JP2008309062A - Knocking detection device for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve accuracy of knocking detection in a knocking detection device for an engine provided with ignition circuits provided for a main spark plug 7a and a sub spark plug 7b provided facing a combustion chamber of the engine respectively and supplying electricity to the spark plugs, and detecting knocking based on ion current flowing in the ignition circuits. <P>SOLUTION: The sub spark plug 7b is provided at an end part of an intake air side of an intake and exhaust air direction (Y direction) where pressure vibration in a combustion chamber gets to roughly maximum value when knocking occurs, and knocking is detected based on ion current flowing in the ignition circuit corresponding to the sub spark plug 7b. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention belongs to a technical field related to a knocking detection apparatus using an ionic current generated in a combustion chamber of an engine.

  Conventionally, as this kind of knocking detection device, an ion current generated in a combustion chamber after ignition of an air-fuel mixture in a spark ignition engine is detected, and based on this, knocking of the engine and its precursor are detected. It has been known.

  In this knocking detection device, spark plugs for spark ignition are usually provided at the center of each combustion chamber, and an ignition circuit is provided for energizing each spark plug. The ignition circuit is connected to a capacitor for accumulating charges when the ignition circuit is energized and an ion current detection means for detecting an ion current flowing through the ignition circuit. The knocking detection device closes the ignition circuit using, as a medium, ions generated on the flame surface due to the growth of flame nuclei accompanying ignition and ions ionized from the burned gas as the temperature in the combustion chamber increases after ignition. And ionic current is conducted to the ignition circuit by discharging the charge accumulated in the capacitor.

For example, in the knocking detection device disclosed in Patent Document 1, the ion current is detected by the ion current detection unit, and if the detected ion current is equal to or greater than a predetermined value, it is determined that knocking has occurred. It is like that. In addition to this, a device that detects a knocking occurrence predictor based on the peak occurrence time of an ion current is known (see, for example, Reference 2).
JP-A-9-273470 JP 2006-46140 A

  By the way, when knocking occurs, a pressure wave (shock wave) due to spontaneous ignition of unburned gas is generated and reciprocally propagates in the combustion chamber while repeatedly reflecting from its wall surface. The temperature of each part in the combustion chamber changes, and as a result, the number of ions due to thermal ionization of the burned gas increases and decreases, and accordingly, the ion current value also increases and decreases.

  As described above, since the increase or decrease in the ionic current value that occurs when knocking occurs is caused by reflection of pressure waves (vibration of pressure waves), the nature of the wave causes the pressure to vary depending on the location in the combustion chamber. A portion where the intensity (amplitude) of the wave increases (a portion corresponding to the antinode of the wave) and a portion where the intensity (a portion corresponding to the wave node) decreases. For this reason, even when the same knocking occurs, a portion where the amount of change in the ionic current value is large and a portion where the amount of change in the ion current value is small are generated depending on the location in the combustion chamber.

  For this reason, for example, in the engine having a so-called primary knock vibration characteristic in which a node of a pressure wave exists in the center of the combustion chamber and a belly exists in the peripheral portion, the above-mentioned Patent Document 1 and Patent Document 2 are used as the knock detection device. When a detection device that performs knocking detection based on the detection value of the ionic current generated when knocking occurs as shown in FIG. 4 is used, the ignition device is provided with a spark plug at the center of each combustion chamber. There is a problem in that the amount of change in the ion current detected by the ion current detection means becomes small and the knocking detection accuracy decreases.

  The present invention has been made in view of such points, and an object of the present invention is to devise a configuration for an engine knocking detection device that detects knocking based on an ion current generated in a combustion chamber. The aim is to improve knocking detection accuracy by elaborating.

  In order to achieve the above object, according to the present invention, at least one of the plurality of spark plugs is disposed in the maximum vibration portion where the amplitude of the pressure vibration at the time of occurrence of knocking in the combustion chamber is substantially maximized. Knocking is detected based on the ionic current flowing through the ignition circuit corresponding to the ignition plug disposed in the vibration part.

  Specifically, according to the first aspect of the present invention, an ignition circuit that is provided on an ignition plug disposed on a ceiling surface of the engine facing the combustion chamber of the engine and energizes the ignition plug, and an ion current generated in the combustion chamber. An engine knock detection device including an ion current detection means for detecting the knocking and a knocking detection means for detecting knocking based on the ion current detected by the ion current detection means.

  A plurality of the spark plugs are disposed on the ceiling surface, and at least one of them is a maximum vibration part that is a part corresponding to an antinode of a pressure wave at the time of occurrence of knocking in the combustion chamber or the vicinity thereof. A maximum vibration part ignition plug disposed at the front, and at least an ignition circuit corresponding to the maximum vibration part ignition plug is connected to the ion current detection means, and the knock detection means is the maximum It is assumed that knocking is detected based on the ionic current detected by the ionic current detection means of the ignition circuit corresponding to the vibration part spark plug.

  With the above configuration, knocking detection by the knocking detection unit can be reliably performed. That is, when knocking occurs, the value of the ionic current flowing through the ignition circuit corresponding to each spark plug also vibrates due to the vibration of the pressure wave in the combustion chamber. Therefore, the vibration amplitude of the ionic current flowing through the ignition circuit corresponding to the maximum vibration part spark plug is as follows. The maximum vibration part ignition plug is larger than the case where the maximum vibration part spark plug is disposed in a portion other than the maximum vibration part. Therefore, the change (vibration) of the ionic current value at the time of occurrence of knocking can be reliably detected by the ion current detection means, and as a result, knocking can be reliably detected by the knocking detection means.

  According to a second aspect of the present invention, in the first aspect of the present invention, the maximum vibration portion ignition plug is disposed so as to face at least one of a peripheral portion and a central portion of the combustion chamber.

