JP3937680B2 - Knock control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a knock control device for an internal combustion engine, and more particularly to a knock control device that uses both ignition timing control and variable valve control (valve timing control).
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a knock control device for an internal combustion engine that detects the occurrence of knock (knock) and retards the ignition timing when the knock occurs (retard) to avoid the occurrence of knock is well known. It has been.
[0003]
On the other hand, as a variable valve operating device for an internal combustion engine, as disclosed in JP-A-8-200025, for example, an electromagnetic drive device is used to drive an intake valve and an exhaust valve, and these opening / closing operations (valve timing) Can be controlled arbitrarily.
[0004]
[Problems to be solved by the invention]
By the way, in the conventional knock control device for an internal combustion engine, the occurrence of the knock is dealt with by retarding the ignition timing. However, the effective compression ratio becomes larger than the design value due to the accumulation of deposits in the combustion chamber. If gasoline with extremely bad fuel properties is used, or if conditions such as an increase in intake air temperature overlap, it may be impossible to cope with the ignition timing delay of knock control.
[0005]
Further, if the retard amount (retard angle limit) of the ignition timing is increased to cope with it, the exhaust temperature rises.
In view of such a conventional problem, the present invention uses a variable valve operating apparatus without retarding the ignition timing any more when the ignition timing reaches a predetermined retardation limit due to the occurrence of knocking. An object of the present invention is to reliably prevent the occurrence of knocking.
[0006]
[Means for Solving the Problems]
Therefore, in the invention according to claim 1, as shown in FIG. 1, the knock of the internal combustion engine comprising knock detection means for detecting the occurrence of knock and ignition timing correction control means for retarding the ignition timing when the knock occurs. In the control device, the retard timing limit judging means for judging that the ignition timing has reached a predetermined retard limit, and the variable valve mechanism at the time of knock occurrence at the retard limit of the ignition timing, the valve timing of the intake valve is set. and valve timing control means for controlling the decreasing direction of the intake air amount and the effective compression ratio, while Ru provided, during knock is generated, the valve timing control means, intake valve timing to the base timing air volume and the effective compression The valve timing is gradually returned to the base timing on the condition that the ratio is controlled to decrease, and the ignition timing correction control means On condition that the blanking timing in the base timing, characterized by being configured the ignition timing so as to gradually advance.
[0007]
That is, the presence or absence of knocking is detected and the ignition timing is retarded at the time of knocking, but when knocking still occurs even when the ignition timing reaches a predetermined retardation limit, the variable valve device The valve timing of the intake valve is controlled in the decreasing direction of the intake air amount and the effective compression ratio to avoid knocking.
[0008]
The invention according to claim 2 is characterized in that the valve timing control means controls the intake valve closing timing to be delayed from the bottom dead center when knocking occurs at the retard limit of the ignition timing.
[0009]
The invention according to claim 3 is characterized in that the valve timing control means controls the intake valve closing timing earlier than the bottom dead center when knocking occurs at the retard limit of the ignition timing.
[0010]
In the invention according to claim 4, the valve timing control means is configured to close the intake valve in a region where the base intake valve closing timing is at the bottom dead center or before the bottom dead center when knocking occurs at the retard limit of the ignition timing. The control is performed in a direction to advance the timing, and in a region where the base intake valve closing timing is after the bottom dead center, the control is performed in a direction to delay the intake valve closing timing.
[0012]
In the invention according to claim 5 , in the high-octane gasoline type internal combustion engine, the base ignition timing is set to high-octane (high octane number) when the retardation limit determining means determines that the ignition timing has reached a predetermined retardation limit. ) It is characterized in that a base ignition timing switching means for switching from a base ignition timing for gasoline to a base ignition timing for regular gasoline is provided.
[0013]
【The invention's effect】
According to the first aspect of the present invention, in the abnormal situation that cannot be dealt with by normal knock control, such as when knocking still occurs even when the ignition timing reaches the predetermined retardation limit, the variable valve device performs intake air. By controlling the valve timing of the valve in the decreasing direction of the intake air amount and the effective compression ratio, knocking can be reliably avoided.
