JP2018091262A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new knock control device of an internal combustion engine capable of suppressing wrong detection of knock, even in performing fuel injection at an injection timing overlapped to a knock detection window.SOLUTION: When an injection mode in which an injection timing of a fuel injection valve 5 is not overlapped to a knock detection window Wind is switched to an injection mode in which the injection timing is overlapped to the knock detection window, a BGL value, a knock determination threshold value, or the BGL value and the knock determination threshold value are set large. Thus wrong detection of knock can be suppressed even when the injection timing of the fuel injection valve 5 is overlapped to the knock detection window Wind.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an internal combustion engine control apparatus, and more particularly to an internal combustion engine control apparatus having a knock control function used in a direct injection type internal combustion engine that directly injects fuel into a cylinder.

  In general, a spark ignition internal combustion engine that compresses an air-fuel mixture and ignites with an ignition plug is equipped with a knock control device that suppresses the occurrence of knock. As is well known, this knock control device performs feedback control of the ignition timing to an ignition timing at which no knock occurs based on a knock signal of a predetermined level output from the knock sensor.

  In the knock detection method in this knock control device, a signal of a knock sensor attached to a cylinder block of an internal combustion engine is mainly defined within a predetermined crank angle range so as to be captured during a knock generation interval. AD conversion is performed in a section (hereinafter referred to as a knock detection window), and a background level (hereinafter referred to as a BGL value) is obtained by filtering the AD conversion value when no knock occurs, for example, by weighted averaging. The calculated BGL value is compared with the AD conversion value at the time of occurrence of the knock, and when the “ratio” or “difference” exceeds a predetermined value (hereinafter referred to as a knock determination threshold), it is determined that there is a knock. Techniques are known.

  By the way, the AD conversion value of the knock sensor signal when knock does not occur means so-called background noise, and this background noise is mainly used for valve seating of valve systems such as an intake valve and an exhaust valve. Although it is classified into noise, other mechanical noises, vibration noise due to combustion, etc., the influence of the seating noise of the intake valve is particularly large. In addition, in an internal combustion engine equipped with a variable valve mechanism, the valve seating noise generation position fluctuates in order to change the opening / closing phase of the intake valve, and when the valve seating noise occurs within the knock detection window, There is a great difference in the accuracy of knock detection between cases where this is not the case.

  For this reason, for example, in Japanese Patent Application Laid-Open No. 2004-11626 (Patent Document 1), the magnitude of the intake valve seating noise and the degree of influence due to the occurrence position are accurately estimated, and accurate knocking is performed based on the ratio with the estimated knock signal. It is determined whether or not detection is possible, and if it is determined to be possible, knock control is executed, and if it is determined to be impossible, the ignition timing is set so that knocking does not occur reliably, thereby reducing the influence of seating noise as much as possible. Propose that.

JP 2004-11626 A

  Recently, in order to reduce fuel consumption and exhaust gas harmful components, direct injection internal combustion engines that directly inject fuel into cylinders have been used. In this direct injection type internal combustion engine, the number of fuels injected during one combustion cycle is divided into one to a plurality of times (for example, one to four injections). It has been broken. This is because, for example, combustion by a homogeneous mixture (fuel is uniformly distributed in the cylinder) and combustion by a stratified mixture (a rich mixture is distributed around the spark plug) are performed separately.

  When the fuel is injected in a plurality of times, the injection timing is set from the intake stroke to the compression stroke. For example, when generating a homogeneous air-fuel mixture, the fuel is injected once or twice in the intake stroke. Further, when generating a stratified mixture, fuel is injected once or twice in the intake stroke, and fuel is injected once or twice in the subsequent compression stroke. Of course, a plurality of injections may be performed for other purposes. Furthermore, the injection timing in the intake stroke and the compression stroke is also appropriately controlled by the state of the internal combustion engine, for example, the engine temperature (= cooling water temperature), the engine load, and the like.

  As described above, in a direct injection type internal combustion engine, the number of fuel injections during one combustion cycle may be divided into one to a plurality of times only from the intake stroke or from the intake stroke to the compression stroke. It has been broken. Since the fuel injection valve injects fuel into the cylinder, the injected fuel pressure is set high, and the set pressure of the valve closing spring of the fuel injection valve is also set high accordingly. Therefore, the valve closing noise of the fuel injection valve also affects the knock determination.

