JP2005351149A - Knocking detecting device and knocking detecting method of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a knocking detecting device and a knocking detecting method of an internal combustion engine capable of accurately detecting knocking in a low load. <P>SOLUTION: This internal combustion engine 1 generates motive power by burning an air-fuel mixture of fuel and air in a combustion chamber 3, and has a cylinder internal pressure sensor 15 for acquiring cylinder internal pressure in the combustion chamber 3, and an ECU 20. The ECU 20 calculates a change degree of heat generation rate when acquiring the cylinder internal pressure P(θ<SB>k</SB>) on the basis of the cylinder internal pressure P(θ<SB>k</SB>) acquired with every predetermined crank angle by using the cylinder internal pressure sensor 15, and determines the existence of knocking on the basis of the change degree of the heat generation rate. AD conversion performing time Tadr being the timing for acquiring the cylinder internal pressure P(θ<SB>k</SB>) for calculating the change degree of the heat generation rate, is changed by a predetermined angle with every combustion cycle. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a knocking detection device and a knocking detection method for an internal combustion engine that generates power by burning a fuel / air mixture in a combustion chamber.

  Conventionally, as an apparatus for preventing knocking of an internal combustion engine, an in-cylinder pressure detecting means for detecting an in-cylinder pressure in a combustion chamber, and a change state (degree of change) of a heat release rate based on a detection signal from the in-cylinder pressure detecting means. There has been known one provided with a calculation means for calculating the above and a storage means for storing a change state of a heat release rate in the internal combustion engine. In this device, paying attention to the fact that the heat generation rate in the cylinder rises temporarily and steeply due to the occurrence of knocking, the change state of the heat generation rate obtained by the calculation means and the heat generation rate stored in the storage means The combustion state of the internal combustion engine is determined by comparing with the change state of the engine, and combustion control is executed to avoid knocking.

Japanese Patent No. 2826591

  In the above-described conventional apparatus, the calculation accuracy of the change rate of the heat generation rate depends on the sampling period of the in-cylinder pressure. That is, if the sampling period of the in-cylinder pressure is long, the calculated change in the heat generation rate does not reflect the original temporary and steep state in spite of the fact that knocking has actually occurred. The difference with the change state of the generated heat generation rate becomes small, and knocking may not be detected even if the comparison process is performed. On the other hand, if the in-cylinder pressure sampling period is significantly shortened, knocking detection accuracy can be improved, but the calculation load becomes excessive, and a device for detecting knocking is used for, for example, a vehicle. It becomes practically difficult to apply to an internal combustion engine or the like.

  Therefore, an object of the present invention is to provide a knocking detection device and a knocking detection method for an internal combustion engine that can detect knocking with high accuracy and low load.

  The knock detection device for an internal combustion engine according to the present invention is a knock detection device for an internal combustion engine that generates power by burning a mixture of fuel and air in a combustion chamber, and detects the in-cylinder pressure in the combustion chamber. Means, calculating means for calculating the degree of change in heat release rate based on the in-cylinder pressure acquired for each predetermined crank angle using the in-cylinder pressure detecting means, and the degree of change in heat release rate calculated by the calculating means. It is characterized by comprising determination means for determining the presence or absence of knocking based on, and means for changing the timing for acquiring the in-cylinder pressure for each combustion cycle.

  The internal combustion engine preferably includes a plurality of combustion chambers, and the timing for acquiring the in-cylinder pressure is preferably changed between the plurality of combustion chambers.

  Furthermore, it is preferable that the amount of change in the timing for acquiring the in-cylinder pressure is shorter than the assumed knocking occurrence period.

  The computing means is based on a control parameter that is the product of the in-cylinder pressure acquired using the in-cylinder pressure detecting means and a value obtained by raising the in-cylinder volume at the time of acquisition of the in-cylinder pressure by a predetermined exponent. It is preferable to calculate the degree of change in the heat release rate.

  The knock detection method for an internal combustion engine according to the present invention is a knock detection method for an internal combustion engine that generates power by burning a mixture of fuel and air in a combustion chamber. (B) calculating the degree of change in the heat generation rate based on the in-cylinder pressure acquired in step (a), and (c) the heat generation rate calculated in step (b). And determining the presence or absence of knocking based on this, and changing the timing for acquiring the in-cylinder pressure for each combustion cycle.

  Further, the internal combustion engine includes a plurality of combustion chambers, and it is preferable to change the timing for acquiring the in-cylinder pressure between the plurality of combustion chambers. Furthermore, it is preferable that the amount of change in the timing for acquiring the in-cylinder pressure be shorter than the expected knocking occurrence period. In step (b), the degree of change in the heat release rate is calculated based on a control parameter that is the product of the in-cylinder pressure and the value obtained by raising the in-cylinder volume at the time of acquisition of the in-cylinder pressure by a predetermined index. It is preferable.

