JP2004044495A - Ignition control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ignition control device for an internal combustion engine in which performance of fuel economy and output torque characteristic are improved by improving burning characteristics in low revolution including an idling period and a lean burning control area of a low load. <P>SOLUTION: In this ignition control device for the internal combustion engine to ignite the same cylinders twice (several times) in one burning cycle, one time (main ignition) among two or more ignition is executed at a first burning timing obtained based on a minimum ignition phase advance that the output torque of the internal combustion engine is maximized, and also at least the other one time (preignition) is executed at a second ignition timing preceding the first ignition timing at a crank angle. The preignition is executed not to ignite a fuel/air mixture in a combustion chamber. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ignition control device for an internal combustion engine in which the same cylinder is ignited a plurality of times in one combustion cycle.
[0002]
[Prior art]
2. Description of the Related Art Japanese Patent Application Laid-Open No. 7-103123 discloses a technique for performing a plurality of ignitions, i.e., multiple ignitions, in one combustion cycle for the same cylinder in an internal combustion engine. In this conventional technique, normal ignition is performed at an ignition timing set based on the minimum ignition advance angle, and subsequently, ignition is performed a plurality of times to increase the ignition rate, thereby improving the ignitability at the time of starting the internal combustion engine. We are trying to improve it.
[0003]
Further, in the above-described conventional technology, the energization time of a plurality of subsequent ignitions is set shorter than that of normal ignition, so that the energization time is suppressed from being lengthened and the reliability of the ignition system components is ensured. Make up.
[0004]
[Problems to be solved by the invention]
In the above-described prior art, the ignitability of the air-fuel mixture at the time of starting is improved by continuously igniting subsequent to the normal ignition. At low rotation speed and low load, lean burn control in which the air-fuel ratio is set to a leaner side than the stoichiometric air-fuel ratio is performed well.
[0005]
In the low-burn, low-load lean-burn control region including the idling time, the combustion characteristics are not always good, and thus it is difficult to sufficiently satisfy the fuel consumption performance and the dissatisfaction also remains in the output torque characteristics. Was something.
[0006]
However, the above-mentioned conventional technology only proposes a technology for improving the ignitability at the time of starting the internal combustion engine by performing continuous ignition, and the combustion characteristics in the low-speed, low-load, lean-burn control region including the idling time are reduced. It did not solve the improvement.
[0007]
Accordingly, an object of the present invention is to solve the above-mentioned problems and improve the combustion characteristics in a low-burn, low-load lean-burn control region including an idling state, thereby improving the fuel consumption performance and the output torque characteristics. To provide an ignition control device.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, according to the present invention, in the ignition control device for an internal combustion engine that ignites the same cylinder a plurality of times in one combustion cycle according to claim 1, one of the plurality of ignitions is A first ignition execution unit that executes at a first ignition timing obtained based on a minimum ignition advance at which an output torque of the internal combustion engine becomes maximum, and at least one other of the plurality of ignitions, It is configured to include a second ignition execution unit that executes at a second ignition timing preceding the first ignition timing by a crank angle.
[0009]
One of the plurality of ignitions is executed at a first ignition timing obtained based on a minimum ignition advance at which the output torque of the internal combustion engine is maximized, and at least another is performed at a first ignition timing higher than the first ignition timing. Is also configured to be performed at the second ignition timing preceding at the crank angle, so that the ignition performed at the second ignition timing is performed before the original ignition performed at the first ignition timing. As a result, the activation of the air-fuel mixture can be promoted, whereby the actual combustion period at the time of ignition can be shortened, the ignitability can be improved, and the combustion characteristics can be improved. Further, by promoting the activation of the air-fuel mixture, the in-cylinder pressure and isocapacity can be improved, and the output torque characteristics can be improved.
[0010]
In the second aspect, the second ignition execution means is configured to execute the at least one other ignition so as not to ignite the mixture in the combustion chamber of the internal combustion engine.
