JP2006152968A - Controller of internal combustion engine with variable valve timing mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To rapidly lower the rotational speed of an internal combustion engine if the over-rotation of the internal combustion engine occurs or a vehicle is decelerating. <P>SOLUTION: This internal combustion engine having the variable valve timing mechanism comprises an over-rotation determination means determining whether the over-rotation of the internal combustion engine occurs or not and/or a deceleration determination means determining whether the vehicle is in a decelerating state or not. When the internal combustion engine is determined to cause the over-rotation (positive determination in S101) or the vehicle is determined to be in the decelerating state (positive determination in S102), the variable valve timing mechanism advances the valve closing timing of the exhaust valve more than in a case where the over-rotation of the internal combustion engine is determined not to cause over-rotation or the vehicle is determined to be not in the decelerating state (S103 to S104). Thus, since a pump loss is increased, the rotational speed of the engine can be rapidly lowered. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a control device for an internal combustion engine including a variable valve timing mechanism capable of changing valve timing.

  When the lubricating oil flows into the cylinder (combustion chamber) of the internal combustion engine and this lubricating oil burns, the rotational speed of the internal combustion engine may increase from the required rotational speed at that time. If the rotational speed of the internal combustion engine rises and exceeds the allowable rotational speed, the internal combustion engine may be damaged.

When such over-rotation (overrun) of the internal combustion engine is detected, the intake throttle valve is closed to reduce the intake air amount of the internal combustion engine, thereby reducing the engine speed or suppressing torque fluctuations. For example, a technique for eliminating over-rotation is known (see, for example, Patent Document 1).
JP 2003-254144 A Japanese Utility Model Publication No. 6-73346 Japanese Patent Laid-Open No. 9-79056 JP-A-10-252575 JP 2001-355462 A JP 2001-355487 A

  However, the intake passage from the intake throttle valve to the combustion chamber has a certain volume, and even if the intake throttle valve is closed, air existing in the intake passage from the intake throttle valve to the combustion chamber is sucked into the combustion chamber. Therefore, the amount of oxygen in the cylinder does not decrease immediately. Further, the pump loss does not increase rapidly but gradually increases. Therefore, it has been difficult to quickly eliminate the overspeed of the internal combustion engine.

  Also, if the intake throttle valve is suddenly closed while lubricating oil or the like is burning in the combustion chamber, the pressure in the intake passage between the compressor of the turbocharger and the intake throttle valve increases, and the compressor and intake passage are There was a possibility that the constituent members were damaged.

  Further, when an overspeed of the internal combustion engine occurs, it is conceivable to close the exhaust throttle valve or close the nozzle vane of the variable displacement turbocharger. Thereby, a pump loss can be enlarged and an engine speed can be reduced. However, since the rotation speed of the turbocharger increases when the nozzle vane is closed, the nozzle vane cannot be closed until the limit rotation speed of the turbocharger is exceeded. Further, if the nozzle vane is closed every time the driver steps on the brake, the nozzle vane may vibrate. Furthermore, when the exhaust throttle valve is closed or the nozzle vane is closed, the back pressure increases, and during subsequent acceleration, the combustion state in the combustion chamber deteriorates until the back pressure decreases, and smoke may be discharged. is there. Moreover, it is difficult to control the degree of decrease in engine speed with an exhaust throttle valve that is operated by an actuator.

  The present invention has been made in view of the above-described problems, and in an internal combustion engine control apparatus equipped with a variable valve timing mechanism, when it is necessary to reduce the rotational speed of the internal combustion engine, the internal combustion engine An object of the present invention is to provide a technique capable of rapidly reducing the rotational speed of the slab.

In order to achieve the above object, an internal combustion engine control apparatus provided with a variable valve timing mechanism according to the present invention is characterized by the following. That is,
In an internal combustion engine having a variable valve timing mechanism for changing the opening and closing timing of the exhaust valve,
An overspeed determination means for determining whether or not an overspeed of the internal combustion engine has occurred;
When the overspeed determination means determines that an overspeed of the internal combustion engine has occurred, the variable valve timing mechanism determines that the exhaust valve is more inactive than when it is determined that no overspeed of the internal combustion engine has occurred. The valve closing timing is advanced.