  As a result, in an engine having such characteristics that the vibration mode of the pressure wave in the combustion chamber becomes a so-called secondary vibration mode at the time of occurrence of knocking, the maximum vibration portion spark plug is surely faced to the maximum vibration portion. It becomes possible to do.

  That is, the secondary vibration mode is usually generated by a pressure wave reciprocating radially through the center of the combustion chamber. When this vibration mode occurs, The part (maximum vibration part) which becomes an antinode of a pressure wave will be located in (the peripheral part of a combustion chamber) and the center part of a combustion chamber. Therefore, by disposing the maximum vibration portion ignition plug so as to face at least one of the peripheral portion and the center portion of the combustion chamber, the maximum vibration portion ignition plug can be reliably exposed to the maximum vibration portion. Therefore, the same effect as that of the invention of claim 1 can be obtained more reliably.

  According to a third aspect of the present invention, in the first aspect of the present invention, the maximum vibration portion ignition plug is disposed so as to face at least one side end portion in the intake and exhaust directions in the combustion chamber.

  This makes it possible to reliably detect knocking in an engine having such a characteristic that the vibration mode of the pressure wave in the combustion chamber when the knocking occurs becomes a so-called primary vibration mode.

  That is, the primary vibration mode is normally generated by the reciprocal propagation of the pressure wave in the intake / exhaust direction, and when this vibration mode occurs, the both ends of the intake / exhaust direction in the combustion chamber The part (maximum vibration part) which becomes the antinode of a pressure wave will be located. Therefore, as in the present invention, the maximum vibration portion ignition plug is disposed at least at one side end in the intake / exhaust direction, so that the maximum vibration portion ignition plug is securely disposed facing the maximum vibration portion. Can do. Therefore, the same effect as that of the invention of claim 1 can be obtained more reliably.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the maximum vibration portion spark plug is disposed facing an intake side end portion of the combustion chamber in the intake and exhaust directions.

  As a result, in an engine having such characteristics that the vibration mode of the pressure wave in the combustion chamber at the time of occurrence of knocking becomes the primary vibration mode, knocking can be detected at an early stage. That is, the pressure wave that triggers the primary vibration mode (knocking) is normally generated at the intake side end in the intake and exhaust directions in the combustion chamber. Therefore, by disposing the maximum vibration part ignition plug at the intake side end in the intake and exhaust directions in the combustion chamber, the maximum vibration part ignition plug can be surely faced to the maximum vibration part, and the knocking trigger is provided. It becomes possible to detect the change in the ionic current value caused by the generation of the pressure wave that becomes the ionic current detection means. Therefore, knocking can be detected early in the generation stage by the knocking detection means.

  According to a fifth aspect of the present invention, in the third or fourth aspect of the present invention, there is provided ignition control means for performing ignition by each of the spark plugs by controlling conduction to the respective spark plugs by the respective ignition circuits. The plurality of spark plugs include a center spark plug disposed so as to face the center of the combustion chamber, and the ignition control means performs combustion ignition for burning the mixed gas in the combustion chamber. It is configured to perform one-point ignition control in which combustion ignition by the maximum vibration part ignition plug is not executed while being executed by the center ignition plug, and the knocking detection means is connected to the maximum vibration part ignition plug. It is assumed that knocking is detected based on the ion current detected by the ion current detection means of the corresponding ignition circuit.

  This makes it possible to reliably detect the change (vibration) of the ionic current flowing through the ignition circuit corresponding to the maximum vibration portion ignition plug when knocking occurs by the ionic current detection means provided in the ignition circuit. .

  That is, the ionic current flowing through the ignition circuit is usually much smaller than the spark discharge current generated by the spark plug. For this reason, during ignition discharge of the spark plug, even if knocking occurs, a change in the ionic current flowing through the ignition circuit cannot be detected by the ionic current detection means. There is a problem that detection becomes impossible.

  However, according to the present invention, the ignition for combustion by the maximum vibration portion ignition plug is not executed by the ignition control means. Therefore, after the start of combustion of the mixed gas in the cylinder, the maximum is not performed during the combustion process. Ignition by the vibration part spark plug is not executed, and therefore no spark ignition current flows through the ignition circuit corresponding to the maximum vibration part spark plug during the combustion process. Therefore, when knocking occurs, a change in the ionic current flowing through the ignition circuit corresponding to the maximum vibration part ignition plug can be reliably detected by the ionic current detection means. As a result, the knocking detection by the knocking detection means can be performed. Detection can be performed reliably.

  In addition, according to the present invention, the center ignition plug is provided, and the ignition for combustion is executed by the center ignition plug, so that the combustion reaction can be started from the center of the combustion chamber. Thus, it is possible to quickly complete the combustion reaction of the mixed gas in the combustion chamber and improve the knocking resistance.

  According to a sixth aspect of the invention, in the fifth aspect of the invention, the ignition control means executes the one-point ignition control when the operating state of the engine is in a high speed range, while the operating state of the engine is low. It is configured to perform two-point ignition control in which combustion ignition for burning the mixed gas in the combustion chamber is sequentially executed by the center spark plug and the maximum vibration spark plug when in the rotation region. And the knocking detection means detects knocking based on the ion current detected by the ion current detection means of the ignition circuit corresponding to the maximum vibration part ignition plug when the operating state of the engine is in a high rotation region. On the other hand, when the operating state of the engine is in the low rotation range, the ion current detecting means of the ignition circuit corresponding to the center spark plug is used. Based on the issued ion current is assumed to be configured to detect the knocking.

  As a result, when the engine is in the high speed region, the one-point ignition control is executed by the ignition control means, the combustion ignition by the maximum vibration part ignition plug is executed, and the maximum knocking detection means performs the maximum ignition. Knocking detection is performed based on the ion current flowing through the ignition circuit corresponding to the vibration part ignition plug. Thus, the same effect as that attained by the 4th aspect can be attained.

