JP2009052466A - Knock detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a knock detection device capable of performing an accurate knock determination. <P>SOLUTION: The knock detection device includes a vibration detecting means, a characteristic value calculating means, a median calculating means, a standard deviation calculating means, a knock determining means, and a steady noise switch determining means. The knock determining means determines whether a knock is occurring based on a relationship among a characteristic value calculated by the characteristic value calculating means, a median, and a standard deviation. The steady noise switch determining means determines whether a steady noise occurring in the internal combustion engine is switched. The median calculating means, when the steady noise switch determining means determines that the steady noise is switched, sets the characteristic value calculated by the characteristic value calculating means to the median. Thus, even in case that a knock occurs in a transition period immediately after the steady noise being switched, the accurate knock determination can be performed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a knocking detection device for detecting knocking of an internal combustion engine.

  Knocking of an internal combustion engine is a phenomenon in which gas in the combustion chamber vibrates due to self-ignition of unburned gas in the combustion chamber, and this vibration is transmitted to the entire engine such as a cylinder block. When such knocking occurs vigorously, unpleasant vibrations are generated and the engine body is damaged. Therefore, an ECU (Electronic Control Unit) of the internal combustion engine needs to accurately detect the occurrence of knocking. The ECU detects knocking based on a detection signal from a knock sensor attached to the side surface of the cylinder block. However, the knock sensor detects not only the frequency of occurrence of knocking but also the frequency of stationary noise. Therefore, the ECU needs to remove the influence of noise from the frequency detected by the knock sensor in order to accurately detect knocking.

  For example, Patent Document 1 describes a knock determination device for an internal combustion engine that includes means for calculating a variable representing noise characteristics for each predetermined crank angle section and noise determination means for determining a noise occurrence state. Yes. Patent Document 2 discloses an engine knock control device that includes an in-cylinder pressure detection unit, a knock determination unit, and a frequency-specific strength detection unit that varies a frequency band for which the frequency-specific strength is detected between cylinders. Are listed. Patent Document 3 describes a knocking detection apparatus including a filter unit that extracts signal components in different frequency bands from a knock sensor, and a knock determination unit. Patent Document 4 describes an internal combustion engine knock control device including characteristic switching means for switching a filter characteristic in a signal extraction means in a specific characteristic switching operation region in a specific operation region based on a noise determination result. Patent Document 5 describes a knocking detection device including a determination unit that determines whether or not knocking is performed based on a predetermined determination value for a frequency output for each cylinder.

JP 2006-169996 A JP 2005-098192 A JP 2004-317207 A JP 2001-173508 A JP-A-5-195929

  However, in the knocking detection method that removes the noise frequency from the frequency detected by the knock sensor, the knocking vibration intensity is weakened when the noise frequency matches the knocking occurrence frequency. It may not be possible to In addition, since the base vibration level (background level) and the detected value of the vibration intensity of knocking that are the basis for knock determination change depending on the excluded frequency, the generation of the knocking determination level and the determination result vary. Furthermore, in the case of noise that is superimposed on a plurality of frequency bands, the influence of noise cannot be removed by simply removing the specific noise frequency. In addition, according to a general knocking detection method, the vibration intensity is smoothed (averaged) for each ignition to create a base vibration level (background level) for knock determination. During the period from when the bank ground level becomes stable, accurate knock determination cannot be performed. Regarding these points, Patent Documents 1 to 5 do not discuss anything.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a knocking detection device capable of performing accurate knock determination.

  According to one aspect of the present invention, there is provided a knocking detection device for detecting knocking generated in an internal combustion engine, the vibration detection means for detecting vibration generated in the internal combustion engine, and the detection device in a predetermined crank angle period. Based on a detection signal, feature value calculating means for calculating a characteristic value characterizing vibration intensity of vibration generated in the internal combustion engine in the predetermined crank angle period, and frequency distribution of the characteristic value every time the characteristic value is calculated A median value calculating means for calculating the median value, a standard deviation calculating means for calculating a standard deviation of a frequency distribution of the feature value each time the feature value is calculated, and the feature value calculated by the feature value calculating means Knocking determination means for determining whether knocking has occurred or not based on the relationship between the median and the standard deviation, and occurring in the internal combustion engine A stationary noise switching determination unit that determines whether or not the normal noise has been switched, and the median value calculation unit, when the stationary noise switching determination unit determines that the stationary noise has been switched, The feature value calculated by the feature value calculation means is set as the median value.