[0011]
Since another ignition is performed so as not to ignite the air-fuel mixture in the combustion chamber, the activation of the air-fuel mixture is further promoted before the actual ignition performed at the first ignition timing. Accordingly, the combustion period at the time of the original ignition can be shortened, the ignitability can be improved, and the combustion characteristics can be improved.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an ignition control device for an internal combustion engine according to one embodiment of the present invention will be described with reference to the accompanying drawings.
[0013]
FIG. 1 is a schematic diagram showing an entire ignition control device for an internal combustion engine according to the embodiment. FIG. 1 shows the internal combustion engine in a perspective view.
[0014]
In FIG. 1, reference numeral 10 denotes an OHC type internal combustion engine (hereinafter referred to as "engine"). The engine 10 includes four cylinders (cylinders) 12 arranged in series from a first cylinder to a fourth cylinder (only one cylinder is shown in FIG. 1). In the engine 10, air sucked from an air cleaner (not shown) flows through the intake manifold 16 while being metered by a throttle valve (not shown) housed inside the throttle body 14, and reaches the intake port 20.
[0015]
A fuel injection valve (injector) 22 is disposed near the intake port 20, and when opened, injects fuel (gasoline) pumped through a fuel pipe (not shown). The injected fuel mixes with the suctioned air, and the resulting mixture flows into the combustion chamber 26 when the intake valve 24 opens.
[0016]
FIG. 2 is an enlarged perspective view of the vicinity of the cylinder head of the engine 10. As shown in the drawing, the engine 10 includes a spark plug 30 i on the intake side at a position near the intake port 20 and exhaust gas at a position near the exhaust port 32. The ignition plug 30e is provided so that sufficient ignition performance (ignition performance) is obtained even when the engine 10 is controlled to perform lean burn control with a total of two ignition plugs.
[0017]
In this embodiment, as will be described later, ignition is performed twice (in other words, normal ignition (hereinafter referred to as “main ignition”) and ignition performed at a crank angle preceding the ignition (hereinafter referred to as “pre-ignition”). The ignition plug 30i on the intake side and the ignition plug 30e on the exhaust side simultaneously perform main ignition and pre-ignition.
[0018]
Returning to the description of FIG. 1, the air-fuel mixture in the combustion chamber 26 is simultaneously ignited by the two spark plugs 30i and 30e, ignited and burned by the main ignition, and drives the piston 34 downward in the figure. The drive of the piston 34 is converted into rotational motion by the crankshaft 36 and output.
[0019]
The rotation of the crankshaft 36 is transmitted to the camshaft 40 via the gear mechanism, and rotates the camshaft 40 by half the rotation of the crankshaft. The camshaft 40 opens and closes the intake valve 24 and the exhaust valve 42 (shown only in FIG. 2) via a valve mechanism. The exhaust gas generated by the combustion of the air-fuel mixture is discharged to the outside of the engine 10 through the exhaust manifold 44 and the exhaust pipe 46 when the exhaust valve 42 opens.
[0020]
A crank angle sensor 50 is disposed near the crankshaft 36. The cylinder discrimination signal is provided every 720 degrees of the crank angle. The TDC signal is provided at a predetermined crank angle near the TDC of the four cylinders. A crank angle signal is output for each predetermined crank angle.
[0021]
At an appropriate position downstream of the throttle body 14 and upstream of the intake manifold 16, an absolute pressure sensor 52 is disposed, which outputs a signal corresponding to the intake pipe absolute pressure PBA indicating the engine load and is housed inside the throttle body 14. A throttle opening sensor 54 is arranged near the throttle valve, and outputs a signal corresponding to the throttle valve position (throttle opening) TH.
[0022]
A coolant temperature sensor 60 is arranged in the coolant passage 56 of the cylinder to output a signal corresponding to the coolant temperature TW. A knock sensor 62 is arranged at an appropriate position of the cylinder. A signal indicating presence and intensity is output. Further, a wide area air-fuel ratio sensor 64 is disposed in the exhaust pipe, and outputs a value corresponding to the oxygen concentration in the exhaust gas.
