JP2005083314A - Knocking detection device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a knocking detection device for an internal combustion engine capable of determining knocking suitable for human auditory sense without adding any new sensor, to a current knocking control system. <P>SOLUTION: A knocking sensor is attached to the internal combustion engine. A prescribed gate interval is set according to an operation state of the internal combustion engine, and a sound pressure effective value of a signal from the knocking sensor in the gate interval is calculated. When the sound pressure effective value exceeds a basic value, the knocking detection device for the internal combustion engine determines generation of the knocking in the internal combustion engine. In this case, a background noise value in each operation state of the internal combustion engine is calculated, and when the value obtained by subtracting the background noise value from the sound pressure effective value exceeds a prescribed determination value, the generation of the knocking in the internal combustion engine can be determined. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a knocking detection device for an internal combustion engine, and more particularly to a knocking detection device that can accurately detect a knocking state of an internal combustion engine based on a signal from a vibration detection sensor attached to a cylinder block of the internal combustion engine.

  In an internal combustion engine fueled with gasoline, in the combustion stroke, the mixture in the cylinder is ignited and burned with sparks from the spark plug, but the pressure in the cylinder becomes abnormally high during the flame propagation after ignition. In this case, a knocking phenomenon may occur in which an unburned portion of the air-fuel mixture is self-ignited before the flame propagation is finished and an extreme pressure rise occurs, resulting in damage to the internal combustion engine.

  Therefore, a knock control system that is a control for suppressing such knocking and realizing optimum torque and fuel consumption has been proposed. In this knock control system, a vibration detection sensor called a knock sensor is attached to the cylinder block of the internal combustion engine in order to detect whether knocking is occurring under the current operating conditions of the internal combustion engine. The presence or absence of knocking is determined by analyzing the vibration waveform of the internal combustion engine detected in (1).

  When analyzing the signal detected by this knock sensor, conventionally, the peak value of the vibration detection signal generated for each combustion cycle of the internal combustion engine has been used. That is, when the peak value is large, it is determined that knocking has occurred, and when the peak value is small, it is determined that background noise has occurred.

  However, in the conventional method of detecting the occurrence of knocking by the magnitude of the peak value of the vibration detection signal, when a large noise is generated from the internal combustion engine, a large peak value appears in the vibration detection signal, and this peak value is generated by knocking. May be misjudged. In other words, when the knocking strength is determined, the peak value of the signal from the knock sensor of each cycle is used and the magnitude is compared. However, since the knock sensor is a vibration detection sensor, other than knocking In addition, various vibrations (for example, valve seating noise and injector noise) generated from the internal combustion engine may be detected. In addition, electrical noise or the like may be detected. If these noises are small, they can be ignored, but if these noises increase for some reason, the peak value of the vibration detection signal from the knock sensor increases, and the input noise is erroneously determined to be knocking. It will end up.

  On the other hand, in order to avoid the erroneous determination in the knocking determination based on the peak value as described above, there has been proposed one utilizing the fact that a sound having a specific frequency is generated from the internal combustion engine when knocking occurs. In this proposal, as in the case where the sound generated from the internal combustion engine is heard by ear, the frequency analysis of the sound generated by the internal combustion engine collected by the microphone is performed, and knocking is determined by the peak value of the signal from the knock sensor. In addition, knocking is determined by performing determination based on sound generated from the internal combustion engine (see, for example, Patent Document 1).

JP-A-1-314925 (Claims, Fig. 1)

  However, in the knocking detection device for an internal combustion engine described in Patent Document 1, a microphone that converts sound generated in the internal combustion engine into an electrical signal in the vicinity of the internal combustion engine, and an amplifier that amplifies the electrical signal output from the microphone, A filter that extracts only a predetermined frequency required for frequency analysis of knocking from an electrical signal and an electric circuit that performs frequency analysis are required, and the cost of the knocking detection device is increased.

  Accordingly, an object of the present invention is to accurately determine knocking more suitable for human hearing without adding new sensors to the current knock control system when comparing the magnitudes of knocking sounds. An object of the present invention is to provide a knock detection device for an internal combustion engine.

  A first embodiment of the knock detection device for an internal combustion engine of the present invention that achieves the above object is a vibration detection means for detecting vibration generated in the internal combustion engine, and a period for detecting knock according to the operating state of the internal combustion engine. Is set as a gate section including at least a part of the combustion stroke of each cylinder of the internal combustion engine, and a sound pressure effective value calculation for calculating a sound pressure effective value in the gate section of a signal from the vibration detection sensor And knocking determination means for determining that knocking has occurred in the internal combustion engine when the sound pressure effective value exceeds the reference value.

  Further, a second form of the knock detection device for an internal combustion engine of the present invention that achieves the above object is a vibration detection means for detecting vibration generated in the internal combustion engine, and each of the internal combustion engine according to the operating state of the internal combustion engine. A gate section setting means for setting a period for detecting knocking including at least a part of the combustion stroke of the cylinder as a gate section, and a sound pressure for calculating a sound pressure effective value in the gate section of a signal from the vibration detection sensor An effective value calculating means, a background noise value calculating means for calculating a background noise value in each operating state of the internal combustion engine, and a value obtained by subtracting the background noise value from the sound pressure effective value is a predetermined determination value. It is characterized by comprising knocking judging means for judging that knocking has occurred in the internal combustion engine when exceeding.

  The knock detection device for an internal combustion engine according to the first aspect further includes an in-cylinder pressure detecting means for detecting a pressure in each cylinder of the internal combustion engine, and whether a gate section is a knock cycle or a noise cycle from a signal waveform from the in-cylinder pressure detecting means. Knock cycle determination means for determining whether knocking is determined when the gate section is a knock cycle.

  The knock detection device for an internal combustion engine according to the second aspect further includes an in-cylinder pressure detecting means for detecting a pressure in each cylinder of the internal combustion engine, and whether a gate section is a knock cycle or a noise cycle from a signal waveform from the in-cylinder pressure detecting means. Knock cycle determination means for determining whether knocking is determined when the gate section is a knock cycle.

