JP4451180B2 - Engine combustion detection interval setting device - Google Patents

Description

  The present invention relates to an engine combustion detection interval setting device that sets a combustion state detection interval for each cylinder based on ions or combustion pressure in a combustion chamber.

  To increase the engine output at a constant air-fuel ratio, increase the charging efficiency by supercharging with a turbocharger or inertial supercharging in a naturally aspirated engine and set the ignition timing to the optimal ignition timing (MBT: Minimum Advance for Best Torque) Then, it is sufficient to increase the thermal efficiency. However, knocking may occur when the charging efficiency is increased or the ignition timing is advanced to the optimal ignition timing. When knocking occurs, the thermal efficiency decreases, so the presence or absence of knocking is detected using a knock sensor. When knocking is detected, control is performed to avoid the occurrence of knocking by, for example, retarding the ignition timing. Is called.

  As the knock sensor, a magnetostrictive type or a piezoelectric type provided in the cylinder block is often employed. However, this type of knock sensor does not directly detect the knock generated in each cylinder, but detects the knock generated in a certain cylinder through vibration propagated to the cylinder block. The cylinder which has been cannot be specified. Therefore, when knocking is detected by the knock sensor, knock control such as retarding the ignition timing for all cylinders is performed.

  On the other hand, recently, various techniques have been proposed in which the combustion state of each cylinder is examined to detect whether or not knocking has occurred for each cylinder, and knock control is performed only on the cylinder in which knocking has occurred.

  Further, when the combustion state is detected and output as an electrical signal, noise (hereinafter referred to as “discharge noise”) generated during spark discharge is easily superimposed on the electrical signal. Therefore, in general, a gate section that avoids discharge noise is set, and a knock component is extracted from an electrical signal indicating a combustion state detected in the gate section, and the presence or absence of knocking is determined.

For example, a knock detection device disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 8-210175) detects an ionic current flowing between electrodes of a spark plug during combustion, and extracts the knock component by filtering the ionic current. On the other hand, at the time of ignition, the mask section is set by referring to the table based on the engine speed and load, etc., and detection of the ionic current is started after the lapse of the mask section. A technique for setting a knock detection interval by referring to a map based on a value, starting a knock detection interval from the time when a peak value is detected, and determining the presence or absence of a knock based on a knock component detected in the knock detection interval Is disclosed.
JP-A-8-210175

  In the technique disclosed in Patent Document 1, a mask section that avoids spark discharge and a knock detection section that determines whether or not knocking has occurred are set based on the engine operating state. However, the section where discharge noise is generated and the section where knocking is likely to occur can be set based on the engine operating state such as the engine speed and engine load in normal operation. Or, in a section where the combustion state is likely to change suddenly, such as transient operation, the mask section and knock detection section cannot be set properly, and discharge noise superimposed on the ion current and predetermined frequency components other than knock are completely removed. It can be difficult.

  Further, the engine has an individual difference for each product. Therefore, even in normal operation, the discharge time of the spark plug and the combustion period vary from engine to engine. Furthermore, variation also occurs due to aging. For engines with such individual differences, when setting the mask section and knock detection section with reference to the table and map, it is not possible to properly remove the predetermined frequency components other than discharge noise and knock, It becomes difficult to accurately determine whether knock has occurred or not.

  In view of the above circumstances, the present invention superimposes predetermined frequency components other than discharge noise and knock without being affected by the operating state of the engine, the discharge time of the spark plug, the variation in the combustion period, aging, etc. It is an object of the present invention to provide an engine combustion detection section setting device capable of always properly setting a combustion state detection section in an area avoiding the section.

In order to achieve the above object, an engine combustion detection interval setting device according to the present invention comprises a combustion detection means for detecting a combustion state of a combustion chamber and outputting a combustion signal, and a collector of an ignition transistor for switching the primary winding of the ignition coil. Combustion signal detection section setting means for setting a start gate of the detection section of the combustion signal when the end of spark discharge of the spark plug is detected based on the voltage, and after detecting the peak value of the combustion signal, The start gate is set, the combustion signal is compared with a preset end determination slice level, and after determining that the combustion signal is equal to or lower than the end determination slice level, the end gate of the knock detection section is set. And a detection section setting means.

