JP4367532B2 - