JP2004263612A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine, which realizes improvement of a combustion condition and reduction of fuel consumption. <P>SOLUTION: In the engine 10, an ignition plug 27 is applied with high voltage from an ignitor 28, and a discharge spark is generated between opposing electrodes of the plug. This causes fuel introduced in a cylinder to be provided for combustion. An ECU 40 comprises a means for adjustably setting, after starting of discharge at ignition timing, time duration of the discharge. The ECU 40 detects a combustion condition of the engine 10 and extends the discharge time duration by the ignition plug 27 when combustion deterioration is detected. This facilitates temperature rise near the opposing electrodes of the plug 27, and ignitability is improved. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a control device for an internal combustion engine.
[0002]
[Prior art]
In a spark ignition type internal combustion engine, a high voltage is applied to an ignition plug from an ignition device including an ignition coil and the like, and accordingly, a discharge spark is generated between opposed electrodes of the ignition plug. Then, the fuel introduced into the combustion chamber is burned by the generation of the discharge spark. In such a case, it has been pointed out that if the temperature near the electrode of the spark plug is low, the ignitability of the fuel is reduced and the combustion stability is impaired.
[0003]
Therefore, conventionally, it has been studied to heat intake air or lubricating oil and to improve combustion stability by increasing the amount of heat. However, in an actual internal combustion engine, it is necessary to move instantaneously in all operation ranges from low-speed light load to high-speed high load in addition to steady-state operation. there were.
[0004]
Further, as a combustion improvement technique, a so-called multiple discharge technique has been proposed in which a plurality of discharges are intermittently repeated within one combustion stroke. For example, in the technique of Patent Document 1, in an internal combustion engine that performs multiple discharges, the discharge interval is shortened when the gas flow in the combustion chamber is increased, thereby limiting the discharge path and improving the ignitability. I was trying to plan.
[0005]
[Patent Document 1]
Japanese Patent No. 2744256
[0006]
[Problems to be solved by the invention]
However, in Patent Literature 1, when the temperature near the electrode of the ignition plug is low and initial ignition becomes unstable, the combustion state may be deteriorated, and sufficient combustion improvement measures have not been taken. In particular, in an operation state of extremely low rotation and no load (idle), the temperature near the plug electrode before ignition is low, and there is a possibility that combustion may be deteriorated. If the combustion deteriorates, there is a possibility that the exhaust emission deteriorates and the fuel efficiency deteriorates. Therefore, appropriate measures for improving the combustion are desired.
[0007]
In recent years, in order to reduce pumping loss and improve mixing of the air-fuel mixture, the opening and closing operation conditions of the intake valve have been adjusted by applying a variable valve mechanism to reduce the lift amount of the intake valve and advance the closing timing. In some cases, the actual compression ratio is reduced because the intake air amount is limited. Further, the reduction of various losses reduces the required torque at the same output, which also contributes to the reduction of the actual compression ratio. It is also known that the decrease in the actual compression ratio lowers the temperature near the electrode of the ignition plug and deteriorates combustion stability.
[0008]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a control device for an internal combustion engine that can improve a combustion state and reduce fuel consumption.
[0009]
[Means for Solving the Problems]
According to the first aspect of the invention, there is provided an ignition control means for controlling the ignition timing of the ignition plug, and a combustion state detection means for detecting a combustion state of the internal combustion engine, wherein the ignition control means discharges at the ignition timing. Means for variably setting the duration of the discharge after the start, wherein the duration of the discharge is extended when deterioration of combustion is detected by the combustion state detecting means.
[0010]
In short, by extending the duration of the discharge after the start of discharge by the spark plug, a temperature rise is promoted near the counter electrode of the spark plug. In this case, the temperature of the vicinity of the opposite electrode of the ignition plug surely rises to a temperature at which ignition is possible, so that the combustion reaction is activated and the flame nucleus is favorably formed. As a result, even if the combustion state is deteriorated, the ignitability is improved, and the improvement of the combustion state and the reduction of fuel consumption can be realized.
[0011]
As a method of extending the discharge, the duration of the discharge may be variably set according to the in-cylinder temperature. Instead of the in-cylinder temperature, the temperature near the electrode of the spark plug may be used. Specifically, the lower the in-cylinder temperature (the temperature near the electrode), the longer the duration of the discharge. Alternatively, the duration of the discharge may be variably set according to the state of the gas flow in the cylinder. Specifically, the longer the gas flow in the cylinder, the longer the duration of the discharge.
[0012]
According to the fourth aspect of the present invention, the extension of the duration of the discharge is limited. In this case, it is possible to prevent the duration of the discharge from being unnecessarily extended, and it is possible to suppress the energy consumption and prevent the plug electrode from being worn.
[0013]
According to a fifth aspect of the present invention, the ignition control means further comprises means for intermittently and repeatedly executing discharge by the spark plug for one combustion stroke, and the first discharge in which the duration of discharge is extended is performed. Subsequently, a second discharge in which the discharge is repeated in small increments is performed. According to the fifth aspect, the temperature in the vicinity of the electrode of the spark plug is maintained by repeatedly performing the small discharge. Thereby, diffusion combustion is promoted. That is, by performing the second discharge subsequent to the first discharge, formation of a flame nucleus and promotion of diffusion combustion can be realized, and the combustion state can be more appropriately improved.
