JP2008215142A - Knocking detection device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid wrong determination of knocking occurrence due to change in valve timing of an engine valve. <P>SOLUTION: In an engine in which a knocking occurrence interval where knocking occurrence is predicted in a combustion stroke in each cylinder is at least overlapped with a variable range of a close timing of the engine valve of a variable valve timing mechanism, the knocking occurrence interval and a detection delay period from the close timing to detection of seating noise by a knocking sensor are included in a knocking detection interval. Thus, even when the close timing is changed, since a background level including seating noise all the time is calculated, determination failure of knocking occurrence by the seating noise can be prevented. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for detecting knocking in an internal combustion engine provided with a variable valve mechanism that varies a valve timing of an engine valve.

Patent Document 1 describes a knock control in which the knock intensity is determined by counting the number of times when the peak value of the output of the knock sensor exceeds the determination reference value, and the ignition timing is retarded when the occurrence of knocking is determined. ing.
JP 07-279712 A

  By the way, the output of the knocking sensor is sampled in a knocking detection section set based on a section in which knocking is predicted to occur, but in an internal combustion engine having a variable valve mechanism that makes the valve timing of the engine valve variable, Depending on the advance / retard angle change of the valve timing, the seating timing (close timing) of the engine valve may be within the knocking detection interval or may be out of the knocking detection interval.

For example, when the seating noise is generated outside the knocking detection section with the change of the closing timing of the engine valve, the knocking intensity detected by the knocking sensor is stepwise. As a result, the occurrence of knocking is erroneously detected.
Generally, the moving average value of the detected values of knocking intensity is set as the background level, and the occurrence of knocking is determined when the detected value of knocking intensity exceeds the background level + threshold value.

For this reason, under conditions where seating noise continues to occur within the knocking detection interval for sampling the sensor output, the background level increases by the amount of seating noise, avoiding erroneous determination of knocking due to seating noise. it can.
However, immediately after the seating noise is generated in the knocking detection section immediately after the seating noise is generated outside the knocking detection section, the background level is an appropriate value in the state where the seating noise is generated. Therefore, the occurrence of knocking is erroneously determined due to the occurrence of seating noise.

  The present invention has been made in view of the above problems, and in an internal combustion engine equipped with a variable valve mechanism, knock detection of an internal combustion engine that can avoid erroneous determination of occurrence of knocking due to a change in valve timing of the engine valve. An object is to provide an apparatus.

Therefore, according to the first aspect of the present invention, the knocking detection period for sampling the output of the knocking sensor is the knocking generation period in which the occurrence of knocking is predicted in the combustion stroke of each cylinder, and the closing timing of the engine valve that overlaps each combustion stroke. And a closing timing that is variable by a variable valve mechanism.
According to the above invention, even if the closing timing of the engine valve changes, the closing timing does not deviate from the knocking detection interval, and the seating noise at the closing timing that is variable by the variable valve mechanism is always within the knocking detection interval. Will occur.

Therefore, knocking detection can be performed based on the state in which seating noise occurs in the knocking detection section, and even if the valve timing is changed, the occurrence of knocking is not erroneously determined by the seating noise.
According to a second aspect of the present invention, the knocking detection section is a fixed section including the entire variable range of the closing timing by the variable valve mechanism.

According to the above invention, even if the closing timing is changed by the variable valve mechanism, at least the valve closing after the change is made within the knocking detection section, and engine seating noise is generated within the knocking detection section. Thus, occurrence of knocking vibration exceeding the seating noise can be detected.
Therefore, with a simple configuration, it is possible to prevent the occurrence of knocking from being erroneously determined due to seating noise even if the valve timing is changed.

According to a third aspect of the present invention, the knocking detection section is variably set according to a change in the closing timing of the engine valve by the variable valve mechanism.
According to the above invention, the minimum width section that can include the knocking occurrence section and the closing timing is set as the knocking detection section according to the valve timing at that time.
Therefore, in order to avoid erroneous determination due to seating noise, it is possible to prevent an excessively long knocking detection interval from being set, reduce a calculation load such as frequency analysis, and maintain the knocking detection accuracy at a high level.

