Internal-combustion engines – Engine speed regulator – Idle speed control
Reexamination Certificate
2002-11-04
2004-04-06
Solis, Erick (Department: 3747)
Internal-combustion engines
Engine speed regulator
Idle speed control
C123S456000, C123S457000, C123S479000
Reexamination Certificate
active
06715468
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based on Japanese Patent Applications No. 2001-341620 filed on Nov. 7, 2001 and No. 2001-353508 filed on Nov. 19, 2001 the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel injection system that has a safety valve for keeping fuel pressure below a predetermined pressure, specifically, the present invention provides a method of and apparatus for executing a failsafe control when the safety valve is activated.
2. Description of Related Art
Generally, a conventional fuel injection system pressurizes fuel and supplies pressurized fuel to cylinder through an injector. In order to keep a fuel pressure within an appropriate range, the fuel injection system may have a safety valve for discharging pressurized fuel from an accumulator or the like when the fuel pressure exceeds a predetermined pressure. The safety valve may be called as a pressure suppresser, a relief valve or a pressure limiter. The safety valve enters an opened state in response to a fuel pressure exceeding the limit setting pressure.
A common rail type fuel injection system is known as a fuel injection system for diesel engines. The common rail type fuel injection system handles high-pressure fuel. Therefore, it is required not only to keep fuel pressure within a predetermined appropriate range, but also to keep the engine running even if the safety valve is activated.
A high-pressure supply pump accumulates high-pressure fuel in a common rail serving as an accumulator by applying a pressure to the fuel in an operation called a pressure feed operation. The high-pressure fuel accumulated in the common rail is then distributed to a plurality of injectors each provided on a cylinder employed in a multi-cylinder engine. The high-pressure fuel distributed to the injectors is finally injected and supplied into a combustion chamber. An inlet metering valve provided at the inlet of the high-pressure supply pump. The inlet metering valve is used for changing and adjusting fuel volume discharged by the high-pressure pump to the common rail by adjusting the intake volume of fuel introduced into the inlet of the high-pressure supply pump. The high-pressure pump is driven by the engine.
A pressure limiter is provided on at least one of a fuel pipe connecting the high-pressure supply pump to the injectors and the common rail. The pressure limiter discharges fuel from the fuel pipe or the common rail to decrease the fuel pressure when the fuel pressure in the fuel pipe and the common rail exceeds a predetermined limit pressure. Such an abnormally excess pressure may be caused by a malfunction on the inlet metering valve. For example, if the inlet metering valve is completely opened due to a mechanical malfunction or a short circuiting, the high-pressure supply pump feeds excessive amount of fuel into the common rail and raises the fuel pressure. The pressure limiter prevents excessive increase of the fuel pressure and assures the reliability of the common rail type fuel injection system.
That is, in a completely opened state of the inlet metering valve with the multi-cylinder engine rotating at an idle revolution speed, the pressure limiter enters an opened valve state because the pressure of fuel in the common rail exceeds the limit setting pressure, letting fuel flow from the fuel pipe and the common rail to the low-pressure side so that the pressure of fuel decreases to a level not higher than the limit setting pressure. As a result, it is possible to assure the reliability of the common rail type fuel injection apparatus.
With the conventional common rail type fuel injection apparatus, however, in an idle state with a small pump fed volume, the pressure limiter enters an opened valve state and a closed valve state alternately in a repeated manner. For example, due to a small pump fed volume, the common rail pressure may swing between an open pressure and a close pressure of the pressure limiter during the engine is operated under an idling state as shown in FIG.
7
. Thus, the pressure of fuel in the common rail and the fuel injection volume become unstable, raising a problem of the engine's rotational instability. At the same time, the increased number of times the pressure limiter enters an opened valve state and a closed valve state alternately causes spring fatigue and a bad seal seat, raising a problem of impossibility to assure reliability of the pressure limiter.
In addition, if the inlet metering valve provided at the inlet of the high-pressure supply pump is an electromagnetic valve of the normally closed type, a breakage of a wiring harness connecting a pump driving circuit to the inlet metering valve results in no fuel discharged from the high-pressure supply pump so that it is impossible to sustain a common rail type fuel pressure and a fuel injection volume, which are required to operate the multi-cylinder engine. As a result, there is raised a problem called an engine stall.
In the case of a normally open electromagnetic valve employed as the inlet metering valve, the high-pressure supply pump supplies fuel at an excessively high pressure or at a maximum flow rate in the event of an abnormality as shown in time charts of
FIGS. 13 and 14
. Examples of the abnormality are an abnormality of a completely open state of the inlet metering valve and an abnormality of a completely closed state of the inlet metering valve. The abnormality of a completely open state of the inlet metering valve is typically caused by a broken wire harness for supplying a pump drive signal from an electronic control unit (ECU) to the inlet metering valve or an abnormality of control executed by the ECU. On the other hand, the abnormality of a completely closed state of the inlet metering valve is typically caused by a foreign substance inadvertently between a valve body and a valve seat of the inlet metering valve.
In the conventional common rail fuel injection system, however, a fuel discharge caused by a valve opening operation of the pressure limiter and a fuel leakage caused by an abnormality and/or a failure of a high-pressure pipe route cannot be distinguished from each other. An example of the abnormality and/or the failure of a high-pressure pipe route is a burst of a high-pressure pipe. For example, a fuel discharge caused by an opened valve state of the pressure limiter may be detected as a fuel leakage by leakage detection logic as shown in the time charts of
FIGS. 13 and 14
, and a failsafe measure such as an operation to stop the engine is taken. However, there is raised a problem of the driver's excessively aroused anxiety. When the pressure limiter is put in an opened valve state due to an excessive pressure applied by the high-pressure supply pump, for example, it is desirable to let the vehicle continue its running state so as to realize the limp home running of the vehicle.
SUMMARY OF THE INVENTION
It is thus an object of the present invention to provide a fuel injection system capable of assuring reliability of a pressure safety valve by eliminating idle performance instability caused by operations to open and close the pressure safety valve repeatedly.
It is another object of the present invention to provide a fuel injection system capable of avoiding an engine stall and putting the vehicle in a smooth limp home state in the event of an excessive pressure feed of the high-pressure supply pump.
It is still another object of the present invention to provide a fuel injection system capable of improving reliability and safety by execution of engine control whereby implementation of failsafe control is changed in accordance with the type of a fuel pressure decrease.
It is yet another object of the present invention to provide a fuel injection system capable of improving reliability and safety by identifying an abnormality which may be caused by an operation of a pressure safety valve or a state of an excessively high pressure feed supplied by a high-pressure s
Matsumura Toshimi
Uchiyama Ken
Denso Corporation
Nixon & Vanderhye P.C.
Solis Erick
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