JP2006070869A - Control device for variable cylinder internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce exhaust emission of a variable cylinder internal combustion engine. <P>SOLUTION: In a control device for the variable cylinder internal combustion engine provided with a plurality of cylinders 2A, 2B and selectively performing all cylinder operation performing combustion in all cylinders and reduced cylinder operation performing combustion on part of the cylinders according to an engine operation condition, an intake valve 15 and an exhaust valve 17 of a cylinder in which combustion is not performed are actuated to make exhaust gas in exhaust passages 5B, 6B flow in the cylinder 2B in which combustion is not performed and to make the exhaust gas flowing in the cylinder discharged to intake passages 3A, 4A during reduced cylinder operation. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a control device for a variable cylinder internal combustion engine.

  An all-cylinder operation in which a plurality of cylinders are provided and combustion is performed in all of these cylinders, and a reduced-cylinder operation in which combustion is performed only in some of these cylinders are selectively performed according to the engine operation state. A variable cylinder internal combustion engine is disclosed in Patent Document 1.

Japanese Utility Model Publication No. 5-42652 JP 2001-132484 A

  An object of the present invention is to reduce exhaust emission in a variable cylinder internal combustion engine as described above.

  In order to solve the above-described problem, in the first invention, the entire cylinder operation in which a plurality of cylinders are provided and combustion is performed in all the cylinders and the reduced cylinder operation in which combustion is performed only in some of the cylinders are performed. In the control apparatus for a variable cylinder internal combustion engine that selectively executes the following in accordance with the engine operating state, during the reduced-cylinder operation, the exhaust gas flows from the exhaust passage into the cylinder where combustion is not performed, The intake and exhaust valves of the cylinders that are not combusted are operated so as to be discharged into the intake passage.

  In order to solve the above-mentioned problem, in the second invention, a multi-cylinder operation in which a plurality of cylinders are provided and combustion is performed in all the cylinders, and a reduced-cylinder operation in which combustion is performed only in some of the cylinders. In a control device for a variable cylinder internal combustion engine that selectively executes the above in accordance with the engine operating state, when an increase in the amount of exhaust gas supplied to the cylinder that is performing the reduced cylinder operation and is being combusted is requested In addition, the intake valve and the exhaust valve of the non-combusted cylinder are operated so that the exhaust gas flows into the non-combusted cylinder from the exhaust passage and the exhaust gas that has flowed into the intake passage is discharged. It is done.

  In order to solve the above-mentioned problem, in the third aspect of the invention, there is provided a plurality of cylinders, all-cylinder operation in which combustion is performed in all of these cylinders, and reduced-cylinder operation in which combustion is performed only in some of these cylinders. In the control device for a variable cylinder internal combustion engine that selectively executes the control according to the engine operating state, the first exhaust passage connected to the cylinder that performs combustion during the reduced cylinder operation and the combustion during the reduced cylinder operation The second exhaust passage connected to the non-performed cylinder is a separate exhaust passage, and an exhaust purification catalyst for purifying the exhaust gas is disposed in the second exhaust passage, and the second exhaust passage downstream of the exhaust purification catalyst is disposed. A cylinder in which one exhaust passage and the second exhaust passage are connected to each other, and combustion is not performed when the temperature of the exhaust purification catalyst becomes lower than a predetermined temperature during the reduced-cylinder operation. Exhaust gas from the exhaust passage Combustion and the intake valve of the cylinder is not performed and the exhaust valve is actuated to exhaust gas the flows are discharged into the intake passage and.

  In order to solve the above problem, in the fourth invention, in the first to third inventions, combustion is not performed when the intake valve of the cylinder in which combustion is performed is opened during the reduced-cylinder operation. When the exhaust valve of the cylinder is opened and the exhaust valve of the cylinder where the combustion is performed is opened, the intake valve of the cylinder where the combustion is not performed is opened, so that the combustion is performed. Exhaust gas flows into the cylinders that do not exist from the exhaust passage, and the exhaust gas that has flowed in is discharged into the intake passage.

