JP2004162617A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device suppressing a lowering of temperature of an exhaust emission controlling catalyst when an engine is stopped in the control device for an internal combustion engine automatically performing idling stop and restarting. <P>SOLUTION: An engine ECU 60 being the control device for the internal combustion engine 1 stops the internal combustion engine 1 in an early stage by such a manner that when the engine 1 is stopped for idling stop, the valve lift timing of at least one of an intake valve 41 and an exhaust valve 42 is changed by variable valve timing means 43, 44 so that negative valve overlap time, that is, time from the closing of the exhaust valve 42 to the opening of the intake valve 41 is lengthened, thereby the workload of a piston 11 is increased. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an internal combustion engine that performs control to automatically stop the internal combustion engine when a predetermined condition is satisfied while the vehicle is stopped and to automatically restart the internal combustion engine when a start condition is satisfied. It relates to a control device.
[0002]
[Prior art]
2. Description of the Related Art There is known a technology (idling stop) for suppressing the amount of exhaust gas and improving fuel efficiency by automatically stopping the engine when the internal combustion engine is idling while the vehicle is stopped such as at a traffic light (for example, And Patent Document 1). In this document, in order to reduce vibration when the engine is stopped due to idling stop in a diesel engine, in particular, a normally-open compression in which a dedicated valve or the like is lifted during a compression and expansion stroke during an engine brake operation to increase a braking force. A technique has been disclosed in which an engine brake is operated when the engine is stopped to suppress vibration generated when the engine is stopped. By opening the dedicated valve during the intake, compression, and expansion strokes, the force continues to act in the direction of reducing the engine rotation speed due to the flow resistance of the gas flowing through the dedicated valve, and the engine can be stopped quickly. It is described as becoming.
[0003]
[Patent Document 1]
JP-A-2002-97972 (paragraphs 0022 to 0028, FIGS. 1 to 3)
[0004]
[Problems to be solved by the invention]
According to this technique, it is possible to stop the engine quickly by increasing the flow resistance. However, at the time of stoppage, the flow rate of gas flowing to the exhaust side increases, and the heat retention of the exhaust gas purification catalyst may decrease. is there.
[0005]
It is an object of the present invention to provide a control device for an internal combustion engine that automatically performs idling stop and restart, wherein the control device can suppress a decrease in the temperature of an exhaust gas purification catalyst when the engine is stopped.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, a control device for an internal combustion engine according to the present invention automatically stops the internal combustion engine when the vehicle is in a stopped state and a predetermined condition is satisfied, and automatically stops when the start condition is satisfied. In a control device for an internal combustion engine that performs control to restart the internal combustion engine, the internal combustion engine further includes variable valve timing means capable of changing the opening / closing timing of at least one of an intake valve and an exhaust valve, When the internal combustion engine is automatically stopped, the fuel supply is stopped and the variable valve timing is operated to control the timing from when the exhaust valve is closed to when the intake valve is opened to be longer than usual.
[0007]
It is preferable that the variable valve timing means performs control for opening the intake valve later than usual or closing the exhaust valve earlier than usual when the internal combustion engine is automatically stopped.
[0008]
The pump work is increased in the intake stroke or the exhaust compression work is increased in the exhaust stroke by adjusting the timing from the closing of the exhaust valve to the opening of the intake valve by the variable valve timing means so as to be longer than usual. Thus, the rotation resistance of the engine can be increased and the engine can be stopped early. Further, since the flow rate of gas flowing to the exhaust side can be reduced, the temperature of the catalyst can be prevented from lowering. For this reason, emission deterioration at the time of restart can be suppressed.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same components are denoted by the same reference numerals as much as possible in each drawing, and duplicate description is omitted.
[0010]
FIG. 1 is a schematic configuration diagram of an internal combustion engine equipped with a control device (control device for an internal combustion engine) according to the present invention. The internal combustion engine 1 is a multi-cylinder gasoline engine mounted on a vehicle, and is a spark-ignition internal combustion engine of an in-cylinder fuel injection type. Here, only one of the cylinders is shown in a simplified manner. .
