JPS6348298B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for detecting blow-through in an exhaust valve of an internal combustion engine.

By installing a suitable sensor such as an accelerometer on the exhaust pipe of an internal combustion engine, signals such as those shown in FIGS. 1b and 1c can be detected in normal times when no blow-through occurs and during abnormal conditions when blow-by occurs. In FIG. 1, a indicates the operating timing of the internal combustion engine, 1 is a combustion signal, 2 is an exhaust signal, 3 is an exhaust valve closing signal, and 4 is a blow-through signal that is confirmed when an abnormality occurs.

However, when attempting to detect the presence or absence of blow-through of the exhaust valve and its degree, the sensor detection signal includes unnecessary noise components other than the blow-through signal 4 as shown in FIG.
For accurate detection of the atrium, the atrium signal 4 is required.
It is necessary to extract only the The general method for removing noise components from the detected signal waveform is as follows:
There are methods that use frequency filters and time window methods that create gate signals and extract only signals over a predetermined period. However, in the case of the blow-through signal 4 that we are trying to detect here, the method using a frequency filter cannot fully achieve the purpose due to the signal generation mechanism, so it is necessary to adopt the time window method. In the time window method, synchronization between the gate signal and the signal to be extracted becomes a problem, and especially in the case of high-speed signals, if this synchronization is insufficient, it is not practical.

Since the blow-through signal 4 in an internal combustion engine is generated at a specific crank angle, it is conceivable to detect the crank angle of the internal combustion engine and use it as a synchronization reference signal for the gate signal. To do this, it is necessary to directly connect a highly accurate detector such as a rotary encoder to the rotating shaft of the internal combustion engine, and this is not a practical method for detecting the blow-through signal 4, which requires simplicity. This is the current situation.

Therefore, the present invention aims to eliminate the above-mentioned drawbacks of the time window method.

In order to achieve this object, the method of the present invention detects a signal by installing a vibration or sound detection sensor on the outside of the exhaust pipe of the internal combustion engine to be inspected, and also detects the fuel injection timing or ignition timing of the internal combustion engine. A gate signal having a predetermined time width for extracting the blow-through signal is created using the detected fuel injection timing or ignition timing as a synchronization reference signal, and the signal of the predetermined time width of the detection sensor output signal is extracted using this gate signal. be.

The device of the present invention also includes a sensor that is attached to the outside of the exhaust pipe of the internal combustion engine to be inspected and detects vibration or sound, and a timing sensor that detects the fuel injection timing or ignition timing of the internal combustion engine and outputs a timing detection signal. means, a rotation detection means for outputting a signal with a repetition period corresponding to the rotation speed of the internal combustion engine, and a count value that starts counting the output signal of the rotation detection means at a time when a timing detection signal is generated in the timing detection means. a first preset counter that detects that the first preset value matches the first preset value;
a second preset counter that starts counting the output signal of the rotation detecting means when the preset counter detects a match, and detects that the counted value matches the second preset value;
a preset counter, an RS flip-flop in which one of the coincidence detection outputs of the first and second preset counters is set and the other is reset, and this RS flip-flop output signal is used as a gate signal. A gate circuit is provided for extracting a signal for a period from the coincidence detection time of the first preset counter to the coincidence detection time of the second preset counter from the sensor output.

According to the method of the present invention, when detecting the exhaust valve blow-through signal, there is no need for any work such as directly connecting a highly accurate detector such as a rotary encoder to the rotating shaft, and there is no need to perform any work such as directly connecting a highly accurate detector such as a rotary encoder to the rotating shaft. It can be detected without using a high-precision detector, and high-speed signal blow-through signals can be extracted accurately.

Further, according to the device of the present invention, after the timing detection signal is generated in the timing detection means, the gate signal for extracting the blow-through signal is activated at the time when the count value by the first preset counter matches the first preset value. At the same time, after the gate signal starts, the gate signal ends when the count value by the second preset counter matches the second preset value. Both of the above counts are obtained by counting repeated signals corresponding to the rotational speed of the internal combustion engine, so even if rotational fluctuations occur, those fluctuations are automatically removed and only the blow-through signal period is detected. Extracted accurately.

Hereinafter, a specific embodiment of the present invention will be described based on FIGS. 2 and 3.

Reference numeral 5 denotes a first acceleration sensor, which is attached to the outside of an exhaust pipe (not shown) in a diesel engine as a device under test. A second acceleration sensor 6 is mounted on the outside of a fuel injector (not shown) in the diesel engine. Reference numeral 7 denotes a tachometer unique to the device under test, which outputs a signal with a voltage value corresponding to the rotational speed of the rotating shaft. Reference numeral 8 denotes a voltage-frequency converter (hereinafter referred to as VFC) which outputs a signal with a repetition period corresponding to the output voltage of the tachometer 7, and the repetition period becomes shorter as the rotation speed becomes faster. Reference numeral 9 denotes a signal processing circuit of the second acceleration sensor 6, which detects the fuel injection timing by comparing the set signal level and the input signal level (Fig. 3 c), and outputs a pulse P ₁ of a specified width (Fig. 3 d). Output. Reference numeral 10 denotes a first preset counter, which receives the VFC8 output signal as a counting input, and has a preset value _N01 set as the number of pulses corresponding to the time _T1 between the fuel injection timing and the blow-through signal 4 generation timing; Counting is started at the time when the pulse _P1 is generated, and when the count value _N1 reaches the preset value _N01 , a coincidence detection pulse _P2 (Fig. 3e) is output. Reference numeral 11 designates a second preset counter which, like the first preset counter 10, receives the VFC8 output signal as a counting input, and has the number of pulses corresponding to the gate time _T2 set as the preset value _N02 . Counting is started at the time when the coincidence detection pulse _P2 is generated, and when the count value _N2 reaches the preset value _N02 , a coincidence detection pulse _P3 (FIG. 3f) is output. 12 is R-S
A flip-flop uses the coincidence detection pulses P ₂ and P ₃ as set and reset signals, respectively, and outputs Q.
A gate signal 13 is generated [FIG. 3g]. 14
is a gate circuit that allows the detection signal of the first acceleration sensor 5 [FIG. 3b] to pass only during the period when the gate signal 13 is at the logic level "1", and outputs only the desired blow-through signal 4 as shown in FIG. 3h. Extract as follows. 15
is a peak hold circuit which holds the peak value of the blow-through signal 4 extracted via the gate circuit 14. 16 is an indicator connected to the peak hold circuit 15 output.

