Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2002-06-27
2004-04-06
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
Reexamination Certificate
active
06715470
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based on Application No. 2002-002322, filed in Japan on Jan. 9, 2002, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel supply device for an internal combustion engine, and more particularly to a fuel supply device for an internal combustion engine, which supplies fuel while controlling the pressure of the fuel supplied to the internal combustion engine.
2. Description of the Related Art
An example of a conventional fuel supply device for an internal combustion engine is disclosed in Japanese Patent Application Laid-open No. 11-324757. In this fuel supply device, a target fuel pressure and the detected fuel pressure are used to set a feedback quantity, and the pump discharge quantity which corresponds to the target fuel pressure change amount, and the fuel quantity that is supplied to the engine by a fuel injection valve, are set as a feed forward quantity.
Explanation will now be made of the construction and operation of the conventional fuel supply device, using
FIG. 1. A
feed pump
102
draws fuel up from a fuel tank
101
. Fuel which has passed through a filter
103
is pressure-regulated by a regulator
104
and introduced into a high-pressure pump
105
. A piston
107
moves up and down by means of a pump cam
112
, which rotates as a single unit with a cam shaft for an air intake or exhaust valve. As a result, the volume of a pressure chamber
118
changes, and the pressurized fuel is introduced into a fuel rail
113
. The quantity of fuel introduced into the fuel rail
113
is adjusted by means of a spill valve
108
.
Electricity passing through a coil
110
causes the spill valve
108
to rise and overcomes a spring
111
, thereby opening a valve
109
. When the valve
109
opens, the pressure chamber
118
is communicated to the fuel intake side. Thus, the fuel returns to the fuel intake side without being sent to the fuel rail
113
. Therefore, the fuel is not discharged from the pump to the fuel rail
113
.
When fuel pressure inside the fuel rail
113
reaches the valve-opening pressure for a relief valve
114
, the relief valve
114
opens, and the fuel in the fuel rail
113
returns to the fuel tank
101
. A fuel pressure sensor
116
detects the fuel pressure inside the fuel rail
113
, and sends this to an ECU
117
, which thus performs feedback control and the like. The injector
115
directly supplies the pressurized fuel in the fuel rail
113
to the combustion chamber inside the internal combustion engine.
FIG. 2
shows the relationship between the pump cam
112
and a drive signal sent to the spill valve
108
. Note that the rotation angle of the pump cam
112
is measured by means of a cam sensor
120
shown in FIG.
1
. In
FIG. 2
, reference numeral
10
indicates how the diameter of the pump cam
112
changes in relation to the piston
107
, and reference numeral
11
indicates changes in the drive signal. As shown in
FIG. 2
, when the pump cam
112
is ascendant, the piston
107
moves upward and thus the volume of the pressure chamber
118
decreases, whereby the fuel is compressed. In the case where the spill valve
108
driving signal is ON, the fuel is returned to the fuel intake side. Therefore, fuel is not discharged to the fuel rail
113
. Even during the fuel discharge stroke, the spill valve
108
is closed only in the case where the drive signal to the spill valve
108
is OFF. Therefore, the discharge of the fuel to the fuel rail
113
side is effective. By controlling the spill valve ON/OFF periods, the effective pump discharge quantity is controlled to thereby control the fuel pressure.
The appropriate fuel pressure depends on the operating state of the engine. Typically, the fuel pressure varies within a range of approximately 3-12 Mpa. Depending on the fuel rail volume, for example, approximately 100 mcc of fuel is necessary to cause the fuel pressure to increase by 1 Mpa. In order to cause the fuel pressure to change by 9 Mpa, approximately 900 mcc of fuel must be introduced into the fuel rail. On the other hand, one pump cycle by a high-pressure pump can only pump out approximately 100 mcc of fuel at maximum. As such, in the case where the target fuel pressure is changed by a large amount, it is necessary to continue the maximum discharge over several cycles, in which the fuel which needed to be pumped out but could not be pumped out in one cycle is pumped out in the next cycle.
FIG. 10
explains control operations in the conventional fuel supply device shown in FIG.
1
. In
FIG. 10
, the computed target fuel pressure, which varies with each engine operating state, is read at reference numeral
1001
. At reference numeral
1002
, the target fuel pressure from the previous cycle is computed. The difference between the target fuel pressure computed at reference numeral
1001
and the previous cycle target fuel pressure computed at
1002
is computed at reference numeral
1003
as a target fuel pressure difference. Next, at reference numeral
1004
, the pump discharge quantity is computed from the target fuel pressure difference, using a predetermined correspondence map which is prepared in advance. At reference numeral
1005
, a carry over quantity
1016
from the previous cycle, which will be described later, is added to the pump discharge quantity to compute the feed forward quantity. At reference numeral
1007
, an injector injection quantity
1006
, the feed forward quantity and a feedback correction quantity are added together to produce a total pump discharge quantity
1008
. Here, the feedback quantity refers to a quantity computed at reference numeral
1014
by adding together a proportional gain
1010
and integral amounts which are given based on the difference between the target fuel pressure
1001
and actual fuel pressure
1008
. Next, at reference numeral
1015
, a pump one discharge quantity is computed from the total pump discharge quantity. At reference numeral
1018
, the pump one discharge quantity is converted into a spill valve control angle
1019
. Note that at reference numeral
1017
the pump one discharge quantity is subtracted from the total pump discharge quantity, and the remainder becomes the carry over quantity
1016
for the next cycle.
Explanation will now be made of the operations, using the flow chart shown in FIG.
9
. The target fuel pressure (FPt), which varies depending on the engine operating state, is computed at step S
801
. At step S
802
, the target fuel pressure difference (DPt) is computed based on the target fuel pressure (FPt) and the previous cycle target fuel pressure (FPt[i−1]). At step S
803
, the correspondence map is used to produce a target fuel pressure differential flow rate (Qt) from the target fuel pressure difference (DPt), for example. At step S
804
, the target fuel pressure differential flow rate (Qt) and the previous cycle's carry over quantity (Qcarry[i−1]) are added together to produce the feed forward quantity (Qff). At step S
806
, the feedback correction quantity (Qfb) is computed from the difference between the target fuel pressure (FPt) and the actual fuel pressure (FPd). At step S
807
, the feed forward quantity (Qff), the injection quantity (Qinj) and the feedback correction quantity (Qfb) are added together to computed the total pump discharge quantity (Qall). At step S
808
, the pump one discharge quantity (Qone) is computed on the basis of the total pump discharge quantity by setting a limit value therefor. At step S
809
, the pump one discharge quantity (Qone) is subtracted from the total pump discharge quantity (Qall) to produce the carry over quantity for the next cycle (Qcarry). The next cycle carry over quantity becomes the previous cycle carry over quantity (Qcarry[i−1]) when this computation process is performed in the next cycle. At step S
810
, the spill valve control angle is computed from the pump one discharge quantity to control the
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