JP2005155546A - Ignition control device of engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ignition control device of an engine capable of avoiding reduction of the output while avoiding knocking. <P>SOLUTION: The ignition control device comprises a first ignition plug (14) and a second ignition plug (15) at a center of a combustion chamber (5) and outside the center of the combustion chamber (5), respectively, and further comprises a multi-point ignition temporary stop means (31) to temporarily stop the multi-point ignition when continuing the multi-point ignition using the plurality of ignition plugs (14 and 15) in a high load range. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ignition control device for an engine, and particularly to an apparatus that performs multipoint ignition.

For the purpose of improving the output while avoiding knocking, a first spark plug is arranged at the center of the combustion chamber, and a second spark plug is arranged at the center other than the center of the combustion chamber. There is what performs a fire (refer patent document 1).
Japanese Patent Laid-Open No. 2002-266739

  By the way, when the experiment of the technique of the above-mentioned patent document 1 was tried, it should have been to improve the output while avoiding knocking, but it was found that knocking occurs when the operation by multipoint ignition becomes longer in a high load region. It was.

  Even if knocking occurs in this manner, knocking control based on the knock sensor actually works, so that knocking can be avoided, but knocking is avoided by retarding the ignition timing. The engine output is reduced by the retarded ignition timing.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an apparatus that avoids a decrease in output while avoiding knocking.

  The present invention includes a first spark plug at the center of the combustion chamber, a second spark plug other than the center of the combustion chamber, and multipoint ignition using these multiple spark plugs in a high load range. The multi-point ignition is configured to be temporarily stopped.

  If multipoint ignition is continued in the high load region, knocking may occur. However, according to the present invention, multipoint ignition is temporarily stopped, so that the output is reduced while suppressing the occurrence of knocking in the high load region. It can be avoided.

  In addition, since the multipoint ignition can be continued in the high load region until the multipoint ignition is temporarily stopped, the output in the high load region can be improved.

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

  FIG. 1 is a schematic diagram for explaining the system of the present invention.

  After the air is stored in the intake collector, it is introduced into the combustion chamber 5 of each cylinder via the intake manifold. Fuel is injected and supplied from a fuel injector 21 disposed in the intake port 4 of each cylinder.

  Here, the three-way catalysts 9 and 10 provided in the exhaust passage 8 are harmful three components such as HC, CO, and NOx contained in the exhaust when the air-fuel ratio of the exhaust is in a narrow range (window) centering on the stoichiometric air-fuel ratio. Can be efficiently removed at the same time. Since the air-fuel ratio is the ratio of the intake air amount and the fuel amount, the intake air amount introduced into the combustion chamber 5 per one cycle of the engine (crank angle 720 ° section in a four-cycle engine) and the fuel injector 21 The engine controller 31 uses the intake air flow rate signal from the air flow meter 32 and the fuel from the fuel injector 21 based on the signals from the crank angle sensors (33, 34) so that the ratio to the fuel injection amount becomes the stoichiometric air-fuel ratio. The injection amount is set.

  The fuel injected into the air is vaporized and mixed with air to form a gas (air mixture) and flows into the combustion chamber 5. This air-fuel mixture is confined in the combustion chamber 5 when the two intake valves 16, 16 are closed, and is compressed by raising the piston 6.

  In order to ignite this compressed air-fuel mixture with a high-pressure spark, an ignition device 11 of an electronic power distribution system is provided in which an ignition coil with a built-in power transistor is arranged in each cylinder. In other words, the ignition device 11 includes an ignition coil 13 that stores electrical energy from the battery, a power transistor that energizes and shuts off the primary side of the ignition coil 13, and two ignition coils 13 by interrupting the primary current of the ignition coil 13. It consists of two spark plugs 14 and 15 that receive a high voltage generated on the next side and perform spark discharge.

  In this case, as shown in FIG. 2 (A), the main plug 14 (first spark plug) is biased to substantially the center position of the ceiling of the combustion chamber 5, and the sub plug 15 (second spark plug) is biased toward the intake side. It is provided at each position facing the combustion chamber 5. In FIG. 2A, the size of ● is different, but the specifications of the main plug 14 and the sub plug 15 are the same or similar. The number and position of the sub plugs 15 are not limited to this. For example, four sub plugs 15 may be equally arranged along the cylinder wall as shown in FIG.

