JP6326728B2 - Control device and control method for internal combustion engine - Google Patents

Description

  The present invention relates to a control device and a control method for an internal combustion engine including an in-cylinder injection fuel injection valve that injects fuel into a combustion chamber and a port injection fuel injection valve that injects fuel into an intake port.

  In Patent Document 1, a fuel injection valve for in-cylinder injection that injects alcohol that is high-octane fuel into a combustion chamber and a fuel-injection valve for port injection that injects gasoline that is low-octane fuel into an intake port are used in combination. An internal combustion engine in which the sharing ratio between the two is appropriately controlled is disclosed.

  Further, in Patent Document 1, when the occurrence of knocking is detected by a knock sensor, the ratio of high-octane fuel is increased by increasing the ratio of in-cylinder injection, thereby suppressing the occurrence of knocking. It is disclosed. Also, in general, for the so-called spark knock, where the unburned mixture (end gas) far from the spark plug in the combustion chamber self-ignites all at once by adiabatic compression, the latent heat of vaporization by in-cylinder injection is effective in reducing knock. It is.

JP 2008-64055 A

  In-cylinder injection directly injects fuel into the combustion chamber, resulting in high spray penetration, and fuel and oil evaporate near the cylinder wall, especially when the engine is cold. There is a risk that they will mix together and cause a so-called super knock, which burns abnormally before the ignition timing.

  Such abnormal combustion (super knock) before the ignition timing caused by in-cylinder injection cannot be suppressed by increasing the share ratio of in-cylinder injection, unlike the normal spark knock described above. Increasing the share of injection increases the risk of abnormal combustion.

  It is an object of the present invention to provide a novel control device and control method for an internal combustion engine that can suppress the occurrence of abnormal combustion due to such in-cylinder injection.

  A cylinder injection fuel injection valve that injects fuel into the combustion chamber; and a port injection fuel injection valve that injects fuel into the intake port. When abnormal combustion before the ignition timing due to in-cylinder injection is detected and the abnormal combustion is detected, the share ratio of the in-cylinder injection is reduced and the share ratio of the in-cylinder injection is reduced. The share ratio of the port injection is increased so as to compensate for the decrease in the fuel injection amount.

  According to the present invention, when abnormal combustion (super knock) before the ignition timing due to in-cylinder injection is detected, the occurrence of such abnormal combustion is suppressed by reducing the share ratio of in-cylinder injection. While avoiding this, increasing the port injection share rate to compensate for the decrease in fuel injection amount accompanying the decrease in in-cylinder injection share rate ensures a fuel injection amount that meets the requirements and reduces torque fluctuations. It is possible to suppress the deterioration of engine operability.

BRIEF DESCRIPTION OF THE DRAWINGS Configuration explanatory drawing which shows the system configuration | structure of the control apparatus of the internal combustion engine which concerns on this invention. The flowchart which shows the flow of control in this Example. The timing chart which shows the operation | movement at the time of applying the control of the said Example.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows the system configuration of an automotive internal combustion engine 1 to which the present invention is applied. This internal combustion engine 1 is a spark ignition internal combustion engine with a turbocharger of a 4-stroke cycle equipped with a variable compression ratio mechanism 2 using, for example, a multi-link type piston crank mechanism. The intake valve 4 and a pair of exhaust valves 5 are disposed, and a spark plug 6 is disposed in a central portion surrounded by the intake valves 4 and the exhaust valves 5.

  A cylinder injection fuel injection valve 8 that directly injects fuel into the combustion chamber 3 is disposed below the intake port 7 that is opened and closed by the intake valve 4. The intake port 7 is provided with a port injection fuel injection valve 41 that injects fuel into the intake port 7. These in-cylinder injection fuel injection valve 8 and port injection fuel injection valve 41 are both electromagnetic or piezoelectric injection valves that are opened when a drive pulse signal is applied. An amount of fuel that is substantially proportional to the pulse width is injected.

