SELF-DIAGNOSING APPARATUS OF VEHICLE

Abstract: A self-diagnosing apparatus of a vehicle, which can reliably hold and store diagnostic data relating to major troubles. A control unit (1) includes a CPU (101) and a RAM (102) that keeps the data if the ignition switch is turned off. The self-diagnosing apparatus detects a plurality of troubles, which are classified into major ones and minor ones. The RAM (102) includes a plurality of memory regions comprising a frame (1) and frame (2), and these frames (1) and (2) are corresponding to major and minor troubles, respectively. The CPU (101) processes diagnostic data of each part of the vehicle necessary for analyzing troubles of instruments and updates the memory contents of individual regions of the frames (1) and (2). If a trouble with an instrument is detected, the CPU (101) sets a trouble code to the leading region of the frame corresponding to that trouble, and inhibits subsequent updating of the memory content. Accordingly, the diagnostic data can be stored and held depending on the classification of trouble.

Description: The present invention relates to a self-diagnosing apparatus for a motor vehicle according to the preamble of claim 1. At the present time the construction of motor vehicles has become remarkably influenced by electronic components. Instruments, including, among other things, the engine, installed in each section of a motor vehicle, are interconnected to each other via a control computer so that complex operations can be performed. In such case, even if a malfunction of a certain single installed instrument is detected, often the true cause for the malfunction, including the interrelation with other installed instruments, cannot be determined unless a wide range of data (diagnostic data) indicating the state of the motor vehicle at the time the malfunction is detected, is collected. Also, after a temporary malfunction, there is a possibility that the malfunction will be corrected naturally. Further, often this is a sign that a complete failure will occur; however, it is quite difficult to find the cause thereof by performing an inspection after getting out of the motor vehicle. A self-diagnosing apparatus according to the preamble of claim 1 is disclosed in JP-A-62-142849 and 63-90738, in which diagnostic data from each section of a motor vehicle is updated and stored in a memory where the contents are stored at specified intervals even when the power supply is shut down; updating of the contents of the memory is inhibited (frozen) after a malfunction of an installed instrument is detected, so that diagnostic data at the time the malfunction is detected will be stored and the cause of the malfunction can be determined accurately after getting out of the motor vehicle. A similar type of an self-diagnosing apparatus is known from RP-B-72 000. Not all malfunctions of the installed instruments in a motor vehicle have the same priority or importance. For example, since malfunctions such as a misfire in the engine, a malfunction of the fuel system and the like are serious malfunctions, such malfunctions have a higher priority than those of other malfunctions. Therefore, even if other malfunctions having respectively lower priorities occur earlier, when a malfunction having a higher priority occurs, thereafter, diagnostic data obtained at that time must be held in precedence over other data. However, in the above-described conventional apparatus, when diagnostic data is frozen once a malfunction of the apparatus has occured, such diagnostic data is not updated even when a malfunction having a priority higher than that of the above one occurs thereafter. Therefore, when a malfunction having a high priority is detected, it is conceivable that the diagnostic data is replaced forcibly. However, if an ignition switch is turned off while this data is being replaced, a portion of the data which has not yet been replaced remains in a part of the memory and, on the contrary, erroneous diagnostic data is given, which is problematical. It is conceivable that a main relay for supplying power for some time after the ignition switch has been turned off is provided, however, such construction results in the hardware becoming overly complex. The present invention solves the above-described problems of the prior art. It is an object of the present invention to provide a self-diagnosing apparatus for motor vehicles which is capable of reliably storing diagnostic data of different priority malfunctions. This object is solved by the characterising features of claim 1. The basic features of the present invention now will be explained with reference to Fig. 10. The present invention comprises diagnostic data detecting means for detecting diagnostic data necessary for analyzing malfunctions of instruments installed in a motor vehicle; storing means for storing a plurality of storage areas disposed so as to respectively correspond to priorities of the malfunctions of the instruments installed in a motor vehicle so that diagnostic data detected by the data detecting means is updated and stored as desired for each of the storage areas, and the stored contents thereof are held even when the ignition switch is in a turned off state; malfunction detecting means for