Internal-combustion engines – Charge forming device – With fuel pump
Reexamination Certificate
2000-08-04
2002-01-08
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
With fuel pump
C123S456000
Reexamination Certificate
active
06336445
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. 11-256164 filed on Sep. 9, 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 fuel supplying apparatus and method for an internal combustion engine.
2. Description of the Related Art
In internal combustion engines, automotive engines and the like, an engine that directly injects fuel into a combustion chamber for the purpose of improving fuel economy and the like has recently been commercialized. As such, a high pressure of fuel supplied to the fuel injection valve is required in order to inject fuel from the fuel injection valve into the combustion chamber and thus overcome the high pressure in the combustion chamber. Therefore, fuel fed from a fuel tank by a feed pump is pressurized by a high-pressure fuel pump and delivered to the fuel injection valve. A known fuel supplying apparatus having a high-pressure fuel pump as mentioned above is described in Japanese Patent Application Laid-Open Nos. 10-76618 and 10-176619. A fuel supplying apparatus described in these laid-open patent applications is shown in FIG.
9
.
As shown in
FIG. 9
, a high-pressure fuel pump
101
of the fuel supplying apparatus has a plunger
103
that is reciprocated within 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
communicating with a feed pump
106
for feeding fuel from a fuel tank
105
, a spill passage
108
that lets fuel out of the pressurizing chamber
104
to return fuel to the fuel tank
105
, and a delivery passage
110
for delivering pressurized fuel from the pressurizing chamber
104
toward a fuel injection valve
109
. The high-pressure fuel pump
101
has a spill valve
111
that opens and closes the communication of the spill passage
108
and the suction passage
107
with the pressurizing chamber
104
.
When the plunger
103
is moved in such a direction as to increase the capacity of the pressurizing chamber
104
(downward in the drawing) while the spill valve
111
is in an open state, that is, when the high-pressure fuel pump
101
is in the suction stroke, fuel is drawn from the suction passage
107
into the pressurizing chamber
104
. When the spill valve
111
is closed during a movement of the plunger
103
in the pressurizing chamber
104
-capacity reducing direction (upward in the drawing), that is, during the fuel ejection stroke of the high-pressure fuel pump
101
, the communication of the suction passage
107
and the spill passage
108
with the pressurizing chamber
104
is closed, so that fuel is delivered from the pressurizing chamber
104
toward the fuel injection valve
109
via the delivery passage
110
.
In this high-pressure fuel pump
101
, fuel is delivered toward the fuel injection valve
109
only during the closed valve period of the spill valve
111
during the ejection stroke of the pump, the amount of fuel delivered is adjusted by adjusting the closed period of the spill valve
111
through control of the valve closure start timing of the spill valve
111
. That is, the amount of fuel delivered is increased by increasing the closed valve period of the spill valve
111
, and is reduced by reducing the closed valve period. When the amount of fuel delivered is adjusted, the pressure of fuel delivered to the fuel injection valve
109
(fuel pressure) is controlled to a target value that is determined in accordance with the operation state of the engine, so that the amount of fuel injected from the fuel injection valve
109
, which is determined by the fuel pressure and the fuel injection duration, becomes equal to a proper amount.
Thus, since fuel fed from the feed pump
106
is pressurized by the high-pressure fuel pump
101
and the pressurized fuel is delivered toward the fuel injection valve
109
, the engine is able to precisely perform fuel injection.
The amount of fuel delivered from the high-pressure fuel pump
101
is affected by the cam speed (i.e., the amount of movement of the plunger
103
per unit angle rotation of the cam
100
) that occurs when the closure of the spill valve
111
starts. The cam speed at the start of closure of the spill valve
111
does not necessarily change at a constant changing rate (with a constant gradient) with respect to changes of the start timing of closure of the spill valve
111
. More specifically, the changing rate (gradient) of the cam speed at the start of closure of the spill valve
111
with respect to changes in the start timing of closure of the spill valve
111
greatly fluctuates based on the phase of the cam. If the amount of fuel delivered is adjusted by changing the start timing of closure of the spill valve
111
so as to control the fuel pressure to a target value, the change of the valve closure start timing does not readily adjust the amount of fuel delivered (fuel delivery amount) in an adequate fashion, thus resulting in considerable fluctuations in the fuel pressure during the control of the fuel pressure to the target value.
SUMMARY OF THE INVENTION
Accordingly, it is one object of the invention to provide a fuel supplying apparatus for an internal combustion engine that improves the controllability of the amount of fuel delivered, by appropriately adjusting the amount of fuel delivered in accordance with changes of the closure start timing of a spill valve.
A first aspect of the invention provides a fuel supplying apparatus for an internal combustion engine, having a fuel pump that draws fuel into a pressurizing chamber and delivers fuel toward a fuel injection valve of the internal combustion engine by changing a capacity of the pressurizing chamber based on a relative movement between a cylinder and a plunger caused by a rotation of a cam. The apparatus also includes a spill valve that opens and closes a communication between the pressurizing chamber and a spill passage for letting fuel out of the pressurizing chamber, wherein an amount of fuel delivered from the fuel pump toward the fuel injection valve is adjusted by controlling a closed valve period of the spill valve. The fuel supplying apparatus includes a controller that controls the closed valve period of the spill valve by changing a valve closure start timing of the spill valve so that an amount of fuel that needs to be delivered from the fuel pump for fuel injection from the fuel injection valve is provided. The apparatus is configured so that the valve closure start timing of the spill valve that provides a maximum amount of fuel that needs to be delivered occurs within a predetermined cam angle range in which an amount of the relative movement between the cylinder and the plunger occurring during rotation of the cam changes with a constant gradient with respect to a change in a phase of the cam.
Since the valve closure start timing of the spill valve that provides the maximum amount of fuel that needs to be delivered is located within the predetermined cam angle range in which the amount of the relative movement between the cylinder and the plunger occurring during rotation of the cam changes with a constant gradient with respect to a change in the phase of the cam, the cam speed at the start of closure of the spill valve changes at a substantially constant rate even when the valve closure start timing of the spill valve is changed (i.e., delayed) in order to adjust the amount of fuel delivered from the fuel pump. The cam speed at the start of closure of the spill valve affects the amount of fuel delivered from the fuel pump. However, if the cam speed at the start of closure of the spill valve changes with a constant rate as mentioned above, it is possible to properly adjust the fuel delivery amount by changing the closure start timing of the spill valve, so that the controllability of the fuel delivery amount can be improved.
In the above-described asp
Kurata Naoki
Sugiyama Masanori
Yamazaki Daichi
Miller Carl S.
Toyota Jidosha & Kabushiki Kaisha
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