JP2009257091A - Knocking determining device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the possibility of erroneously determining whether or not knocking occurs. <P>SOLUTION: An engine ECU carries out a program including a step (S300) of updating the standard deviation σ of the accumulated value lpkknk of the vibration intensity, a step (S302) of updating the median VM of the accumulated value lpkknk, a step (S304) of updating the knocking determination level VKD using the updated median VM and standard deviation σ, a step (S400) of determining whether or not the accumulated value lpkknk is same as or higher than the knocking determination level VKD, that is, whether or not knocking occurs, and a step (S206) of stopping the determination on whether or not knocking occurs if the ignition timing is retarded than the top dead center (YES in the step S200). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a knock determination device for an internal combustion engine, and more particularly to a technique for stopping determining whether knock has occurred or not when retarding an ignition timing.

  Conventionally, various methods for determining the presence or absence of knocking (knocking) have been proposed. For example, there is a technique for determining the occurrence of knocking based on whether or not the intensity of vibration detected from an internal combustion engine is greater than a knock determination value.

Japanese Patent Laid-Open No. 2007-255195 (Patent Document 1) discloses a detection unit for detecting the intensity of vibration generated in an internal combustion engine a plurality of times, and vibration caused by knocking according to each intensity detected by the detection unit. And a control unit for controlling the ignition timing of the internal combustion engine based on a result of comparing the knock intensity with a predetermined first determination value. An ignition timing control device for an internal combustion engine comprising: For example, when the knock magnitude is larger than the first determination value, the ignition timing is retarded.
JP 2007-255195 A

  By the way, the ignition timing of the internal combustion engine is retarded in order to reduce shock or vibration at the time of shifting or sudden acceleration of the automatic transmission, as well as when knocking occurs. That is, even if knocking has not occurred, the ignition timing is retarded according to the traveling state of the vehicle. If the ignition timing is retarded until after the top dead center, it may be difficult to distinguish between vibration caused by knocking generated at a crank angle after top dead center and vibration generated by ignition. This is because the crank angle at which vibration generated by ignition can be detected overlaps with the crank angle at which vibration due to knocking can be detected. Therefore, it can be erroneously determined whether or not knocking has occurred. However, Japanese Patent Laid-Open No. 2007-255195 has no disclosure regarding such a problem.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a knock determination device for an internal combustion engine that can reduce the possibility of erroneous determination of whether or not knocking has occurred. Is to provide.

  An internal combustion engine knock determination device according to a first aspect of the present invention is a means for controlling the ignition timing of an internal combustion engine in accordance with the running state of a vehicle, and for detecting the intensity of vibration of the internal combustion engine in a plurality of ignition cycles. And a first calculating means for calculating the first value representing the median value of the intensity according to the intensity, and a second value representing the standard deviation of the intensity according to the intensity. A second calculating means for calculating by updating, a setting means for setting a determination value according to the first value and the second value, and if the strength is greater than the determination value, knocking is Means for determining that it has occurred. The determination means includes a determination stop means for stopping determining whether or not knocking has occurred when the ignition timing is later than a predetermined timing.

  According to this configuration, the ignition timing of the internal combustion engine is controlled according to the traveling state of the vehicle. For example, the ignition timing is retarded in order to reduce shock or vibration at the time of shifting of an automatic transmission connected to the internal combustion engine or at the time of sudden acceleration of the vehicle. Further, the intensity of vibration of the internal combustion engine is detected in a plurality of ignition cycles. A first value representing the median value of the detected intensity and a second value representing the standard deviation are calculated. Determination values corresponding to the first value and the second value are set. Thereby, it is possible to obtain a determination value corresponding to the intensity of vibration actually generated in the internal combustion engine. When the intensity is larger than the determination value, it is determined that knocking has occurred. By the way, when the ignition timing of the internal combustion engine is retarded, the crank angle at which vibration generated by ignition can be detected and the crank angle at which vibration due to knocking can be detected may overlap. For this reason, it may be difficult to distinguish between vibration caused by knocking and vibration caused by ignition. Therefore, when the ignition timing is later than a predetermined timing, it is stopped to determine whether knocking has occurred. Accordingly, it is possible to reduce the possibility of erroneously determining that knocking has occurred when knocking has not occurred. As a result, it is possible to provide a knock determination device for an internal combustion engine that can reduce the possibility of erroneous determination of whether or not knocking has occurred.

  In the knock determination device for an internal combustion engine according to the second invention, in addition to the configuration of the first invention, the determination stop means causes knocking when the ignition timing is changed from before to after a predetermined timing. Means for stopping the determination of whether or not.

  According to this configuration, when the ignition timing is changed from before to after a predetermined timing, it is stopped to determine whether knocking has occurred. As a result, it is possible to determine whether or not knocking has occurred when vibration due to ignition can suddenly appear at a crank angle after a predetermined time, similarly to knocking that occurs suddenly. . Therefore, in a situation where it is difficult to distinguish between vibration caused by knocking and vibration caused by ignition, the possibility of erroneously determining that knocking has occurred when knocking has not occurred can be reduced.

  In the knock determination device for an internal combustion engine according to the third invention, in addition to the configuration of the first or second invention, the first calculation means is configured to output the first when the ignition timing is later than a predetermined timing. Update means for updating so that the value of changes faster. The second calculation means includes an update stop means for stopping the update of the second value when the ignition timing is later than a predetermined time.

  According to this configuration, when the ignition timing is later than the predetermined timing, the first value representing the median value is updated so as to change more quickly, and the second value representing the standard deviation is updated. Is stopped. As a result, when the magnitude of vibration generated in the internal combustion engine can change greatly due to the retarded ignition timing, the first value representing the median value is updated so as to change more quickly, and the standard deviation is changed. The update of the second value to represent can be stopped. For this reason, the first value representing the median value can quickly follow the intensity actually generated in the internal combustion engine. Further, it is possible to prevent the second value representing the standard deviation that can suddenly increase with a sudden change in detected intensity from being changed. A determination value is calculated in accordance with the first value and the second value. Therefore, the follow-up delay of the determination value with respect to the vibration actually generated in the internal combustion engine can be reduced. As a result, it is possible to obtain a determination value that accurately corresponds to vibration actually generated in the internal combustion engine.

  In the knock determination device for an internal combustion engine according to the fourth invention, in addition to the configuration of the third invention, the updating means has the first value when the ignition timing is changed from before to after a predetermined timing. Has means for updating to change faster. The update stop means has means for stopping the update of the second value when the ignition timing is changed from before to after the predetermined timing.

  According to this configuration, when the ignition timing is changed from before to after the predetermined timing, the first value representing the median is updated so as to change more quickly, and the second representing the standard deviation is used. The value update is stopped. As a result, when the magnitude of vibration generated in the internal combustion engine can change greatly due to the retarded ignition timing, the first value representing the median value is updated so as to change more quickly, and the standard deviation is changed. The update of the second value to represent can be stopped. For this reason, the first value representing the median value can quickly follow the intensity actually generated in the internal combustion engine. Further, it is possible to prevent the second value representing the standard deviation that can suddenly increase with a sudden change in detected intensity from being changed. A determination value is calculated in accordance with the first value and the second value. Therefore, the follow-up delay of the determination value with respect to the vibration actually generated in the internal combustion engine can be reduced. As a result, it is possible to obtain a determination value that accurately corresponds to vibration actually generated in the internal combustion engine.

  In the internal combustion engine knock determination device according to the fifth aspect of the present invention, in addition to the configuration of the third or fourth aspect, the determination stop means stops determining whether or not knocking has occurred a predetermined number of times. Means to do. The updating means includes means for updating the first value so as to change faster by a predetermined number of times. The update stop means has means for stopping the update of the second value a predetermined number of times.

  According to this configuration, it is stopped to determine whether knocking has occurred a predetermined number of times (for example, the number of ignitions). As a result, it is possible to limit the period for stopping determining whether knocking has been determined. Therefore, it is possible to stop determining whether or not knocking has occurred only during a period in which it is difficult to distinguish between vibration caused by knocking and vibration caused by ignition. Further, the first value representing the median value is updated so as to change more quickly by a predetermined number of times, and the updating of the second value representing the standard deviation is stopped. This makes it possible to speed up the update of the first value and limit the period during which the update of the second value is stopped. Therefore, the update of the first value can be accelerated and the update of the second value can be stopped only during a period necessary for obtaining a determination value that accurately corresponds to the vibration generated in the internal combustion engine.

  In the knock determination device for an internal combustion engine according to the sixth invention, in addition to the configuration of any one of the first to fifth inventions, the setting means calculates the product of the first coefficient greater than zero and the second value. Means for setting a value added to the value of 1 as a determination value is included.

  According to this configuration, a value obtained by adding the product of the first coefficient greater than zero and the second value to the first value is set as the determination value. Thereby, a determination value corresponding to the first value representing the median value and the second value representing the standard deviation can be obtained.

  In the internal combustion engine knock determination device according to the seventh aspect of the invention, in addition to the structure of any one of the first to sixth aspects, the predetermined time is top dead center.

  According to this configuration, when the ignition timing is after the top dead center, the determination of whether or not knocking has occurred is stopped. Thereby, when it is difficult to distinguish between vibration caused by knocking generated at a crank angle after top dead center and vibration generated by ignition, it is possible to stop determining whether knocking has occurred or not. it can. Therefore, the possibility of erroneously determining that knocking has occurred when knocking has not occurred can be reduced.

  In the knock determination device for an internal combustion engine according to the eighth aspect of the invention, in addition to the configuration of any one of the first to seventh aspects, the internal combustion engine is provided with a plurality of cylinders. The determining means includes means for determining whether knocking has occurred for each cylinder. The determination stop means stops all the cylinders from determining whether knocking has occurred when the ignition timing in at least one of the plurality of cylinders is later than a predetermined timing. Means for doing so.

  According to this configuration, it is stopped to determine whether knocking has occurred in all the cylinders provided in the internal combustion engine. Accordingly, it is possible to reduce the possibility of erroneously determining that knocking has occurred when knocking has not occurred in all the cylinders.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  With reference to FIG. 1, a vehicle engine 100 equipped with a knock determination device according to an embodiment of the present invention will be described. The engine 100 is provided with a plurality of cylinders. The knocking determination device according to the present embodiment is realized by a program executed by an engine ECU (Electronic Control Unit) 200, for example. The program executed by engine ECU 200 may be recorded on a recording medium such as a CD (Compact Disc) or a DVD (Digital Versatile Disc) and distributed to the market.

  Engine 100 is an internal combustion engine that burns an air-fuel mixture of air sucked from air cleaner 102 and fuel injected from injector 104 by igniting with an ignition plug 106 in a combustion chamber.

  The ignition timing is set according to the operating state of engine 100. Hereinafter, the ignition timing set according to the operating state of engine 100 is also referred to as basic ignition timing. When knocking occurs, the ignition timing is retarded from the basic ignition timing.

  When the air-fuel mixture burns, the piston 108 is pushed down by the combustion pressure, and the crankshaft 110 rotates. The combusted air-fuel mixture (exhaust gas) is purified by the three-way catalyst 112 and then discharged outside the vehicle. The amount of air taken into engine 100 is adjusted by throttle valve 114. When the intake valve 116 is opened, the air-fuel mixture is introduced into the combustion chamber. When the exhaust valve 118 is opened, the exhaust gas is discharged from the combustion chamber.

  Engine 100 is controlled by engine ECU 200. The engine ECU 200 includes a knock sensor 300, a water temperature sensor 302, a crank position sensor 306 provided facing the timing rotor 304, a throttle opening sensor 308, a vehicle speed sensor 310, an ignition switch 312, and an air flow meter. 314 is connected.

