JPH0145568B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for outputting fault diagnosis results for an internal combustion engine.

In a control system that controls the operation of an internal combustion engine using a microcomputer, failure diagnosis is used to detect abnormalities in each element that makes up the system, such as various sensors, actuators, etc., and to notify a repair person of the abnormality. processing is normally performed. FIG. 3 is a block diagram showing the configuration of a conventional electronic control unit equipped with an output terminal for outputting fault diagnosis results. In the figure, 10 is an electronic control unit that controls various operations of the internal combustion engine, and 12-1 to 12-n are an air flow sensor, a crank angle sensor, a vehicle speed sensor, and 12-n that detect the operating state of the engine. Various sensors are shown, such as a water temperature sensor, intake air temperature sensor, throttle position sensor, and _O2 sensor. Reference numeral 14 is used to perform adjustments such as reference angle position adjustment for ignition timing control, and to diagnose failures of each sensor. A predetermined signal when performing
For example, an electronic control unit 1 to which a ground signal is applied
0 indicates a dedicated input terminal, 16 indicates a switch provided between the input terminal 14 and ground, and 18 indicates a battery.

In FIG. 3, 20 further includes a fuel injection mechanism that adjusts the fuel injection amount of the engine according to an output signal from the injection time control circuit 42 of the electronic control unit 10;
22 is an ignition mechanism that adjusts the ignition timing according to the output signal from the ignition timing control circuit 44 of the electronic control unit 10, and 24 is an ignition mechanism that adjusts the ignition timing in accordance with the air-fuel ratio correction amount in the duty ratio calculation circuit 46. After that, dedicated output terminals 25-1 to 25-n to which the air-fuel ratio adjustment signal converted into a voltage value is output in the averaging circuit 48 are used when the corresponding sensors 12-1 to 12-n fail. It shows a dedicated output terminal from which a signal is output.
Reference numeral 26 indicates a voltmeter which is connected to this output terminal 24 by a repair person so as to know the air-fuel ratio adjustment signal.

The electronic control unit 10 includes an input port 30 that receives detection signals from each of the sensors 12-1 to 12-n and a signal applied to the input terminal 14 via an input buffer 28, a central processing unit (CPU) 32,
It includes a microcomputer consisting primarily of a read-on memory (ROM) 34, a random access memory (RAM) 36, an output port 38, and a clock generator 40. 41 is a low voltage source for supplying power to the electronic control unit 10.

In the conventional electronic control unit configured as described above and equipped with an output terminal for fault diagnosis results,
The failure diagnosis results for each element obtained by a predetermined failure diagnosis routine are sent to various sensors 12-1 to 12-n input to the electronic control unit 10, as shown in FIG. The signals are output to dedicated output terminals 25-1 to 25-n provided correspondingly when each sensor fails, and the repair person can select which output terminals 25-1 to 25-n.
The location of the failure was recognized based on whether a failure signal appeared.

Furthermore, this type of control system has an ignition timing control function that performs control based on the crank angle signal from the distributor, and in order to adjust the position of this crank angle signal, a predetermined signal is used. It has a dedicated input terminal that outputs ignition timing at a fixed advance angle when applied.

As described above, in this type of conventional control system, a plurality of output terminals for outputting failure diagnosis results, an output terminal for air-fuel ratio adjustment signals, and an input terminal for ignition timing adjustment are provided. Ori,
For this reason, there was a problem in that the manufacturing cost of the system was high and the system configuration was complicated by the number of terminals.

The present invention solves the above-mentioned conventional problems, and by making the output terminal dedicated to the failure signal and the output terminal for the air-fuel ratio adjustment signal double, the cost at the time of manufacturing the system is reduced, and the system configuration is simplified. The purpose of the present invention is to provide a method for outputting diagnostic results for an internal combustion engine.

According to the internal combustion engine diagnostic result output method of the present invention, when a predetermined signal is not applied to the electronic control unit, the electronic control unit outputs the current air-fuel ratio state to the dedicated output terminal for the air-fuel ratio adjustment signal. If a predetermined signal is applied to the electronic control unit, the electronic control unit outputs a signal representing the failure diagnosis result to the output terminal dedicated to the air-fuel ratio adjustment signal.