  According to the present invention, it is possible to avoid an interval in which a predetermined frequency component other than discharge noise or knock is superimposed without being affected by the operating state of the engine, the discharge time of the spark plug, the variation in the combustion period, and the secular change. Therefore, it is possible to always set the combustion state detection section appropriately in the region.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 to 4 show a first embodiment of the present invention. FIG. 1 is an overall configuration diagram of the combustion detection zone setting device.

  Reference numeral 1 in FIG. 1 denotes an ignition coil arranged corresponding to each cylinder. One end of the primary winding 1a is connected to the battery 2, and the other end of the ignition transistor 3 that switches the primary winding 1a. Connected to the collector. Further, the emitter of the ignition transistor 3 is grounded, and an ignition signal is applied to the base. On the other hand, one end of the secondary winding 1 b of the ignition coil 1 is connected to the battery 2, and the other end is connected to the center electrode 4 a of the ignition plug 4. Further, the outer electrode 4b of the spark plug 4 is grounded.

  An ion probe 14 is disposed in the combustion chamber of each cylinder of the engine. The ion probe 14 has a pair of electrodes. A potential difference is given between the electrodes during combustion, and an ion current flows through the ion probe 14 when a flame arrives between the electrodes. It is known that the ionic current changes sharply according to the combustion state in the combustion chamber, and the waveform thereof is almost the same as the combustion waveform pressure as shown in FIG. Therefore, by monitoring the ion current, it is possible to individually grasp the combustion state (occurrence of knocking or misfire) in the cylinder. Since the ion probe 14 can be replaced by the spark plug 4, the spark plug 4 may be used as the ion probe 14.

The combustion detection zone setting device according to this embodiment includes an ion current detection circuit 11, a combustion signal detection zone setting unit 12, and a knock detection unit 13 as combustion detection means. The combustion signal detection section setting unit 12 may be an analog circuit, but can also be executed by an in-vehicle computer such as a microcomputer.

  The ion current detection circuit 11 detects an ion current flowing through the ion probe 14, and includes a capacitor that applies a high voltage to the ion probe 14, an ion current detection resistor, and the like, and is detected by the ion current detection resistor. The ion current is detected from the potential to be amplified, and the ion current is amplified and output.

The combustion signal detection section setting unit 12 monitors the voltage applied to the collector of the ignition transistor 3 (hereinafter referred to as “collector voltage”) and the ion current detected by the ion current detection circuit 11, and based on the collector voltage, The spark discharge end time is determined from the voltage change, and the ion current detection section and the knock detection section as the combustion state detection section are set from the change in the ion current. Since the collector voltage can monitor the discharge state of the spark plug 4 indirectly and relatively easily, the spark discharge end time can be easily detected from the change in the collector voltage.

The knock detection unit 13 filters the ion current output from the ion current detection circuit 11 to extract the knock current, and based on the knock current detected in the knock detection section set by the combustion signal detection section setting unit 12. Check for knocks. As a method for checking the presence / absence of knock occurrence, for example, as disclosed in Japanese Patent Application Laid-Open No. 6-159129, a technique for integrating the knock current and checking the presence / absence of knock occurrence for each cylinder based on the value, Alternatively, as disclosed in JP-A-10-252634, the knock current is integrated, the knock current is corrected based on the peak value of the ion current, and the corrected value is compared with the knock determination level. A technique for checking the occurrence of knocking for each cylinder is known.

When the on-vehicle computer has a function executed by the combustion signal detection interval setting unit 12, the on-vehicle computer sets the ion current detection interval and the knock detection interval according to the combustion detection interval setting routine shown in FIG. To do.

  This routine is started when the ignition signal output to the ignition transistor 3 is switched from ON to OFF. As shown in FIG. 3A, an ignition signal is applied to the base of the ignition transistor 3 and the ignition transistor 3 is turned on. Then, the ignition transistor 3 is turned off and the secondary winding 1b of the ignition coil 1 is turned on. When the voltage is induced, a spark discharge is generated between the electrodes 4a and 4b of the spark plug 4 as shown in FIG. 4B, and the air-fuel mixture in the combustion chamber is ignited by the spark discharge and combustion is started. The collector voltage detected during the spark discharge varies greatly as shown in FIG. 3C, and the discharge state of the spark plug 4 can be easily grasped by monitoring the collector voltage.

