Vehicle control apparatus

Abstract: A vehicle control apparatus is provided with a plurality of unit controllers (2, 6) each controlling respectively different control functions so that mutual communication of data for diagnosis is effected between the unit controllers, and when one (2) of the unit controllers develops a fault, the other (6) or others change their control mode so as to lead the vehicle to safety, based on the data from the one unit controller developing a fault.

Description: Background of the Invention The present invention relates to an apparatus for controlling a vehicle having diversified control items such as an automobile and, more particularly to a vehicle control apparatus suitable for raising the safety of an automobile provided with an internal engine such as a gasoline engine. Various kinds of controllers using a micro-computer have come to be employed in recent years. A variety of controllers with a micro-computer have now been applied to automobiles for the purposes of controlling a power transmission mechanism and an air conditioner, suspension control, or the like, in addition to various controls concerning the engine, in individual units. EP-A-0270036 discloses a vehicle speed control system for a vehicle having an automatic transmission control and an automatic speed control. When the vehicle speed control cannot control the vehicle speed, the automatic transmission control effects a fixed speed travelling control by making a shift into delay mode or fixed mode. The vehicle speed is thus shifted to a fixed speed. There is thus a self-diagnosis in the automatic transmission control but the automatic speed control does not diagnose the fault in the automatic transmission control to change its own control mode. JP-A-60-135332 has duplicate systems which when trouble occurs in one of the systems has a detection circuit that switches control to the other system. However, there is no control unit which effects self-diagnosis. US-A-4,472,777 discloses an engine control apparatus for limiting engine speed to a predetermined level based on signals from various sensors and the result is provided to an engine control computer. The various sensors are merely applied to an AND gate logic circuit and there is no self-diagnosis in any of the controllers. Some conventional unit controllers each are provided with a self-diagnosis function and a fail-safe function. However, they have no problem so long as each of the unit controllers exhibits reliably its fail-safe function but does not take into consideration the fact that when any abnormality occurs in any of various load driving circuits controlled by the unit controllers, the fail-safe function cannot be obtained. For example, "Automobile Engineer" April, 1988, p. 41 roughly discloses that a mutual communication system between computers for control is incorporated in order to obtain an optimum control. However, the papers do not touch the above-mentioned problem. Therefore, the conventional technique has a problem with respect to provision of sufficient reliability. Summary of the Invention An object of the present invention is to provide a vehicle control apparatus which backs up the fail-safe function for a plurality of unit controllers of a vehicle and can always secure reliably sufficient safety of the vehicle. More particularly, an object of the present invention is to provide a vehicle control apparatus in which a fail-safe function provided for at least one of a plurality of unit controllers is backed up by at the other unit controller or controllers and sufficient safety can be always secured reliably. According to this invention there is provided a vehicle control apparatus having a plurality of unit control means each provided for a different control function, at least one of said unit control means having a self-diagnosis function and effecting self-diagnosis therefor, characterized by data transfer means (SCI) for allowing said at least one unit control means to transfer data for determination and use by another unit control means and allowing said another unit control means to transfer refined data to said at least one unit control means, and means provided in said another unit control means for diagnosing said at least one unit control means on the basis of said data transferred therefrom, and for changing a control mode of said another unit control means whereby said control mode of said another unit control means is changed in dependence upon the result of diagnosis by said another unit control means so as to secure safety of the vehicle. Preferably, even when a certain unit controller loses its fail-safe function due to the occurrence of abnormality, at least one of the other unit controllers changes its control mode to compensate for the drop of safety caused thereby, such as the decrease in a fuel supply quantity by an engine controller as one of the unit controllers for the abnormal increase in intake air due to abnormality of an auto-cruising controller as the other unit controller, for example, and since this counter-measure is provided, reliable back-up can always be obtained. Brief Description of the Drawings Fig. 1 is a block diagram showing an embodiment of a vehicle control apparatus according to the present invention; Fig. 2 is a characteristic diagram of an auto-cruising controller; Fig. 3 is a block diagram showing details of a part of Fig. 1; Figs. 4a and 4b each are a flowchart for explaining the vehicle control apparatus; Fig. 5 is a characteristic diagram of a fuel correction coefficient; Fig. 6 is a characteristic diagram of the auto-cruising controller; Fig. 7 is a block diagram showing another embodiment of a vehicle control apparatus according to the present invention; Fig. 8 is a flowchart for explaining the vehicle control apparatus shown in Fig. 7; Fig. 9 is a block diagram showing still another embodiment