[0011]
A reciprocating piston 11 is disposed in a cylinder 10 of the internal combustion engine 1, and a region defined by the piston 11, the cylinder 10, and the cylinder head 12 forms a combustion chamber 13. The intake pipe 20 and the exhaust pipe 30 are connected to the combustion chamber 13 via an intake valve 41 and an exhaust valve 42. The intake valve 41 and the exhaust valve 42 are opened and closed by variable valve timing means 43 and 44, respectively. One intake valve 41 and one exhaust valve 42 may be provided for each cylinder, or a plurality of intake valves 41 and exhaust valves 42 may be provided. Further, the numbers of the intake valves 41 and the exhaust valves 42 may be different. At a position facing the combustion chamber 13 of the cylinder head 12, an ignition plug 16 and a fuel injector 17 are arranged. The piston 11 is connected to a crankshaft 15 via a connecting rod 14 and converts the reciprocating movement of the piston 11 into a rotational movement of the crankshaft 15. A starting motor 70 can be connected to the crankshaft 15. A cooling water temperature sensor 45 is provided in the cylinder 10 and a crank angle sensor 46 is arranged adjacent to the crankshaft 15.
[0012]
An air filter 21, an intake air temperature sensor 22, an electromagnetic throttle valve 24, and an intake pressure sensor 26 are arranged in the intake pipe 20 from the upstream side. The electromagnetic throttle valve 24 is driven by a throttle motor 23, and its opening is a throttle opening. It is detected by the sensor 25.
[0013]
An exhaust gas purification device 31 including a three-way catalyst, a NOx storage reduction catalyst, and the like is disposed in the exhaust pipe 30. An A / F sensor 32 and a CO sensor 33 are disposed upstream of the exhaust gas purification device 31. The purifier 31 is provided with a catalyst temperature sensor 34.
[0014]
The engine ECU 60, which is a control device of the internal combustion engine 1, includes a CPU, a memory, and the like. In addition to the outputs of the sensors 22, 25, 26, 32 to 34, 45, and 46, an accelerator opening sensor 51 attached to an accelerator pedal 50 operated by the driver and a vehicle speed sensor 52 for detecting the vehicle speed To control the operations of the spark plug 16, the fuel injector 17, the throttle motor 23, the variable valve timing means 43 and 44, and the starting motor 70.
[0015]
The variable valve timing means 43 and 44 form a camshaft having a cam for driving the intake valve 41 and the exhaust valve 42 so that the camshaft has a different phase, or the cam itself has a different shape in the longitudinal direction of the camshaft. The lift timing and lift of the valve are adjusted by moving the camshaft in the longitudinal direction. FIG. 2 is a diagram showing an example of the adjustment. Here, a standard valve lift is indicated by a thick line. Advancement of the valve opening (closing) timing as indicated by a broken line by the variable valve timing means 43 and 44 is called advancement, and conversely, delaying the opening (closing) timing as indicated by a dotted line is retarded. Call. Here, an example is shown in which only the timing is shifted while the lift amount is fixed, but the lift amount may be adjusted in accordance with the adjustment of the opening / closing timing of the valve lift.
[0016]
The control device (engine ECU 60) of the internal combustion engine 1 according to the present invention performs an idling stop (IS) for automatically stopping the internal combustion engine 1 when the vehicle is stopped and when the engine is idling, and performs a control for restarting when the driver performs a start operation. carry out. Hereinafter, the control processing will be specifically described. FIG. 3 is a flowchart showing the contents of this processing, and FIGS. 4 to 6 are views showing some examples of valve lift timing during this processing operation. This process is repeatedly executed by the engine ECU 60 at a predetermined timing after the start of the internal combustion engine 1 until the driver stops the engine by operating the ignition key. The flag FlagES used in this process is a flag indicating whether or not the internal combustion engine 1 is in an IS state in which the internal combustion engine 1 is automatically stopped, and is set to an initial value 0 when the engine is started.
[0017]
In step S1, the value of the flag FlagES is checked. If the value is 0, that is, if the current state is not the IS state and the internal combustion engine 1 is operating, the process proceeds to step S2. In step S2, it is determined whether the IS condition is satisfied. The IS condition is, for example, that the vehicle speed detected by the vehicle speed sensor 52 is 0, the throttle opening detected by the throttle opening sensor 25 is fully closed, and the engine speed detected by the crank angle sensor 47 is When the engine cooling water temperature detected by the cooling water temperature sensor 45 is equal to or higher than the predetermined temperature, the accelerator opening detected by the accelerator opening sensor 51 is equal to or lower than the predetermined angle, and the catalyst detected by the catalyst temperature sensor 34 is equal to or lower than the predetermined rotation speed. It may be determined that the IS condition is satisfied when the temperature is equal to or higher than the predetermined temperature. Thus, when the vehicle is stopped and the internal combustion engine 1 is idling and there is almost no load, the internal combustion engine 1 can be stopped, and the warm-up of the internal combustion engine 1 and the exhaust gas purification device 31 is completed. This is because it is considered that the vehicle can be easily restarted when starting.