  On the other hand, when the engine is in the low speed region, the ignition control means performs the two-point ignition control. As a result, after the combustion ignition by the center spark plug is executed and the combustion starts, the periphery of the combustion chamber Ignition is performed by the maximum vibration part spark plug disposed in the part. By doing this, after the combustion reaction is started by combustion ignition by the center spark plug, before the unburned gas at the peripheral edge in the combustion chamber is spontaneously ignited, the unfired gas is surely secured by the maximum vibration spark plug. Can be burned. Therefore, the combustion reaction in the combustion chamber can be completed quickly, and as a result, it is possible to suppress the occurrence of knocking in the low-speed region of the engine where the combustion reaction in the combustion chamber becomes relatively unstable.

  In addition, when the engine is in the low rotation region, knocking is detected based on the ion current detected by the ion current detection means of the ignition circuit corresponding to the center spark plug, thereby improving the knocking detection accuracy. Can be achieved.

  That is, the ignition by the maximum vibration part ignition plug is performed in the latter half of the combustion reaction from the viewpoint of suppressing the occurrence of knocking as described above. For this reason, the ignition timing of the maximum vibration part ignition plug is close to the timing of occurrence of knocking. Therefore, even if knocking occurs, an ignition circuit corresponding to the maximum vibration part ignition plug is provided for the spark discharge current due to the ignition. There is a problem that a change in flowing ion current cannot be detected. However, since the ignition by the center spark plug triggers the combustion reaction and is performed at the early stage of the combustion reaction, it is executed at a relatively early stage from the knocking occurrence time, and the engine is low. When in the rotation region, the time until the combustion reaction is completed is longer than when the engine is in the high rotation region. For this reason, the spark ignition current from the center spark plug does not continue to flow until the knocking occurrence time (the second half of the combustion reaction). Therefore, even when knocking occurs, a change in ion current flowing through the ignition circuit corresponding to the center spark plug can be reliably detected by the ion current detection means. Therefore, it is possible to reliably detect knocking by the knocking detection means and improve the knocking detection accuracy.

  As described above, according to the engine knock detection device of the present invention, at least one of the plurality of spark plugs is disposed in the maximum vibration portion where the amplitude of the pressure vibration when knocking occurs in the combustion chamber is substantially maximum. In addition, it is possible to improve the detection accuracy of knocking by the knocking detection means by detecting knocking based on the ion current flowing through the ignition circuit corresponding to the ignition plug disposed in the maximum vibration part. It becomes.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows an engine 1 provided with a knocking detection device according to an embodiment of the present invention, in which a plurality of cylinders 2, 2,... (Only one is shown in the figure) are arranged in series. It is regarded as a spark ignition direct gasoline engine. As shown in the figure, the upper end of the cylinder 2 opens at the upper end surface of the cylinder block 3 and is closed by the lower surface of the cylinder head 4 mounted thereon. A piston 5 is fitted in the cylinder 2 so as to be able to reciprocate, and a combustion chamber 6 is defined between the upper surface of the piston 5 and the lower surface of the cylinder head 4. That is, the lower surface of the cylinder head 4 constitutes the ceiling surface of the combustion chamber 6. The ceiling surface is a so-called pent roof type having an intake side inclined surface 6a and an exhaust side inclined surface 6b as shown only in FIG. A ridge line 6c between the intake-side inclined surface 6a and the exhaust-side inclined surface 6b extends in the cylinder radial direction through the center of the cylinder bore on the ceiling surface. On the other hand, a crankshaft (not shown) is disposed in the crankcase below the piston 5 and is connected to the piston 5 by a connecting rod.

  As will be described later, the cylinder head 4 is provided with two spark plugs 7a and 7b (a main spark plug 7a and a sub spark plug 7b) for each cylinder 2, and an electrode at each tip thereof faces the combustion chamber 6. The base end of each spark plug 7 is connected to ignition circuits 80 and 81, respectively.

  By the way, the shape of the combustion chamber (valve pinching angle etc.) is determined so as to shorten the flame propagation distance and improve the combustion speed so that the anti-knock performance is not less than the predetermined performance. The shape of the combustion chamber is one of factors affecting the knock vibration characteristics of the engine 1, that is, the vibration mode of the pressure wave generated in each cylinder 2 when knocking (abnormal combustion) occurs in each cylinder 2. In this embodiment, this vibration mode is such that the portion of the pressure wave generated in the cylinder 2 when knocking is located at the center of the combustion chamber 6 (the center of the cylinder 2). The part which becomes an antinode becomes what is called a primary vibration mode located in the both ends of the intake-exhaust direction (Y direction) in the combustion chamber 6 (refer FIG. 3). Here, the propagation direction of the pressure wave generated in the combustion chamber 6 approximately coincides with the intake / exhaust direction (Y direction). The intake / exhaust direction (Y direction) refers to the center axis Z axis of the combustion chamber 6 and the centers of the intake ports 9 and 9 (or the exhaust port 10) when viewed from the central axis direction (Z axis direction) of the cylinder 2. , 10 center) means the Y-axis direction passing through the midpoint of the line segment. In the following description, the X-axis direction passing through the Z-axis and orthogonal to the Y-axis is referred to as a bore arrangement direction.

  As shown in FIG. 2, a main spark plug 7a as a central spark plug is disposed in a portion of the combustion chamber 6 closer to the exhaust side in the intake and exhaust directions than the central axis Z. At the end of the intake side in the intake / exhaust direction (Y direction), a sub ignition plug 7b as a maximum vibration part ignition plug is disposed. More specifically, the auxiliary spark plug 7b is disposed corresponding to a portion (maximum vibration portion) where the amplitude of the pressure wave becomes substantially maximum when the knocking occurs, that is, an antinode portion of the pressure wave. It can also be said that the auxiliary spark plug 7 b is disposed facing the maximum vibration part of the combustion chamber 6.