  Here, knock occurs in a section where the air-fuel mixture in the cylinder is burned. Generally, the knock detection window is set to the crank angle range in the first half of the expansion stroke in which the air-fuel mixture is burned. Yes. Usually, the knock detection window is about 60 ° from 30 ° to 90 ° after ignition. The knock detection window is set for each cylinder, the occurrence of knock is detected for each cylinder, and the ignition timing is feedback-controlled based on this.

  For this reason, in the “in-line four-cylinder internal combustion engine” in which the combustion cycle is performed in the order of the first cylinder → the third cylinder → the fourth cylinder → the second cylinder, for example, fuel is injected in the intake stroke of the first cylinder. If so, the knock detection window is open in the fourth cylinder. At this time, since the knock detection window of the fourth cylinder and the fuel injection timing of the intake stroke of the first cylinder are set so as not to overlap, the valve closing noise of the fuel injection valve of the intake stroke of the first cylinder is the fourth cylinder. Are not captured in the knock detection window.

  However, when fuel is injected in the first half of the compression stroke following the intake stroke of the first cylinder, the knock detection window is opened in the first half of the expansion stroke of the second cylinder. At this time, the knock detection window set in the first half of the expansion stroke of the second cylinder and the fuel injection timing in the first half of the compression stroke of the first cylinder overlap, so that the closing noise of the fuel injection valve in the compression stroke of the first cylinder is It will be taken into the knock detection window of the second cylinder.

  Further, in the “horizontally opposed four-cylinder internal combustion engine” in which the combustion cycle is performed in the order of the first cylinder → the third cylinder → the second cylinder → the fourth cylinder, fuel is injected in the intake stroke of the first cylinder. In this case, the knock detection window is opened in the second cylinder. At this time, in the horizontally opposed four-cylinder internal combustion engine, the first cylinder and the third cylinder are in the same bank, the second cylinder and the fourth cylinder are in the same bank, and a knock sensor is provided in each bank. Yes. For this reason, the valve closing noise of the fuel injection valve in the intake stroke of the first cylinder is hardly transmitted to the bank of the second cylinder and is taken into the knock detection window of the second cylinder and has no adverse effect. It is.

  However, when fuel is injected in the first half of the compression stroke following the intake stroke of the third cylinder, the knock detection window is opened in the first half of the expansion stroke of the first cylinder. At this time, since the first cylinder and the third cylinder are in the same bank, the knock detection window set in the first half of the expansion stroke of the third cylinder overlaps with the fuel injection timing in the first half of the compression stroke of the first cylinder. The closing noise of the fuel injection valve in the compression stroke of the three cylinders is captured in the knock detection window of the first cylinder.

  Therefore, the AD conversion values of the knock sensor signals taken in the section of the knock detection window of the second cylinder (four in-line cylinders) and the first cylinder (four horizontally opposed cylinders) are the first cylinder (in-line four cylinders) and the first cylinder, respectively. The closing noise of the fuel injection valve in the first half of the compression stroke of the three cylinders (horizontally opposed four cylinders) is reflected, which may cause erroneous detection of knock. Of course, there is a possibility that knocking may be erroneously detected in other cylinders as well. This will be described in more detail with reference to FIG.

  An object of the present invention is a novel device capable of suppressing knock detection error even when fuel injection is performed at an injection timing overlapping with a knock detection window when fuel injection is performed a plurality of times in one combustion cycle. Another object of the present invention is to provide a control device for an internal combustion engine.

  A feature of the present invention is that when the injection timing is switched to the injection mode overlapping with the knock detection window, the BGL value, the knock determination threshold value, or the BGL value and the knock determination threshold value are set to be large.

  According to the present invention, even if the injection timing of the fuel injection valve overlaps with the knock detection window, erroneous detection of knock can be suppressed.

1 is a system configuration diagram of an internal combustion engine including a knock control device according to an embodiment of the present invention. It is a block diagram which shows the internal structure of the knock control apparatus which becomes one Embodiment of this invention. It is explanatory drawing explaining the relationship between the fuel-injection timing in a 4-cylinder internal combustion engine, and a knock detection window. It is a control block diagram which calculates the BGL value of the knock control apparatus which becomes one Embodiment of this invention. It is a flowchart figure which shows the control flow of the knock control apparatus which becomes one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments, and various modifications and application examples are included in the technical concept of the present invention. Is also included in the range.