  Knock sensor 300 is provided in a cylinder block of engine 100. Knock sensor 300 is composed of a piezoelectric element. Knock sensor 300 generates a voltage due to vibration of engine 100. The magnitude of the voltage corresponds to the magnitude of the vibration. Knock sensor 300 transmits a signal representing a voltage to engine ECU 200. Water temperature sensor 302 detects the temperature of the cooling water in the water jacket of engine 100 and transmits a signal representing the detection result to engine ECU 200.

  The timing rotor 304 is provided on the crankshaft 110 and rotates together with the crankshaft 110. A plurality of protrusions are provided on the outer periphery of the timing rotor 304 at predetermined intervals. The crank position sensor 306 is provided to face the protrusion of the timing rotor 304. When the timing rotor 304 rotates, the air gap between the protrusion of the timing rotor 304 and the crank position sensor 306 changes, so that the magnetic flux passing through the coil portion of the crank position sensor 306 increases and decreases, and an electromotive force is generated in the coil portion. . Crank position sensor 306 transmits a signal representing the electromotive force to engine ECU 200. Engine ECU 200 detects the crank angle and the rotational speed of crankshaft 110 based on the signal transmitted from crank position sensor 306.

  Throttle opening sensor 308 detects the throttle opening and transmits a signal representing the detection result to engine ECU 200. Vehicle speed sensor 310 detects the number of rotations of a wheel (not shown) and transmits a signal representing the detection result to engine ECU 200. Engine ECU 200 calculates the vehicle speed from the rotational speed of the wheel. Ignition switch 312 is turned on by the driver when engine 100 is started. Air flow meter 314 detects the amount of air taken into engine 100 and transmits a signal representing the detection result to engine ECU 200.

  Engine ECU 200 is operated by electric power supplied from auxiliary battery 320 as a power source. The engine ECU 200 performs arithmetic processing based on signals transmitted from the sensors and the ignition switch 312, a map and a program stored in a ROM (Read Only Memory) 202, so that the engine 100 enters a desired operating state. Control equipment.

  In the present embodiment, engine ECU 200 determines a predetermined knock detection gate (a predetermined second crank angle from a predetermined first crank angle based on a signal and a crank angle transmitted from knock sensor 300). The vibration waveform of the engine 100 (hereinafter referred to as a vibration waveform) is detected in the period up to this point), and whether or not knocking has occurred in the engine 100 is determined based on the detected vibration waveform. The knock detection gate in the present embodiment is from top dead center (0 degree) to 90 degrees in the combustion stroke. The knock detection gate is not limited to this.

  When knocking occurs, as shown in FIG. 2, vibration of a frequency included in frequency bands A to C is generated in engine 100. Therefore, in the present embodiment, vibrations in a wide frequency band D including the frequency bands A to C are detected.

  As shown in FIG. 3, engine ECU 200 includes an A / D (analog / digital) conversion unit 400, a band pass filter 410, and an integration unit 420.

  The A / D converter 400 converts an analog signal into a digital signal. Bandpass filter 410 passes only the signal of frequency band D among the signals transmitted from knock sensor 300. That is, only the vibration in the frequency band D is extracted from the vibration detected by the knock sensor 300 by the bandpass filter 410.

  The integrating unit 420 integrates a signal selected by the bandpass filter 410, that is, an integrated value obtained by integrating the vibration intensity by 5 ° CA (Crank Angle) as a crank angle (hereinafter also referred to as a 5 ° CA integrated value). calculate. Thereby, as shown in FIG. 4, the vibration waveform of the frequency band D is detected.

  The detected vibration waveform is used to calculate a correlation coefficient K that represents the degree to which the vibration waveform is similar to the knock waveform model (represents the difference between the shape of the vibration waveform and the shape of the knock waveform model). As shown in FIG. 5, it is detected in the range of the crank angle after the crank angle at which the strength is the largest, that is, the crank angle at which the strength is peak, which is larger than the strength of the adjacent crank angle. The correlation coefficient K is calculated by comparing the generated vibration waveform with the knock waveform model.

  Hereinafter, a method for specifying the crank angle at which the intensity reaches a peak in the vibration waveform will be described.

  In this embodiment, as shown in FIG. 6, the strength (three 5 ° CA integrated values) is integrated for each region obtained by dividing the knock detection gate into 6 equal parts, that is, 15 ° CA in crank angle. ° CA integrated value is calculated. The 15 ° CA integrated value is calculated for each of a plurality of ignition cycles. Note that the number of regions is not limited to six, and any other number may be used.

  Due to the difference between the 15 ° CA integrated value of the current ignition cycle and the 15 ° CA integrated value of the previous (one previous) ignition cycle, the change amount ΔV (1) to 15 ° CA integrated value indicated by hatching in FIG. ΔV (6) is detected.

  Of the six regions in which the change amounts ΔV (1) to ΔV (6) of the 15 ° CA integrated value are detected, two regions where the change amount of the 15 ° CA integrated value is larger are identified. That is, the top two areas with the largest amount of change are specified. Note that the number of areas to be specified is not limited to two.

  The same area as the identified area is defined as a search area, and within this search area, the maximum intensity (within the intensity (5 ° CA integrated value)) is larger than the adjacent crank angle intensity (5 ° CA integrated value). A crank angle of 5 ° CA integrated value) is specified. That is, the crank angle at which the intensity peaks in the vibration waveform is specified. A comparison between the vibration waveform and the knock waveform model is performed by making the crank angle coincide with the timing at which the vibration intensity in the knock waveform model becomes maximum.

  The knock waveform model is determined as a reference for the vibration waveform of engine 100 when knocking occurs. In the present embodiment, the strength of the knock waveform model is set every time it is compared with the vibration waveform. More specifically, the maximum intensity value in the knock waveform model is set to be the same as the intensity (peak value of intensity) greater than the adjacent intensity in the vibration waveform.