  As shown in FIG. 4, each of the ignition circuits 80 and 81 includes an igniter 8a made of a power transistor and an ignition coil 8b, and is controlled by a PCM 30 (ignition control means, knocking detection means) described later. In response to the signal, each cylinder 2 is energized to each spark plug 7a, 7b at a predetermined timing (ignition timing). In this example, an ion current detection circuit 34 (ion current detection means) is connected to each of the ignition circuits 80 and 81, so that an ion current generated with a combustion reaction in the combustion chamber 6 can be detected as will be described later. Yes.

  The cylinder head 4 has two intake ports 9 and two exhaust ports 10 for each cylinder 2 so as to open to the intake side inclined surface 6a (see FIG. 2) and the exhaust side inclined surface 6b facing the combustion chamber 6. Each of the port openings is provided with intake and exhaust valves 11, 12,... (Intake and exhaust valves, see FIG. 1) so as to be opened and closed by cam shafts. Although not shown in the figure, one camshaft is provided on each of the intake side and the exhaust side, and is connected to the crankshaft by a common cam chain. The intake shaft is synchronized with the rotation of the crankshaft. The intake and exhaust valves 11, 12,... Are opened and closed at predetermined timings by rotating the side and exhaust side camshafts, respectively.

  In this example, the variable phase mechanism 13 (see FIG. 1, Variable) is capable of continuously changing the phase relative to the rotation of the crankshaft within a predetermined angle range (for example, 40 to 60 ° CA). Valve Timing (hereinafter also referred to as VVT) is attached, and the lift curve In of the intake valve 11 is changed to the advance side and the retard side by this VVT 13. Along with this, the overlap period of the exhaust valve 12 with the lift curve Ex changes, whereby the amount of burnt gas (hereinafter referred to as internal EGR) remaining in the combustion chamber 6 also changes.

  An intake passage 15 is disposed on one side of the cylinder head 4 (left side in the figure) so that the downstream end communicates with the intake port 9. The upstream end of the intake passage 15 is connected to an air cleaner 16 for filtering fresh air introduced from the outside. From there, an air flow sensor 17 for detecting the intake flow rate in order toward the downstream side, and an electric motor 18a. And a throttle valve 18 that throttles the intake passage 15 by being driven by. Although not shown in the figure, each branch passage of the intake manifold of the intake passage 15 is bifurcated, and each of the bifurcated passages is connected to the intake port 9. A tumble swirl control valve (hereinafter referred to as TSCV) 14 that adjusts the strength of the intake air flow in the combustion chamber 6 for each cylinder 2 is provided in one of the bifurcated passages. Further, the cylinder head 4 is provided with a plurality of injectors 19, 19,... (Only one is shown in the drawing) for directly injecting fuel into the combustion chamber 6 for each cylinder 2.

  On the other hand, on the opposite side of the cylinder head 4 (the right side in FIG. 1), an exhaust passage 20 communicates with the exhaust port 10 and exhausts burnt gas (exhaust gas) from the combustion chamber 6 in each cylinder 2. It is arranged. In this exhaust passage 20, in order from the upstream side, an oxygen concentration sensor (hereinafter referred to as O2 sensor) 21 for detecting the air-fuel ratio of the air-fuel mixture based on the oxygen concentration in the exhaust gas, and a catalyst for purifying the exhaust gas A converter 22 is provided. Although not shown in the figure, each branch passage of the exhaust manifold of the exhaust passage 20 is bifurcated, and each of the bifurcated passages is connected to the exhaust port 10.

  Further, an exhaust gas recirculation passage 24 (hereinafter referred to as an EGR passage) for recirculating a part of the exhaust gas to the intake air passage 15 is branched and connected to the exhaust passage 20 upstream of the O2 sensor 21. The downstream end of the passage 24 communicates with the intake passage 15 on the downstream side of the throttle valve 18. An electric flow control valve 25 (hereinafter referred to as EGR valve) whose opening degree can be adjusted is disposed near the downstream end of the EGR passage 24, and exhaust gas recirculated through the EGR passage 24 (hereinafter referred to as external EGR). The flow rate is adjusted.

  Furthermore, a crank angle sensor 26 comprising an electromagnetic pickup or the like for detecting the rotation angle (crank angle) of the crankshaft is provided in the crankcase below the cylinder block 3 of the engine 1. The crank angle sensor 26 is an electromagnetic pickup that outputs a signal corresponding to the passage of a convex portion provided on the outer peripheral portion thereof as the rotor 27 attached so as to rotate integrally with the end portion of the crankshaft is rotated. It consists of a coil 26. Further, a water temperature sensor 28 for detecting the temperature state of the cooling water is provided on the water jacket (not shown) of the cylinder block 3.

  Output signals from the air flow sensor 17, the O2 sensor 21, the crank angle sensor 26, the water temperature sensor 28, etc. are input to a PCM (Power-train Control Module) 30, respectively. As is well known, the PCM 30 includes a CPU, ROM, RAM, an I / O interface circuit, etc. In addition to the above sensors, a cam angle sensor 31 that detects at least the rotation angle (rotation position) of the intake camshaft. And an accelerator opening sensor 32 that detects the operation amount of the accelerator pedal, and an engine speed sensor 33 that detects the engine speed, respectively.

  The PCM 30 determines the operating state of the engine 1 based on the signals input from the sensors and controls the operation of the engine 1 accordingly. That is, the PCM 30 outputs a signal for controlling the operation timing of the intake valve 11 to the VVT 13, outputs a signal for controlling the intake flow rate to the throttle valve 18, and outputs to the TSCV 14 for each cylinder 2. A signal for controlling the strength of the intake air flow in the combustion chamber 6 is output, and a pulse signal for controlling the fuel injection amount and the injection timing is output to the injectors 19, 19,. Then, a signal for controlling the amount of exhaust gas (external EGR) circulating to the intake system through the EGR passage 24 is output to the EGR valve 25.