The features of the present invention that achieve the above-mentioned objects are as follows:
An air-fuel ratio control device that feedback-controls the fuel injection amount according to the air-fuel ratio state of the internal combustion engine, and an output terminal that outputs an air-fuel ratio adjustment signal having an electrical signal according to the air-fuel ratio state of the internal combustion engine. In the internal combustion engine, when an output switching signal is applied to a predetermined input terminal, an electric signal representing a failure diagnosis result of each element of the engine is outputted to the output terminal instead of the air-fuel ratio adjustment signal. be.

The present invention will be explained in detail below using the drawings.

FIG. 1 is a block diagram showing a schematic configuration of an embodiment of the present invention. In the figure, 10 is an electronic control unit that has a built-in microcomputer and controls various operations of the internal combustion engine; 12-1;
12-n are various sensors that detect the operating state of the engine, such as an air flow sensor, a crank angle sensor, a vehicle speed sensor, a water temperature sensor, an intake air temperature sensor,
Throttle position sensor, O ₂ sensor, etc. are shown, and 14 is a predetermined signal (hereinafter referred to as IS signal),
For example, an electronic control unit 1 to which a ground signal is applied
This is a dedicated input terminal of 0, and in this embodiment, it is pressed when obtaining the output of failure diagnosis of each sensor 12-1 to 12-n. 16 is the input terminal 14
18 indicates a battery. Switch 16 may be replaced by a removable ground connector.

In FIG. 1, 20 also adjusts the fuel injection amount of the engine in accordance with the output signal from the electronic control unit 10, and 22 also controls the ignition timing in accordance with the output signal from the electronic control unit 10. 24 represents a dedicated output terminal for outputting an air-fuel ratio adjustment signal having a voltage value corresponding to the air-fuel ratio correction amount and a signal representing a failure diagnosis result, and 26 represents a repair person. indicates a voltmeter connected to this output terminal 24 to obtain an air-fuel ratio adjustment signal or a failure diagnosis result.

The electronic control unit 10 includes an input port 30 that receives detection signals from each of the sensors 12-1 to 12-n and a signal applied to the input terminal 14 via an input buffer 28, a central processing unit (CPU) 32,
It includes a microcomputer consisting primarily of a read-on memory (ROM) 34, a random access memory (RAM) 36, an output port 38, and a clock generator 40. 41 is a constant voltage source for supplying power to the electronic control unit 10.
The CPU 32 connects the input port 30 to each of the sensors 12-1 to 12-n and the input terminal 1 according to a control program stored in the ROM 34 in advance.
4 signals, and performs calculations related to fuel injection time, ignition timing, failure diagnosis of each sensor, actuator, etc. according to these input data, and temporarily stores the results in RAM 36 and outputs them to the output port at a predetermined timing. 38 or directly to output port 38.

The basic value of the fuel injection time is calculated from the intake air amount and rotational speed of the engine, and the oxygen component concentration in the exhaust gas detected by the O ₂ sensor,
That is, the air-fuel ratio correction amount corresponding to the current air-fuel ratio state is fed back and corrected, and further corrected based on water temperature, throttle position, etc., to obtain the final injection time value. The binary representation of the injection time sent to the output port 38 is sent to the injection time control circuit 42 consisting of, for example, a down counter and converted into a drive signal having a pulse width corresponding to the calculated injection time. Fuel injection mechanism 2
0, and the fuel supply amount is controlled. The fuel injection amount control method as described above is well known and is not directly related to the present invention, so a detailed explanation will be omitted.

The ignition timing is calculated according to a predetermined function based on the intake air amount, rotational speed, water temperature, etc. of the engine, and the calculated value is sent to the ignition timing control circuit 44, which includes a down counter, etc., through the output port 38. The signal is sent, converted into a signal representing ignition timing, and then sent to the ignition mechanism 22 for control. Such an ignition timing control method is also well known and is not directly related to the present invention, so a detailed explanation will be omitted.

The CPU 32 performs failure diagnosis detection for each element, that is, each sensor 12-1 to 12-n and each actuator, according to a known diagnostic processing routine, and transmits the results to the RAM 3 for each element.
It is stored in a predetermined bit of 6. In addition, if even one of the elements is diagnosed as abnormal,
A predetermined abnormality occurrence flag FDIAG in the RAM 36 is set (set to "1").

