JP2013160130A - Control device of internal combustion engine - Google Patents

Abstract

An object of the present invention is to effectively prevent repeated abnormal combustion while reducing the influence on drivability and emission.
When abnormal combustion is detected, abnormal combustion prevention processing is performed in a predetermined number of cycles after the abnormal combustion is detected. The abnormal combustion prevention process is a process for preventing the occurrence of abnormal combustion by setting a fuel injection amount that is different from that during normal operation in which abnormal combustion is not detected. In the present invention, the setting of the fuel injection amount in the abnormal combustion prevention process is varied for each cycle, and the fuel injection is performed so that the second cycle after the abnormal combustion is detected is more effective in preventing abnormal combustion than the other cycles. Set the amount. For example, the fuel injection amount is set to zero in the second cycle after the abnormal combustion is detected, and the fuel injection amount is increased in the other cycles as compared with the normal operation.
[Selection] Figure 8

Description

  The present invention relates to a control device for an internal combustion engine, and in particular, relates to a control device for an internal combustion engine having a function of preventing repeated abnormal combustion.

  Abnormal combustion, such as knocking and pre-ignition, not only lowers the output of the internal combustion engine but also adversely affects its durability. For this reason, preventing the occurrence of abnormal combustion is an important issue in the control of an internal combustion engine, and various solutions have been proposed to date. For example, Patent Document 1 below describes increasing the fuel injection amount when abnormal combustion is detected. Patent Document 8 describes that a fuel cut is performed when abnormal combustion is detected. Other Patent Documents 2-7 also describe techniques related to prevention of abnormal combustion.

JP 2011-163322 A JP 2001-152918 A Japanese Patent Application Laid-Open No. 2004-124887 JP 2010-0777908 A JP 2008-303832 A JP 2011-190729 A JP 2009-030541 A JP 2011-085098 A

  By the way, when abnormal combustion occurs once, abnormal combustion may occur subsequently. This is called repeated abnormal combustion. It is considered that deposits attached to the inside of the cylinder are peeled off due to the occurrence of abnormal combustion, and a part of the deposit remains in the cylinder after the next cycle and becomes an ignition source, thereby causing a series of abnormal combustion. As a method for preventing the occurrence of abnormal combustion, it is effective to increase the fuel injection amount or to perform fuel cut as described above. However, when such a process is continuously performed, there is a contradiction such as a decrease in drivability and emission performance, or an increase in the catalyst bed temperature to accelerate the deterioration. Therefore, how to reduce the influence on drivability and emission performance is a problem in preventing the continuous combustion of abnormal combustion by increasing the fuel injection amount or cutting the fuel.

  The present invention has been made in view of the above problems, and provides a control device for an internal combustion engine that can effectively prevent repeated abnormal combustion while reducing the influence on drivability and emission performance. Objective.

  FIG. 1 is a graph showing the results of examining how the probability that abnormal combustion will occur again changes depending on the number of cycles after the occurrence of abnormal combustion. As described above, the cause of the occurrence of abnormal combustion is the deposit that peeled off at the first abnormal combustion, so the cycle with more peeled deposits remaining in the cylinder, that is, the cycle closer to the first abnormal combustion, the abnormal combustion Is likely to occur again. However, in the next cycle after the first abnormal combustion, that is, the first cycle, although there are many peeling deposits remaining in the cylinder, the probability of abnormal combustion is not so high because the conditions for ignition are not yet established. For this reason, as shown in FIG. 1, the occurrence probability of abnormal combustion increases rapidly in the second cycle, and gradually decreases after the third cycle. That is, the occurrence probability of abnormal combustion peaks in the second cycle after abnormal combustion is detected.

  The present invention has been made based on such knowledge, and the control device provided by the present invention is configured to perform the following operations.

  The control device provided by the present invention detects abnormal combustion for each cycle. When abnormal combustion is detected, abnormal combustion prevention processing is performed in a predetermined number of cycles after the abnormal combustion is detected. The abnormal combustion prevention process means a process for preventing abnormal combustion by setting a fuel injection amount that is different from that during normal operation in which abnormal combustion is not detected. This control device varies the fuel injection amount setting in the abnormal combustion prevention process for each cycle, and the second cycle after the detection of abnormal combustion is such that the effect of preventing abnormal combustion is greater than that of other cycles. Set the injection amount.

