Abstract:
Even in such an arrangement in which the throttle valve is operated independently of the engine control system, abnormal engine behavior is ensured to be detected such that a necessary fail-safe operation should be taken. The arrangement of the invention is comprised of the electronically controlled throttle system, engine control system and engine speed monitoring unit, wherein the electronically controlled throttle system is allowed to monitor engine behaviors. Thereby, in the case when the throttle valve is operated independently of the engine control system, if its engine behavior becomes abnormal relative to its drive contents, the engine system senses the abnormality, and takes a fail-safe operation such as to stop operation of the throttle valve and the like.

Description:
This application is a divisional of application Ser. No. 09/633,896, filed Aug. 7, 2000 now U.S. Pat No. 6,352,064. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a throttle valve control system for opening and closing a throttle valve for use in an automobile by means of an actuator such as a motor or the like. 
     For an electronically controlled throttle system in which the throttle valve is operated by electronic control, in addition to such a case in which a throttle demand opening is instructed from an engine control system and it operates in response to this instruction, there is another case in which an electronically controlled throttle valve is provided independently of the engine control system for allowing operation by determining a control target position thereof by the electronically controlled throttle system itself. More specifically, there are such cases including: a case for driving its throttle to its close direction or to its open direction in order to learn a minimum position (full close learning) or a maximum position (full open learning); a case for driving its throttle by the steps of reading its acceleration pedal position, obtaining a corresponding throttle opening relative to the value read out from a look-up table or the like; or a case in which the electronically controlled throttle system drives its throttle without instruction from the engine control system when data exchange between the electronically controlled throttle system and the engine control system is interrupted. Because that the engine is driven based on an air flow quantity that is controlled by a throttle opening, and a fuel injection control and an ignition control in which the engine control system is involved, in case where the electronically controlled throttle system itself determines a control target for operation, in order appropriately to execute the fuel injection control, the ignition control and the like, it is necessary for the electronically controlled throttle system and the engine control system to exchange information and control the throttle in collaboration with each other. 
     For example, in the throttle full close position learning, all that is required is simply to operate the throttle valve until it makes contact with a stopper provided in its close direction, and it is not necessary for the engine to be rotating. In view of safety, it is rather preferable for the engine not working, thereby suppressing fuel injection and the engine should be stopped. In the full open learning, it is necessary for the engine to be controlled not to rotate. Further, in case a throttle opening is to be set up from a position of the acceleration pedal, it is necessary for the electronically controlled throttle system to inform a present position of the acceleration pedal to the engine control system such that the engine control system executes its engine control appropriately in response to the information. 
     Conventionally, in such a case as above, the electronically controlled throttle system and the engine control system are operated in synchronism with each other, and when the electronically controlled throttle system executes an operation that does not need engine speed, the engine control system is caused to take a measure to stop the engine operation. As a method for synchronizing therebetween, such methods have been utilized as one for taking a necessary step by exchanging contents of operation via a communication line therebetween, or one for monitoring a signal level of its ignition key and synchronizing at a period of timing of a change thereof. 
     However, as for the electronically controlled throttle system, it is more advantageous to be treated as a one unit and to minimize a relation with other systems, more specifically, interdependency with other systems, because a burden for newly incorporating the electronically controlled throttle system is substantially reduced. However, it should be noted that as described above, there is the case in which the electronically controlled throttle system depends on the behavior of the engine that is controlled by the engine control system. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to reduce an interdependency between the electronically controlled throttle system and the engine control system and improve a system reliability. 
     An electronically controlled throttle system of the invention monitors behaviors of an engine that is a target of direct control of an engine control system by means of an engine behavior monitor, and executes a fail-safe processing when a predetermined condition is not satisfied. An example of the engine behavior monitor is an engine speed monitor. 
     More specifically, when the electronically controlled throttle system of the invention controls its throttle independently of the engine control system, monitors engine behaviors using the engine behavior monitor, and if a predetermined condition is not satisfied, executes a fail-safe processing. For example, in the case in which the engine is controlled not to rotate in the step of the full open learning, when the engine behavior monitor that monitors engine speed indicates a value in excess of a predetermined speed, an engine control abnormality is judged to have occurred, and the electronically controlled throttle system terminates the full open learning operation abnormally. An advantage for allowing the electronically controlled throttle system also to monitor the engine behavior in addition to the monitoring and controlling by the engine control system resides in starting the fail-safe processing as quickly as possible and contributing to the improvement in the system reliability. 
