Internal-combustion engines – Combustion chamber means having fuel injection only – Using multiple injectors or injections
Reexamination Certificate
2001-11-14
2003-07-01
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Combustion chamber means having fuel injection only
Using multiple injectors or injections
C123S446000, C123S478000
Reexamination Certificate
active
06584953
ABSTRACT:
CROSS REFERENCES TO RELATED APPLICATIONS
This application corresponds to Japanese Patent Application No. 2000-069990 filed in JPO on Mar. 14, 2000, the entire disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a common rail fuel injection device for injecting fuel accumulated in a pressurized state in a common rail, via injectors, and more particularly, to a common rail fuel injection device for performing fuel injection via injectors, by means of a main injection, and a pilot injection whereby a small quantity of fuel is injected prior to the main injection.
2. Description of the Related Art
In the prior art, a common rail fuel injection system is known as a method for obtaining a higher fuel injection pressure in a fuel injection system for an engine, by controlling the injection conditions of fuel from injectors, such as the injection timing and injection quantity, to optimal conditions corresponding to the operating state of the engine. A common rail fuel injection system is a system wherein an operating fluid raised to a prescribed pressure by means of a fuel supply pump, is accumulated in a pressurized state inside a common rail, and based on the action of the pressure of the operating fluid, fuel is injected from injectors disposed respectively with respect to a plurality of cylinders, into combustion chambers thereof, under optimal fuel injection conditions, such as fuel injection quantity and fuel injection time, and the like, as determined by a controller in accordance with the operating state of the engine. Each injector is provided with a control valve to perform control for passing or blocking fuel supplied via a fuel supply pipe.
If the fuel itself forms the operating fluid, then the common rail accumulates fuel in a pressurized state therein, and a fuel pressure corresponding to the injection pressure is exerted constantly in the fuel supply path formed from the common rail, via fuel supply pipes, to nozzles formed at the front end of each injector. In order that each injector injects fuel only at a prescribed time, control valves are provided which open and shut the fuel supply path by being driven by an actuator, such as an electromagnetic actuator, magnetic distortion element, or the like. The controller controls the pressure in the common rail and the operation of each injector's control valve, in such a manner that the pressurized fuel is injected by each injector at optimal injection conditions with respect to the operating state of the engine.
In a common rail fuel injection device, the control valves are operated by actuators on the basis of electrical signals output by the controller. However, there is a delay time caused by response delay, from the time at which current is applied to the actuator due to the output signal from the controller, until the time at which the control valve actually performs an opening/shutting operation. Therefore, the target fuel injection time is determined based on the operating state of the engine, and the aforementioned response delay is taken into consideration when determining the drive time of the control valve to the injector, in other words, the output timing of the injection pulse constituting a command pulse from the controller, based on the target fuel injection time.
FIG. 5
shows an overview of a common rail fuel injection system in which a common rail fuel injection device is applied. The common rail fuel injection system
1
illustrated in
FIG. 5
is a system for a six-cylinder engine, wherein fuel in a fuel tank
4
is passed through a pre-filter
5
and a filter
6
comprising a circulating valve and demoisturizer, whereupon it travels along a fuel pipe
7
and is supplied to a fuel supply pump
8
, which is, for example, a variable capacity high-pressure plunger-type pump. The fuel supply pump
8
is driven by the engine output, and it raised the fuel to the prescribed pressure required, and supplies it to a common rail
2
, via a fuel valve
9
and pressure control valve
11
. Before the common rail
2
on the output side of the fuel supply pump
8
, a pressure control valve
11
is provided in order to maintain the fuel pressure in the common rail
2
at a prescribed pressure. Fuel relieved from the fuel supply pump
8
is returned via a return pipe
12
to the fuel tank
4
. The fuel inside the common rail
2
is supplied to a plurality of (six) injectors
10
(only one injector is depicted here) via a fuel supply pipe
3
. Of the fuel that is supplied to the injector
10
via the fuel supply pipe
3
, that fuel which is not consumed in the injection into the combustion chamber, and the fuel that is relieved by the pressure control valve
11
is returned to the fuel tank
4
by means of return pipes
13
and
14
.
The controller
15
is an electronic control unit, which inputs signals from various sensors
16
in order to detect the operating state of the engine, such as, an engine cylinder discriminating sensor, a crank angle sensor for detecting the engine revolutions Ne and the top dead centre (TDC), an accelerator opening sensor for detecting the accelerator pedal operation amount Ac, a water temperature sensor for detecting the temperature of the cooling water, an inlet tube pressure sensor for detecting the internal pressure of the inlet tube, and the like. The pressure of the common rail
2
is detected by a pressure sensor
18
provided at the pressure control valve
11
, and a detection signal for the fuel pressure Pr inside the common rail
2
(hereinafter, called fuel pressure in the common rail,) as detected by the pressure sensor
18
is also input to the controller
15
. Based on these signals, the controller
15
controls the injection conditions for the fuel from the injectors
10
, in other words, the fuel injection time (injection start timing and duration), injection quantity, and the like, in such a manner that the engine output is optimally suited to the operating state thereof. The fuel in the common rail
2
is consumed by being injected from the injectors
10
, and hence the fuel pressure inside the common rail falls, but the controller
15
controls the pressure of the fuel supplied from the fuel supply pump
8
by means of the control section
19
of the pressure control valve
11
, in such a manner that the fuel pressure in the common rail Pr remains uniform, or become equal to the fuel injection pressure required according to the operating state of the engine.
FIG. 6
is an approximate longitudinal diagram showing one example of an injector used in a common rail fuel injection system. The injector
10
is installed in a sealed state by means of a sealing member in a cavity portion provided in the base of the cylinder head, or the like (not illustrated). The fuel supply pipe
3
is connected to the upper side portion of the injector
10
, and this fuel supply pipe
3
forms a fuel supply path in conjunction with fuel passages
21
,
22
formed inside the injector
10
proper. Nozzles
25
are formed at the front end portion of the injector
10
, and fuel supplied via the fuel supply path passes via a fuel reservoir
23
and needle valve
24
and is injected into the combustion chamber from the nozzles
25
, which open when the needle valve
24
lifts.
In order to control the lifting of the needle valve
24
, the injector
10
is provided with a needle lifting mechanism based on a pressure control chamber. An electromagnetic actuator
26
driving an electromagnetic valve is provided on the uppermost portion of the injector
10
, and a control current corresponding to a command pulse from the controller
15
is supplied via a signal line
27
to the solenoid
28
of the electromagnetic actuator
26
. When the solenoid
28
is excited, an armature
29
rises up and opens a control valve
32
provided at the end of the fuel path
31
, thereby releasing the pressure of the fuel supplied from the fuel supply path to the pressure control chamber
30
, by means of the fuel passage
31
.
Argenbright Tony M.
Isuzu Motors Limited
McCormick Paulding & Huber LLP
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