  FIG. 1 shows a system configuration of an internal combustion engine according to an embodiment of the present invention. The internal combustion engine is an in-line 4-cylinder internal combustion engine in which a variable valve mechanism is provided on an intake camshaft and an exhaust camshaft, and the first to fourth cylinders are in the same bank. In the in-line four-cylinder internal combustion engine of the present embodiment, the combustion cycle is performed in the order of first cylinder → third cylinder → fourth cylinder → second cylinder. The internal combustion engine includes a control device 1 including a microprocessor (MPU), an input / output circuit (I / OLSI), a storage element (ROM, RAM), and the like. The ignition timing, variable valve mechanism, etc. can be comprehensively controlled.

  The control device 1 includes an injector drive circuit that drives a fuel injection valve 5 that directly injects fuel into a cylinder of the internal combustion engine, and injects fuel at a predetermined number of required injections in one combustion cycle of the internal combustion engine 1. A multi-stage injection control function for controlling the injector drive circuit is provided. The reason why the number of fuels injected during one combustion cycle is divided into one to a plurality of times (for example, one injection to four injections) is as follows. This is because the combustion by the stratified gas and the combustion by the stratified mixture are separately performed.

  When the fuel is injected in a plurality of times, the injection timing is set from the intake stroke to the compression stroke. For example, in the case of generating a homogeneous air-fuel mixture, the fuel is injected once or twice in the intake stroke alone. Further, when the stratified mixture is generated, the fuel is injected once or twice in the intake stroke, and the fuel is injected once or twice in the compression stroke.

  Here, the injection timing in the intake stroke and the compression stroke is set to a predetermined crank angle, and the injection timing is controlled by this predetermined crank angle. The injection timing is appropriately controlled not only by homogeneous combustion and stratified combustion, but also by the state of the internal combustion engine, for example, engine temperature (= cooling water temperature), engine load, and the like.

  The control device 1 detects the crank angle (position) and the number of rotations with the crank angle sensor 3, and matches the air amount directly or indirectly measured by the airflow sensor 4a or the intake pipe pressure sensor 4b. The fuel is injected from the fuel injection valve 5 and the ignition coil 6 is driven at the charging timing calculated from the charging efficiency calculated from the air amount or the ignition timing map set by the axis of the load value and the rotational speed. Ignite the air-fuel mixture in the cylinder. The ignition timing is controlled to be delayed by a predetermined value every time a knock occurs based on a knock signal detected by a common knock sensor 22 in the first to fourth cylinders to avoid knock. ing.

  The variable valve mechanism is mainly composed of a hydraulic control mechanism 8 that controls the phase of the cam angle with respect to the crank angle, and the cam angle is detected by the cam angle sensor 7. The target advance angle values (intake valve opening timing: IVO and exhaust valve closing timing: EVC) are searched from the charging efficiency calculated from the air amount or the phase map set by the load value and the rotation speed axis, and the crank angle The drive signal (for example, duty signal) of the solenoid valve of the hydraulic control mechanism 8 is feedback-controlled so that the actual advance value detected by the cam angle becomes the target phase value retrieved from the map.

  The horizontally opposed 4-cylinder internal combustion engine has substantially the same configuration, but in the horizontally opposed 4-cylinder internal combustion engine, the first cylinder and the fourth cylinder are in the same bank, and the second cylinder and the third cylinder are the same. The difference is that a knock sensor is provided in each bank. In the horizontally opposed four-cylinder internal combustion engine, the combustion cycle is performed in the order of the first cylinder → the third cylinder → the second cylinder → the fourth cylinder. Such an internal combustion engine system is well known and will not be described further.

  Next, an outline of the basic configuration and operation of the knock control device according to the embodiment of the present invention will be briefly described with reference to the block diagram shown in FIG. First, the knock control device 10 basically includes a knock detection unit 11, a knock control unit 12, and an ignition timing control unit 13.

  The knock detection unit 11 includes a knock detection window opening / closing timing calculation unit 14 that sets a knock detection window, a knock signal processing unit 15 that processes a signal of the knock sensor, and a knock index calculation unit 16 that determines whether or not a knock has occurred and its magnitude. Etc. Further, the ignition timing control unit 13 stores an ignition timing map 17 in which basic ignition timing is stored with the rotation speed as one axis, charging efficiency and load as the other axis, and the basic ignition timing of the ignition timing map 17. It includes an ignition timing calculation unit 18 that corrects by various parameters (water temperature change, rotation speed change, throttle opening change, etc.).