  Then, the background noise value calculating means calculates the background noise value from the average value of the sound pressure effective values in the noise cycle, or from the average value of the sound pressure effective values in the operating condition in which knocking does not occur in the internal combustion engine. Can be calculated.

  Further, the determination value used by the knock determination means for determination of knocking can be a map value that increases as the engine speed of the internal combustion engine increases, and further, an effective value of background noise, It is also possible to determine knocking using a map showing the relationship with the value obtained by subtracting the background noise value from the sound pressure effective value.

  In any form, when the internal combustion engine has four cylinders and only one vibration detection means is provided in the engine, the gate section may be a section of 180 ° CA from the top dead center of each cylinder. it can. Further, when the internal combustion engine has four cylinders and two vibration detection means are provided in the engine, the gate section may be set to a section of 180 ° CA from the top dead center of each cylinder that the vibration detection means is responsible for. it can. Further, when the internal combustion engine is a V-type and the vibration detection means is provided in each bank of the engine, the gate section is set to the top dead center of each cylinder which the vibration detection means is responsible according to the number of cylinders of the engine. To an angle determined by (720 ° CA / number of cylinders).

  This gate section can be changed, and if the detection value of the vibration detection means attached to the bank of the cylinder not in the combustion stroke exceeds a predetermined threshold, the detection of the vibration detection means of this bank It is also possible for the knocking determination means to determine knocking by adding the value to the detection value of the vibration detection means attached to the bank of the cylinder in the combustion stroke.

Furthermore, to the signal output terminal of the vibration detection means,
(1) A form of connecting a bandpass filter that passes the frequency of the audible band,
(2) A form of connecting a high-pass filter that cuts a frequency in the low frequency band,
(3) A configuration in which a band pass filter that allows only a frequency band in which a peak appears in the detection signal to pass is connected,
(4) A configuration is possible in which a plurality of bandpass filters for passing and enhancing only frequencies in the audible band that are easily recognized as knocking sounds are connected.

  Further, the knocking determination means includes a knocking re-determination means, and the determination of knocking by the knocking determination means is performed when the sound pressure effective value is in the vicinity of the reference value, or the background noise value is calculated from the sound pressure effective value. When the subtracted value is in the vicinity of the determination value, the knocking re-determination means determines whether or not there is a high-frequency component of the sound pressure effective value, and if the high-frequency component is small, the knock determination means Even when the determination is made, the determination of the occurrence of knocking may be canceled, and conversely, the determination of the occurrence of knocking may be performed when the knocking determination means determines that knocking has not occurred and the high frequency component is large.

  Further, when the internal combustion engine is provided with only one vibration detection means, knocking of the same magnitude is generated in advance under the same conditions in each cylinder of the internal combustion engine, and the knocking detection output for each cylinder of the vibration detection means is provided. It is also possible to correct the output value of the vibration detecting means so that they are the same.

  According to the knock detection device for an internal combustion engine of the present invention, when comparing the magnitude of knocking sound, accurate knocking more suitable for human hearing can be performed without adding new sensors to the current knock control system. Judgment can be made.

  Hereinafter, embodiments of the present invention will be described in detail based on specific examples with reference to the accompanying drawings.

  FIG. 1 (a) shows the configuration of a first example of the first form of the knocking detecting device for an internal combustion engine of the present invention. A vibration detection sensor (hereinafter referred to as a knock sensor) 2 as vibration detection means for detecting vibration generated in the internal combustion engine 1 is attached to the cylinder block of the internal combustion engine 1, and the internal combustion engine detected by the knock sensor 2. 1 knock signal is input to the knock determination device 10. The knock determination device 10 can be configured by a data analysis device or an electronic control unit (ECU).

  The knock determination device 10 includes an engine load signal from a load detection sensor SL that detects the load of the internal combustion engine 1, an engine speed signal from the rotation speed sensor SN that detects the rotation speed of the internal combustion engine 1, and an internal combustion engine. The operating state of the internal combustion engine 1 such as a cooling water temperature signal from the temperature sensor SW for detecting the cooling water temperature 1 and an intake air temperature signal from the temperature sensor SA for detecting the temperature of the intake air provided in the intake passage of the internal combustion engine 1 A parameter is entered.

  FIG.1 (b) is a block block diagram which shows the function structure inside the knock determination apparatus 10 shown to (a). The knock determination device 10 includes a gate section setting means 3 for setting a period for detecting knocking as a gate section according to the operating state of the internal combustion engine 1, and a sound pressure in the gate section of the signal from the knock sensor 2. A sound pressure effective value calculating means 4 for calculating an effective value and a knocking determining means 5 for determining that knocking has occurred in the internal combustion engine 1 when the sound pressure effective value exceeds a reference value are provided. Since knocking occurs in the combustion stroke of each cylinder of the internal combustion engine 1, the gate section is set to include at least a part of the combustion stroke. The knock signal from the knock sensor 2 is input to the sound pressure effective value calculation means 4 through a filter 9 described later.

  Here, the knocking detection procedure by the knock determination device 10 shown in FIGS. 1A and 1B will be described with reference to the flowchart shown in FIG. This detection is performed, for example, every predetermined time.

  In step 101, first, the operation state of the internal combustion engine 1 is read based on the operation state parameter input to the knock determination device 10. Then, in accordance with the operating state of the internal combustion engine 1, a gate interval for performing knocking determination is set in step 102. Here, a case where a frequency filter that passes only a signal of a specific frequency is provided as the filter 9 provided between the knock sensor 2 and the sound pressure effective value calculation means 4 will be described. Then, the pass frequency of the frequency filter is set. The setting of the gate section and the setting of the frequency filter are for correcting a shift due to a difference in the structure of the internal combustion engine 1, the mounting position of the knock sensor 2, the operating state of the internal combustion engine 1, and the like.

  After setting the frequency filter, in step 104, the signal from knock sensor 2 is sampled and read. In the subsequent step 105, the sound pressure effective value is calculated based on the signal from the knock sensor 2 sampled and read in step 104 in the gate section set in step 102. In the next step 106, it is determined whether or not the sound pressure effective value calculated in step 105 is larger than a reference value.