  According to the first and second aspects of the invention, exhaust gas is discharged into the intake passage from a cylinder that is not combusted during the reduced-cylinder operation, so that the intake passage is connected to the cylinder that is combusted during the reduced-cylinder operation. Exhaust gas will be sucked from. According to this, the exhaust emission in the cylinder in which the combustion is performed during the reduced-cylinder operation is reduced due to the property of the exhaust gas as the inert gas.

  According to the third aspect of the invention, during the reduced-cylinder operation, the exhaust passage connected to the non-combusted cylinder passes through the non-combusted cylinder to the non-combusted cylinder. A flow of exhaust gas flowing into the connected intake passage is generated. For this reason, during the reduced-cylinder operation, the relatively high-temperature exhaust gas discharged from the cylinder in which combustion is performed flows into the exhaust purification catalyst. Thereby, even during the reduced-cylinder operation, the temperature of the exhaust purification catalyst is maintained relatively high and the activity of the exhaust purification catalyst is maintained in a high state, so when switching from reduced-cylinder operation to all-cylinder operation The exhaust gas discharged from the cylinders that have not been combusted during the reduced-cylinder operation is favorably purified by the exhaust purification catalyst.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a variable cylinder internal combustion engine to which the present invention is applied. In FIG. 1, reference numerals 1A and 1B denote engine bodies. One engine body (hereinafter also referred to as “first engine body”) 1A includes four cylinders (combustion chambers) 2A. A corresponding intake branch pipe 3A is connected to each cylinder 2A. These intake branch pipes 3A are connected to one intake passage 4A. Each cylinder 2A is connected to a corresponding exhaust branch pipe 5A. These exhaust branch pipes 5A are connected to one exhaust passage 6A. A catalyst 7A for purifying exhaust gas (hereinafter referred to as “exhaust purification catalyst”) 7A is disposed in the exhaust passage 6A.

  The other engine body (hereinafter referred to as “second engine body”) 1B also includes four cylinders (combustion chambers) 2B. A corresponding intake branch pipe 3B is also connected to each cylinder 2B. These intake branch pipes 3B are also connected to one intake passage 4B. Also, the corresponding exhaust branch pipes 5B are connected to the respective cylinders 2B. These exhaust branch pipes 5B are also connected to one exhaust passage 6B. A catalyst (exhaust purification catalyst) 7B for purifying exhaust gas is also disposed in the exhaust passage 6B.

  The intake passage 4A of the first engine body 1A and the intake passage 4B of the second engine body 1B are connected to one intake pipe 8. A throttle valve 9 is disposed in the intake pipe 8. On the other hand, the exhaust passage 6A of the first engine body 1A and the exhaust passage 6B of the second engine body 1B are connected to one exhaust pipe 10.

  FIG. 2 shows one of the cylinders of the internal combustion engine of FIG. In FIG. 2, 11 is a cylinder head, 12 is a cylinder block, 13 is a piston, 14 is a combustion chamber, 15 is an intake valve, 16 is an intake port, 17 is an exhaust valve, 18 is an exhaust port, 19 is a fuel injection valve, 20 Indicates a spark plug. A drive device (hereinafter referred to as “drive device for intake valve”) 21 for opening and closing the intake valve 15 is attached to the intake valve 15. The intake valve drive device 21 can open or close the intake valve 15 at any timing. On the other hand, a drive device (hereinafter referred to as “exhaust valve drive device”) 22 for opening and closing the exhaust valve 17 is attached to the exhaust valve 17. The exhaust valve drive device 22 can also open or close the exhaust valve 17 at any timing.

  By the way, in the embodiment of the present invention, the engine operation is controlled based on the map of FIG. That is, in the region I where the engine speed N is relatively small and the required load L is relatively small, fuel is injected from the fuel injection valves 19 corresponding to the four cylinders 2A of the first engine body 1A. The fuel is ignited by the spark plug 20 to cause combustion, and the fuel injection valve 19 corresponding to the four cylinders 2B of the second engine body 1B does not perform combustion injection, and therefore does not perform combustion (hereinafter referred to as engine operation). "Reduced cylinder operation") is performed.