When the switch 16 is open, the CPU 32
That is, when the IS signal is not applied, an output value corresponding to the above-mentioned air-fuel ratio correction amount is sent to the duty ratio calculation circuit 46 via the output port 38, and when the switch 16 is closed, that is, when the IS signal is is applied to the RAM 36 in the arithmetic circuit 46.
The failure diagnosis results stored in the control circuit 44 are sent to the control circuit 44, and the ignition timing signal to be sent to the control circuit 44 is set to a fixed value corresponding to a predetermined fixed advance angle value.

The above-mentioned operation will be explained in detail below using the flowchart shown in FIG.

The CPU 32 executes the interrupt processing routine shown in FIG. 2 at predetermined intervals, for example, every 50 msec. That is, first, in step 50, it is determined whether the switch 16 is closed and the IS signal is input to the input terminal 14. If the IS signal is not input, that is, if the switch 16 is open, the process proceeds to step 51, and the process corresponds to the air-fuel ratio feedback amount (air-fuel ratio correction amount) used in the calculation of the fuel injection time described above. The binary number V _f is outputted to the duty ratio calculation circuit 46 via the output port 38 . Binary number corresponding to this air-fuel ratio correction amount
For example, when the air-fuel ratio is the stoichiometric air-fuel ratio, a voltage value of 2.5V is output to the output terminal 24 _, and when the current air-fuel ratio is lean and correction in the rich direction is required, a voltage value of 2.5V is output to the output terminal 24. A large voltage value is output, and when the current air-fuel ratio is rich and correction in the lean direction is required, it is applied to the duty ratio calculation circuit 46 so that a voltage value smaller than 2.5V is output to the output terminal 24. Duty ratio calculation circuit 46
is composed of a presettable down counter, and its output is kept at "1" until it finishes counting the preset binary number _Vf , and when the counting is finished, its output becomes "0". This output therefore has a duty ratio corresponding to the preset binary number. Assuming that the clock period of this down counter applied from the clock generator 40 is 20 μsec, and the down counter is 12 bits, if the preset value is “2500” or more in decimal notation, then ( 50m
sec), the down counter does not finish counting, so
The duty ratio becomes 100%, and the duty ratio calculation circuit 46 always outputs a signal in the "1" state. Further, if the preset value is "1250", the duty ratio will be 50%, and if the preset value is "0", the duty ratio will be 0%. The output of the duty ratio calculation circuit 46 is converted into a voltage corresponding to the duty ratio in an averaging circuit 48. In other words, when the duty ratio is 100%, it is 0V, and when it is 50%, it is 0V.
If it is 2.5V or 0%, it is converted to 5V and output from the output terminal 24.

Therefore, in this embodiment, for example, (1) When the air-fuel ratio is the stoichiometric air-fuel ratio, the decimal number "1250" preset by the duty ratio calculation circuit 46 is converted to a duty ratio of 50%, and this is converted into a duty ratio of 50% by the averaging circuit 48. It is converted into a voltage and a voltage value of 2.5V is output to the output terminal 24.

(2) When the air-fuel ratio is lean and correction is made in the rich direction, a decimal number smaller than "1250" is preset in the duty ratio calculation circuit 46 and converted to a duty ratio smaller than 50%, which is converted into a voltage in the averaging circuit 48. is converted to output terminal 24.
A voltage value greater than 2.5V is output.

(3) When the air-fuel ratio is rich and the air-fuel ratio is corrected toward the lean direction, a decimal number larger than "1250" is preset in the duty ratio calculation circuit 46 and converted to a duty ratio larger than 50%, which is converted into a voltage in the averaging circuit 48. is converted to output terminal 24.
A voltage value smaller than 2.5V is output.

In step 51, a flag indicating whether or not the process is in the process of outputting the failure diagnosis result is also set.
Processing to reset DIAGOUT to "0" is also performed, and then the current interrupt processing is ended.