detecting malfunctions of the instruments installed in the motor vehicle; inhibiting means for inhibiting the updating and storing of the diagnostic data corresponding to the priority of the malfunction in the storage area of the storing means; and diagnostic data output means for outputting the contents of the storing means from the storage areas respectively corresponding to priorities of the malfunctions. In the above-described apparatus, storage areas, the number of which corresponds to the number of the priorities of the instrument malfunctions, are provided. Therefore, even if an instrument malfunction with a low priority is detected and diagnostic data relating to this malfunction is frozen, since diagnostic data of the storing means corresponding to the instrument malfunction with a high priority is not frozen, the updating of the diagnostic data relating to the malfunction with a low priority is continued. When, thereafter, an instrument malfunction with a high priority is detected, diagnostic data relating to this malfunction is frozen and held. Since an operation for replacing diagnostic data on an instrument malfunction having a high priority with diagnostic data on an instrument malfunction having a low priority is unnecessary, no problem, for example, one in which diagnostic data on an instrument malfunction having a low priority remains in a portion of the diagnostic data as a result of an ignition switch being turned off during the above replacing operation, occurs. As described above, according to the self-diagnosing apparatus of the present invention, it is possible to reliably store diagnostic data for analyzing a serious instrument malfunction having a high priority. Brief Description of the Drawings Fig. 1 is an illustration of the entire construction of the self-diagnosing apparatus; Fig. 2 is a block diagram of the control unit; Fig. 3 is a program flowchart; Fig. 4 is a program flowchart; Fig. 5 is a program flowchart; Fig. 6 is a program flowchart; Fig. 7 is an illustration of the memory configuration; Fig. 8 is a program flowchart; Fig. 9 is a program flowchart; and Fig. 10 is a conceptual block diagram of the basic features of the present invention. Best Mode for Carrying Out the Invention In Figs. 1 and 2, a potentiometer 21 of a flow meter 31, an intake-air temperature sensor 24, a throttle sensor 27 of a throttle valve 32, and a fuel discharge valve 29 are disposed in the upstream portion of an intake-air pipe E1 of an engine E. A water temperature sensor 23 is disposed in a water jacket of the engine E, and an O2 sensor 22 is disposed in a discharge pipe E2 of the engine E. A control unit 1 having a CPU 101 contained therein is disposed, and the CPU 101 is connected via a data bus to a RAM 102, a ROM 103, an oscillation circuit 104, input/output ports 105A and 105B, and output ports 106A, 106B, and 106C. The RAM 102 is separated into a common RAM for temporary storage and a standby RAM in which the contents at the time the ignition key is turned off are held. Output signals from the potentiometer 21, the O2 sensor 22, the water temperature sensor 23, the intake-air temperature sensor 24 and the throttle sensor 27 are input through a multiplexer 107 and an A/D converter 108 to the input/output port 105A. Output signals from a cylinder determination sensor 25 and a rotational angle sensor 26 are input through a waveform shaping circuit 109 to the input/output port 105B. The output signals are supplied via output ports 106B and 106C to an igniter 28 and the fuel discharge valve 29. When a malfunction of each of the above-mentioned instrument installed in a motor vehicle is detected by a sequence to be described later, an output signal is issued to a malfunction warning means 5 through the output port 106A and a drive circuit 112A. As will be described later, diagnostic data necessary for analyzing instrument malfunctions are exchanged via the input/output port 105B and an intercommunication circuit 110 with a fault diagnosing apparatus 4. Fig. 3 shows a program for detecting a misfire malfunction. The program is activated at intervals of 30° crank angles (CA). When TDC is confirmed in step (hereinafter referred to as S) 101, the amount ΔNE (TDC) of variations in the number of rotations of the engine for the duration of 60° CA up to TDC is calculated in S102. Next, BTDC 60° is confirmed in S103. In S104, the amount ΔNE (BT60) of the fluctuation of the engine speed for the duration of 60° CA up to the present time is calculated. In S105, the difference between ΔNE (TDC) and ΔNE (BT60) is calculated. When this difference exceeds 100 rpm, it is assumed that a misfire has occurred (S106), and a fail flag in the common RAM is set (S107). Fig. 4 shows a program for detecting a malfunction of the fuel system. The program is activated at intervals of every 65 ms. A check is made in S201 and S202 to determine whether a FAF has reached an upper limit and a lower limit, respectively. In the above, FAF is an air-fuel ratio correction coefficient which can be obtained by integrating or skipping an output from the O2 sensor. When the state in which FAF is at the upper limit or lower limit continues for 10 s or more (S203), it is assumed that a malfunction has occurred in the fuel system, and