  If it is determined in step 106 that (sound pressure effective value)> (reference value), the process proceeds to step 107, and knocking occurrence detection signal is output assuming that knocking has occurred in the internal combustion engine 1. On the other hand, if it is determined in step 106 that (sound pressure effective value) ≦ (reference value), the process proceeds to step 108, and a signal indicating that the internal combustion engine 1 is in a normal state without knocking is output.

  FIG. 3 shows a comparison between the conventional knocking determination method and the knocking determination method according to the first embodiment of the first aspect of the present invention. In the conventional knock determination method, the presence or absence of knocking is determined based on the knock determination threshold S shown in (b) with respect to the knock sensor signal p shown in (c). For this reason, when noise is added to the knock sensor signal p, it is determined that the peak value of the knock sensor signal p exceeds the knock determination threshold value S due to the noise, and knocking has occurred in the internal combustion engine. It was.

  On the other hand, in the first embodiment of the first mode of the present invention, the sound pressure effective value P as shown in (e) in the gate section T with respect to the knock sensor signal p shown in (c). This sound pressure effective value P is compared with the knocking determination reference value R shown in (d). This sound pressure effective value P can be calculated by the following equation (1), where p is the knock sensor signal and T is the gate interval.

  As can be seen from FIG. 3, as in the first embodiment of the first aspect of the present invention, the sound pressure effective value P calculated in each gate section T with respect to the knock sensor signal p is (d) As shown in FIG. 4, since knock determination reference value R is exceeded only when knocking actually occurs, the occurrence of knocking can be accurately detected.

  FIG. 4A shows the configuration of the second embodiment of the first mode of the knocking detection apparatus for an internal combustion engine of the present invention. Also in the second embodiment, a knock sensor 2 is attached to the cylinder block of the internal combustion engine 1 as in the first embodiment, and the engine knock signal detected by the knock sensor 2 is sent to the knock determination device 10. Entered. On the other hand, the second embodiment differs from the first embodiment in that each cylinder of the internal combustion engine 1 is provided with an in-cylinder pressure sensor 6 as an in-cylinder pressure detecting means for detecting the pressure in each cylinder. The in-cylinder pressure signal detected by the in-cylinder pressure sensor 6 is also input to the knock determination device 10.

  Also in the second embodiment, the knock determination device 10 detects the engine load signal from the load detection sensor SL for detecting the load of the internal combustion engine 1 and the rotational speed of the internal combustion engine 1 as in the first embodiment. From the engine speed signal from the rotation speed sensor SN, the cooling water temperature signal from the temperature sensor SW that detects the cooling water temperature of the internal combustion engine 1, and the temperature sensor SA that detects the temperature of the intake air provided in the intake passage of the internal combustion engine 1 The engine operating state parameters such as the intake air temperature signal are input.

  FIG. 4B is a block configuration diagram illustrating an internal functional configuration of the knock determination device 10 illustrated in FIG. Inside the knock determination device 10 of the second embodiment, as in the first embodiment, a gate section setting means 3, a sound pressure effective value calculation means 4, a knock determination means 5, and a filter 9 are provided. Yes. On the other hand, in addition to these components, the knock determination device 10 of the second embodiment is provided with a knock cycle determination means 7 for determining the knock cycle of the engine based on the in-cylinder pressure signal from the in-cylinder pressure sensor 6. ing. A signal indicating the knock cycle detected by the knock cycle determination means 7 is input to the knock detection means 5. A knock cycle is a cycle (combustion stroke) in which knocking has occurred, and a cycle in which knocking has not occurred is called a noise cycle. Also, a knock cycle may be defined as a gate section where knocking has occurred, and a noise cycle may be defined as a gate section where knocking has not occurred, and this definition will be used in the following description.

  Here, the knocking detection procedure by the knock determination device 10 shown in FIGS. 4A and 4B will be described with reference to the flowchart shown in FIG. Since the processing from step 101 to step 103 in the second embodiment is exactly the same as that in the first embodiment, the same step number is assigned and description thereof is omitted.

  In the second embodiment, in step 201 after step 103 in which the frequency filter is set, the signals from the knock sensor 2 and the in-cylinder pressure sensor 6 are sampled and stored at the same timing. In the next step 202, the signal from the knock sensor 2 stored in step 201 is read, and in step 203, the effective sound pressure value in the gate section is calculated. Thereafter, in step 204, the signal from the in-cylinder pressure sensor 6 stored in step 201 is read. Then, in the next step 205, knock determination is performed by the knock cycle determination means 7 shown in FIG. 4B, and it is determined whether the gate section is a knock cycle or a noise cycle by referring to the result.

  If it is determined in step 205 that the gate section is a knock cycle, the process proceeds to step 106, which is the same procedure as in the first embodiment, and whether or not the sound pressure effective value calculated in step 203 is larger than the reference value. Determine. If it is determined in step 106 that (sound pressure effective value)> (reference value), the process proceeds to step 107, and knocking occurrence detection signal is output assuming that knocking has occurred in the internal combustion engine 1.

  On the other hand, if it is determined in step 205 that the gate interval is not a knock cycle, the process proceeds to step 108. Further, in the determination of step 106, the process proceeds to step 108 also when (sound pressure effective value) ≦ (reference value). In step 108, a signal indicating that the internal combustion engine 1 is in a normal state without knocking is output.

  FIG. 6 shows (a) the order of combustion cylinders in a four-cylinder internal combustion engine, (b) conventional knock determination threshold value S, (c) knock sensor signal p, and (d) to (g) each cylinder. The output waveforms of the in-cylinder pressure sensors S1 to S4 provided in FIG. In the case of a four-cylinder internal combustion engine, the combustion cylinders are in the order of the first cylinder # 1, the third cylinder # 3, the fourth cylinder # 4, and the second cylinder # 2. FIG. 6 shows a case where knocking occurs in the third cylinder # 3 and knocking does not occur in the second cylinder # 2, as in FIG. 3, but noise is superimposed on the output of the knock sensor. .