  An electronically controlled throttle valve 19 whose opening degree is controlled by a control signal from the engine controller 9 is interposed on the upstream side of the collector portion 18a of the intake passage 18 connected to the intake port 7, and further upstream thereof. On the side, a turbocharger compressor 20 is arranged. An air flow meter 10 that detects the intake air amount is disposed upstream of the compressor 20.

  In addition, a catalyst device 13 made of a three-way catalyst is interposed in the exhaust passage 12 connected to the exhaust port 11, and an air-fuel ratio sensor 14 for detecting the air-fuel ratio is disposed upstream thereof.

  Further, a knock sensor 42 for detecting the occurrence of so-called super knock (vibration resulting from this), which is abnormal combustion before the ignition timing due to in-cylinder injection, is attached to the cylinder block 29. Super knock is a fuel spray of droplets injected and supplied directly into the combustion chamber by in-cylinder injection, mixed with oil in the vicinity of the cylinder wall, or mixed with oil expelled by fuel spray, and this is used as a heat source for ignition timing This is a phenomenon that causes abnormal combustion before, and is particularly likely to occur when the engine is cold at low engine temperatures.

  In addition to the air flow meter 10, the air-fuel ratio sensor 14 and the knock sensor 42, the engine controller 9 includes a crank angle sensor 15 for detecting the engine speed, a water temperature sensor 16 for detecting the cooling water temperature, and an operation by the driver. Detection signals of sensors such as an accelerator opening sensor 17 that detects the amount of depression of the accelerator pedal are input. Based on these detection signals, the engine controller 9 optimally controls the fuel injection amount and injection timing by the fuel injection valves 8 and 41, the ignition timing by the spark plug 6, the opening of the throttle valve 19, and the like.

  On the other hand, the variable compression ratio mechanism 2 uses a known multi-link type piston crank mechanism, and includes a lower link 22 rotatably supported by a crank pin 21 a of the crankshaft 21 and one end of the lower link 22. An upper link 25 for connecting the upper pin 23 of the part and the piston pin 24a of the piston 24, a control link 27 having one end connected to the control pin 26 at the other end of the lower link 22, and the other end of the control link 27 And a control shaft 28 that supports the shaft in a swingable manner. The crankshaft 21 and the control shaft 28 are rotatably supported in a crankcase below the cylinder block 29 via a bearing structure (not shown). The control shaft 28 has an eccentric shaft portion 28a whose position changes with the rotation of the control shaft 28. Specifically, the end portion of the control link 27 is rotatably fitted to the eccentric shaft portion 28a. Match. In the variable compression ratio mechanism 2 described above, the top dead center position of the piston 24 is displaced up and down with the rotation of the control shaft 28, so that the mechanical compression ratio changes.

  As a drive mechanism for variably controlling the compression ratio of the variable compression ratio mechanism 2, an electric motor 31 having a rotation center axis parallel to the crankshaft 21 is disposed below the cylinder block 29. A reduction gear 32 is connected so as to be arranged in series in the direction. As the speed reducer 32, for example, a wave gear mechanism having a large speed reduction ratio is used, and the speed reducer output shaft 32 a is positioned coaxially with the output shaft (not shown) of the electric motor 31. Accordingly, the speed reducer output shaft 32a and the control shaft 28 are positioned in parallel with each other, and the first arm 33 and the control shaft 28 fixed to the speed reducer output shaft 32a are connected to each other so that both of them rotate in conjunction with each other. The fixed second arm 34 is connected to each other by an intermediate link 35.

  That is, when the electric motor 31 rotates, the angle of the speed reducer output shaft 32a changes in a form greatly decelerated by the speed reducer 32. The rotation of the speed reducer output shaft 32a is transmitted from the first arm 33 to the second arm 34 via the intermediate link 35, and the control shaft 28 rotates. Thereby, as mentioned above, the mechanical compression ratio of the internal combustion engine 1 changes. In the illustrated example, the first arm 33 and the second arm 34 extend in the same direction. Therefore, for example, when the speed reducer output shaft 32a rotates in the clockwise direction, the control shaft 28 also rotates in the clockwise direction. Although it is related, the link mechanism can also be configured to rotate in the opposite direction.

