JP5772702B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine that can change the operating angle of an exhaust valve.

  Conventionally, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2009-150320, a variable valve system capable of switching a plurality of cams having different operating angles and a part of exhaust gas passing through an exhaust system are recirculated to an intake system. A system including an external EGR is known. In this system, there are two types: a first mode in which a first cam having a normal operating angle is used and an external EGR is used together, and a second mode in which a second cam having a smaller operating angle is used and an internal EGR is used in combination. The mode can be switched. The fuel consumption is improved by switching these modes in accordance with the temperature of the internal combustion engine.

JP 2009-150320 A

  By the way, when the cam for changing the operating angle of the exhaust valve is switched to a cam having a smaller operating angle, the ignition timing is changed to a more advanced value corresponding to the small operating angle. Here, if the working angle of the exhaust valve is reduced during execution of the exhaust gas recirculation (EGR) operation, the high temperature exhaust gas at the large working angle is recirculated as EGR gas for several cycles immediately after switching. In this case, the intake air temperature in the cylinder rises more than the assumption of a small working angle, and there is a possibility that knocking may occur due to a combination with the ignition timing on the more advanced side.

  The present invention has been made to solve the above-described problems, and effectively suppresses the occurrence of knocking in an internal combustion engine in which the exhaust gas recirculation operation and the exhaust valve operating angle variable operation are performed simultaneously. It is an object of the present invention to provide a control device for an internal combustion engine that can be used.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
An operating angle variable mechanism capable of switching the operating angle of the exhaust valve of the internal combustion engine in at least two stages;
An exhaust gas recirculation device for recirculating a part of the burned gas exhausted from the cylinder of the internal combustion engine into the cylinder;
An ignition device capable of changing the ignition timing of the internal combustion engine;
The operating angle variable mechanism and the ignition device are operated to switch the operating angle of the exhaust valve from a predetermined large operating angle to a predetermined small operating angle, and the ignition timing is advanced according to the small operating angle. Control means for changing to the ignition timing of
The control means performs an operation of changing the ignition timing by the ignition device after a predetermined period of time has elapsed after the switching operation by the variable operating angle mechanism during a period in which the exhaust gas recirculation operation is being performed by the exhaust gas recirculation device. It is characterized by doing.

According to a second invention, in the first invention,
The predetermined period is a period until the burned gas after switching to the small working angle is recirculated into the cylinder by the exhaust gas recirculation device.

  According to the first invention, the operating angle variable mechanism and the ignition device are operated to switch the operating angle of the exhaust valve from the predetermined large operating angle to the predetermined small operating angle, and the ignition timing corresponds to the small operating angle. In the control to change to the ignition timing on the advance side, if the control is executed during the period in which the exhaust gas recirculation operation is being performed by the exhaust gas recirculation device, a predetermined period elapses after the switching operation by the working angle variable mechanism After that, the ignition timing is changed by the ignition device. If the operating angle of the exhaust valve is switched to a small operating angle during the exhaust gas recirculation operation, the high-temperature burned gas exhausted from the cylinder before switching will be returned to the cylinder for several cycles after the switching. It becomes. According to the present invention, after the switching operation by the working angle variable mechanism, the ignition timing is changed to the advance side after a predetermined period has elapsed, so that the ignition is performed in a state where the intake air temperature in the cylinder is higher than expected. It is possible to effectively suppress the occurrence of knocking due to advance of the timing.

  According to the second aspect of the invention, the ignition timing changing operation is performed after a period in which the burned gas exhausted from the cylinder after the switching to the small working angle is returned to the cylinder by the exhaust gas recirculation apparatus has elapsed. For this reason, according to the present invention, it is possible to avoid the ignition timing from being changed to the advance side when the intake air temperature in the cylinder is higher than expected, so that the occurrence of knocking can be effectively suppressed. Can do.

It is a figure for demonstrating the structure of the system of embodiment of this invention. It is a figure which shows the lift amount and working angle of the exhaust valve for every exhaust cam. It is a figure which shows the relationship between the operation area | region of an internal combustion engine, and a working angle. It is a figure which shows the in-cylinder temperature with respect to a crank angle. It is a timing chart which shows the timing of the operation | movement of a working angle variable mechanism in the EGR introduction | transduction area | region, and the variable operation of ignition timing.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted. The present invention is not limited to the following embodiments.

Embodiment.
[Configuration of the embodiment]
FIG. 1 is a diagram for explaining the configuration of a system according to an embodiment of the present invention. The system shown in FIG. 1 includes an internal combustion engine 10 mounted on a vehicle. The internal combustion engine 10 of the present embodiment is assumed to be an in-line four cylinder type. FIG. 1 shows a cross section of one of the cylinders. A piston 12 is provided in each cylinder of the internal combustion engine 10. An intake passage 14 and an exhaust passage 16 communicate with each cylinder.