the fail flag in the common RAM is set. In a case other than the above, the fail flag is cleared (S205). Fig. 5 shows a program for detecting a malfunction of the throttle sensor 27. In S301, a check is made to determine whether a throttle opening signal is in the range from 0.1 V to 4.9 V (S301, S302). If the signal is in this range, the fail counter is cleared, and the fail flag in the common RAM is cleared (S305, S306). If, on the other hand, the time during which the signal is not present in the above-mentioned range exceeds 500 ms (S303), it is assumed that the throttle sensor has a malfunction, and the fail flag is set (S304). Fig. 6 shows a program for inputting into the standby RAM the fact that the above-mentioned fail flags are set, which program is activated at intervals of every 65 ms. In S401, a check is made to determine whether writing in the standby RAM is possible. When the fail flag has been set, predetermined bits of the standby RAM are set (S402, S403), so that the fact that a specific instrument malfunctions has been detected is stored. The diagnostic data storage areas of the standby RAM are shown in Fig. 7. Frame 1 starting at address 10 is allocated as an area for storing various diagnostic data necessary for analyzing a high priority misfire and a high priority fuel system malfunction. Frame 2 starting at address 20 is allocated as an area for storing various diagnostic data necessary for analyzing malfunctions having lower priority than the above misfire malfunction. A malfunction code indicating the type of the malfunction is set at the beginning address of each frame as described later. Fig. 8 shows a program for controlling writing in the standby RAM. The program is activated at intervals of every 65 ms. In S401, a check is made to determine whether the malfunction code has been set in frame 1. If the code has not been set, the diagnostic data stored in the previous cycle is updated into the newly input diagnostic data (S402). When the malfunction code has been set, updating is inhibited, and the diagnostic data is frozen. In S403, a check is made to determine whether the malfunction code of frame 2 has been set. If the code has not been set, the diagnostic data is updated (S404); if it has been set, the diagnostic data is not updated. In S405 and S406, a check is made for a misfire malfunction and a fuel system malfunction, respectively. If either of these malfunctions is confirmed, the malfunction code of frame 1 is set, so that the diagnostic data is frozen. If the malfunction is one other than one of the two above-described malfunctions, the malfunction code of frame 2 is set, so that the diagnostic data is frozen. Fig. 9 shows a program for connecting a fault diagnosing apparatus after getting out of the motor vehicle and transmitting diagnostic data, which program is activated every 16 ms. In S501, a check is made to determine if frozen diagnostic data has been requested from the diagnosing apparatus. If the request is for frame 1, it is confirmed that the data has been frozen, and diagnostic data of frame 1 for request PID is selected (S502, S503, S504). If the request is for frame 2, it is confirmed that the data has been frozen, and diagnostic data of frame 2 for the request PID is selected (S505, S506, S507). In the above case, the request PID is one in which diagnostic data is requested in an ID format from the diagnosing apparatus. For example, PID1 is the number of rotations of the engine, and PID2 is the speed of the motor vehicle. The selected diagnostic data is transmitted to the diagnosing apparatus (S508). If the request is not for a data request for frame 1 in S502, it is confirmed in S505 that it is a request for frame 2, and diagnostic data for the request PID of frame 2 is transmitted to the diagnosing apparatus in S505, S506, and S507. As described above, since priority is given to the malfunctions of the instrument installed in the motor vehicle, and since the frames, the number of which corresponds to the number of priorities, are secured in the standby RAM, even if a high priority malfunction is detected after a low priority malfunction is detected, diagnostic data necessary for analyzing the latter malfunction is secured instantly. Since it is not necessary to replace diagnostic data in such case, no problem, such as, for example, one in which completely different diagnostic data is stored in a part without being updated when the ignition switch is turned off while the diagnostic data is being replaced, occurs. Although in the above-described embodiment two types of priorities are used, of course the number of frames may be expanded so that three or more types of priorities are included. Industrial Applicability The present invention can be used as an apparatus for supporting the analysis of the cause of the malfunction by a method in which diagnostic data, such as the operating state of the internal combustion engine or the running state of the motor vehicle when a malfunction occurs in the instrument installed in the motor vehicle, is stored so that the state when the malfunction occurred can be reproduced on the basis of the above-described stored diagnostic data when a repair is made after the malfunction of the motor vehicle has occurred.