  The probability of the occurrence of repeated abnormal combustion is the peak in the second cycle after the first abnormal combustion. Therefore, by setting the fuel injection amount so that the effect of preventing abnormal combustion in this cycle is increased, Combustion of combustion can be effectively prevented. In other cycles where the probability of occurrence of abnormal combustion is relatively low, the effect on drivability and emission performance is reduced by setting the fuel injection amount so that the effect of preventing abnormal combustion is smaller than in the second cycle. can do.

  There are two preferred configurations for the control device provided by the present invention. According to the first embodiment, the control device increases the fuel injection amount from the normal operation after detecting the abnormal combustion, and increases the fuel injection amount in the second cycle after the abnormal combustion is detected. Is larger than other cycles. As the rate of increase in the fuel injection amount is increased, the cooling effect due to the latent heat of vaporization is increased and the effect of preventing abnormal combustion is increased. Therefore, abnormal combustion in the second cycle having a high probability of occurrence can be effectively prevented. .

  On the other hand, according to the second embodiment, the control device sets the fuel injection amount to zero in the second cycle after the abnormal combustion is detected, and increases the fuel injection amount in the other cycles as compared with the normal operation. Making the fuel injection amount zero, that is, fuel cut, is a process that has a greater effect of preventing abnormal combustion than increasing the fuel injection amount. According to this embodiment, not only the abnormal combustion in the second cycle with a high probability of occurrence can be effectively prevented, but also in the next cycle, that is, the third cycle, due to the reduction of the separation deposit in the combustion state that becomes the ignition source. It is also possible to reduce the probability of occurrence of abnormal combustion.

  In each of the above-described embodiments, it is more preferable that the increase rate of the fuel injection amount after the third cycle after the abnormal combustion is detected is made smaller as the later cycle. Since the probability of occurrence of abnormal combustion decreases with later cycles, the influence on drivability and emission performance can be further suppressed by reducing the rate of increase of the fuel injection amount with later cycles.

  In each of the above-described embodiments, the fuel in the cycle in which the fuel injection amount is increased according to the magnitude of knock caused by abnormal combustion or according to the in-cylinder pressure measured when abnormal combustion is detected. It is more preferable to change the increase rate of the injection amount. This is because the amount of deposits to be peeled depends on the scale of abnormal combustion and the magnitude of in-cylinder pressure. It is also possible to estimate the deposit amount adhering to the cylinder and change the fuel injection amount increase rate in the cycle in which the fuel injection amount increase is performed according to the estimated deposit accumulation amount when abnormal combustion is detected. preferable. This is because the probability of occurrence of abnormal combustion changes according to the amount of deposit accumulated in the cylinder.

  According to the present invention, it is possible to effectively prevent repeated abnormal combustion while reducing the influence on drivability and emission performance.

It is a graph which shows the result of having investigated about the probability that abnormal combustion will generate | occur | produce again by the number of cycles after generation | occurrence | production of abnormal combustion. It is a figure which shows the structure of the engine system with which the control apparatus of this invention is applied. It is a figure for demonstrating the fuel-injection control for the continuous combustion prevention of the abnormal combustion by Embodiment 1 of this invention. It is a graph which shows the relationship between the magnitude | size of a knock or in-cylinder pressure, and an increase coefficient. It is a figure which shows the image of the map for calculating the accumulation amount / peeling amount of a deposit from a load and rotation speed. It is a figure which shows the image of the control which estimates the accumulation | storage amount of a deposit from a load and rotation speed. It is a graph which shows the relationship between the accumulation amount of a deposit, and an increase coefficient. It is a figure for demonstrating the fuel-injection control for the continuous combustion prevention of the abnormal combustion by Embodiment 2 of this invention.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described with reference to the drawings.

  FIG. 2 is a diagram showing the configuration of an automobile engine system to which the control device of the present invention is applied in Embodiment 1 and Embodiment 2 described later. An internal combustion engine provided in this engine system is a gasoline engine (hereinafter simply referred to as an engine) 10 with a turbocharger 38.