[0018]
If the condition is satisfied, the process proceeds to step S3, in which the fuel injection from the fuel injector 17 is prohibited. In the subsequent step S4, the variable valve timing means 43, 44 changes the valve lift timing to the timing at the time of stop. I do. For example, as shown by broken lines A and B in FIG. 4, the opening timing of the intake valve 41 is retarded by the variable valve timing means 43. Alternatively, as shown by broken lines A and B in FIG. 5, the closing timing of the exhaust valve 42 is advanced by the variable valve timing means 44. Further, as shown by broken lines A and B in FIG. 6, the opening timing of the intake valve 41 may be delayed by the variable valve timing means 43 and 44, and the closing timing of the exhaust valve 42 may be advanced.
[0019]
By controlling the valve timing in this manner, the negative valve overlap time (t _A , t _B ), which is the time from when the exhaust valve 42 closes to when the intake valve 41 opens, can be lengthened (usually). Since the intake valve 41 is open while the exhaust valve 42 is open, there is a period during which both are open at the same time, which is referred to as a valve overlap time [takes a positive value]).
[0020]
If the exhaust valve 42 is closed early, all of the in-cylinder gas cannot be exhausted. After the exhaust valve 42 is closed, the remaining in-cylinder gas is compressed until the piston 11 reaches TDC (top dead center). Work load increases. This increase in the work amount allows the internal combustion engine 1 to be stopped early. In addition, since the amount of gas sent to the exhaust gas purification device 31 via the exhaust pipe 30 is reduced, excessive cooling of the catalyst can be suppressed, and the heat retention is improved. On the other hand, if the intake valve 41 is opened late, it is necessary to expand the in-cylinder gas by the piston 11 with the combustion chamber 12 sealed between TDC of the piston 11 and the opening of the intake valve 41. The amount increases. This increase in the work amount allows the internal combustion engine 1 to be stopped early. In addition, by reducing the intake air amount, as a result, the amount of gas sent to the exhaust gas purification device 31 via the exhaust pipe 30 can also be reduced, thereby suppressing excessive cooling of the catalyst and improving its heat retention. . When both are combined, it is possible to stop the internal combustion engine 1 early and to further enhance the heat retaining effect of the exhaust gas purification device. However, providing the variable valve timing means 43 and 44 in both the intake valve 41 and the exhaust valve 42 requires the device. Only one of them may be provided since the configuration becomes complicated and the product cost increases. After stopping the internal combustion engine 1 in step S5 in this way, the flag FlagES is set to 1 and the process ends.
[0021]
On the other hand, if it is determined in step S2 that the IS condition is not satisfied, the subsequent processing is skipped and the processing ends. In this case, the internal combustion engine 1 continues to operate.
[0022]
If FlagES is determined to be 1 in step S1, that is, if it is determined that the internal combustion engine 1 is automatically stopped in the current IS state, the process proceeds to step S11 to determine whether the start condition is satisfied. judge. The start condition is satisfied, for example, when the accelerator opening sensor 51 detects that the driver has depressed the accelerator pedal 50 by a predetermined angle or more. If the starting condition is not satisfied, the subsequent processing is skipped and the processing ends. In this case, the IS state, that is, the automatic stop state of the internal combustion engine 1 continues.
[0023]
If it is determined in step S11 that the start condition has been satisfied, the process proceeds to step S12 to perform engine restart processing. Here, the starting motor 70 is connected to the crankshaft 15, the crankshaft 15 is rotated by the driving force of the starting motor 70, the electromagnetic throttle valve 24 is opened by the throttle motor 23, and the combustion chamber 13 is opened from the opened intake valve 41. Then, the intake valve 41 is closed, the introduced air is compressed (compression step), and fuel is injected from the fuel injector 17 to form an air-fuel mixture. Then, the air-fuel mixture is ignited by the ignition plug 16 and burned, and the expansion of the combustion gas drives the piston 11 (expansion stroke) to drive the crankshaft 15 via the connecting rod 14. The combustion gas is sent to the exhaust pipe 30 via the open exhaust valve 42 and is processed by the exhaust gas purification device 31. When the start of the internal combustion engine 1 is successful, the start motor 70 is disconnected from the crankshaft 15. The success / failure of the start can be determined from the output of the crank angle sensor 47. The fuel injection amount from the fuel injector 17, the valve lift timing by the variable valve timing means 43 and 44 of the intake valve 41 and the exhaust valve 42 at the time of starting, the accelerator opening, the intake temperature detected by the intake temperature sensor 22, the intake pressure sensor The correction is made based on the intake pressure measured at 26, the A / F value measured by the A / F sensor 32 and the CO sensor 33, and the like.
