JP2012036763A - Ignition control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ignition control device for an internal combustion engine capable of satisfying both of suppression of electrode wear and securement of ignitibility, regarding the ignition control device for the internal combustion engine.SOLUTION: The ignition control device for the internal combustion engine includes: an ignition means that ignites a fuel-air mixture by discharge; a discharge energy detection means that detects discharge energy supplied to the ignition means; a re-discharge determination means that determines occurrence of re-discharge when the discharge energy supplied to the ignition means is lower than the discharge energy after capacitative discharge at the start of discharge; and a discharge interruption means that interrupts the discharge energy supplied to the ignition means when the re-discharge is generated.

Description

  The present invention relates to an ignition control device for an internal combustion engine, and more particularly, to an ignition control device for an internal combustion engine provided with an ignition plug for spark ignition by discharge.

  2. Description of the Related Art Conventionally, as disclosed in Patent Document 1, for example, an internal combustion engine including an ignition plug that ignites an air-fuel mixture by spark discharge is known. Further, this publication discloses an ignition control device that calculates a spark ignition duration using a map with engine speed and engine load as parameters, and forcibly shuts off the spark discharge after the spark discharge duration has elapsed. Has been.

JP 2002-202040 A JP 2008-88947 A

  The inventors of the present application have conducted extensive research, and as a result, one of the main causes of electrode wear of the spark plug is re-discharge that does not contribute to ignitability in the latter half of the discharge (after the initial capacity discharge at the start of discharge, induction discharge is induced. It was found that there was a repetition of the capacity discharge that occurred and then regenerated again. In the above conventional ignition control device, since no consideration is given to this re-discharge, there is a concern about electrode consumption due to repeated re-discharge. Further, in the conventional ignition control device, the spark discharge duration time corresponding to the engine speed and the engine load is merely selected from the map. The spark discharge duration varies depending on individual differences in spark plugs and changes over time, and there may be cases where the ignitability is not sufficient. Therefore, it is not optimal from the viewpoint of electrode consumption and ignitability only by controlling the discharge according to the spark discharge duration.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide an ignition control device for an internal combustion engine capable of achieving both suppression of electrode wear and ensuring of ignitability.

In order to achieve the above object, a first invention is an ignition control device for an internal combustion engine,
Ignition means for igniting the mixture of the internal combustion engine by electric discharge;
Discharge energy detecting means for detecting discharge energy supplied to the ignition means;
Re-discharge determination means for determining that re-discharge occurs when the discharge energy supplied to the ignition means falls below a threshold value after the capacity discharge at the start of discharge;
And a discharge interruption means for cutting off discharge energy supplied to the ignition means when the re-discharge occurs.

The second invention is the first invention, wherein
Storage means for storing a necessary discharge period required for ignition for a plurality of operating states;
The discharge interruption means is characterized in that the discharge energy supplied to the ignition means is interrupted when the re-discharge occurs after the necessary discharge period according to an operating state has elapsed.

The third invention is the first or second invention, wherein
The discharge interruption means is
Charging means for charging ignition energy for generating discharge energy supplied to the ignition means, and charging the ignition energy by the charging means to cut off discharge energy supplied to the ignition means; Features.

According to a fourth invention, in any one of the first to third inventions,
The discharge shut-off means shuts off discharge energy supplied to the ignition means when the necessary discharge period elapses when the re-discharge occurs before the required discharge period elapses. .

The fifth invention is the third invention, wherein
The discharge interruption means is
Charging end determination means for determining whether or not the crank angle exceeds a predetermined angle in the latter half of the expansion stroke, and charging of the ignition energy by the charging means when the crank angle exceeds a predetermined angle in the latter half of the expansion stroke Charging termination means for terminating the charging.