  The knocking detection device is a device for detecting knocking that has occurred in the internal combustion engine. The knocking detection device includes vibration detection means, feature value calculation means, median value calculation means, standard deviation calculation means, knocking determination means, and steady noise switching determination means. The vibration detecting means is a knock sensor, for example, and detects vibration generated in the internal combustion engine. The feature value calculation means, median value calculation means, standard deviation calculation means, knocking determination means, and steady noise switching determination means are, for example, an ECU (Electronic Control Unit). The characteristic value calculating means calculates a characteristic value characterizing the vibration intensity of the vibration generated in the internal combustion engine during the predetermined crank angle period based on a detection signal from the detection device during the predetermined crank angle period. The median value calculation means calculates the median value of the frequency distribution of the feature values each time the feature values are calculated. The standard deviation calculating means calculates the standard deviation of the frequency distribution of the feature value every time the feature value is calculated. The knocking determination unit determines whether knocking has occurred based on the relationship between the feature value calculated by the feature value calculation unit, the median value, and the standard deviation. The stationary noise switching means determines whether or not the stationary noise generated in the internal combustion engine has been switched. Here, the median value calculation means sets the feature value calculated by the feature value calculation means as the median value when the steady noise switching determination means determines that the steady noise has been switched. .

  According to the knocking detection device of the present invention, immediately after the stationary noise is switched, the error between the characteristic value and the median value of the stationary noise immediately after the switching can be reduced. Even when knocking occurs during the period, accurate knock determination can be performed. Further, the knocking detection device of the present invention does not exclude noise frequencies. Therefore, compared with a general knocking detection device that detects knocking by excluding the noise frequency, the knocking detection device of the present invention does not knock even when the noise frequency matches the knocking frequency. The detectability can be improved, and variations in the determination result can be prevented.

  In a preferred embodiment of the knocking detection device, the feature value calculation means calculates an integral value of vibration intensity of vibration generated in the internal combustion engine in the predetermined crank angle period as the feature value.

  Preferred embodiments of the present invention will be described below with reference to the drawings.

[Configuration of internal combustion engine]
FIG. 1 is a cross-sectional view of an internal combustion engine 1 to which a knocking detection device according to an embodiment of the present invention is applied.

  The internal combustion engine 1 is an engine provided with a plurality of cylinders. As shown in FIG. 1 (a), the internal combustion engine 1 mainly includes a cylinder block 2, a piston 3, and a water jacket 4. The cylinder block 2 is provided with a cylinder wall 2a in series. A cylinder bore is formed in the cylinder wall 2a so that the piston 3 can be moved up and down. A block side wall 2b is formed so as to surround the cylinder wall 2a. The cylinder block 2 is made of, for example, aluminum (Al). A water jacket 4 is formed between the cylinder wall 2a and the block side wall 2b. The cylinder wall 2a is radiated and cooled by the cooling water circulating through the water jacket 4.

  A spark plug 13 is provided in the head portion 19 of the internal combustion engine 1. An intake passage 14 and an exhaust passage 16 are connected to the combustion chamber 18 of the internal combustion engine 1. Further, the internal combustion engine 1 is a direct injection internal combustion engine, for example, and is provided with a fuel injection valve 21 that injects fuel directly into the combustion chamber 18.

  The intake passage 14 circulates intake air (air) to be supplied to the internal combustion engine 1. The fuel injection valve 21 injects fuel into the combustion chamber 18. The injection amount of the fuel injection valve 21 is controlled by a control signal S21 from the ECU 50. In the combustion chamber 18, the air-fuel mixture of the supplied intake air (air) and fuel is combusted by being ignited by ignition of the spark plug 13. This combustion causes the piston 3 to reciprocate. This reciprocating motion is transmitted to the crankshaft 12 via the connecting rod 11, and the crankshaft 12 rotates. The ignition timing of the spark plug 13 is controlled by a control signal S13 from the ECU 50. Exhaust gas generated by the combustion in the combustion chamber 18 is discharged to the exhaust passage 16. A crank angle sensor 20 is installed in the vicinity of the crankshaft 12. The crank angle sensor 20 detects the rotation angle of the crankshaft 12, and supplies a detection signal S20 corresponding to the detected rotation angle to the ECU 50.

