JP2005002883A - Controller for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress reduction of engine output at a transient time for suppressing knocking. <P>SOLUTION: This spark ignition type internal combustion engine provided with an ignition plug 9 is provided with a variable compression ratio mechanism 20 for changing engine compression ratio. When detecting the occurrence of knocking by a knock sensor 15, engine compression ratio and ignition time are controlled so that reduction of engine output becomes the minimum extent. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for a spark ignition internal combustion engine having a variable compression ratio mechanism, and more particularly to a technique for effectively avoiding knocking.
[0002]
[Prior art]
In Patent Document 1, in a spark ignition type internal combustion engine equipped with a variable compression ratio mechanism capable of changing the engine compression ratio and an ignition plug, when knocking is detected by a knocking sensor, the compression ratio is first lowered, and thereafter A technique for avoiding knocking by retarding the ignition timing when knocking continues is disclosed.
[0003]
[Patent Document 1]
Japanese Patent Publication No. 05-059273 [0004]
[Problems to be solved by the invention]
The above-mentioned Patent Document 1 does not take into consideration a decrease in engine output / torque during a transition period in which the compression ratio and the ignition timing are changed in order to avoid knocking. The present invention has been made paying attention to this point.
[0005]
[Means for Solving the Problems]
In a spark ignition type internal combustion engine control device equipped with a variable compression ratio mechanism capable of changing the engine compression ratio and an ignition plug, when the occurrence of knocking is detected by the detection means, the output reduction of the engine is minimized. The engine compression ratio and ignition timing are controlled.
[0006]
【The invention's effect】
According to the present invention, when knocking is detected, the occurrence of knocking can be suppressed and avoided while minimizing a decrease in engine output.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, this internal combustion engine is roughly constituted by a cylinder head 1 and a cylinder block 2, and an ignition for spark-igniting an air-fuel mixture in a combustion chamber 4 defined above a piston 3. A spark ignition internal combustion engine such as a gasoline engine provided with a plug 9. As is well known, this internal combustion engine includes an intake valve 5 that opens and closes an intake port 7, an exhaust valve 6 that opens and closes an exhaust port 8, a fuel injection valve 10 that injects fuel into the intake port 7, and an intake collector 18. And a throttle 16 for adjusting the intake air amount by opening and closing the upstream side, and a variable compression ratio mechanism 20 capable of changing the engine compression ratio.
[0008]
The ECU (engine control unit) 11 is a well-known digital computer having a CPU, ROM, RAM, and an input / output interface, and includes an accelerator opening sensor 12 that detects the accelerator opening, and a water temperature sensor 13 that detects the engine water temperature. Based on detection signals from various sensors such as a crank angle sensor 14 for detecting the engine speed and a knock sensor 15 for detecting the presence or absence of knocking, a driving device 16a for the fuel injection valve 10, the spark plug 9, and the throttle 16 is provided. , And a control signal is output to various actuators such as the drive unit 21 of the variable compression ratio mechanism 20 to comprehensively control the fuel injection amount, fuel injection timing, ignition timing, throttle opening, engine compression ratio, and the like.
[0009]
Referring to FIG. 2, the variable compression ratio mechanism 20 includes a lower link 24 rotatably attached to a crankpin 23 of a crankshaft 22, an upper link 25 that links the lower link 24 and the piston 3, and an eccentricity. A control shaft 27 provided with a shaft 28 and a control link 26 that links the eccentric shaft 28 and the lower link 24 are provided. When the rotational position of the control shaft 27 is changed by the driving device 21 (see FIG. 1), the motion restraint condition of the lower link 24 by the control link 26 changes, and the stroke characteristics of the piston 3, that is, the top dead of the piston 3 The point position and the engine compression ratio are continuously changed and controlled.