  Further, the PCM 30 explodes and burns the mixed gas when the engine 1 is in a high rotation region A (see FIG. 5) in which the engine rotation speed is equal to or higher than a predetermined rotation speed N1 (for example, 2000 rpm). Combustion ignition is executed by the main ignition plug 7a while one-point ignition control is executed so that the combustion ignition by the auxiliary ignition plug 7b is not executed, and the engine speed is higher than the predetermined speed N1. When the engine is in the small low rotation region B (see FIG. 5), two-point ignition control is executed in which combustion ignition for causing the mixed gas to explode and combustion is executed in this order by the main ignition plug 7a and the auxiliary ignition plug 7b. It is configured.

  Further, when the engine 1 is in the low rotation region B, the PCM 30 detects the ion current detected by the ion current detection circuit 34 of the ignition circuit 80 (hereinafter referred to as the main ignition circuit 80) corresponding to the main ignition plug 7a. On the other hand, when the engine 1 is in the high rotation region A, the ion of the ignition circuit 81 (hereinafter referred to as the sub-ignition circuit 81) corresponding to the sub-ignition plug 7b which is the maximum vibration part ignition plug is detected. Knocking detection control for performing knocking detection based on the ion current detected by the current detection circuit 34 is executed.

  Next, the knocking detection control by the PCM 30 will be described with reference to the flowchart of FIG.

  First, in the first step S1, various signals from the respective sensors are read.

  In step S2, based on the signal read in step S1, it is determined whether or not the engine 1 is in a knocking determination area that requires the determination of knocking. If this determination is YES, the process proceeds to step S3. In this case, the determination in step S2 is performed again.

  Specifically, based on detection signals from the water temperature sensor 28 and the engine speed sensor 33, the temperature of the cooling water and the engine speed are calculated. The engine speed is greater than 500 rpm and less than 5500 rpm, and the coolant temperature is When the condition of 70 ° C. or higher is satisfied, a determination of YES is made, and when the condition is not satisfied, a determination of NO is made.

  In step S3, based on the signal read in step S1, it is determined whether or not the engine 1 is in the high rotation region A. If this determination is YES, the process proceeds to step S4, and if NO (engine 1 is If it is in the low rotation region B), the process proceeds to step S9.

  In step S4, one-point ignition control is performed in which combustion ignition for burning the mixed gas in the combustion chamber 6 is executed by the main ignition plug 7a while combustion ignition by the auxiliary ignition plug 7b is not executed.

  Specifically, when the crank angle of the crankshaft reaches the set ignition angle after the start of the expansion stroke, the main ignition circuit 80 is energized to perform ignition by the main ignition plug 7a, thereby mixing in the combustion chamber 6 Gas combustion is started (see FIG. 7).

  Then, during the exhaust stroke after the expansion stroke, the auxiliary ignition circuit 81 is energized to perform ignition by the auxiliary ignition plug 7b. Here, the ignition by the auxiliary ignition plug 7b is a so-called discarding ignition that does not contribute to the output of the engine 1 without causing a combustion reaction due to the ignition because it is performed during the exhaust stroke. The capacitor 34a of the ignition circuit 81 is charged.

  In step S5, whether or not knocking has occurred is determined based on the ion current detected by the ion current detection circuit 34 provided in the sub-ignition circuit 81 during the expansion stroke, that is, during the combustion reaction of the unburned gas. When it is determined that knocking has occurred, the strength is determined.

  Specifically, in this embodiment, when the ion current value detected by the ion current detection circuit 34 is less than a predetermined lower limit current value, it is determined that knocking has not occurred, and the ion current is determined. When the value is equal to or greater than the lower limit current value, it is determined that knocking has occurred, and the intensity level is determined based on the magnitude of the ion current value.

  In step S6, the ignition timing of the main spark plug 7a in the next cycle is set based on the determination in step S5, and the process ends after the setting. Specifically, when it is determined in step S5 that knocking has not occurred, the set ignition angle is not changed. On the other hand, when it is determined that knocking has occurred, the strength level thereof is not changed. Is larger, the ignition timing is delayed, that is, the set ignition angle is retarded to obtain a new set ignition angle.

  In step S7, it is determined whether or not to proceed to the next combustion cycle, that is, whether or not the operation of the engine 1 is continued. If this determination is YES, the process returns to step S2, while if NO, the process ends. To do.

  In step S8, which proceeds in the case of NO in step S3, two-point ignition control is performed in which combustion ignition is executed in this order by the main spark plug 7a and the sub spark plug 7b.

  Specifically, immediately after the start of the expansion stroke, and when the crank angle of the crankshaft reaches the set ignition angle, the main ignition circuit 80 is energized to perform ignition by the main ignition plug 7a, whereby the inside of the combustion chamber 6 Then, in the latter half of the combustion reaction of the mixed gas, the auxiliary ignition circuit 81 is energized to ignite the auxiliary ignition plug 7b, thereby promoting the combustion of the unburned gas (FIG. 8). reference).

  In step S9, whether or not knocking has occurred by the same determination method as in step S5 based on the ionic current detected by the ionic current detection circuit 34 provided in the main ignition circuit 80 during the expansion stroke. After the determination and the knocking strength determination when knocking has occurred, the process proceeds to step S6.

  When the engine 1 equipped with the PCM 30 as the knocking detection means configured as described above is in the high speed region A (when the determination in step S3 is YES), the one-point ignition control is executed by the PCM 30 (step S3). As a result, the ignition for combustion by the main spark plug 7a disposed in the combustion chamber 6 is executed on the cylinder 2 after the transition from the compression stroke to the expansion stroke. The ignition for combustion by the auxiliary ignition plug 7b is not executed.