  The ignition timing map 17 of the ignition timing control unit 13 is supplied with charging efficiency information or load information obtained from the air flow sensor 4a or the intake pipe pressure sensor 4b, and the rotational speed information obtained from the crank angle sensor 3. Is entered. Further, an ignition signal to the ignition coil 6 is output from the ignition timing calculation unit 18, and ignition is performed at a predetermined crank angle before and after the compression top dead center.

  The knock detection window opening / closing timing calculation unit 14 of the knock detection unit 11 calculates the timing for opening / closing the knock detection window from the angular position signal from the crank angle sensor 3, and is generally a predetermined value from the compression top dead center. The knock sensor signal is captured over an angular range. Generally, it is set in the range of 30 ° to 90 ° after ignition as described above, and this knock detection window is sent to the knock signal processing unit 15. The adoption of the variable valve mechanism 8 also tends to enlarge the knock detection window, and the ratio of taking in the valve closing noise of the fuel injection valve 5 described above increases.

  The knock signal processing unit 15 captures a knock sensor signal for each cylinder, and captures a knock sensor signal over a knock detection window section. The signals for “no knock” and “no knock” are AD-converted together. In the case of “no knock”, a weighted average process (filtering) is performed, a BGL value is calculated for each cylinder, and the calculated BGL value is compared with a knock signal in the case of “with knock”. The “ratio” or “difference” is determined.

  The knock index calculation unit 16 calculates a knock index from the “ratio” or “difference” sent from the knock signal processing unit 14, and sets a knock determination threshold value (a slice level and a slice level in FIG. 2). This is a calculation of a knock index indicating how much knock has occurred compared to (described). This knock index is sent to the knock control unit 12 and converted into a retard amount of the ignition timing. This retard amount is sent to the ignition timing calculation unit 18, and the ignition timing calculation unit 18 corrects the basic ignition timing in the retard direction.

  Therefore, as described in the operation explanation shown in the lower right of FIG. 2, when the knock determination threshold is exceeded, the ignition timing is retarded by a predetermined amount, and thereafter, if the knock does not occur, the ignition timing is gradually advanced. When the knock determination threshold is exceeded again, the ignition timing is retarded by a predetermined amount. By repeating this, the ignition timing is feedback-controlled so that a constant knock level is obtained. The ignition timing feedback control can be performed simultaneously for all cylinders or for each cylinder, but in this embodiment, the ignition timing feedback control is performed for each cylinder.

  Note that the basic knock detection suitability is that a knock detection window is set so that the knock signal at the time of knock occurrence in a steady operation state can be surely taken and AD conversion can be performed, and the AD conversion value and BGL value of the knock signal are set. The knock index obtained based on the “ratio” or “difference” of the knock is equal to or less than a predetermined value at the time of knock occurrence (determining the presence of knock) and greater than a predetermined value when no knock occurs (knock detection without knock) The knock determination threshold value may be set so that

  In the knock control device 10 as described above, the relationship between the fuel injection timing of the fuel injection valve 5 and the knock detection window will be described with reference to FIG. FIG. 3 shows the progress of each stroke when the combustion cycle is performed in the order of the first cylinder → the third cylinder → the second cylinder → the fourth cylinder in the horizontally opposed four-cylinder internal combustion engine. Further, as described above, the first cylinder and the third cylinder are the same bank, and the second cylinder and the fourth cylinder are the same bank.

  FIG. 3 also shows an example of an in-line four-cylinder internal combustion engine. In this case, the combustion cycle is performed in the order of the first cylinder → the third cylinder → the fourth cylinder → the second cylinder. Compared to the cylinder, the second cylinder is the fourth cylinder, and the fourth cylinder is the second cylinder. In the inline 4-cylinder internal combustion engine, the first to fourth cylinders are in the same bank.

  Next, in FIG. 3, in the horizontally opposed four-cylinder internal combustion engine, the injection timing and knock detection window of the fuel injection valve 5 in a state where the first cylinder advances from the intake stroke to the compression stroke (region shown in gray). The relationship will be described.

  Here, knock occurs in a section where the air-fuel mixture in the cylinder is burned, and the knock detection window Wind is set to the crank angle range in the first half of the expansion stroke in which combustion is performed. On the other hand, the injection timing of the fuel injection valve 5 has various timings as described above, but an injection timing section Iinj for injecting in the intake stroke and an injection timing section Cinj injecting in the compression stroke are set.