  First, in step S1, the collector voltage is read at predetermined intervals, and the process waits until the collector voltage is stabilized by the voltage from the battery 2 (battery voltage). Whether the collector voltage is stable is, for example, when the collector voltage read last time is compared with the collector voltage read this time, the difference is within a predetermined value, and the state continues for a set time Judged as stable. Alternatively, the collector voltage is compared with the battery voltage, and when the collector voltage becomes substantially equal to the battery voltage, it is determined that the voltage is stable.

  Then, when the collector voltage is stabilized, it is determined that the spark discharge has ended, and the process proceeds to step S2, and as shown in FIG. 3 (e), the start gate of the ion current detection section (hereinafter referred to as “ion current detection start gate”). Set.

  When the ion current detection start gate is set, reading of the ion current is started in step S3, and thereafter, the ion current is read at every predetermined calculation cycle and waits until the ion current shows a peak value. As a method of detecting the peak value of the ion current, for example, the ion current is sampled and weighted average every setting calculation, the current weighted average value is compared with the previous weighted average value, and the current weighted average is compared with the previous weighted average value. If it is lower than the weighted average and the state continues for a set period, it is determined as a peak.

  Incidentally, as shown in FIG. 3D, discharge noise is superimposed on the ion current during the spark discharge. However, in this embodiment, since the reading of the ionic current is started after the end of the discharge, the discharge noise is hardly superimposed on the ionic current.

  When the peak value of the ionic current is detected, the process proceeds to step S4, where a start gate of the knock detection section (hereinafter referred to as “knock detection start gate”) is set as shown in FIG. It is known that the high-frequency component accompanying the occurrence of knock is superimposed on the ion current after showing a peak value. Therefore, by starting knock detection from the ionic current after detecting the peak value, it is possible to remove the contamination of noise components as much as possible.

  Next, the process proceeds to step S5, where the ion current is compared with a preset slice level for end determination and waits until the ion current is stabilized below the slice level for end determination. As shown in FIG. 3 (d), the end determination slice level is obtained by setting the end time of combustion through experiments or the like, and in the determination, the ion current is equal to or lower than the end determination slice level. When the state continues for the set time, it is determined that the state is stable.

  When it is determined that the ion current is stable below the slice level for end determination, the process proceeds to step S6, and the ion current detection end gate and the knock detection end gate are set (see FIGS. 3 (e) and 3 (f)). ) Exit the routine.

  Then, as shown in FIG. 3G, the knock detection unit 13 checks the occurrence of knocking for each cylinder using the above-described method based on the knock current extracted in the knock detection section. When a knock generation cylinder is detected, knock control such as retarding the ignition timing of the knock generation cylinder is performed in the next cycle to avoid knock generation.

  Thus, in this embodiment, since the ion current detection start gate is set when the voltage of the primary winding 1a of the ignition coil 1 is monitored and this voltage is stabilized, the peak value of the ion current is detected. In doing so, it becomes difficult to be affected by the discharge noise, and the peak value can be detected with high accuracy.

  In addition, the ion detection section and the knock detection section are automatically set for each ignition based on the ion current without using a table or a map. Alternatively, even in an engine operating region where the combustion state is likely to change suddenly, such as transient operation, it is possible to always set the optimum section. Similarly, the optimum state can always be set without being affected by variations in the combustion period due to the discharge time of the spark plug 4, engine manufacturing error, etc., and aging.

  Therefore, the S / N ratio of the knock current extracted from the ion current detected in this knock detection section is improved, and the presence / absence of knock occurrence can be determined with high accuracy based on the knock current. Therefore, by performing knock control such as ignition timing control based on the knock current detected in the knock detection section, knock can be effectively avoided without suppressing the engine output more than necessary. As a result, the potential of the engine can be maximized.