  As can be seen from FIGS. 6C to 6G, when knocking occurs in the third cylinder # 3, the output waveform of the in-cylinder pressure sensor S3 of the third cylinder is disturbed (fine amplitude fluctuations near the peak of the output waveform). Therefore, the occurrence of knocking in the third cylinder # 3 can be detected, and the gate section of the third cylinder # 3 can be detected as a knock cycle. On the other hand, the knock sensor signal p includes a peak exceeding the knock determination threshold value S, but in the second cylinder # 2 in which knocking does not actually occur, the cylinder provided in the second cylinder # 2 There is no disturbance in the output of the internal pressure sensor S2. Therefore, from the waveform of the in-cylinder pressure sensor S2, knock cycle determination means 7 can detect the gate interval of second cylinder # 2 at this time as a noise cycle.

  Therefore, when the knock cycle is determined, the cylinder in which knocking has occurred can be more accurately specified by determining the magnitude of the sound pressure effective value and the reference value as in the second embodiment.

  FIG. 7A shows the configuration of the first embodiment of the second form of the knock detection device for the internal combustion engine of the present invention. The knock determination device 10 shown in FIG. 2 shows an internal functional configuration in the second mode. In the first embodiment, the sound pressure effective value of the knock signal from the knock sensor 2 in the gate section is calculated, and the presence or absence of knocking is determined by comparing this with the reference value. On the other hand, in the second embodiment, the presence or absence of knocking is determined by comparing the sound pressure effective value of the knock signal calculated from the knock sensor 2 in the gate section with the background noise in the gate section. This is different from the first embodiment.

  Inside the knock determination device 10 of the first example of the second mode, similarly to the first example of the first mode, the gate section setting unit 3, the sound pressure effective value calculation unit 4, the knock determination Means 5 and a filter 9 are provided. In addition to these components, the knock determination device 10 according to the first embodiment of the second mode includes a background noise value calculation means 8 for calculating a background noise value from an operating state parameter of the internal combustion engine. Is provided. The background noise signal detected by the background noise value calculation unit 8 is input to the knocking detection unit 5.

  Here, the knocking detection procedure by the knock determination device 10 shown in FIG. 7A will be described with reference to the flowchart shown in FIG. Since the processing from step 101 to step 105 in the first example of the second mode is exactly the same as that of the first example of the first mode, the same step number is assigned and description thereof is omitted. To do.

  In the first embodiment of the second mode, the background noise value is calculated in step 301 after step 105 in which the sound pressure effective value in the gate section is calculated. Since there are several methods for calculating the background noise value, this calculation method will be described later. In the next step 302, a difference ΔN between the sound pressure effective value in the gate section obtained in step 105 and the background noise value obtained in step 301 is calculated. In step 303, it is determined whether or not the difference ΔN between the sound pressure effective value and the background noise value in the gate section is larger than the knock determination value.

  If it is determined in step 303 that (ΔN)> (determination value), the process proceeds to step 304 and a knocking detection signal is output assuming that knocking has occurred in the internal combustion engine 1. On the other hand, if (ΔN) ≦ (determination value) in the determination in step 303, the process proceeds to step 305, and a signal indicating that the internal combustion engine 1 is in a normal state without occurrence of knocking is output.

  In the second embodiment, since the magnitude of the background noise of the internal combustion engine 1 is taken into consideration when determining the occurrence of knocking, a small knocking that is buried in the background noise and causes no auditory problem is determined to be knocking. Therefore, it is possible to determine knocking that is close to the determination of knocking by a human ear.

  FIG. 7B shows the configuration of the second embodiment of the second form of the knock detection device for the internal combustion engine of the present invention. The knock determination device 10 shown in FIG. 2 shows an internal functional configuration in the second mode. Inside the knock determination device 10 of the second example of the second mode, as in the second example of the first mode, the gate section setting unit 3, the sound pressure effective value calculation unit 4, the knock determination Means 5, knock cycle determination means 7 and filter 9 are provided. In addition to these components, the knock determination device 10 according to the second embodiment of the second mode includes a background noise value calculation means 8 that calculates a background noise value from an operating state parameter of the internal combustion engine. Is provided. The background noise signal detected by the background noise value calculation unit 8 is input to the knocking detection unit 5.

  Here, the knocking detection procedure by the knock determination device 10 shown in FIG. 7B will be described with reference to the flowchart shown in FIG. The processing from step 101 to step 103 in the second example of the second mode is exactly the same as that of the first example of the first mode, and the processing from step 201 to 203 is the same as that of the first mode. Since it is the same as that of the second embodiment, the same step number is assigned and its description is omitted.

  In the second example of the second mode, in step 301 after step 203 in which the sound pressure effective value in the gate section is calculated, the background noise value is calculated in the same manner as in the first example of the second mode. I do. In the next step 302, a difference ΔN between the sound pressure effective value in the gate section obtained in step 203 and the background noise value obtained in step 301 is calculated.

  After calculating the difference ΔN between the sound pressure effective value and the background noise value in the gate section in this way, the in-cylinder pressure stored in step 201 is stored in step 204 as in the second embodiment of the first mode. The signal from the sensor 6 is read. Then, in the next step 205, knock determination is performed by the knock cycle determination means 7 shown in FIG. 4B, and it is determined whether the gate interval is a knock cycle or a noise cycle by referring to the result.

  If it is determined in step 205 that the gate section is a knock cycle, the process proceeds to step 303 which is the same procedure as in the first embodiment of the second mode. In step 303, it is determined whether or not the difference ΔN between the sound pressure effective value and the background noise value in the gate section is larger than the knock determination value. If it is determined in step 303 that (ΔN)> (determination value), the process proceeds to step 304 and a knocking detection signal is output assuming that knocking has occurred in the internal combustion engine 1.

  On the other hand, if it is determined in step 205 that it is not a knock cycle, or if (ΔN) ≦ (determination value) in step 303, the process proceeds to step 305, and the internal combustion engine 1 is in a normal state where knocking does not occur. A certain signal is output.

  Here, a method for calculating the above-described background noise value will be described.