  Further, in the present embodiment, the injection timing interval Iinj of the intake stroke is set between the middle of the intake stroke and near the end thereof, and the injection timing interval Cinj of the compression stroke is set from the first half to the middle of the compression stroke. ing. And the injection timing of the fuel injection valve 5 is appropriately controlled between these sections. However, in the horizontally opposed four-cylinder internal combustion engine, as described above, the bank with the cylinder of the intake stroke and the bank with the cylinder of the expansion stroke in which the knock detection window is opened are different. There is no problem even if it is set.

  Therefore, in the horizontally opposed four-cylinder internal combustion engine in which the combustion cycle is performed in the order of the first cylinder → the third cylinder → the second cylinder → the fourth cylinder, the fuel is supplied only in the injection timing section Iinj of the intake stroke of the first cylinder. When the fuel is being injected (first injection mode), the knock detection window Wind is opened in the second cylinder. At this time, since the knock detection window Wind of the second cylinder and the fuel injection timing section Iinj of the intake stroke of the first cylinder do not overlap, the closing noise of the fuel injection valve 5 of the intake stroke of the first cylinder is the knock of the second cylinder. It is not captured in the detection window Wind. Further, even if the fuel injection timing interval Iinj of the intake stroke of the first cylinder is set wide and the knock detection window Wind of the second cylinder overlaps the fuel injection timing interval Iinj of the intake stroke of the first cylinder, respectively. Therefore, the valve closing noise in the intake stroke of the first cylinder is not affected.

  In an in-line four-cylinder internal combustion engine in which the combustion cycle is performed in the order of the first cylinder → the third cylinder → the fourth cylinder → the second cylinder, fuel is injected only in the injection timing section Iinj of the intake stroke of the first cylinder. If it is (hereinafter referred to as the first injection mode), the knock detection window Wind is open in the fourth cylinder. At this time, since the knock detection window Wind of the fourth cylinder and the fuel injection timing section Iinj of the intake stroke of the first cylinder are set so as not to overlap, the valve closing noise of the fuel injection valve 5 of the intake stroke of the first cylinder is set. Is not taken into the knock detection window Wind of the fourth cylinder.

  However, in a horizontally opposed four-cylinder internal combustion engine, when fuel is injected at a plurality of injection timings (hereinafter referred to as a second injection mode), the fuel injection timing section Iinj of the intake stroke of the third cylinder continues. Thus, fuel is injected in the injection timing section Cinj of the compression stroke. For this reason, the knock detection window Wind is opened in the first cylinder, but the first cylinder and the third cylinder are in the same bank.

  Therefore, since the knock detection window Wind of the first cylinder in the same bank overlaps with the fuel injection timing section Cinj of the compression stroke of the third cylinder, the valve closing noise of the fuel injection valve of the compression stroke of the third cylinder is the knock of the first cylinder. It will be taken into the detection window Wind.

  In the in-line four-cylinder internal combustion engine, the knock detection window Wind is opened in the second cylinder. At this time, the knock detection window Wind in the second cylinder and the fuel injection in the compression stroke of the first cylinder are performed. Since the timing intervals Cinj overlap, the valve closing noise of the fuel injection valve in the compression stroke of the first cylinder is taken into the knock detection window Wind of the second cylinder.

  As described above, the AD conversion value of the knock sensor signal taken in the section of the knock detection window Wind of the fourth cylinder (four horizontally opposed cylinders) or the second cylinder (four in-line cylinders) is injected in the compression stroke of the first cylinder. The closing noise of the fuel injection valve 5 is reflected, which may cause a false detection of knock. Of course, in the second injection mode in which fuel is injected at a plurality of injection timings in other cylinders as well, there is a risk of erroneous detection of knock as can be seen from FIG.

  For example, a filter is provided to remove a high-frequency component from the vibration waveform signal when a signal is taken from the knock sensor 2. The filter also inputs a higher frequency component than the knock frequency as a knock signal, and the high frequency region corresponds to the frequency of the fuel injection valve.