of a vehicle control apparatus according to the present invention; and Fig. 10 is a block diagram showing details of a monitor employed in Fig. 9. Description of the Invention A vehicle control apparatus according to the present invention will be described on its embodiments. First of all, an embodiment of the vehicle control apparatus according to the present invention will be described hereunder in detail referring to Figs. 1 to 6. In Fig. 1, an engine controller 6 and an auto-cruising controller 2 are employed as a plurality of unit controllers. The engine controller 6 executes calculation according to the following equation (1) on the basis of r.p.m. (N) of an automobile engine 1 detected by a crank angle sensor 10 and an intake air flow rate (Qa) detected by an air flow sensor 9 mounted in an intake passage, thereby to obtain a fuel injection pulse width Tp. Tp = f (Qa · N) (1) Then, the engine controller 6 supplies a pulse signal having this fuel injection pulse width Tp to a fuel injector drive circuit 61 which inputs a signal to a fuel injection valve 7 provided on the intake passage to drive it according to the fuel injection pulse width Tp thereby to execute a control so as to obtain a predetermined air-fuel ratio. In parallel with such an operation, the engine controller 6 exchanges predetermined data with the auto-cruising controller 2, diagnosis the function of the auto-cruising controller 2, executes the operations to be later described when any abnormality is detected in this auto-cruising controller 2, and turns on an alarm lamp 8 to give an alarm to the user. The auto-cruising controller 2 controls the rotating speed of the engine so that the vehicle travels automatically at a constant speed set by the user (driver) and the relation between the set speed by the user and the traveling speed of the car is shown in Fig. 2. Referring to Fig. 3, the auto-cruising controller 2 includes a micro-computer 20, an amplification circuit 21, an output driving device (power transistor) 22, a resistor 23 and a speed set switch 15. The micro-computer 20 receives, as a set car speed, the car speed from the car speed sensor 4, which car speed is set by the user through a pushing operation of the speed set switch 15 and its value being one at the time the speed set switch 15 is pushed, and, stores the set car speed in RAM, calculates an opening signal (S₁) of the throttle valve 3 using the set car speed, controls the throttle valve actuator 5 through the amplification circuit 21 and the output driving device 22 to control the opening of the throttle valve 3 and executes feedback control so that the actual car speed detected from the car speed sensor 4 converges to the set car speed. At this time, a current flowing through the output driving device (power transistor), that is, a current supplied to the throttle valve actuator 5, flows through the resistor 23 so that a predetermined signal F1 can be obtained. Therefore, the micro-computer 20 receives this signal F1, makes self-diagnosis or self-checking by judging whether or not its level is within a predetermined range and executes a fail-safe control. In this embodiment, a data transfer system by SCI (Serial Communication Interface) is disposed between the auto-cruising controller 2 and the engine controller 6 so that the data transfer can be made between the auto-cruising controller 2 and the engine controller 6. Among the data of the auto-cruising controller 2 which are taken in by the micro-computer 20, predetermined data are also taken in by the micro-computer 60 of the engine controller 6, and among the data of the micro-computer 60, some necessary data are also transferred to the micro-computer 20. Next, the case where any abnormality occurs in the auto-cruising controller 2 will be explained. It will be now assumed that a short-circuit accident takes place in the output driving device of the auto-cruising controller 2 for some reason or other. Then, a current keeps flowing through the actuator 5 and the throttle valve 3 is kept fully open because the actuator 5 is constructed such that the throttle valve 3 is always urged by a spring to close and driven by an electromagnetic means to be opened against the spring force. As a result that the throttle valve 3 is kept fully open, the intake air flow rate increases drastically and since the engine controller 6 increases the quantity of the fuel jetted from the fuel injection valve 7 in accordance with this intake air flow rate Qa as expressed by the afore-mentioned equation (1), uncontrolled driving is likely to occur irrespective of the driver's intention of auto-cruising. This accident cannot be prevented by the fail-safe control of the auto-cruising controller 2 itself at this time. In other words, the fail-safe control at this time can only switch the control signal for the output driving device 22 to the OFF direction through the amplification circuit 21 and cannot cope with the short-circuit trouble of this output driving device 22. In this embodiment, the micro-computer 20 in the auto-cruising controller 2 detects the current flowing through the output driving device 22 from the signal F1 resulting from the voltage drop of the resistor 23 as described above, makes judgement for the self-diagnosis processing depending on whether or not the current exceeds a predetermined value and transmits the result to the engine controller 6. When the short-circuit accident described above occurs, therefore, the accident is recognized by the micro-computer 60 of the engine controller 6. More specifically, the micro-computer 20 of the auto-cruising controller 2 transmits the data representing that "the throttle valve 3 is fully open due to the short-circuit of the output driving device 22" to the micro-computer 60 of the engine controller 6. In response thereto, the micro-computer 60 reduces the pulse width Tp described already so as to reduce the fuel quantity supplied from the fuel injection valve 7, thus to limit the increase in the number of revolution of the engine 1, to light the alarm lamp 8 and to give the alarm to the user. Therefore, in accordance with this embodiment, the auto-cruising controller 2 as one of the unit controllers can be backed up by the engine controller 6 as the other unit controller even when the fail-safe function of the auto-cruising controller 2 does not operate effectively, and the uncontrolled operation of the engine 1 can be reliably prevented. Next, the processing described above will be explained with reference to the flowchart shown in Figs. 4a and 4b. First of all, the micro-computer 20 of the auto-cruising controller 2 executes the processing shown in Fig. 4a in each predetermined period. In other words, a set car speed value, which is set by the driver and inputted into the micro-computer 20, is sent to the engine controller 6 at step 101. Self-diagnosis or self-checking such as whether or not the current F1 is in a predetermined range is made at step 102, and its result is transferred to the engine controller 6 at the subsequent step 103. In other words, an NG signal representing not-normal condition is transferred when any abnormality is detected. On the other hand, the micro-computer 60 of the engine controller 6 executes the processing shown in Fig. 4b. Namely, the set car speed value VSPs is taken into the micro-computer 60 from the micro-computer 20 at step 104 and an actual car speed VSPn is received from the speed sensor 4 through the micro-computer 20 at step 105. At the subsequent step 106, it is judged whether or not this actual car speed VSPn is equal to or less than the sum of the set car speed value VSPs and a value α, which is added in order to provide the former with a predetermined allowance range. If the result proves to be NO, the flow proceeds to step 107, where whether or not the NG signal is received is judged. If the result proves to be YES here, the micro-computer 60 judges that an abnormality occurs in the auto-cruising controller 2 and the possibility of uncontrolled operation of the engine exists. Then, steps 108 and 109 are executed. Namely, a fuel correction coefficient β having a numeric value of below 1.0 is multiplied by the ordinary EGI (fuel injection) pulse width Tp, outputs the product as a fuel injection pulse width Tpng (= β · Tp) at the time of abnormality and execute the alarm lamp ON processing at the subsequent step 109. In this case, the fuel correction coefficient β changes in a decreasing direction as a function of the time t elapsed from the point (to) of the occurrence of abnormality as shown in Fig. 5, for example. According to this embodiment, therefore, the control by which the number of revolution N of the engine is decreased with the passage of time t after the point (to) of the occurrence of abnormality in the auto-cruising controller 2 is made automatically as represented by dashed line 111 in Fig. 6, and back-up can be reliably obtained. Incidentally, the characteristics represented by solid line 110 in this drawing show the case where back-up by this embodiment cannot be obtained, and represents that the number of revolution of the engine increases with the passage of time and a critical state will be reached. In the embodiment described above, the auto-cruising controller 2 and the engine controller 6 make direct mutual data communication to obtain the necessary back-up data communication to obtain the necessary back-up function. Next, another embodiment of the present invention will be explained with reference to Fig. 7. The embodiment shown in Fig. 7 represents a structural example of a vehicle control apparatus including an auto-cruising controller and an engine controller as a plurality of unit controllers that do not have a mutual data communication function. The construction in Fig. 7 is the same as one in Fig. 1 except that a car speed setting switch 15 is connected to a micro-computer 60 so that a set car speed can be inputted into the micro-computer 60. Therefore, explanation about the other construction is omitted. Further, the same parts or apparatus in Fig. 7 as ones in Fig. 1 are referred to by the same reference numerals. Next, the operation of this embodiment will be explained with reference to the flowchart of Fig. 8. First of all, at step 112, the signal of the car speed setting switch 15 for setting a car speed on the auto-cruising controller 2 is received to judge whether or not a car speed is set. If the result is YES, the set car speed is received at step 113 to obtain the data VSPs. Processing is completed there if the results at the steps 112 is NO. At step 114, the actual car speed VSPn is taken into and at the subsequent step 115, this car speed VSPn is compared with a certain predetermined car speed reference value VSPs + α. When the car speed value VSPn is more than the car speed reference value VSPs + α, judgement is made to the effect that any abnormality occurs in the auto-cruising controller 2 and here the next step 116 is executed. Namely, the normal fuel injection pulse width Tp is multiplied by the correction coefficient β to execute the fuel injection pulse width T PNG at the time of abnormality and the alarm lamp 8 is lit at the subsequent processing of step 117 to complete the processing. According to this embodiment, too, it is possible to obtain sufficient back-up, to check reliably the uncontrolled operation of the engine and to secure sufficient safety even when any abnormality occurs in the auto-cruising controller 2 and moreover when the fail-safe function for it does not operate. Next, Fig. 9 shows still another embodiment of the present invention. In this embodiment, the auto-cruising controller 2 and the engine controller 6 do not individually make the abnormality judgement but a monitor 12 