  According to the first invention, after the capacity discharge at the start of discharge, when the discharge energy supplied to the ignition means falls below the threshold value, it is determined that re-discharge occurs, and the discharge energy supplied to the ignition means is Cut off. Therefore, it is possible to suppress the repetition of re-discharge that does not contribute to the ignitability in the latter half of the discharge, and it is possible to suppress electrode consumption due to the repetition of the re-discharge. In particular, since the supercharging region is a region where the charging efficiency is high, the re-discharge energy is large, and the electrode is consumed heavily, the electrode consumption in such a region can be effectively suppressed. Further, when re-discharge does not occur, a long discharge period can be ensured. For this reason, according to this invention, suppression of electrode consumption and ensuring of ignitability can be made compatible.

  According to the second invention, the discharge energy supplied to the ignition means is shut off when a re-discharge occurs after the elapse of the necessary discharge period according to the operating state. Therefore, it is possible to ensure a necessary discharge period according to the operating state. Furthermore, even after the elapse of the necessary discharge period according to the operating state, the discharge period can be ensured long until re-discharge occurs. As a result, even during lean combustion where high ignitability is required, a sufficient discharge period can be ensured, and the operating limit can be prevented from narrowing. For this reason, according to this invention, suppression of electrode consumption and ensuring of ignitability can be made compatible.

  According to the third aspect of the invention, the discharge energy supplied to the ignition means is cut off by charging the ignition energy that generates the discharge energy. For this reason, according to this invention, while being able to interrupt | block discharge energy suitably, it can charge in preparation for the next discharge.

  According to the fourth invention, when re-discharge occurs before the required discharge period elapses, the discharge energy supplied to the ignition means is cut off when the necessary discharge period elapses. For this reason, according to this invention, while being able to ensure a required discharge period, the repetition of the redischarge which generate | occur | produces after the period progress can be prevented beforehand.

  According to the fifth invention, when the crank angle exceeds the predetermined angle in the latter half of the expansion stroke, the charging of the ignition energy by the charging means is terminated. The latter half of the expansion stroke is a time when the in-cylinder pressure is reduced, and discharge and re-discharge are difficult to occur. Moreover, it is a time sufficient as a recharging period. For this reason, according to this invention, charging can be complete | finished, preventing a redischarge, and it can prepare for the next discharge.

It is a schematic block diagram for demonstrating the system configuration | structure of embodiment of this invention. FIG. 5 is a diagram for explaining re-discharge that occurs in the spark plug 12. It is a flowchart of the control routine which ECU50 performs in order to determine whether it is an area | region where electrode consumption with high redischarge energy is intense. It is a flowchart of the control routine which ECU50 and the apparatuses 34-40 perform in order to detect re-discharge and to start discharge interruption | blocking. It is the map which defined required discharge period (tau) _min corresponding to engine speed NE and charging efficiency KL. It is a flowchart of the control routine which ECU50 and apparatus 34-40 perform in order to interrupt | block discharge. It is a figure which shows the example of control of this embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.

Embodiment.
[System configuration]
FIG. 1 is a schematic configuration diagram for explaining a system configuration according to an embodiment of the present invention. The system shown in FIG. 1 includes an internal combustion engine (hereinafter simply referred to as an engine) 10. The engine 10 is a spark ignition type four-stroke engine having a spark plug 12 in each cylinder. Although only one cylinder is depicted in FIG. 1, the vehicle engine 10 generally has a plurality of cylinders. Each cylinder is provided with a fuel injection valve (not shown) that directly injects fuel into the cylinder. Note that the present invention is not limited to a cylinder injection internal combustion engine, but can be similarly applied to a port injection internal combustion engine that injects fuel into an intake port.

  Further, an intake passage 16 and an exhaust passage 18 are connected to each cylinder. An air cleaner 20 is provided near the inlet of the intake passage 16. An air flow meter 22 that outputs an intake air amount GA corresponding to the flow rate of fresh air taken into the intake passage 16 is attached downstream of the air cleaner 20.

  A supercharger 24 is provided downstream of the air flow meter 22. The supercharger 24 includes a compressor 24a and a turbine 24b. The compressor 24a and the turbine 24b are integrally connected by a connecting shaft. The compressor 24a is rotationally driven by the exhaust energy of the exhaust gas input to the turbine 24b.