  The first method for calculating the background noise value is that the sound pressure effective value in the gate interval (noise cycle) where the background noise value calculation means 8 shown in FIGS. This is a method of calculating an average value of the above and making this a background noise value. The average value of the sound pressure effective values at this time corresponds to the engine sound of the internal combustion engine 1 that is always heard as the background.

  The gate section where knocking has not occurred can be determined from the output of the knock sensor, but can be determined more accurately when the cylinder pressure sensor 6 is provided in the internal combustion engine 1. That is, when the knock cycle determining means 7 shown in FIG. 7B determines that it is a noise cycle, the background noise value calculating means 8 calculates the average value of the sound pressure effective values in this noise cycle. Is a background noise value, the background noise value can be calculated more accurately.

  The second method for calculating the background noise value is that the background noise value calculation means 8 shown in FIGS. 7A and 7B is an average of sound pressure effective values under operating conditions in which knocking does not occur in the internal combustion engine 1. This is a method of calculating the background noise value from the value. In this case, an operating condition in which knocking does not occur in the internal combustion engine 1 is set by setting the ignition timing of the internal combustion engine 1, and the background noise is calculated from the average value of the effective sound pressure values in this operating state. The detection of the non-knock state by the knock sensor 2 and the detection of the noise cycle by the in-cylinder pressure sensor 6 are unnecessary.

  According to the third method of calculating the background noise value, a background noise value map is created in advance according to the operating state of the internal combustion engine, and the background noise value is referred to by referring to the map according to the operating state of the internal combustion engine. Is the way to get. FIG. 10A shows an example of this map. In this example, the background noise value increases as the rotational speed of the internal combustion engine increases.

  The reason for this will be explained. As the engine speed increases, the engine noise increases and the background noise increases. In this case, even when knocking has occurred in the internal combustion engine, if the knocking sound is small, it will not be heard due to background noise, and if the knocking sound does not exceed a certain level, it will not be heard as a knocking sound. Based on such a situation, as shown in FIG. 10A, the range that can be heard as the knocking sound and the range that is larger than the background noise but cannot be heard as the knocking sound (shown by hatching) are shown in the map. Set it. That is, the determination value used by the knocking determination means 5 for determining knocking is a map value that increases as the rotational speed of the internal combustion engine increases as shown in FIG. 10B. It shows that it is.

  On the other hand, when the types of internal combustion engines are different, the engine sound (background noise value) is different even if the engine speed is the same. Therefore, the engine sound of another internal combustion engine cannot be determined only with the map shown in FIG. Therefore, a general-purpose map as shown in FIG. 11 is created in which the horizontal axis of the map is the background noise value level and the vertical axis is the difference between the sound pressure effective value and the background noise value (effective value) in the gate section. Is possible. The map shown in FIG. 11 includes a range that can be heard as a knocking sound and a range that is larger than the background noise but cannot be heard as a knocking sound (indicated by hatching).

  For example, consider a case where there are two internal combustion engines E1 and E2, and the value of the difference ΔN between the effective values of the two internal combustion engines E1 and E2 at an engine speed of 3000 rpm is Y. Then, it is assumed that the background noise value of the internal combustion engine E1 is X1, and the background noise value of the internal combustion engine E2 is X2 larger than X1. In this case, since the value of the effective value difference ΔN at the engine speed 3000 rpm of the internal combustion engine E1 is within a range that can be heard as a knocking sound in the map of FIG. 11, it is determined that knocking has occurred in the internal combustion engine E1. . On the other hand, the value ΔN of the effective value at the engine speed 3000 rpm of the internal combustion engine E2 is larger than the background noise, but is in a range that cannot be heard as the knocking sound in the map of FIG. Is determined not to occur.

  Thus, the knocking determination means 5 determines the knocking using the map showing the relationship between the effective value of the background noise as shown in FIG. 11 and the value obtained by subtracting the background noise value from the sound pressure effective value. If it performs, knocking determination can be performed irrespective of the kind of internal combustion engine.

  Here, the knocking detection procedure in the third example of the second mode by the knock determination device 10 using the map of FIG. 10 will be described with reference to the flowchart shown in FIG. Note that the processing from step 101 to step 103 in the third example of the second mode is exactly the same as that of the first example of the first mode, so the same step numbers are assigned and description thereof is omitted. To do.

  In the third embodiment of the second mode, the signals from the knock sensor 2 and the in-cylinder pressure sensor 6 are sampled and stored in step 201 after step 103 in which the frequency filter is set. Then, in the next step 204, the signal from the in-cylinder pressure sensor 6 is read, and in the following step 205, knocking is determined by the knock cycle determining means 7 shown in FIG. 4 (b), and the result is referred to. It is determined whether the gate interval is a knock cycle or a noise cycle.

  If it is determined in step 205 that the engine is in the knock cycle, the process proceeds to step 401, and the signal from the knock sensor 2 stored in step 201 is read. In the following step 402, the sound pressure effective value in the gate section set in step 102 is calculated based on the signal from the knock sensor 2 sampled and read in step 401. In the next step 403, a determination value corresponding to the engine operating state read in step 101 is calculated based on the map shown in FIG. On the other hand, if it is determined in step 205 that it is not a knock cycle, the process proceeds to step 404 where the average value of the sound pressure effective values of the noise cycle is calculated and the process proceeds to step 302 as a background noise value.

  In the next step 302, a difference ΔN between the sound pressure effective value in the gate section obtained in step 402 and the background noise value obtained in step 404 is calculated. After calculating the difference ΔN between the sound pressure effective value and the background noise value in the gate section in this way, the process proceeds to step 303 which is the same procedure as in the first example of the second mode. In step 303, it is determined whether or not the difference ΔN between the sound pressure effective value and the background noise value in the gate section is larger than the knock determination value calculated in step 403. If it is determined in step 303 that (ΔN)> (determination value), the process proceeds to step 304 and a knocking detection signal is output assuming that knocking has occurred in the internal combustion engine 1. On the other hand, if (ΔN) ≦ (determination value) in the determination in step 303, the process proceeds to step 305, and a signal indicating that the internal combustion engine 1 is in a normal state without occurrence of knocking is output.