[0010]
3 and 4 show an example of control of the ignition timing and the compression ratio when knocking occurs according to the present invention. When the occurrence of knocking is detected, the ignition timing and the engine compression ratio are controlled so that the output / torque reduction of the engine is minimized. For example, if point A is set as the initial compression ratio and ignition timing, knocking occurs due to a rise in temperature or the like, and when this is detected by a knock sensor, the ignition timing is first retarded toward point B. To avoid knocking. If knocking continues, the ignition timing is retarded and the compression ratio is lowered to shift to point C. If knocking continues, the compression ratio is lowered and moved to point D. To do.
[0011]
For example, when the occurrence of knocking is detected, the compression ratio is first lowered, and if knocking is detected after the compression ratio reaches the lowest value that can be set, knocking is avoided by retarding the ignition timing. Control may be performed in the same way. Alternatively, when the occurrence of knocking is detected, the ignition timing is first retarded, and if knocking is detected after the ignition timing reaches the retardation limit, knocking is avoided by reducing the compression ratio. Control may be performed. It should be noted that the control amount for avoiding knocking, that is, the retard amount of the ignition timing and the decrease amount of the compression ratio are preferably set according to engine operating conditions such as engine speed and load.
[0012]
FIG. 5 is a flowchart showing a flow of control according to the first embodiment of the present invention. This routine is repeatedly executed by the ECU 11 at predetermined intervals, for example. In S (step) 11, the detection signal of the knock sensor 15 is read. In S12, based on the detection signal of the knock sensor 15, it is determined whether or not knocking has occurred. If it is determined that knocking has not occurred, the process proceeds to S24, an index K and variables I and J, which will be described later, are initialized to 0, and this routine is terminated.
[0013]
In S13, 1 is added to the knocking strength index K, and the maximum value TMAX of the engine output index T is initialized to 0. The knocking strength index K corresponds to the degree of knocking suppression. Basically, the larger the value of the index K, the greater the retard of the ignition timing and the degree of decrease in the engine compression ratio for reducing knocking. The smaller the value of K, the smaller the retard of the ignition timing and the degree of decrease in the engine compression ratio for reducing knocking.
[0014]
In S14, 1 is added to the ignition timing control variable I. In S15, 1 is added to the compression ratio control variable J. In S16, the value K (I, J) is compared with the knocking strength index K. If K (I, J) is not equal to K, S17 and S18 are skipped and the process proceeds to S19. As shown in FIG. 6, the above K (I, J) is obtained by mapping the current variable I and variable J to a preset knocking strength index K map. For example, K (2,3) is 5.
[0015]
In S17, it is determined whether the value T (I, J) is equal to or greater than TMAX. The value T (I, J) is obtained by mapping the variables I and J to the engine output index T map shown in FIG. Values corresponding to the engine output / torque are stored in T11, T12,..., T88 on the map of FIG. These values may be fixed values set in advance, or may be calculated and updated based on the engine speed and the engine load. If T (I, J) is smaller than TMAX, S18 is skipped and the process proceeds to S19. If both S16 and S17 are affirmed, the process proceeds to S18, where variable I is substituted for ITRG and variable J is substituted for JTRG.
[0016]
In S19, the variable J is compared with the maximum value JMAX (8 in the examples of FIGS. 6 and 7) of this variable. If the variable J has not reached the maximum value JMAX, the process returns to S14. In S20, the variable I is compared with the maximum value IMAX (8 in the examples of FIGS. 6 and 7) of this variable. If the variable I has not reached the maximum value IMAX, the process returns to S15 described above.
[0017]
When both the variables I and J reach the maximum value and the processing for all the regions / combinations in the map of FIG. 6 is completed, the determinations in S19 and S20 are affirmed and the process proceeds to S21, and the ignition timing is based on the above-mentioned ITRG. Control command value ADV, that is, an ignition timing (a retarded angle) for avoiding knocking, and a control command value CR for engine compression ratio, that is, compression for avoiding knocking, based on the above JTRG The ratio (degree of decrease) is calculated. In S22, ignition timing retardation control is performed based on the control command value ADV. In S23, the engine compression ratio is lowered based on the control command value CR.