[0014]
As described in claim 6, the ignition control means may variably set the implementation period of the second discharge in accordance with the state of the in-cylinder gas flow, and more specifically, the stronger the in-cylinder gas flow, Extend the implementation period of the second discharge. Here, variably setting the execution period of the second discharge also means variably setting the number of repetitions of the discharge, and extending the execution period of the second discharge also means increasing the number of repetitions of the discharge.
[0015]
According to the seventh aspect of the present invention, the ignition mode consisting of only the first discharge or the ignition mode consisting of the first discharge and the second discharge is selectively executed according to the operating state of the internal combustion engine each time. In other words, when the combustion state is deteriorating, it is desirable to carry out both the first discharge and the second discharge from the viewpoint of combustion improvement, but from the viewpoint of suppressing energy consumption and preventing wear of the plug electrode. It is desirable that the discharge is small. If the ignition mode is selected according to the operating state of the internal combustion engine as described above, the effects of suppressing energy consumption and preventing the wear of the plug electrode can be obtained in a well-balanced manner in addition to the combustion improving effect. It should be noted that each of the ignition modes may be selected according to the degree of combustion deterioration. If combustion improvement is relatively easy, an ignition mode consisting of only the first discharge is selected. (In other words, if the combustion cannot be improved only by the first discharge), an ignition mode including the first discharge and the second discharge is selected.
[0016]
The ignition device stores electric energy for generating a discharge spark every time of ignition and applies a high voltage to the ignition plug by discharging the electric energy. In the ignition system including the ignition device, as set forth in claim 8, it is preferable that the ignition control means increases the electric energy stored in the ignition device in advance corresponding to the extension of the duration of the discharge. . Thereby, sufficient discharge energy for extending the duration of discharge can be secured.
[0017]
When the duration of the discharge is extended, the combustion reaction is activated, so that the combustion speed is increased as compared with the case where the discharge is not extended. That is, after the start of the discharge at the ignition timing, the peak point of the output torque is quickly reached. In this case, the ignition control means may retard the ignition timing when extending the duration of the discharge. Thus, even if the discharge is extended, a desired output torque can be obtained at the optimal time. It is desirable that the ignition retard amount is set according to the length of the discharge continuation time (the extent of the discharge extension).
[0018]
On the other hand, the invention according to claim 10 includes ignition control means for controlling the ignition timing of the ignition plug, and the ignition control means extends the duration of the discharge immediately after the start of the discharge to increase the temperature near the electrode. Following the first combustion improving means and the second combustion improving means, a second step of intermittently and repeatedly performing discharge by the ignition plug for one combustion stroke in order to maintain the temperature near the electrode after the temperature rise. And combustion improvement means.
[0019]
According to the tenth aspect, by increasing the duration of the discharge immediately after the start of the discharge by the ignition plug, a temperature rise is promoted near the counter electrode of the ignition plug, and further, by repeating the discharge thereafter, The temperature near the electrode of the spark plug is maintained. As a result, the formation of a flame nucleus and the promotion of diffusion combustion can be realized, so that the combustion state can be improved and the fuel consumption can be reduced.
[0020]
In the invention of claim 10, the inventions of claims 2 to 4, claim 6, claim 8, and claim 9 can be applied. That is,
The duration of discharge in the first combustion improvement means is variably set according to the in-cylinder temperature (temperature near the electrode).
The duration of the discharge in the first combustion improvement means is variably set according to the state of the gas flow in the cylinder.
-To limit the extension of the duration of discharge in the first combustion improvement means.
-The execution period of the repeated discharge in the second combustion improving means is variably set according to the state of the gas flow in the cylinder.
Increasing the electrical energy pre-stored in the igniter corresponding to the extension of the duration of the discharge.
-To prolong the duration of discharge, retard the ignition timing.
Can be applied.
[0021]
The invention according to claim 11, further comprising a combustion state detecting means for detecting a combustion state of the internal combustion engine, wherein when the combustion state detecting means detects deterioration of the combustion, the ignition control means performs the first combustion. The combustion is improved by the improvement means and the second combustion improvement means. Thereby, when the combustion state is deteriorating, it is possible to suitably realize the combustion improvement. Further, since combustion improvement is performed only when necessary due to deterioration of combustion, it is possible to suppress energy consumption and prevent wear of the plug electrode.
[0022]
According to the twelfth aspect of the present invention, the ignition control means implements only the first combustion improvement means or the first combustion improvement means and the second combustion improvement means depending on the operation state of the internal combustion engine at each time. Choose to implement both improvement measures. In other words, if each combustion improvement means is selectively executed according to the operating state of the internal combustion engine, in addition to the combustion improvement effect, effects such as suppression of energy consumption and prevention of wear of the plug electrode can be obtained in a well-balanced manner. It should be noted that each of the combustion improvement means may be selectively performed according to the degree of combustion deterioration. If the combustion improvement is relatively easy, only the first combustion improvement means is selected and performed, and the combustion improvement is compared. If it is difficult (that is, if the combustion cannot be improved only by the first combustion improving means), the first combustion improving means and the second combustion improving means are selected and executed.
[0023]
According to a thirteenth aspect of the present invention, the combustion state detecting means calculates a rotation fluctuation amount of the internal combustion engine, and detects a combustion state based on the rotation fluctuation amount. When the combustion deteriorates, the rotation fluctuation occurs, so that the deterioration of the combustion can be accurately detected. According to the thirteenth aspect, combustion deterioration is appropriately detected, and the combustion improvement processing such as discharge extension and repeated discharge (multiple discharge) can be appropriately performed.