  Next, the knocking detection procedure in the fourth example of the second mode by the knock determination device 10 using the map of FIG. 11 will be described with reference to the flowchart shown in FIG. The processing from step 101 to step 103 and the processing from step 201 to step 404 (except for the processing of step 403) in the fourth example of the second mode are the same as those of the third example of the second mode. Since they are exactly the same, the same step numbers are given and their explanations are omitted.

  In the third embodiment of the second mode, if it is determined in step 205 that the knock cycle is present, the signal from knock sensor 2 stored in step 201 is read in step 401, and then in step 402 in the gate section. When the sound pressure effective value is calculated and it is determined in step 205 that it is not a knock cycle, a background noise value is calculated in step 404.

  On the other hand, in the fourth example of the second mode, in step 501 following step 402 or step 404, the difference ΔN between the sound pressure effective value and the background noise value in the gate section is calculated, and this effective value is calculated. The relationship between the value difference ΔN and the effective value of the background noise is applied to the knocking sound map of FIG. 11, and the range indicated by the effective value difference ΔN and the effective value of the background noise is heard as the knocking sound of FIG. It is determined in step 502 whether or not

  If it is determined in this determination that the point indicated by the difference ΔN between the effective values and the effective value of the background noise is within the range that can be heard as the knocking sound in FIG. 11, the routine proceeds to step 503 where knocking has occurred in the internal combustion engine 1. As a result, a detection signal of occurrence of knocking is output. On the other hand, if the point indicated by the difference ΔN in the effective value and the effective value of the background noise is not within the range that can be heard as the knocking sound in FIG. 11 in the determination in step 502, the process proceeds to step 504, and the internal combustion engine 1 Output a signal that is not normal.

  Next, a method for setting the gate section according to the type of the internal combustion engine will be described.

  First, when the internal combustion engine is an in-line four cylinder and only one knock sensor is provided in the cylinder block of this internal combustion engine, the gate section is set to a section of 180 ° CA from the top dead center of each cylinder. . Further, when the internal combustion engine is an in-line 4-cylinder engine and two knock sensors are provided in the cylinder block of the internal combustion engine, the gate section is 180 ° from the top dead center of each cylinder that the two knock sensors respectively handle. Set to CA section.

  On the other hand, when the internal combustion engine is a V-type multi-cylinder internal combustion engine and a knock sensor is provided in each bank of the V-type engine, each knock sensor takes charge of the gate section according to the number of cylinders of the V-type engine. The interval is set from the top dead center of each cylinder to an angle determined by (720 ° CA / number of cylinders).

  The gate interval set in this way can be changed in length. This is because the S / N ratio of the knock signal from the knock sensor is improved by changing the length of the gate section and calculating the effective value only in the part of the stroke where the vibration due to knocking of the internal combustion engine is noticeable. Because it can.

  Further, in order to increase the detection reliability of the knock detection device for the V-type internal combustion engine, when the detection value of the knock sensor attached to the bank of the cylinder not in the combustion stroke exceeds a predetermined threshold, this bank A method of adding the detection value of the knock sensor to the detection value of the knock sensor attached to the bank of the cylinder in the combustion stroke is conceivable. In this way, since the level of the knocking detection signal input to the knocking determination means when knocking occurs increases, the certainty in determining knocking increases.

The filter 9 provided between the knock sensor 2 and the sound pressure effective value calculation means 4 in FIGS. 1B, 4B, 7A and 7B has the following configuration. It can be.
(1) Bandpass filter of 20 Hz to 20 kHz The knock signal output from the knock sensor includes signals of various frequency bands. However, since the frequency band that can be heard by the human ear is limited, it is useless from the viewpoint of matching the human sense of hearing to determine knocking by analyzing a signal in a frequency band that cannot be heard by the human ear as knocking. . Therefore, the knock signal from the knock sensor is passed through a bandpass filter that allows only the audible frequency band (20 Hz to 20 kHz) to pass through so that the detection of knocking can be more matched to human hearing. And the effective value of the signal of the frequency of the obtained audible frequency band is calculated, and knocking determination is performed based on this effective value.
(2) High-pass filter It is known that even if knocking occurs in an internal combustion engine, the frequency in the low frequency band of about 4 kHz or less has little difference in the effective value in the knock cycle and the noise cycle. Therefore, a low frequency band of 4 kHz or less that is not different between the knock cycle and the noise cycle is cut by a high-pass filter to improve the S / N ratio of the knock signal.
(3) Band-pass filter that passes only the frequency of the frequency band where the peak appears in the detection signal The knock signal output from the knock sensor may have a peak value in a certain frequency band determined by the cylinder bore diameter of the internal combustion engine. Are known. In the frequency band not including the peak value, it is difficult for the effective value to be different between the knock cycle and the noise cycle. Therefore, the S / N ratio is better when knocking is detected in the frequency band including this peak value, and the knocking detection accuracy is higher. For this reason, the detection accuracy of knocking is improved by connecting a bandpass filter that passes only the frequency of the frequency band where the peak appears in the detection signal to the output of the knock sensor and cutting it even in the audible frequency band.
(4) A plurality of band-pass filters for emphasizing by passing only frequencies in the audible band that are easily recognized as knocking sounds. The human ear has a frequency band of 2 kHz to 4 kHz as shown in FIG. The sound is well audible, but it has the characteristic of having an auditory characteristic that it is difficult to hear lower and higher frequencies. Therefore, if the frequency characteristic of the output signal of the knock sensor 2 is attenuated according to the human auditory characteristic, knocking in the frequency band that can be heard by the human ear can be detected.

  FIG. 14B shows this embodiment, and a plurality of filters, in this embodiment, three band-pass filters 9A, 9B, and 9C are provided on the output side of the knock sensor 2. FIG. For example, the pass band of the band pass filter 9A is 2 to 8 kHz, the pass band of the band pass filter 9B is 8 to 16 kHz, and the pass band of the band pass filter 9C is 16 to 20 kHz. The output of the knock sensor 2 is branched into three and input to these filters 9A to 9C, and the output of the bandpass filter 9B is connected to an attenuator 11 that attenuates the output by a factor of 0.8. An attenuator 12 for attenuating the output by a factor of 0.5 is connected to the output of the pass filter 9C. The outputs of the band-pass filter 9A and the attenuators 11 and 12 are combined and input to the sound pressure effective value calculation means.