  When a spark is blown off by the two spark plugs 14 and 15 slightly before the compression top dead center and the compressed air-fuel mixture in the combustion chamber 5 is ignited, the flame spreads and explosively burns, and the gas pressure due to this combustion is increased. The work of pushing down the piston 6 is performed. This work is taken out as the rotational force of the crankshaft 7. The combusted gas (exhaust gas) is discharged into the exhaust passage 8 when the two exhaust valves 17 and 17 are opened.

  In ignition, the sub plug 15 is ignited first, and then the main plug 14 is ignited. Thereby, the combustion speed of the air-fuel mixture in the combustion chamber 5 is increased, and the output of the engine can be increased. The main plug 14 and the sub plug 15 may be ignited simultaneously.

  The ignition timing at which the fuel consumption is optimal is determined as the basic ignition timing ADV0. The engine controller 31 calculates the basic ignition timing ADV0 according to the operating conditions (engine load and rotation speed), and the actual crank angle is the ignition timing. When it coincides with the timing ADV0, the ignition timing is controlled by cutting off the primary current of the spark plug 14 via the power transistor.

  On the other hand, since the engine controller 31 performs knock control based on the knock sensor 36 because knocking tends to occur in the high load low rotation speed region. Knock control using two spark plugs 14 and 15 is the same as knock control using only one spark plug 14. That is, when the knock intensity detected by the knock sensor 36 exceeds a predetermined value, the timing at which the basic ignition timing ADV0 [° BTDC] is retarded stepwise by a constant retardation amount RTD [°] is controlled by the control ignition timing QADV [ If the knock strength is within a predetermined value at this retarded angle, the ignition timing is controlled by giving a constant advance amount little by little, that is, gradually returning to the advance side. Ignition is performed with the ignition timing QADV. When the knock intensity again exceeds a predetermined value due to the advance of this ignition timing, ignition is performed with the control ignition timing QADV as the timing when the control ignition timing QADV at that time is retarded stepwise again by a certain delay amount RTD. If the knock magnitude falls within a predetermined value at this retarded angle, ignition is performed with the ignition timing that is gradually returned to the advance side as the control ignition timing QADV. Then repeat the above.

  FIG. 3 shows the measurement results of the location where knocking occurs and the timing IT when knocking occurs in an engine provided with a spark plug only at substantially the center position of the combustion chamber ceiling. In FIG. 3, the smaller the number attached to IT, the closer to the TDC, and the larger the number, the later the TDC. It can be seen from the figure that knocking has occurred from the heat spot near the intake valve. As described above, uniform flame propagation is not performed even at the center point ignition, but knocking generally occurs on the intake side, so a sub-plug is provided on the intake side as a countermeasure against knocking on the intake side. However, because the spark plug is biased toward the intake side, the combustion arrival time varies depending on the location, and by continuing the operation by multi-point ignition in the high load region, the combustion chamber 5 wall temperature is out of balance and knocking is reversed. Is likely to occur.

  In order to improve the state, in this embodiment, when the multipoint ignition in the high load region continues, the multipoint ignition is temporarily stopped.

  Specifically, FIG. 4 shows that when the engine load is increased at time t1 at a low rotational speed, the rotational speed is increased from time t2, and the load is decreased at time t3 during high load operation. It is a characteristic. In this case, the period during which the engine load exceeds the determination load is a high load region where knocking frequently occurs when multipoint ignition is continued. For this reason, in principle, multipoint ignition (hereinafter simply referred to as “multipoint ignition”) by the main plug 14 and the sub plug 15 is performed in a region other than the high load region where knocking does not occur, and the first condition in the high load region. In the second condition, the ignition by the sub-plug 15 is stopped and the one-point ignition only by the main plug 14 (hereinafter simply referred to as “one-point ignition”). Switch to

  Here, the first condition in the high load region in which the single point ignition is performed is the period B after the multipoint ignition is performed in the high load region for the period A. The second condition for performing the one-point ignition is when the temperature of the sub plug 15 exceeds the determination temperature. In the present embodiment, these two conditions are handled together, but only one of them may be handled.