  By the way, when the spark discharge from the spark plug 4 does not ignite the air-fuel mixture in the combustion chamber, that is, when misfiring occurs, the molecules in the combustion chamber are not ionized (ionized). It will not be detected. Therefore, after setting the ion current detection start gate, if the peak value of the ion current does not show a predetermined value (for example, a current value slightly higher than 0) or more, it can be determined that misfire has occurred.

  FIG. 4 shows a misfire determination routine for performing misfire determination by applying the combustion detection interval setting routine shown in FIG.

  Steps S1 to S3 are the same as the combustion detection interval setting routine shown in FIG. 2, and after detecting the peak value of the ion current in step S3, the process proceeds to step S11. When the peak value is equal to or less than the misfire determination slice level, the process proceeds to step S12, where it is determined that there is a misfire and the routine is exited. On the other hand, when the peak value is equal to or higher than the misfire determination slice level, the process branches to step S13, determines that there is no misfire, and exits the routine.

  If it is determined that a misfire has occurred, a trouble code indicating a misfire is stored at a predetermined address in the backup memory. Further, at that time, a warning lamp disposed on the instrument panel or the like may be turned on to notify the driver of the occurrence of misfire.

  5 to 7 show a second embodiment of the present invention. In the first embodiment described above, the ion current detection section and the knock detection section are set based on the ion current, but in this embodiment, from the combustion pressure sensor 22 as the combustion pressure sensing means for exposing the sensing surface to the combustion chamber. A combustion pressure detection section and a knock detection section are set based on the electrical signal. The combustion pressure sensor 22 outputs an electrical signal corresponding to the combustion pressure. When a knock occurs, a vibration component due to the knock is superimposed on the electrical signal. Therefore, the presence or absence of knocking can be detected by extracting this vibration component.

The combustion detection zone setting device according to this embodiment includes a combustion pressure detection circuit 21, a combustion signal detection zone setting unit 12, and a knock detection unit 13 as combustion detection means. The combustion signal detection section setting unit 12 may be an analog circuit, but can also be executed by an in-vehicle computer such as a microcomputer.

  The combustion pressure detection circuit 21 processes the electrical signal from the combustion pressure sensor 22 to generate a combustion pressure signal, and outputs this combustion pressure signal to the combustion pressure detection circuit 21 as combustion detection means.

The combustion signal detection interval setting unit 12 sets a combustion pressure detection interval and a knock detection interval based on the combustion pressure signal output from the combustion pressure detection circuit 21.

The knock detection unit 13 filters the combustion pressure signal output from the combustion pressure detection circuit 21 to extract a vibration component caused by knock, and detects it in the knock detection section set by the combustion signal detection section setting unit 12. The occurrence of knocking is examined based on the vibration component. Note that the method for checking the presence / absence of knock occurrence is the same as in the first embodiment, and a description thereof will be omitted.

When the function executed by the combustion signal detection interval setting unit 12 is provided in the in-vehicle computer, the in-vehicle computer sets the combustion pressure detection interval and the knock detection interval according to the combustion detection interval setting routine shown in FIG. To do.

  This routine is executed at predetermined intervals. First, in step S21, the combustion pressure signal is monitored, and the process waits until the combustion pressure signal becomes equal to or higher than the start timing determination slice level. This start time determination slice level detects the start time of combustion, and is set in advance based on experiments or the like.

  Then, when the combustion pressure signal exceeds the start timing determination slice level, it is determined that combustion starts, and the process proceeds to step S22, and as shown in FIG. 7B, the start gate of the combustion pressure detection section (hereinafter referred to as "combustion pressure detection"). (Referred to as “start gate”).

  When the combustion pressure detection start gate is set, in step S23, the process waits until the combustion pressure signal shows a peak value. As a method for detecting the peak value of the combustion pressure signal, for example, the combustion pressure signal is sampled and weighted average every setting calculation, the current weighted average value is compared with the previous weighted average value, and the current weighted average is calculated. If it is lower than the previous weighted average and the state continues for a set period, it is determined as a peak.