  On the other hand, in the region II other than the region I, the fuel is injected from the fuel injection valves 19 corresponding to all the cylinders 2A and 2B of both the engine main bodies 1A and 1B, and the fuel is ignited by the spark plugs 20 of these cylinders 2A and 2B. Then, engine operation for causing combustion (hereinafter referred to as “all cylinder operation”) is performed.

  More specifically, in the first embodiment of the present invention, when the engine operating state is in the region I in FIG. 3 and the reduced-cylinder operation is performed, the cylinder of the first engine main body 1A in which combustion is performed (hereinafter referred to as the cylinder operation) 2A) (referred to as “working cylinder”), fuel is injected from the fuel injection valve 19 corresponding to the working cylinder 2A in the normal intake stroke, and the intake valve 15 of the working cylinder 2A is indicated by IN1 in FIG. 4 is opened, air and fuel are sucked into each cylinder 2A from the intake branch pipe 3A, and the spark plug 20 of the working cylinder 2A is operated at a timing near the compression top dead center to ignite the fuel, as shown in FIG. As indicated by EX1, in the normal exhaust stroke, the exhaust valve 17 is opened, and the exhaust gas is discharged from each operating cylinder 2A to the exhaust branch pipe 5A.

  On the other hand, in the cylinder 2B of the second engine body 1B in which combustion is not performed during the reduced-cylinder operation (hereinafter referred to as “pause cylinder”) 2B, fuel is supplied from the fuel injection valve 19 corresponding to the pause cylinder 2B in the normal intake stroke. 4 is not injected, but the exhaust valve 17 is opened as indicated by IN2 in FIG. 4, whereby the exhaust gas is sucked into each idle cylinder 2B from the exhaust branch pipe 5B, and then EX2 in FIG. As shown in FIG. 4, the intake valve 15 is opened in the normal exhaust stroke, and thereby exhaust gas is discharged from each idle cylinder 2B to the intake branch pipe 3A (of course, ignition corresponding to the idle cylinder 2B). The plug 20 is not activated).

According to this, the exhaust gas discharged from the deactivated cylinder 2B to the intake branch pipe 3B connected to the deactivated cylinder 2B is sucked into the active cylinder 2A via the intake passages 4B and 4A and the intake branch pipe 3A. become. Since the exhaust gas contains an inert gas such as CO ₂ , this inert gas lowers the combustion temperature in the operating cylinder 2A and suppresses the generation of nitrogen oxides (NOx). . That is, exhaust emission is reduced.

  Further, according to this, a flow of exhaust gas flowing from the exhaust branch pipe 3B connected to the idle cylinder 2B through the idle cylinder 2B to the intake branch pipe 3B connected to the idle cylinder 2B is generated. Therefore, at least the high-temperature exhaust gas discharged from the operating cylinder 2A to the exhaust passage 5A flows into the exhaust purification catalyst 7B corresponding to the second engine main body (rest cylinder 2B). Therefore, the temperature of the exhaust purification catalyst 7B (hereinafter referred to as “catalyst temperature”) is raised by the heat of the exhaust gas flowing into the exhaust purification catalyst 7B. This increases the possibility that the temperature of the exhaust purification catalyst 7B corresponding to the second engine main body (paused cylinder 2B) is maintained at or above its activation temperature. For this reason, immediately after the engine operation is switched from the reduced-cylinder operation to the all-cylinder operation, there is a high possibility that the temperature of the exhaust purification catalyst 7B corresponding to the second engine body (stop cylinder 2B) is maintained at the activation temperature or higher. As a result, exhaust emissions are reduced.

  Further, according to this, also in the idle cylinder 2B, the exhaust gas flows from the exhaust branch pipe into each idle cylinder 2B in the intake stroke, and the exhaust gas is discharged from each idle cylinder 2B to the intake branch pipe 3B in the exhaust stroke. Therefore, the pumping loss in the idle cylinder 2B is reduced.

  In the above description, the intake valve and the exhaust valve are controlled in the idle cylinder during the reduced-cylinder operation. However, the present invention is not limited to this. When it is required to supply exhaust gas, or another means (for example, a so-called exhaust circulation passage provided so as to extend from the exhaust passage to the intake passage in order to introduce exhaust gas directly from the exhaust passage to the intake passage) When the exhaust gas has already been supplied to the active cylinder during the reduced cylinder operation, the intake air described above is used only when the increase in the amount of exhaust gas supplied to the active cylinder is requested during the reduced cylinder operation. The valve and the exhaust valve may be controlled in the idle cylinder.