  Referring to FIG. 4 in detail, multipoint ignition is performed only during period A from time t11 when entering the high load region, one point ignition is performed from time t12 when period A passes, and the period B ends is waited for. Multi-point ignition is performed again during the period A from time t13 when the period B passes.

  Since the sub-plug temperature has exceeded the determination temperature in the period from time t14 to time t15 before the period A has elapsed, one-point ignition is immediately performed in this period.

  The multipoint ignition is performed again from time t15, but the multipoint ignition is continued because the high load region is not reached after time t16.

  When the engine load returns to the high load range again at time t17, multipoint ignition is performed only during the period A, and switching to single point ignition is performed at time t18 when the period A passes.

  If the high load region is not reached at time t19 before the period B passes from time t18, multipoint ignition is performed.

  This control performed by the engine controller 31 will be described in detail with reference to the flowchart in FIG.

  FIG. 5 is for performing ignition control (multi-point ignition and single-point ignition) using two spark plugs 14 and 15, and is executed at regular intervals (for example, every 10 ms).

  In step 1, the engine load, the engine rotational speed N detected by the crank angle sensors (33, 34) (rotational speed detecting means), the water temperature Tw detected by the water temperature sensor 35 (water temperature detecting means), and the temperature sensor 37 (second sensor). The actual sub-plug temperature Ts detected by the means for detecting the temperature of the spark plug) is read.

  Here, as the engine load, for example, a basic injection pulse width Tp [ms] that is a basic value of the fuel injection amount or an intake air amount detected by the air flow meter 32 may be used.

  In step 2, the actual sub-plug temperature Ts is compared with the determination temperature TsH. Here, the determination temperature TsH is set based on the temperature at which pre-ignition occurs. Specifically, the determination temperature TsH may be a constant value. Here, pre-ignition means that the air-fuel mixture in the combustion chamber 5 is ignited by an ignition plug (here, the sub-plug 15) that is at a high temperature before being ignited by the ignition plug. When the sub-plug temperature Ts is equal to or higher than the determination temperature TsH, pre-ignition occurs due to the sub-plug 15, so the process proceeds to step 3 to perform one-point ignition. The sub-plug temperature Ts is not limited to that detected directly by the temperature sensor, but can be obtained by estimation.

  When the sub-plug temperature Ts is lower than the determination temperature TsH, it is determined that pre-ignition is not caused by the sub-plug 15, and the routine proceeds to step 4 to check whether or not the operating condition determined by the engine load and the rotational speed is in the knock control range. The knock control range is a high load low rotation speed range as shown in FIG.

  Here, the case where the operating condition is in the knock control region and the engine load continues in the high load region will be described first, and then the case where the operation condition is out of the knock control region or the high load region will be mentioned. Since the operating condition is in the knock control range, the process proceeds from step 4 to step 5 to compare the control ignition timing QADV [° BTDC] with the basic ignition timing ADV0 [° BTDC]. Here, the basic ignition timing ADV0 is an ignition timing at which MBT is obtained, and is given in advance as a map in accordance with operating conditions (engine load and rotational speed). When the control ignition timing QADV and the basic ignition timing ADV0 are equal, no knock has occurred, so the routine proceeds to step 11 where multipoint ignition is performed.

  When the control ignition timing QADV and the basic ignition timing ADV0 are not equal, the routine proceeds to step 6 where the engine load is compared with the determination load. Here, the determination load is a value that defines the boundary of a high load region where knocking frequently occurs, and is set as shown in FIG. That is, the determination load is a value that decreases as the engine speed decreases if the cooling water temperature Tw is the same. If the engine speed N is the same, the value becomes smaller as the cooling water temperature Tw becomes higher.

  Here, since the engine load is equal to or higher than the determination load, that is, in the high load range, it is determined that there is a possibility of knocking, and the process proceeds from step 6 to steps 7 and 8 to check the sub stop flag and the sub execution flag. Since both the sub stop flag and the sub execution flag are initially set to zero, the process proceeds to step 9 to start the first timer TM1 (TM1 = 0). The first timer TM1 is for measuring a period during which one-point ignition is continuously performed in a high load region.

  In step 10, after the sub execution flag = 1, the operation of step 11 is executed. With this sub-execution flag = 1, the process proceeds to step 12 from steps 7 and 8 from the next time.