  The combustion ignition of the main spark plug 7a causes the combustion reaction of unburned gas in the cylinder 2 to occur, and ions accompanying the combustion reaction are generated in the cylinder 2. As a result, the main ignition circuit 80 and In each of the sub-ignition circuits 81, an ion current using ions as a medium flows.

  The ion current detection circuits 34 and 34 provided in the respective ignition circuits 80 and 81 detect ion currents flowing through the respective ignition circuits 80 and 81 and transmit this ion current information to the PCM 30. Specifically, the ion current detection circuit 34 (see FIG. 4) includes a power supply capacitor 34a connected in series to an end opposite to the ignition plug 7 where the secondary side of the ignition coil 8b is grounded, and a detection circuit. 34b, and when the ignition plug 7 is energized (ignited) by the operation of the igniter 8a, a circuit is constituted by the electric charge stored in the power supply capacitor 34a and the ions generated in the combustion chamber 6 to form a current. (Ion current) flows. That is, the ionic current is generated in the combustion chamber 6 by releasing the charge accumulated in the power supply capacitor 34a. The ionic current is detected by the detection circuit 34b and output to the PCM 30 as ionic current information.

  Here, the waveform (value) of the ionic current detected by the ionic current detection circuit 34 of the sub-ignition circuit 81 changes with the progress of the crank angle after ignition by the main spark plug 7a as shown by the solid line in FIG. The waveform usually has two peaks, the first half and the second half. The ionic current represented in the first half of the mountain is thought to be based on ions (radicals) present on the flame surface that expand as the flame nuclei grow after the mixture has ignited. Are strongly influenced by the speed of the gas and the flow strength of the combustion chamber 6. That is, the first half of the mountain becomes steeper as the initial combustion becomes active, and its peak advances. In addition to the ions (radicals) generated by the combustion reaction itself as described above, the ion current represented by the peaks in the latter half is generated by the thermal ionization of NOx present in the burned gas as the temperature of the combustion chamber 6 rises. It is considered that the ions are also used as a medium, and the peak appears at the crank angle position where the temperature of the combustion chamber 6 is highest, and as a whole, the higher the combustion is, the lower the slower the combustion is. .

  When knocking occurs, a vibration component of ion current (corresponding to a portion indicated by a two-dot chain line in FIG. 9) caused by pressure vibration in the combustion chamber 6 due to the occurrence of knocking is indicated by a solid line in FIG. It appears in a portion (hereinafter referred to as knock vibration superimposing portion V) that is superimposed on the ion current waveform shown in FIG.

  On the other hand, the waveform (value) of the ionic current detected by the ionic current detection circuit 34 of the main ignition circuit 80 is almost the same as the large current region E in the two peaks including the knock vibration superimposing portion V, as shown in FIG. Is different from the current waveform (see FIG. 9) flowing through the sub-ignition circuit 81 in that it is indistinguishable. This is because although the ion current corresponding to the two peaks flows also in the ion current detection circuit 34 of the main ignition circuit 80, the current flowing through the main ignition circuit 80 when the main spark plug 7a is ignited (spark discharge current). This is because the waveform of the ion current is erased by the large current region E corresponding to the spark discharge current because the value of the ion current is extremely small. Therefore, even when knocking occurs, the vibration waveform of the ion current that appears in the knock vibration superimposing portion V is erased by the large current region E and cannot be identified.

  Further, when the engine 1 is in the low speed region B (when the determination in step S3 is NO), the two-point ignition control is executed by the PCM 30 (the process of step S8 is executed). The ignition for combustion by the spark plug 7a and the sub spark plug 7b is executed in this order during the expansion stroke. The ion current detection circuits 34 and 34 provided in the ignition circuits 80 and 81 detect ion currents flowing through the ignition circuits 80 and 81 during the expansion stroke, and the ion current information is transmitted to the PCM 30. The

  Here, as shown in FIG. 11, the waveform (value) of the ion current detected by the ion current detection circuit 34 provided in the sub-ignition circuit 81 has its peak in the latter half of the two peaks. The excessive portion, that is, the knock vibration superimposing portion V is erased by the large current region E corresponding to the spark ignition current due to the ignition of the auxiliary spark plug 7b and cannot be identified. Therefore, even when knocking occurs, the vibration waveform of the ion current that appears in the knock vibration superimposing portion V is erased by the large current region E and cannot be identified.

  On the other hand, the waveform (value) of the ion current detected by the ion current detection circuit 34 disposed in the main ignition circuit 80 includes the peak in the first half of the two peaks as shown in FIG. The portion (the portion indicated by the two-dot chain line in the figure) is erased by the large current region E corresponding to the spark ignition current due to the ignition of the main spark plug 7a and becomes indistinguishable. It is outside the large current region E and can be identified.

  When the combustion chamber 6 is in a misfire state, no ions are generated in the combustion chamber 6 and therefore no ion current is detected.

  In the above embodiment, when the engine 1 is in the high rotation region A (when the determination in step S3 is YES), the PCM 30 performs the ion of the sub ignition circuit 81 during the expansion stroke (combustion reaction). Based on the ion current detected by the current detection circuit 34, it is determined whether knocking has occurred (detection of knocking) (the process of step S5 is executed). Here, in the above-described embodiment, the auxiliary ignition plug 7b is disposed facing the maximum vibration portion where the amplitude of the pressure wave at the time of occurrence of knocking in the combustion chamber 6 is maximized. The vibration amplitude (vibration component) of the ionic current detected by the detection circuit 34 can be increased as compared with the case where the auxiliary spark plug 7b is disposed in a portion other than the maximum vibration portion. Therefore, the knocking determination process performed in step S5 can be performed reliably.