  For this reason, when the injection mode of the fuel injection valve 5 is switched to the second injection mode, the injection timing Cinj in the compression stroke overlaps with the knock detection window Wind, so that the second injection mode is switched. If the signal level of the knock sensor signal suddenly increases and the resulting knock index is the same as that at the time of knock occurrence, there is a risk that the knock determination threshold will be exceeded and it will be erroneously determined that there is a knock. is there.

  Therefore, in the present embodiment, when the injection timing of the fuel injection valve 5 is switched to the injection timing section Cinj that overlaps the knock detection window Wind, the BGL value, the knock determination threshold, or the BGL value and the knock determination threshold are set large. It is a configuration. According to this, even if the injection timing section Cinj of the fuel injection valve overlaps with the knock detection window Wind, erroneous detection of knock can be effectively suppressed.

  FIG. 4 shows a schematic control concept of the knock detection unit 11 according to the present embodiment. In the “first injection mode” state in which injection is performed once or twice only during the injection timing interval Iinj of the intake stroke, the closing noise of the fuel injection valve 5 is taken into the knock detection window set in the first half of the expansion stroke. Therefore, knock detection is performed using a normal BGL value calculation and a knock determination threshold.

  In addition to the state in which injection is performed once or twice in the injection timing interval Iinj of the intake stroke, the state of “second injection mode” in which injection is performed once or twice in the injection timing interval Cinj of the subsequent compression stroke When the normal switching is performed, the followability becomes slow. Therefore, the BGL value is a fixed value having a predetermined amount, or a BGL value obtained by adding an offset value having a predetermined amount to the BGL value. To obtain a new BGL value.

  Therefore, the new BGL value calculated in the “second injection mode” is rapidly different from the BGL value in the “first injection mode” in which the injection timing is set only in the injection timing interval Iinj of the intake stroke. It becomes large and followability is ensured. Further, since the “ratio” or “difference” between the BGL value and the AD conversion value of the knock sensor signal is also a new large BGL value, an appropriate knock index can be obtained.

  Further, the knock determination threshold value to be compared with the knock index is “second injection mode” with respect to the knock determination threshold value of “first injection mode” in which the injection timing is set in the injection timing interval Iinj of the intake stroke. Then, the new knock determination threshold value is set to be large in order to correct the valve closing noise of the fuel injection valve 5, and this makes it possible to perform an appropriate knock determination.

  Next, a specific control flow will be described based on FIG. The control flow shown in FIG. 5 is started every predetermined time, for example, every 10 ms, and is started using a compare match interrupt of a microcomputer counter provided in the control device 1.

<< Step S10 >>
In step S10, the required number of injections of the fuel injection valve 5 of each cylinder is captured. This number of injections is the total number of injections in the injection timing interval Iinj of the intake stroke and the injection timing interval Cinj of the compression stroke. Hereinafter, for convenience, the “single injection mode” corresponds to the “first injection mode” in which injection is performed only in the injection timing interval Iinj of the intake stroke, and the “multiple injection mode” is the injection timing interval of the intake stroke. Description will be made assuming that it corresponds to the “second injection mode” in which injection is performed once in total and twice in each of Iinj and the injection timing interval Cinj of the compression stroke. As described above, the injection may be performed a plurality of times in each of the injection timing interval Iinj of the intake stroke and the injection timing interval Cinj of the compression stroke. When the acquisition of the required number of injections is completed in step S10, the process proceeds to step S11.

<< Step S11 >>
In step S11, when the required number of injections is greater than “1”, here “2”, and when the required number of injections is greater than “1”, here “2” to “1”. The offset value of the BGL value is calculated in accordance with the switching at the time of switching to. Since the required number of injections is captured as information for each cylinder, switching between the single injection mode and the multiple injection mode can be determined for each cylinder.

  As described with reference to FIG. 4, this offset value may be a predetermined fixed value (= BGL value), or may be a predetermined offset value that is added to or subtracted from the current BGL value. In this embodiment, an offset value for addition or subtraction is obtained. Note that the offset value is changed depending on the rotation speed, and the offset value is determined to increase as the rotation speed increases. When this offset value is obtained, the process proceeds to step S12.

<< Step S12 >>
In step S12, knock determination threshold values corresponding to the single injection mode and the multiple injection mode are calculated from the determination threshold map. The knock determination threshold is set larger in the multiple injection mode than in the single injection mode. The knock determination threshold is stored in a determination threshold map with the rotation speed and load as axes. The value of the knock determination threshold is changed depending on the rotation speed and the load, and the value of the knock determination threshold is determined to increase as the rotation speed and the load increase. When the knock determination threshold is obtained, the process proceeds to step S13.