  In step 12, the first timer value TM1 is incremented, and the first timer value TM1 after the increment is compared with the time A (first period). The time A determines the time for two-point ignition continuously in the high load range. When the first timer value TM1 is less than the time A, the routine proceeds to step 11 where multipoint ignition is performed.

  Eventually, when the first timer value TM1 becomes equal to or greater than the time A, the process proceeds from step 13 to step 14 to start the second timer TM2 (TM2 = 0). The second timer TM2 is for measuring a period during which one-point ignition is continuously performed in a high load region.

  In step 15, the sub-stop flag is set to 1, and then one-point ignition is performed in step 16. With this sub-stop flag = 1, the process proceeds from step 7 to step 17 from the next time.

  In step 17, the second timer value TM2 is incremented, and the incremented second timer value TM2 is compared with the time B (second period). The time B determines the time for which one-point ignition is continuously performed in the high load region. When the second timer value TM2 is less than the time B, the routine proceeds to step 16 where a one-point ignition is performed.

  Eventually, when the timer value TM2 becomes equal to or greater than the time B, the process proceeds from step 18 to steps 19 and 20, where the sub execution flag = 0 and the sub stop flag = 0. In step 21, multipoint ignition is performed again.

  Since the sub execution flag = 0 and the sub stop flag = 0, the process proceeds from step 7 to step 9 again from the next time, and the above is repeated.

  In this way, as long as the operating condition is in the knock control range and the engine load is in the high load range equal to or higher than the determination load, the multipoint ignition in period A and the single point ignition in period B are repeated.

  On the other hand, when the operating conditions change in the middle of the knock control range, it is outside the knock control range, or the control ignition timing does not match the basic ignition timing and the engine load changes from the high load range. When the load is lower than the load, the process proceeds from Steps 4 and 6 to Step 11 to immediately execute multipoint ignition.

  In this way, multipoint ignition and single point ignition are performed, but steps 11 and 21 in FIG. 5 are actually multipoint ignition execution flag = 1, and steps 3 and 16 in FIG. The multipoint ignition execution flag = 0. The multipoint ignition execution flag is viewed in a flow synchronized with an ignition timing (not shown). When this multipoint ignition execution flag = 1, multipoint ignition is executed, and conversely, when this multipoint ignition execution flag = 0. Stop the single point ignition.

  Here, the operation and effect of this embodiment will be described.

  FIG. 8 and FIG. 8 show how the ignition timing changes during the knock control when the engine speed is changed and the operating condition is shifted from the low load state to the throttle valve fully open state. 9 represents. Of these, FIG. 8 shows the characteristics in the case of continuous operation with multipoint ignition, and FIG. 9 shows the characteristics in the case of this embodiment.

  When multipoint ignition is performed continuously in a high load region, the ignition timing changes downward as shown in FIG. 8, that is, the ignition timing is gradually retarded as time elapses.

  On the other hand, in the present embodiment (the invention described in claim 2), in the period D (second period) after the multipoint ignition is performed in the period C (first period) as shown in FIG. Even if the ignition timing is shifted to the more advanced side than the period C because it is switched to the one-point ignition, and the ignition timing is returned to the multipoint ignition in the subsequent period E (first period), the ignition timing is the period C. (The previous first period). In the period of D, that is, in the case of single point ignition, the ignition timing shifts to the advance side than in the case of multipoint ignition because the combustion period is longer in single point ignition, so that the ignition timing can be advanced. is there.

  Here, FIG. 10 shows the full-open torque sensitivity at the time of multipoint ignition, and the torque increase rate increases by 1% every time the ignition timing is advanced by 1 °, that is, 1% strong torque at the ignition timing of 1 °. Represents an increase. For this reason, according to this embodiment (the invention described in claim 2), when the same ignition timing as the period C can be maintained when returning to the multipoint ignition in the period E, the multipoint ignition is continuously performed. The ignition timing can be advanced more than the case, and the engine torque can be improved accordingly. Note that the zero position on the horizontal axis in FIG. 10 is TDC, the right side is the advance side, and the left side is the retard side.