  The target compression ratio of the variable compression ratio mechanism 2 is set in the engine controller 9 based on engine operating conditions (for example, required load and engine speed), and the electric motor 31 is driven so as to realize this target compression ratio. Be controlled.

  Next, FIG. 2 is a flowchart showing a flow of control performed for super knock suppression in the configuration of the above embodiment. This routine is repeatedly executed in the engine controller 9, for example, at predetermined time intervals or at intervals corresponding to the ignition intervals of each cylinder.

  In step S <b> 1, it is determined based on the detection signals of the knock sensor 42 and the crank angle sensor 15 whether a super knock-occurring cylinder has been detected. If the occurrence of super knock is not detected, this routine is terminated. If the occurrence of super knock is detected, the process proceeds to step S2 and subsequent steps.

  In step S2, the share ratio between in-cylinder injection and port injection is changed and corrected for the cylinder in which the occurrence of super knock is detected. In other words, the ratio of in-cylinder injection is decreased, and the ratio of port injection is increased so as to compensate for the decrease in the fuel injection amount accompanying the decrease in the ratio of in-cylinder injection (abnormal combustion suppression means).

  In this case, the sharing ratio to be changed / corrected is a piston that changes in accordance with the compression ratio in the case of the configuration including the variable compression ratio mechanism 8 in addition to the penetration of the in-cylinder injection fuel injection valve 8. The changed sharing rate is set in consideration of the positional relationship between the cylinder bore and the cylinder bore.

  In addition, in the operation region in which operation by only port injection is possible, in order to reliably suppress the occurrence of super knock caused by in-cylinder injection, in-cylinder injection is stopped, that is, the share ratio of in-cylinder injection is reduced to 0. %, And the port injection share is 100%, and the entire amount of combustion injection is injected by this port injection.

  In step S3, the compression ratio is corrected to the lower side in accordance with the change / correction of the sharing ratio. This is because the latent heat of vaporization due to in-cylinder injection decreases as the share of in-cylinder injection decreases, and the risk of normal spark knock increases, so that the occurrence of this normal spark knock is suppressed. Reduce compression ratio.

  Similarly, in step S4, the ignition timing is corrected to the retard side so as to suppress the occurrence of normal spark knock accompanying the change / correction of the sharing ratio. The retard amount of the ignition timing at this time is increased as the increase in the share of port injection increases.

  In this embodiment, both the compression ratio and the ignition timing are performed in accordance with the change of the sharing ratio, but either one may be performed.

  In step S5, it is determined whether or not the occurrence of abnormal combustion has been sufficiently suppressed / avoided based on operating conditions such as the detection signal of the knock sensor 42, the intake air temperature, and the oil / water temperature. If it is determined that the occurrence of abnormal combustion is suppressed / avoided, the process proceeds to step S6, and the changed / corrected sharing ratio, compression ratio, and ignition timing are returned to normal values.

  FIG. 3 is a timing chart in the case where the control of this embodiment is applied. As shown in the figure, when the occurrence of super knock before the ignition timing t2 is detected, in the fuel injection after the next detection cylinder, in-cylinder injection (GDI pulse) is stopped and port injection (MPI) is performed instead. Pulse). Further, the compression ratio is reduced and the ignition timing is corrected to the retard side. In this embodiment, the compression ratio with low responsiveness is decreased immediately after the detection of abnormal combustion from t2, and the ignition timing retardation with high responsiveness is performed from t3 after the sharing ratio change. For example, when the responsiveness of the compression ratio is high, the compression ratio may be decreased from t3 immediately after the share ratio change.

  [1] As described above, in the present embodiment, when abnormal combustion (super knock) before the ignition timing due to in-cylinder injection is detected, such an abnormality is reduced by reducing the share ratio of in-cylinder injection. While suppressing and avoiding the occurrence of combustion, increasing the port injection share ratio to compensate for the decrease in fuel injection quantity accompanying the decrease in the in-cylinder injection share ratio, the fuel injection quantity meeting the requirements can be increased. It is possible to secure and suppress the torque fluctuation to suppress the deterioration of the engine operability.