  The combustion chamber 18 is provided with an intake valve 15 and an exhaust valve 17. The intake valve 15 controls opening / closing of the intake passage 14 and the combustion chamber 18 by opening and closing. Further, the exhaust valve 17 controls opening / closing of the exhaust passage 16 and the combustion chamber 18 by opening and closing.

  A knock sensor 6 is attached to the wall surface of the cylinder block 2, specifically, to the block side wall 2b. If the temperature and pressure in the combustion chamber 18 rise too much, the unburned gas will self-ignite. At this time, the gas in the combustion chamber 18 vibrates. This vibration is transmitted to the entire engine such as the cylinder block 2. This phenomenon is called knocking. If knocking occurs violently, unpleasant vibrations are generated, and output is reduced due to energy loss, and fuel consumption is reduced. Knock sensor 6 senses the vibration of internal combustion engine 1 and supplies detection signal S6 corresponding to the sensed vibration to ECU 50.

  The ECU (Electronic Control Unit) 50 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like (not shown). The ECU 50 acquires detection signals from various sensors provided in the internal combustion engine 1 and controls the internal combustion engine 1 based on the detection signals. In the knock detection device according to the present embodiment, the ECU 50 includes a filter circuit and an amplifier circuit. The ECU 50 obtains the vibration intensity of the internal combustion engine 1 based on the detection signal S6 from the knock sensor 6, and detects whether knocking has occurred based on the vibration intensity. When the ECU 50 determines that knocking has occurred, the ECU 50 controls the ignition timing of the spark plug 13 to suppress the occurrence of knocking.

(Knock detection method)
The knocking detection method according to this embodiment will be specifically described. First, a general knocking detection method will be described for comparison. In a general knocking detection method, the ECU 50 calculates a characteristic value characterizing the vibration intensity of the vibration generated in the internal combustion engine 1 during a predetermined crank angle period based on the detection signal S6 from the knock sensor 6. The ECU 50 calculates the standard deviation and standard deviation of the frequency distribution of the feature value every time the feature value is calculated, and whether knocking has occurred based on the relationship between the calculated feature value, the median value, and the standard deviation. Determine whether or not. The details will be described below.

  First, the ECU 50 obtains the vibration intensity of the vibration generated in the internal combustion engine 1 based on the detection signal S6 from the knock sensor 6 in a predetermined crank angle period, and calculates the feature value based on the vibration intensity. In the present embodiment, the ECU 50 calculates the integral value V of the vibration intensity as a feature value.

  FIG. 2 is a schematic diagram showing a method for obtaining the integrated value V of the vibration intensity. FIG. 2A shows the change with respect to time of the detection signal S6 from the knock sensor 6. FIG. Specifically, the graph shown in FIG. 2A is obtained by extracting a specific frequency from the detection signal S6 from the knock sensor 6 through a filter circuit. In FIG. 2A, the time indicated on the horizontal axis is a time corresponding to a predetermined crank angle period. Since knocking occurs only between combustion pressures, the predetermined crank angle period is specifically set to a certain period after ignition output in order to prevent erroneous detection of knocking due to noise. This predetermined period is obtained in advance by experiments and recorded in the ECU 50.

  Next, the ECU 50 determines the vibration strength. Specifically, the output of the knock sensor 6 vibrates positively and negatively around 0, and thus the ECU 50 can obtain the vibration intensity by converting the detection signal S6 from the knock sensor 6 into an absolute value. FIG. 2B is a graph showing changes in vibration intensity with respect to time. Then, the ECU 50 integrates the vibration intensity over a time corresponding to a predetermined crank angle period, as shown in FIG. In this way, the integral value V of the vibration intensity of the internal combustion engine 1 is calculated.

  FIG. 3 is a graph showing the frequency distribution of the integrated value V of the vibration intensity as a normal distribution. Here, Vmed is the median value of the frequency distribution of the integral value V of vibration intensity, and SGM is the standard deviation of the frequency distribution of the integral value V of vibration intensity.