disposed separately from, and independently of, them makes the abnormality judgement. The monitor 12 is constructed by a micro-computer 62 as shown in Fig. 10. Data communication between the auto-cruising controller 2, the engine controller 6 and the monitor 12 is carried out by SCI. In this embodiment, it is possible to make data communication between the auto-cruising controller 2 and this monitor 12 in the same way as in the embodiment shown in Fig. 1 so as to obtain the back-up function. It is also possible to employ the structure where the data communication function is not provided in the same way as in the embodiment shown in Fig. 7 but the monitor 12 executes the back-up processing by inputting the signal from the car speed sensor 4 to the monitor 12. Although the present invention has been explained with reference to the foregoing embodiments wherein abnormality detection between the engine controller and the auto-cruising controller and between them and the monitor is made, the present invention is not particularly limited thereto but can of course be practised in other ways. Needless to say, the present invention may be constituted for the purpose of backing up between the unit controllers with any other control items as the control object. Although the foregoing embodiments deal with the case where a certain unit controller changes its own control item when it diagnosis the abnormality of other unit controllers, it is of course possible to employ the construction wherein the function of the unit controller itself from which the abnormality is detected is stopped. As described above, the present invention can be applied to any controllers such as an air conditioner, a suspension controller, a power transmission controller, and the like, that are mounted into a vehicle, as the unit controller, and back-up can of course be obtained between these controllers when the abnormality diagnosis and fail-safe function therebetween cannot be obtained. According to the present invention, sufficient back-up can be obtained at the time of the occurrence of abnormality in various unit controllers such as the auto-cruising controller and the engine controller of a vehicle, and there can be obtained the effect that safety can be always secured reliably.

Claims: A vehicle control apparatus having a plurality of unit control means (2, 6) each provided for a different control function, at least one of said unit control means (2) having a self-diagnosis function and effecting self-diagnosis therefor, characterized by data transfer means (SCI) for allowing said at least one unit control means (2) to transfer data for determination and use by another unit control means (6) and allowing said another unit control means (6) to transfer refined data to said at least one unit control means (2), and means (60, 61) provided in said another unit control means (6) for diagnosing said at least one unit control means (2) on the basis of said data transferred therefrom, and for changing a control mode of said another unit control means (6) whereby said control mode of said another unit control means (6) is changed in dependence upon the result of diagnosis by said another unit control means (6) so as to secure safety of the vehicle. A vehicle control apparatus according to claim 1, wherein said data transfer means (SCI) also allows said at least one unit control means (2) to transfer said self-diagnosis result of said one unit control means (2) to said another unit control means (6), and said diagnosing means (60, 61) changes a control mode of said another unit control means (6) in response to said diagnosis result of said at least one unit control by said another unit control means (6) as well as said self-diagnosis result of said at least one unit control means (2), so as to secure safety of the vehicle. A vehicle control apparatus according to any preceding claim, wherein when abnormality in said at least one unit control means (2) is detected, the control mode of said another unit control means (6) is changed so that a controlled system (3 or 7) to be controlled by said another unit control means (6) is controlled so as to secure safety of the vehicle. A vehicle control apparatus according to any preceding claim, wherein said at least one unit control means (2) is an autocruising controller for controlling the vehicle so as to travel at a set speed on the basis of data including an actual vehicle travelling signal detected by a speed sensor (4) and a set speed signal, and the other unit control means (6) is an engine controller for controlling an engine so as to inject an optimum amount of fuel into the engine by an injector (7) on the basis of engine conditional data including a throttle (3) opening and engine revolution numbers (10), and wherein when abnormality in said autocruising controller is detected, the control mode of said engine controller is changed so that a speed of the vehicle is decreased gradually. A vehicle control apparatus according to claim 4, wherein said engine controller (6) is arranged to generate a signal to said fuel injector (7) for decreasing the fuel injection amount with the passage of time from a time the abnormality takes place in said autocruising controller (2). A vehicle control apparatus as claimed in any preceding claim wherein said data transfer means (SCI) permits said another unit control means (6) to transfer data evaluated thereby to the at least one unit control means (2), whereby the at least one unit control means (2) can diagnose the another unit control means if required.

Inventors: ABE OSAMU, HASEGAWA TAIJI, ISHIKAWA HIDEAKI, ABE, OSAMU, HASEGAWA, TAIJI, ISHIKAWA, HIDEAKI
Applicants: HITACHI AUTOMOTIVE ENG, HITACHI LTD, HITACHI AUTOMOTIVE ENGINEERING CO., LTD., HITACHI, LTD.
Application year: 1989
Main classification: B60K28
IPC codes: F02B1, B60R16, F02D41, G01M17, F02D45, B60W30, B60W50