JPH0463224B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a failure detection method for a control device for an internal combustion engine.

Recently, in automotive internal combustion engines, fuel injection,
A control device is provided that centrally controls ignition timing, idle speed, etc. by a single control circuit using a microcomputer. The control circuit calculates various engine control amounts based on various engine parameters such as intake air amount and cooling water temperature to drive electromagnetic valves, relay switches, and the like. For this reason, in the control device, sensors for detecting engine parameters and actuators such as electromagnetic valves are connected to the control circuit by harnesses.

In such control devices, when an abnormality occurs, it is not easy to tell from the outside where the fault is, so a fault detection method is adopted that uses a microcomputer to detect the fault and notify the driver. ing.

Conventionally, such fault detection methods have determined that when the voltage level of the harness is outside the normal voltage level range, there is a fault in the sensor, actuator, or output section of the control circuit connected to the harness, and generates an alarm corresponding to the fault location. This method allowed the microcomputer to sequentially inform the harness voltage level during the calculation time of engine control variables. However, in conventional fault detection methods,
There has been a problem in that even if pulse signals such as ignition signals and fuel injection pulses are missing pulses or noise is mixed in, it is not possible to determine a failure from the pulse signals.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a failure detection method that can determine a failure from a pulse signal.

The fault detection method according to the present invention detects and stores the period of a signal on a signal line such as a harness, and compares the current period with the previous period for each signal line.
It is characterized in that a failure is determined when the difference is greater than the previous cycle.

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1, 2, and 3.

FIG. 1 is a block diagram of an apparatus using the fault detection method according to the present invention. In Fig. 1, a control circuit 1 is a circuit that calculates control amounts for engine fuel injection, ignition timing, and idle speed, and a harness 2 is connected to the input/output end of the control circuit 1 to which pulse signals are input/output.
Sensors, actuators (not shown), etc. are connected to each other via terminals ₁ to 2 _o . A shaping circuit 4 ₁ for removing noise components of the pulse signal is connected to the intermediate point of the harness 2 ₁ via a harness 3 ₁ . Further, shaping circuits 4 ₂ to 4 _o are similarly connected to other harnesses 2 ₂ to 2 _o via harnesses 3 ₂ to 3 _o . Frequency divider circuits 51 _{to 5o} are connected to the output terminals of the shaping circuits ₄₁ to _4o , respectively, _and the frequency divider circuits ₅₁ to _5o are frequency divider circuits.
Frequency divider circuit ₅ Control circuit 1 at each output terminal of 1 to 5 _o
A microcomputer 6 is connected separately from the microcomputer . The microcomputer 6 is a so-called one-chip type in which an input/output interface, memory, etc. are integrally formed in addition to a microprocessor. The microcomputer 6 is also provided with a display 7 made of a light emitting diode or the like to indicate the location of a failure.

In the above configuration, for example, the noise component of the pulse signal applied to the harness 2 ₁ is removed by the shaping circuit 4 ₁ via the harness 3 ₁ . The frequency is then divided by 2 by the frequency divider circuit 5 ₁ , and then the microcomputer 6
is supplied to Pulse signals applied to the harnesses 2 ₂ to 2 _o are similarly supplied to the microcomputer 6 .

Next, the operation of the microcomputer 6 will be explained with reference to the flowchart shown in FIG.

The microcomputer 6 first starts operating with a frequency dividing circuit 11 and a frequency dividing circuit 5 ₁ in response to a clock pulse.
to 5 _o are selected in a predetermined order12. Next, it is determined whether the output voltage of the selected frequency dividing circuit has increased (13), and the rising edge of the pulse signal is detected. If the output voltage of the frequency dividing circuit has not increased, the process returns to step 12. However, when the output voltage of the frequency divider circuit is rising, the count value of the counter (not shown) corresponding to the selected frequency divider circuit must be read.
T _o 14. Then, the counter is reset and then operated again 15. Next, it is determined whether the output voltage change of the selected frequency dividing circuit is the first or second time 16. When the change is the first or second time, the period T _o is stored as the previous period T _o-1 , and step 17 is performed. Return to 12. However, when it is the third time or more, it is determined whether the relationship between the previous period T _o-1 and the period T _o is T _o >2T _o-1 (18). If T _o ≦2T _o-1 , the period
Store T _o as the previous period T _o-1 (17), and return to step 12 again. However, when T _o >2T _o-1 , it is determined that there is a failure and the display 7 is activated to issue an alarm.
19 generates a display signal to turn on the light.

As a result, if a pulse signal such as that _shown in _FIG . calculates the period T ₃ when pulse A is missing, T ₃ >
Since it becomes 2T ₂ , a display signal is generated.

In addition, the display 11 is designed to light up the failure points related to the signal lines of the harnesses 2 ₁ to 2 _o using light emitting diodes, but when the microcomputer 6 detects two related failure points, Generates a display signal that lights up only the main cause of the failure. For example, if it is detected that the crank angle sensor and the injection valve have failed at almost the same time, the engine is programmed to turn on only the crank angle sensor. Further, the shaping circuit and frequency dividing circuit may not be necessary depending on the pulse signal. In addition, in the present invention, even if a pulse drop occurs in a pulse signal,
There is a range where T _o > 2T _o-1 does not occur, but in a transient state of the engine, even when the engine is operating normally, there is a good chance that the engine rotation will change by about T _o ≒ 1.5T _o-1 . T _o − to prevent false positives
A failure is determined when T _o-1 is greater than T _o-1 .

As described above, according to the failure detection method according to the present invention, a failure of the control device can be detected from the pulse signal when there is an abnormality such as a pulse dropout or noise inclusion in the pulse signal. Furthermore, by displaying the failure location using a light emitting diode or the like, the repair location can be easily found. Furthermore, the difference between the current period T _o and the previous period T _o-1 of the pulse signal T _o −T _o-1
It is determined that there is a failure when is greater than the previous period T _o-1 , so if the pulse signal on the signal line has periodicity, even if the normal period is not known in advance,
In addition, it is possible to identify failures even with pulse signals whose period changes gradually during normal operation, and in this respect, it is more versatile than comparing T _o − _{T o-1} with a fixed value, and other The present invention can be easily applied to control devices for different internal combustion engines.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a device using the fault detection method of the present invention, Fig. 2 is an operation flow diagram of the microcomputer shown in Fig. 1, and Figs. 3a and b are operational waveform diagrams of the circuit shown in Fig. 1. It is. Explanation of symbols of main parts, 1...Control circuit, 2 ₁
or 2 _o , 3 ₁ or 3 _o ... Harness, 4 ₁ or 4 _o ... Shaping circuit, 5 ₁ or 5 _o ... Frequency dividing circuit,
6...Microcomputer.

Claims (1)

[Claims] 1. Failure detection method for a control device for an internal combustion engine, which includes a controlled device, a sensor that detects various parameters from the internal combustion engine, and a control circuit that controls the controlled device according to the detected values of the various parameters from the sensor. The period of the signal on each signal line between the controlled device, the sensor, and the control circuit is detected and stored, the current period and the previous period are compared for each signal line, and the difference is calculated as the previous period. A failure detection method characterized in that a failure is determined when the period is greater than .