Internal-combustion engines – Charge forming device – Fuel flow regulation between the pump and the charge-forming...
Reexamination Certificate
2001-09-27
2002-07-09
Moulis, Thomas (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel flow regulation between the pump and the charge-forming...
C123S447000
Reexamination Certificate
active
06415770
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. 2000-312093 filed on Oct. 12, 2000, including the specification, drawings and abstract is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to a high-pressure fuel supply system and method for supplying high-pressure fuel to be injected into cylinders of an internal combustion engine.
2. Description of Related Art
A high-pressure fuel supply system is known in the art, and is operable to supply high-pressure or pressurized fuel to each of fuel injectors so as to inject the fuel directly into a corresponding one of the cylinders of the internal combustion engine.
A generally known high-pressure fuel supply system includes a delivery chamber that communicates with each of fuel injectors, a high-pressure pump adapted for feeding high-pressure fuel into the delivery chamber under pressure, and a low-pressure pump that is connected to the inlet side of the high-pressure pump so as to ensure entry of the fuel into the high-pressure pump. In general, the low-pressure pump is of an electrically driven type, and is able to start delivering fuel at a rated delivery pressure at the same time that the engine is started. On the other hand, the high-pressure pump is of an engine driven type, and is not able to immediately deliver fuel under pressure in a desired manner upon a start of the engine since the pump is not sufficiently driven by the engine.
It has been proposed to raise the pressure in the delivery chamber to the rated delivery pressure (for example, 0.3 MPa) of the low-pressure pump upon a start of the engine, so as to start fuel injection. However, the rated delivery pressure is considerably lower than a target fuel pressure (for example, 12 MPa) that is to be developed in the delivery chamber during a normal operation of the engine. It is thus difficult to realize desirable fuel injection by utilizing the rated delivery pressure of the low-pressure pump.
To address the above problem, a plunger-type pressure raising mechanism as disclosed in Japanese Laid-open Patent Publication No. 5-321787 has been proposed wherein the pressure in a delivery chamber communicating with fuel injectors is raised to a set pressure upon a start of the engine, by using a plunger that operates at a delivery pressure of the low-pressure pump. Also, an accumulator-type pressure raising mechanism as disclosed in Japanese Laid-open Patent Publication No. 9-184464 has been proposed in which the pressure in a high-pressure pipe is raised to a set pressure upon a start of the engine by using an accumulator in which a fuel pressure developed during an operation of the engine has been accumulated or stored. The plunger of the plunger-type pressure raising mechanism or a diaphragm or piston of the accumulator-type pressure raising mechanism serves as a pressure wall that is caused to displace or move from an original position so as to reduce the volume of a high-pressure portion of the fuel supply system that is located downstream of the high-pressure pump. If the high-pressure pump starts being sufficiently driven by the engine, and the pressure in the high-pressure portion becomes higher than the set pressure, the pressure wall as described above is returned to the original position due to the high pressure of the fuel delivered by the high-pressure pump.
If the pressure in the high-pressure portion of the fuel supply system is raised by the pressure raising mechanism to be almost equal to the set pressure for starting, the engine exhibits good starting characteristics. However, the pressure wall of the pressure raising mechanism does not always operate normally or fulfill its intended function. If the pressure wall does not operate normally, the engine starting characteristics may deteriorate, and a large quantity of unburned fuel may be discharged from the cylinders. Since a catalyst device of an exhaust system of the engine is not sufficiently activated during a starting period of the engine, the large quantity of unburned fuel thus discharged may be released to the atmosphere without being purified or removed.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a high-pressure fuel supply system and method for supplying fuel into cylinders of an internal combustion engine, which includes a pressure raising mechanism that is adapted to raise a pressure in a high-pressure portion of the fuel supply system to a suitable set pressure upon a start of the engine, by displacing or moving a pressure wall so as to reduce the volume of the high-pressure portion, wherein the pressure wall is prevented in advance from operating in an undesirable manner.
To accomplish the above and/or other objects, there is provided according to a first aspect of the invention a high-pressure fuel supply system for an internal combustion engine, comprising: (a) a pressure raising mechanism and (b) a high-pressure pump. The pressure raising mechanism is operable to raise a pressure in a high-pressure portion of the fuel supply system to a first level during a start of the internal combustion engine. The pressure raising mechanism includes a pressure wall that is displaceable from an original position so as to reduce a volume of the high pressure portion and thereby raise the pressure in the high-pressure portion. The pressure wall is displaceable in a predetermined displacement range between the original position and a maximum displacement position. The high-pressure pump is operable to raise the pressure in the high-pressure portion of the fuel supply system to a second level that is higher than the first level after the start of the internal combustion engine. The pressure wall is returned to the original position when the pressure in the high-pressure portion is raised by the high-pressure pump to the second level. In the high-pressure fuel supply system, the pressure wall is spaced apart from the maximum displacement position of the predetermined displacement range when the pressure in the high-pressure portion that is raised by the pressure raising mechanism reaches the first level, so that the pressure wall will be able to further displace toward the maximum displacement position so as to raise the pressure in the high-pressure portion when the internal combustion engine is re-started after the engine is stopped before the pressure wall is returned to the original position. The high-pressure fuel supply system of this aspect of the invention, constructed as described above, is able to assure good engine starting characteristics.
According to a second aspect of the invention, the pressure raising mechanism is operable to raise a pressure in a high-pressure portion of the fuel supply system to a first level during a start of the internal combustion engine. The pressure raising mechanism includes a pressure wall that is displaceable from an original position so as to reduce a volume of the high-pressure portion and thereby raise the pressure in the high-pressure portion. The pressure wall is displaceable in a predetermined displacement range between the original position and a maximum displacement position. The high-pressure pump is operable to raise the pressure in the high-pressure portion of the fuel supply system to a second level that is higher than the first level after the start of the internal combustion engine. The pressure wall is returned to the original position when the pressure in the high-pressure portion is raised by the high-pressure pump to the second level. In this high-pressure fuel supply system, a controller diagnoses the pressure raising mechanism based on changes in the pressure in the high-pressure portion during an operation of the high-pressure pump. With this arrangement, the pressure raising mechanism, such as a plunger or an accumulator, can be immediately repaired upon determination of an abnormality or a failure therein, so that the pressure wall can operate normally, thus assuring good engine starting characteristics.
REF
Moulis Thomas
Oliff & Berridg,e PLC
Toyota Jidosha & Kabushiki Kaisha
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