<< Step S13 >>
In step S13, it is determined whether or not the mode is switched from the single injection mode to the multiple injection mode. This determination can be made by monitoring the change in the required number of injections. For example, when the required number of injections is changed from “1” to “2”, it can be determined that the single injection mode is switched to the multiple injection mode. If it is determined in this step that the single injection mode is switched to the multiple injection mode, the process proceeds to step S14, and if it is determined that the single injection mode is not switched to the multiple injection mode, the step is performed. The process proceeds to S15.

<< Step S14 >>
In step S14, since it is determined that the single injection mode is switched to the multiple injection mode, the offset value obtained in step S11 is added to the current BGL value (the BGL value in the single injection mode). It is set as a new BGL value, and is set by switching to a new knock determination threshold value in the multiple injection mode obtained in step S12. These new BGL values and new knock determination threshold values are used in the knock detection unit 11 shown in FIG.

  In the multiple injection mode, the injection is performed once in the injection timing interval Iinj of the intake stroke and is injected once in the injection timing interval Cinj of the subsequent compression stroke, so that the closing by the injection in the injection timing interval Iinj of the intake stroke is performed. Valve noise is generated. However, in the case of the horizontally opposed four cylinders, the banks are different as described above, and in the case of the in-line four cylinders, since there is no cylinder in which the knock detection window Wind is open, there is no substantial problem. Is.

  As described above, in a cylinder that has been determined to switch from the single injection mode to the multiple injection mode, the BGL value and the knock determination threshold value are switched to values larger than those in the single injection mode, thereby injecting the compression stroke. It is possible to reduce the knock erroneous determination by suppressing the influence that the signal level of the knock sensor signal rapidly increases due to the closing noise of the fuel injection valve 5 in the timing section Cinj being captured in the knock detection window. When this process is completed, the process proceeds to step S15.

<< Step S15 >>
In step S15, it is determined whether or not the mode is switched from the multiple injection mode to the single injection mode. If it is not determined in step 13 that the single injection mode is switched to the multiple injection mode, and it is not determined in this step S15 that the switch is from the multiple injection mode to the single injection mode, each mode is continued. As a result, the program returns to return and waits for the next activation timing.

  Similarly, if step S14 is completed and it is not determined that the mode is switched from the multiple injection mode to the single injection mode, it is determined that the multiple injection mode is continuously executed and the process returns to wait for the next start timing. It will be. On the other hand, the process proceeds to step S16 where it is determined that the mode is switched from the multiple injection mode to the single injection mode.

<< Step S16 >>
In step S16, since it is determined that the mode is switched from the multiple injection mode to the single injection mode, the offset value obtained in step S11 is subtracted from the current BGL value (BGL value in the multiple injection mode). It resets as a new BGL value (BGL value in the single injection mode), and switches to the new knock determination threshold value in the single injection mode obtained in step S12. These new BGL values and new knock determination threshold values are used in the knock detection unit 11 shown in FIG. In this case, since it is the single injection mode, the valve closing noise of the fuel injection valve 5 in the injection timing section Iinj of the intake stroke is not captured in the knock detection window.

  Here, in steps S11 and S12, the BGL value and the knock determination threshold are set larger in the multiple injection mode than in the single injection mode, but either the BGL value or the knock determination threshold is injected once. It is also possible to set the multiple injection mode larger than the mode.

  As described above, in the cylinder for which switching from the multiple injection mode to the single injection mode is determined in step S16, the BGL value and knock determination threshold of the multiple injection mode are set to the BGL value of the single injection mode and the knock determination. By switching to the threshold value, the knock determination process is not performed while the BGL value and the knock determination threshold value are maintained at the high values of the multiple injection mode, so that erroneous determination of knock is suppressed.

  As described above, according to the present invention, when the injection timing is switched to the injection mode overlapping with the knock detection window, the BGL value, the knock determination threshold value, or the BGL value and the knock determination threshold value are set large. According to this, even if the injection timing of the fuel injection valve overlaps with the knock detection window, erroneous detection of knock can be suppressed.