In the invention according to claim 4, the knocking detection section includes a knocking generation section, a closing timing of the engine valve, and a predetermined section immediately after the closing timing.
According to the above invention, the delay period from when the engine valve is closed to when the seating noise is actually generated and detected by the knocking sensor can be included in the knocking detection section together with the knocking generation section.

Therefore, even if the closing timing is changed by the variable valve mechanism, it is possible to set a knocking detection section in which seating noise can be reliably detected by the knocking sensor, and to stably prevent erroneous determination of knocking occurrence. .
In the invention according to claim 5, as the variable valve mechanism, an intake side variable valve mechanism that varies the valve timing of the intake valve and an exhaust side variable valve mechanism that varies the valve timing of the exhaust valve are individually provided. The start of the knocking detection interval is determined based on the earlier of the intake valve closing timing and the exhaust valve closing timing, and the knocking detection is performed based on the later of the intake valve closing timing and the exhaust valve closing timing. Determine the end of the leg.

According to the above invention, both the intake valve closing timing and the exhaust valve closing timing are included in the knocking detection interval even when the closing timing is variable for both the intake valve and the exhaust valve. become.
Accordingly, it is possible to avoid erroneous determination of occurrence of knocking due to seating noise of the intake valve, and at the same time, it is possible to avoid erroneous determination of occurrence of knocking due to seating noise of the exhaust valve.

Embodiments of the present invention will be described below.
FIG. 1 is a system configuration diagram of an internal combustion engine for a vehicle in the embodiment.
In FIG. 1, an internal combustion engine 101 is an in-line four-cylinder spark ignition gasoline engine, and an intake pipe 102 of the internal combustion engine 101 is provided with an electronically controlled throttle 104 that opens and closes a throttle valve 103b by a throttle motor 103a. The

Then, air is sucked into the combustion chamber 106 through the electronic control throttle 104 and the intake valve 105.
An electromagnetic fuel injection valve 131 is provided in each intake port 130 upstream of the intake valve 105 of each cylinder.
The fuel injection valve 131 injects fuel toward the intake valve 105 when driven to open by an injection pulse signal from the control unit 114.

The fuel injection valve 131 may be an in-cylinder direct injection engine that injects fuel directly into the combustion chamber 106.
The fuel sucked into the combustion chamber 106 mixed with air is ignited and burned by spark ignition by the spark plug 151.
Each ignition plug 151 is directly attached with an ignition coil 152 with a built-in power transistor, and an ignition control signal for controlling on / off of the power transistor is output from the control unit 114, thereby igniting each cylinder. The timing is controlled individually.

The combustion exhaust in the combustion chamber 106 is discharged to the exhaust pipe through the exhaust valve 107, purified by the front catalytic converter 108 and the rear catalytic converter 109, and then released into the atmosphere.
The intake valve 105 and the exhaust valve 107 are opened and closed by cams provided on the intake camshaft 111 and the exhaust camshaft 110, respectively, but by changing the rotational phase of the camshafts 110 and 111 with respect to the crankshaft 120. In addition, variable valve timing mechanisms 156 and 157 (variable valve operating mechanisms) are provided for changing the valve timings of the intake valve 105 and the exhaust valve 107 while the operating angles are constant.

  As the variable valve timing mechanism (VVT) 156, 157, the hydraulic pressure supply / discharge to / from the advance hydraulic chamber and the retard hydraulic chamber formed by the vanes as disclosed in Japanese Patent Laid-Open No. 2006-300018 is performed. A mechanism for changing the rotational phase of the camshaft by control, a mechanism for changing the rotational phase of the camshaft by friction braking of an electromagnetic clutch, or the like as disclosed in Japanese Patent Application Laid-Open No. 2003-278514 can be used. However, it is not limited to these variable valve timing mechanisms.

