Intake air quantity control system for internal combustion...

Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – With indicator or control of power plant

Reexamination Certificate

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C701S114000, C701S115000, C123S399000

Reexamination Certificate

active

06718254

ABSTRACT:

This application is based on Application No. 2001-180166, filed in Japan on Jun. 14, 2001, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to an electronic control system for controlling an intake air quantity in an internal combustion engine for a motor vehicle with a throttle valve operated by an electric motor with improved control performance while ensuring enhanced fail-safe. More particularly, the present invention is concerned with an intake air quantity control system for an internal combustion engine of the type in which a pair of central processing units or microprocessors (hereinafter referred to as the CPU in abbreviation) are employed for effectuating primary or main controls such as ignition control and fuel supply control for the internal combustion engine (hereinafter also referred to simply as the engine) with the control functions being efficiently and effectively shared between the paired CPUs for improving the control performance.
Further, the present invention is concerned with an intake air quantity control system equipped with a default position restoring mechanism which is so designed as to allow the throttle valve to be automatically restored to a position corresponding to an opening degree slightly greater than that in an idle operation upon breaking or turn-off of a load relay through which an electric power is supplied to the throttle valve control motor, wherein a backup function (fail-safe control) is adopted for coping with abnormality which may possibly occur upon restoration to the default throttle position to thereby realize the intake air quantity control with high control performance and reliability, ensuring thus improved fail-safe feature.
2. Description of Related Art
In general, the electronic throttle control for controlling the opening degree of the throttle valve through which the intake air is fed to the engine in dependence on the depression stroke or degree of an accelerator pedal is extensively adopted in practical applications. In recent years, the intake air quantity control system for the engine of wireless type in which the accelerator pedal wire is spared has been widespread.
Additionally, such intake air quantity control system for the engine has been proposed in which the accelerator pedal wire is used jointly as a backup means or in which the accelerator pedal wire is used in the ordinary driving operation whereas an electric motor is used in a constant-speed operation, e.g. a cruising operation.
On the other hand, the control for the engine system as a whole can be classified into a main control for engine driving machinery (i.e., devices or machines having direct relevancy to the operation of the engine) such as an ignition coil, a fuel injection solenoid valve and the like and an auxiliary equipment control for peripheral equipments such as an electromagnetic valve for a transmission, an electromagnetic clutch for an air-conditioner and the like. Under the circumstances, there have been proposed various types of intake air quantity control systems which differ from one another in respect to what sort of CPU configuration is to be adopted in combination with the control of the throttle valve.
For having better understanding of the concept underlying the present invention, description will first be made of the background techniques.
FIG. 9
of the accompanying drawings is a block diagram showing only schematically a general arrangement of a conventional intake air quantity control system for an internal combustion engine which system is designed to perform all controls for the engine by using a single CPU
600
a.
Referring to
FIG. 9
, output signals
610
a
of various sensors indicating operation states of the engine are inputted to the CPU
600
a
. As the various sensor output signals
610
a
, there may be mentioned such on/off signals and analogue signals which are derived, respectively, from the outputs of an engine rotation speed detecting sensor, a crank angle sensor, an air flow sensor for measuring the intake air quantity (i.e., flow rate of the intake air), an intake pressure sensor, an exhaust gas sensor, a water temperature sensor, an accelerator pedal position sensor (hereinafter also referred to as the APS in abbreviation) for measuring the degree of depression of an accelerator pedal, a throttle position sensor (hereinafter also referred to as the TPS in short) for measuring or detecting the opening degree of a throttle valve, a shift position sensor for detecting a position of a speed shift lever and others.
The CPU
600
a
is so designed or programmed as to output control signals
620
a
and
621
a
for various types of actuators which the engine is equipped with. The control signal
620
a
is destined for controlling operations of primary or main machinery such as an ignition coil, a fuel injection solenoid valve, a speed stage shifting solenoid valve and an exhaust gas recirculation (EGR) controlling solenoid valve as well as auxiliary equipments such as an air-conditioner and the like. On the other hand, the control signal
621
a
is destined for the control of a throttle valve control motor or the like.
Incidentally, the conventional system known heretofore for performing all the controls with the single CPU
600
a
, as shown in
FIG. 9
, is disclosed in, for example, Japanese Patent Application Laid-Open Publications Nos. 176141/1990 (JP-A-2-176141) and 141389/1999 (JP-A-11-141389).
However, the conventional systems such as mentioned above suffers a serious problem that an excessively heavy burden is imposed on the CPU
600
a
for realizing satisfactorily the desired engine performance as well as the specified functions and that adequate fail-safe function can not always be ensured for coping with abnormal events occurring in the engine system.
As is well known in the art, so long as the intake air quantity can be controlled with high reliability, there will arise no fear of runaway of the engine. Accordingly, the control of the intake air quantity (i.e., control of flow rate of the intake air) is one of the most important factors for ensuring the safety for operation of the engine. Under the circumstances, it is desirable to provide the relevant sensors and the CPUs in a duplexed arrangement (redundant arrangement) especially for the electronic control of the throttle valve.
FIG. 10
is a block diagram showing schematically a first conventional intake air quantity control system for an internal combustion engine which system is implemented in a triplex CPU configuration in which three CPUs
600
b
,
601
b
and
602
b
are employed for the control purpose.
Referring to
FIG. 10
, inputted to the CPU
600
b
are various sensor signals
610
b
relevant to the main machinery (and auxiliary equipments) from the engine speed detecting sensor, the crank angle sensor, the air flow sensor, the intake pressure sensor and the like. The CPU
600
b
is so programmed as to generate control signals
620
b
for the main machinery (and the auxiliary equipment) on the basis of the input sensor signals.
On the other hand, inputted to the CPU
601
b
are sensor signals
611
b
for the throttle control from the accelerator pedal position sensor (APS), the throttle position sensor (TPS) and the like. In response to these sensor signals, the CPU
601
b
outputs a control signal
621
b
for the throttle valve control motor.
Furthermore, a sensor signal
612
b
for supervisory control is inputted to the CPU
602
b
which is so programmed as to output a control signal
622
b
destined for the supervisory control of a load relay, an electromagnetic clutch and others with the aim of ensuring high fail-safe or security for the electronic control of the throttle valve.
The conventional system in which a plurality of CPUs are employed as in the case of the system shown in
FIG. 10
is disclosed in e.g. Japanese Patent Application Laid-Open Publications Nos. 278502/1994 (JP-A-6-278502) and 2152/1999 (JP-A-11-2152).
In these

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