  The engine 10 includes an intake passage 18 through which air taken into each cylinder flows, and an exhaust passage 20 through which exhaust gas discharged from each cylinder flows. The intake passage 10 is provided with a compressor 38 b of the turbocharger 38. A throttle valve 22 is provided in the intake passage 18 downstream of the compressor 38b. On the other hand, a turbine 38 a of a turbocharger 38 is attached to the exhaust passage 20. In the exhaust passage 20, a catalyst device 24 for purifying exhaust gas is provided downstream of the turbine 38a.

  A piston 12 is disposed inside each cylinder of the engine 10. A combustion chamber 14 is formed by the cylinder inner wall and the piston 12. Each cylinder includes a fuel injection valve 26 that injects fuel into the intake port, an ignition plug 28 that ignites the air-fuel mixture in the combustion chamber 14, an intake valve 30 that opens and closes between the intake passage 18 and the combustion chamber 14, An exhaust valve 32 that opens and closes between the exhaust passage 20 and the combustion chamber 14 is provided. Although only one cylinder is shown in FIG. 1 for convenience, the engine 10 actually includes a plurality of cylinders.

  The engine system includes an ECU (Electronic Control Unit) 50. The ECU 50 is a control device that comprehensively controls the entire engine system. The ECU 50 captures and processes signals from various sensors included in the engine system. Sensors are installed in various parts of the engine system. For example, a crank angle sensor 40 is attached in the vicinity of the crankshaft 16, and an air flow meter 42 is attached at the inlet of the intake passage 18. A knock sensor 44 is attached to the cylinder block of the engine 10, and an in-cylinder pressure sensor 46 is attached to each cylinder. The ECU 50 processes the signals of the acquired sensors and operates the actuators according to a predetermined control program. The actuator operated by the ECU 50 includes a throttle valve 22, a fuel injection valve 26, a spark plug 28, and the like. There are many actuators and sensors connected to the ECU 50 other than those shown in the figure, but the description thereof is omitted in this specification.

  The engine control executed by the ECU 50 in the present embodiment includes fuel injection control for preventing repeated abnormal combustion. Hereinafter, the fuel injection control for this purpose will be referred to as repeated prevention control. In the continuous prevention control of the present embodiment, after an abnormal combustion such as knocking or pre-ignition occurs once, the fuel injection amount is increased from that in the normal operation in which no abnormal combustion occurs, and the inside of the combustion chamber 14 is generated by the latent heat of vaporization. The occurrence of abnormal combustion again is prevented by cooling the. However, simply increasing the fuel injection amount may impair drivability and emission performance, and if the increase in fuel injection amount is suppressed because of this fear, the occurrence of abnormal combustion can be effectively prevented. I can't.

  Therefore, in the continuous prevention control of the present embodiment, as shown in the graph of FIG. 3, the fuel injection amount increase coefficient is changed according to the number of cycles after occurrence of abnormal combustion. The increase coefficient is a coefficient that is multiplied by the basic amount of the fuel injection amount, and indicates an increase ratio of the fuel injection amount. The occurrence of abnormal combustion can be detected from a knock signal captured by the knock sensor 44 or can be detected from the in-cylinder pressure measured by the in-cylinder pressure sensor 46.

  In the graph of FIG. 3, in addition to a curve indicating the relationship between the increase coefficient and the number of cycles after occurrence of abnormal combustion, the probability of occurrence of abnormal combustion for each number of cycles after occurrence of abnormal combustion is also shown. As can be seen from these comparisons, in the continuous prevention control of the present embodiment, the increase coefficient is changed according to the high probability of occurrence of abnormal combustion. The probability of occurrence of abnormal combustion is relatively low in the first cycle after the occurrence of abnormal combustion, rapidly increases in the second cycle, reaches a peak, and gradually decreases after the third cycle. Therefore, the increase coefficient of the fuel injection amount by the continuous prevention control of the present embodiment is suppressed to a relatively small value in the first cycle after the abnormal combustion is detected, and is set to the maximum value in the second cycle. After the first, it is gradually changed to a smaller value. By setting the increase coefficient of the fuel injection amount in this way, it is possible to effectively prevent repeated abnormal combustion while reducing the influence on drivability and emission performance.