  According to the present invention, it is possible to realize a knocking detection device and a knocking detection method for an internal combustion engine that can detect knocking accurately with low load.

  The inventor calculates the degree of change in the heat release rate based on the acquired in-cylinder pressure based on the in-cylinder pressure acquired for each predetermined crank angle using the in-cylinder pressure detecting means, and calculates the calculated heat generation. When determining the presence or absence of knocking based on the rate of change in rate, we conducted intensive research to reduce the computational load and improve the detection accuracy of knocking. As a result of research, the present inventor came to pay attention to the timing for acquiring (sampling) the in-cylinder pressure.

  That is, when the in-cylinder pressure is acquired at every predetermined crank angle (for example, 6 °) and the degree of change in the heat release rate is calculated based on the acquired in-cylinder pressure, as shown in FIG. 1 and the timing at which knocking occurs in the combustion chamber are in good agreement, the degree of change in the heat generation rate at a predetermined timing calculated based on the in-cylinder pressure (the two shown by the solid line in FIG. 1). Since the change in the heat generation rate when knocking has not occurred (refer to the inclination between two measurement points indicated by a one-dot chain line in FIG. 1), It is possible to determine the presence or absence of knocking using the degree of change in the heat generation rate.

  On the other hand, as shown in FIG. 2, when the timing at which the in-cylinder pressure is acquired does not match well with the timing at which knocking occurs in the combustion chamber, at a predetermined timing calculated based on the in-cylinder pressure. The degree of change in the heat generation rate (see the slope between two measurement points indicated by the solid line in FIG. 2) is the degree of change in the heat generation rate when knocking has not occurred (the two changes indicated by the one-dot chain line in FIG. 2). In this case, it is difficult to determine the presence or absence of knocking using the degree of change in the heat generation rate.

  In consideration of these points, in the present invention, the timing for acquiring the in-cylinder pressure for calculating the degree of change in the heat release rate is changed for each combustion cycle. As a result, even if the predetermined crank angle, i.e., the in-cylinder pressure sampling period, is not shortened more than necessary, the timing at which the in-cylinder pressure is acquired and the timing at which knocking occurs in the combustion chamber are well matched. Can be increased. Therefore, according to the present invention, it is possible to detect knocking of the internal combustion engine with low load and high accuracy.

  Moreover, it is preferable that the timing for acquiring the in-cylinder pressure for calculating the degree of change in the heat generation rate is changed between the plurality of combustion chambers. As a result, with respect to a certain combustion chamber, even if the timing for acquiring the in-cylinder pressure does not match the timing at which knocking occurs in the combustion chamber, both timings can be matched well in the other combustion chambers. . Therefore, according to such a configuration, it is possible to further increase the probability that the timing at which the in-cylinder pressure is acquired and the timing at which knocking occurs in the combustion chamber match well, thereby improving the knocking detection accuracy. Furthermore, the amount of change in the timing at which the in-cylinder pressure is acquired for calculating the degree of change in the heat generation rate may be made shorter than the expected knocking generation period. As a result, it is possible to further increase the probability that the timing at which the in-cylinder pressure is acquired and the timing at which knocking occurs in the combustion chamber match well.

On the other hand, the present inventor conducted further research to calculate the heat generation rate and the degree of change thereof at a low load, and in the process, the in-cylinder pressure acquired using the in-cylinder pressure detecting means, and the in-cylinder pressure The control parameters calculated based on the in-cylinder volume at the time of pressure acquisition were noted. More specifically, the present inventor sets P (θ) as the in-cylinder pressure acquired using the in-cylinder pressure detection means when the crank angle is θ, and the in-cylinder volume when the crank angle is θ. When V (θ) and the specific heat ratio are κ, the in-cylinder pressure P (θ) and the value V ^κ (θ) obtained by raising the in-cylinder volume V (θ) to a specific heat ratio (predetermined index) κ The control parameter P (θ) · V ^κ (θ) (hereinafter referred to as “PV ^κ ” as appropriate) obtained as the product of Then, the present inventor has a correlation between the change pattern of the heat generation amount Q in the cylinder of the internal combustion engine with respect to the crank angle and the change pattern of the control parameter PV ^κ with respect to the crank angle as shown in FIG. I found out. In FIG. 3, −360 °, 0 °, and 360 ° correspond to the top dead center, and −180 ° and 180 ° correspond to the bottom dead center.

In FIG. 3, the solid line shows the in-cylinder pressure acquired for each predetermined minute crank angle in a predetermined model cylinder, and the value obtained by raising the in-cylinder volume at the time of acquisition of the in-cylinder pressure by a predetermined specific heat ratio κ. This is a plot of the control parameter PV ^κ which is the product. In FIG. 3, the broken line is calculated and plotted with the heat generation amount Q in the model cylinder as Q = ∫dQ based on the following equation (1) indicating the heat generation rate. In either case, for simplicity, κ = 1.32.

As can be seen from the results shown in FIG. 3, the change pattern of the heat generation amount Q with respect to the crank angle and the change pattern of the control parameter PV ^κ with respect to the crank angle are substantially the same (similar), and in particular, Before and after the start of combustion of the air-fuel mixture (at the time of spark ignition or compression ignition) (for example, a range from about −180 ° to about 135 ° in FIG. 3), the change pattern of the heat generation amount Q and the control parameter PV ^κ It can be seen that the change pattern matches very well.

In the present invention, using the correlation between the heat generation amount Q and the control parameter PV ^κ , the in-cylinder pressure acquired using the in-cylinder pressure detecting means, the in-cylinder volume at the time of acquiring the in-cylinder pressure, and based on the control parameter PV ^kappa calculated from the heat generation rate dQ / d [theta] (hereinafter, to indicate that calculated using the control parameter PV ^kappa, appropriately referred to as "d (PV ^kappa)") is obtained. That is, if the control parameter PV ^κ is used, the heat generation rate at an arbitrary timing (timing at which the crank angle = θ) is obtained as a difference between the control parameters PV ^κ between two predetermined points (between the minute crank angles δ), that is, ,

  Represented as:

Here, in FIG. 4, the solid line represents the heat generation rate d (PV ^κ ) at the timing when the crank angle = θ in the model cylinder described above, calculated based on the control parameter PV ^κ and plotted. However, for simplicity, κ = 1.32 and δ = 1 ° (1 CA). In FIG. 4, the broken line calculates the heat generation rate dQ / dθ at the timing when the crank angle = θ in the model cylinder described above, based on the above equation (1) and based on the in-cylinder pressure P (θ), It is a plot. Also in this case, for simplicity, κ = 1.32. As can be seen from FIG. 4, the change pattern of d (PV ^κ ) with respect to the crank angle (see the solid line in FIG. 4) is a change pattern of the heat release rate dQ / dθ obtained based on the equation (1) (see FIG. 4). It almost coincides (similar) with the broken line in the figure. Therefore, if the control parameter PV ^κ is used, the heat generation rate and the degree of change in the combustion chamber can be accurately obtained without requiring high-load calculation processing. Note that the heat generation rate dQ / dθ [d (PV ^κ )] at the timing when the crank angle = θ is obtained by using the conversion coefficient α for converting the heat generation amount Q into the energy change rate.

  May be represented as

  Hereinafter, the best mode for carrying out the present invention will be specifically described with reference to the drawings.

  FIG. 5 is a schematic configuration diagram showing an internal combustion engine to which the knocking detection device according to the present invention is applied. The internal combustion engine 1 shown in FIG. 1 generates power by burning a fuel / air mixture in a combustion chamber 3 formed in a cylinder block 2 and reciprocating a piston 4 in the combustion chamber 3. Is. Although only one cylinder is shown in FIG. 5, the internal combustion engine 1 is preferably configured as a multi-cylinder engine, and the internal combustion engine 1 of the present embodiment is configured as a four-cylinder engine.

  The intake port of each combustion chamber 3 is connected to the intake pipe 5 via an intake manifold, and the exhaust port of each combustion chamber 3 is connected to the exhaust pipe 6 via an exhaust manifold. In addition, an intake valve Vi that opens and closes an intake port and an exhaust valve Ve that opens and closes an exhaust port are provided for each combustion chamber 3 in the cylinder head of the internal combustion engine 1. Each intake valve Vi and each exhaust valve Ve are opened and closed by a valve operating mechanism (not shown) having a variable valve timing function. Further, the internal combustion engine 1 has a number of spark plugs 7 corresponding to the number of cylinders, and the spark plugs 7 are disposed in the cylinder heads so as to face the corresponding combustion chambers 3.

  The intake pipe 5 is connected to a surge tank 8 as shown in FIG. An air supply pipe L1 is connected to the surge tank 8, and the air supply pipe L1 is connected to an air intake port (not shown) via an air cleaner 9. A throttle valve (electronically controlled throttle valve in this embodiment) 10 is incorporated in the middle of the supply pipe L1 (between the surge tank 8 and the air cleaner 9). On the other hand, as shown in FIG. 5, a front-stage catalyst device 11 a including a three-way catalyst and a rear-stage catalyst device 11 b including a NOx storage reduction catalyst are connected to the exhaust pipe 6.

  Further, as shown in FIG. 5, the internal combustion engine 1 has a plurality of injectors 12, and the injectors 12 are disposed in the cylinder heads so as to face the corresponding combustion chambers 3. Each piston 4 of the internal combustion engine 1 is configured as a so-called deep dish top surface type, and a recess 4a is formed on the upper surface thereof. In the internal combustion engine 1, fuel such as gasoline is directly injected from each injector 12 toward the recess 4 a of the piston 4 in each combustion chamber 3 in a state where air is sucked into each combustion chamber 3. As a result, in the internal combustion engine 1, the fuel / air mixture layer is formed (stratified) in the vicinity of the spark plug 7 so as to be separated from the surrounding air layer. And stable stratified combustion can be performed. The internal combustion engine 1 of the present embodiment is described as a so-called direct injection engine, but is not limited to this, and the present invention can be applied to an intake pipe (intake port) injection type internal combustion engine. Not too long. Needless to say, the present invention can be applied to a diesel engine.

  Each of the spark plugs 7, the throttle valve 10, the injectors 12, the valve operating mechanism and the like described above are electrically connected to an ECU 20 that functions as a control device for the internal combustion engine 1. The ECU 20 includes a CPU, a ROM, a RAM, an input / output port, a storage device, etc., all not shown. Various sensors such as an air flow meter AFM for detecting the intake air amount are electrically connected to the ECU 20 via an A / D converter or the like. The ECU 20 uses the various maps stored in the storage device and the spark plug 7, the throttle valve 10, the injector 12, the valve operating mechanism, etc. so as to obtain a desired output based on the detection values of various sensors. To control.

  As shown in FIG. 5, the sensors connected to the ECU 20 include a crank angle sensor 14. The crank angle sensor 14 is a magnetic sensor or a photoelectric sensor including a rotor plate (signal plate) fixed to the crankshaft, and the like, and provides a pulse signal indicating the rotation angle of the crankshaft to the ECU 20 every minute time. Further, the internal combustion engine 1 has in-cylinder pressure sensors (in-cylinder pressure detecting means) 15 including a semiconductor element, a piezoelectric element, an optical fiber detection element, or the like, corresponding to the number of cylinders. Each in-cylinder pressure sensor 15 is disposed on the cylinder head so that the pressure receiving surface faces the corresponding combustion chamber 3, and is electrically connected to the ECU 20 via the A / D converter 16. Each in-cylinder pressure sensor 15 outputs a voltage signal (a signal indicating a detection value) corresponding to the pressure (in-cylinder pressure) applied to the pressure receiving surface in the combustion chamber 3. In the present invention, the in-cylinder pressure sensor 15, the ECU 20, and the like constitute a knocking detection device that detects knocking in the combustion chamber 3 of the internal combustion engine 1.

  Next, a procedure for detecting knocking in each combustion chamber 3 of the internal combustion engine 1 will be described with reference to FIGS.

  When the internal combustion engine 1 is started, the ECU 20 reads the AD conversion execution interval Tad (in this embodiment, for example, 6 °) and the timing change rate Nr, which are parameters for detecting knocking, and sets the timing setting flag. Set to the initial value (in this case “0”). In consideration of practicality, the AD conversion execution interval Tad is set to 6 ° in the present embodiment, for example. Further, the timing change rate Nr is determined so as to satisfy Tn ≧ Tad / Nr when an assumed knocking occurrence period Tn, and is set to “2” in the present embodiment, for example. Then, as shown in FIG. 6, the ECU 20 determines the combustion chamber 3 in which the knock determination period has arrived based on the signal from the crank angle sensor 14 (S10).

  In the present embodiment, the knock determination period is generally determined between the compression top dead center and the expansion bottom dead center for each combustion chamber 3. That is, the knock determination period of the first combustion chamber 3 (hereinafter referred to as “first cylinder # 1”) is set to a range in which the crank angle is approximately 0 ° to 180 °. The knock determination period of “No. 3 cylinder # 3” is in a range where the crank angle is approximately 180 ° to 360 °. Further, the knock determination period of the fourth combustion chamber 3 (hereinafter referred to as “fourth cylinder # 4”) is set to a range in which the crank angle is approximately 360 ° to 540 °, and the second combustion chamber 3 (hereinafter referred to as “fourth cylinder # 4”). The knock determination period of “No. 2 cylinder # 2” is in a range where the crank angle is approximately 540 ° to 720 °.

  When the ECU 20 determines in S12 that the first cylinder # 1 is in the knock determination period based on the signal from the crank angle sensor 14, the ECU 20 further determines in the first cylinder # 1 based on the signal from the crank angle sensor 14. It is determined whether or not the piston 4 is at the compression top dead center (whether or not the crank angle is 0 °) (S14). When determining that the piston 4 is at the compression top dead center in the first cylinder # 1, the ECU 20 reverses the timing setting flag from the previous value (S16). That is, the ECU 20 sets the timing setting flag from “0” to “1” immediately after the internal combustion engine 1 is started, and sets the timing setting flag to “0” when the timing setting flag is “1”.

