JP6212953B2 - Engine misfire detection device - Google Patents

Description

  The present invention relates to an engine misfire detection apparatus.

  In recent years, detection of misfire has become necessary as OBD (self-diagnosis diagnosis) of diesel engines. Therefore, a technique for detecting misfire by detecting a change in engine rotation speed due to misfire has been put into practical use (for example, see Patent Document 1).

JP 2005-299511 A

  By the way, the engine rotation speed is detected by, for example, measuring the tooth period of the crank angle sensor. However, if the engine rotation speed becomes high, the tooth period becomes shorter, and the detection resolution of the engine rotation speed change is the engine resolution. There are restrictions depending on the clock of the period measurement function of the control unit. Therefore, the detection resolution of the engine rotation speed change is lowered in the high rotation range, and it is difficult to accurately detect the combustion state in each cylinder.

  An object of the present invention is to provide an engine misfire detection device capable of accurately detecting misfire in the entire operation range.

  In order to achieve the above object, an engine misfire detection apparatus according to the present invention extracts vibration components in a predetermined high frequency range from vibration detection means for detecting vibrations of the engine and vibration signals detected by the vibration detection means. And vibration energy calculation means for calculating vibration energy by integrating the extracted vibration components, and misfire determination means for determining misfire from the magnitude of vibration energy calculated by the vibration energy calculation means. And

  Further, the apparatus further comprises ignition timing calculation means for extracting a vibration component in a low frequency range lower than the high frequency range from the vibration signal detected by the vibration detection means, and calculating an ignition timing from the extracted vibration component. The misfire determination means may determine misfire based on a delay of the ignition timing calculated by the ignition timing calculation means with respect to a reference time.

  Further, the misfire determination means may determine misfire using information on both vibration energy calculated by the vibration energy calculation means and ignition timing calculated by the ignition timing calculation means.

  According to the engine misfire detection apparatus of the present invention, misfire can be detected with high accuracy in the entire operation range.

It is the schematic which shows the misfire detection apparatus of the engine which concerns on one Embodiment of this invention. It is a time chart explaining calculation of the vibration energy by the engine misfire detection apparatus concerning one embodiment of the present invention. It is a time chart explaining calculation of the ignition timing by the engine misfire detection apparatus which concerns on one Embodiment of this invention.

  Hereinafter, based on FIGS. 1-3, the misfire detection apparatus of the engine which concerns on one Embodiment of this invention is demonstrated. The same parts are denoted by the same reference numerals, and their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  A diesel engine (hereinafter simply referred to as an engine) 10 is an in-line four-cylinder engine having a plurality of cylinders # 1 to # 4. The engine 10 may be a multi-cylinder engine other than four cylinders or a single cylinder engine.

  The injector 20 is provided corresponding to each cylinder of the engine 10 and directly injects high-pressure fuel supplied from the common rail 11 into the combustion chamber of each cylinder. The fuel injection amount and injection timing of the injector 20 are determined by lifting the core valve in accordance with the pulse width (time width) of the injection instruction signal input from the electronic control unit (hereinafter referred to as ECU) 40 to the electromagnetic solenoid. It is controlled by opening and closing the hole.

  The vibration acceleration sensor 30 is a knock sensor or the like that can detect vibration generated in the engine 10 due to combustion in each cylinder, for example, one between the # 1 cylinder and the # 2 cylinder, There are two in total between # 4 cylinders. The vibration of the engine 10 detected by the vibration acceleration sensor 30 is output to the electrically connected ECU 40. In the present embodiment, the vibration acceleration sensor 30 is provided in the cylinder block CB of the engine 10, but a cylinder head or the like as long as the vibration generated in the engine 10 due to combustion in each cylinder can be detected. It can also be provided on other parts. A sensor may be provided corresponding to each cylinder, and the vibration is detected by being transmitted through the cylinder block CB. Therefore, even a multi-cylinder engine can be handled by a single sensor.

  The ECU 40 performs various controls of the engine 10 and includes a known CPU, ROM, RAM, input port, output port, and the like. In order to perform these various controls, output signals from the vibration acceleration sensor 30, the engine rotation sensor (crank angle sensor) 31, the accelerator opening sensor 32, and the like are input to the ECU 40.

  In addition, the ECU 40 includes a vibration energy calculation unit 41, an ignition timing calculation unit 42, and a misfire determination unit 43 as some functional elements. In the present embodiment, these functional elements are described as being included in the ECU 40, which is an integral piece of hardware. However, any one of these functional elements may be provided in separate hardware.

  The vibration energy calculation unit 41 calculates vibration energy (vibration energy) generated in the engine 10 by combustion in each cylinder based on the vibration signal measured by the vibration acceleration sensor 30 provided in the engine 10. More specifically, the vibration signal detected by the vibration acceleration sensor 30 is filtered by a bandpass filter having a passband characteristic of, for example, 5 to 20 kHz, and vibration components in a high frequency range are detected from the vibration signal detected by the vibration acceleration sensor 30. Extract. Then, the integration (for example, absolute value integration or square integration) of the extracted vibration component in the high frequency range is calculated, and the value (integration value) obtained by the integration is set as vibration energy E (see FIG. 2). When a misfire occurs, the combustion energy decreases, and the vibration energy also decreases accordingly. Therefore, the misfire can be determined from the magnitude of the vibration energy. The integrated value is reset to 0 at, for example, the expansion bottom dead center.

