Internal-combustion engines – Combustion chamber means having fuel injection only – Using multiple injectors or injections
Patent
1991-10-04
1993-12-21
Miller, Carl S.
Internal-combustion engines
Combustion chamber means having fuel injection only
Using multiple injectors or injections
123496, F02B 300, F02M 3704
Patent
active
052713660
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a system for injecting fuel under pressure from a fuel injection pump into a combustion chamber in an internal combustion engine, and more particularly to a fuel injection system for pressurizing fuel with an in-line fuel injection pump or a distributor fuel injection pump for a diesel engine.
BACKGROUND ART
As is well known in the art, an in-line fuel injection pump for use in a diesel engine has a structure for feeding fuel under pressure. The fuel feeding structure is described below.
The in-line fuel injection pump has a cylinder as a pump element, and the cylinder includes a plunger barrel having a spill port. A plunger is slidable in the plunger barrel and has an inclined plunger reed formed thereon. Fuel is fed under pressure during a period of time until the spill port faces the plunger reed.
Fuel that is metered by the fuel injection pump is injected by an injection nozzle. In the case where the fuel injection pump is connected to the injection nozzle by an injection pipe, the ignition of fuel may be delayed by a time lag that is caused by the flow of fuel in the injection pipe.
As the rotational speed of the engine is increased, the crankshaft angle by which the crankshaft rotates prior to the fuel ignition becomes larger, and the period of time by which the fuel ignition is delayed is so large that the fuel ignition fails to meet the best fuel combustion timing.
To prevent such a phenomenon from occurring, it has been customary to equip the camshaft of the injection pump with an injection advancing mechanism which employs a timer that operates based on centrifugal forces produced by the rotation of the engine.
The injection advancing mechanism is interposed between the crankshaft of the engine and the camshaft of the injection pump. Under centrifugal forces produced when the crankshaft rotates at high speed, a timer weight of the injection advancing mechanism is displaced radially outwardly to advance the phase of the camshaft from an initial position.
In recent years, it has been considered effective to increase the combustion efficiency of a diesel engine for the purpose of reducing the generation of harmful components in exhaust gases.
In view of such a consideration, it has been proposed to increase the pressure under which fuel is injected.
According to the above proposal, fuel is atomized into fine particles when injected under high pressure, and an increased amount of air is introduced into the mist of fine fuel particles to increase the average excess air factor of the fuel mist for thereby forming a good air-fuel mixture.
However, the proposal has suffered the problems, described below, that the present invention is to solve.
In a fuel injection system including the above injection pump, since the plunger of the injection pump is actuated by a cam, the torque required to drive the cam has to be increased for feeding the fuel under higher pressure, and the injection advancing mechanism has to be increased in size because the cam is required to be large in size.
In addition to the increased size of the injection advancing mechanism, the high-pressure feeding of the fuel also poses a problem in that the pressure under which the fuel is injected is not constant because the rotational speed of the engine varies.
Specifically, the fuel injection pressure goes higher when the rotational speed of the engine is higher, and goes lower when the rotational speed of the engine is lower.
The above phenomenon affects the atomization of the fuel. The high-pressure fuel injection is effective to generate a good air-fuel mixture for the reasons described above insofar as the engine rotates at higher speed. On the other hand, no good air-fuel mixture can be formed when the engine rotates at lower speed because the fuel injection pressure is lower.
For increasing the fuel injection ratio of the injection pump when the engine rotates at lower speed, an attempt would be made to increase the fuel injection pressure in the injection pump to achieve the fuel
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patent: 4479475 (1984-10-01), Babitzka
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patent: 4630588 (1986-12-01), Sagawa
patent: 4838232 (1989-06-01), Wich
patent: 5094216 (1992-03-01), Miyaki
patent: 5115783 (1992-05-01), Nakamura
Ishii Hiroshi
Shimada Taizo
Yamada Kiyoharu
Yokoyama Masakazu
Miller Carl S.
Mitsubishi Jidosha Engineering K.K.
Mitsubishi Jidosha K.K.
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