Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2000-05-23
2002-04-30
Wolfe, Willis R. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
Reexamination Certificate
active
06378501
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for controlling the fuel pressure in a direct cylinder fuel injection engine having a high-pressure pump and a fuel pressure-varying means. More particularly, the invention relates to a device for controlling the fuel pressure in a direct cylinder fuel injection engine featuring improved response and stability in the fuel pressure control when the fuel pressure has shifted from a steady state to a transient state.
2. Prior Art
FIG. 9
is a diagram schematically illustrating the constitution of a general device for controlling the fuel pressure in a direct cylinder fuel injection engine, in which a fuel pressure regulator (fuel pressure-varying means) is controlled by feedback so that the fuel pressure in a high-pressure fuel system acquires a target fuel pressure.
In
FIG. 9
, a piston
2
is provided in a cylinder of an engine, and a combustion chamber
3
is formed over the piston
2
.
An intake pipe
4
and an exhaust pipe
5
are communicated with the combustion chamber
3
, and an intake valve
6
and an exhaust valve
7
are provided in the ports among the combustion chamber
3
, intake pipe
4
and exhaust pipe
5
. An injector
8
and a spark plug
9
are arranged in the combustion chamber
3
.
Though not diagramed, here, in the intake pipe
4
are arranged an air filter, an air flow sensor, a throttle valve, a surge tank and an intake manifold from the upstream side in order mentioned. In the exhaust pipe
5
is arranged an air-fuel ratio sensor for detecting the oxygen concentration.
The air taken in by the engine
1
is distributed into the intake pipe
4
connected to the cylinders through the air filter, air flow sensor, throttle valve and intake manifold.
Fuel such as gasoline is pressurized by a low-pressure pump
11
and is fed from a fuel tank
10
to a low-pressure conduit
12
, and is further pressurized by a high-pressure pump
13
and is fed to an injector
8
through a high-pressure conduit
14
.
The high-pressure conduit
14
is communicated with a high-pressure return conduit
14
A through the injector
8
, and the output end of the high-pressure return conduit
14
A is connected to a low-pressure return conduit
16
through a fuel pressure regulator
15
.
The fuel pressure regulator
15
increases or decreases the opening degree at the output end of the high-pressure return conduit
14
A to adjust the amount of fuel returned to the low-pressure return conduit
16
in order to adjust the real fuel pressure PF (hereinafter also simply referred to as “fuel pressure”) of the injector
8
to a target fuel pressure PFo.
The fuel pressure regulator returns part of fuel in the high-pressure conduit
14
back to the fuel tank
10
through the low-pressure return conduit
16
to lower the fuel pressure PF, and further closes the output end of the high-pressure return conduit
14
A to raise the fuel pressure PF.
When no exciting current Ri is supplied to the fuel pressure regulator
15
, the fuel pressure PF in the high-pressure conduit
14
is adjusted by the urging force of a spring (described later) in the fuel pressure regulator
15
.
The fuel of a target fuel pressure PFo supplied to the high-pressure conduit
14
is injected into the combustion chamber
3
through the injector
8
provided for each of the cylinders.
The fuel pressure sensor
17
detects the fuel pressure PF in the high-pressure conduit
14
.
The air flow sensor and the throttle sensor in the intake pipe
4
detect the flow rate of the air taken in and the throttle opening degree, and a water temperature sensor
18
detects the cooling water temperature WT of the engine
1
.
The crank angle sensor
19
forms a crank angle signal CA that represents the rotational position of the engine
1
. The air-fuel ratio sensor (not shown) in the exhaust pipe
5
forms an air-fuel ratio signal that represents the oxygen concentration in the exhaust gas.
The above-mentioned sensors send signals representing the operating conditions of the engine
1
as operating condition data to an electronic control unit (ECU)
20
.
The ECU
20
reads operating condition data from the sensors, executes a predetermined arithmetic operation, and sends control signals operated as a result of operation to the actuators.
For instance, the ECU
20
supplies an exciting current Ri to the fuel pressure regulator
15
based on the fuel pressure PF detected by the fuel pressure sensor
17
(and data of various sensors), in order to control the fuel pressure PF.
Though not diagramed here, the fuel pressure regulator
15
is provided with a low-pressure regulator in series to suppress the pulsation of fuel pressure in the high-pressure conduit
14
.
As means for varying fuel pressure in the high-pressure conduit
14
, there can be used those of various constitutions that have been known without being limited to the high-pressure pump
13
and the fuel pressure regulator
15
shown in FIG.
9
.
FIG. 10
is a vertical sectional view illustrating, in detail, the structure of the fuel pressure regulator
15
, and in which portions same as those described above (see
FIG. 9
) are denoted by the same reference numerals but are not described in detail again.
In
FIG. 10
, the fuel pressure regulator
15
includes an electromagnetic coil
151
, a magnetic circuit
152
, a plunger
153
, a valve
154
, a valve seat
155
, a through hole
156
, a communication hole
157
and a spring
158
.
Being excited by a duty control with an exciting current Ri, the electromagnetic coil
151
closes the high-pressure return conduit
14
A. The magnetic circuit
152
forms a passage of a magnetic flux generated by the excitation of the electromagnetic coil
151
.
The plunger
153
is driven in a direction in which it protrudes when the electromagnetic coil
151
is excited. The valve
154
is integrally formed at an end of the plunger
153
. The valve seat
155
is arranged being opposed to the valve
154
.
The through hole
156
is formed in the center of the valve seat
155
, and an output end of the high-pressure return conduit
14
A is connected to the through hole
156
.
The communication hole
157
penetrates through the side surface neighboring the through hole
156
. The low-pressure return conduit
16
is connected to the communication hole
157
.
The spring
158
urges the plunger
153
in a direction in which it protrudes.
Next, concrete steps of adjusting the fuel pressure PF by the fuel pressure regulator
15
shown in
FIG. 10
will be described with reference to
FIGS. 11 and 12
.
FIG. 11
shows basic characteristics of the fuel pressure regulator
15
, and
FIG. 12
shows basic characteristics of the blow-out amount of the high-pressure pump
13
.
In
FIG. 11
, the abscissa represents the duty value (current value) of the exciting current Ri, the ordinate represents the fuel pressure PF, and the fuel pressure PF increases with an increase in the exciting current Ri (current value) starting from the adjusted pressure RS due to the urging force of the spring
158
.
In
FIG. 12
, the abscissa represents the rotational speed of the high-pressure pump
13
corresponding to the engine rotational speed Ne, the ordinate represents the amount of fuel QF blown out from the high-pressure pump
13
, and the blow-out amount of fuel QF increases with an increase in the engine rotational speed Ne (pump rotational speed).
In
FIG. 10
, when the exciting current Ri is supplied from the ECU
20
, the electromagnetic coil
151
in the fuel pressure regulator
15
controls the sucking force of the plunger
153
through the magnetic circuit
152
using the magnetic flux generated by the exciting current Ri.
In this case, the valve
154
is pushed onto the valve seat
155
with a maximum force when the exciting current Ri is maximum (when the duty is maximum).
The fuel pressure PF in the high-pressure return conduit
14
A (high-pressure conduit
14
) is controlled by the amount of fuel that flows from the output end of the high-pressure return conduit
14
A into the
Enoki Keiichi
Hisato Hiromichi
Kitao Takeshi
Ono Takahiko
Mitsubishi Denki & Kabushiki Kaisha
Sughrue & Mion, PLLC
Wolfe Willis R.
LandOfFree
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