     Because the full close learning or the full open learning are operations that do not require engine operation, there may be a case in which the electronically controlled throttle system and the engine control system are desired to be separated. Even in a state they are separated, in a method in which the electronically controlled throttle system is allowed to monitor the engine behavior, the electronically controlled throttle system is ensured to detect abnormality in the engine behavior and proceed to execute its fail-safe operation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic block diagram indicating a first embodiment of the invention; 
     FIG. 2 is a schematic block diagram indicating a second embodiment of the invention; 
     FIG. 3 is a schematic block diagram indicating a third embodiment of the invention; 
     FIG. 4 is a schematic block diagram indicating a fourth embodiment of the invention; and 
     FIG. 5 is a schematic block diagram indicating a fifth embodiment of the invention. 
    
    
     DESCRIPTION OF THE INVENTION 
     Preferred embodiments of the invention will be described with reference to the accompanying drawings in the following. 
     FIG. 1 is a schematic block diagram indicating a first embodiment of the invention. 
     An electronically controlled throttle module  100  communicates with an engine control system  200  via a communication line  150 , receives a throttle demand opening  151  from engine control system  200  and transmits a throttle&#39;s present position  152  to engine control system  200 . Further, the same causes a throttle valve  115  to operate by driving a throttle actuator  110 . A position of throttle valve  115  is read using a throttle sensor  120  to be used as a feedback signal for driving throttle actuator  110 . Engine control system  200  reads an output of an air flow sensor  230 , and controls the output of an engine  250  by operating a fuel injection controller  210  and a ignition controller  220 . An engine speed that is a typical value for indicating engine behaviors is fed back to the engine control system, and is also read in electronically controlled throttle module  100  via engine speed monitor  280 . 
     The learning of the full close position of throttle valve  115  is executed by the electronically controlled throttle module  100  at the time when the ignition switch is turned on or off, under no throttle opening demand from engine control system  200 . Electronically controlled throttle module  100  causes throttle actuator  110  to drive the throttle in the direction of closure, during which, reads values of throttle sensor  120 , and sets up a value of throttle sensor  120  which is judged to have reached its minimum as a learned full closure value. At this stage, electronically controlled throttle module  100  notifies engine control system  200  completion of the full close position learning via communication line  150 . Until the notification of the completion of the full closure learning from electronically controlled throttle module  100 , engine control system  200  does not drive fuel injection controller  210  and ignition controller  220 , and upon notification thereof, drives fuel injection controller  210  and ignition controller  220  to start the engine control operation. 
     In the process of the full closure learning by electronically controlled throttle module  100 , if engine control system  200  misjudges that the electronically controlled throttle module  100  does not execute the full closure learning, the engine control system  200  attempts to control engine  250  by operating fuel injection controller  210  and ignition controller  220 , however, because that throttle valve  115  is driven to its full closure position, there is a probability for the engine  250  to become in a state of engine stall. At this moment, in the case in which a full open learning is to be executed, its engine speed increases with opening of throttle valve  115  in such a case as above. However, according to the invention, because electronically controlled throttle module  100  monitors the revolution of engine  250  via engine speed monitor  280 , when it senses an increase in the engine speed, interrupts its full open learning and closes throttle valve  115 , thereby capable of suppressing the output of engine  250 . 
     In the case described above, when engine speed monitoring unit  280  malfunctions, the state of the engine  250  cannot be known. Therefore, according to the invention, its full open learning is interrupted in the same way as in the case where the engine speed monitoring unit  280  operates normally and an increase in the engine speed is sensed. Malfunctioning of engine speed monitor  280  probably occurs due to a short-circuit or open-circuit of wiring, and can be detected by a change in the output level of engine speed monitor  280 . 
     The foregoing description has been made by way of examples of the full close and the full open learning operations, however, it may also be applied to a case in which a throttle return spring is to be checked. When the throttle control becomes abnormal, throttle valve  115  stops the motor drive as a fail-safe procedure. A return spring is provided for ensuring the throttle valve to return to a predetermined position (a default position) at this instant. The default position is set, not at the full closure position, but mostly at a position at which the throttle valve  115  is slightly open. This is because of ensuring that even if the motor drive is stopped as the fail-safe procedure under abnormality of the throttle control, the vehicle may be moved at least to a safety position. In order to allow for the throttle valve  115  to be moved to a predetermined position at the time when the motor drive is stopped, two kinds of throttle return springs are used for urging throttle valve  115  into both directions of an open and a closure directions. Diagnosis of these two springs whether or not they function normally is done by observation that throttle valve  115  returns to its default position from its full open position and full close position after it is driven thereto, and then the motor drive is stopped. Also, in the diagnosis of this operation, this embodiment of the invention is applicable. 