If it is determined in step 50 that the IS signal is being input, that is, if the switch 16 is closed, the program proceeds to step 52, where the value output to the ignition timing control circuit 44 is set to a predetermined fixed value. Set to the value corresponding to the angle, for example 8° CA.BTDC. Next, the process proceeds to step 53, where it is determined whether or not the abnormality occurrence flag FDIAG is "1". As a result of the fault diagnosis, if there is no abnormality in the sensor or actuator and FDIAG is reset to "0", the process advances to step 54, and the duty ratio calculation circuit 46 causes the down counter to count during one interrupt cycle. a large value that cannot be accommodated
V ₀ , for example, if the counter is 12 bits and its counting clock is 20 μsec, outputs a value of “2500” or more. As a result, the duty control circuit 46
The output of is always "1", and as a result, the output voltage of the averaging circuit 48 is 0V. In step 54, DIAGOUT is further reset to "0", after which the current interrupt processing ends. As a result of the above processing, the voltage at the output terminal 24 gradually becomes 0V, so that the repair person who monitors the output from the output terminal 24 can see that there is no abnormality at all in the sensor.

As a result of the fault diagnosis, there is an abnormality in one of the sensors or actuators, so FDIAG
If it is set to "1", the program proceeds to step 55 and thereafter, and outputs the failure diagnosis results for each item. First, in step 55, it is determined whether or not the diagnostic result is being outputted based on whether DIAGOUT is "1". When passing through step 55 for the first time, DIAGOUT is "0", so the process proceeds to step 56, and from the predetermined area of the RAM 36 where the failure diagnosis results are stored, the result output areas DIAG(m) to DIAG(m) for each diagnostic item are output. DIAG
(o) and also the above
The DIAGOUT flag is set to "1" and the output time measurement timer TDIAG is reset to "0". Note that this step 56 will be
Jumped in as long as DIAGOUT is “1”.

In the next step 57, the diagnosis result DIAG(m) regarding the diagnosis item with the highest priority is "1".
It is determined whether or not. In other words, RAM36
Bits DIAG(m) to DIAG(o) store results for each diagnostic item in order of priority. For example, if DIAG (m) is "1", the air flow sensor is defective, if DIAG (m-1) is "1", the water temperature sensor is defective, and DIAG (m-2) is "1".
In this case, it is stored to indicate that the crank angle sensor is defective. If the diagnostic item corresponding to DIAG(m) is abnormal, the program returns to step 58.
It is determined whether the measured value TDIAG of the above-mentioned timer, which has been measuring immediately since the time of reset, has exceeded the predetermined time T _0. If TDIAG<T ₀ , the procedure advances to step 59 and this DIAG ( The duty ratio calculation circuit 4 calculates the value V(m) stored in the ROM 34 in advance corresponding to the diagnostic item m).
Output to 6. After that, the timer measurement value TDIAG is
This process of step 59 is repeated until T ₀ or more, and when TDIAG≧T ₀ , step 60 is executed.
Proceed to DIAG(m) is reset to “0”,
The timer is reset. Therefore, the duty ratio calculation circuit 46 outputs a signal having a duty ratio corresponding to V(m) for the time _T0 , and the averaging circuit 48 outputs a signal having a duty ratio corresponding to the duty ratio, that is, V(m). The corresponding voltage is output for a time T ₀ . This time T ₀ is a time such that the voltage can be recognized by the human eye. The repair person measures the voltage at the output terminal 24 with the voltmeter 26, and
(m) By detecting that the corresponding voltage continues for _T0 , it is recognized that an abnormality has occurred in the diagnostic item corresponding to the above-mentioned DIAG (m).

If DIAG(m) is determined to be "0" in step 57, that is, if there is no abnormality in the diagnostic items related to DIAG(m), or if there is an abnormality, output processing of the result has been completed. ,
The program includes the following diagnostic items, DIAG (m-
1), DIAG(m-2), ..., DIAG(1), DIAG(o)
Perform the same process sequentially for each diagnosis item, and if there is an abnormality in each diagnostic item,
V(m-2), . . . , V(1), and V(o) are outputted, and the process reaches step 64. However, V(m) to V(o)
are different values from each other, and by measuring the voltage that continues for a time T ₀ , the repair person can determine that the sensor corresponding to the measured voltage value is faulty. After resetting DIAG(o) and resetting TDIAG in step 64, the program proceeds to step 65, where DIAGOUT is reset to "0" and the process of outputting the results of all diagnostic items is completed.