[0023]
On the other hand, an ECU (electronic control unit) 70 is disposed at an appropriate position in an engine room of a vehicle (not shown) in which the engine 10 is mounted. The ECU 70 includes a microcomputer, and includes a CPU, a ROM, a RAM, an input / output circuit, a counter, and the like (all not shown). The output of the above-described sensor group is sent to the ECU 70. The ECU 70 counts the crank angle signal output from the crank angle sensor 50 to detect the engine speed NE. Other sensor outputs are stored in the RAM through appropriate processing.
[0024]
FIG. 3 is a block diagram showing input and output of the ECU 70. The above-mentioned sensor group is connected to the input side of the ECU 70, and the above-mentioned intake and exhaust side ignition plugs 30i, 30e are connected to the output side of the ECU 70 via ignition devices 72i, 72e. The ignition devices 72i and 72e have the same configuration, and each include a primary coil, a secondary coil, and an igniter for energizing / disconnecting the primary coil from a battery (not shown).
[0025]
In this embodiment, the ignition system has no distributor and has no distributor, and the ignition devices 72i and 72e are housed above the ignition plugs 30i and 30e as shown in FIG. 1 (only on the exhaust side). .
[0026]
Further, the fuel injection valve 22 is also connected to the output side of the ECU 70 via the drive circuit 74. The ECU 70 determines the fuel injection amount and the injection timing based on the sensor output, and drives the fuel injection valve 22 via the drive circuit 74 to open.
[0027]
FIG. 4 is a flowchart showing the operation of the ignition control device for an internal combustion engine according to this embodiment. The illustrated program is started by the TDC signal described above.
[0028]
In the following description, the engine speed NE, the intake pipe absolute pressure PBA, the throttle opening TH, the engine coolant temperature TW, etc. detected in S10 are read, and the program proceeds to S12 in which the detected engine speed NE is converted to the predetermined engine speed NEL. (For example, 2500 rpm) or less, and when affirmative, the process proceeds to S14, and it is determined whether or not the detected intake pipe absolute pressure PBA is equal to or less than a predetermined intake pipe absolute pressure PBAL (for example, a negative pressure equivalent to −367 mmHg). I do.
[0029]
If the result in S14 is also affirmative, the program proceeds to S16, in which it is determined that the engine speed NE is relatively low and the engine load (absolute pressure PBA in the intake pipe) is relatively low, that is, the engine is in the lean burn control region of low rotation and low load. An appropriately set map is retrieved from the detected engine speed NE and the intake pipe absolute pressure PBA to determine the pre-ignition ignition timing and energizing time.
[0030]
The ignition timing of the pre-ignition is determined, for example, between 90 degrees (between BTDC (before top dead center)) and 50 degrees, and the energization time is determined, for example, between 1.4 msec and 2.0 msec. More specifically, the energization time is determined to be longer as the engine speed NE and the intake pipe absolute pressure PBA are lower between 1.4 msec and 2.0 msec. Note that, as described later, even if the energization time is the maximum value of 2.0 msec, the mixture is set so as not to ignite in the pre-ignition.
[0031]
In this lean burn control region, the air-fuel ratio is controlled to a value on the lean side (for example, 16.0: 1 to 24.0: 1) compared to the stoichiometric air-fuel ratio. The lean burn control region also includes the idling state in which the throttle opening is fully closed (or in the vicinity thereof) and the engine speed NE decreases to about 700 rpm. When the result in S12 or S14 is NO, the process in S16 is skipped.
[0032]
Next, the program proceeds to S18, where the ignition timing and energizing time of the main ignition are calculated from the detected engine speed NE and the intake pipe absolute pressure PBA.
[0033]
Here, the main ignition means a normal ignition performed to ignite and burn the air-fuel mixture in the combustion chamber 26, and its ignition timing is determined by a minimum ignition advance (Minimum Advance) at which the output torque of the engine becomes maximum. The basic ignition timing, which is set as a map through an experiment so as to obtain “For Best Torque” and obtained from the engine speed NE and the absolute pressure PBA in the intake pipe, is advanced and retarded based on the coolant temperature TW, the presence or absence of knock, and the strength. This means a corrected ignition timing, that is, a so-called normal ignition timing (a first ignition timing obtained based on a minimum ignition advance at which the output torque of the engine becomes maximum).