  The ECU 50 calculates the median value Vmed every time the integrated value V of the vibration intensity is calculated. Specifically, the ECU 50 obtains a new median value Vmed in the frequency distribution including the integrated value V of the vibration intensity calculated this time. For example, when the integral value V of the vibration intensity calculated this time is equal to or greater than the median value Vmed of the frequency distribution of the integral value V of the vibration intensity calculated so far, the ECU 50 determines the predetermined value as the median value Vmed. A value obtained by adding the value A is set as a new median value Vmed. On the other hand, when the integrated value V of the vibration intensity calculated this time is smaller than the median value Vmed of the frequency distribution of the integrated value V of the vibration intensity calculated so far, the ECU 50 determines the predetermined value from the median value Vmed. A value obtained by subtracting A is set as a new median value Vmed. That is, here, the ECU 50 performs the averaging process of the median value Vmed. This median value Vmed is the base vibration level for determining knocking. The predetermined value A is a conforming value, and a value corresponding to a change in the engine state is set.

  The ECU 50 calculates the standard deviation SGM every time the integral value V of the vibration intensity is calculated. Specifically, the ECU 50 obtains a new standard deviation SGM in the frequency distribution including the integrated value V of the vibration intensity calculated this time. For example, the ECU 50 determines that the integral value V of the vibration intensity calculated this time is Vmed−SGM ≦ V ≦ Vmed (SGM is a standard deviation of the frequency distribution of the integral value V of the vibration intensity calculated so far). When it is satisfied, SGM-2 × B is set as a new standard deviation SGM. On the other hand, when the integrated value V of the calculated vibration intensity does not satisfy the relationship of Vmed−SGM ≦ V ≦ Vmed, the ECU 50 sets SGM + B as a new standard deviation SGM. The predetermined value B is a conforming value, and a value corresponding to a change in the engine state is set.

  The ECU 50 determines that the relationship between the calculated integrated value V of the vibration intensity, the new median value Vmed, and the new standard deviation SGM is a relationship of V ≧ Vmed + U × SGM (hereinafter, this relationship is referred to as “knocking determination condition”). ) Is satisfied, it is determined that vibration due to knocking has occurred, and if the relationship of V ≧ Vmed + U × SGM is not satisfied, it is determined that vibration due to knocking has not occurred. Here, the predetermined value U is a conforming value, and a value corresponding to a change in the engine state is set. That is, as shown in FIG. 3, the ECU 50 determines that vibration due to knocking occurs when the calculated integrated value V of the vibration intensity is more than U × SGM from the median value Vmed. If not, it is determined that vibration due to knocking has not occurred. In this way, the ECU 50 can detect whether knocking has occurred.

  FIG. 4 is an example of a graph showing changes with respect to time of the integrated value V and the median value Vmed of the vibration intensity. In FIG. 4, the circle indicates the integrated value V of the vibration intensity, the solid triangle indicates the median value Vmed when the present invention is applied, and the broken triangle indicates that the present invention is not applied. The median value Vmed of V is shown.

  In the example shown in FIG. 4, it is assumed that one fuel injection is performed in one combustion until time t1. From time t1 to t2, it is assumed that multiple fuel injections, so-called multi-injection, are performed in one combustion. After the time t2, it is assumed that one fuel injection is performed once in one combustion. In the example shown in FIG. 4, it is assumed that vibration due to knocking does not occur and only stationary noise due to fuel injection occurs. Therefore, the integrated value V of the vibration intensity indicated by a circle is an integrated value of the vibration of stationary noise caused by fuel injection. In particular, in a direct injection type internal combustion engine that directly injects fuel into a combustion chamber, such as the internal combustion engine 1 of the present embodiment, steady noise tends to be relatively large.

  Until the time t1, the multi-injection execution flag is turned off (OFF), so multi-injection is not performed, and one fuel injection (hereinafter referred to as “single injection”) is performed in one combustion. That is, stationary noise mainly due to single injection occurs until time t1. At this time, as shown in FIG. 4, the integrated value V of the vibration intensity is a value that is hardly different from the median value Vmed.

  From time t1 to t2, the multi-injection execution flag is turned on (ON), and multi-injection is performed. Therefore, from time t1 to t2, the stationary noise is switched from single injection to multi-injection, and the magnitude of the vibration intensity is larger in one combustion than when single injection is performed. It becomes larger according to the number of injections. Therefore, the integrated value V of the vibration intensity from the time t1 to the time t2 is also larger than the integrated value V of the vibration intensity from the time t1 when the single injection is performed. At this time, when the above-described averaging process of the median value Vmed is performed, the median value Vmed does not immediately catch up with the vibration intensity V, but gradually integrates the vibration intensity, as indicated by a broken triangle. It approaches V and catches up with the integrated value V of the vibration intensity at time t1 + Δt1.

