Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2001-09-25
2003-09-23
Vo, Hieu T. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S490000, C123S491000, C123S456000, C123S459000
Reexamination Certificate
active
06622702
ABSTRACT:
CROSS REFERENCES TO RELATED APPLICATIONS
This application corresponds to Japanese Patent Application No. 2000-070310 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, which is stored in common rails under accumulated pressure, from injectors.
2. Description of the Related Art
Conventionally, with regard to engine fuel injection, in attempting to perform fuel injection at higher pressure, common rail fuel injection systems are known as a method of providing optimum control, in accordance with the running state of the engine, of conditions, for the injection of fuel from injectors, such as the timing of fuel injection and the amount of fuel injected. A common rail fuel injection system is one in which working fluid, to which a predetermined pressure has been applied by a fuel supply pump, is stored under accumulated pressure in common rails, and in which, based on the action of pressure of this working fluid, fuel is injected, into a combustion chamber from injectors respectively arranged in a plurality of cylinders, under optimum fuel injection conditions such as the fuel injection amount and the duration of the fuel injection, these conditions being determined by a controller in accordance with the engine running state. Each of these injectors comprises a control valve for performing control such that fuel supplied via a fuel supply pipe is allowed to pass or blocked.
When the working fluid is the fuel itself, the common rails store the fuel under accumulated pressure, and inside a fuel flow pass, which runs from the common rails, via a fuel supply pipe, to nozzle holes, which are formed in the front ends of the injectors, is continually subjected to the action of a fuel pressure that is suited to the injection pressure. In order to perform fuel injection over only a predetermined duration, the injectors comprise a open/close valve that constitutes a control valve and opens and closes the fuel flow pass, this open/close valve being actuated by an actuator, such as an electromagnetic actuator, or an actuator with magnetic bending elements. The controller controls the common rail pressure and the actuation of the injector open/close valves such that the pressurized fuel in the injectors is injected under fuel injection conditions that are optimum for the engine running state.
In a common rail fuel injection device, the open/close valves are actuated by actuators by means of electrical signals output by the controller. With regard to the fuel injection quantity, the controller determines a target Fuel injection quantity in accordance with the engine running state, and controls the duration over which the injector actuators are actuated in accordance with this target fuel injection quantity. When the actuators used are electromagnetic valves, the duration over which the electromagnetic valves are open, in other words, the pulse duration of a command pulse, for fuel injection, which is output by the controller to the electromagnetic valves, is controlled. However, the quantity of fuel injected in any given single period, in other words, the fuel injection rate, depends not only on the pulse duration but also on the fuel pressure of the common rails. Consequently, the pulse duration is elected in accordance with the target fuel injection quantity and this common rail fuel pressure.
An overview of a common rail fuel injection system, in which a common rail type fuel injection system is applied, is shown in FIG.
3
. The common rail fuel injection system
1
shown in
FIG. 3
is a system for a six-cylinder engine. The fuel in a fuel tank
4
passes through a pre-filter
5
, and a filter
6
, which comprises a circulation valve and a water separator, whereupon the fuel is supplied via a fuel pipe
7
to a fuel supply pump
8
that is, for example, a plunger-type variable-capacity high-pressure pump. Fuel-supply pump
8
, which is driven by the output of the engine, raises the fuel pressure to a required predetermined pressure, and supplies the fuel to common rails
2
via fuel pipe
9
and pressure-control valve
11
. A pressure control valve
11
, for maintaining the fuel pressure in common rails
2
at a predetermined pressure, is disposed at the outlet of fuel supply pump
8
and before common rails
2
. Fuel, which is relieved from fuel supply pump
8
, returns to fuel tank
4
via return pipe
12
. Fuel in common rails
2
is supplied to a plurality (six) of injectors
10
(only one is shown) via a fuel supply pipe
3
. Of the fuel supplied from fuel supply pipe
3
to injectors
10
, the portion that is not used in the injection to the combustion chamber, and the portion that is relieved using pressure control valve
11
, returns to fuel tank
4
via return pipes
13
,
14
.
Signals are input to controller
15
, which is an electronic control unit, from a variety of sensors
16
that serve to detect the engine running state, such as an engine cylinder discrimination sensor, a crank angle sensor for detecting the engine rotation speed Ne and top dead center (TDC), an accelerator opening sensor for detecting the accelerator pedal depression amount Ac, a water temperature sensor for detecting the cooling water temperature, and an intake pipe pressure sensor for detecting the pressure in an intake pipe. The pressure of common rails
2
is provided by pressure sensors
18
, which are provided in pressure control valve
11
. A detection signal for fuel pressure Pr in common rails
2
(herein below termed “common rail pressure”), which is detected by pressure sensors
18
, is also input to controller
15
. Based on these signals, controller
15
controls conditions of the fuel injection by injector
10
such as the period of the fuel injection (fuel start time and duration) and the injection quantity, and so forth, of injector
10
, such that the engine output is optimized to suit the running state of the engine. Fuel inside common rails
2
is consumed by injecting fuel from injectors
10
, and the fuel pressure in the common rails is therefore lowered. However, controller
15
performs control such that common rail pressure Pr becomes constant or is the fuel injection pressure required according to the engine running state, by controlling the fuel pressure supplied from fuel supply pump
8
under pressurized conditions by means of a control portion
19
of pressure control valve
11
.
FIG. 4
is a vertical cross-sectional schematic view showing one example of an injector that may be used in a common rail fuel injection system. This injector
10
is mounted in a hermetically sealed fashion by means of a seal member in a hole portion provided in a base of a cylinder head, or the like, of which illustration has been omitted from the diagram. Fuel supply pipe
3
is connected to an upper side portion of injector
10
, and fuel supply pipe
3
constitutes, along with fuel passages
21
,
22
, which are formed inside injector
10
proper, a fuel flow pass. With nozzle holes
25
being formed in the front end portion of injector
10
, fuel, which is supplied via the fuel flow pass, passes along the passage in the vicinity of a fuel reservoir
23
and a needle valve
24
, and, when nozzle holes
25
open when needle valve
24
is lifted, fuel is injected into the combustion chamber from nozzle holes
25
.
A pressure-control-chamber type needle-valve lift mechanism is provided in injector
10
in order to control the lifting of needle valve
24
. An electromagnetic actuator
26
is provided for driving an electromagnetic valve at the uppermost portion of injector
10
. A control current, which corresponds to a command pulse from controller
15
, is sent via a signal wire
27
to solenoids
28
of electromagnetic actuator
26
. When solenoids
28
are excited, an armature
29
rises, and a switch valve
32
opens, this switch valve being provided at the end portion of discharge path
31
. Consequently, fu
Ohishi Kazutaka
Yomogida Koichiro
Huynh Hai H
Isuzu Motors Limited
McCormick Paulding & Huber LLP
Vo Hieu T.
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