  An intercooler (not shown) for cooling the fresh air compressed by the compressor 24a is provided downstream of the compressor 24a. A throttle valve 26 is provided downstream of the intercooler. The intake passage 16 downstream of the throttle valve 26 is branched and connected to each cylinder.

  The exhaust passage 18 is provided with a turbine 24b of the supercharger 24. Further, a catalyst (not shown) for purifying the exhaust gas is disposed downstream of the turbine 24b. As the catalyst, for example, a three-way catalyst is used.

  The system of this embodiment further includes an ECU (Electronic Control Unit) 50. In addition to the air flow meter 22 described above, various sensors such as a crank angle sensor 28 for detecting the crank angle CA are connected to the input unit of the ECU 50. Further, various actuators such as the ignition plug 12, the fuel injection valve, and the throttle valve 26 are connected to the output portion of the ECU 50. ECU50 controls the driving | running state of the engine 10 by operating various actuators according to a predetermined program based on the output of various sensors. The ECU 50 can calculate the engine speed NE and the charging efficiency KL based on the crank angle CA and the intake air amount GA.

[Discharge in spark plug]
As shown in FIG. 1, the spark plug 12 is attached to a cylinder head or the like of the engine 10 and is disposed in a state where the electrode portion is exposed in the combustion chamber 30. An ignition coil 32 that generates high-voltage discharge energy is connected to the spark plug 12. A plug discharge voltage measuring device 34 for measuring the discharge voltage of the spark plug 12 is connected to the ignition coil 32. A re-discharge determination device 36 is connected to the plug discharge voltage measuring device 34, and the discharge voltage measured by the plug discharge voltage measuring device 34 is input to the re-discharge determination device 36. A discharge interruption execution device 38 is connected to the redischarge determination device 36, and the determination result determined by the redischarge determination device 36 is input to the discharge interruption execution device 38. An input unit of the charge termination determination device 40 is connected to the output unit of the discharge interruption execution device 38. An input part of the ignition coil 32 is connected to the output part of the charging end determination device 40. In addition, a re-discharge determination device 36, a discharge interruption execution device 38 and a charge end determination device 40 are connected to the output portion of the ECU 50.

  In the system of the present embodiment, the spark plug 12 is provided with a center electrode and a ground electrode that are wrapped in an insulator penetrating the center of the plug with a gap (plug gap) therebetween. The spark plug 12 generates a spark between the electrodes by discharge to ignite the air-fuel mixture. Specifically, spark discharge is generated when the high voltage boosted by the ignition coil 32 breaks the insulation between the plug gaps in the highly compressed mixture. The spark discharge includes two components: a capacitive discharge that occurs first after the start of discharge in the vicinity of compression top dead center, and an induced discharge that occurs thereafter. The capacitive discharge is due to the discharge of electrostatic energy stored in the capacitor, and a large current flows in a short time. Inductive discharge is due to the release of electromagnetic energy stored in the coil, and a small current continuously flows for a long time compared to capacitive discharge.

  Note that an ignition circuit (a configuration including an ignition coil, a capacitor, a battery, a transistor, and the like) that generates spark discharge is a known circuit described in, for example, Japanese Patent Application Laid-Open No. 2002-202040. Description is omitted. Such an ignition circuit can interrupt discharge by charging of ignition energy (accumulation of charge in a capacitor, storage of electricity in a battery, etc.).

  By the way, since the electrode consumption by discharge arises in the spark plug 12, the suppression is desired. As a result of diligent research, the inventor of the present application has found that one of the main causes of electrode consumption is the repetition of re-discharge that does not contribute to the ignitability in the latter half of the discharge. Re-discharge refers to a phenomenon in which, after the first capacity discharge at the start of discharge, the process shifts to induction discharge, and then capacity discharge occurs again.