Because of this configuration, the gate signal 13 is generated at a time delayed by a predetermined crank angle from the fuel injection timing with the fuel injection timing as a synchronization reference [coincidence detection pulse
_P2 generation time], the logic level is inverted to "1", and the crank angle period during which blow-through signal 4 is generated has elapsed [coincidence detection pulse _P3 generation time]
Since the signal is generated by returning the signal to the logic level "0", a complete synchronization state can be maintained even though the blow-through signal 4 is a high-speed signal. Also,
The repetition period of the count inputs of the first and second preset counters 10 and 11 changes depending on the rotational speed of the internal combustion engine, so even though the fuel injection timing is used as a synchronization standard, the rotational fluctuation of the internal combustion engine The influence can be completely removed, the synchronization state can be maintained completely, and only the blow-through signal 4 can be extracted accurately.

In the above embodiment, a diesel engine was used as an example of the internal combustion engine, but the same method can be applied to a gasoline engine as well.
In the case of a gasoline engine, for example, a pickup coil for detecting ignition timing is provided in place of the second acceleration sensor 6, and the first preset counter 10 starts counting at the ignition timing.

As described above, according to the method of the present invention, a vibration or sound detection sensor is attached to the outside of the exhaust pipe of the internal combustion engine to detect a signal, and at the same time, the fuel injection timing or ignition timing of the internal combustion engine is detected. , to create a gate signal with a predetermined time width for extracting the blow-through signal using the detected fuel injection timing or ignition timing as a synchronization reference signal, and to extract the signal of the predetermined time period of the detection sensor output signal with this gate signal, When detecting the exhaust valve blow-through signal, there is no need to directly connect a high-precision detector such as a rotary encoder to the rotating shaft. Since it can be detected at any time, it is possible to accurately extract the high-speed signal.

Further, according to the apparatus of the present invention, the rotation detection means outputs a signal with a repetition period corresponding to the rotation speed of the internal combustion engine to be inspected, and the rotation detection means outputs the signal at the time when the timing detection signal is generated in the timing detection means. a first preset counter that starts counting the signals and detects that the counted value matches the first preset value; and a first preset counter that starts counting the signals and detects that the counted value matches the first preset value; By creating a gate signal by providing a second preset counter that detects when the count value matches the second preset value, a high-precision detector similar to the method of the present invention can be obtained. Not only can the blow-through signal be accurately extracted without using the blow-through signal, but even if rotational fluctuations occur, the fluctuations can be automatically removed and only the blow-through signal period can be accurately extracted.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of detection signals from the exhaust pipe, FIGS. 2 and 3 show a specific embodiment of the present invention, FIG. 2 is a configuration diagram of an exhaust valve blow-through detection device, and FIG. FIG. 3 is a waveform diagram of the main part of FIG. 2; 1...Combustion signal, 2...Exhaust signal, 3...Valve closing signal, 4...Blow-through signal, 5...First acceleration sensor, 6...Second acceleration sensor, 7...Tachometer, 8...Voltage-frequency converter , 9... Signal processing circuit, 10... First preset counter, 11... Second preset counter, 12... R-S flip-flop, 1
3...Gate signal, 14...Gate circuit,...Fuel injection timing, _P2 , _P3 ...Coincidence detection pulse.

Claims (1)

[Scope of Claims] 1. A vibration or sound detection sensor is attached to the outside of the exhaust pipe of the internal combustion engine to be inspected to detect a signal, and the fuel injection timing or ignition timing of the internal combustion engine is detected, and the detected fuel An internal combustion engine characterized in that a gate signal of a predetermined time width for extracting a blow-through signal is created using injection timing or ignition timing as a synchronization reference signal, and the signal of the detection sensor output signal of the predetermined time width is extracted using this gate signal. Exhaust valve blow-through detection method. 2. A sensor attached to the outside of the exhaust pipe of the internal combustion engine to be inspected to detect vibration or sound; a timing detection means for detecting the fuel injection timing or ignition timing of the internal combustion engine and outputting a timing detection signal; rotation detection means for outputting a signal with a repetition period corresponding to the rotation speed, and counting of the output signal of the rotation detection means at a time when a timing detection signal is generated in the timing detection means, and the count value reaches a first preset value. a first preset counter that detects a match; and when the first preset counter detects a match, starts counting the output signal of the rotation detecting means and detects that the counted value matches the second preset value. A second preset counter to detect, an RS flip-flop whose coincidence detection outputs of the first and second preset counters are set at one side and reset at the other, and this RS flip-flop output signal. and a gate circuit for extracting from the sensor output a signal for a period from the coincidence detection time of the first preset counter to the coincidence detection time of the second preset counter, using the gate signal as a gate signal. Exhaust valve blow-through detection device for internal combustion engines.