[0014]
If this method is used, it is possible to suppress an increase in the exhaust gas temperature as compared with the case where the ignition timing is further retarded, and to reduce the effective compression ratio even when compared with the case where the air is simply throttled with the throttle valve, The maximum combustion pressure and temperature are lowered, and knocking can be avoided more reliably.
When knocking does not occur during the knock control based on the valve timing, first, the valve timing is gradually returned to the base timing, so that the control can be shifted to the normal ignition timing as quickly as possible.
[0015]
According to the second aspect of the present invention, the intake air amount and the effective compression ratio are reduced by controlling the intake valve closing timing to be delayed from the bottom dead center when knocking occurs at the retard limit of the ignition timing. Thus, knocking can be avoided reliably.
[0016]
According to the third aspect of the present invention, when knocking occurs at the retard limit of the ignition timing, the intake valve closing timing is controlled in a direction earlier than the bottom dead center, so that no blow back to the intake system occurs. By reducing the intake air amount and the effective compression ratio, knocking can be reliably avoided.
[0017]
According to the fourth aspect of the present invention, when the knock occurs at the retard limit of the ignition timing, the intake valve closing timing is made earlier in the low speed region where the base intake valve closing timing is at or before the bottom dead center. By controlling in such a direction, knocking can be reliably avoided by reducing the intake air amount and the effective compression ratio by fine control of timing and without causing blowback to the intake system. Further, in the middle and high rotation range where the intake valve closing timing of the base is after the bottom dead center, knocking can be surely avoided by controlling the intake valve closing timing to be delayed so that the timing is finely controlled. .
[0019]
According to the invention of claim 5 , particularly in the case of an engine with a high-octane gasoline specification, when it is determined that the ignition timing has reached a predetermined retardation limit, it is assumed that regular gasoline is being used. By switching from the ignition timing for high-octane gasoline to the base ignition timing for regular gasoline, when regular gasoline is actually used, without shifting to valve timing control with a large rebound to torque, It is possible to avoid knocking by appropriately retarding the ignition timing.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
FIG. 2 is a system diagram of an internal combustion engine showing an embodiment of the present invention.
[0021]
A combustion chamber 3 defined by a piston 2 of each cylinder of an internal combustion engine (hereinafter referred to as an engine) 1 is provided with an electromagnetically driven intake valve 5 and an exhaust valve 6 so as to surround the spark plug 4. 7 is an intake passage and 8 is an exhaust passage.
[0022]
FIG. 3 shows the basic structure of an electromagnetic drive device (variable valve operating device) for the intake valve 5 and the exhaust valve 6. A plate-like movable element 22 is attached to the valve shaft 21 of the valve body 20, and the movable element 22 is biased to a neutral position by springs 23 and 24. A valve opening electromagnetic coil 25 is disposed below the mover 22, and a valve closing electromagnetic coil 26 is disposed above the movable element 22.
[0023]
Therefore, when opening the valve, after energization of the upper valve closing electromagnetic coil 26 is stopped, by energizing the lower valve opening electromagnetic coil 25 and attracting the mover 22 downward, The valve body 20 is lifted and opened. Conversely, when closing the valve, by energizing the lower valve opening electromagnetic coil 25 and then energizing the upper valve closing electromagnetic coil 26 to attract the mover 22 upward, The valve body 20 is seated on the seat portion and closed.
[0024]
Returning to FIG. 2, an electric throttle valve 9 is provided in the intake passage 7 upstream of the intake manifold. The intake passage 7 is also provided with an electromagnetic fuel injection valve 10 for each cylinder in each branch portion of the intake manifold.