  Further, when the above-described intake valve and exhaust valve control is performed in the idle cylinder during the reduced cylinder operation, the intake valve lift amount and valve opening period (so-called operating angle), the exhaust valve lift amount and valve opening period ( The amount of exhaust gas supplied to the working cylinder may be controlled by adjusting a so-called working angle.

  On the other hand, in the first embodiment, when the engine operating state is in the region II of FIG. 3 and all-cylinder operation is performed, in all the cylinders 2A and 2B of the first engine main body 1A and the second engine main body 1B, During the intake stroke, fuel is injected from the fuel injection valves 19 corresponding to the cylinders 2A and 2B, and the intake valves 15 of the cylinders 2A and 2B are opened as indicated by IN1 and IN2 in FIG. The air and fuel are sucked into the cylinders 2A and 2B from the intake branch pipes 3A and 3B, and the spark plugs 20 of the cylinders 2A and 2B are operated at a timing near the compression top dead center to ignite the fuel. As indicated by EX1 and EX2 in FIG. 5, the exhaust valves 17 of the cylinders 2A and 2B are opened, and the exhaust gas is discharged from the cylinders 2A and 2B to the exhaust branch pipes 5A and 5B.

  FIG. 6 shows an example of a routine for controlling the intake valve and the exhaust valve according to the first embodiment. In the routine of FIG. 6, first, at step 10, it is determined whether or not the ignition switch is on. Here, when it is determined that the ignition switch is OFF, the routine ends. On the other hand, when it is determined in step 10 that the ignition switch is on, it is determined in step 11 whether or not the reduced cylinder operation is being performed. If it is determined that the reduced cylinder operation is being performed, it is determined in step 12 whether or not the fluctuation amount ΔNE of the engine speed is smaller than a predetermined value α (ΔNE <α) (that is, the engine operating state). Whether or not is stable).

  When it is determined in step 12 that ΔNE <α (that is, when the engine operating state is stable), intake / exhaust valve control I is executed in step 13. According to this intake / exhaust valve control I, in the operating cylinder 2A, the intake valve 15 is opened in the normal intake stroke, and the exhaust valve 17 is opened in the normal exhaust stroke. On the other hand, in the idle cylinder 2B, the exhaust valve 17 is opened in the normal intake stroke, and the intake valve 15 is opened in the normal exhaust stroke.

  On the other hand, when it is determined in step 12 that ΔNE ≧ α (that is, when the engine operating state is unstable), intake / exhaust valve control II is executed in step 14. According to this intake / exhaust valve control II, in the operating cylinder 2A, the intake valve 15 is opened in the normal intake stroke, and the exhaust valve 17 is opened in the normal exhaust stroke. On the other hand, in the idle cylinder 2B, the intake valve 15 and the exhaust valve 17 are always kept closed.

  On the other hand, when it is determined in step 11 that the reduced-cylinder operation is not being performed (that is, when all the cylinders are being operated), intake / exhaust valve control III is executed in step 15. According to this intake / exhaust valve control III, in all the cylinders 2A, 2B, the intake valve 15 is opened in the normal intake stroke, and the exhaust valve 17 is opened in the normal exhaust stroke.

  In the example shown in FIG. 6, whether or not the engine operating state is stable is determined based on the fluctuation amount of the engine speed, but the fluctuation amount of the output torque, the maximum in-cylinder pressure in the working cylinder, The determination may be made based on the fluctuation amount and the fluctuation amount of the crank angle that is the maximum in-cylinder pressure.