Thereafter, as long as the IS signal is input and the FDIAG flag is "1", the same process as described above is repeated. Note that this FDIAG flag is reset to "0" when the engine's power switch (ignition switch) is closed or the starter switch is opened. However, in an electronic control unit equipped with a backup RAM, it is reset to "0" if no new abnormality is detected while the ignition switch is closed a predetermined number of times.
Furthermore, when the FDIAG flag is reset to "0", all fault diagnosis results within a predetermined area of the RAM 36 are cleared.

From the above, according to the routine shown in Figure 2,
The electronic control unit 10 of FIG. 1 performs the following three types of operations.

(a) Output of air-fuel ratio correction amount This is the operation when the IS signal is not input to the electronic control unit.The operation in step 51 is performed, and the binary number V _f corresponding to the air-fuel ratio correction amount is output to the duty ratio calculation circuit. The arithmetic circuit 46 converts it into a duty ratio signal according to the binary number V _f , and the averaging circuit 48 converts this signal into a voltage, which is output to the output terminal 24 .

(b) Output when there is no abnormality in the fault diagnosis result This is the operation when the IS signal is input, and the operation in step 54 is performed, and the down counter in the duty ratio calculation circuit 46 cannot count at one interrupt. A large value V ₀ is output, and the output is always in the "1" state, and the output voltage 0V from the averaging circuit 48 is output to the output terminal 24.

(c) Output when there is an abnormality in the failure diagnosis result If there is an abnormality in the failure diagnosis result when the IS signal is input, the diagnosis result is read from a predetermined area of the ROM 34 in step 56. For example, if only the diagnostic item corresponding to DIA(m) is abnormal, the step
57 becomes YES and the process proceeds to step 58, where the value V(m) previously stored in the ROM 34 corresponding to the diagnostic item DIA(m) is sent to the duty ratio calculation circuit 46 so that the timer measurement value TDIAG is _T0. It will be output until it reaches the above value. After the time has elapsed, it is checked whether there are any abnormalities in other diagnostic items, and if any abnormalities are found, the same operation is performed, and if there are no abnormalities, the failure diagnosis is ended.

As described above, according to the present embodiment, when the switch 16 is closed, voltages set to be different for each item are output from the output terminal 24 for a predetermined period of time for each item that has an abnormality as a result of diagnosis. Output. Therefore, repairers can use very simple means,
For example, the diagnostic results can be very easily obtained for each item using the voltmeter 26 or other means that can identify the voltage.

As explained in detail above, according to the method of the present invention, when an output switching signal is applied to a predetermined input terminal, the failure diagnosis result of each element of the engine is displayed from the terminal to which the air-fuel ratio adjustment signal is output. Since electrical signals are output, there is no need to provide a dedicated output terminal for outputting diagnostic results, and the number of output terminals is significantly reduced. As a result, the system configuration can be simplified and costs can be reduced.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a schematic configuration of an embodiment of the present invention, Fig. 2 is a flowchart of a part of the control program in the above embodiment, and Fig. 3 is a conventional system equipped with an output terminal for fault diagnosis results. FIG. 2 is a block diagram showing the configuration of an electronic control unit. 10...Electronic control unit, 12-1 to 12
-n...Sensor, 14...Input terminal, 16...Switch, 20...Fuel injection mechanism, 22...Ignition mechanism, 24...Output terminal, 26...Voltmeter, 32...
...CPU, 34...ROM, 36...RAM, 46
...Duty ratio calculation circuit, 48...Averaging circuit.

Claims (1)

[Claims] 1. an air-fuel ratio control device that feedback-controls the fuel injection amount according to the air-fuel ratio state of the internal combustion engine; an output terminal to which an air-fuel ratio adjustment signal having an electrical signal according to the air-fuel ratio state of the internal combustion engine is output; In an internal combustion engine equipped with a failure diagnosis device that performs failure diagnosis of each element of the engine, when an output switching signal is applied to a predetermined input terminal, the output switching signal of each element of the engine is applied instead of the air-fuel ratio adjustment signal. A method for outputting diagnostic results for an internal combustion engine, comprising outputting an electrical signal representing a failure diagnostic result to the output terminal.