[0025]
Here, the operation of the intake valve 5, the exhaust valve 6, the electric throttle valve 9, the fuel injection valve 10 and the spark plug 4 is controlled by the control unit 11, and the control unit 11 has a crank in synchronization with the engine rotation. A crank angle sensor 12 that outputs an angle signal and can detect the engine speed Ne together with the crank angle position, an accelerator pedal sensor 13 that detects an accelerator opening (accelerator pedal depression amount) APO, and an upstream of a throttle valve 9 in the intake passage 7 In addition to the air flow meter 14 that detects the intake air amount Qa, a signal is input from a knock sensor 15 as a knock detection means.
[0026]
The knock sensor 15 is attached to a main body such as a cylinder block of the engine 1 and outputs a signal corresponding to engine vibration by a piezoelectric element. A signal (knock signal) of a specific frequency component related to knock vibration from the output signal. Can be taken out. As the knock sensor 15, a piezoelectric in-cylinder pressure sensor that is formed and attached to the spark plug 4 in the form of a washer may be used to extract the knock signal from the output signal.
[0027]
The control of the ignition timing of the spark plug 4 in the control unit 11 is performed based on the engine operating conditions, specifically, the engine speed Ne and the load (accelerator opening, cylinder intake air amount, fuel injection amount, etc.) TQ. Referring to this, the base ignition timing ADVbase is determined and corrected by knock control, that is, corrected according to the presence or absence of occurrence of knock based on the signal from the knock sensor 15, and the final ignition timing ADV is calculated. By doing.
[0028]
Further, in the present invention, when the ignition timing ADV reaches the retard limit by knock control and knock still occurs, the valve timing of the intake valve 5 and the exhaust valve 6, particularly the intake valve close timing IVC is controlled by the variable valve operating device. By controlling this, knock control is performed.
[0029]
Such knock control will be described.
FIG. 4 is a flowchart of the knock control routine.
In step 1 (denoted as S1 in the figure, the same applies hereinafter), the presence or absence of the occurrence of knock is detected based on the signal from knock sensor 15. Specifically, the level of the knock vibration is detected by extracting a signal (knock signal) of a specific frequency component related to the knock vibration from the signal corresponding to the engine vibration output from the knock sensor 15, and the magnitude of the level is detected. Is used to determine whether knock has occurred or not. This part corresponds to the knock detection means together with the knock sensor 15.
[0030]
When knocking occurs (when knocking is present), the process proceeds to step 2.
In step 2, it is determined whether or not the ignition timing ADV is controlled to a predetermined delay limit (retard amount RET ≧ predetermined value) based on the retard of the ignition timing ADV due to the continuous occurrence of knock. This portion corresponds to the retard limit determination means.
[0031]
If the retard limit has not been reached, go to step 3.
In step 3, the ignition timing ADV is retarded by a predetermined value to avoid knocking. More specifically, the ignition timing retard amount RET is increased by a predetermined value ΔRET (RET = RET + ΔRET), and the base ignition timing (advance value) ADVbase retarded from the engine speed Ne and the load TQ is determined with reference to the map. The ignition timing ADV = ADVbase−RET is calculated by subtracting the amount RET and controlled. This portion corresponds to the ignition timing correction control means.
[0032]
When the ignition timing ADV reaches a predetermined retardation limit due to continuous retardation (when the retardation amount RET ≧ predetermined value), the process proceeds from step 2 to step 4.
In step 4, in order to avoid knocking at the retard limit, the valve timing of the intake valve 5 and the exhaust valve 6, particularly the intake valve closing timing IVC, is controlled in the decreasing direction of the intake air amount and the effective compression ratio by the variable valve device. (IVC control) This part corresponds to the valve timing control means.
[0033]
Specifically, the valve timing at full load (4/4 o'clock) shown in FIG. 5 (a) is lower than the intake valve closing timing IVC during knock control as shown in FIG. 5 (b). Control the direction slower than the point BDC (IVC for late closing), or control the timing for closing the intake valve IVC earlier than the bottom dead center BDC (IVC for early closing), and adjust the intake air amount and effective compression ratio. Decrease. In FIG. 5, EVO is the exhaust valve opening timing, EVC is the exhaust valve closing timing, and IVO is the intake valve opening timing, which are constant.