In addition, an electromagnetically driven valve that opens and closes the engine valve by the attractive force of the electromagnet without using a cam, a mechanism that switches the cam that drives the engine valve, and a variable lift mechanism that changes the operating angle with the lift amount of the engine valve are variably operated. The variable valve mechanism may be a mechanism that can change at least the closing timing of the engine valve.
In this embodiment, the intake valve 105 and the exhaust valve 107 are provided with variable valve timing mechanisms 156 and 157 (variable valve operating mechanisms), respectively, and the valve timing is variable. Any one of the valve timings may be variable.

The variable valve timing mechanisms 156 and 157 are controlled by the control unit 114 according to engine operating conditions such as engine load and engine speed.
An electric fuel pump 136 is built in the fuel tank 135, and the fuel (gasoline) in the fuel tank 135 is pumped toward the fuel injection valve 131 by driving the fuel pump 136.

The distribution pipe 137 that distributes the fuel discharged from the fuel pump 136 to each fuel injection valve 131 is provided with a fuel pressure sensor 138 so that the fuel pressure detected by the fuel pressure sensor 138 becomes the target fuel pressure. The discharge amount (drive voltage) of the fuel pump 136 is feedback controlled by the control unit 114.
The control unit 114 incorporates a microcomputer, and the electronic control throttle 104, the fuel injection valve 131, the fuel pump 136, the power transistor built-in ignition coil 152, the variable valve timing, by arithmetic processing based on detection signals from various sensors. The mechanisms 156 and 157 are controlled.

A variable valve control unit that controls the variable valve timing mechanisms 156 and 157 can be provided separately from the control unit 114.
As the various sensors, in addition to the fuel pressure sensor 138, an accelerator opening sensor 116 that detects the depression amount (accelerator opening) of an accelerator pedal operated by a driver, and an air flow meter 115 that detects an intake air flow rate Q of the engine 101. A crank angle sensor 117 that detects the rotational position of the crankshaft 120, a throttle sensor 118 that detects the opening TVO of the throttle valve 103b, a water temperature sensor 119 that detects the coolant temperature of the engine 101, and an upstream side of the front catalyst 108. An air-fuel ratio sensor 121 for detecting the air-fuel ratio based on the oxygen concentration in the exhaust gas, a knocking sensor 122 for detecting vibration of the engine 101 when knocking occurs by a piezoelectric element, and the like are provided.

As the knock sensor 122, each cylinder may be provided with a washer-type piezoelectric element that is attached to a portion where the spark plug 151 is attached to the internal combustion engine 101, as disclosed in JP-A-2001-115886.
The washer-type piezoelectric element can simultaneously detect the knocking vibration and the pressure in the cylinder.

Here, the control unit 114 calculates the engine rotational speed Ne based on the detection signal from the crank angle sensor 117, and the basic injection from the engine rotational speed Ne and the intake air flow rate Q detected by the air flow meter 115. The pulse width Tp is calculated.
The basic injection pulse width Tp is corrected by an air-fuel ratio feedback correction coefficient calculated based on a comparison between the detection result of the air-fuel ratio sensor 121 and the target air-fuel ratio, various increase correction coefficients, and the like. A typical injection pulse width Ti is calculated.

When the final injection pulse width Ti is calculated, an injection pulse signal having the injection pulse width Ti is output to each fuel injection valve 131 in accordance with the stroke of each cylinder.
The control unit 114 calculates a basic ignition timing (basic ignition advance value) ADVb from the basic injection pulse width Tp representing the engine load and the engine rotational speed Ne.
In the present embodiment, the ignition timing is indicated by an advance angle from the compression top dead center.

On the other hand, the presence or absence of knocking is determined from the output of the knocking sensor 122, and when the occurrence of knocking is detected, the correction value ADVh of the basic ignition timing ADVb is corrected to the retarded side (corrected to the decreasing side), and knocking is performed. When non-occurrence of occurrence is detected, the correction value ADVh is corrected to the advance side (corrected to the increase side).
Then, the correction value ADVh is added to the basic ignition timing ADVb, the addition result is set as the final ignition timing ADV, and the ignition coil 152 is energized based on the ignition timing ADV (the power transistor is turned on / off). By controlling (timing), ignition is performed in the vicinity of the maximum advance value that does not cause knocking.