[0034]
The ignition timing of the main ignition is determined, for example, from 10 degrees to 20 degrees BTDC during idling and from 20 degrees to 40 degrees BTDC in other lean burn control regions. When the vehicle is not in the lean burn control region including the idling time, for example, it is determined between 50 degrees BTDC and 15 degrees ATDC.
[0035]
The energization time means the time during which the primary coil must be energized to secure the ignition energy of the main ignition, and is similarly determined by searching a map from the engine speed NE and the intake pipe absolute pressure PBA. The energization time is specifically determined to be a value of 2.3 msec or more.
[0036]
When the order of ignition (combustion) of the engine 10 is the order of the first, third, fourth, and second cylinders, the ignition timing and the energization time calculated in S16 and S18 are as shown in the flowchart of FIG. Is the value for the next cylinder (in the order of ignition) of the cylinder corresponding to the TDC signal.
[0037]
FIG. 5 is a flow chart showing the operation of the ignition control device for the internal combustion engine according to this embodiment, and specific operations such as energization processing based on the ignition timing determined in the processing of the flow chart of FIG. It is a flowchart which shows. The illustrated program is started at a predetermined crank angle of BTDC.
[0038]
Prior to the description of FIG. 5, the ignition control according to the present embodiment will be briefly described with reference to the time chart of FIG. 6, in which the engine 10 performs one combustion cycle (intake, intake, It is ignited a plurality of times (twice) in compression, explosion, and exhaust strokes), and one of the plurality of times (two times) is executed at the ignition timing of the main ignition (first ignition timing). , At least one other of the multiple ignitions, more precisely, the other of the two ignitions, at the crank angle preceding the ignition timing of the main ignition (first ignition timing). The ignition timing is set to 2, for example, BTDC 90 degrees to 50 degrees. The ignition by the second ignition timing is referred to as “pre-ignition” as described above.
[0039]
Hereinafter, the processing of the flow chart of FIG. 5 will be described with reference to the time chart of FIG. 6. First, it is determined in S100 whether or not the energization start timing of the pre-ignition has come. If the determination is negative, the subsequent processing is skipped. At the same time, when the result is affirmative, the process proceeds to S102, in which the energization of each of the primary coils of the ignition devices 72i, 72e of the intake and exhaust-side ignition plugs 30i, 30e is started.
[0040]
Next, the program proceeds to S104, in which it is determined whether or not the ignition timing of the pre-ignition has arrived. If the result is negative, the subsequent processing is also skipped. To perform ignition (discharge). As described above, even if the energization time of the pre-ignition is determined to be the maximum value (2.0 msec), the mixture is not ignited (in other words, no flame kernel is formed).
[0041]
Next, the routine proceeds to S108, in which it is determined whether or not the main ignition start timing has come. In this case, a pre-ignition discharge time of 2.0 msec or more is secured in preparation for energization of the main ignition. Accordingly, when the pre-ignition and the main ignition approach each other due to the advance correction of the ignition timing of the main ignition and the pre-discharge time of 2.0 msec cannot be secured, the pre-ignition time is determined as shown by the imaginary line in FIG. The pre-ignition energizing time is reduced to advance the ignition timing.
[0042]
When the result in S108 is negative, the subsequent processing is similarly skipped, and when the result is affirmative, the process proceeds to S110, in which the primary coils of the ignition devices 72i, 72e of the intake and exhaust-side ignition plugs 30i, 30e are energized. Start. Then, the program proceeds to S112, in which the arrival of the ignition timing of the main ignition is confirmed, and the program proceeds to S114, in which the power supply to the primary coil is interrupted to perform ignition (discharge). By the main ignition, the air-fuel mixture in the combustion chamber 26 is ignited and burns.
[0043]
FIGS. 7 to 10 are data diagrams showing experimental results when the pre-ignition according to this embodiment is applied to an actual machine (the case where the pre-ignition according to this embodiment is not executed in FIGS. 7 to 9). (Shown by white circles).