  That is, when the valve closing timing of the exhaust valve is advanced by the variable valve timing mechanism, the exhaust valve is closed during the piston ascending in the exhaust stroke. Then, the burnt gas is confined in the cylinder, and the piston works by compressing the burned gas, and the pump loss increases accordingly.

  Further, when the closing timing of the exhaust valve is advanced, the intake valve is opened in a state where the burned gas is compressed, so that the burned gas flows back into the intake passage. This burned gas flows again into the cylinder during the intake stroke. Thus, the pump loss can be increased by sucking the burned gas once flowing out into the intake passage into the cylinder again.

  Since the force for rotating the crankshaft decreases due to the increased pump loss in this way, the rotational speed of the internal combustion engine can be reduced, the occurrence of overspeed can be suppressed, or the overspeed can be suppressed. Can be eliminated.

  Further, when the valve closing timing of the exhaust valve is advanced by the variable valve timing mechanism, the pump loss can be increased from that cycle or the next cycle, so that the rotational speed of the internal combustion engine can be quickly reduced. .

In order to achieve the above object, an internal combustion engine control apparatus provided with a variable valve timing mechanism according to the present invention may be characterized as follows. That is,
In an internal combustion engine having a variable valve timing mechanism for changing the opening and closing timing of the exhaust valve,
The vehicle further comprises deceleration determination means for determining whether or not the vehicle is in a deceleration state,
When the deceleration determination means determines that the vehicle is in a deceleration state, the variable valve timing mechanism advances the valve closing timing of the exhaust valve more than when it is determined that the vehicle is not in a deceleration state. It is good.

  That is, by increasing the pump loss as described above, the rotational speed of the internal combustion engine can be quickly reduced, so that the vehicle can be quickly decelerated.

  The greatest feature of the present invention is that when the engine speed is to be reduced, the valve closing timing of the exhaust valve is advanced, thereby generating a pump loss for compressing the burned gas, and the engine speed. It is to reduce.

  If both the overspeed determination means and the deceleration determination means are provided, the overspeed determination means determines that an overspeed of the internal combustion engine has occurred, or the deceleration occurs when the vehicle is in a deceleration state. When the determination means determines, the variable valve timing mechanism advances the valve closing timing of the exhaust valve more than when it is determined that the overspeed of the internal combustion engine has not occurred and the vehicle is not decelerated. You may let them.

In the present invention, when the valve closing timing of the exhaust valve is advanced, the variable valve timing mechanism can also advance the valve opening timing of the exhaust valve.

  As described above, when the opening timing of the exhaust valve is advanced, the exhaust valve is opened during the expansion stroke, so that the combustion gas is discharged from the cylinder while the combustion gas is pushing down the piston. Therefore, energy for rotating the crankshaft is discharged out of the cylinder as heat of exhaust. Thereby, since the force for rotating the crankshaft is reduced, the rotational speed of the internal combustion engine can be reduced.

  Further, in the present invention, the variable valve timing mechanism also changes the valve timing of the intake valve, and when the valve closing timing of the exhaust valve is advanced, the valve opening timing of the intake valve is set as the exhaust top dead center. can do.

  As described above, when the closing timing of the exhaust valve is advanced, the burnt gas is compressed and the pressure in the cylinder rises. When the piston reaches the exhaust top dead center, the space volume in the cylinder is minimized and the pressure of the burned gas after combustion is the highest. Therefore, work is performed to compress the burned gas until the piston reaches exhaust top dead center, and pump loss increases. However, if the intake valve is kept closed even after the piston has passed the exhaust top dead center, the compressed burned gas will then push down the piston, generating a force to rotate the crankshaft. Therefore, the pump loss per cycle is reduced. Therefore, the pump loss can be further increased by opening the intake valve when the piston reaches the exhaust top dead center.

  According to the control apparatus for an internal combustion engine provided with the variable valve timing mechanism according to the present invention, the pump loss is increased by advancing the closing timing of the exhaust valve, and the rotational speed of the internal combustion engine is rapidly reduced. Can do.