  As a result, the level of the knock signal output from the bandpass filter 9A does not change, but the level of the knock signal output from the bandpass filter 9B decreases to 80%, and the knock signal output from the highpass filter 9C. The level drops to 50%. Therefore, the knock signal after being synthesized by the synthesizer 13 has a frequency characteristic close to the audibility characteristic of the human ear, and the knock determination means 5 of any of the above-described embodiments also uses the human ear. It is possible to detect a knocking sound that is easy to hear.

  By the way, when it is judged that knocking occurring in the internal combustion engine is audible or not audible to humans, if the knocking level is in the vicinity of the judgment boundary, the knocking judging means determines that knocking has occurred due to the frequency characteristics of knocking. Even if it is determined, it may not be heard, or it may be heard even when the knock determination means determines that knocking has not occurred. The reason for this is that the engine sound that is originally heard as background noise is a low frequency sound, so that a higher frequency knocking sound is easier to hear.

  For this reason, the knocking determination means includes a knocking re-determination means, and the determination of knocking by the knocking determination means is performed when the sound pressure effective value is in the vicinity of the reference value or the background noise value is calculated from the sound pressure effective value. When the subtraction is performed in a state where the value is in the vicinity of the determination value, the knocking re-determination unit can re-determine the occurrence of knocking. The knocking re-determination means determines whether or not there is a high-frequency component of the sound pressure effective value when knocking determination is performed near the reference value or the determination value. And, if the high frequency component of the sound pressure effective value is small, even when the knocking determination means determines that knocking has occurred, cancels the determination of knocking occurrence, and conversely, when the knocking determination means determines that knocking has not occurred However, if the high frequency component is large, the occurrence of knocking is determined.

  By providing this knocking re-determination means, the presence or absence of the occurrence of knocking can be made closer to the determination heard with the human ear.

  When the four-cylinder internal combustion engine has only one knock sensor, the knock sensor is generally installed between the second cylinder # 2 and the third cylinder # 3. In this case, even if knocking of the same magnitude occurs in each cylinder, the output of the knock sensor becomes large in the cylinders close to the knock sensor (second and third cylinders # 2 and # 3), and the cylinder far from the knock sensor ( In the first and fourth cylinders # 1, # 4), the vibration is attenuated before reaching the knock sensor, so that the output of the knock sensor is reduced. In order to correct this difference, knocking of the same magnitude is generated in advance under the same conditions in each cylinder, and the output of the vibration detecting means is set so that the knocking detection output for each cylinder of the knock sensor at this time becomes the same. The value can also be corrected by sound pressure effective value calculation means.

  According to the knock detection device for an internal combustion engine of the present invention, when comparing the magnitude of knocking sound generated in the internal combustion engine, it is more suitable for human hearing without adding new sensors to the current knock control system. Accurate determination of knocking can be performed.

(A) is a block diagram which shows the structure of the knock detection apparatus of the internal combustion engine of 1st Example of the 1st form of this invention, (b) is the inside of the knock detection apparatus of the internal combustion engine shown to (a). It is a block block diagram which shows a function structure. It is a flowchart which shows the knocking detection procedure in the knocking detection apparatus of the internal combustion engine of 1st Example of the 1st form of this invention. It is a diagram which compares and shows the conventional knocking determination method and the knocking determination method of the 1st Example of the 1st form of this invention. (A) is a block diagram which shows the structure of the knocking detection apparatus of the internal combustion engine of 2nd Example of the 1st form of this invention, (b) is the inside of the knocking detection apparatus of the internal combustion engine shown to (a). It is a block block diagram which shows a function structure. It is a flowchart which shows the knocking detection procedure in the knocking detection apparatus of the internal combustion engine of 2nd Example of the 1st form of this invention. It is a wave form diagram which shows the waveform of the cylinder pressure which performs the determination of a knock cycle and a noise cycle for every cylinder in the knock detection apparatus of the internal combustion engine of 2nd Example of the 1st form of this invention. (A) is a block configuration diagram showing an internal functional configuration of the knock detection device for an internal combustion engine of the first embodiment of the second mode of the present invention, and (b) is a second block diagram of the second mode of the present invention. It is a block block diagram which shows the function structure inside the knocking detection apparatus of the internal combustion engine of an Example. It is a flowchart which shows the knocking detection procedure of the knocking detection apparatus of the internal combustion engine of 1st Example of the 2nd form of this invention. It is a flowchart which shows the knocking detection procedure of the knocking detection apparatus of the internal combustion engine of 2nd Example of the 2nd form of this invention. (A) is a figure which shows the sound pressure effective value map used in the knocking detection apparatus of the internal combustion engine of this invention, (b) is a figure which shows the map of the knock determination value with respect to the engine speed based on the map of (a). . It is a figure which shows the general purpose sound pressure effective value map used in the knocking detection apparatus of the internal combustion engine of this invention. It is a flowchart which shows the knocking detection procedure of the knocking detection apparatus of the internal combustion engine of 3rd Example of the 2nd form of this invention. It is a flowchart which shows the knocking detection procedure of the knocking detection apparatus of the internal combustion engine of the 4th Example of the 2nd form of this invention. (A) is a figure which shows the auditory characteristic with respect to a human frequency, (b) is a block diagram explaining the structure which changes the frequency characteristic of the knock signal from a knock sensor according to the auditory characteristic of (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Vibration detection means (knock sensor)
3 ... Gate section setting means 4 ... Sound pressure effective value calculation means 5 ... Knocking determination means 6 ... In-cylinder pressure detection means (in-cylinder pressure sensor)
7 ... Knock cycle determination means 8 ... Background noise calculation means 9, 9A, 9B, 9C ... Filter 10 ... Knock determination devices 11, 12 ... Attenuator 13 ... Synthesizer