Here, the knocking detection based on the output of the knocking sensor 122 is performed as follows.
First, the output signal of the knocking sensor 122 is sampled in a predetermined knocking detection interval set during the combustion stroke of each cylinder.
The frequency of the sampled signal is analyzed to detect the intensity of the knocking vibration in the frequency range, while the weighted average value (moving average value) of the detected intensity is set as the background level BGL. The occurrence of knocking is determined when the detected intensity is stronger than the added value (determination value) of BGL and a threshold value.

The frequency range of the knocking vibration can be made variable according to the engine speed, and the threshold can be individually set for each cylinder.
The knocking detection section is set based on a knocking generation section in which knocking is predicted to occur in the combustion stroke of each cylinder. In the engine 101 of the present embodiment including the variable valve timing mechanisms (VVT) 156 and 157, The knocking occurrence interval and the closing timing of the intake valve 105 and the exhaust valve 107 which are variable by the variable valve timing mechanisms 156 and 157 have a correlation as shown in FIG.

In the four-cylinder engine 101 of the present embodiment, the ignition order is set in the order of the first cylinder → the third cylinder → the fourth cylinder → the second cylinder.
As shown in FIG. 2, in the engine 101 according to the present embodiment, the knocking occurrence section is a section of approximately 10 deg to 50 deg (ATDC 10 deg to 50 deg) after the compression top dead center of each cylinder.

  On the other hand, for example, the intake valve 105 of the third cylinder is closed after the compression top dead center of the first cylinder (during the combustion stroke). The closing timing thereof is determined by the variable valve timing mechanism 156 by the ATDC 20 deg at the most advanced angle position. To the most retarded angle range of ATDC 70 deg., When the intake valve 105 of the third cylinder is closed within the knocking occurrence section of the first cylinder, and when the third cylinder passes after the knocking occurrence section of the first cylinder has passed. The intake valve 105 may be closed.

Further, for example, the exhaust valve 107 of the fourth cylinder is closed after the compression top dead center of the first cylinder (during the combustion stroke). The closing timing of the exhaust valve 107 is ATDC 10 deg at the most advanced angle position by the variable valve timing mechanism 157. And the exhaust valve 107 of the fourth cylinder is always closed within the knocking occurrence section of the first cylinder.
However, the knocking occurrence section and the variable range of the closing timing of the intake / exhaust valves are merely examples, and it is apparent that the present invention can be applied to an angle range other than these or an engine other than four cylinders. It is.

Here, if the knocking occurrence section is used as it is as the knocking detection section, the problem shown in FIG. 3 occurs.
For example, when the closing timing of the intake valve 105 is later than ATDC 50 deg which is the final stage of the knocking occurrence section, noise due to the seating of the intake valve 105 is detected by the knocking sensor 122 outside the knocking detection section, The seating noise of the intake valve 105 is irrelevant to the detection of the knocking intensity and the calculation of the background level BGL (see FIG. 3A).

Therefore, in this case, even if the frequency of the seating noise is close to the frequency of the knocking vibration, the occurrence of knocking is not erroneously determined by the seating noise of the intake valve 105.
However, from the above state, the closing timing of the intake valve 105 is advanced in accordance with changes in the engine operating conditions, the intake valve 105 is closed within the knocking occurrence section, and the intake valve 105 is closed within the knocking generation section. When the seating noise is picked up by the knocking sensor 122, the seating noise of the intake valve 105 is not sampled until then, and the background level BGL does not include the influence of the seating noise of the intake valve 105. The intake valve 105 seating noise is erroneously determined as an increase in knocking strength due to the occurrence of knocking (see FIG. 3B).