  Therefore, as shown in FIG. 4, the integrated value V of the vibration intensity from the time t1 to the time t1 + Δt1 is larger than the median value Vmed indicated by the broken triangle as compared with the integrated value V of the vibration intensity until the time t1. . Therefore, from time t1 to time t1 + Δt1, depending on the difference between the integrated value V of the vibration intensity and the median value Vmed, the integrated value V of the vibration intensity may satisfy the knocking determination condition. In this case, stationary noise due to multi-injection is determined to be knocking.

  Further, after time t2, the multi-injection execution flag is turned off (OFF), and single injection is performed. Therefore, after time t2, the stationary noise is switched from that due to multi-injection to that due to single injection, and the magnitude of the vibration intensity becomes smaller than that when multi-injection is performed. Therefore, the integrated value V of the vibration intensity after time t2 is smaller than the integrated value V of the vibration intensity from time t1 to time t2 when the multi-injection is performed. Also at this time, when the above-described averaging process of the median value Vmed is performed, the median value Vmed does not immediately catch up with the vibration intensity V, but gradually integrates the vibration intensity, as indicated by a broken triangle. The value approaches V and catches up with the integrated value V of the vibration intensity at time t2 + Δt2.

  Therefore, as shown in FIG. 4, the integrated value V of the vibration intensity from the time t2 to the time t2 + Δt2 is smaller than the median value Vmed as compared to the integrated value V of the vibration intensity from the time t1 to the time t2. Therefore, even if knocking occurs from time t2 to time t2 + Δt2, if the difference between the integrated value V of the vibration intensity due to knocking and the median value Vmed indicated by the broken triangle is not so large, the knocking determination condition is set. Not satisfying, knocking will not be detected.

  That is, when the vibration intensity changes stepwise due to switching of stationary noise, during the transition period indicated by Δt1 and Δt2, the ECU 50 performs the above-described averaging process of the median value Vmed, and the steady state immediately after the switching is performed. Since the error between the integrated value V and the median value Vmed of the vibration intensity due to noise increases, an accurate knock determination cannot be made.

  Therefore, in the knocking detection device according to the present embodiment, the ECU 50 determines whether or not the stationary noise generated in the internal combustion engine 1 has been switched. If it is determined that the stationary noise has been switched, the ECU 50 integrates the vibration intensity. The value V is the median value Vmed.

  By doing so, as indicated by solid triangles in FIG. 4, the median value Vmed at times t1 and t2 is made equal to the integral value V of the vibration intensity at times t1 and t2, respectively. As a result, as indicated by a solid triangle in FIG. 4, the error between the integral value V and the median value Vmed of the vibration intensity of the stationary noise is reduced in the transient period indicated by Δt1 and Δt2 immediately after the stationary noise is switched. The ECU 50 can make an accurate knock determination even when knocking occurs in the transition period after the stationary noise is switched. In the above example, the median value Vmed at the times t1 and t2 is set equal to the integral value V of the vibration intensity at the times t1 and t2, respectively. In addition to this, the predetermined ignition from the times t1 and t2 is performed. At the time of ignition, the median value Vmed may be made equal to the integrated value V of the vibration intensity at times t1 and t2. As the predetermined number of ignitions here, for example, the number of ignitions in a transition period indicated by Δt1 and Δt2 is set.

  Further, the knocking detection device according to the present embodiment does not exclude noise frequencies. Therefore, compared to a general knocking detection device that detects knocking by excluding the noise frequency, in the knocking detection device according to the present embodiment, even when the noise frequency matches the knocking frequency. The detectability of knocking can be improved. Further, in the knocking detection device according to the present embodiment, since the noise frequency is not excluded, it is possible to prevent the detection value of the knocking vibration intensity from changing as compared with a general knocking detection device that excludes the noise frequency. It is possible to prevent variations in the determination result.

  Needless to say, the above example is merely an example of the median Vmed averaging method and the standard deviation SGM calculation method, and other methods may be used.

(Knock detection process)
Next, the knocking detection process according to the present embodiment will be described with reference to the flowchart shown in FIG.