  Next, control of the intake valve and the exhaust valve in the second embodiment will be described. In the second embodiment, the engine operating state is in the region I of FIG. 3 and the reduced-cylinder operation is performed, and the temperature of the exhaust purification catalyst 7B corresponding to the second engine body 1B is lower than its activation temperature. Sometimes, in the operating cylinder 2A, fuel is injected from the fuel injection valve 19 corresponding to the operating cylinder 2A in a normal intake stroke, and the intake valve 15 of the operating cylinder 2A is opened as indicated by IN1 in FIG. As a result, air and fuel are sucked into the working cylinders 2A from the intake branch pipes 3A, and the spark plugs 20 of the working cylinders 2A are actuated at a timing near the compression top dead center to ignite the fuel. As shown, the exhaust valve 17 is opened in the normal exhaust stroke, and the exhaust gas is discharged from each operating cylinder 2A to the exhaust branch pipe 5A.

  On the other hand, in the reduced cylinder operation, in the idle cylinder 2B, fuel is not injected from the fuel injection valve 19 corresponding to the idle cylinder 2B in the normal intake stroke, but the exhaust valve 17 is indicated by IN2 in FIG. As a result, the exhaust gas is sucked into each idle cylinder 2B from the exhaust branch pipe 5B, and then the intake valve 15 is opened in the normal exhaust stroke as indicated by EX2 in FIG. Thus, the exhaust gas is discharged from each of the deactivated cylinders 2B to the intake branch pipe 3B (of course, the spark plug 20 corresponding to the deactivated cylinder 2B is not operated).

  According to this, when the temperature of the exhaust purification catalyst 7B corresponding to the deactivated cylinder 2B is lower than its activation temperature, the deactivated cylinder 2B passes from the exhaust branch pipe 3B connected to the deactivated cylinder 2B through the deactivated cylinder 2B. Since an exhaust gas flow that flows to the intake branch pipe 3B connected to the exhaust gas is generated, at least high-temperature exhaust gas discharged from the active cylinder 2A to the exhaust passage 5A corresponds to the deactivated cylinder 2B. It will flow into 7B. For this reason, the temperature of the exhaust purification catalyst 7B is raised by the heat of the exhaust gas flowing into the exhaust purification catalyst 7B. As a result, the temperature of the exhaust purification catalyst 7B is reliably maintained above its activation temperature. For this reason, immediately after the engine operation is switched from the reduced-cylinder operation to the all-cylinder operation, the temperature of the exhaust purification catalyst 7B corresponding to the deactivated cylinder 2B is maintained at the activation temperature or higher, so that the exhaust emission is reduced.

  FIG. 7 shows an example of a routine for controlling the intake valve and the exhaust valve according to the second embodiment. In the routine of FIG. 7, first, at step 20, it is judged if the ignition switch is on. Here, when it is determined that the ignition switch is OFF, the routine ends. On the other hand, when it is determined at step 20 that the ignition switch is on, it is determined at step 21 whether or not the reduced cylinder operation is being performed. Here, when it is determined that the reduced-cylinder operation is being performed, in step 22, the temperature (catalyst temperature) T of the exhaust purification catalyst 7B corresponding to the second engine body 1B is set to a predetermined temperature β (for example, It is determined whether or not the temperature is at least lower than the activation temperature of the exhaust purification catalyst 7B (T <β) (that is, whether or not the exhaust purification catalyst 7B is in an active state).

  When it is determined in step 22 that T <β (that is, when the exhaust purification catalyst 7B is not in the active state), in step 23, the intake / exhaust valve control I is executed. According to this intake / exhaust valve control I, in the operating cylinder 2A, the intake valve 15 is opened in the normal intake stroke, and the exhaust valve 17 is opened in the normal exhaust stroke. On the other hand, in the idle cylinder 2B, the exhaust valve 17 is opened in the normal intake stroke, and the intake valve 15 is opened in the normal exhaust stroke. As a result, the temperature of the exhaust purification catalyst 7B is raised by the high-temperature exhaust gas flowing into the exhaust purification catalyst 7B.

  On the other hand, when it is determined in step 22 that T ≧ β (that is, when the exhaust purification catalyst 7B is in the active state), the intake / exhaust valve control II is executed in step 24. According to this intake / exhaust valve control II, in the operating cylinder 2A, the intake valve 15 is opened in the normal intake stroke, and the exhaust valve 17 is opened in the normal exhaust stroke. On the other hand, in the idle cylinder 2B, the intake valve 15 and the exhaust valve 17 are always kept closed.