  The ignition timing calculation unit 42 calculates the timing (ignition timing) at which combustion occurs in each cylinder based on the vibration signal measured by the vibration acceleration sensor 30 provided in the engine 10. More specifically, the vibration signal detected by the vibration acceleration sensor 30 is filtered by a low-pass filter of about 2 kHz, for example, and the vibration component in the low frequency range is extracted from the vibration signal detected by the vibration acceleration sensor 30. Since the extracted vibration component in the low frequency range has a waveform highly correlated with the combustion pressure waveform in each cylinder, the time (or crank angle) corresponding to the peak point at which the shape of the waveform changes is set in each cylinder. Let timing (ignition timing) T when combustion occurs (see FIG. 3). When misfire occurs, the ignition timing is delayed from the reference time, and therefore misfire can be determined from the delay of the ignition timing with respect to the reference time.

  The misfire determination unit 43 determines misfire using information on both the vibration energy calculated by the vibration energy calculation unit 41 and the ignition timing calculated by the ignition timing calculation unit 42. More specifically, the vibration energy calculated by the vibration energy calculation unit 41 and the delay of the ignition timing calculated by the ignition timing calculation unit 42 are respectively expressed as the reference state is “1.0” and the degree of misfire increases. Convert to a smaller coefficient. Moreover, after weighting each converted coefficient, the coefficients are added together. For example, it can be considered that the weighting of the coefficient due to the magnitude of the vibration energy is decreased and the weighting of the coefficient due to the delay of the ignition timing is increased as the operating state of the engine 10 becomes higher.

  When the misfire occurs, the above coefficient becomes small. Therefore, when the combined coefficient falls below a reference coefficient (threshold value) set according to the operating state of the engine 10, it is determined that misfire has occurred. Therefore, the ECU 40 stores a reference coefficient map (not shown) indicating the relationship between the operating state of the engine 10 (engine rotational speed Ne, fuel injection amount Q) and the reference coefficient.

  Next, the function and effect of the misfire detection device according to the present embodiment will be described.

  In the misfire detection apparatus of the present embodiment, the vibration acceleration sensor 30 provided in the engine 10 is used, the energy due to combustion in each cylinder is regarded as vibration energy, and misfire is detected from the magnitude of the vibration energy. That is, the misfire detection device of the present embodiment detects engine vibration that is easy to detect even in the high rotation range of the engine 10, compared to a technique for detecting the combustion state in each cylinder from changes in engine rotation speed. The combustion state in the cylinder is reliably detected.

  Therefore, according to the misfire detection device of the present embodiment, misfire can be accurately detected in the entire operation region by using the vibration signal detected by the vibration acceleration sensor 30 for misfire determination.

  In addition, this invention is not limited to the above-mentioned embodiment, In the range which does not deviate from the meaning of this invention, it can change suitably and can implement.

  For example, the engine 10 is not limited to a diesel engine, and can be widely applied to other engines such as a gasoline engine. The misfire determination can also be performed using information on engine speed change in addition to information on vibration energy and ignition timing.

10 Engine 30 Vibration acceleration sensor (vibration detecting means)
40 ECU
41 Vibration energy calculation unit (vibration energy calculation means)
42 Ignition timing calculation unit (Ignition timing calculation means)
43 misfire determination unit (misfire determination means)

Claims (3)

Vibration detecting means for detecting engine vibration;
Vibration energy calculation means for extracting vibration components in a predetermined high frequency range from the vibration signal detected by the vibration detection means, and calculating vibration energy by integrating the extracted vibration components;
Ignition timing calculation means for extracting a vibration component in a low frequency range on a lower frequency side than the high frequency range from the vibration signal detected by the vibration detection means, and calculating an ignition timing from the extracted vibration component;
Misfire determination means for determining misfire using information on both the magnitude of vibration energy calculated by the vibration energy calculation means and a delay with respect to a reference time of the ignition timing calculated by the ignition timing calculation means ,
The misfire determination means converts the magnitude of vibration energy and the delay in ignition timing into coefficients, weights each converted coefficient, adds the coefficients, and compares the combined coefficients with a reference coefficient. A misfire detection device for an engine characterized by determining misfire. The coefficient is a coefficient that decreases as the degree of misfire increases,
The engine misfire detection device according to claim 1, wherein the misfire determination unit determines that a misfire has occurred when a combined coefficient falls below a reference coefficient . The engine misfire determination unit according to claim 1 or 2, wherein the misfire determination means decreases the weighting of the coefficient due to the magnitude of vibration energy and increases the weighting of the coefficient due to a delay in the ignition timing as the engine operating state becomes higher . Misfire detection device.

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