  First, in step S101, the ECU 50 calculates an integrated value V of vibration intensity in a predetermined crank angle period. Specifically, the ECU 50 obtains the vibration intensity of the vibration generated in the internal combustion engine 1 based on the detection signal S6 from the knock sensor 6 during a predetermined crank angle period, and integrates the vibration intensity based on the vibration intensity. The value V is calculated. The process described below is performed every time the integral value V of the vibration intensity is calculated.

  In step S102, the ECU 50 determines whether or not the stationary noise has been switched. For example, the ECU 50 determines that the stationary noise has been switched when switching between single injection and multi-injection or switching of the timing lift amount of the intake and exhaust valves. These switching operations are performed by the ECU 50 itself supplying control signals to the fuel injection valve 21 and the intake / exhaust valves. Therefore, the ECU 50 can detect that the stationary noise has been switched based on the control signal supplied to the fuel injection valve 21 and the intake / exhaust valve. For example, the ECU 50 turns on the multi-injection execution flag when supplying a control signal for causing the fuel injection valve 21 to execute multi-fuel injection. The ECU 50 can detect that the stationary noise has been switched to the one due to the multi-injection by detecting that the multi-injection execution flag is turned on.

  If the ECU 50 determines in step S102 that the stationary noise has been switched (step S102: Yes), the ECU 50 proceeds to step S103 and sets the integral value V of the vibration intensity calculated this time in step S101 as a new median value Vmed. . By doing so, the error between the integrated value V of the vibration intensity of the stationary noise immediately after switching of the stationary noise and the median value Vmed can be reduced, and knocking occurs in the transient period. Accurate knock determination can be performed. Thereafter, the ECU 50 advances the process to step S107.

  On the other hand, if the ECU 50 determines in step S102 that the stationary noise has not been switched (step S102: No), the ECU 50 proceeds to step S104, and the integral value V of the vibration intensity calculated this time has been calculated so far. It is determined whether or not the integrated value V of the vibration intensity is equal to or greater than the median value Vmed.

  If the ECU 50 determines in step S104 that the vibration intensity integral value V calculated this time is equal to or greater than the median value Vmed of the vibration intensity integral value V calculated so far (step S104: Yes). A value obtained by adding the predetermined value A to the median value Vmed of the integral value V of the vibration intensity calculated so far is set as a new median value Vmed (step S105). Thereafter, the ECU 50 advances the process to step S107. On the other hand, when the ECU 50 determines in step S104 that the integrated value V of the vibration intensity calculated this time is smaller than the median value Vmed of the integrated value V of the vibration intensity calculated so far (step S104). : Yes), a value obtained by subtracting the predetermined value A from the median value Vmed of the integrated value V of the vibration intensity calculated so far is set as a new median value Vmed (step S106). Thereafter, the ECU 50 advances the process to step S107. The predetermined value A is a conforming value, and a value corresponding to a change in the engine state is set in advance and recorded in the ECU 50. Through the processing in steps S104 to S106, the ECU 50 can perform the averaging process of the median value Vmed.

  Through the processing of steps S103 to S106 described above, the ECU 50 can obtain a new median value Vmed in the frequency distribution including the integrated value V of the vibration intensity calculated this time.

  In step S107, the ECU 50 determines that the integrated value V of the vibration intensity calculated this time is Vmed−SGM ≦ V ≦ Vmed (SGM is the standard deviation of the frequency distribution of the integrated value V of the vibration intensity calculated so far). It is determined whether or not the above is satisfied. If the ECU 50 determines in step S107 that the integral value V of the vibration intensity calculated this time satisfies the relationship of Vmed−SGM ≦ V ≦ Vmed (step S107: Yes), the SGM-2 × B is newly set. A standard deviation SGM is set (step S108). On the other hand, when the ECU 50 determines in step S107 that the integral value V of the vibration intensity calculated this time does not satisfy the relationship of Vmed−SGM ≦ V ≦ Vmed, SGM + B is set as a new standard deviation SGM ( Step S109). The predetermined value B is a conforming value, and a value corresponding to a change in the engine state is set in advance and recorded in the ECU 50. Through the processing in steps S107 to S109, the ECU 50 can obtain a new standard deviation SGM in the frequency distribution including the integrated value V of the vibration intensity calculated this time. The ECU 50 proceeds to step S110 after completing the process of step S108 or step S109.