  On the other hand, the intensity other than the maximum value is set according to the engine speed NE and the load of the engine 100. More specifically, the attenuation rate of the intensity at the adjacent crank angle is set according to a map having the engine speed NE and the load of engine 100 as parameters.

  For example, when an intensity of 20 degrees is set as the crank angle with an attenuation rate of 25%, the intensity decreases by 25% as shown in FIG. The method for setting the strength of the knock waveform model is not limited to this.

  The correlation coefficient K is calculated by calculating the absolute value (deviation amount) of the difference between the intensity in the vibration waveform and the intensity in the knock waveform model for each crank angle (every 5 ° CA). The absolute value of the difference between the intensity in the vibration waveform and the intensity in the knock waveform model may be calculated for each crank angle other than 5 ° CA.

  The absolute value of the difference for each crank angle between the intensity in the vibration waveform and the intensity in the knock waveform model is set to ΔS (I) (I is a natural number). As indicated by hatching in FIG. 8, a value obtained by summing the vibration intensities of the knock waveform model, that is, the area of the knock waveform model is S. The correlation coefficient K is calculated using Equation 1 below.

K = (S−ΣΔS (I)) / S (1)
ΣΔS (I) is the sum of ΔS (I). Note that the method of calculating the correlation coefficient K is not limited to this.

  In the present embodiment, in addition to correlation coefficient K, knock magnitude N is calculated. Knock strength N is calculated using an integrated value lpkknk obtained by summing up the strength (5 ° CA integrated value) in the vibration waveform, as indicated by hatching in FIG. Note that the maximum intensity in the vibration waveform may be used instead of the integrated value lpkknk.

  A value representing the intensity of vibration of engine 100 in a state where knocking has not occurred in engine 100 is represented as BGL (Back Ground Level). Knock strength N is calculated using Equation 2 below.

N = lpkknk / BGL (2)
The method for calculating knock magnitude N is not limited to this. When calculating knock magnitude N, a logarithmic conversion value of integrated value lpkknk is used. BGL is a value obtained by subtracting, from median value VM, the product of standard deviation σ and a positive coefficient (for example, “1”) in a frequency distribution representing the frequency (number of times or probability) at which each integrated value lpkknk is detected. Is calculated as Note that the BGL calculation method is not limited to this, and the BGL may be stored in the ROM 202. Further, when creating the frequency distribution, the logarithm conversion value of the integrated value lpkknk is used. Therefore, as shown in FIG. 10, in the frequency distribution of integrated value lpkknk, knock magnitude N is expressed as the difference between integrated value lpkknk and BGL. The frequency distribution is created for each cylinder.

  By the way, as shown in FIG. 11, when the change amount of the integrated value of 15 degrees is large in the end point of the knock detection gate, that is, in the region around 90 degrees in the crank angle, the crank angle at which the intensity level reaches the peak Among the bisected regions, the region can be identified from the retarded region.

  In engine 100, it is known that knocking occurs near top dead center. That is, it can be said that the vibration that occurs near 90 degrees in crank angle is caused by factors other than knocking.

  Therefore, if there is a region specified as a region where the amount of change in the 15 ° CA integrated value is larger outside the peak search section defined in front of the knock detection gate, the 15 ° integrated value changes without causing knocking. It is highly possible. In this case, the vibration waveform is corrected so that the 15 ° CA integrated value in the specified region becomes the same value as the 15 ° CA integrated value calculated in the previous ignition cycle. That is, the hatched portion in FIG. 11 is removed. As a result, a vibration waveform as shown in FIG. 12 is obtained. When the vibration waveform is corrected, the integrated value lpkknk in the corrected vibration waveform is used.

  In the present embodiment, whether or not knocking has occurred is determined for each ignition using the correlation coefficient K calculated based on the shape of the vibration waveform and the knock intensity N calculated based on the strength of the vibration waveform. Is determined. Whether or not knocking has occurred is determined for each cylinder. If correlation coefficient K is equal to or greater than threshold value K1 and knock magnitude N is equal to or greater than determination value VJ, it is determined that knocking has occurred. Otherwise, it is determined that knocking has not occurred.

  Further, in the present embodiment, as shown in FIG. 13, knocking occurs when the region specified as the region where the change amount of the 15 ° CA integrated value is larger is outside the predetermined peak search interval. It is determined that it is not.

  If it is determined that knocking has occurred, the ignition timing is retarded by a predetermined amount. If it is determined that knocking has not occurred, the ignition timing is advanced by a predetermined amount.

  By the way, when the engine 100 or the vehicle is shipped, a value determined in advance through experiments or the like is used as the determination value VJ stored in the ROM 202 (initial value of the determination value VJ at the time of shipment). However, the detected intensity can change even when the same vibration occurs in engine 100 due to variations or deterioration in the output value of knock sensor 300. In this case, it is necessary to correct the determination value VJ and determine whether knocking has occurred using the determination value VJ according to the actually detected intensity. Therefore, in the present embodiment, determination value VJ is corrected every ignition cycle of a predetermined number of times IGN1 (for example, 200 times).

  Determination value VJ is corrected according to a knock count value KC described later. In order to count knock count value KC, it is determined whether knocking has occurred using a method different from the method described above.

  The function of engine ECU 200 will be described with reference to FIG. Note that the functions described below may be realized by software or hardware.

  The engine ECU 200 includes an ignition timing setting unit 500, a crank angle detection unit 600, an intensity detection unit 602, a waveform detection unit 604, a correlation coefficient calculation unit 606, an integrated value calculation unit 608, and a knock intensity calculation unit 610. A first knock determination unit 612, an ignition timing control unit 614, an ignition timing determination unit 616, and a feedback unit 700.