  Specific embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating a schematic configuration of an internal combustion engine 1 according to the present embodiment. The internal combustion engine 1 according to this embodiment is a four-cylinder diesel engine. In the present embodiment, in order to display the internal combustion engine 1 simply, some components are not shown.

  An intake pipe 4 is connected to the combustion chamber in the cylinder 2 via an intake port 3 provided in the cylinder head 10. Inflow of intake air into the cylinder (combustion chamber) 2 is controlled by an intake valve 5. Opening and closing of the intake valve 5 is controlled by rotational driving of the intake side cam 6. An exhaust pipe 8 is connected via an exhaust port 7 provided in the cylinder head 10. Exhaust discharge to the outside of the cylinder 2 is controlled by an exhaust valve 9. Opening and closing of the exhaust valve 9 is controlled by rotational driving of the exhaust side cam 11. Further, a fuel injection valve 12 is provided at the top of the cylinder 2. The piston 15 connected to the crankshaft 13 of the internal combustion engine 1 via the connecting rod 14 reciprocates in the cylinder 2.

  An intake throttle valve (throttle valve) 16 for adjusting the amount of intake air flowing through the intake pipe 4 is provided in the middle of the intake pipe 4.

Further, the internal combustion engine 1 is provided with an electronic control unit (hereinafter referred to as “ECU”) 90 for controlling the internal combustion engine 1. The ECU 90 includes a CPU, a ROM, a RAM, and the like for storing various programs and maps, and a unit that controls the operating condition of the internal combustion engine 1 according to the operating conditions of the internal combustion engine 1 and the driver's request. It is.

  Here, the accelerator opening sensor 91 is electrically connected to the ECU 90, and the ECU 90 receives a signal corresponding to the accelerator opening, and calculates an engine load and the like required for the internal combustion engine 1 according to this signal. A crank position sensor 92 is electrically connected to the ECU 90. The ECU 90 receives a signal corresponding to the rotation angle of the output shaft of the internal combustion engine 1, and the engine rotational speed of the internal combustion engine 1, the engine rotational speed and the gear. The speed or the like of the vehicle on which the internal combustion engine 1 is mounted is calculated from the ratio or the like.

  Next, an opening / closing operation of the intake valve 5 and the exhaust valve 9 in the internal combustion engine 1 and an opening / closing mechanism for performing the opening / closing operation will be described.

  In the internal combustion engine 1, the intake valve 5 is opened and closed by the intake side cam 6. The intake side cam 6 is attached to an intake side camshaft 22, and an intake side pulley 24 is provided at the end of the intake side camshaft 22. Further, a variable rotation phase mechanism (hereinafter referred to as “intake side VVT”) 23 that can change the relative rotation phase between the intake side camshaft 22 and the intake side pulley 24 is provided. The intake side VVT 23 controls the relative rotation phase between the intake side camshaft 22 and the intake side pulley 24 in accordance with a command from the ECU 90.

  The opening / closing operation of the exhaust valve 9 is performed by the exhaust side cam 11. The exhaust side cam 11 is attached to the exhaust side cam shaft 25, and an exhaust side pulley 27 is provided at the end of the exhaust side cam shaft 25. Further, a variable rotation phase mechanism (hereinafter referred to as “exhaust side VVT”) 26 that can change the relative rotation phase between the exhaust side camshaft 25 and the exhaust side pulley 27 is provided. The exhaust side VVT 26 controls the relative rotation phase between the exhaust side camshaft 25 and the exhaust side pulley 27 in accordance with a command from the ECU 90.

  The rotation of the intake camshaft 22 and the exhaust camshaft 25 is driven by the driving force of the crankshaft 13.

  In this way, the intake side camshaft 22 and the exhaust side camshaft 25 are rotationally driven by the driving force of the crankshaft 13, so that the intake side cam 6 and the exhaust side cam 11 cause the intake valve 5 and the exhaust valve 9 to move. Opening and closing operations are performed.

  In this embodiment, when it is determined that the overspeed of the internal combustion engine 1 is occurring, or when it is determined that the vehicle is in a decelerating state, the opening timing and closing timing of the exhaust valve 9 are determined. Advance the angle.