  In the above embodiment, when it is determined that knocking has occurred, the PCM 30 determines the knocking intensity and delays the ignition timing according to the intensity (executes the control process of step S6). It has become. As a result, the higher the knocking strength level, the lower the pressure (pressure ratio) in the combustion chamber 6 at the time of ignition, thereby lowering the combustion chamber temperature. As a result, the occurrence of knocking in the subsequent cycle is suppressed. It becomes possible.

  Further, in the above embodiment, the auxiliary spark plug 7b is disposed so as to face the portion that is the maximum vibration portion in the combustion chamber 6 and is located at the end portion on the intake side. This enables early detection of knocking by the PCM 30. That is, the pressure vibration generated in the combustion chamber 6 when knocking occurs (pressure vibration having the primary vibration mode) usually starts from a pressure wave (shock wave) generated at the end on the intake side in the combustion chamber 6. However, the auxiliary ignition plug 7b is disposed at the portion where the pressure wave that is the starting point is generated (the end on the intake side of the combustion chamber 6). With the current detection circuit 34, it is possible to reliably detect a change in ion current caused by the pressure wave that is the starting point. Therefore, early detection of knocking becomes possible.

  Further, in the above embodiment, when the engine 1 is in the high rotation region A (when the determination in step S3 is YES), the PCM 30 performs the combustion by the auxiliary ignition plug 7b during the expansion stroke (combustion reaction). The ignition is not executed (step S4). Therefore, when knocking occurs, the ion current detection circuit 34 can reliably detect the vibration component of the ion current.

  That is, the spark ignition current due to the ignition of the secondary spark plug 7b does not flow in the secondary ignition circuit 81 during the expansion stroke. Therefore, the vibration component of the ion current flowing through the ion current detection circuit 34 due to the occurrence of knocking is For example, as shown in FIG. 10 (when ion current detection is performed by the ion current detection circuit 34 of the main ignition circuit 80), it is prevented from being erased by the spark ignition current and becoming indistinguishable. The vibration component can be reliably detected. Therefore, it is possible to reliably perform the knocking detection in step S5 based on the change amount of the ionic current, and to improve the knocking detection accuracy.

  Further, in the above embodiment, when the engine 1 is in the high rotation region A (when the determination in step S3 is YES), the PCM 30 performs the ignition by the auxiliary ignition plug 7b during the exhaust stroke (in step S4). Control processing).

  As a result, the auxiliary ignition circuit 81 is energized and distributed to the auxiliary ignition circuit 81 without affecting the combustion reaction in the combustion chamber 6 during the expansion stroke, that is, without affecting the engine output of the engine 1. The provided capacitor 34a can be charged. In this way, by charging the capacitor 34a, the sub-ignition circuit 81 is in a state in which ion current can be conducted by discharging the capacitor 34a when ions are generated in the combustion chamber 6. Accordingly, during the subsequent expansion stroke (combustion reaction), the ion current can be reliably conducted to the ion current detection circuit 34, and knocking detection based on the ion current in the PCM 30 can be reliably performed. It becomes.

  Furthermore, in the above embodiment, when the engine 1 is in the low rotation region B (when the determination in step S3 is NO), the PCM 30 burns with the main spark plug 7a and the auxiliary spark plug 7b during the expansion stroke. Two-point ignition control (control processing in step S8) for sequentially executing the ignition is executed. As a result, in the low rotation region B where the combustion in the combustion chamber 6 becomes unstable compared to when the engine 1 is in the high rotation region A, the two ignition plugs of the main ignition plug 7a and the auxiliary ignition plug 7b are used for combustion. Ignition can be performed, and stable combustion in the low rotation region B is possible. Therefore, it is possible to improve the thermal efficiency in the low rotation region B of the engine 1.

  In the above embodiment, when the engine 1 is in the low rotation region B (when the determination in step S3 is NO), the PCM 30 performs the ionic current of the main ignition circuit 80 during the expansion stroke (combustion process). Knocking is detected based on the ion current detected by the detection circuit 34. Thereby, even when the two-point ignition control is executed as described above, the knocking can be reliably detected by the PCM 30.

  That is, as described above, in the waveform of the ionic current flowing through the auxiliary ignition circuit 81, the knock vibration superimposing portion V is included in the large current region E. For this reason, when knocking occurs, the ion current circuit of the sub-ignition circuit 81 cannot detect a change (vibration component) of the ion current accompanying the occurrence of knocking. However, in the waveform of the ionic current flowing through the main ignition circuit 80, the knock vibration superimposed portion V is outside the large current region E. Therefore, when knocking occurs, the ion current detection circuit 34 of the main ignition circuit 80 can reliably detect a change (vibration component) of the ion current accompanying the occurrence of knocking. Therefore, knocking can be reliably detected by the PCM 30 based on the ion current information from the ion current detection circuit 34 of the main ignition circuit 80.

(Other embodiments)
The configuration of the present invention is not limited to the above embodiment, but includes various other configurations. That is, in the above embodiment, the engine 1 is employed in which the vibration mode of the pressure wave in the combustion chamber 6 when knocking occurs becomes the primary vibration mode. However, the present invention is not limited to this. As shown in FIG. 13, the portion that becomes the antinode of the pressure wave is located at the peripheral portion of the combustion chamber 6 and the central portion of the combustion chamber 6, while the portion that becomes the node is between the central portion and the peripheral portion of the combustion chamber 6. The engine 1 may be a secondary vibration mode located at the position. Here, the pressure wave having this secondary vibration mode propagates back and forth radially through the central portion of the combustion chamber 6 while repeating reflection from the bore wall surface, so that the central portion of the combustion chamber 6 and the combustion chamber 6 The antinode of the pressure wave is located in a range (entire peripheral portion) over the entire periphery of the peripheral portion. That is, the center portion of the combustion chamber 6 and the entire peripheral edge portion of the combustion chamber 6 become the maximum vibration portion. Therefore, in the engine 1 having such a secondary vibration mode, the spark plugs 7a and 7b used for detecting the ionic current are, for example, bore arrangement directions in the combustion chamber 6 (X direction, see FIG. 2). It may be arranged so as to face one end of the combustion chamber, or may be arranged so as to face the center of the combustion chamber 6.