  In the repeated prevention control of the present embodiment, the setting of the increase coefficient is changed according to the magnitude of knock caused by abnormal combustion. The magnitude of the knock can be determined from the strength of the knock signal obtained by the knock sensor 44. The magnitude of the knock represents the magnitude of abnormal combustion. The larger the magnitude of abnormal combustion, the greater the amount of deposits that are peeled off, and the greater the amount of deposits peeled, the higher the probability of occurrence of abnormal combustion. Therefore, as shown in FIG. 4, according to the continuous prevention control of the present embodiment, the increase coefficient is changed to a large value as a whole when the magnitude of the knock is large, and the increase coefficient when the magnitude of the knock is small. Is changed to a smaller value overall.

  Note that the setting of the increase coefficient may be changed according to the in-cylinder pressure when abnormal combustion is detected instead of the magnitude of the knock. This is because the greater the in-cylinder pressure at the time of occurrence of abnormal combustion, the greater the amount of deposits that are peeled off, and the higher the probability of occurrence of abnormal combustion. The in-cylinder pressure at the time of occurrence of abnormal combustion can be measured by the in-cylinder pressure sensor 46.

  Further, in the continuous prevention control of the present embodiment, the setting of the increase coefficient is changed according to the accumulated amount of deposit in the cylinder. This is because the more deposits are accumulated in the cylinder, the more deposits are peeled off when the first abnormal combustion occurs, resulting in a higher probability of abnormal combustion. The accumulated amount of deposit can be estimated from the load and rotation speed history of the engine 10.

  The ECU 50 is provided with a deposit accumulation map as shown in FIG. As shown in this map, there are a region where the deposit is accumulated and a region where the deposit is separated in the operation region of the engine 10 defined by the load and the rotational speed. In the deposit accumulation map, the accumulation amount per unit time in the deposit accumulation area is stored in association with the load and the rotation speed, and the separation amount per unit time in the deposit separation area is stored in association with the load and the rotation speed. FIG. 6 is a diagram showing an image of control for estimating the accumulated amount of deposit from the load and the rotational speed. As shown in this figure, the ECU 50 measures the load and the rotational speed at regular time intervals, and calculates the accumulated amount or peeling amount per unit time according to the measured load and rotational speed using the deposit accumulation map. . Then, by accumulating the calculated accumulation amount or peeling amount per unit time, the deposit accumulation amount is constantly updated. According to the continuous prevention control of the present embodiment, as shown in FIG. 7, when the deposit accumulation amount is large, the increase coefficient is changed to a large value as a whole, and when the deposit accumulation amount is small, the increase coefficient is generally small. Changed to a value.

  The ECU 50 has a map that associates the value of the increase coefficient with the number of cycles, the magnitude of knock (or in-cylinder pressure), and the accumulated amount of deposit, and until a predetermined number of cycles elapse after the abnormal combustion is detected. Using this map, the value of the increase coefficient used for calculating the fuel injection amount is determined.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to the drawings.

  This embodiment is different from the first embodiment in the content of the continuous prevention control. In the continuous prevention control of the present embodiment, as shown in the graph of FIG. 8, the fuel injection amount is made zero, that is, the fuel cut is performed in the second cycle after the abnormal combustion is detected. In the second cycle after occurrence of abnormal combustion, the probability of occurrence of abnormal combustion is maximized. However, if fuel cut is performed, occurrence of abnormal combustion in that cycle can be reliably prevented. However, although the fuel cut is more effective in preventing abnormal combustion than increasing the fuel injection amount, if it is continued for a long time, the catalyst device 24 is deteriorated and the drivability is greatly affected. Therefore, the execution of the fuel cut is limited to the second cycle in which the occurrence probability of abnormal combustion is maximized, and in other cycles, the occurrence of abnormal combustion is prevented by increasing the fuel injection amount.