  Ignition timing setting unit 500 sets the basic ignition timing according to the running state (driving state) of the vehicle and the driving state of engine 100. The basic ignition timing is set, for example, according to a map having the engine speed NE and the load KL as parameters. Further, at the time of shifting of an automatic transmission (not shown) connected to engine 100, when the vehicle is accelerated, the crank angle after the top dead center is set as the basic ignition timing.

  The crank angle detection unit 600 detects the crank angle based on the signal transmitted from the crank position sensor 306.

  Based on the signal transmitted from knock sensor 300, intensity detector 602 detects the intensity of vibration at the knock detection gate. The intensity of vibration is detected corresponding to the crank angle. The intensity of vibration is expressed by the output voltage value of knock sensor 300. The intensity of vibration may be represented by a value corresponding to the output voltage value of knock sensor 300.

  The waveform detection unit 604 detects the vibration waveform at the knock detection gate by integrating the vibration intensity by 5 ° CA in terms of the crank angle.

  The correlation coefficient calculation unit 606 calculates a correlation coefficient K that represents the degree to which the vibration waveform is similar to the knock waveform model (represents the difference between the shape of the vibration waveform and the shape of the knock waveform model).

  The integrated value calculation unit 608 calculates an integrated value lpkknk obtained by adding the intensity (5 ° CA integrated value) in the vibration waveform by the knock detection gate. Knock strength calculation unit 610 calculates knock strength N using integrated value lpkknk.

  The first knock determination unit 612 determines whether or not knocking has occurred for each ignition using the correlation coefficient K and the knock intensity N. If correlation coefficient K is equal to or greater than threshold value K1 and knock magnitude N is equal to or greater than determination value VJ, it is determined that knocking has occurred. Otherwise, it is determined that knocking has not occurred. Moreover, when the area | region specified as an area | region where the variation | change_quantity of 15 degree CA integrated value is larger is outside a peak search area, it determines with knocking not having generate | occur | produced. Furthermore, the first knock determination unit 612 stops determining whether knocking has occurred when the ignition timing is after top dead center.

  The ignition timing control unit 614 performs control by correcting the ignition timing according to whether knocking has occurred. If it is determined that knocking has occurred, the ignition timing is retarded by a predetermined amount. If it is determined that knocking has not occurred, the ignition timing is advanced by a predetermined amount.

  The ignition timing determination unit 616 determines whether or not the ignition timing is after top dead center. More specifically, it is determined whether or not the ignition timing has been changed from before the top dead center. That is, it is determined whether or not the ignition timing in the current ignition cycle is after top dead center and the ignition timing in the previous ignition cycle is before top dead center.

  Feedback unit 700 sets determination value VJ to be compared with knock magnitude N. As shown in FIG. 14, the feedback unit 700 includes a frequency distribution creation unit 702, a median value calculation unit 704, a standard deviation calculation unit 706, a BGL calculation unit 708, a knock determination level calculation unit 710, and a second knocking. A determination unit 712, a count unit 714, and a correction unit 716 are included.

  As shown in FIG. 15, the frequency distribution creating unit 702 creates a frequency distribution of the integrated value lpkknk calculated in each ignition cycle. When creating the frequency distribution, the logarithm conversion value of the integrated value lpkknk is used.

  Median value calculation unit 704 calculates median value VM of integrated values lpkknk. Median value VM is calculated for each ignition cycle using Equation 3 below.

VM (i) = VM (i−1) + (lpkknk−VM (i−1)) / X (3)
In Equation 3, VM (i) indicates the current value. VM (i-1) indicates the previous value. X is a positive value. That is, median value VM is calculated by updating by an update amount (lpkknk−VM (i−1)) / X determined according to integrated value lpkknk. As X decreases, the update amount of median value VM increases.

  Median value VM calculated using Equation 3 is an approximate value representing the median value calculated based on a plurality (for example, 200 ignition cycles) of integrated values lpkknk. Therefore, the median value VM calculated using Equation 3 may be different from the actual median value.

  Furthermore, when the ignition timing determination unit 616 determines that the ignition timing is later than the top dead center, the median value calculation unit 704 is more specifically assumed that the ignition timing has been changed from before the top dead center. If determined, the update amount of the median value VM is increased during a predetermined number of ignition cycles IGN2 (for example, IGN2 <IGN1). That is, updating is performed so that the median value VM changes more quickly.

  In at least one of the plurality of cylinders, when it is determined that the ignition timing is later than the top dead center, more specifically, it is determined that the ignition timing has been changed from before the top dead center. In this case, the update amount of the median value VM is increased in all the cylinders. Note that the number and frequency of updates may be increased instead of or in addition to increasing the update amount.

  Standard deviation calculation unit 706 calculates standard deviation σ of integrated value lpkknk. The standard deviation σ is calculated for each ignition cycle using Equation 4 below.

σ (i) = σ (i−1) + (lpkknk−σ (i−1)) / Y (4)
In Equation 4, σ (i) represents the current value. σ (i−1) indicates the previous value. Y is a positive value. That is, the standard deviation σ is calculated by updating the update amount (lpkknk−σ (i−1)) / Y determined according to the integrated value lpkknk.

Note that the standard deviation σ calculated using Expression 4 is an approximate value representing a standard deviation calculated based on a plurality (for example, 200 ignition cycles) of integrated values lpkknk. Therefore,
The standard deviation σ calculated using Equation 4 may be different from the actual standard deviation.

  Furthermore, when the ignition timing determination unit 616 determines that the ignition timing is later than the top dead center, the standard deviation calculation unit 706 is more specifically assumed that the ignition timing has been changed from before the top dead center. If determined, updating of the standard deviation σ is stopped during a predetermined number of ignition cycles IGN2.

  In at least one of the plurality of cylinders, when it is determined that the ignition timing is later than the top dead center, more specifically, it is determined that the ignition timing has been changed from before the top dead center. If so, the update of the standard deviation σ is stopped in all the cylinders.