  Further, in the above embodiment, the auxiliary ignition plug 7b that detects the ionic current that becomes the basis of the knocking detection by the PCM 30 at the time of high rotation is arranged at the intake side end portion in the intake and exhaust direction (Y direction) in the combustion chamber 6. However, the present invention is not limited to this. For example, as shown in FIG. 14, it may be arranged at the end on the exhaust side in the intake / exhaust direction (Y direction).

  Further, in the above embodiment, the engine 1 is a four-valve engine having two intake valves 11 and two exhaust valves 12 for each cylinder 2, but is not limited to this. For example, as shown in FIG. 15, a three-valve engine having one intake valve 11 (intake port 9) and two exhaust valves 12 (exhaust port 10) for each cylinder 2 may be used.

  INDUSTRIAL APPLICABILITY The present invention is useful for a knocking detection device that uses an ionic current generated in a combustion chamber of an engine, and is particularly useful for detecting knocking at a high engine speed.

1 is a schematic structural diagram of an engine including a combustion state detection device according to an embodiment of the present invention. It is the schematic structure figure which looked at the ceiling surface of the combustion chamber from the combustion chamber side of the axial direction. It is a schematic diagram which shows the vibration mode of the pressure wave in a combustion chamber at the time of knocking generation | occurrence | production. It is the schematic which shows the structure of an ion current detection circuit. It is explanatory drawing which shows a high rotation area | region and a low rotation area | region. It is a flowchart which shows knocking detection control in PCM (Power-train Control Module). It is explanatory drawing which shows the operation state of the main ignition circuit and sub ignition circuit in case an engine exists in a high rotation area | region. It is explanatory drawing which shows the operation state of the main ignition circuit and sub ignition circuit in case an engine exists in a low speed area | region. It is a figure which shows typically the waveform of the ion current detected by the ion current detection circuit arrange | positioned at the sub ignition circuit when an engine exists in a high rotation area | region. It is a figure which shows typically the waveform of the ion current detected by the ion current detection circuit arrange | positioned at the main ignition circuit when an engine exists in a high rotation area | region. It is a figure which shows typically the waveform of the ion current detected by the ion current detection circuit arrange | positioned at the sub ignition circuit when an engine exists in a low rotation area | region. It is a figure which shows typically the waveform of the ion current detected by the ion current detection circuit arrange | positioned at the main ignition circuit when an engine exists in a low rotation area | region. FIG. 4 is a view corresponding to FIG. 3 showing another embodiment. FIG. 3 is a view corresponding to FIG. 2 and showing another embodiment. FIG. 3 is a view corresponding to FIG. 2 showing another embodiment.

Explanation of symbols

PCM30 (knocking detection means, ignition control means)
1 Engine 6 Combustion chamber 7a Main spark plug (center spark plug)
7b Secondary spark plug (maximum vibration part spark plug)
34 Ion current detection circuit (ion current detection means)
80 Main ignition circuit (ignition circuit)
81 Sub-ignition circuit (ignition circuit)

Claims (6)

An ignition circuit that is provided on an ignition plug that faces the combustion chamber of the engine and that is disposed on the ceiling surface thereof, energizes the ignition plug, ion current detection means that detects an ion current generated in the combustion chamber, and the ion current An engine knocking detection device comprising knocking detection means for detecting knocking based on ion current detected by the detection means,
A plurality of the spark plugs are disposed on the ceiling surface, and at least one of them faces the maximum vibration part corresponding to the antinode of the pressure wave at the time of occurrence of knocking in the combustion chamber or the vicinity thereof. It is the maximum vibration part spark plug that is arranged,
The ionic current detection means is connected to an ignition circuit corresponding to at least the maximum vibration part ignition plug,
The knocking detection means is configured to detect knocking based on an ion current detected by an ion current detection means of an ignition circuit corresponding to the maximum vibration part ignition plug. apparatus. The engine knock detection device according to claim 1,
The engine knock detection device according to claim 1, wherein the maximum vibration portion ignition plug is disposed facing at least one of a central portion and a peripheral portion of the combustion chamber. The engine knock detection device according to claim 1,
The engine knock detection device according to claim 1, wherein the maximum vibration portion ignition plug is disposed facing at least one side end portion in the intake and exhaust directions in the combustion chamber. The engine knock detection device according to claim 3,
The engine knock detection device according to claim 1, wherein the maximum vibration portion ignition plug is disposed facing an intake side end portion of the combustion chamber in an intake and exhaust direction. The engine knock detection device according to claim 3 or 4,
Ignition control means for performing ignition by the spark plug by controlling conduction to the spark plug by the respective ignition circuits,
The plurality of spark plugs include a center spark plug disposed facing the center of the combustion chamber,
The ignition control means performs one-point ignition control in which combustion ignition for burning the mixed gas in the combustion chamber is executed by the center ignition plug while combustion ignition by the maximum vibration part ignition plug is not executed. An engine knocking detection device is configured to perform the following. The engine knock detection device according to claim 5,
The ignition control means executes the one-point ignition control when the engine operating state is in a high rotation region, and combusts the mixed gas in the combustion chamber when the engine operating state is in a low rotation region. Is configured to perform two-point ignition control for sequentially executing combustion ignition for the center ignition plug and the maximum vibration part ignition plug,
The knocking detection means detects knocking based on the ion current detected by the ion current detection means of the ignition circuit corresponding to the maximum vibration portion ignition plug when the operating state of the engine is in a high rotation range. The engine is configured to detect knocking based on the ion current detected by the ion current detection means of the ignition circuit corresponding to the center spark plug when the engine operating state is in the low rotation range. An engine knock detection device characterized by the above.

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