  In the first cycle and after the third cycle after the abnormal combustion is detected, the increase coefficient of the fuel injection amount is set to a larger value than in the normal operation, as in the first embodiment. However, the value of the increase coefficient in the third cycle after the abnormal combustion is detected is set to a value smaller than that of the first embodiment. This is because the fuel cut is executed in the second cycle, so that the separation deposit in the combustion state that becomes the ignition source is reduced in the third cycle. In the graph of FIG. 8, in addition to the curve showing the relationship between the increase coefficient and the number of cycles after occurrence of abnormal combustion, the probability of occurrence of abnormal combustion for each number of cycles when the fuel cut is executed in the second cycle is also shown. It is shown. As can be seen from the comparison between FIG. 8 and FIG. 3, in the third cycle, the probability of abnormal combustion is the second highest after the second cycle, but by performing the fuel cut in the second cycle, The probability of occurrence of combustion can be greatly reduced.

  As described above, according to the repetitive prevention control of the present embodiment, not only the abnormal combustion in the second cycle with a high probability of occurrence can be effectively prevented by the fuel cut, but also the separation deposit in the combustion state that becomes the ignition source As a result of the decrease, the probability of occurrence of abnormal combustion in the third cycle, which has the highest probability of occurrence of abnormal combustion next to the second cycle, can also be lowered. If the occurrence probability of abnormal combustion decreases, the increase in the fuel injection amount can be suppressed correspondingly, so that the influence on drivability and emission performance can be further reduced.

  In the repeated prevention control of the present embodiment, as in the first embodiment, 1 according to the magnitude of knock caused by abnormal combustion or according to the in-cylinder pressure when abnormal combustion is detected. The setting of the increase coefficient in the cycle and the third and subsequent cycles is changed. Further, similarly to the first embodiment, the setting of the increase coefficient in the first cycle and the third and subsequent cycles is also changed according to the accumulated amount of deposit in the cylinder.

Others.
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. Further, the present invention can be applied to an engine other than a gasoline engine, for example, a diesel engine, and can be applied not only to a supercharged engine but also to a naturally aspirated engine.

10 Gasoline Engine 14 Combustion Chamber 26 Fuel Injection Valve 44 Knock Sensor 46 In-Cylinder Pressure Sensor 50 ECU

Claims (7)

Detection means for detecting abnormal combustion;
When abnormal combustion is detected, in a predetermined number of cycles after abnormal combustion is detected, processing for preventing occurrence of abnormal combustion by setting a fuel injection amount different from that during normal operation in which abnormal combustion is not detected ( And an abnormal combustion prevention means for carrying out abnormal combustion prevention processing)
The abnormal combustion prevention means varies the fuel injection amount setting in the abnormal combustion prevention processing for each cycle, and the second cycle after the abnormal combustion is detected has a greater effect of preventing abnormal combustion than the other cycles. A control apparatus for an internal combustion engine, wherein the fuel injection amount is set as described above.   The abnormal combustion preventing means sets the fuel injection amount to zero in the second cycle after the abnormal combustion is detected, and increases the fuel injection amount in other cycles than in the normal operation. The internal combustion engine control device described.   The abnormal combustion preventing means increases the fuel injection amount from the normal operation after detecting the abnormal combustion, and increases the fuel injection amount increase ratio from the other cycles in the second cycle after the abnormal combustion is detected. 2. The control apparatus for an internal combustion engine according to claim 1, wherein   4. The internal combustion engine according to claim 2, wherein the abnormal combustion preventing means reduces the increase rate of the fuel injection amount after the third cycle after the abnormal combustion is detected, as the subsequent cycle becomes smaller. Control device.   5. The fuel injection amount increase ratio in a cycle in which the fuel injection amount is increased according to the magnitude of a knock caused by the abnormal combustion. 5. A control device for an internal combustion engine according to claim 1. The control device further includes means for measuring an in-cylinder pressure,
The abnormal combustion preventing means changes a fuel injection amount increase ratio in a cycle in which the fuel injection amount is increased in accordance with an in-cylinder pressure measured when abnormal combustion is detected. Item 5. The control device for an internal combustion engine according to any one of Items 2 to 4. The control device further comprises means for estimating the amount of deposit accumulated in the cylinder,
3. The abnormal combustion preventing means changes a fuel injection amount increase rate in a cycle in which the fuel injection amount increase is performed according to an estimated deposit accumulation amount when abnormal combustion is detected. The control device for an internal combustion engine according to any one of claims 1 to 6.

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