Internal-combustion engines – Charge forming device – With fuel pump
Reexamination Certificate
2000-07-07
2001-11-13
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
With fuel pump
C123S299000
Reexamination Certificate
active
06314945
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. 11-214216 filed on Jul. 28, 1999 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 for a fuel pump that pumps fuel toward a fuel injection valve of an internal combustion engine.
2. Description of Related Art
Recently, there have been commercialized internal combustion engines for motor vehicles and the like in which fuel is injected directly into combustion chambers to improve fuel economy, etc. In order to inject fuel from a fuel injection valve into a combustion chamber in such an engine despite a high pressure in the combustion chamber, it is necessary to provide a high fuel pressure in the fuel injection valve. In this type of engine, therefore, fuel pumped from a fuel tank by a feed pump is pressurized by a high-pressure fuel pump, and the thus pressurized fuel is delivered to the fuel injection valve. Such high-pressure fuel pumps are described in, for example, Japanese Patent Application Laid-Open Nos. 10-176618 and 10-176619. A construction of a high-pressure fuel pump as described in these laid-open patent applications and the like is shown in FIG.
10
.
As shown in
FIG. 10
, a high-pressure fuel pump
101
, as described in the laid-open patent applications and the like, has a plunger
103
reciprocated in a cylinder
102
by rotation of a cam
100
, and a pressurizing chamber
104
defined by the cylinder
102
and the plunger
103
. Connected to the pressurizing chamber
104
are a suction passage
107
connecting to a feed pump
106
for pumping fuel from a fuel tank
105
, a spill passage
108
for leading fuel out of the pressurizing chamber
104
and returning fuel to the fuel tank
105
, and a delivery passage
110
for delivering fuel from the pressurizing chamber
104
toward a fuel injection valve
109
. The high-pressure fuel pump
101
has a spill valve
111
for establishing and discontinuing communication of the pressurizing chamber
104
with the suction passage
107
and the spill passage
108
.
When the spill valve
111
is open and the plunger
103
is moving in such a direction as to increase the capacity of the pressurizing chamber
104
(downward in FIG.
10
), that is, during the suction stroke of the high-pressure fuel pump
101
, fuel is drawn from the suction passage
107
into the pressurizing chamber
104
. When the spill valve is closed while the plunger
103
is moving in the pressurizing chamber capacity-reducing direction (upward in FIG.
10
), that is, while the high-pressure fuel pump
101
is in the ejection stroke, the communication of the pressurizing chamber
104
with the suction passage
107
and the spill passage
108
is closed, so that fuel is pumped from the pressurizing chamber
104
toward the fuel injection valve
109
via the delivery passage
110
.
Since the high-pressure fuel pump
101
delivers fuel toward the fuel injection valve
109
only when the spill valve
111
remains closed (closed valve period) during the ejection stroke, the amount of fuel delivered toward the fuel injection valve
109
can be adjusted by adjusting the closed valve period of the spill valve
111
through control of the timing of starting to close the spill valve
111
. That is, the amount of fuel delivered is increased by elongating the closed valve period of the spill valve
111
through advancement of the timing of starting to close the spill valve
111
, and the amount of fuel delivered is reduced by shortening the closed valve period of the spill valve
111
through delay of the timing of starting to close the spill valve
111
.
Since the high-pressure fuel pump
101
pressurizes fuel delivered by the feed pump
106
, and delivers pressurized fuel toward the fuel injection valve
109
, the high-pressure fuel pump
101
allows precise fuel injection even in an internal combustion engine in which fuel is injected directly into a combustion chamber.
When the spill valve
111
is about to be closed during the ejection stroke of the high-pressure fuel pump
101
, during which the capacity of the pressurizing chamber
104
reduces, fuel in the pressurizing chamber
104
tends to flow toward the spill passage
108
as well as toward the delivery passage
110
. When the spill valve
111
is closed in this situation, the closing movement of the spill valve
111
is accelerated by fuel flowing as described above, so that the impact of closure of the spill valve
111
becomes considerably great. As the impact increases, the operational noise of the spill valve
111
(noise produced by closure of the valve) increases. The operational noise of the spill valve
111
repeatedly occurs every time the spill valve
111
closes.
During normal operation of an internal combustion engine, operational noises of the engine, such as noises caused by combustion of air-fuel mixture and the like, are loud, so that the operational noises of the spill valve
111
continually occurring corresponding to continual closures of the spill valve
111
are not so loud as to annoy an occupant in the vehicle or the like. However, when the engine operational noises become small, for example, during an idling operation of the engine or the like, the continual operational noises of the spill valve
111
become relatively great, so that the annoyance caused by the operational noises become louder than can be ignored.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide a fuel pump control apparatus capable of reducing operational noises produced every time the spill valve closes.
In accordance with the invention, a fuel pump control apparatus controls a fuel pump that draws fuel into a pressurizing chamber by changing a capacity of the pressurizing chamber based on a relative movement between a plunger and a cylinder caused by a rotation of a cam and that delivers fuel toward a fuel injection valve of an internal combustion engine, and includes a spill valve that opens and closes a communication between the pressurizing chamber and a spill passage that leads fuel out of the pressurizing chamber. The fuel pump control apparatus adjusts an amount of fuel delivered from the fuel pump toward the fuel injection valve by controlling a closed valve period of the spill valve. The fuel pump control apparatus of the invention includes a controller for adjusting a number of times of performing fuel delivery from the fuel pump during a predetermined period to change a number of times of injecting fuel from the fuel injection valve per performance of the fuel delivery, by controlling the spill valve based on a load of the internal combustion engine.
Normally, during an ejection stroke of a fuel pump, as the amount of relative movement between a plunger and a cylinder with respect to a predetermined angle rotation of a cam (hereinafter, referred to as “cam speed”) increases, the force applied from fuel to a spill valve in the valve closing direction increases, so that the noise produced when the spill valve closes increases. When the position of the cam is near the top dead center during a movement of the cam from the bottom dead center to the top dead center, the cam speed decreases as the position of the cam approaches the top dead center. During an operation state of the engine during which the amount of fuel injected is relatively small, for example, during a low-load operation of the engine, the timing of starting to close the spill valve is set to a timing closer to the top dead center (i.e., a timing at which the cam speed is relatively low), so that the closed valve period of the spill valve is shortened. In this case, the noises caused by closures of the spill valve become lower than the noises caused by closures of the spill valve during a high-load operation state of the engine or the like. However, in this case, the operational noises of the engine, for example, combustion noises and the like, become further lower. Therefore,
Kurata Naoki
Sugiyama Masanori
Yamazaki Daichi
Moulis Thomas N.
Oliff & Berridg,e PLC
Toyota Jidosha & Kabushiki Kaisha
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