[0044]
As the actual machine, a spark ignition type internal combustion engine having a displacement of 660 cc was used. The operating conditions were an engine speed of 1500 rpm, a load of 1.9 ps (−340 mmHg), and an air-fuel ratio of 22: 1.
[0045]
As is clear from FIGS. 7 and 8, when the pre-ignition according to this embodiment was performed, both the maximum in-cylinder pressure value Pmax and the isocapacity improved compared to the case where the pre-ignition was not performed. This improvement in the in-cylinder pressure maximum value Pmax is not due to the advance angle but to the improvement in combustion efficiency. As a result, as shown in FIG. 9, the BSFC (Brake
Specific Fuel Consumption also showed an average improvement of about 1%.
[0046]
As shown in FIG. 11, the "equal capacity" means the area (the area from the start to the end of the actual cycle combustion (shown by oblique lines)) / the area of the ideal cycle (enclosed by broken lines) in the acupressure diagram. Area) × 100 [%].
[0047]
Further, as shown in FIG. 10, the total combustion period was reduced by an average of 6 degrees at the crank angle. Mainly from the initial combustion period (ignition (IG) to 10% MBF (Mass
(Burned Fraction) was remarkably shortened, and improvement in ignitability was observed.
[0048]
The reason why the combustion characteristics are improved by the pre-ignition according to this embodiment is considered as follows. That is, when only one normal ignition (main ignition) is performed, the air-fuel mixture in the discharge path is activated by spark discharge between the plug electrodes and chemically reacts, and the flame nucleus is formed by a combined phenomenon of the chemical reaction and electric heating. Are formed, and combustion proceeds with the growth of the flame kernel.
[0049]
On the other hand, when performing the pre-ignition according to the present embodiment, the air-fuel mixture in the discharge path is activated by a spark discharge between the plug electrodes due to the pre-ignition, causing a chemical reaction. Next, by generating spark discharge between the plug electrodes by the main ignition, the activation and the chemical reaction are further promoted. Then, a flame nucleus is formed by a combined phenomenon of the promoted chemical reaction and electric heat, and combustion proceeds with the growth of the flame nucleus.
[0050]
It is considered that the activation is promoted by the pre-ignition, so that the combustion characteristics are improved. Specifically, it is considered that an electric field is applied to the air-fuel mixture by discharging sparks to such an extent that no flame nucleus is formed before the main ignition, thereby promoting the activation of the air-fuel mixture. It is thought that the promotion of this activation leads to improvement of ignitability at the time of main ignition (shortening of the initial combustion period) and improvement of the maximum value of the in-cylinder pressure and the equal capacity.
[0051]
In the ignition control according to the present embodiment, as described above, the main ignition is executed after performing the pre-ignition to such an extent that no ignition occurs. , The fuel consumption performance and the output torque characteristics can be improved.
[0052]
Further, the load condition when the fuel supply is restarted from the fuel supply stop (fuel cut) at the time of deceleration can be set to the low load side, and the fuel efficiency can be improved.
[0053]
Further, since the two spark plugs 30i and 30e are provided on the intake side and the exhaust side, sufficient ignition performance and ignition performance can be obtained even when the engine 10 is under lean burn control.
[0054]
As described above, this embodiment ignites the same cylinder 12 a plurality of times (specifically, twice) in one combustion cycle (consisting of four strokes of intake, compression, explosion, and exhaust) (engine 10). ), One of the multiple ignitions (main ignition) is executed at a first ignition timing obtained based on a minimum ignition advance at which the output torque of the internal combustion engine becomes maximum. The first ignition execution means (S108 to S114) and at least one of the plurality of ignitions (pre-ignition) are performed at a crank angle (to the front of the top dead center) with respect to the first ignition timing. A second ignition executing means (S100 to S106) for executing at the preceding second ignition timing is provided.
[0055]
The second ignition executing means is configured to execute the at least one other ignition so as not to ignite the air-fuel mixture in the combustion chamber 26 of the internal combustion engine.