Therefore, in this embodiment, the knocking detection section is set as shown in FIG. 4 so that the occurrence of knocking is not erroneously determined due to the seating noise.
As described above, in the present embodiment, the knocking occurrence section where knocking is predicted to occur in the combustion stroke of each cylinder is ATDC 10 deg to 50 deg, the variable timing range of the exhaust valve 105 is ATDC 10 deg to 40 deg, and the intake valve If the variable range of the closing timing of 107 is ATDC 20 deg to 70 deg, the knocking detection section includes all of these sections, and is a predetermined angle (for example, 10 deg) further than the most retarded position of the closing timing of the intake valve 105. The angular position (ATDC 80 deg) that has just passed is set to ATDC 10 deg to 80 deg.

  That is, the earliest timing between the closing timing of the intake valve 105 and the closing timing of the exhaust valve 107 is a state in which the exhaust valve 107 is closed at ATDC 10 deg. If the initial stage is set to the initial stage, the intake / exhaust valve is not closed earlier than this, and if the initial stage is set to ATDC 10 deg, the knocking occurrence section and the closing timing can be included.

On the other hand, the latest timing between the closing timing of the intake valve 105 and the closing timing of the exhaust valve 107 is a state in which the intake valve 105 is closed at ATDC 70 deg. This is a timing later than the end of the knocking occurrence section. Based on this, the end of the knocking detection interval is determined.
If the knocking detection period is set as described above, the knocking generation period is included, so that knocking vibration can be reliably sampled, and the closing timing of the intake valve 105 and the exhaust valve 107 are controlled by the variable valve timing mechanisms 156 and 157. Even if the closing timing is changed, the closing timing is always included in the knocking detection interval.

  Moreover, even when the intake valve 105 is closed at ATDC 70 deg, which is the slowest closing timing overlapping the combustion stroke, there is a margin of 10 deg until the end of the knocking detection section, and seating noise is actually generated from the closing timing. Even when there is a delay time until the knocking sensor 122 detects the seating noise, the knocking sensor 122 detects the seating noise within the knocking detection section.

That is, even when the closing timing of the intake valve 105 and the closing timing of the exhaust valve 107 are changed by the variable valve timing mechanisms 156 and 157, the closing timing is always included in the knocking detection section, and seating noise at the closing timing is generated. It is always picked up and sampled by the knocking sensor 122 within the knocking detection section.
When the closing timing of the exhaust valve 107 is advanced by more than ATDC 10 deg, which is the start of the knocking occurrence section, the most advanced position of the closing timing of the exhaust valve 107 may be set as the start of the knocking detection section. it can.

  Further, even when the most advanced position of the closing timing of the exhaust valve 107 is advanced from ATDC 10 deg which is the start of the knocking occurrence section, the difference is slight, and the exhaust valve 107 is at the most advanced position. Even if the seating noise is picked up by the knocking sensor 122 after becoming the knocking occurrence section, the start of the knocking occurrence section can be used as the start of the knocking detection section.

  As described above, if the knocking detection interval is set, even if the closing timing of the intake valve 105 and the closing timing of the exhaust valve 107 are changed by the variable valve timing mechanisms 156 and 157, the intake valve 105 and the exhaust valve 107 are controlled. Since the seating noise is always sampled within the knocking detection interval and the background level BGL is always calculated under the seating noise generation condition, the occurrence of knocking is not erroneously determined by the seating noise.

When the variable range of the closing timing overlaps with the knocking occurrence section, attempting to perform knocking detection in a knocking detection section that is narrower than the knocking occurrence section that does not always include the closing timing reduces the knocking occurrence detection system. End up.
On the other hand, if a range wider than the knocking occurrence interval including the knocking occurrence interval and the variable range of the closing timing is set as the knocking detection interval, all of the knocking occurrence intervals are included in the knocking detection interval, and the knocking detection is performed. Even if the closing timing is not included or included in the section and the closing timing is changed, knocking detection is always performed in a state in which seating noise is included, so that knocking can be detected with high accuracy.