  In the middle of the intake passage 14, an electronically controlled throttle valve 18 and a surge tank 20 are provided. The surge tank 20 is disposed on the downstream side of the throttle valve 18. An air flow meter 22 that detects the intake air amount is installed on the upstream side of the throttle valve 18. An exhaust purification catalyst 26 that purifies exhaust gas is disposed in the exhaust passage 16.

  Each cylinder of the internal combustion engine 10 is provided with a fuel injector 28 for injecting fuel into the intake port, an ignition plug 30 for igniting an air-fuel mixture in the combustion chamber, an intake valve 32, and an exhaust valve 34. Yes. A crank angle sensor 36 for detecting the rotation angle (crank angle) of the crankshaft 24 is provided in the vicinity of the crankshaft 24 of the internal combustion engine 10. An accelerator position sensor 44 for detecting the accelerator pedal position is provided in the vicinity of the accelerator pedal.

  Further, the internal combustion engine 10 includes an EGR device 40 for performing so-called EGR, in which a part of the exhaust gas in the exhaust passage 16 is recirculated to the intake passage 14. The EGR device 40 is provided in the middle of the EGR passage 46 having one end connected to the exhaust passage 16 and the other end connected to the intake passage 14 on the downstream side of the surge tank 20, and the EGR passage 46. And an EGR valve 48 for controlling the exhaust gas recirculation amount by opening and closing the valve.

  The exhaust valve 34 is provided with a variable working angle mechanism 38 that changes a valve opening period (working angle) that is a valve opening characteristic of the exhaust valve 34. The working angle variable mechanism 38 in the present embodiment is a mechanism that changes the working angle in two stages together with the lift amount of the exhaust valve 34 by switching two exhaust cams. Hereinafter, in the present embodiment, the working angle variable mechanism 38 will be described focusing on a mechanism that changes the valve working angle in two stages together with the lift amount of the exhaust valve 34. However, the working angle variable mechanism 38 that can be applied to the present invention is described. As long as the operating angle can be changed in at least two stages, the mechanism is not particularly limited. That is, as the operating angle variable mechanism 38, for example, a mechanism that can change the valve operating angle in three or more stages by providing three or more exhaust cams may be applied, or by rotating the control shaft. A mechanism that can continuously change the operating angle may be applied.

  The internal combustion engine system of the present embodiment includes an ECU (Electronic Control Unit) 50. The various sensors described above are connected to the input side of the ECU 50. Various actuators such as the above-described EGR valve 48, spark plug 30, working angle variable mechanism 38 and the like are connected to the output side of the ECU 50. The ECU 50 can control the operating state of the internal combustion engine 10 based on those sensor outputs.

[Operation of the embodiment]
As described above, the system of the present embodiment includes the operating angle variable mechanism 38 that can switch the operating angle of the exhaust valve 34 in two stages by switching between the two exhaust cams. FIG. 2 is a diagram showing the lift amount and operating angle of the exhaust valve for each exhaust cam. As shown in this figure, the exhaust cam of the system of the present embodiment has an exhaust cam corresponding to a small working angle with a small lift amount and working angle of the exhaust valve 34, and a large lift amount and valve working angle of the exhaust valve 34. And an exhaust cam corresponding to a large working angle. The profile of the exhaust cam for the small working angle is defined so that the exhaust opening timing EVO is retarded as compared with the exhaust cam for the large working angle.

  The operating angle variable mechanism 38 is controlled according to the operating state of the internal combustion engine 10. FIG. 3 is a diagram showing the relationship between the operating range of the internal combustion engine and the operating angle. As shown in this figure, the operating region of the internal combustion engine 10 is divided into a region on the low rotation / low load side where a small operating angle is used and a region on the high rotation / high load side where a large action is used. Therefore, first, the engine speed and the engine load are calculated using the air flow meter 22, the crank angle sensor 36, the accelerator position sensor 44, and the like, and the operating state specified from these values is changed from the region of the large operating angle to the small operating angle. When shifting to the region (for example, at the time of deceleration), the switching operation by the working angle variable mechanism 38 is performed.

  Further, in the system of the present embodiment, when the working angle of the exhaust valve 34 is switched by the working angle variable mechanism 38, the ignition timing by the spark plug 30 is accordingly reduced from the adapted value corresponding to the large working angle. The value can be changed to a compatible value corresponding to the working angle. Specifically, when the operating angle of the exhaust valve 34 is switched from the large operating angle to the small operating angle, the optimum ignition timing corresponding to the small operating angle is advanced from the ignition timing corresponding to the large operating angle. It can be changed to the matching value on the corner side.

  Furthermore, in the system according to the present embodiment, an exhaust gas recirculation operation for the purpose of improving fuel efficiency is performed. Specifically, the EGR valve 48 is opened when the operating state of the internal combustion engine 10 belongs to the EGR introduction region shown in FIG. As a result, the burnt gas exhausted from the cylinder to the exhaust passage 16 is returned to the intake passage 14 via the EGR passage 46. The recirculated burned gas (EGR gas) is sucked into the cylinder of the internal combustion engine 10 together with fresh air and is used for combustion.

  Here, when the operating angle of the exhaust valve 34 is switched from the large operating angle to the small operating angle, the temperature of the burned gas exhausted from the cylinder also changes. FIG. 4 is a diagram showing the in-cylinder temperature with respect to the crank angle. As described above, when the operating angle of the exhaust valve 34 is switched from the large operating angle to the small operating angle, the exhaust opening timing EVO is retarded. For this reason, as shown in this figure, the burnt gas exhausted when the operating angle of the exhaust valve 34 is a large operating angle is higher in temperature than that exhausted when the operating angle is a small operating angle. Therefore, when the operating angle of the exhaust valve 34 is switched from the large operating angle to the small operating angle in the EGR introduction region, the high-temperature burned gas exhausted from the cylinder at the large operating angle in several cycles after switching. Is recirculated into the cylinder. In this case, the intake air temperature in the cylinder rises more than expected at the small working angle, and there is a possibility that knocking may occur due to the combination with the appropriate value of the ignition timing at the small working angle.

  Therefore, in the system of the present embodiment, when the operating angle of the exhaust valve 34 is switched from the large operating angle to the small operating angle in the EGR introduction region, the ignition timing variable timing is delayed. FIG. 5 is a timing chart showing the timing of the operation of the variable working angle mechanism and the variable operation of the ignition timing in the EGR introduction region. As shown in this figure, when the operating angle of the exhaust valve 34 is switched from a large operating angle to a small operating angle, the ignition timing is maintained for a predetermined period after switching, with the ignition timing adapted to the large operating angle. The ignition timing is changed to an appropriate value corresponding to the small operating angle after a predetermined period. Thereby, it is possible to effectively suppress the occurrence of knocking immediately after the switching.

  It should be noted that the period during which the ignition timing is maintained after switching the operating angle is preferably set to a period until the burned gas exhausted from the cylinder at the small operating angle is recirculated into the cylinder as EGR gas. As a result, it is possible to avoid the ignition timing from being changed to the advance side when the intake air temperature in the cylinder is higher than expected, so that the occurrence of knocking can be effectively suppressed.

  By the way, in the present embodiment, when the operating angle of the exhaust valve 34 is switched from the large operating angle to the small operating angle in the EGR introduction region, the variable operation of the ignition timing is delayed for a predetermined period. May be limited to a region where knocking is likely to occur. Thereby, it is possible to effectively avoid a situation in which unnecessary control is performed.

  Further, in the present embodiment, the working angle variable mechanism 38 configured so that the exhaust opening timing EVO of the small working angle is retarded from that of the large working is used. However, the exhaust of the small working angle is used. A working angle variable mechanism configured such that the closing timing EVC is advanced more than that of the large action may be used.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Piston 14 Intake passage 16 Exhaust passage 18 Throttle valve 20 Surge tank 22 Air flow meter 24 Crankshaft 26 Exhaust purification catalyst 28 Fuel injector 30 Spark plug 32 Intake valve 34 Exhaust valve 36 Crank angle sensor 38 Working angle variable mechanism 40 EGR Device 44 Accelerator position sensor 46 EGR passage 48 EGR valve 50 ECU (Electronic Control Unit)

Claims (2)

An operating angle variable mechanism capable of switching the operating angle of the exhaust valve of the internal combustion engine in at least two stages;
An exhaust gas recirculation device for recirculating a part of the burned gas exhausted from the cylinder of the internal combustion engine into the cylinder;
An ignition device capable of changing the ignition timing of the internal combustion engine;
The operating angle variable mechanism and the ignition device are operated to switch the operating angle of the exhaust valve from a predetermined large operating angle to a predetermined small operating angle, and the ignition timing is advanced according to the small operating angle. Control means for changing to the ignition timing of
The control means performs an operation of changing the ignition timing by the ignition device after a predetermined period of time has elapsed after the switching operation by the variable operating angle mechanism during a period in which the exhaust gas recirculation operation is being performed by the exhaust gas recirculation device. A control device for an internal combustion engine.   The predetermined period is a period until a part of burned gas exhausted from the cylinder after switching to the small working angle is returned to the cylinder by the exhaust gas recirculation device. Item 2. A control device for an internal combustion engine according to Item 1.

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