[0056]
Although the embodiment of the present invention has been described by taking an engine that ignites twice in one combustion cycle for the same cylinder as an example, the present invention is not limited to this, and is equally applicable to an engine that ignites three or more times.
[0057]
Further, the embodiment of the present invention has been described by taking an engine having two spark plugs in one cylinder as an example. However, the present invention is not limited to this, and is applicable to an engine having only one spark plug in one cylinder. Is equally valid.
[0058]
Further, an engine having two ignition plugs in one cylinder will be described as an example, and ignition (main ignition and pre-ignition) by the two ignition plugs will be performed simultaneously. The ignition at the plug may be shifted in time with an appropriate phase difference.
[0059]
【The invention's effect】
According to the first aspect, one of the plurality of ignitions is executed at a first ignition timing obtained based on a minimum ignition advance angle at which the output torque of the internal combustion engine becomes maximum, and at least another ignition timing is obtained. Since the first ignition timing is performed at the second ignition timing preceding the first ignition timing by the crank angle, the second ignition timing is performed before the original ignition performed at the first ignition timing. It is possible to promote the activation of the air-fuel mixture, thereby shortening the combustion period at the time of the original ignition, improving the ignitability and improving the combustion characteristics. Can be improved. Further, by promoting the activation of the air-fuel mixture, the in-cylinder pressure and isocapacity can be improved, and the output torque characteristics can be improved.
[0060]
According to the second aspect of the present invention, another ignition is performed so as not to ignite the air-fuel mixture in the combustion chamber. Activation can be further promoted, whereby the actual combustion period at the time of ignition can be shortened, ignitability can be improved, and combustion characteristics can be improved.
[Brief description of the drawings]
FIG. 1 is an overall schematic diagram showing an ignition control device for an internal combustion engine according to one embodiment of the present invention.
FIG. 2 is an enlarged perspective view of the vicinity of a cylinder head of the engine shown in FIG.
FIG. 3 is a block diagram showing input and output of an ECU in the device shown in FIG. 1;
4 is a flowchart showing the operation of the ignition control device for an internal combustion engine shown in FIG. 1. FIG.
FIG. 5 is a flowchart showing the operation of the ignition control device for the internal combustion engine shown in FIG. 1;
FIG. 6 is a time chart showing the operation of the ignition control device for the internal combustion engine shown in FIGS. 4 and 5;
FIG. 7 is a data diagram showing experimental results when pre-ignition based on the operation of the apparatus shown in FIGS. 4 and 5 is applied to an actual machine.
8 is a data diagram showing an experimental result when preignition based on the operation of the apparatus shown in FIGS. 4 and 5 is similarly applied to an actual machine.
9 is a data diagram showing an experimental result when pre-ignition based on the operation of the apparatus shown in FIGS. 4 and 5 is similarly applied to an actual machine.
10 is a data diagram showing an experimental result when pre-ignition based on the operation of the apparatus shown in FIGS. 4 and 5 is similarly applied to an actual machine.
FIG. 11 is an explanatory diagram showing a definition of equal capacity shown in FIG. 8;
[Explanation of symbols]
10 Internal combustion engine (engine)
12 cylinder 26 combustion chamber 30 spark plug 50 crank angle sensor 52 absolute pressure sensor 70 ECU (electronic control unit)
72 Ignition device

Claims (2)

In an ignition control device for an internal combustion engine that ignites the same cylinder a plurality of times in one combustion cycle,
a. First ignition execution means for executing one of the plurality of ignitions at a first ignition timing obtained based on a minimum ignition advance at which the output torque of the internal combustion engine becomes maximum;
And b. Second ignition execution means for executing at least another one of the plurality of ignitions at a second ignition timing preceding the first ignition timing at a crank angle,
An ignition control device for an internal combustion engine, comprising: 2. The ignition control of an internal combustion engine according to claim 1, wherein the second ignition execution means executes the at least one other ignition so as not to ignite an air-fuel mixture in a combustion chamber of the internal combustion engine. apparatus.

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