FIG. 5 shows a control block diagram in a case where knocking detection is performed with a certain section including the knocking occurrence section and the entire variable range of the closing timing as the knocking detection section as described above.
The output of the knocking sensor 122 is A / D converted by the A / D converter 501 every predetermined minute time, and the operation of the A / D converter 501 is controlled based on the knocking detection interval. It is.

That is, the RAM 502 stores in advance the crank angle from the top dead center TDC to the start of the knocking detection section (knocking detection section offset) and angle data indicating the width of the knocking detection section, and the detection section calculation unit In 503, a detection section is calculated from these data.
As described above, the offset and detection interval width data are set in advance so as to be an interval including the knocking occurrence interval and the entire variable range of the closing timing.

The sampling unit 504 controls the A / D converter 501 so that the output of the knocking sensor 122 in the knocking detection section is read from the data of the knocking detection section, the crank angle signal, the cam angle signal, and the like. To do.
The output of the knocking sensor 122 in the knocking detection section read by A / D conversion by the A / D converter 501 is subjected to frequency analysis by the frequency analysis unit 505, and the strength (decibel) of the knocking frequency is obtained. The detection result is weighted average (moving average) by the BGL calculation unit 506 to calculate the background level BGL.

Then, the S / N ratio calculation unit 507 calculates the ratio (S / N ratio) between the magnitude of the knocking frequency at that time and the background level BGL.
Knocking strength calculating section 508 adds the S / N ratio obtained for each frequency included in the knocking frequency range, and outputs the result as the knocking strength.
The threshold setting unit 510 sets a threshold value for each cylinder from the engine speed calculated by the rotation speed calculation unit 511 and the cylinder discrimination result by the cylinder discrimination unit 512, and the knocking determination unit 509 sets the threshold and the knocking. When the knocking strength exceeds the threshold, the occurrence of knocking is determined.

Based on the knocking determination by the knocking determination unit 509, the retard control unit 513 performs advance / retard angle control of the ignition timing ADV.
By the way, if the knocking detection interval is set as described above, it is not necessary to change the knocking detection interval with respect to the change of the closing timing, the knocking detection interval can be given as a fixed value, and simple control is possible. is there.

  However, in an operating condition in which the closing timing of the intake valve 105 is advanced, the knocking generation period has passed, and the output of the knocking sensor 122 continues to be sampled even after the seating noise of the intake valve 105 has occurred. Therefore, it is preferable to avoid as much as possible from the viewpoint of knocking detection accuracy that the calculation load is unnecessarily large and the output of the knocking sensor 112 is not sampled outside the knocking occurrence section.

Therefore, the knocking detection section can be made variable according to the closing timing which is made variable by the variable valve timing mechanisms 156 and 157, and a second embodiment having such a configuration will be described below.
The flowchart of FIG. 6 shows the calculation of the knocking detection interval in the second embodiment.
In step S701, the closing timing IVC of the intake valve 105 at that time is detected. The detection of the closing timing IVC includes detection values of operating conditions used to control the variable valve timing mechanisms 156 and 157, control targets of the variable valve timing mechanisms 156 and 157, detection values of the rotational phase of the camshafts 110 and 111, and the like. It can be done from.

In step S702, a time delayed by a predetermined angle (10 deg) from the closing timing IVC of the intake valve 105 detected in step S101 is calculated.
The predetermined angle is an angle corresponding to a delay time from the closing timing until the seating noise is detected by the knocking sensor 122, and the angle position calculated in step S702 is the seating noise generated at the closing timing IVC at that time. Is substantially equivalent to the angular position detected by the knocking sensor 122.

  In the above description, the angle (detection delay period) from the closing timing IVC until the seating noise is detected by the knocking sensor 122 is assumed to be 10 deg, and the closing timing IVC + 10 deg is calculated in step S102. The time until the seating noise is detected by the knocking sensor 122 is predetermined, the crank angle corresponding to the predetermined time is obtained from the engine speed at that time, and the crank angle can be added to the closing timing IVC.

