Internal-combustion engines – Engine speed regulator – Idle speed control
Reexamination Certificate
1999-02-22
2001-04-24
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Engine speed regulator
Idle speed control
C123S325000
Reexamination Certificate
active
06220218
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an engine operation control device for controlling an engine as it shifts its operating state from a non-idling state to an idling state.
2. Description of the Prior Art
In recent years a variety of electronic control fuel injection systems for diesel engines have been developed which can control a fuel injection pressure as well as a fuel injection amount and a fuel injection timing in order to make further improvements in the engine characteristics involving output and mileage and in the exhaust gas characteristics. Such fuel injection systems for engines have an injector that includes a needle valve, which moves up or down in an injector body to perform an open-close control on injection nozzle holes, and a solenoid valve, which is supplied with a drive current for controlling a working fluid to raise or lower the needle valve. According to an operating condition of the engine, the timing, amount and pressure of the fuel injected from the injector are controlled by a controller.
Among such electronic control fuel injection systems proposed so far are a hydraulically activated system and a fuel pressure activated system. In the hydraulically activated system, an engine oil is used as the working fluid that is pressurized by a high pressure oil pump, the injector has a pressure increasing piston therein which operates on the pressure of the engine oil, and the fuel in a pressure increasing chamber is pressurized by the pressure increasing piston to lift the needle valve, which in turn allows the pressurized fuel to be injected from nozzle holes opened by the needle valve. In the fuel pressure activated system, a high-pressure fuel is used as the working fluid that is pressurized by a high-pressure fuel pump and stored in a common rail, the injector has a pressure control chamber formed in its body and controls the inflow and outflow of the high-pressure fuel into and out of the pressure control chamber to lift or lower the needle valve according to the pressure of the high-pressure fuel, thereby injecting the high-pressure fuel from the nozzle holes opened by the needle valve. In either type of the electronic control fuel injection system, the injector has a solenoid valve, and a controller in the form of an electronic control device controls the timing and duration of supplying a drive current to the solenoid valve to supply the highly pressurized working fluid to the injector, which in turn injects fuel in a predetermined amount at a predetermined timing from nozzle holes formed at the front end of the injector.
Under the non-idling condition a target fuel injection amount is determined based on data, such as a map which is preset so that the engine output characteristic and exhaust gas characteristic remain optimum in response to the engine revolution speed and load (for example, accelerator opening (or the amount by which the accelerator pedal is depressed)). During idling it is desired that the engine revolution remain constant and thus the target fuel injection amount is determined by setting a target revolution speed for the idling operation and performing a PID control, which is based on a difference between the target revolution speed and the engine revolution speed, so that the engine revolution speed matches the target revolution speed. A decision on whether the engine is idling or not is based, for example, on the engine revolution speed and the accelerator pedal depression amount (accelerator opening). The target revolution speed for idling is determined by correcting a basic revolution speed according to the on/off state of an air conditioner and a warming-up switch, the basic revolution speed being set based on data which was determined beforehand according to the engine temperature (for example, a cooling water temperature detected by an engine cooling water temperature sensor). The target fuel injection amount for idling is determined by adding to a basic fuel injection amount set according to the engine temperature a PID correction amount which is obtained based on the revolution speed difference described above. The target fuel injection amount obtained through the correction is injected during idling to prevent cyclic changes and offsets in revolution speed as well as delays in following rapid revolution speed changes.
As one of the electronic control fuel injection systems that adopt an unit injector of the above hydraulically activated type, there is an electronic control fuel injection system disclosed in Published Japanese translations of PCT international publication No. 511526/1994. In this electronic control fuel injection system the pressure of the engine oil as the working fluid is controlled through an electronic device such as solenoid valve installed in the injector to allow simultaneous control of the fuel injection amount and the fuel injection timing.
An injector
50
shown in
FIG. 10
includes a nozzle body
52
having nozzle holes
64
for injecting fuel formed at its front end, a solenoid body
53
mounting a solenoid
60
as a solenoid actuator, an injector body
54
and a fuel supply body
55
. The injector
50
has a pressure increasing chamber
57
supplied with a fuel from a common rail
63
, a pressure chamber
58
supplied with a working fluid, a pressure increasing piston
59
driven by the working fluid supplied to the pressure chamber
58
to pressurize the fuel in the pressure increasing chamber
57
, a return spring
71
for resetting the pressure increasing piston
59
, and a case
56
formed with a fuel supply port
61
and a fuel discharge port
62
, both opening to the common rail
63
to form a fuel chamber
70
. In the injector
50
the needle valve
65
is moved up or down by the fuel pressure from the pressure increasing chamber
57
to open or close nozzle holes
64
. The pressure increasing piston
59
comprises a large-diameter portion
68
, which is slidably fitted in a hole
66
formed in the injector body and forms part of a wall surface of the pressure chamber
58
, and a small-diameter portion
69
, which is slidably fitted in a hole
67
and forms part of a wall surface of the pressure increasing chamber
57
.
The fuel pressurized by a fuel pump to a relatively low pressure is supplied through the common rail
63
, the fuel supply port
61
and the fuel chamber
70
into the pressure increasing chamber
57
. The fuel in the pressure increasing chamber
57
is pressurized by the pressure increasing piston
59
and delivered from the pressure increasing chamber
57
at a fuel injection pressure. The engine oil as the working fluid that is pressurized by a high-pressure oil pump to a high pressure is accumulated in a high-pressure oil manifold (or an oil rail, see FIG.
9
). To actuate the pressure increasing piston
59
, the oil rail is connected to the pressure chamber
58
in the injector
50
and a solenoid valve
51
is installed in a hydraulic pressure passage in the injector
50
through which the engine oil is fed. A drive current from the controller energizes the solenoid
60
to operate a valve disc
72
thus opening the solenoid valve
51
, with the result that the engine oil is supplied through the hydraulic pressure passage to the pressure chamber
58
, as shown by an arrow, acting on a pressure receiving surface of the pressure increasing piston
59
to drive (or stroke) the pressure increasing piston
59
. The fuel in the pressure increasing chamber
57
is pressurized by the pressure increasing piston
59
and as the needle valve
65
is moved up or down in the body of the injector
50
by the fuel pressure from the pressure increasing chamber
57
, the nozzle holes
64
formed at the front end of the nozzle body
52
are opened or closed to inject the fuel into the combustion chamber through the open nozzle holes
64
. Because the injector
50
pressurizes the fuel in the pressure increasing chamber
57
by the pressure increasing piston
59
, the fuel injection is carried out at a fuel injection pressure ind
Browdy and Neimark
Gimie Mahmoud M
Isuzu Motors Limited
Yuen Henry C.
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