FIG. 2 is a diagram for explaining re-discharge that occurs in the spark plug 12. Spark discharge is started at time t0 near the compression top dead center. After the first capacity discharge, the discharge is continued by shifting to induction discharge. However, after that, at time t1 when the voltage falls below the threshold value V _thr , capacitive discharge occurs again (FIG. 2A). This capacitive discharge is re-discharge. As shown in FIG. 2, re-discharge occurs repeatedly thereafter. If re-discharge that occurs repeatedly is left unattended, there is a concern about deterioration of electrode consumption.

[Characteristic control in the embodiment]
Therefore, in the system of this embodiment, after the capacity discharge at the start of discharge, the discharge energy (discharge voltage) supplied to the spark plug 12 is detected at any time, and re-discharge occurs when the discharge energy falls below the threshold value V _thr. Then, it was determined that the discharge energy supplied to the spark plug 12 was cut off to suppress electrode consumption.

  In addition, the supercharging region is a region in which the charging efficiency KL is high and the re-discharge energy is large, and the electrode wear due to repeated re-discharge is severe. Therefore, suppression of electrode consumption in such a region is particularly required. On the other hand, if the discharge energy is lowered in order to reduce electrode consumption, there is a concern about deterioration in ignitability during lean combustion operation that requires high ignitability. Therefore, in the system of the present embodiment, suppression of electrode consumption in the supercharging region and securing of ignitability in lean combustion are also considered. Hereinafter, a control routine executed by the ECU 50 and the devices 34 to 40 in the system of the present embodiment will be described with reference to FIGS.

  FIG. 3 is a flowchart of a control routine executed by the ECU 50 in order to determine whether or not it is a region where the re-discharge energy is high and the electrode consumption is severe. In the routine shown in FIG. 2, it is determined whether or not the charging efficiency KL is higher than a predetermined value (step S100). According to the knowledge of the inventor, it is known that there is a correlation between the charging efficiency and the magnitude of the re-discharge energy. Therefore, as the predetermined value, a value indicating a region with high filling efficiency (about 80% as an example) is used. When the determination condition is satisfied, it is determined that the charging efficiency is high, such as a supercharging area, and the electrode is heavily consumed. In addition, when the charging efficiency KL is lower than a predetermined value, it is determined that the occurrence rate of re-discharge or the influence thereof is small. In this case, the processing after step S110 can be canceled to reduce the processing amount.

  FIG. 4 is a flowchart of a control routine executed by the ECU 50 and the devices 34 to 40 in order to detect re-discharge and start the discharge interruption. The routine shown in FIG. 4 is executed when the determination condition in step S100 is satisfied. First, when re-discharge is detected, the discharge voltage V is read (step S110). The discharge voltage V is a measured value measured by the plug discharge voltage measuring instrument 34. The plug discharge voltage measuring instrument 34 measures the discharge voltage of the ignition coil 32 as needed in the measurement section T before and after the start of discharge shown in FIG.

Next, after the first capacity discharge at the start of discharge, it is determined whether or not the discharge voltage V that has shifted to induction discharge is lower than the threshold value V _thr (step S120). Specifically, the discharge voltage V measured by the plug discharge voltage measuring instrument 34 is input to the re-discharge determination device 36, and the re-discharge determination device 36 compares it with the threshold value V _thr . The re-discharge determination device 36 stores in advance a voltage value that is likely to cause re-discharge as a threshold value V _thr . If the determination condition is not satisfied, the process returns to step S110. On the other hand, when the determination condition is satisfied, it is determined that re-discharge occurs.

Subsequently, it is determined whether or not the discharge period is sufficient for ignition. First, the re-discharge detection time _Tdis is read (step S130). The re-discharge detection timing _Tdis is the time from the start of discharge until the re-discharge is detected, and is the time when the discharge voltage V below the threshold V _thr is measured in step S120. The re-discharge determination device 36 reads the time when the discharge voltage V is measured from the plug discharge voltage measuring instrument 34 as the re-discharge detection time T _dis .