  Thus, according to the present embodiment (the invention described in claim 1), when multipoint ignition continues in a high load region, the multipoint ignition is temporarily stopped. It is possible to avoid a decrease in output while suppressing the occurrence of knocking in the region.

  According to this embodiment (the invention according to claim 3), when the temperature of the sub plug 15 (second ignition plug) becomes equal to or higher than the determination temperature TsH (set temperature), the multipoint ignition is immediately stopped. Since switching to single point ignition, preignition caused by the sub plug 15 can be suppressed.

  Since knocking is more likely to occur at a lower rotational speed even in a high load range, according to the present embodiment (the invention according to claim 5), the determination load is set to be smaller as the rotational speed N of the engine is lower ( 7), the determination load can be given with high accuracy regardless of the engine speed N.

  Since knocking is more likely to occur at higher water temperatures, according to the present embodiment (invention of claim 6), the determination load is set to be smaller as the cooling water temperature Tw becomes higher (see FIG. 7). Regardless of whether the determination load can be given with high accuracy.

  The fact that the ignition timing is not corrected to the retard side indicates that knocking has not occurred even in the high load range. Therefore, according to the present embodiment (the invention described in claim 7), the temporary stop of the multipoint ignition is prohibited when the ignition timing is not corrected to the retard side. Therefore (steps 5 and 11 in FIG. 5), this makes it possible to perform multipoint ignition at all times and improve fuel efficiency and torque.

The schematic block diagram of the engine of 1st Embodiment. The schematic block diagram which looked up at the combustion chamber of the engine from the bottom. The characteristic view which shows the knock generation | occurrence | production location and knock generation | occurrence | production time in the case of center one point ignition. The wave form diagram for demonstrating the ignition control of 1st Embodiment. The flowchart for demonstrating the ignition control of 1st Embodiment. The area | region figure of a knock control area. The characteristic figure of judgment load. The wave form diagram which shows the change of the ignition timing during knock control in 2 point | piece ignition continuous operation. The wave form diagram which shows the change of the ignition timing during knock control of 1st Embodiment. The characteristic diagram of the ignition timing sensitivity of the two-point ignition full open torque.

Explanation of symbols

14 Main plug (first spark plug)
15 Sub plug (second spark plug)
21 Fuel injection valve 31 Engine controller 33, 34 Crank angle sensor (rotational speed detection means)
35 Water temperature sensor (water temperature detection means)
37 Sub plug temperature sensor (means for detecting the temperature of the second spark plug)

Claims (7)

A first spark plug is provided at the center of the combustion chamber, and a second spark plug is provided at the center other than the center of the combustion chamber.
An ignition control device for an engine, comprising multipoint ignition temporary stop means for temporarily stopping the multipoint ignition when multipoint ignition using the plurality of spark plugs continues in a high load range. . The multipoint ignition temporary stop means is
Means for performing multi-point ignition using the plurality of spark plugs during a first period;
Means for stopping ignition by the second spark plug for a second period after the end of the first period and performing ignition only by the first spark plug;
2. The engine ignition control device according to claim 1, comprising means for repeating multipoint ignition in the first period and ignition by only the first spark plug in the second period. Means for estimating or detecting the temperature of the second spark plug;
3. The engine ignition control device according to claim 1, wherein when the temperature of the second ignition plug becomes equal to or higher than a set temperature, the multipoint ignition is immediately stopped.   2. The engine ignition control device according to claim 1, wherein the high load region is a case where an engine load is equal to or higher than a determination load. A rotation speed detecting means for detecting the rotation speed of the engine;
5. The engine ignition control device according to claim 4, wherein the determination load is set to be smaller as the detected rotation speed of the engine is lower. Equipped with water temperature detecting means for detecting the cooling water temperature of the engine,
5. The engine ignition control device according to claim 4, wherein the determination load is set to be smaller as the detected coolant temperature of the engine becomes higher. Means for calculating a basic ignition timing giving MBT;
Means for determining whether knocking has occurred based on a knock sensor;
Means for setting, as a control ignition timing, a value obtained by correcting the basic ignition timing to the retard side when knocking occurs from the determination result;
2. The engine ignition control device according to claim 1, wherein when the ignition timing is not corrected to the retarded angle side, temporary stop of the multipoint ignition is prohibited.

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