[0024]
According to a fourteenth aspect of the present invention, the combustion state detecting means calculates a pressure fluctuation amount in a combustion chamber of the internal combustion engine, and detects a combustion state based on the pressure fluctuation amount. Since in-cylinder pressure fluctuations occur at the time of combustion deterioration, combustion deterioration can be accurately detected. According to the fourteenth aspect, deterioration of combustion is appropriately detected, and combustion improvement processing such as discharge extension and repeated discharge (multiple discharge) can be appropriately performed.
[0025]
The invention according to claim 15 includes, in place of the combustion state detecting means, means for defining combustion state data for each operating region of the internal combustion engine and estimating a combustion state using the combustion state data, When the deterioration is estimated, a process for improving the combustion is performed. In this case, if it is estimated from the operating state of the internal combustion engine that combustion deterioration will occur, combustion improvement processing such as discharge extension and repeated discharge (multiple discharge) is performed. Therefore, the combustion improvement processing can be performed promptly with respect to the deterioration of the combustion or before the actual deterioration of the combustion.
[0026]
In recent years, an internal combustion engine having a variable valve mechanism for variably adjusting the opening / closing operation conditions (a lift amount, a valve opening timing, and the like) of an intake valve to control an intake air amount has been put into practical use. In this case, the opening / closing operation condition of the intake valve is set in the direction of limiting the intake air amount, and the variable valve mechanism is controlled. In such a case, the combustion state becomes unstable due to a decrease in the actual compression ratio or the like, which may cause deterioration of combustion. However, as described in claim 16, combustion such as discharge extension and repetitive discharge (multiple discharge) occurs. By applying the improvement process to the variable valve mechanism of the intake valve, combustion improvement can be realized even in a region where the combustion state becomes unstable due to a decrease in the actual compression ratio or the like.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described below with reference to the drawings. In the present embodiment, an engine control system is constructed for an in-vehicle multi-cylinder gasoline engine which is an internal combustion engine. In this control system, an electronic control unit (hereinafter referred to as an ECU) is used as a center to control a fuel injection amount. And control of ignition timing and the like. First, an overall schematic configuration diagram of the engine control system will be described with reference to FIG.
[0028]
In the engine 10 shown in FIG. 1, an air cleaner 12 is provided at the most upstream portion of the intake pipe 11, and an air flow meter 13 for detecting an intake air amount is provided downstream of the air cleaner 12. Downstream of the air flow meter 13, a throttle valve 14 whose opening is adjusted by an actuator such as a DC motor and a throttle opening sensor 15 for detecting the throttle opening are provided. A surge tank 16 is provided downstream of the throttle valve 14, and the surge tank 16 is provided with an intake pipe pressure sensor 17 for detecting an intake pipe pressure. An intake manifold 18 for introducing air into each cylinder of the engine 10 is connected to the surge tank 16, and an electromagnetically driven fuel injection that injects fuel near the intake port of each cylinder in the intake manifold 18. A valve 19 is mounted.
[0029]
An intake valve 21 and an exhaust valve 22 are provided at an intake port and an exhaust port of the engine 10, respectively. When the intake valve 21 is opened, a mixture of air and fuel is introduced into the combustion chamber 23. The exhausted gas after combustion is discharged to the exhaust pipe 24 by the opening operation of. The intake valve 21 and the exhaust valve 22 are provided with variable valve mechanisms 25 and 26, respectively. These variable valve mechanisms 25 and 26 have a structure in which the valve opening / closing operation conditions such as the lift amount and the valve opening timing of each valve 21 and 22 can be continuously varied. Valve opening / closing operation conditions are appropriately adjusted according to the engine operating state and the like. In such a case, in particular, according to the variable valve mechanism 25 on the intake side, the amount of intake air into the combustion chamber 23 can be directly controlled at the intake port (intake inlet). Therefore, by performing the intake air amount control by the variable valve mechanism 25, there is no delay in the response of the intake system from the throttle valve to the combustion chamber as compared with the conventional intake air amount control by the throttle valve. Responsiveness is improved. Further, since there is no need to restrict the intake passage with a throttle valve, pumping loss can be reduced and fuel efficiency can be improved. A detailed configuration example of the variable valve mechanisms 25 and 26 will be described later.
[0030]
As described above, in the present control system, the intake air amount control is basically performed by the variable valve mechanism 25, and the intake air amount control is not performed by the throttle valve 14. The air amount control is performed. Further, when discharging the fuel vapor (evaporative gas) generated in the fuel tank to the intake system, it is necessary to generate a slight negative pressure in the intake pipe 11. For this reason, the throttle valve 14 is also provided.
[0031]
An ignition plug 27 is attached to a cylinder head of the engine 11 for each cylinder, and a high voltage is applied to the ignition plug 27 at a desired ignition timing through an ignition device 28 including an ignition coil and the like. By the application of the high voltage, a spark discharge is generated between the opposing electrodes of each ignition plug 27, and the air-fuel mixture introduced into the combustion chamber 23 is ignited and used for combustion.