Further, the necessary discharge period τ _min is read (step S140). Specifically, the re-discharge determination device 36 stores a map that defines the required discharge period τ _min corresponding to the engine speed NE and the charging efficiency KL shown in FIG. The necessary discharge period τ _min is set in advance by experiments or the like according to the electrode shape of the spark plug 12. From this map, the necessary discharge period τ _min corresponding to the engine speed NE and the charging efficiency KL is read. The required discharge period τ _min may be further determined according to the fuel injection amount.

The re-discharge determination device 36 determines whether or not the re-discharge detection timing T _dis is after the required discharge period τ _min has elapsed (step S150). When re-discharge occurs after the necessary discharge period τ _min elapses, a signal for interrupting the subsequent discharge is input to the discharge interruption execution device 38 as a determination result (step S160). On the other hand, if the re-discharge occurs prior to the expiration required discharge period tau _min waits for elapse of the required discharge period tau _min, input as the determination result at the time of elapse, signal to shut off the discharge to the discharge cutoff execution unit 38 (Step S170).

  FIG. 6 is a flowchart of a control routine executed by the ECU 50 and the devices 34 to 40 in order to cut off the discharge. The routine shown in FIG. 6 is executed after the process of step S160 or S170. First, in order to cut off the discharge, a signal for starting charging is issued (step S180). Specifically, a signal for starting charging is output from the discharge interruption execution device 38 to the ignition circuit including the ignition coil 32 via the charging end determination device 40. As described above, the discharge of the ignition circuit of this embodiment is interrupted by charging of ignition energy.

  After the start of charging, the charging end determination device 40 sequentially reads the crank angle CA (step S190). The crank angle CA is sequentially detected by the ECU 50. Then, the charging end determination device 40 determines whether or not the crank angle CA exceeds a predetermined angle after the compression top dead center (step S200). As the predetermined angle, the charging end determination device 40 stores a sufficient time as a recharging period when the in-cylinder pressure is reduced and discharge is not cut off and redischarge is difficult to occur after the start of charging. For example, it is around 120 ° CA after the compression top dead center in the latter half of the expansion stroke. If the determination condition in step S200 is not satisfied, the process is resumed from step S190.

  On the other hand, when the determination condition of step S200 is satisfied, a signal for ending charging is output from the charging end determination device 40 to the ignition circuit including the ignition coil 32 (step S210). Thereafter, the processing of this routine is terminated.

As described above, according to the control routine of the present embodiment, when the discharge voltage V supplied to the spark plug 12 falls below the threshold value V _thr after the capacity discharge at the start of discharge, a re-discharge occurs. The discharge voltage V supplied to the spark plug 12 can be cut off. Therefore, it is possible to suppress the repetition of re-discharge that does not contribute to the ignitability in the latter half of the discharge, and it is possible to suppress electrode consumption due to the repetition of the re-discharge. In particular, electrode consumption can be effectively suppressed in a supercharging region where the charging efficiency is high and the electrode consumption due to re-discharge is severe.

Further, according to the control routine of the present embodiment, a long discharge period can be secured until re-discharge occurs even after the necessary discharge period τ _min has elapsed. Further, even if re-discharge occurs before the necessary discharge period τ _min elapses, the discharge period can be ensured until the elapse. As a result, it is possible to secure a sufficient discharge period, and it is possible to prevent the operating limit from being narrowed even during lean combustion that requires high ignitability.

  Further, according to the control routine of the present embodiment, the discharge voltage V supplied to the spark plug 12 is cut off by charging, and thereafter the charging is terminated when the crank angle CA exceeds a predetermined angle in the latter half of the expansion stroke. Can do. FIG. 7 is a diagram illustrating a control example of the present embodiment. As shown in FIG. 7, the voltage is increased by starting charging, and re-discharge after time t1 can be prevented. Further, the latter half of the expansion stroke is a time when the in-cylinder pressure is reduced, and it is difficult to cause discharge interruption and re-discharge, and is a time sufficient as a recharge period. For this reason, it is possible to prepare for the next discharge by terminating the charging while suppressing the re-discharge.

  Thus, according to the system of the present embodiment, it is possible to achieve both suppression of electrode consumption in the supercharging region and securing of ignitability in lean combustion.