  When the peak value of the combustion pressure signal is detected, the process proceeds to step S24, and a start gate of the knock detection section (hereinafter referred to as “knock detection start gate”) is set as shown in FIG. . It is known that the vibration component resulting from knocking is superimposed on the combustion pressure signal after showing a peak value. Therefore, by starting knock detection from the combustion pressure signal after detecting the peak value, it is possible to remove the noise component as much as possible.

  Next, the process proceeds to step S25, where the combustion pressure signal is compared with the preset end determination slice level, and the process waits until the combustion pressure signal is equal to or lower than the end determination slice level. When it is determined that the combustion pressure signal is equal to or lower than the end determination slice level, the process proceeds to step S26 to set a combustion pressure detection end gate and a knock detection end gate (see FIGS. 3 (e) and 3 (f)). Exit the routine.

  In this embodiment, as shown in FIG. 7A, the start time determination slice level and the end axis determination slice level are set to the same value, but both slice levels may be set to different values. good.

  As shown in FIG. 7E, the knock detection unit 13 checks the presence or absence of the occurrence of knock for each cylinder based on the vibration component extracted in the knock detection section. When a knock generation cylinder is detected, knock control such as retarding the ignition timing of the knock generation cylinder is performed in the next cycle to avoid knock generation.

  Thus, in this embodiment, since the knock detection start gate is set after detecting the peak value of the combustion pressure signal, for example, the combustion pressure sensor 22 is positioned close to the spark plug 4 (see FIG. 1). Even in an environment where discharge noise from the spark plug 4 is easily received, the S / N ratio of knock detection is improved, and high knock detection accuracy can be obtained.

  As a result, by performing knock control such as ignition timing control based on the vibration component detected in the knock detection section, knock can be effectively avoided without suppressing the engine output more than necessary, and the engine has The potential can be maximized.

Overall configuration diagram of the combustion detection zone setting device according to the first embodiment A flowchart showing a combustion detection interval setting routine (A) is a waveform diagram of a signal of an ignition transistor, (b) is a waveform diagram of a secondary current signal energized to a spark plug, (c) is a waveform diagram of a collector voltage, and (d) is a waveform diagram of an ion current signal. (E) is a waveform diagram of a signal for setting an ion current detection interval, (f) is a waveform diagram of a signal for setting a knock detection interval, and (g) is a waveform diagram of a knock current extracted in the knock detection interval. The flowchart showing the misfire determination routine Whole block diagram of combustion detection section setting device according to second embodiment A flowchart showing a combustion detection interval setting routine (A) is a waveform diagram of a combustion pressure signal, (b) is a waveform diagram of a signal for setting a combustion pressure detection interval, (c) is a waveform diagram of a signal for setting a knock detection interval, and (c) is a combustion pressure signal. Waveform diagram of vibration component caused by knock superimposed on signal, (e) is a waveform diagram of vibration component caused by knock extracted in the knock detection section

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ignition coil 1a Primary winding 1b Secondary winding 2 Battery 3 Ignition transistor 4 Spark plug 4a Center electrode 4b Outer electrode 11 Ion current detection circuit 12 Combustion detection section setting part 13 Knock detection part 21 Ion probe 21 Combustion pressure detection circuit 22 Combustion pressure sensor

Agent Patent Attorney Susumu Ito

Claims (3)

Combustion detection means for detecting the combustion state of the combustion chamber and outputting a combustion signal;
Combustion signal detection interval setting means for setting a start gate of the detection interval of the combustion signal when detecting the end of spark discharge of the ignition plug based on the collector voltage of the ignition transistor that switches the primary winding of the ignition coil;
After detecting the peak value of the combustion signal, a start gate of the knock detection section is set, the combustion signal is compared with the preset end determination slice level, and the combustion signal is determined to be equal to or lower than the end determination slice level. And a knock detection zone setting means for setting an end gate of the knock detection zone.   2. The combustion detection section setting device for an engine according to claim 1, wherein the combustion detection means is an ion current detection circuit that detects an ion current that changes according to ions interposed between a pair of electrodes.   2. The combustion detection interval setting device for an engine according to claim 1, wherein the combustion detection means is a combustion pressure detection circuit for detecting a combustion pressure signal output from a combustion pressure sensing means facing the combustion chamber. .

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