  When the process of S16 is executed, the ECU 20 determines whether or not the timing setting flag is “1” (S18). When the ECU 20 determines that the timing setting flag is “1” in S18, the AD conversion start time Tadst is set to “0 °”, and the AD conversion execution time Tadr is set as Tadr = Tadst = 0 °. (S20). On the other hand, when determining in S18 that the timing setting flag is not “1” but “0”, the ECU 20 sets the AD conversion start timing Tadst to Tadst = (Tad / Nr) ° (3 ° in the present embodiment). ) And AD conversion execution time Tadr is set as Tadr = Tadst = 3 ° (S22).

Thereafter, the ECU 20 performs AD conversion processing on the signal from the in-cylinder pressure sensor 15 of the first cylinder # 1 to the AD converter 16 for the first cylinder # 1 according to the AD conversion execution timing Tadr set in S20 or S22. (S24), and the AD conversion execution timing Tadr (Crank angle at this time is θ _k , where k is an integer equal to or greater than 1) obtained thereby Based on the pressure value P (θ _k ), a knock determination routine (S26) is executed.

FIG. 8 is a flowchart for explaining the knock determination routine. As shown in the figure, when the knock determination, ECU 20, first, the value of the first cylinder # 1 of the in-cylinder pressure in the AD conversion execution timing Tadr (when the crank angle becomes θ _k) P (θ _k) (S260), and using the above equation (3), the heat generation rate dQ / ds (θ _k ) at the AD conversion execution time Tadr is expressed as dQ / ds (θ _k ) = α · P (θ _k ) · V ^κ (θ _k ) (S261). In this way, by using the control parameter PV ^κ described above, it is possible to accurately grasp the heat generation rate dQ / ds (θ _k ) and the degree of change thereof without requiring high-load calculation processing.

Then, the ECU 20 takes the deviation between the heat generation rate dQ / ds (θ _k ) calculated in S261 and the heat generation rate dQ / ds (θ _k-1 ) calculated in the previous time, so that the previous and current AD conversions are performed. The degree of change in heat generation rate between execution times Tadr is calculated, and the degree of change in heat generation rate {dQ / ds (θ _k ) −dQ / ds (θ _k−1 )} is below a predetermined threshold value β. It is determined whether or not (S262). However, when k = 1, dQ / ds (θ _k−1 ) = 0. The threshold value β is a value determined based on the degree of change in the heat generation rate when knocking has not occurred, and is set to, for example, -0.03.

In S262, it is determined that the degree of change in heat release rate {dQ / ds (θ _k ) −dQ / ds (θ _k−1 )} is lower than the threshold value β. It shows that the fluctuation of the heat generation rate in the vicinity (at the time of obtaining the in-cylinder pressure P (θ _k )) is steep and deviates from the allowable range. Therefore, when the ECU 20 makes an affirmative determination in S262, it determines that knocking has occurred in the first cylinder # 1 (S263). On the other hand, when it is determined that the degree of change {dQ / ds (θ _k ) −dQ / ds (θ _k−1 )} is not lower than the threshold value β, the heat generation rate in the vicinity of the AD conversion execution timing Tadr is determined. The variation will be within an acceptable range. Therefore, if the ECU 20 makes a negative determination in S262, it determines that knocking has not occurred in the first cylinder # 1 (S264). After the determination in S263 or S264, the ECU 20 replaces the previous heat generation rate dQ / ds (θ _k-1 ) with the heat generation rate dQ / ds (θ _k ) calculated in S261 (S265), and then makes a knock determination. The routine is temporarily terminated.

  As shown in FIG. 6, after the execution of the knock determination routine (S26), the ECU 20 sets the AD conversion execution time Tadr as Tadr = Tadr + Tad (S28), and executes the processes after S10 again. At this time, even if the first cylinder # 1 is in the knock determination period, if it is not determined in S14 that the piston 4 is at the compression top dead center, the processing from S16 to S22 is skipped. Therefore, as described above, when the process of S20 is executed once, for the first cylinder # 1, the AD conversion process is performed every 6 ° from the time when the crank angle becomes 0 ° to the time when it becomes 180 ° (S24). And a knock determination routine (S26) is executed. When the process of S22 is executed once, for the first cylinder # 1, the AD conversion process (S24) and the knock determination routine (S24) are performed every 6 ° from the time when the crank angle becomes 3 ° to the time when it reaches 177 °. S26) is executed.

  When the knock determination for the first cylinder # 1 ends, in this embodiment, the knock determination period for the third cylinder # 3 comes. When the ECU 20 determines in S30 that the third cylinder # 3 is in the knock determination period based on the signal from the crank angle sensor 14, the ECU 20 further determines in the third cylinder # 3 based on the signal from the crank angle sensor 14. It is determined whether or not the piston 4 is at the compression top dead center (whether or not the crank angle is 180 °) (S32).