  In the system of the above-described embodiment, the spark plug 12 has a plug gap between the center electrode and the ground electrode. However, the structure of the spark plug 12 is not limited to this. What is necessary is just to ignite the air-fuel mixture by spark discharge.

  Moreover, in the system of embodiment mentioned above, although the engine 10 is made into the supercharged engine provided with the supercharger 24, the engine 10 is not limited to this. An engine that does not have the supercharger 24 may be used.

  Moreover, in the system of embodiment mentioned above, although discharge energy is made into discharge voltage, discharge energy is not limited to this. For example, as shown in FIG. 6B, re-discharge may be detected using the discharge current as discharge energy.

Further, in the system of the above-described embodiment, the necessary discharge period τ _min is stored in the map (FIG. 5) corresponding to the operation state, but the present invention is not limited to this. For example, the necessary discharge period may be stored as a learned value, and learned according to detection of re-discharge.

  In the first embodiment described above, the spark plug 12 is used as the “ignition means” in the first invention, and the plug discharge voltage measuring device 34 is used as the “discharge energy detection means” in the first invention. The determination device 36 is the “re-discharge determination means” in the first invention and the “memory means” in the second invention, and the discharge cutoff execution device 38 is the “discharge cutoff means” in the first invention. The device 40 corresponds to the “charging end determination unit” in the fifth aspect of the invention.

  Here, the ECU 50 executes the process of step S110, so that the “discharge energy detecting means” in the first invention executes the process of step S120, and the When the “discharge determination means” executes the processes of steps S160 and S180, the “discharge cutoff means” in the first and second inventions causes the first and second steps to execute the processes of steps S170 and S180. The “discharge blocking means” in the fourth invention executes the process in step S180, and the “charging means” in the third invention executes the processes in steps S190 to S210. The “charging end means” in the present invention is realized.

KL Charging efficiency NE Engine speed T Measurement section T _dis Re-discharge detection timing V Discharge voltage V _thr threshold value τ _min Required discharge period 10 Engine 12 Spark plug 16 Intake passage 18 Exhaust passage 22 Air flow meters 24, 24a, 24b Supercharger, Compressor, turbine 28 Crank angle sensor 30 Combustion chamber 32 Ignition coil 34 Plug discharge voltage measuring device 36 Re-discharge determination device 38 Discharge interruption execution device 40 Charge end determination device 50 ECU

Claims (5)

Ignition means for igniting the mixture of the internal combustion engine by electric discharge;
Discharge energy detecting means for detecting discharge energy supplied to the ignition means;
Re-discharge determination means for determining that re-discharge occurs when the discharge energy supplied to the ignition means falls below a threshold value after the capacity discharge at the start of discharge;
A discharge shut-off means for shutting off discharge energy supplied to the ignition means when the re-discharge occurs;
An ignition control device for an internal combustion engine, comprising: Storage means for storing a necessary discharge period required for ignition for a plurality of operating states;
The discharge shut-off means shuts off discharge energy supplied to the ignition means when the re-discharge occurs after the elapse of the required discharge period according to the operating state;
The ignition control device for an internal combustion engine according to claim 1. The discharge interruption means is
Charging means for charging ignition energy for generating discharge energy supplied to the ignition means,
Cutting off the discharge energy supplied to the ignition means by charging the ignition energy by the charging means;
The ignition control device for an internal combustion engine according to claim 1 or 2, characterized by the above. The discharge shut-off means shuts off discharge energy supplied to the ignition means when the necessary discharge period elapses when the re-discharge occurs before the required discharge period elapses;
The ignition control device for an internal combustion engine according to any one of claims 1 to 3. The discharge interruption means is
Charging end determination means for determining whether or not the crank angle exceeds a predetermined angle in the latter half of the expansion stroke;
Charging end means for ending charging of the ignition energy by the charging means when the crank angle exceeds a predetermined angle in the latter half of the expansion stroke;
The ignition control device for an internal combustion engine according to claim 3, further comprising:

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