[0032]
The exhaust pipe 24 is provided with a catalyst 31, such as a three-way catalyst, for purifying CO, HC, NOx and the like in the exhaust gas. Alternatively, an air-fuel ratio sensor 32 (linear air-fuel ratio sensor, oxygen sensor, etc.) for detecting rich / lean is provided. The cylinder block of the engine 10 includes a cooling water temperature sensor 33 for detecting a cooling water temperature and a crank angle sensor 34 for outputting a rectangular crank angle signal at every predetermined crank angle of the engine (for example, at a cycle of 30 ° CA). Installed.
[0033]
The outputs of the various sensors described above are input to the ECU 40 that controls the engine. The ECU 40 mainly includes a microcomputer including a CPU, a ROM, a RAM, and the like. By executing various control programs stored in the ROM, the ECU 40 controls the fuel injection amount and the ignition amount of the fuel injection valve 19 according to the engine operating state. The ignition timing by the plug 27 is controlled.
[0034]
Here, the configuration of the intake-side variable valve mechanism 25 will be described with reference to FIG. Note that the variable valve mechanism 26 on the exhaust side is substantially the same as the variable valve mechanism 25 on the intake side, and a description thereof will be omitted.
[0035]
As shown in FIG. 2, the upper end of the intake valve 21 is in contact with the swing arm 51, and the intake valve 21 performs a lifting operation in the vertical direction in the figure as the swing arm 51 swings. A roller 52 is provided substantially at the center of the swing arm 51, and a link arm 53 is provided vertically above the swing arm 51 so as to be in contact with the outer peripheral surface of the roller 52. The link arm 53 is supported by a control shaft 55 integrally provided with an eccentric cam 56, and swings in the left and right direction in the figure according to the rotation of the cam shaft 57. That is, the roller 54 is provided substantially at the center of the link arm 53, and the outer peripheral surface of the roller 54 is in contact with the cam 58 provided on the cam shaft 57. The link arm 53 is urged by a return spring (not shown) so that the roller 54 is held in a state in which the roller 54 contacts the cam 58. In this case, when the camshaft 57 rotates, the link arm 53 swings right and left following the outer peripheral surface shape (cam profile) of the cam 58. Here, at the lower end of the link arm 53, a pressing portion 53a is provided which is apart from the swing arm 51 in normal times and which comes into contact with and presses the swing arm 51 when the link arm 53 swings. When the swing 53 is performed, the swing arm 51 is pressed by the pressing portion 53a. As a result, the swing arm 51 swings up and down, and accordingly, the intake valve 21 lifts to the open side.
[0036]
Further, the control shaft 55 is provided with a small angle of rotation by an actuator (not shown) such as a stepping motor. When the control shaft 55 is given a rotation, the eccentric cam 56 is integrally formed. It rotates, and the support point of the link arm 53 moves little by little. At this time, when the support point of the link arm 53 moves, the swing position of the link arm 53 changes, and as a result, the amount of pressing of the swing arm 51 changes and the amount of valve lift changes.
[0037]
Specifically, for example, when the control shaft 55 is rotated together with the eccentric cam 56 in the clockwise direction in the figure, the upper end of the link arm 53 is pushed rightward by the eccentric cam 56, and the pressing portion 53a of the link arm 53 is pushed. It moves so as to approach the swing arm 51. When the camshaft 57 rotates in this state, the pressing amount of the swing arm 51 increases, the lift amount of the intake valve 21 increases, and the pressing period of the swing arm 51 increases, and the valve opening period of the intake valve 21 increases. Become.
[0038]
Since the rotation angle position of the control shaft 55 can be linearly adjusted by a stepping motor or the like, the valve opening and closing operation conditions such as the lift amount of the intake valve 21 and the valve opening period are continuously variable by precisely controlling the rotation angle position. It can be. At this time, the rotation angle position of the control shaft 55 is controlled by the ECU 40 according to the accelerator opening degree, the engine operating state, and the like at each time.
[0039]
In the present control system, the ECU 40 implements “combustion state detection means” and “ignition control means”. In particular, the ignition control means extends the duration of discharge after the start of discharge at ignition timing. The "first discharge" and the "second discharge" that is repeated intermittently for one combustion stroke following the first discharge are performed. In the following description, the second discharge is also referred to as a multiple discharge. The first discharge is performed for the purpose of increasing the temperature near the electrode, and this corresponds to “first combustion improvement means”. The second discharge is performed for the purpose of maintaining the temperature near the electrode after the temperature rise, and this corresponds to “second combustion improvement means”. FIG. 3 shows a configuration of an ignition device 28 for realizing such an ignition mode. FIG. 3 shows a configuration for one cylinder for convenience, but actually, a configuration for the number of cylinders of the engine is provided.
[0040]
3, an energy storage coil 72 and a transistor 73 are connected in series to a battery 71 serving as a DC power supply. Electric energy is stored in the energy storage coil 72 when the transistor 73 is turned on. i0 is a current flowing through the coil 72. In addition, a capacitor 75 is connected between the energy storage coil 72 and the transistor 73 via a diode 74. The capacitor 75 is charged by the electric energy stored in the energy storage coil 72.