  When it is determined that the piston 4 is at the compression top dead center in the third cylinder # 3 (S32), the ECU 20 determines whether or not the timing setting flag is “1” (S34). When the ECU 20 determines that the timing setting flag is “1” in S34, the AD conversion start timing Tadst is set to Tadst = (180 + Tad / Nr) ° (183 ° in this embodiment), and then AD conversion is performed. The execution time Tadr is set as Tadr = Tadst = 183 ° (S36). On the other hand, if it is determined in S34 that the timing setting flag is not “1” but “0”, the ECU 20 sets the AD conversion start timing Tadr to Tadr after setting the AD conversion start timing Tadst to “180 °”. = Tadst = 180 ° is set (S38).

Thereafter, the ECU 20 performs AD conversion processing on the signal from the in-cylinder pressure sensor 15 of the third cylinder # 3 to the AD converter 16 for the third cylinder # 3 according to the AD conversion execution timing Tadr set in S36 or S38. It was executed (S40), (a crank angle and theta _k at this time. However k is 1 or more is an integer.) AD conversion execution timing Tadr obtained thereby in the third cylinder # 3 in the cylinder Based on the pressure value P (θ _k ), a knock determination routine (S42) is executed. The knock determination routine of S42 is the same as the routine of S26 shown in FIG.

  After executing the knock determination routine (S42) of S42, the ECU 20 sets the AD conversion execution time Tadr as Tadr = Tadr + Tad (S44), and executes the processes after S30 again. At this time, even if the third cylinder # 3 is in the knock determination period, if it is not determined in S32 that the piston 4 is at the compression top dead center, the processing from S34 to S38 is skipped. Therefore, as described above, when the process of S36 is executed once, for the third cylinder # 3, the AD conversion process is performed every 6 ° from the time when the crank angle becomes 183 ° to the time when it becomes 357 ° (S40). Then, the knock determination routine (S42) is executed. When the process of S38 is executed once, for the third cylinder # 3, the AD conversion process (S40) and the knock determination routine (S40) are performed every 6 ° from the time when the crank angle becomes 180 ° to the time when it becomes 360 °. S42) is executed.

  When the knock determination for the third cylinder # 3 ends, in this embodiment, the knock determination period for the fourth cylinder # 4 comes. For the fourth cylinder # 4, the processing of S46, S48, S50, S52, S54, S56, S58, and S60 (corresponding to S30, S32, S34, S36, S38, S40, S42, and S44 in order) ( (See FIG. 7). In this case, when the ECU 20 determines that the timing setting flag is “1” in S50, the AD conversion start time Tadst is set to “360 °”, and the AD conversion execution time Tadr is set to Tadr = Tadst = 360 °. (S52). On the other hand, when determining in S50 that the timing setting flag is not “1” but “0”, the ECU 20 sets the AD conversion start timing Tadst to Tadst = (360 + Tad / Nr) ° (363 ° in the present embodiment). ) And AD conversion execution time Tadr is set as Tadr = Tadst = 363 ° (S54).

  Thereby, when the process of S52 is executed once, for the fourth cylinder # 4, the AD conversion process (S56) and the knock determination are performed every 6 ° from the time when the crank angle becomes 360 ° to the time when it becomes 540 °. The routine (S58) is executed. When the process of S54 is executed once, for the fourth cylinder # 4, the AD conversion process (S56) and the knock determination routine are performed every 6 ° from the time when the crank angle becomes 363 ° to the time when it becomes 537 °. (S58) is executed.

  When the knock determination for the fourth cylinder # 4 is completed, in this embodiment, the knock determination period for the second cylinder # 2 comes. Also for the second cylinder # 2, the processing of S62, S64, S66, S68, S70, S72, and S74 corresponding to the above-described S32, S34, S36, S38, S40, S42, and S44 in order (see FIG. 7) is executed. Is done. In this case, when the ECU 20 determines that the timing setting flag is “1” in S64, the AD conversion start timing Tadst is set to Tadst = (540 + Tad / Nr) ° (543 ° in the present embodiment). The AD conversion execution time Tadr is set as Tadr = Tadst = 543 ° (S66). On the other hand, if it is determined in S64 that the timing setting flag is not “1” but “0”, the ECU 20 sets the AD conversion start time Tadr to “540 °” and sets the AD conversion execution time Tadr to Tadr. = Tadst = 540 ° (S68).

  Thus, when the process of S66 is executed once, for the second cylinder # 2, the AD conversion process (S70) and the knock determination routine are performed every 6 ° from the time when the crank angle becomes 543 ° to the time when it becomes 717 °. (S72) is executed. When the process of S68 is executed once, for the fourth cylinder # 4, the AD conversion process (S70) and the knock determination routine (S70) are performed every 6 ° from the time when the crank angle becomes 540 ° to the time when it becomes 720 °. S72) is executed. When the knock determination for the fourth cylinder # 4 ends, in this embodiment, the knock determination period for the first cylinder # 1 comes again, and thereafter, the above-described first cylinder # 1, the third cylinder # described above. The knocking determination for the third cylinder, the fourth cylinder # 4, and the second cylinder # 2 is repeatedly executed.

  After the knock determination for the fourth cylinder # 4 is completed, when the knock determination period for the first cylinder # 1 comes again and the piston 4 reaches the compression top dead center in the first cylinder # 1, S16. The timing setting flag is inverted at. In the first cylinder # 1 of the internal combustion engine 1, every time the timing setting flag is inverted, the AD conversion start timing Tadst is changed between 0 ° and Tad / Nr = 3 °. The AD conversion execution time Tadr set in S28 also changes.

  Similarly, in the third cylinder # 3, every time the timing setting flag is inverted, the AD conversion start timing Tadst is changed between 183 ° and 180 °, and accordingly, the AD conversion set in S44. The execution time Tadr also changes. In the fourth cylinder # 4, every time the timing setting flag is reversed, the AD conversion start timing Tadst is changed between 360 ° and 3630 °, and accordingly, AD conversion execution set in S60 is performed. Time Tadr also changes. Further, in the second cylinder # 2, every time the timing setting flag is inverted, the AD conversion start timing Tadst is changed between 543 ° and 540 °, and accordingly, AD conversion execution set in S74 is performed. Time Tadr also changes.

Here, the timing setting flag is inverted in S16 because the first cylinder # 1 is in the knock determination period and the piston 4 reaches the compression top dead center in the first cylinder # 1. In one combustion cycle, the timing setting flag is inverted only once. That is, in the internal combustion engine 1, the AD conversion execution timing Tadr, which is the timing for acquiring the in-cylinder pressure for calculating the degree of change in the heat generation rate dQ / ds (θ _k ), is Tad / Nr = 3 ° for each combustion cycle. Can only be changed (shifted). Thus, the timing (AD conversion execution timing Tadr) for acquiring the in-cylinder pressure P (θ _k ) and the combustion chamber 3 can be obtained without shortening the AD conversion execution interval Tad, which is the sampling period of the in-cylinder pressure, more than necessary. It is possible to increase the probability that the timing at which knocking occurs is well matched. Therefore, according to the present invention, knocking of the internal combustion engine 1 can be detected accurately with a low load in the knock determination routine of S26, S42, S58, and S72.

  As described above, when the timing setting flag is “1”, for the first cylinder # 1, from the time when the crank angle becomes 0 ° to 180 °, for the third cylinder # 3, From the time when the crank angle becomes 183 ° to the time when it becomes 357 °, for the fourth cylinder # 4, from the time when the crank angle becomes 360 ° to the time when it becomes 540 °, the crank angle for the second cylinder # 2 The AD conversion process and the knock determination routine are executed every 6 ° from the time when becomes 543 ° to the time when it becomes 717 °.

  On the other hand, when the timing setting flag is “0”, for the first cylinder # 1, the crank angle is 180 ° for the third cylinder # 3 from the time when the crank angle is 3 ° to the time when it becomes 177 °. From the time when the crank angle becomes 360 °, the crank angle for the fourth cylinder # 4 becomes 540 ° for the second cylinder # 2 from the time when the crank angle becomes 363 ° until the time when the crank angle becomes 537 °. The AD conversion process and the knock determination routine are executed every 6 ° from the time to 720 °.

That is, the in-cylinder pressure P (θ _k ) is acquired between the first cylinder # 1 and the third cylinder # 3 of the internal combustion engine 1 in order to calculate the degree of change in the heat generation rate dQ / ds (θ _k ). The AD conversion execution timing Tadr, which is the timing to perform, is changed (shifted) by Tad / Nr = 3 ° with the compression top dead center as a reference. Similarly, the in-cylinder pressure P (θ _k ) is also calculated between the fourth cylinder # 4 and the second cylinder # 2 of the internal combustion engine 1 in order to calculate the degree of change in the heat generation rate dQ / ds (θ _k ). The AD conversion execution timing Tadr, which is the acquisition timing, is changed (shifted) by 3 ° with reference to the compression top dead center.

Accordingly, with respect to one combustion chamber 3 (for example, the first cylinder # 1), the timing (AD conversion execution timing Tadr) for acquiring the in-cylinder pressure P (θ _k ) and the timing at which knocking occurs in the combustion chamber 3 Even if these do not match, both timings can be matched well in the other combustion chamber 3 (for example, the third cylinder # 3). Therefore, in the internal combustion engine 1, the probability that the timing (AD conversion execution timing Tadr) at which the in-cylinder pressure P (θ _k ) is acquired and the timing at which knocking occurs in the combustion chamber 3 matches well is further increased. The knocking detection accuracy can be improved.

Then, heat is generated for each combustion cycle and between the combustion chambers 3 (between the first cylinder # 1 and the third cylinder # 3 and between the fourth cylinder # 4 and the second cylinder # 2). Amount (AD / Nr = 3 in the present embodiment) of changing the timing (AD conversion execution timing Tadr) for acquiring the in-cylinder pressure P (θ _k ) in order to calculate the rate of change of the rate dQ / ds (θ _k ). Is preferably shorter than the expected knocking occurrence period (for example, 5 °). Thereby, it is possible to further increase the probability that the timing at which the in-cylinder pressure P (θ _k ) is acquired and the timing at which knocking occurs in the combustion chamber 3 are well matched.

It is a graph for demonstrating the state in which the timing which acquires in-cylinder pressure, and the timing which knocking generate | occur | produces in a combustion chamber matched well. It is a graph for demonstrating the state where the timing which acquires in-cylinder pressure, and the timing which knocking generate | occur | produce in a combustion chamber do not correspond. It is a graph which shows the correlation between control parameter PV ( ^kappa) used in this invention, and the amount of heat generation in a combustion chamber. It is a graph which shows the correlation with the heat release rate calculated ^| required based on control parameter PV ( ^kappa) , and the heat release rate calculated | required according to a theoretical formula. 1 is a schematic configuration diagram showing an internal combustion engine according to the present invention. 6 is a flowchart for explaining a knocking detection procedure in the internal combustion engine of FIG. 5. 6 is a flowchart for explaining a knocking detection procedure in the internal combustion engine of FIG. 5. It is a flowchart for demonstrating the knock determination routine shown by FIG. 6 and FIG.

Explanation of symbols

1 Internal combustion engine 3 Combustion chamber 4 Piston 7 Spark plug 12 Injector 14 Crank angle sensor 15 In-cylinder pressure sensor 20 ECU
Ve Exhaust valve Vi Intake valve

Claims (8)

In a knocking detection device for an internal combustion engine that generates power by burning a mixture of fuel and air in a combustion chamber,
In-cylinder pressure detecting means for acquiring the in-cylinder pressure in the combustion chamber;
Calculation means for calculating the degree of change in the heat release rate based on the in-cylinder pressure obtained for each predetermined crank angle using the in-cylinder pressure detection means;
Determining means for determining the presence or absence of knocking based on the degree of change in the heat generation rate calculated by the calculating means;
And a means for changing the timing for obtaining the in-cylinder pressure for each combustion cycle.   2. The knock detection device for an internal combustion engine according to claim 1, wherein the internal combustion engine includes a plurality of the combustion chambers, and a timing at which the in-cylinder pressure is acquired is changed between the plurality of combustion chambers.   3. The knock detection device for an internal combustion engine according to claim 1, wherein an amount of change in timing for acquiring the in-cylinder pressure is shorter than an assumed knock generation period. 4.   The computing means is based on a control parameter that is the product of the in-cylinder pressure acquired using the in-cylinder pressure detecting means and a value obtained by raising the in-cylinder volume at the time of acquisition of the in-cylinder pressure by a predetermined exponent. The knock detection device for an internal combustion engine according to any one of claims 1 to 3, wherein the degree of change in the heat generation rate is calculated. In a knocking detection method for an internal combustion engine that generates power by burning a mixture of fuel and air in a combustion chamber,
(A) obtaining in-cylinder pressure in the combustion chamber for each predetermined crank angle;
(B) calculating the degree of change in the heat release rate based on the in-cylinder pressure acquired in step (a);
(C) determining the presence or absence of knocking based on the degree of change in the heat release rate calculated in step (b),
A method for detecting knocking of an internal combustion engine, wherein timing for acquiring the in-cylinder pressure is changed for each combustion cycle.   6. The knock detection method for an internal combustion engine according to claim 5, wherein the internal combustion engine includes a plurality of the combustion chambers, and the timing for acquiring the in-cylinder pressure is changed between the plurality of combustion chambers.   7. The knock detection method for an internal combustion engine according to claim 5, wherein an amount of change in timing for acquiring the in-cylinder pressure is made shorter than an assumed knock generation period. In step (b), the degree of change in the heat release rate is calculated based on a control parameter that is the product of the in-cylinder pressure and a value obtained by raising the in-cylinder volume at the time of acquisition of the in-cylinder pressure by a predetermined index. The knock detection method for an internal combustion engine according to any one of claims 5 to 7.

Images