  Instead of calculating median value VM and standard deviation σ using equations 3 and 4, the following calculation method may be used.

  When the integrated value lpkknk calculated this time is larger than the median value VM calculated last time, a value obtained by adding a predetermined value C1 to the median value VM calculated last time is calculated as the current median value VM. Conversely, if the integrated value lpkknk calculated this time is smaller than the median value VM calculated last time, a value obtained by subtracting a predetermined value C2 (for example, C2 is the same value as C1) from the median value VM calculated last time. Is calculated as the median value VM of this time.

  When the integrated value lpkknk calculated this time is smaller than the median value VM calculated last time and larger than the value obtained by subtracting the standard deviation σ calculated last time from the median value VM calculated last time, the previously calculated standard value A value obtained by subtracting a value obtained by doubling a predetermined value C3 from the deviation σ is calculated as the current standard deviation σ. Conversely, if the integrated value lpkknk calculated this time is larger than the median value VM calculated last time, or smaller than the value obtained by subtracting the standard deviation σ calculated last time from the median value VM calculated last time, A value obtained by adding a predetermined value C4 (for example, C4 is the same value as C3) to the calculated standard deviation σ is calculated as the current standard deviation σ. The initial value of median value VM and standard deviation σ may be a preset value or “0”.

  As shown in FIG. 15, the BGL calculation unit 708 calculates BGL by subtracting the standard deviation σ from the median value VM.

  Knock determination level calculation unit 710 calculates (sets) knock determination level VKD using median value VM and standard deviation σ. As shown in FIG. 15, a value obtained by adding the product of positive coefficient U (U is a constant, for example, U = 3) and standard deviation σ to median value VM is knock determination level VKD. The method for calculating knock determination level VKD is not limited to this.

  The coefficient U is a coefficient obtained from data or knowledge obtained through experiments or the like. The integrated value lpkknk that is larger than the knock determination level VKD when U = 3 substantially matches the integrated value lpkknk in the ignition cycle in which knocking actually occurs. A value other than “3” may be used as the coefficient U.

  Second knock determination unit 712 determines that knocking has occurred when integrated value lpkknk is equal to or higher than knock determination level VKD. When the ignition timing determination unit 616 determines that the ignition timing is later than the top dead center, more specifically, the second knock determination unit 712 changes the ignition timing from before the top dead center. If it is determined that the knocking has occurred, the determination of whether knocking has occurred is stopped.

  In at least one of the plurality of cylinders, when it is determined that the ignition timing is later than the top dead center, more specifically, it is determined that the ignition timing has been changed from before the top dead center. If so, it is stopped to determine whether knocking has occurred in all the cylinders.

  Counting unit 714 counts the frequency of integrated value lpkknk that is equal to or higher than knock determination level VKD during the predetermined number of ignition cycles IGN1 as knock count value KC. That is, in the ignition cycle of the predetermined number of times IGN1, the frequency of occurrence of knocking is counted as the knock count value KC.

  Further, when the ignition timing determination unit 616 determines that the ignition timing is later than the top dead center, the count unit 714 determines more specifically that the ignition timing has been changed from before the top dead center. If it is detected, counting of knock count value KC is stopped.

  In at least one of the plurality of cylinders, when it is determined that the ignition timing is later than the top dead center, more specifically, it is determined that the ignition timing has been changed from before the top dead center. In this case, the counting of knock count value KC is stopped in all cylinders.

  When the knock count value KC is equal to or greater than the threshold value KC1, the correction unit 716 corrects the determination value VJ so as to decrease by a predetermined correction amount A1. Further, when the knock count value KC is smaller than the threshold value KC1, the correction unit 716 corrects the determination value VJ so as to increase by a predetermined correction amount A2.

  Referring to FIG. 16, a control structure of a program executed by engine ECU 200 to determine whether knocking has occurred every ignition cycle will be described.

  In step (hereinafter step is abbreviated as S) 100, engine ECU 200 detects the crank angle based on the signal transmitted from crank position sensor 306. In S102, engine ECU 200 detects the intensity of vibration of engine 100 in accordance with the crank angle based on the signal transmitted from knock sensor 300.

  In S104, engine ECU 200 calculates a 5 ° CA integrated value obtained by integrating the output voltage value of knock sensor 300 (a value representing the intensity of vibration) every 5 ° CA (by 5 ° CA) in crank angle. Thus, the vibration waveform of engine 100 is detected.

  In S106, engine ECU 200 calculates correlation coefficient K. In S108, engine ECU 200 calculates integrated value lpkknk. In S110, engine ECU 200 calculates knock magnitude N.

  In S120, engine ECU 200 determines whether knocking has occurred or not. If correlation coefficient K is equal to or greater than threshold value K1 and knock magnitude N is equal to or greater than determination value VJ, it is determined that knocking has occurred. In addition, when the region specified as the region where the change amount of the 15 ° CA integrated value is larger is outside the predetermined peak search section, it is determined that knocking has not occurred. If it is determined that knocking has occurred (YES in S120), the process proceeds to S122. If not (NO in S120), the process proceeds to S124.

  In S122, engine ECU 200 retards the ignition timing. Thereafter, the process returns to S100. In S124, engine ECU 200 advances the ignition timing. Thereafter, the process returns to S100.

  A control structure of a program executed by engine ECU 200 to correct determination value VJ will be described with reference to FIG.

  In S200, engine ECU 200 determines whether or not the ignition timing is after top dead center. If the ignition timing is after top dead center (YES in S200), the process proceeds to S202. If not (NO in S200), the process proceeds to S300.

  In S202, engine ECU 200 determines whether or not the ignition timing in the previous ignition cycle is before top dead center. If the ignition timing in the previous ignition cycle is before top dead center (YES in S202), the process proceeds to S204. If not (NO in S202), the process proceeds to S300.