  In addition, this invention is not limited to above-described embodiment, Various modifications are included. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to one having all the configurations described. Further, a part of the configuration of an embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of an embodiment. In addition, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  DESCRIPTION OF SYMBOLS 1 ... Control apparatus, 2 ... Knock sensor, 3 ... Crank angle sensor, 4a ... Air flow sensor, 4b ... Intake pipe pressure sensor, 5 ... Fuel injection valve, 6 ... Ignition coil, 7 ... Cam angle sensor, 8 ... Hydraulic control mechanism DESCRIPTION OF SYMBOLS 10 ... Knock control apparatus, 11 ... Knock detection part, 12 ... Knock control part, 13 ... Ignition timing control part, 14 ... Knock detection window opening / closing timing calculating part, 15 ... Knock signal processing part, 16 ... Knock index calculating part, 17 ... ignition timing map, 18 ... ignition timing calculating section.

Claims (5)

Based on a signal from a knock sensor attached to an internal combustion engine having a plurality of cylinders, a background level (hereinafter referred to as a BGL value) when no knock occurs for each cylinder, and when a knock occurs Knock determination means for detecting knock by comparing the signal of the knock sensor;
When the knock determination means detects the occurrence of knock, ignition timing calculation means for retarding the occurrence of knock by retarding the ignition timing by a predetermined value;
A first injection mode in which an injection timing of a fuel injection valve that directly injects fuel into the plurality of cylinders is set to an injection timing interval Iinj of an intake stroke; and an injection timing interval of the fuel injection valve that is an injection timing interval of an intake stroke In a control device for an internal combustion engine comprising Iinj and a fuel injection control means for switching and controlling the second injection mode set in the injection timing section Cinj of the subsequent compression stroke,
The knock determination means captures a signal from the knock sensor in a knock detection window set in the first half of the expansion stroke for each cylinder, and makes a “ratio” or “difference” between the BGL value and the signal of the knock sensor. A function of calculating a knock index on the basis of the knock index and comparing the knock index with a predetermined knock determination threshold,
Furthermore, the knock determination means is configured to switch between the first injection mode and the second injection mode when the fuel injection control means switches between the first injection mode and the second injection mode. A control device for an internal combustion engine, wherein the control is switched between the BGL value and the knock determination threshold value corresponding to each. The control apparatus for an internal combustion engine according to claim 1,
When the first injection mode is switched to the second injection mode, the knock determination means determines the BGL value of the second injection mode as compared with the BGL value of the first injection mode. The knock determination threshold value in the second injection mode is set to a larger value than the knock determination threshold value in the first injection mode. Engine control device. The control apparatus for an internal combustion engine according to claim 2,
When the first injection mode is switched to the second injection mode, the knock determination means adds a predetermined offset value to the BGL value of the first injection mode to add the second injection mode. A control device for an internal combustion engine, characterized in that it is set as the BGL value. Based on a signal from a knock sensor attached to an internal combustion engine having a plurality of cylinders, a background level (hereinafter referred to as a BGL value) when no knock occurs for each cylinder, and when a knock occurs Knock determination means for detecting knock by comparing the signal of the knock sensor;
When the knock determination means detects the occurrence of knock, ignition timing calculation means for retarding the occurrence of knock by retarding the ignition timing by a predetermined value;
The first injection mode in which the injection timing of the fuel injection valve that directly injects fuel into the plurality of cylinders is set at least once in the injection timing interval Iinj of the intake stroke, and the injection timing of the fuel injection valve is the intake stroke. And a fuel injection control means for switching between and controlling the second injection mode set at least once in the injection timing section Iinj of the subsequent compression stroke and the injection timing section Cinj of the compression stroke. ,
The knock determination means takes in a signal from the knock sensor in a knock detection window set in the first half of the expansion stroke of each cylinder, and makes a “ratio” or “difference” between the BGL value and the knock sensor signal. A function of calculating a knock index on the basis of the knock index and comparing the knock index with a predetermined knock determination threshold,
Further, the knock determination means determines the BGL value of the second injection mode or the knock determination when the injection timing of the fuel injection valve is switched from the first injection mode to the second injection mode. A control apparatus for an internal combustion engine, characterized in that a threshold value, or the BGL value and the knock determination threshold value are set larger than in the first injection mode. The control apparatus for an internal combustion engine according to claim 4,
When the first injection mode is switched to the second injection mode, the knock determination means adds a predetermined offset value to the BGL value of the first injection mode to add the second injection mode. A control device for an internal combustion engine, characterized in that it is set as the BGL value.

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