  Here, FIG. 2 is a graph showing changes in the lift amounts of the exhaust valve 9 and the intake valve 5 with respect to the crank angle according to the present embodiment. A solid line indicates a case where it is determined that an overspeed of the internal combustion engine 1 has occurred, or a case where it is determined that the vehicle is in a deceleration state, and a broken line indicates that an overspeed of the internal combustion engine 1 has not occurred and The case where it is determined that the vehicle is not in a deceleration state is shown. When it is determined that the over-rotation of the internal combustion engine 1 indicated by the broken line has not occurred and it is determined that the vehicle is not decelerating, the exhaust valve 9 is opened, for example, from 17 degrees to 20 degrees before bottom dead center. The valve is closed near the exhaust top dead center.

  On the other hand, when it is determined that the overspeed of the internal combustion engine 1 is occurring or when it is determined that the vehicle is in a decelerating state, the valve opening timing and the valve closing timing of the exhaust valve 9 are advanced. As a result, since the combustion gas is discharged to the exhaust port 7 while the combustion gas is pushing down the piston 15, the force for rotating the crankshaft 13 is reduced and the engine speed is reduced.

  When the exhaust valve 9 is closed during the exhaust stroke before the exhaust top dead center, the burnt gas is compressed in the cylinder until the piston 15 reaches the exhaust top dead center. Therefore, a part of the energy generated by the combustion of the fuel is used for compressing the burned gas, so that the force for rotating the crankshaft 13 is reduced and the engine speed is reduced.

  Further, when the intake valve 5 is opened in a state where the burned gas is compressed, the burned gas flows out to the intake port 3. Since the piston works to suck the burned gas into the cylinder again, this is a pump loss. In order to increase the pump loss, in this embodiment, when the closing timing of the exhaust valve 9 is advanced, the opening timing of the intake valve 5 is set to the exhaust top dead center (TDC). Then, the valve timing of the intake valve 5 is changed. Note that if the opening timing of the intake valve 5 is further advanced from the exhaust top dead center, the intake valve 5 and the piston 15 may come into contact with each other. You may advance further than exhaust top dead center.

  Here, as the valve opening timing of the exhaust valve 9 is advanced, the force to push down the piston decreases, so the degree of decrease in the engine speed increases. Further, as the exhaust valve 9 is closed, the amount of burned gas that is compressed increases, and the amount of burned gas that flows out to the intake port 3 increases. The degree increases.

  Therefore, in this embodiment, when it is determined that an overspeed of the internal combustion engine 1 that requires a rapid reduction in the rotational speed of the internal combustion engine 1 has occurred, the timing for opening and closing the exhaust valve 9 is determined. Advance the valve timing as much as possible.

  On the other hand, when it is determined that the vehicle is in a decelerating state, the opening timing and closing timing of the exhaust valve 9 are changed based on drivability or the temperature of the exhaust purification catalyst. For example, if the vehicle is only to be decelerated, the stronger the engine brake is, the better. Therefore, it is preferable to advance the opening timing and closing timing of the exhaust valve 9 as much as possible. I feel uncomfortable. Further, while the vehicle is decelerating, the temperature of the exhaust gas is reduced due to the fuel cut, so that the temperature of the exhaust purification catalyst may be lower than the activation temperature. In order to suppress a decrease in the temperature of the exhaust purification catalyst, the engine brake is strengthened and the vehicle is quickly decelerated, thereby shortening the period during which the vehicle is in a decelerating state, and then quickly restarting fuel injection. Better to do. Therefore, in this embodiment, when it is determined that the vehicle is in a deceleration state, the exhaust valve 9 is opened in consideration of the required engine brake strength, exhaust purification catalyst temperature, and exhaust temperature. Determine the valve timing and valve closing timing. These relationships are obtained in advance through experiments or the like and are mapped and stored in the ECU 90.

  As described above, when the overspeed of the internal combustion engine 1 occurs, the engine speed can be lowered by advancing the opening timing and closing timing of the exhaust valve 9. In addition, since the response speeds of the exhaust side VVT 26 and the intake side VVT 23 are faster than those of the conventionally used intake throttle valves and nozzle vanes of the variable displacement turbocharger, the engine speed can be reduced more quickly.

