing of the engine.
In order to attain the above-mentioned object, a compression-ignition internal combustion engine in accordance with the present invention comprises a valve control means for controlling opening timing and/or closing timing of the intake valve and/or the exhaust valve.
By controlling opening timing and/or closing timing of valves, it is possible to control the compression pressure corresponding to an operating condition of the engine, and to obtain an appropriate auto-ignition timing because the auto-ignition timing can be controlled corresponding to the operating condition of the engine.
Since a crank angle corresponding to combustion time period becomes large when a rotating speed of the engine is high, it is also important to control opening timing and/or closing timing of the intake valve and/or the exhaust vale corresponding to the rotating speed of the engine so that the auto-ignition occurs at an appropriate timing.
Since combustion speed becomes slow when an air-to-fuel ratio is increased, it is important to control opening timing and/or closing timing of the intake valve and/or the exhaust vale corresponding to the air-to-fuel ratio so that the auto-ignition occurs at an appropriate timing.
It is practical that the control of auto-ignition timing is performed so as to minimize a difference between an actual ignition timing and a target ignition timing by comparing them.
When the air-to-fuel ratio becomes larger than a preset value or when the rotating speed of the engine becomes higher than a preset value, an appropriate combustion can be attained by controlling the opening timing and/or the closing timing of the intake valve and/or the exhaust valve so that the auto-ignition timing or the maximum point of the cylinder pressure falls within 20 degrees after the top dead center.
REFERENCES:
patent: 4009695 (1977-03-01), Ule
patent: 4111177 (1978-09-01), Regueiro
patent: 4633403 (1986-12-01), Asmus
patent: 6155217 (2000-12-01), Shiraishi et al.
patent: 6371065 (2002-04-01), Shiraishi et al.
patent: 4-8847 (1992-01-01), None
patent: 11-257108 (1999-09-01), None
Nakayama Yoko
Nogi Toshiharu
Ohsuga Minoru
Shiraishi Takuya
Tokuyasu Noboru
Crowell & Moring LLP
Vo Hieu T.
LandOfFree
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