Claims: A self-diagnosing apparatus for a motor vehicle, comprising: [a] diagnostic data detecting means (21-26) for detecting diagnostic data necessary for analysing malfunctions of instruments (27-29) installed in said motor vehicle; [b] malfunction detecting means (Fig.3-5) for detecting malfunctions of said instruments (27-29) installed in said motor vehicle; [c] storing means (102; Fig.7) for storing and updating diagnostic data relating to respectively detected malfunctions, the stored diagnostic data being held even when an ignition switch is in a turned off state; and [d] diagnostic data output means (5) for outputting the diagnostic data stored in said storing-means (102; Fig.7); wherein [e] each of said detected malfunctions of said instruments (27-29) is assigned to one of at least two different priorities; characterised in that said storing means comprises a plurality of storage areas (Frame 1, Frame 2) which are assigned to said one of at least two different priorities, and said updating of the diagnostic data within the related storage areas (Frame 1, Frame 2) is inhibited if a malfunction having an assigned priority is already stored in a storage area having the same assigned priority. Apparatus according to claim 1, characterized in that said malfunction detecting means (Fig.4) detects a fuel system malfunction of an internal combustion engine as a high priority malfunction. Apparatus according to claim 1 or 2, characterized in that said malfunction detecting means (Fig.3) detects a misfire malfunction of an internal combustion engine as a high priority malfunction. Apparatus according to one of claims 1 through 3, characterized in that each storage area (Frame1, Frame2) comprises a code storage area (10,20) for storing a malfunction code indicating the type of the malfunction and a plurality of data storage areas for storing said diagnostic data. Apparatus according to one of claims 1 through 4, characterized in that said diagnostic data output means (5) outputs diagnostic data to a fault diagnosing apparatus (4) in distinction for each of said storage areas (Frame1, Frame2) for each priority in response to a request from said fault diagnosing apparatus (4) connected to the self-diagnosing apparatus installed in said motor vehicle. Apparatus according to claim 5, characterized in that said diagnostic data output means (5) outputs the stored contents of a high priority when a high priority malfunction has been detected when a request from said connected fault diagnosing apparatus (4) is one for a high priority malfunction, and outputs the stored contents of a low priority when a high priority malfunction has not been detected and a low priority malfunction has been detected. Apparatus according to one of claims 1 through 6, characterized in that two or more malfunctions of the same priority are assigned to be stored in the corresponding storage area (Frame1, Frame2), the updating of the diagnostic data within each of the storage areas (Frame1, Frame2) being inhibited even then when another malfunction of the same priority is detected.

Inventors: FUJISAWA SHUICHI, TAKABA KATSUMI, FUJISAWA, SHUICHI, TAKABA, KATSUMI, FUJISAWA, Shuichi Denso Corporation, TAKABA, Katsumi Denso Corporation
Applicants: DENSO CORP, DENSO CORPORATION
Application year: 1993
Main classification: F02D45
IPC codes: F02D41, F02P11, F02D45