[0034]
More specifically, when knocking occurs at the retard limit of the ignition timing, the intake valve closing timing IVC is advanced in a low rotation region where the base intake valve closing timing (base IVC) is near (or before) the BDC ( In the middle and high rotation range where the base intake valve closing timing (base IVC) is after BDC, the intake valve closing timing IVC is controlled to be delayed (slow closing IVC).
[0035]
Comparing the early closing and the late closing, in the case of the late closing, the intake air temperature rises due to the blow back to the intake system, or an intake air amount measurement error occurs in the air flow meter. Although it is advantageous, if the base intake valve closing timing (base IVC) is BDC or later, if the valve is quickly closed, the timing change margin must be increased (if the valve is slightly advanced, the intake air amount is This is because the effective compression ratio increases, but it is not suitable for fine control such as knock control, and there is a concern about rebound to drivability.
[0036]
In the case of controlling as described above, the IVC control in step 4 of FIG. 4 is executed according to the IVC control subroutine of FIG.
In step 41, it is determined whether or not the base IVC is near (or before) the BDC. If yes, the process proceeds to step 42, and the IVC is advanced by a predetermined value (early closing). In the case of No (when the base IVC is BDC or later), the routine proceeds to step 42, where the IVC is delayed by a predetermined value (late closing).
[0037]
By controlling the intake air amount and the effective compression ratio in the decreasing direction by controlling the intake valve closing timing IVC as described above, even if the ignition timing reaches a predetermined delay limit, knocking may still occur. In an abnormal situation that cannot be dealt with by knock control, knock can be reliably avoided.
[0038]
When knocking does not occur (when there is no knocking), the process proceeds from step 1 to step 5.
In step 5, it is determined whether IVC = base IVC.
As a result, when the IVC is not the base IVC (when the knock control is performed by the IVC), the process proceeds to step 6, and the IVC is returned to the base IVC side by a predetermined value.
[0039]
When IVC = base IVC (when knock control by IVC is not performed), the process proceeds to step 7 to determine whether or not the ignition timing ADV is the base ignition timing ADVbase (ADV = base ADV).
[0040]
As a result, if ADV is not the base ADV, the process proceeds to step 8 to advance the ignition timing ADV by a predetermined value. Specifically, the ignition timing retard amount RET is decreased by a predetermined value ΔRET (RET = RET−ΔRET), and the retard amount RET is determined from the base ignition timing ADVbase determined by referring to the map from the engine speed Ne and the load TQ. By subtracting, the ignition timing ADV = ADVbase−RET is calculated and controlled.
[0041]
Needless to say, when ADV = base ADV, the ignition timing ADV is maintained at the base ignition timing ADVbase.
In this flow, the ignition timing ADV is converged to the base ignition timing ADVbase when knocking does not occur, but step 7 is omitted, and if IVC = base IVC as determined in step 5, go to step 8. By proceeding, the ignition timing ADV may be advanced to the knock limit when knock does not occur.
[0042]
Next, another embodiment of the present invention will be described.
In a high-octane gasoline engine, a map for high-octane gasoline set on the advance side is used as a map for setting the base ignition timing ADVbase compared to a regular gasoline map.
[0043]
FIG. 7 is a flowchart of a knock control routine in a high-octane gasoline engine. Steps 21 and 22 are added to the flow of FIG.
When the ignition timing ADV reaches a predetermined retardation limit due to continuous retardation (when the retardation amount RET ≧ predetermined value), the routine proceeds from step 2 to step 21.
[0044]
In step 21, it is determined whether or not the base ignition timing ADVbase setting map has already been switched from the high-octane gasoline map to the regular gasoline map (map switching has already been completed). Then switch to the regular gasoline map. This portion corresponds to the base ignition timing switching means.