     A second embodiment of the invention is indicated in FIG. 2, in which engine speed monitor  280  indicated in FIG. 1 of the first embodiment of the invention is eliminated, and instead thereof, its engine speed is notified from engine control system  200  to electronically controlled throttle module  100  via communication line  150 . In the electronically controlled throttle module  100 , only a means for knowing its engine speed is changed, and its operating principle is the same as in the case of FIG.  1 . Further, such a case in which the electronically controlled throttle module  100  fails to learn the engine speed due to abnormality in communication line  150  corresponds to the case of malfunctioning of engine speed monitor  280  described with reference to FIG.  1 . 
     A third embodiment of the invention will be described with reference to FIG. 3. A driver&#39;s intent device  300  is typically represented by an acceleration pedal, and when the driver operates the pedal, it outputs a value in response to its control quantity. Electronically controlled throttle module  100  reads an output value from driver&#39;s intent input device  300 , and obtains a first throttle target opening by means of a driver&#39;s intent/throttle opening converter  310 . Further, an engine control demand opening converter  320  calculates a second throttle target opening on the basis of the throttle demand opening value received from engine control system  200  via communication line  150 . A final throttle target opening arithmetic unit  330  adds the first throttle target opening and the second throttle target opening, and drives throttle actuator  110  in accordance with a value obtained as a result of addition. 
     In the process of receiving a throttle demand opening value from engine control system  200  via communication line  150  according to this embodiment of the invention, it may be considered that the throttle demand opening value cannot be received properly due to a failure such as open circuit, short circuit, or by noise. In such cases, according to this embodiment of the invention, a predetermined value is used as a throttle demand opening value. 
     A fourth embodiment of the invention, which is a modification of the third embodiment above, will be described with reference to FIG.  4 . In this embodiment of the invention, a throttle demand opening buffer  321  is added to in comparison with the configuration of FIG.  3 . Engine control demand opening converter  320 , everytime it calculates a second throttle target opening on the basis of the throttle demand opening value received from engine control system  200  via communication line  150 , stores a result of its calculation in throttle demand opening buffer memory  321 . In case electronically controlled throttle module  100  is unable to receive the throttle demand opening value properly, a second throttle target opening value is calculated on the basis of the values stored in throttle demand opening buffer memory  321 . At this time, as methods of the above calculation, there are such ones as follows. Simply to continue to use the value stored in throttle demand opening buffer  321 , to use a value which is obtained by subtracting a predetermined value from the value stored in throttle demand opening buffer memory  321 , or to change the value to be used along a curve predetermined relative to the value stored in throttle demand opening buffer  321 . 
     A fifth embodiment of the invention will be described with reference to FIG.  5 . In this embodiment of the invention, a target opening select information  153  is received from engine control system  200 . Target opening select information  153  is either value of 1, 2 and 3, and each of which means as follows. 
     1: its final throttle target opening is to be obtained by addition of values of the first throttle target opening and the second throttle target opening, 
     2: its final throttle target opening should be the first throttle target opening, and 
     3: its final throttle target opening should be the second throttle target opening. 
     A case where its target opening select information  153  is “1” corresponds to a normal case; another case where its target opening select information  153  is “2” corresponds to a case in which an output from driver&#39;s intent input device  300  is to be disregarded, wherein its throttle is controlled in accordance with the first throttle target opening requested by engine control system  200  even if the acceleration pedal is not pressed, which corresponds to a case of a cruising state; and the remaining case where its target opening select information  153  is “3” corresponds to a case in which the first throttle target opening received from engine control system  200  is to be disregarded, wherein the second throttle target opening that is calculated on the basis of the throttle demand opening value received from engine control system  200  via communication line  150  is disregarded due to detection of abnormality in communication with engine control system  200 , even if the communication therebetween is recovered, thereby operating throttle valve  115  only according to a value read from driver&#39;s intent input device  300 . 
     According to the invention, even in such a case where the throttle valve is operated independently of the engine control system, it is enabled to detect occurrence of abnormality in the engine and execute a necessary fail-safe procedure.