In step S703, it is determined whether the timing of the closing timing IVC + 10 deg is later than the preset end of the knocking occurrence section.
When the timing of the closing timing IVC + 10 deg is later than the end of the knocking occurrence interval, the seating noise of the intake valve 105 is detected by the knocking sensor 122 after the knocking occurrence interval ends.

Therefore, the process proceeds to step S704, where the end of the knocking detection section is set to the closing timing IVC + 10 deg instead of the end of the knocking generation section, and the knocking generation section and the generation timing of the seating noise of the intake valve 105 are set in the knocking detection section. It should be included (see FIG. 7).
On the other hand, when the timing of the closing timing IVC + 10 deg is earlier than the end of the knocking occurrence section, the seating noise of the intake valve 105 is detected by the knocking sensor 122 in the knocking generation section.

Therefore, the process proceeds to step S705, and the end of the knocking occurrence section is set as the end of the knocking detection section (see FIG. 8).
As described above, if the knocking detection period is set, the knocking detection period including the knocking generation period and the occurrence timing of the seating noise of the intake valve 105 is set by extending the period as much as necessary with respect to the knocking generation period. Can be made.

Therefore, it is possible to reduce a calculation load such as frequency analysis and to improve knocking detection accuracy.
FIG. 9 shows a control block diagram corresponding to the second embodiment in which the knocking detection interval is made variable in accordance with the closing timing which is made variable by the variable valve timing mechanisms 156 and 157 described above.

In the control block diagram shown in FIG. 9, the RAM 502 stores an offset value indicating the start of the knocking occurrence section as an angle from the top dead center and a crank angle indicating the width of the knocking generation section.
Then, the knocking detection interval calculation unit 503 calculates the knocking generation interval and the closing timing + detection delay period from the information on the knocking occurrence interval and the information on the closing timing from the control target calculation unit 514 of the variable valve timing mechanisms 156 and 157. A knocking detection section including is set.

The functions of the blocks other than those described above are the same as those in FIG.
In the above description, the end of the knocking detection interval is delayed according to the delay of the closing timing IVC of the intake valve 105. However, for example, when the closing timing of the exhaust valve 107 is earlier than the beginning of the knocking occurrence interval, The start time of the detection zone can be the closing timing of the exhaust valve 107 (or the closing timing +10 deg) earlier than the start time of the knocking occurrence zone.

Further, instead of correcting the ignition timing based on the knocking detection, or together with correcting the ignition timing, the fuel injection amount (air-fuel ratio) can be corrected to suppress the occurrence of knocking.
Next, inventions other than those described in the claims that can be grasped from the above-described embodiment will be described together with the effects thereof.
(A) When the knocking occurrence section and the variable range of the closing timing by the variable valve mechanism overlap at least partially, the knocking detection section includes the closing timing. The knock detection device for an internal combustion engine according to any one of the above.

  According to the above invention, the knocking occurrence section and the variable range of the closing timing by the variable valve mechanism overlap at least partially, and the engine valve is closed within the knocking occurrence section, and the engine valve is closed outside the knocking occurrence section. When the knocking detection section includes the knocking generation section and the closing timing, the engine valve is always closed within the knocking detection section even if the closing timing is changed.

Accordingly, it is possible to prevent the occurrence of knocking from being erroneously determined when the engine valve is closed outside the knocking occurrence section to the state where the engine valve is closed within the knocking occurrence section.
(B) A moving average of the knocking intensity detected based on the output of the knocking sensor in the knocking detection section is determined, and the occurrence of knocking is determined when the difference between the moving average value and the knocking intensity is equal to or greater than a threshold value. The knock detection device for an internal combustion engine according to any one of claims 1 to 5, wherein:

According to the above invention, the knocking strength including the seating noise is constantly moving averaged, and the moving average value is compared with the knocking strength for each knocking detection section, so that knocking vibration having a strength exceeding the seating noise can be reliably detected. Can do.
(C) The variable valve mechanism is a variable valve timing mechanism that changes the valve timing of the engine valve by advancing / retarding with a constant operating angle by changing the rotational phase of the camshaft with respect to the crankshaft. The knock detection device for an internal combustion engine according to any one of claims 1 to 5, characterized in that:

According to the above invention, by changing the rotation phase of the camshaft with respect to the crankshaft, the closing timing of the engine valve changes, and even if the generation timing of the seating noise changes in and out of the knocking occurrence section, the seating noise is reduced. Based on this, it is possible to avoid erroneous determination of the occurrence of knocking.
(D) The knocking detecting device for an internal combustion engine according to claim 4, wherein the predetermined section immediately after the closing timing is set to a predetermined crank angle stored in advance.

  According to the above invention, even if there is a delay time from the closing timing of the engine valve until the seating noise is detected by the knocking sensor, the seating noise can be reliably detected within the knocking detection section with a simple configuration. .

1 is a system diagram of an internal combustion engine in an embodiment of the present invention. The time chart which shows the correlation with the knock generation | occurrence | production area in the internal combustion engine of embodiment, and the open period of an intake / exhaust valve. The time chart for demonstrating the reason for misjudging generation | occurrence | production of knocking by the change of the closing timing of an intake valve. The figure which shows 1st Embodiment of the setting of a knocking detection area. The control block diagram which shows the knocking detection process in the said 1st Embodiment. The flowchart which shows 2nd Embodiment of the setting of a knocking detection area. The figure which shows the example which expands a knocking detection area rather than a knock generation | occurrence | production area by the said 2nd Embodiment. The figure which shows the example which makes a knock generation area as it is a knock detection area by the said 2nd Embodiment. The control block diagram which shows the knocking detection process in the said 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 101 ... Internal combustion engine, 104 ... Electronically controlled throttle, 105 ... Intake valve, 107 ... Exhaust valve, 110, 111 ... Camshaft, 114 ... Control unit, 115 ... Air flow meter, 116 ... Accelerator opening sensor, 117 ... Crank angle sensor , 118 ... throttle sensor, 120 ... crankshaft, 122 ... knocking sensor, 131 ... fuel injection valve, 151 ... ignition plug, 152 ... ignition coil with built-in power transistor, 156, 157 ... variable valve timing mechanism (variable valve mechanism)

Claims (5)

In an internal combustion engine equipped with a variable valve mechanism that makes the valve timing of the engine valve variable, knocking is detected when the knocking strength is detected based on the output of the knocking sensor in the knocking detection section and the knocking strength exceeds the judgment value. An internal combustion engine knock detection device for determining
The knocking detection section includes a knocking generation section in which knocking is predicted in the combustion stroke of each cylinder, and a closing timing of the engine valve that overlaps each combustion stroke and is variable by the variable valve mechanism. A knocking detection apparatus for an internal combustion engine, comprising:   2. The knocking detection device for an internal combustion engine according to claim 1, wherein the knocking detection section is a fixed section including the entire variable range of the closing timing by the variable valve mechanism.   2. The knock detection device for an internal combustion engine according to claim 1, wherein the knocking detection section is variably set in accordance with a change in the closing timing of the engine valve by the variable valve mechanism.   The knock detection of the internal combustion engine according to any one of claims 1 to 3, wherein the knocking detection section includes the knocking occurrence section, the closing timing, and a predetermined section immediately after the closing timing. apparatus.   As the variable valve mechanism, an intake-side variable valve mechanism that varies the valve timing of the intake valve and an exhaust-side variable valve mechanism that varies the valve timing of the exhaust valve are separately provided, and the intake valve is closed. The start of the knocking detection interval is determined based on the earlier of the timing and the closing timing of the exhaust valve, and the knocking detection interval of the knocking detection interval is determined based on the later of the closing timing of the intake valve and the closing timing of the exhaust valve. The knocking detection device for an internal combustion engine according to any one of claims 1 to 4, wherein an end stage is determined.

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