  In S204, engine ECU 200 moves in the retard direction by a predetermined crank angle in the peak search section.

  In S206, engine ECU 200 stops determining whether integrated value lpkknk is equal to or higher than knock determination level VKD, that is, whether knocking has occurred. In S208, engine ECU 200 stops counting knock count value KC.

  In S210, engine ECU 200 stops updating standard deviation σ. In S212, engine ECU 200 increases the update amount of median value VM and updates median value VM. In S214, engine ECU 200 updates (sets) knock determination levels VKD and BGL. In S216, engine ECU 200 stops counting the number of ignition cycles after correcting determination value VJ.

  In S218, engine ECU 200 determines whether or not a predetermined number of ignition cycles equal to or greater than IGN2 has elapsed. If an ignition cycle equal to or greater than the predetermined number of times IGN2 has elapsed (YES in S218), the process returns to S200. If not (NO in S218), the process proceeds to S206.

  In S300, engine ECU 200 updates standard deviation σ. In S302, engine ECU 200 updates median value VM using a normal update amount. That is, the median value VM is updated using an update amount smaller than the update amount while stopping determining whether knocking has occurred. In S304, engine ECU 200 updates knock determination levels VKD and BGL.

  In S400, engine ECU 200 determines whether integrated value lpkknk is equal to or higher than knock determination level VKD, that is, whether knocking has occurred. In S402, engine ECU 200 counts knock count value KC.

  In S404, engine ECU 200 determines whether or not the number of ignition cycles after correcting previous determination value VJ is equal to or greater than a predetermined number of times IGN1. If the number of ignition cycles after correcting previous determination value VJ is equal to or greater than a predetermined number of times IGN1 (YES in S404), the process proceeds to S406. If not (NO in S404), the process returns to S200.

  In S406, engine ECU 200 corrects determination value VJ according to knock count value KC. When knock count value KC is equal to or greater than threshold value KC1, determination value VJ is corrected so as to decrease by a predetermined correction amount A1. When knock count value KC is smaller than threshold value KC1, determination value VJ is corrected so as to increase by a predetermined correction amount A2.

  An operation of engine ECU 200 in the present embodiment based on the above-described structure and flowchart will be described.

  During operation of engine 100, the crank angle is detected based on the signal transmitted from crank position sensor 306 (S100). Based on the signal transmitted from knock sensor 300, the intensity of vibration of engine 100 is detected in correspondence with the crank angle (S102). A vibration waveform of engine 100 is detected by calculating a 5 ° CA integrated value obtained by integrating the output voltage value of knock sensor 300 every 5 ° CA with a crank angle (S104).

  In order to determine whether knocking has occurred or not based on the shape of the waveform, a correlation coefficient K is calculated using a knock waveform model (S106). Further, an integrated value lpkknk is calculated in order to determine whether the vibration generated due to knocking is included in the vibration waveform based on the strength (S108). Knock strength N is calculated by dividing integrated value lpkknk by BGL (S110).

  If it is determined that knocking has occurred in engine 100 (YES in S120), the ignition timing is retarded to suppress knocking (S122). On the other hand, when it is determined that knocking has not occurred in engine 100 (NO in S120), the ignition timing is advanced (S124).

  By the way, the ignition timing can be retarded other than when knocking occurs. For example, the crank angle after the top dead center is set as the basic ignition timing at the time of shifting of the automatic transmission and acceleration of the vehicle.

  If the ignition timing is after top dead center (YES in S200), it is determined whether or not the ignition timing in the previous ignition cycle is before top dead center (S202). If the ignition timing in the previous ignition cycle is before top dead center (YES in S202), the peak search interval is retarded by a predetermined crank angle (S204).

  Further, it is stopped to determine whether or not the integrated value lpkknk is equal to or higher than the knock determination level VKD, that is, whether or not knocking has occurred (S206). As a result, when the crank angle after the top dead center can suddenly (transiently) generate vibrations due to ignition, it is difficult to distinguish between vibrations caused by knocking and vibrations generated by ignition. The determination of whether knocking has occurred can be stopped. Therefore, the possibility of erroneously determining that knocking has occurred when knocking has not occurred can be reduced.

  Further, counting of knock count value KC and updating of standard deviation σ are stopped (S208, S210). The median value VM is updated with a large update amount (S212). Thereafter, knock determination levels VKD and BGL are updated according to median value VM and standard deviation σ (S214).

  As a result, when the magnitude of vibration generated in engine 100 can change greatly due to the retarded ignition timing, median value VM is updated so as to change more quickly, and updating of standard deviation σ is stopped. be able to. Therefore, median value VM can quickly follow the intensity actually generated in engine 100. Further, it is possible to prevent the standard deviation σ that can suddenly increase with a sudden change in detected intensity from being changed. Knock determination levels VKD and BGL are set according to median value VM and standard deviation σ. Therefore, the follow-up delay of knock determination level VKD and BGL with respect to vibration actually generated in engine 100 can be reduced.

  Since counting of knock count value KC is stopped, counting of the number of ignition cycles after correcting determination value VJ is also stopped (S216).

  In these processes, the ignition timing is after the top dead center (YES in S200), and ignition is performed after it is determined that the ignition timing in the previous ignition cycle is before the top dead center (YES in S202). The cycle is performed while the number of cycles is smaller than the predetermined number of times IGN2 (NO in S218).

  On the other hand, if the ignition timing is before top dead center (NO in S200), or if the ignition timing in the previous ignition cycle is after top dead center (NO in S202), standard deviation σ is updated. (S300). Further, the median value VM is updated using the normal update amount (S302). Using the updated median value VM and standard deviation σ, knock determination levels VKD and BGL are updated (S304).