  [2] In particular, when operation by only port injection is possible, when abnormal combustion is detected, in-cylinder injection is completely stopped, and the entire amount of combustion injection is injected by port injection, thereby causing abnormal combustion. Can be more reliably suppressed.

  [3] Further, in the configuration provided with the variable compression ratio mechanism 2 that makes the mechanical compression ratio of the internal combustion engine variable, the compression ratio is reduced according to the reduction of the share ratio of the in-cylinder injection when the abnormal combustion is detected. Let As a result, the increase in the risk of occurrence of a normal spark knock due to a decrease in the latent heat of vaporization accompanying the decrease in in-cylinder injection can be offset / reduced by the decrease in the compression ratio, and the occurrence of spark knock can be suppressed.

  [4] Similarly, when abnormal combustion is detected, the ignition timing is retarded in accordance with the decrease in the in-cylinder injection share rate, thereby suppressing the occurrence of normal spark knock associated with the decrease in in-cylinder injection. it can.

  [5] Further, when it is possible to identify the cylinder in which the abnormal combustion has occurred, only the cylinder in which the abnormal combustion has occurred is changed / corrected for the in-cylinder injection ratio, and the other cylinders are changed / corrected. By adopting such a configuration, fluctuations in engine operability can be minimized.

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Variable compression ratio mechanism 6 ... Spark plug 8 ... Fuel injection valve for cylinder injection 9 ... Engine controller 14 ... Air fuel ratio sensor 20 ... Compressor 41 ... Fuel injection valve for port injection 42 ... Knock sensor (abnormal combustion) Detection means)

Claims (6)

A fuel injection valve for in-cylinder injection that injects fuel into the combustion chamber; and a fuel injection valve for port injection that injects fuel into the intake port. In the control device for the internal combustion engine set according to
Abnormal combustion detection means for detecting abnormal combustion before the ignition timing due to the in-cylinder injection;
When the abnormal combustion is detected, the share ratio of the in-cylinder injection is decreased, and the share ratio of the port injection is increased so as to compensate for the decrease in the fuel injection amount accompanying the decrease in the share ratio of the in-cylinder injection. Abnormal combustion suppression means to
A control apparatus for an internal combustion engine, comprising:   2. The internal combustion engine according to claim 1, wherein when the abnormal combustion is detected, the abnormal combustion suppressing means stops the in-cylinder injection and injects the entire combustion injection amount by the port injection. Control device. A variable compression ratio mechanism for a pressure Chijimihi of the internal combustion engine variable,
The control apparatus for an internal combustion engine according to claim 1 or 2, wherein the abnormal combustion suppressing means reduces the compression ratio when the abnormal combustion is detected.
  The said abnormal combustion suppression means retards an ignition timing according to the increase in the share of the said port injection, when the said abnormal combustion is detected, The ignition timing of any one of Claims 1-3 characterized by the above-mentioned. Control device for internal combustion engine. The abnormal combustion detection means identifies the cylinder in which the abnormal combustion has occurred,
The abnormal combustion suppressing means reduces the share ratio of the in-cylinder injection only for the cylinder in which the abnormal combustion has occurred, and compensates for a decrease in the fuel injection amount accompanying a decrease in the share ratio of the in-cylinder injection. The control device for an internal combustion engine according to any one of claims 1 to 4, wherein a share ratio of port injection is increased. A fuel injection valve for in-cylinder injection that injects fuel into the combustion chamber; and a fuel injection valve for port injection that injects fuel into the intake port. In the control method of the internal combustion engine configured accordingly,
Detecting abnormal combustion before the ignition timing due to the in-cylinder injection,
When the abnormal combustion is detected, the share ratio of the in-cylinder injection is decreased, and the share ratio of the port injection is increased so as to compensate for the decrease in the fuel injection amount accompanying the decrease in the share ratio of the in-cylinder injection. A control method for an internal combustion engine.

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