  In step S110, the ECU 50 satisfies whether or not the integral value V of the vibration intensity calculated this time satisfies the knocking determination condition, that is, satisfies the relationship of V ≧ Vmed + U × SGM (hereinafter referred to as “knocking determination condition”). It is determined whether or not. When the ECU 50 determines in step S110 that the integrated value V of the vibration intensity calculated this time satisfies the knocking determination condition (step S110: Yes), the ECU 50 determines that vibration due to knocking has occurred (step S110). S111). On the other hand, if the ECU 50 determines in step S110 that the integral value V of the vibration intensity calculated this time does not satisfy the knocking determination condition (step S110: No), the ECU 50 determines that vibration due to knocking has not occurred. (Step S112). The predetermined value U is a conforming value, and a value corresponding to a change in the engine state is set in advance and recorded in the ECU 50. In this way, the ECU 50 can detect whether knocking has occurred.

  The feature value is not limited to the integral value V of the vibration intensity of the internal combustion engine 1. Instead, for example, a peak value that maximizes the vibration intensity as indicated by a point P1 in FIG. 2 may be used as the feature value.

  As can be understood from the above description, in the knocking detection device of the present invention, the ECU 50 is generated in the internal combustion engine 1 in the predetermined crank angle period based on the detection signal S6 from the knock sensor 6 in the predetermined crank angle period. The feature value that characterizes the vibration intensity of the measured vibration is calculated, and each time the feature value is calculated, the median of the frequency distribution of the feature value is calculated, and the standard deviation of the frequency distribution of the feature value is calculated, and the calculated feature It is determined whether knocking has occurred based on the relationship between the value, the median value, and the standard deviation. When calculating the median value, the ECU 50 determines whether or not the stationary noise generated in the internal combustion engine 1 has been switched. If the ECU 50 determines that the stationary noise has been switched, the median averaging process is performed. Instead of calculating a new median value, the calculated feature value is set as a new median value.

  According to the knocking detection device of the present invention, immediately after the stationary noise is switched, the error between the characteristic value and the median value of the stationary noise immediately after the switching can be reduced. Even so, an accurate knock determination can be made.

  Further, the knocking detection device of the present invention does not exclude noise frequencies. Therefore, compared with a general knocking detection device that detects knocking by excluding the noise frequency, the knocking detection device of the present invention does not knock even when the noise frequency matches the knocking frequency. The detectability can be improved, and variations in the determination result can be prevented.

It is a figure showing the schematic structure of the internal-combustion engine to which the knocking detection device of the present invention was applied. It is a schematic diagram which shows the method of calculating | requiring the integrated value of vibration intensity. It is the graph which showed frequency distribution of integral value V of vibration intensity as normal distribution. It is an example of the graph which shows the change with respect to time of the integral value and median value of vibration intensity. It is a flowchart which shows the knocking detection process which concerns on this embodiment.

Explanation of symbols

1 engine (internal combustion engine)
2 Cylinder block 2a Cylinder wall 3 Piston 4 Water jacket 6 Knock sensor 50 ECU

Claims (2)

A knocking detection device for detecting knocking generated in an internal combustion engine,
Vibration detecting means for detecting vibration generated in the internal combustion engine;
Feature value calculating means for calculating a characteristic value characterizing the vibration intensity of the vibration generated in the internal combustion engine in the predetermined crank angle period based on a detection signal from the detection device in the predetermined crank angle period;
Median value calculating means for calculating the median value of the frequency distribution of the feature value each time the feature value is calculated;
A standard deviation calculating means for calculating a standard deviation of a frequency distribution of the feature value each time the feature value is calculated;
Knocking determination means for determining whether or not knocking has occurred based on the relationship between the feature value calculated by the feature value calculation means, the median value, and the standard deviation;
A stationary noise switching determination means for determining whether or not the stationary noise generated in the internal combustion engine is switched,
The median value calculating means sets the feature value calculated by the feature value calculating means as the median value when the stationary noise switching determining means determines that the stationary noise has been switched. Knock detection device.   2. The knocking detection device according to claim 1, wherein the feature value calculation unit calculates an integral value of vibration intensity of vibration generated in the internal combustion engine in the predetermined crank angle period as the feature value.

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