  Thereafter, it is determined whether or not integrated value lpkknk is equal to or higher than knock determination level VKD, that is, whether or not knocking has occurred (S400). In order to correct determination value VJ, knock count value KC is counted using knock determination level VKD (S402). If the number of ignition cycles since the determination value VJ was corrected last time is equal to or greater than the predetermined number IGN1 (YES in S404), determination value VJ is corrected in accordance with knock count value KC (S406). ).

  When knock count value KC is equal to or greater than threshold value KC1, determination value VJ is corrected so as to decrease by correction amount A1. Thereby, it can be easily determined that knocking has occurred. Therefore, the frequency of retarding the ignition timing can be increased. As a result, the number of times that knocking occurs can be reduced.

  When knock count value KC is smaller than threshold value KC1, determination value VJ is corrected so as to increase by correction amount A2. Thereby, it can be made difficult to determine that knocking has occurred. For this reason, the frequency at which the ignition timing is advanced can be increased. As a result, the output of engine 100 can be increased.

  As described above, according to the knock determination device according to the present embodiment, if the ignition timing is after top dead center, whether or not integrated value lpkknk is equal to or higher than knock determination level VKD, that is, knocking occurs. Determining whether or not has been done is stopped. As a result, it is possible to determine whether or not knocking has occurred when it is difficult to distinguish between the vibration caused by the knocking and the vibration caused by the ignition because the vibration caused by the ignition can appear at the crank angle after the top dead center. The determination can be stopped. Therefore, the possibility of erroneously determining that knocking has occurred when knocking has not occurred can be reduced.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a schematic block diagram which shows an engine. It is a figure which shows the frequency band of the vibration which generate | occur | produces with an engine at the time of knocking. It is a control block diagram which shows engine ECU. It is a figure which shows the vibration waveform of an engine. It is the figure which compared the vibration waveform and the knock waveform model. It is a figure which shows the value which integrated | accumulated the intensity | strength of the vibration waveform for every 15 degree CA. It is a figure which shows a knock waveform model. It is a figure which shows the area S of a knock waveform model. It is a figure which shows integrated value lpkknk. It is a figure which shows knock intensity | strength N. FIG. It is a figure (the 1) which shows the vibration waveform containing noise. It is a figure which shows the vibration waveform after correction | amendment. It is a figure (the 2) which shows the vibration waveform containing noise. It is a functional block diagram of engine ECU. It is a figure which shows frequency distribution of integrated value lpkknk. It is FIG. (1) which shows the control structure of the program which engine ECU performs. It is FIG. (2) which shows the control structure of the program which engine ECU performs.

Explanation of symbols

  100 engine, 104 injector, 106 spark plug, 110 crankshaft, 116 intake valve, 118 exhaust valve, 200 engine ECU, 202 ROM, 300 knock sensor, 302 water temperature sensor, 304 timing rotor, 306 crank position sensor, 308 throttle opening Sensor, 310 Vehicle speed sensor, 312 Ignition switch, 314 Air flow meter, 320 Auxiliary battery, 400 A / D converter, 410 Bandpass filter, 420 Accumulator, 500 Ignition timing setting unit, 600 Crank angle detector, 602 Strength detection , 604 waveform detection unit, 606 correlation coefficient calculation unit, 608 integrated value calculation unit, 610 knock intensity calculation unit, 612 first knock determination unit, 614 ignition timing control unit, 616 Ignition timing determination unit, 700 feedback unit, 702 frequency distribution creation unit, 704 median value calculation unit, 706 standard deviation calculation unit, 708 BGL calculation unit, 710 knock determination level calculation unit, 712 second knock determination unit, 714 count unit, 716 Correction unit.

Claims (8)

A knock determination device for an internal combustion engine mounted on a vehicle,
Means for controlling the ignition timing of the internal combustion engine in accordance with the running state of the vehicle;
Means for detecting the intensity of vibration of the internal combustion engine in a plurality of ignition cycles;
First calculating means for calculating a first value representing the median value of the intensity by updating according to the intensity;
Second calculation means for calculating a second value representing a standard deviation of the intensity by updating the intensity according to the intensity;
Setting means for setting a determination value according to the first value and the second value;
Means for determining that knocking has occurred if the intensity is greater than the determination value;
The determination means includes a determination stop means for stopping determination of whether or not knocking has occurred when the ignition timing is later than a predetermined timing.   The said determination stop means has a means for stopping determining whether knocking generate | occur | produced when the ignition timing is changed before and after the predetermined time. A knocking determination device for an internal combustion engine. The first calculating means includes an updating means for updating the first value so as to change faster when the ignition timing is later than the predetermined timing,
The internal combustion engine according to claim 1 or 2, wherein the second calculation means includes an update stop means for stopping the update of the second value when the ignition timing is later than a predetermined timing. Engine knocking determination device. The update means includes means for updating the first value so that the first value changes faster when the ignition timing is changed from before to after a predetermined time,
4. The knocking of the internal combustion engine according to claim 3, wherein the update stopping means includes means for stopping the update of the second value when the ignition timing is changed from before to after a predetermined timing. Judgment device. The determination stop means includes means for stopping determining whether knocking has occurred a predetermined number of times;
The updating means comprises means for updating the first value to change faster by the predetermined number of times;
5. The knock determination device for an internal combustion engine according to claim 3, wherein the update stop means includes means for stopping the update of the second value by the predetermined number of times.   The setting means includes means for setting a value obtained by adding a product of a first coefficient greater than zero and the second value to the first value as the determination value. The knock determination device for an internal combustion engine according to any one of the above.   The knock determination device for an internal combustion engine according to claim 1, wherein the predetermined time is top dead center. The internal combustion engine is provided with a plurality of cylinders,
The determination means includes means for determining whether knocking has occurred for each cylinder,
The determination stop means determines whether or not knocking has occurred when an ignition timing in at least one of the plurality of cylinders is later than the predetermined timing. The knock determination device for an internal combustion engine according to any one of claims 1 to 7, further comprising means for stopping the cylinder.

Images