[0045]
Accordingly, the ignition timing ADV = ADVbase′−RET is calculated and controlled by subtracting the current retard amount RET from the base ignition timing ADVbase ′ in the regular gasoline map, and the base ignition timing is used for high-octane gasoline. By switching from the base ignition timing to the base ignition timing for regular gasoline, it is possible to greatly retard the delay limit for regular gasoline.
[0046]
In this way, in a high-octane gasoline engine, when it is determined that the ignition timing has reached a predetermined retardation limit, it is assumed that regular gasoline is being used, and the base ignition timing is set to the base for high-octane gasoline. By switching from the ignition timing to the base ignition timing for regular gasoline, when using regular gasoline, the ignition timing is appropriately retarded to avoid knocking without shifting to valve timing control. It becomes possible.
[0047]
If the map has already been switched, that is, if knocking has occurred even if the map is switched and knocked, the process proceeds from step 21 to step 4.
In step 4, in order to avoid knocking at the retard limit, the valve timing of the intake valve 5 and the exhaust valve 6, in particular the intake valve closing timing IVC, is controlled in the decreasing direction of the intake air amount and the effective compression ratio by the variable valve device. (IVC control) Others are the same.
[Brief description of the drawings]
FIG. 1 is a functional block diagram showing the configuration of the present invention. FIG. 2 is a system diagram of an engine showing an embodiment of the present invention. FIG. 3 is a basic structural diagram of an electromagnetic drive device for intake and exhaust valves. Flowchart of routine [FIG. 5] Explanatory drawing of valve timing [FIG. 6] Flowchart of IVC control subroutine [FIG. 7] Flowchart of knock control routine showing another embodiment [Explanation of symbols]
1 Engine 4 Spark plug 5 Electromagnetically driven intake valve 6 Electromagnetically driven exhaust valve 9 Electric throttle valve 10 Fuel injection valve 11 Control unit 12 Crank angle sensor 13 Accelerator pedal sensor 14 Air flow meter 15 Knock sensor

Claims (5)

In a knock control device for an internal combustion engine comprising a knock detection means for detecting the occurrence of knock and an ignition timing correction control means for retarding the ignition timing when the knock occurs,
A retard limit determining means for determining that the ignition timing has reached a predetermined retard limit;
Valve timing control means for controlling the valve timing of the intake valve in the decreasing direction of the intake air amount and the effective compression ratio by a variable valve device when knocking occurs at the retard limit of the ignition timing;
While the Ru is provided,
When knocking does not occur, the valve timing control means gradually returns the valve timing to the base timing on the condition that the valve timing is controlled to decrease the intake air amount and the effective compression ratio with respect to the base timing. The ignition timing correction control means is configured to gradually advance the ignition timing on condition that the valve timing is at the base timing .   2. The knock control device for an internal combustion engine according to claim 1, wherein the valve timing control means controls the intake valve closing timing to be delayed from the bottom dead center when knocking occurs at the retard limit of the ignition timing. .   2. The knock control device for an internal combustion engine according to claim 1, wherein the valve timing control means controls the intake valve closing timing in a direction earlier than the bottom dead center when knocking occurs at the retard limit of the ignition timing. . The valve timing control means controls the intake valve closing timing to be advanced in a region where the base intake valve closing timing is at or before the bottom dead center when knocking occurs at the retard limit of the ignition timing. 2. The knock control device for an internal combustion engine according to claim 1, wherein the control is performed so that the intake valve closing timing is delayed in a region where the base intake valve closing timing is after bottom dead center. In an internal combustion engine of high-octane gasoline specifications, when it is determined by the retard limit determining means that the ignition timing has reached a predetermined retard limit, the base ignition timing is changed from the base ignition timing for high-octane gasoline to that for regular gasoline. 5. The knock control device for an internal combustion engine according to claim 1, further comprising base ignition timing switching means for switching to the base ignition timing.

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