[0024]
If the restart of the internal combustion engine 1 succeeds, the process proceeds to step S13, where FlagES is set to 0 and the process ends. This restart can be performed automatically and in a short time, so that startability is not impaired. With such control, the internal combustion engine 1 can be quickly stopped when the engine is idling while the vehicle is stopped, and can be restarted promptly when the engine starts, so that the amount of exhaust gas is suppressed and the fuel efficiency is improved. In addition, since the amount of gas sent to the exhaust gas purification device 31 when the engine is stopped can be reduced, the heat retention of the catalyst can be maintained.
[0025]
The processing flow described above is an example, and the control in the control device for an internal combustion engine of the present invention is not limited to this processing flow. When the internal combustion engine 1 is stopped idling, the valve lift is controlled by the variable valve timing means. Various processing modes can be adopted as long as the timing is controlled to extend the negative overlap time and stop the engine early. For example, the order of step S3 and step S4 can be changed.
[0026]
Here, the embodiment in which the engine ECU 60 controls the internal combustion engine 1 has been described. However, a dedicated ECU is provided for controlling the variable valve timing means 43 and 44, and this is cooperated with the engine control ECU. Is also good. Alternatively, the vehicle control ECU may also control the internal combustion engine 1.
[0027]
In the above description, the case of a direct injection type gasoline engine has been described as an example, but the present invention is also applicable to a diesel engine or a gasoline engine of a type in which fuel is injected into an intake pipe.
[0028]
【The invention's effect】
As described above, according to the present invention, when automatically stopping the internal combustion engine while the vehicle is stopped and the engine is idling, the valve lift timing of at least one of the intake valve and the exhaust valve is changed by the variable valve timing means. By increasing the negative overlap time, that is, by increasing the time during which both valves are closed, the work of the piston during the expansion or exhaust stroke is increased, and the internal combustion engine is stopped early. Further, since the amount of exhaust gas can be reduced, the cooling of the exhaust gas purification device is suppressed, and the heat retention property is improved.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an internal combustion engine equipped with a control device according to the present invention.
FIG. 2 is a diagram illustrating a change of a valve lift timing by a variable valve timing means.
FIG. 3 is a flowchart showing idling stop / restart control processing in the apparatus of FIG. 1;
FIG. 4 is a diagram illustrating an example of a valve lift timing at the time of the processing of FIG. 3;
FIG. 5 is a diagram for explaining another example of the valve lift timing at the time of the processing in FIG. 3;
FIG. 6 is a view for explaining still another example of the valve lift timing at the time of the processing of FIG. 3;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine, 10 ... Cylinder, 11 ... Piston, 12 ... Cylinder head, 13 ... Combustion chamber, 14 ... Connecting rod, 15 ... Crankshaft, 16 ... Spark plug, 17 ... Fuel injector, 20 ... Intake pipe, 21 ... Air Filter 22, 22 intake temperature sensor, 23 throttle motor, 24 electromagnetic throttle valve, 25 throttle opening sensor, 26 intake pressure sensor, 30 exhaust pipe, 31 exhaust purification device, 32 A / F sensor, 33: CO sensor, 34: catalyst temperature sensor, 41: intake valve, 42: exhaust valve, 43, 44: variable valve timing means, 45: cooling water temperature sensor, 46: crank angle sensor, 50: accelerator pedal, 51: accelerator Opening sensor, 52: vehicle speed sensor, 60: engine ECU, 70: starting motor.

Claims (3)

In a control device for an internal combustion engine that performs control to automatically stop the internal combustion engine when a predetermined condition is satisfied while the vehicle is stopped and automatically restart the internal combustion engine when a start condition is satisfied,
The internal combustion engine further includes variable valve timing means capable of changing the opening / closing timing of at least one of an intake valve and an exhaust valve.When the internal combustion engine is automatically stopped, fuel supply is stopped to adjust the variable valve timing. A control device for an internal combustion engine that controls a timing from when an exhaust valve closes to when an intake valve opens by operating the means. 2. The control device for an internal combustion engine according to claim 1, wherein when the internal combustion engine is automatically stopped, control is performed by the variable valve timing means to open the intake valve later than usual. 3. The control device for an internal combustion engine according to claim 1, wherein when the internal combustion engine is automatically stopped, control for closing an exhaust valve earlier than usual is performed by the variable valve timing means.

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