  On the other hand, when it is determined in step 21 that the reduced-cylinder operation is not being performed (that is, when all the cylinders are being operated), intake / exhaust valve control III is executed in step 25. According to this intake / exhaust valve control III, in all the cylinders 2A, 2B, the intake valve 15 is opened in the normal intake stroke, and the exhaust valve 17 is opened in the normal exhaust stroke.

1 is a view showing a variable cylinder internal combustion engine to which the present invention is applied. It is a longitudinal cross-sectional view of the variable cylinder internal combustion engine of FIG. It is the figure which showed the map used in order to determine engine operation. In 1st Embodiment, it is the figure which showed the lift amount of the intake valve and exhaust valve when reduced cylinder driving | operation is performed. In 1st Embodiment, it is the figure which showed the lift amount of the intake valve and exhaust valve when all cylinder operation is performed. It is the figure which showed an example of the routine for controlling an intake valve and an exhaust valve according to 1st Embodiment. It is the figure which showed an example of the routine for controlling an intake valve and an exhaust valve according to 2nd Embodiment.

Explanation of symbols

2A, 2B Cylinder 5A, 5B Exhaust branch pipe 6A, 6B Exhaust passage 15 Intake valve 17 Exhaust valve

Claims (4)

  A variable cylinder operation that includes a plurality of cylinders and selectively performs all-cylinder operation in which combustion is performed in all of these cylinders and reduced-cylinder operation in which combustion is performed only in some of the cylinders depending on the engine operation state. In a control apparatus for a cylinder internal combustion engine, during reduced-cylinder operation, combustion is not performed so that exhaust gas flows into an uncombusted cylinder from the exhaust passage and the exhaust gas that has flowed is discharged into the intake passage A control apparatus for a variable cylinder internal combustion engine, wherein an intake valve and an exhaust valve of a cylinder are operated.   A variable cylinder operation that includes a plurality of cylinders and selectively performs all-cylinder operation in which combustion is performed in all of these cylinders and reduced-cylinder operation in which combustion is performed only in some of the cylinders depending on the engine operation state. In a control apparatus for a cylinder internal combustion engine, when an increase in the amount of exhaust gas supplied to a cylinder that is in a reduced-cylinder operation and is being combusted is required, the exhaust gas is exhausted from the exhaust passage to a cylinder that is not combusting. A control apparatus for a variable cylinder internal combustion engine, wherein an intake valve and an exhaust valve of a cylinder that is not combusted are operated so that gas flows in and the exhaust gas that flows in is discharged into an intake passage.   A variable cylinder operation that includes a plurality of cylinders and selectively performs all-cylinder operation in which combustion is performed in all of these cylinders and reduced-cylinder operation in which combustion is performed only in some of the cylinders depending on the engine operation state. In a control apparatus for a cylinder internal combustion engine, a first exhaust passage connected to a cylinder in which combustion is performed during reduced-cylinder operation and a second exhaust passage connected to a cylinder in which combustion is not performed during reduced-cylinder operation Are separate exhaust passages, and an exhaust purification catalyst for purifying exhaust gas is disposed in the second exhaust passage, and the first exhaust passage downstream of the exhaust purification catalyst and the second exhaust passage are mutually connected. Exhaust gas that is connected and exhaust gas flows from the exhaust passage into a cylinder that is not combusted when the temperature of the exhaust purification catalyst becomes lower than a predetermined temperature during reduced-cylinder operation. Gas is discharged into the intake passage Control device for a variable-cylinder internal combustion engine where combustion with an intake valve of the cylinder is not performed and the exhaust valve is characterized in that it is actuated as.   During the cylinder reduction operation, when the intake valve of the cylinder in which combustion is performed is opened, the exhaust valve of the cylinder in which combustion is not performed is opened and the exhaust valve of the cylinder in which combustion is performed is opened. When the intake valve of the cylinder that is not combusted when the valve is opened is opened, exhaust gas flows into the cylinder that is not combusted from the exhaust passage, and the exhaust gas that has flowed into the intake passage is discharged into the intake passage The control device for a variable cylinder internal combustion engine according to any one of claims 1 to 3, wherein

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