[0018]
According to this routine, when knocking is detected, first, in S13, the knocking intensity index K corresponding to the knocking suppression degree is set to 1, and the ignition timing control variable is set to K = 1 with reference to the map of FIG. The combination K (I, J) of I and the compression ratio control variable J is selected (S16), and the combination T (I, J) having the largest engine output is selected from the selected combinations (S17). The ignition timing and the compression ratio are controlled based on the ignition timing control variable ITRG and the compression ratio control variable JTRG corresponding to the combination T (I, J) (S18, S21 to S23). If knocking is detected again, in S13, the knocking intensity index K corresponding to the degree of knocking suppression is increased by one level to 2, and the ignition timing and the compression ratio are controlled so that the engine output becomes maximum as described above. . In this way, the ignition timing and the compression ratio are controlled so that the engine output is maximized (the engine output decrease is minimized) while gradually changing the knocking intensity until occurrence of knocking is not detected. . Therefore, it is possible to minimize a decrease in the engine output during the transition period in which the ignition timing and the engine compression ratio are controlled in order to avoid knocking.
[0019]
FIG. 8 is a flowchart showing the flow of control according to the second embodiment of the present invention. The same processing contents as those in the first embodiment shown in FIG. In the second embodiment, after adding 1 to the knocking strength index K in S13, the process proceeds to S13a to determine whether the knocking strength index K exceeds the maximum value KMAX (7 in the example of FIG. 6). Until the knocking strength index K exceeds the maximum value KMAX, the process proceeds to S14 and the same processing as in the first embodiment is performed. When the knocking strength index K exceeds the maximum value KMAX, the process proceeds from S13a to S25, and the intake air amount is limited. Specifically, the opening degree of the throttle 16 is reduced.
[0020]
According to the second embodiment, the same effect as the first embodiment can be obtained, and the intake air amount can be reduced even in a situation where the occurrence of knocking cannot be avoided due to the retard of the ignition timing and the reduction of the compression ratio. Therefore, knocking can be avoided, and knocking can be avoided and suppressed more reliably.
[0021]
As described above, the present invention has been described based on the specific embodiments. However, the present invention is not limited to the above-described embodiments, and includes various modifications and changes without departing from the spirit of the present invention. .
[Brief description of the drawings]
FIG. 1 is a system configuration diagram showing a control device for an internal combustion engine according to the present invention.
FIG. 2 is a schematic configuration diagram showing a variable compression ratio mechanism.
FIG. 3 is a characteristic diagram showing how ignition timing and compression ratio are controlled when knocking occurs.
FIG. 4 is a characteristic diagram showing how ignition timing and compression ratio are similarly controlled when knocking occurs.
FIG. 5 is a flowchart showing a control flow according to the first embodiment of the present invention.
FIG. 6 is a control map of a knocking strength index K.
FIG. 7 is a control map of an engine output index T.
FIG. 8 is a flowchart showing a control flow according to the second embodiment of the present invention.
[Explanation of symbols]
4 ... Combustion chamber 9 ... Spark plug 11 ... ECU
15 ... Knock sensor 16 ... Throttle 20 ... Variable compression ratio mechanism

Claims (4)

In a control device for a spark ignition internal combustion engine having a variable compression ratio mechanism capable of changing the engine compression ratio and an ignition plug,
Detection means for detecting the occurrence of knocking;
Control means for controlling the engine compression ratio and the ignition timing so as to minimize the decrease in engine output when knocking is detected by the detection means;
A control apparatus for an internal combustion engine, comprising: 2. The control device for an internal combustion engine according to claim 1, wherein the control unit increases a knocking strength index corresponding to a degree of suppression of knocking in a stepwise manner until occurrence of knocking is not detected. The control means selects a combination that maximizes engine output from a plurality of combinations of ignition timing control variables and compression ratio control variables that have the same knocking strength index, and sets the ignition timing control variable for the selected combination. The control apparatus for an internal combustion engine according to claim 2, wherein the ignition timing and the engine compression ratio are controlled based on the compression ratio control variable. The control apparatus for an internal combustion engine according to any one of claims 1 to 3, further comprising means for reducing an intake air amount when occurrence of knocking is detected by the detection means.

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