[0041]
The ignition coil 76 includes a primary coil 76a and a secondary coil 76b. The capacitor 75 is connected to one end of the primary coil 76a, and the transistor 77 is connected to the other end. In this case, by turning on / off the transistor 77, the electric energy stored in the energy storage coil 72 and the capacitor 75 is sequentially released, and the primary current i1 flows through the primary coil 76a. The ignition plug 27 is connected to the secondary coil 76b of the ignition coil 76. When the primary coil 76a is energized, a secondary current i2 flows through the secondary coil 76b. Then, a discharge spark is generated in the ignition plug 27 by the supply of the discharge energy from the ignition coil 76 (the application of a high voltage).
[0042]
The ECU 40 calculates an optimal ignition timing according to the current engine operating state and the like, generates a discharge section signal IGw and an ignition signal IGt based on the ignition timing, and outputs them to the drive circuit 78. Drive circuit 78 generates drive signals IG1 and IG2 based on discharge section signal IGw and ignition signal IGt, and outputs drive signals IG1 and IG2 to transistors 73 and 77, respectively.
[0043]
The outline of the ignition operation by the ignition device 28 will be described with reference to the time chart of FIG. FIG. 4 shows an example in which the discharge extension immediately after the ignition timing and the subsequent multiple discharge are successively performed. In FIG. 4, time t2 to t3 is the period of discharge extension, and time t3 to t4 is the multiple discharge. Period. FIG. 4 shows the operation of the transistors 73 and 77 by the discharge section signal IGw, the ignition signal IGt, the drive signals IG1 and IG2, the current i0 flowing through the energy storage coil 72, the primary current i1 and the secondary current i2 of the ignition coil 76. Is shown.
[0044]
In FIG. 4, between times t1 and t2, the ignition signal IGt rises to the H level, and in response thereto, the drive signal IG1 rises to the H level. When the drive signal IG1 rises, the transistor 73 is turned on, and energy is stored in the energy storage coil 72.
[0045]
At time t2, which is the ignition timing, the drive signals IG1 and IG2 are respectively operated to L level and H level by the fall of the ignition signal IGt, and the transistor 73 is turned off and the transistor 77 is turned on. Thus, the energy of the energy storage coil 72 and the energy of the capacitor 75 are simultaneously supplied to the primary coil 76a of the ignition coil 76, a high voltage is induced on the secondary side, and a discharge spark is generated in the ignition plug 27. After t2, the discharge at the ignition plug 27 is started. In the period from time t2 to t3, magnetic energy is accumulated in the ignition coil 76 because the transistor 77 is ON.
[0046]
The discharge section signal IGw is at the H level during the period from time t2 to t4, and during this period, the transistors 73 and 77 are alternately turned on and off, so that multiple discharge of the ignition plug 27 is performed. That is, when the transistor 73 is turned on, magnetic energy is stored in the energy storage coil 72. When the transistor 73 is turned on and the transistor 77 is turned off, the magnetic energy stored in the ignition coil 76 is stored in the ignition plug 76. It is released as 27 discharge energy. Thereafter, when the transistor 73 is turned off, the magnetic energy of the energy storage coil 72 is released as the discharge energy of the ignition plug 27. When the transistor 73 is turned off and the transistor 77 is turned on, the ignition coil 76 is turned on again. Energy is stored in Thus, the transistors 73 and 77 are alternately turned ON / OFF, so that the energy of the energy storage coil 72 and the energy of the ignition coil 76 are alternately used, and the discharge of the ignition plug 27 is repeated. As a result, the spark discharge of the ignition plug 27 is continued in the discharge section. After the end of the discharging, the transistor 73 is turned on and the capacitor 75 is charged.
[0047]
Next, a procedure of a combustion improvement process performed by the ECU 40 will be described. FIG. 5 is a flowchart showing a combustion improvement processing routine, which is executed by the ECU 40 each time a rising edge of the crank angle signal is detected (that is, every 30 ° CA).
[0048]
In FIG. 5, first, in step S101, detection of the combustion state is performed based on the engine operating state in each case. As a method for detecting the combustion state, any method can be applied as long as an unstable combustion state due to incomplete ignition or misfire can be detected, but a detection method based on an engine rotation fluctuation amount is disclosed here as an example. I do. 6, a crank angle signal is read in step S201, and an elapsed time T30 between predetermined crank angles (30 ° CA in the present embodiment) is read in step S202.
[0049]
Thereafter, in step S203, the maximum value and the minimum value of the elapsed time T30 in the combustion stroke are calculated, and are set to T30MAX and T30MIN, respectively. In step S204, a current value ΔT30i of a difference between the maximum value T30MAX and the minimum value T30MIN is calculated for each cylinder. Further, in step S205, a smoothing process of the difference ΔT30 is performed. That is, the difference ΔT30 after the averaging is calculated by the following equation (1) using the averaging constant k.
ΔT30 = ΔT30 + k × (ΔT30i−ΔT30) (1)
After that, in step S206, the average value ΔT30ave of the difference ΔT30 is calculated using the past n times of data, and in the following step S207, the rotation fluctuation amount DEV is calculated by the following equation (2). Then, the process returns to the original process of FIG.
DEV = (ΔT30−ΔT30ave) / ΔT30ave (2)
After the detection of the combustion state (that is, after the calculation of the rotation fluctuation amount DEV), in step S102 of FIG. 5, it is determined whether or not the combustion has deteriorated based on the detection result of the combustion state. Specifically, the rotation fluctuation amount DEV calculated in the combustion state detection processing of FIG. 6 is compared with a predetermined determination value, and combustion deterioration is determined based on whether the rotation fluctuation amount DEV is larger than the determination value. If the rotation fluctuation amount DEV is equal to or less than the determination value and combustion has not deteriorated, the process proceeds to step S103, and normal ignition control is performed.
[0050]
If the rotation fluctuation amount DEV is larger than the determination value and the combustion is deteriorated, the process proceeds to step S104, and the engine operation state (engine speed, load information, etc.) is read. In the following step S105, the situation of the deterioration of combustion at that time is determined to be whether the combustion duration is improved by extending the discharge duration immediately after the start of discharge (extension of discharge), that is, only by performing the first discharge, or multiple discharge following the extension of discharge. That is, it is determined whether the second discharge is required. At this time, the engine operating state and the degree of combustion deterioration generally correspond to each other, and it is determined whether to extend the discharge or to extend the discharge and perform multiple discharges according to the engine operating state or the like each time. In the present embodiment, the determination is performed using a map prepared in advance and using load information such as an engine speed and an accelerator opening as parameters. In addition to the above, it is also possible to refer to the calculated rotation fluctuation amount DEV and perform the determination in step S105 according to the degree.
[0051]
Then, when it is determined that the combustion is improved only by the extension of the discharge (YES in step S105), the discharge continuation time is set in step S106 in order to extend the discharge. At this time, for example, the discharge duration time is basically set based on the in-cylinder temperature using the relationship shown in FIG. In FIG. 7, a relationship is defined such that the lower the in-cylinder temperature, the longer the discharge duration time. It is also possible to set the discharge duration by adding the state of the in-cylinder gas flow as a parameter. In such a case, the stronger the in-cylinder gas flow, the longer the discharge duration. However, the maximum value of the discharge duration time (maximum value) is limited due to the fact that there is a limit to the amount of energy stored on the primary side of the ignition coil, and that compression top dead center may occur during discharge continuation in the high engine speed range. It is desirable to define a guard), and the maximum value can be variably set according to various conditions. By limiting the maximum value of the discharge duration time, it is possible to suppress the discharge duration time from being unnecessarily extended, and it is possible to suppress energy consumption and prevent abrasion of the plug electrode. It is also possible to prevent the temperature near the electrode of the spark plug 27 from unnecessarily increasing.
[0052]
The in-cylinder temperature is measured by a temperature sensor installed in the combustion chamber 23 or estimated from parameters such as the intake air temperature and the intake air amount. Instead of the in-cylinder temperature, the temperature near the electrode of the spark plug may be used. The in-cylinder gas flow is estimated from the balance of the flow of the intake air (swirl, tumble, squish), the position of a swirl valve provided in the intake system (that is, the strength of the swirl), the amount of intake air, and the like. It is also possible to estimate the in-cylinder gas flow in consideration of the port shape and the piston shape.
[0053]
Then, in step S107, the ignition timing is corrected to the retard side. That is, when the process of extending the discharge is performed as described above, the combustion speed is increased, and the peak of the output torque is quickly reached after the start of the discharge. Therefore, the ignition timing is retarded according to the discharge continuation time (the degree of discharge extension) in anticipation of an increase in the combustion rate.
[0054]
On the other hand, if step S105 is NO, the discharge continuation time is set in step S108 and the multiple discharge period is set in step S109 in order to perform the discharge extension and the subsequent multiple discharge. In step S108, similarly to step S106, the discharge duration may be set based on the in-cylinder temperature and the in-cylinder gas flow, for example, using the relationship in FIG. However, in this case, since the discharge is extended in combination with the multiple discharges, the discharge duration may be set shorter than in the case of step S106. In step S109, for example, the multiple discharge period is set basically based on the state of the gas flow in the cylinder using the relationship shown in FIG. In FIG. 8, a relationship is defined such that the stronger the gas flow in the cylinder, the longer the multiple discharge period. However, when the engine is in a high rotation state or when the ignition timing is late, there is no time margin until the next ignition discharge, so the maximum value of the multiple discharge period (maximum value guard) should be specified. It is desirable that the maximum value can be variably set according to various conditions.
[0055]
Then, in step S110, the ignition timing is corrected to the retard side. At this time, as in step S107, the ignition timing is delayed according to the discharge continuation time (the degree of discharge extension) in anticipation of an increase in combustion speed due to the extension of discharge.
[0056]
Since the temperature change near the counter electrode is affected by the heat value of the ignition plug 27 used and the in-cylinder shape, it is desirable to adjust the discharge duration and the multiple discharge period according to the plug heat value and the in-cylinder shape. This makes it possible to suppress unnecessary energy consumption and to prevent electrode wear of the spark plug 27. In addition, as the multiple discharge condition, in addition to the multiple discharge period, the interval between individual discharges can be variably set according to the engine operating state.
[0057]
The time chart of FIG. 4 will be described again based on the processing of FIG. 4 corresponds to the discharge duration set in steps S106 and S108 (however, in FIG. 4, multiple discharges are combined, more precisely, the set time in step S108), and t3 in FIG. T4 corresponds to the multiple discharge period set in step S109.
[0058]
In the period from t2 to t3 in FIG. 4, the discharge spark is continuously generated due to the extension of the discharge, so that the temperature is promoted near the counter electrode of the ignition plug 27. In this case, the lower the in-cylinder temperature or the stronger the in-cylinder gas flow, the longer the discharge continuation time (period from t2 to t3). Since the temperature near the opposing electrode of the ignition plug 27 reliably rises to a temperature at which ignition is possible, the combustion reaction is activated, and the formation of a flame nucleus is favorably performed. When the discharge is extended, the energy storage time (the period from t1 to t2) is also extended so that a correspondingly large amount of electric energy can be stored in the ignition device 28.
[0059]
Thereafter, in the period from t3 to t4, the multiple discharge is performed in small increments, so that the temperature near the electrode of the ignition plug 27 is maintained. In this case, the stronger the in-cylinder gas flow, the longer the multiple discharge period (period from t3 to t4). Even if the gas flow in the cylinder is strong, a decrease in the temperature near the electrode is suppressed, and diffusion combustion is promoted. That is, the formation of a flame nucleus and the promotion of diffusion combustion can be realized by the discharge extension and the subsequent multiple discharge, and the combustion state is greatly improved.
[0060]
FIG. 9 is a time chart showing how the temperature changes near the plug electrode. The ignition signal in the figure corresponds to the drive signal IG1 in FIG. In FIG. 9, the temperature near the electrode increases with the start of the discharge at time t11, and the temperature near the electrode is maintained at a high temperature level (ignition temperature or higher) due to the discharge extension and multiple discharge. Therefore, formation of a flame nucleus and promotion of diffusion combustion can be reliably realized.
[0061]
According to the present embodiment described in detail above, the following excellent effects can be obtained.
[0062]
When the deterioration of combustion is detected, the discharge is extended immediately after the start of the discharge, or the subsequent multiple discharges are performed together, so that the ignitability is improved even under the condition of deterioration of combustion, and the combustion state is improved. Improvement and reduction of fuel consumption can be realized.
[0063]
In accordance with the combustion state in each case, the necessity of the combustion improvement processing is determined, and in the combustion improvement processing, either the discharge extension or the discharge extension + multiple discharge is selectively performed. Thus, effects such as suppression of energy consumption and prevention of wear of the plug electrode can be obtained in a well-balanced manner.
[0064]
When the duration of the discharge is extended, the electric energy stored in advance in the ignition device 28 is correspondingly increased, so that sufficient discharge energy for extending the duration of the discharge can be secured.
[0065]
Since the ignition timing is retarded when the duration of the discharge is extended, a desired output torque can be obtained at the optimum timing even if the discharge is extended.
[0066]
When the intake air amount control is performed by the variable valve mechanism 25 in the direction of limiting the intake air amount, the combustion state becomes unstable due to a decrease in the actual compression ratio or the like, and the combustion may be deteriorated. As described above, by performing the combustion improvement processing such as the discharge extension and the multiple discharge, the combustion improvement can be realized.
[0067]
The present invention is not limited to the description in the above embodiment, and may be implemented, for example, as follows.
[0068]
As a method of detecting the combustion state, the following detection method may be used instead of the detection method based on the rotation fluctuation amount of the engine 10.
Calculate the pressure fluctuation amount in the combustion chamber 23 and detect the combustion state based on the pressure fluctuation amount. Since in-cylinder pressure fluctuations occur at the time of combustion deterioration, combustion deterioration can be accurately detected. The in-cylinder pressure is preferably calculated from a detection value of a combustion pressure sensor installed in a cylinder block.
An ion current detection circuit is provided on the secondary side of the ignition coil to measure an ion current generated at the time of fuel combustion, and a combustion state is detected based on the ion current. When the combustion deteriorates, the ion current fluctuates, so that the combustion deterioration can be detected with high accuracy.
[0069]
Instead of directly detecting the deterioration of combustion, combustion state data may be defined for each engine operating region, and the combustion state may be estimated using the combustion state data. As parameters for estimating combustion deterioration, the engine speed, idle state, intake air amount, intake air temperature, engine water temperature, fuel injection amount, operating states of the variable valve mechanisms 25 and 26, battery voltage, and the like are used. In this case, if it is estimated from various estimated parameters that combustion deterioration will occur, combustion improvement processing such as discharge extension and multiple discharge is performed. Therefore, the combustion improvement processing can be performed promptly with respect to the deterioration of the combustion or before the actual deterioration of the combustion.
[0070]
In the above embodiment, whether to extend the discharge or to extend the discharge and perform the multiple discharges is determined according to the engine operating state or the like at each time (step S105 in FIG. 5), but this is changed. For example, after the combustion is deteriorated, the combustion deterioration may be determined again in the state where the discharge is extended, and if the combustion deterioration is not improved by merely extending the discharge, the ignition may be switched to the discharge extension + multiple discharge ignition mode. . In this case, when the combustion deteriorates, the ignition mode is switched in the order of normal discharge → extension of discharge → extension of discharge + multiple discharge.
[0071]
The ignition technique using multiple discharges has been put into practical use before itself, and there is also one that switches between normal ignition and multiple ignition according to the engine operating range. FIG. 10 shows the operation regions of the normal ignition and the multiple ignition. Specifically, a normal ignition zone is set in a high load region of the entire rotation range, and a multiple ignition zone is set in a region from 1000 rpm or more to a medium load. Further, the ignition mode of the discharge extension + multiple discharge in the present invention is set in a region of lower rotation and lower load (less than 1000 rpm, near no load) in the multiple ignition zone. By using the relationship of FIG. 10, it is possible to appropriately switch each ignition mode such as normal ignition, multiple ignition, and discharge extension + multiple discharge.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an engine control system according to an embodiment of the present invention.
FIG. 2 is a configuration diagram of a variable valve mechanism.
FIG. 3 is a circuit diagram showing a configuration of an ignition system.
FIG. 4 is a time chart for explaining an ignition operation.
FIG. 5 is a flowchart showing a combustion improvement process.
FIG. 6 is a flowchart showing a combustion state detection process.
FIG. 7 is an explanatory diagram for setting a discharge duration time.
FIG. 8 is an explanatory diagram for setting a multiple discharge period.
FIG. 9 is a time chart showing transition of the temperature near the electrode.
FIG. 10 is a diagram showing an operation region of each ignition mode.
[Explanation of symbols]
10 ... Engine,
21 ... intake valve,
23 ... combustion chamber,
25 ... variable valve mechanism,
27 ... Spark plug,
28 ... Ignition device,
40 ... ECU.

Claims (16)

In a control device for an internal combustion engine applied to an internal combustion engine ignition system in which a high voltage is applied from an ignition device to generate a discharge spark between opposed electrodes of a spark plug and burn fuel introduced into a combustion chamber,
Ignition control means for controlling the ignition timing of the ignition plug;
And combustion state detection means for detecting the combustion state of the internal combustion engine,
The ignition control means includes means for variably setting the duration of the discharge after the start of the discharge at the ignition timing, and extending the duration of the discharge when the deterioration of combustion is detected by the combustion state detecting means. A control device for an internal combustion engine, comprising: 2. The control device for an internal combustion engine according to claim 1, wherein the ignition control means variably sets a duration of the discharge in accordance with a temperature in the cylinder. 3. The control device for an internal combustion engine according to claim 1, wherein the ignition control means variably sets a duration of the discharge in accordance with a state of the in-cylinder gas flow. The control device for an internal combustion engine according to any one of claims 1 to 3, wherein a limit is set for extending the duration of the discharge. The ignition control means further includes means for intermittently and repeatedly performing discharge by the spark plug for one combustion stroke, and a second means for repeating the discharge in small increments following the first discharge in which the duration of the discharge is extended. The control device for an internal combustion engine according to any one of claims 1 to 4, wherein discharging is performed. 6. The control device for an internal combustion engine according to claim 5, wherein the ignition control means variably sets an execution period of the second discharge in accordance with a state of gas flow in the cylinder. 7. The control apparatus for an internal combustion engine according to claim 5, wherein an ignition mode consisting of only the first discharge or an ignition mode consisting of the first discharge and the second discharge is selectively selected according to the operating state of the internal combustion engine in each case. A control device for an internal combustion engine, wherein the control device is implemented. The ignition device stores electric energy for generating a discharge spark every time of ignition and applies a high voltage to a spark plug by discharging the electric energy. 8. The control device for an internal combustion engine according to claim 1, wherein the electric energy previously stored in said ignition device is correspondingly increased. The control device for an internal combustion engine according to any one of claims 1 to 8, wherein the ignition control means delays the ignition timing when extending the duration of the discharge. In a control device for an internal combustion engine applied to an internal combustion engine ignition system in which a high voltage is applied from an ignition device to generate a discharge spark between opposed electrodes of a spark plug and burn fuel introduced into a combustion chamber,
An ignition control means for controlling an ignition timing of the ignition plug, the ignition control means extending a discharge duration immediately after the start of discharge to increase a temperature near the electrode; A second combustion improving means for intermittently and repeatedly performing discharge by a spark plug for each combustion stroke in order to maintain the temperature near the electrode after the temperature rise. Control device for an internal combustion engine. The engine further includes combustion state detection means for detecting a combustion state of the internal combustion engine. When the combustion state detection means detects deterioration in combustion, the ignition control means includes a first combustion improvement means and a second combustion improvement means. The control device for an internal combustion engine according to claim 10, wherein the combustion improvement is performed by the means. The control device for an internal combustion engine according to claim 10 or 11, wherein the ignition control means implements only the first combustion improvement means or the first combustion improvement means according to the operating state of the internal combustion engine at each time. And a control device for controlling the internal combustion engine, which selects whether to implement both the second combustion improvement means and the second combustion improvement means. The internal combustion engine according to any one of claims 1 to 9, wherein the combustion state detection means calculates a rotation fluctuation amount of the internal combustion engine and detects a combustion state based on the rotation fluctuation amount. Control device. 12. The method according to claim 1, wherein the combustion state detecting means calculates a pressure fluctuation amount in a combustion chamber of the internal combustion engine, and detects a combustion state based on the pressure fluctuation amount. Control device for internal combustion engine. In place of the combustion state detecting means, a means for defining combustion state data for each operating region of the internal combustion engine and estimating a combustion state using the combustion state data is provided. The control device for an internal combustion engine according to any one of claims 1 to 9, wherein the process is performed. Applied to an internal combustion engine having a variable valve mechanism for controlling the intake air amount by variably adjusting the opening and closing operation conditions of the intake valve, and setting the opening and closing operation conditions of the intake valve in a direction to limit the intake air amount The control device for an internal combustion engine according to any one of claims 1 to 15, wherein the variable valve mechanism is controlled.

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