Claims (19)

Vibration detecting means for detecting vibration generated in the internal combustion engine;
Gate interval setting means for setting a period for detecting knocking according to the operating state of the internal combustion engine as a gate interval including at least a part of the combustion stroke of each cylinder of the internal combustion engine;
A sound pressure effective value calculation means for calculating a sound pressure effective value in the gate section of the signal from the vibration detection sensor;
Knocking determination means for determining that knocking has occurred in the internal combustion engine when the sound pressure effective value exceeds a reference value;
A knocking detection apparatus for an internal combustion engine, comprising: The knock detection device for the internal combustion engine further includes:
In-cylinder pressure detecting means for detecting the pressure in each cylinder of the internal combustion engine;
From the signal waveform from the in-cylinder pressure detection means, provided with a knock cycle determination means for determining whether the gate section is a knock cycle or a noise cycle,
2. The knock detection device for an internal combustion engine according to claim 1, wherein the knock determination unit performs the knock determination when the gate section is in a knock cycle. 3. Vibration detecting means for detecting vibration generated in the internal combustion engine;
A gate section setting means for setting a period for detecting knocking including at least a part of a combustion stroke of each cylinder of the internal combustion engine as a gate section according to an operating state of the internal combustion engine;
A sound pressure effective value calculation means for calculating a sound pressure effective value in the gate section of the signal from the vibration detection sensor;
A background noise value calculating means for calculating a background noise value in each operating state of the internal combustion engine;
Knocking determination means for determining that knocking has occurred in the internal combustion engine when a value obtained by subtracting the background noise value from the sound pressure effective value exceeds a predetermined determination value;
A knocking detection apparatus for an internal combustion engine, comprising: The knock detection device for the internal combustion engine further includes:
In-cylinder pressure detecting means for detecting the pressure in each cylinder of the internal combustion engine;
From the signal waveform from the in-cylinder pressure detection means, provided with a knock cycle determination means for determining whether the gate section is a knock cycle or a noise cycle,
4. The knock detection device for an internal combustion engine according to claim 3, wherein the knocking determination unit determines the knocking when the gate section is in a knock cycle. 5.   The knock detection device for an internal combustion engine according to claim 3 or 4, wherein the background noise value calculation means calculates the background noise value from an average value of sound pressure effective values in the noise cycle.   5. The internal combustion engine according to claim 3, wherein the background noise value calculation means calculates the background noise value from an average value of sound pressure effective values under an operating condition in which knocking does not occur in the internal combustion engine. Engine knocking detection device.   5. The internal combustion engine according to claim 3, wherein the determination value used by the knocking determination unit for determination of knocking is a map value that increases as the engine speed of the internal combustion engine increases. Engine knocking detection device.   The determination value used for determination of knocking by the knocking determination means is further used using a map indicating a relationship between an effective value of background noise and a value obtained by subtracting the background noise value from the effective sound pressure value. 8. The knock detection device for an internal combustion engine according to claim 7, wherein knocking is determined. The internal combustion engine has four cylinders;
Only one vibration detection means is provided in the engine,
The knock detection device for an internal combustion engine according to any one of claims 1 to 8, wherein the gate section is a section of 180 ° CA from the top dead center of each cylinder. The internal combustion engine has four cylinders;
Two vibration detection means are provided in the engine,
9. The knock detection device for an internal combustion engine according to claim 1, wherein the gate section is a section of 180 ° CA from the top dead center of each cylinder that the vibration detecting means is responsible for. The internal combustion engine is V-shaped;
The vibration detection means is provided in each bank of the engine,
The gate section is a section from the top dead center of each cylinder that the vibration detecting means is responsible to an angle determined by (720 ° CA / number of cylinders) according to the number of cylinders of the engine. The knock detection device for an internal combustion engine according to any one of 1 to 8.   The knock detection device for an internal combustion engine according to any one of claims 9 to 11, wherein the gate section is changeable.   If the detection value of the vibration detection means attached to the bank of the cylinder not in the combustion stroke exceeds a predetermined threshold, the detection value of the vibration detection means of this bank is attached to the bank of the cylinder in the combustion stroke The knocking detection device for an internal combustion engine according to claim 11, wherein the knocking determination means determines knocking by adding to the detected value of the vibration detection means.   14. The knock detection device for an internal combustion engine according to claim 1, wherein a band-pass filter that allows a frequency in an audible band to pass is connected to a signal output terminal of the vibration detection unit.   14. The knock detection device for an internal combustion engine according to claim 1, wherein a high-pass filter that cuts a frequency in a low frequency band is connected to a signal output terminal of the vibration detection means.   The band-pass filter which passes only the frequency of the frequency band in which the peak appears in a detection signal is connected to the signal output terminal of the said vibration detection means, The Claim 1 characterized by the above-mentioned. An internal combustion engine knock detection device.   14. A plurality of band-pass filters for passing and enhancing only a frequency in an audible band that is easily recognized as a knocking sound are connected to a signal output terminal of the vibration detecting means. The knock detection device for an internal combustion engine according to any one of the above. The knocking determination means is further provided with a knocking re-determination means,
In this knocking re-determination means, the determination of knocking by the knocking determination means is such that the sound pressure effective value is in the vicinity of a reference value, or a value obtained by subtracting the background noise value from the sound pressure effective value is When it is performed in a state in the vicinity of the determination value, it is determined whether or not there is a high frequency component of the sound pressure effective value, and even if the knock determination means determines that knocking has occurred, knocking is performed if the high frequency component is small. The determination of occurrence of knocking is canceled, and conversely, even when the knocking determination means determines that knocking has not occurred, the occurrence determination of knocking is performed if the high frequency component is large. The knock detection device for an internal combustion engine according to claim 1.   Knock of the same magnitude is generated in advance in each cylinder of the internal combustion engine under the same conditions, and the output value of the vibration detection means is corrected so that the knock detection output for each cylinder of the vibration detection means becomes the same. The knock detection device for an internal combustion engine according to claim 9, wherein the knock detection device is configured as described above.

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