  Also, the intake passage from the intake throttle valve to the combustion chamber does not have a large negative pressure, and the pressure of the intake passage from the compressor of the turbocharger to the intake throttle valve does not increase. Will not be damaged.

Further, since the response speeds of the exhaust side VVT 26 and the intake side VVT 23 are fast, the vehicle speed can be feedback controlled by controlling the exhaust side VVT 26 and the intake side VVT 23 regardless of the cause of the overspeed of the internal combustion engine 1. . With this feedback control,
For example, the vehicle can be driven at a speed of 20 to 30 km / h, and the vehicle can be retracted during that time.

  In addition, the conventional engine that reduces the engine speed by closing the intake throttle valve generates a force that opposes the force to turn the crankshaft after the force to turn the crankshaft is generated by the combustion gas. Excessive force was applied to the members constituting the engine. On the other hand, when the opening timing of the exhaust valve 9 is advanced, the combustion gas energy is discharged to the exhaust port together with the exhaust gas before becoming the force for turning the crankshaft 13. Thereby, since the force itself which turns the crankshaft 13 falls, the extra force concerning the internal combustion engine 1 can be decreased.

  On the other hand, compared to the conventional variable displacement turbocharger that closes the nozzle vane, the turbocharger's limit rotational speed is not exceeded, so that the turbocharger is not damaged. Further, since the supercharging pressure does not rise rapidly, the members constituting the internal combustion engine 1 are not damaged.

  Further, since the exhaust side VVT 26 is more responsive than the nozzle vane, the opening timing and closing timing of the exhaust valve 9 can be quickly returned to the original during re-acceleration after deceleration, thereby requiring the internal combustion engine 1. Therefore, the transient characteristic of the internal combustion engine 1 is excellent.

  Furthermore, since the exhaust side VVT 26 has better responsiveness than the nozzle vane, the pump loss can be precisely controlled by detecting the engine speed and its fluctuation, and an appropriate deceleration force can be obtained.

  Next, the advance angle control of the exhaust valve 9 according to this embodiment will be described.

  FIG. 3 is a flowchart showing a flow of the advance angle control of the exhaust valve 9 according to this embodiment. This process is repeatedly executed every predetermined time.

  In step S101, the ECU 90 determines whether or not an overspeed of the internal combustion engine 1 has occurred.

  For example, when the engine speed is increasing without the intake throttle valve 16 being opened, or when the engine speed is increasing without the accelerator being stepped on, the maximum allowable engine speed of the internal combustion engine 1 is increased. If the engine speed is increased even though the vehicle speed is zero, it can be determined that the overspeed of the internal combustion engine 1 has occurred. .

  That is, when the intake throttle valve 16 is not opened or the accelerator is not depressed, fuel is injected from the fuel injection valve 12 so as to maintain a predetermined idle rotation. However, when lubricating oil or the like is burned in addition to the fuel, the engine speed increases. Therefore, in such a case, it can be determined that the overspeed of the internal combustion engine 1 has occurred.

  The internal combustion engine 1 has a maximum rotational speed that is allowed to prevent damage. If a rotational speed that is lower than the maximum allowable rotational speed by a predetermined value is detected, the maximum allowable rotational speed is detected thereafter. The maximum speed may be reached. In this embodiment, even in such a case, it is determined that over-rotation has occurred. Here, the predetermined value is set based on the time required to advance the valve opening timing and valve closing timing of the exhaust valve 9 to decrease the engine speed.

  Further, when the vehicle speed is 0, the internal combustion engine 1 is controlled so as to maintain idle rotation, but when the driver steps on the accelerator accidentally, the engine speed increases. In such a case, it is determined that over-rotation has occurred.

  If an affirmative determination is made in step S101, the process proceeds to step S103, whereas if a negative determination is made, the process proceeds to step S102.

  In step S102, the ECU 90 determines whether or not the vehicle is decelerating. Here, it is determined that the vehicle is in a decelerating state when the speed of the vehicle decreases and the accelerator is not depressed.

  If an affirmative determination is made in step S102, the process proceeds to step S103. On the other hand, if a negative determination is made, this routine is temporarily terminated.

  In step S103, the ECU 90 determines the opening timing and closing timing of the exhaust valve 9. For example, when over-rotation has occurred, the opening timing and closing timing of the exhaust valve 9 are advanced as much as possible. Further, when the vehicle is in a decelerating state, the opening timing and closing timing of the exhaust valve 9 are determined based on the engine speed and the temperature of the exhaust purification catalyst.

  In step S104, the opening timing and closing timing of the exhaust valve 9 are changed, and further, the opening timing of the intake valve 5 is changed so that the intake valve 5 is opened at the exhaust top dead center.

  In step S105, the ECU 90 determines whether or not the overspeed of the internal combustion engine 1 has occurred and the vehicle is not in a deceleration state. That is, it is determined whether it is no longer necessary to advance the opening timing and closing timing of the exhaust valve 9.

  If an affirmative determination is made in step S105, the process proceeds to step S106, whereas if a negative determination is made, the process returns to step S105.

  In step S106, the ECU 90 returns the valve opening timing and valve closing timing of the exhaust valve 9 and further the valve opening timing of the intake valve 5 to normal values.

  As described above, according to the present embodiment, when the overspeed of the internal combustion engine occurs or when the vehicle is decelerated, the opening timing and closing timing of the exhaust valve 9 are advanced. The pump speed can be increased and the engine speed can be quickly reduced.

  In this embodiment, both the opening timing and closing timing of the exhaust valve 9 are advanced when an overspeed of the internal combustion engine is detected or when the vehicle is decelerated. Only the valve closing timing may be advanced while the valve opening timing of 9 is kept as it is.

It is a figure showing the schematic structure of the internal combustion engine which concerns on an Example. It is the figure which showed transition of the lift amount of the exhaust valve and the intake valve with respect to the crank angle by an Example. It is the flowchart which showed the flow of advance angle control of the exhaust valve by an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder 3 Intake port 4 Intake pipe 5 Intake valve 6 Intake side cam 7 Exhaust port 8 Exhaust pipe 10 Exhaust valve 10 Cylinder head 11 Exhaust side cam 12 Fuel injection valve 13 Crankshaft 14 Connecting rod 15 Piston 16 Intake throttle valve 22 Intake side camshaft 23 Intake side VVT
24 Intake side pulley 25 Exhaust side camshaft 26 Exhaust side VVT
27 Exhaust side pulley 90 ECU
91 Accelerator opening sensor 92 Crank position sensor

Claims (4)

In an internal combustion engine having a variable valve timing mechanism for changing the opening and closing timing of the exhaust valve,
An overspeed determination means for determining whether or not an overspeed of the internal combustion engine has occurred;
When the overspeed determination means determines that an overspeed of the internal combustion engine has occurred, the variable valve timing mechanism determines that the exhaust valve is more inactive than when it is determined that no overspeed of the internal combustion engine has occurred. A control apparatus for an internal combustion engine, comprising a variable valve timing mechanism, wherein the valve closing timing is advanced. In an internal combustion engine having a variable valve timing mechanism for changing the opening and closing timing of the exhaust valve,
The vehicle further comprises deceleration determination means for determining whether or not the vehicle is in a deceleration state,
When the deceleration determination means determines that the vehicle is in a deceleration state, the variable valve timing mechanism advances the valve closing timing of the exhaust valve more than when it is determined that the vehicle is not in a deceleration state. A control apparatus for an internal combustion engine comprising a variable valve timing mechanism.   3. The variable valve timing mechanism according to claim 1, wherein when the valve closing timing of the exhaust valve is advanced, the valve opening timing of the exhaust valve is also advanced. A control device for an internal combustion engine.   The variable valve timing mechanism also changes the valve timing of the intake valve, and when the closing timing of the exhaust valve is advanced, the opening timing of the intake valve is set as an exhaust top dead center. An internal combustion engine control device comprising the variable valve timing mechanism according to Item 3.

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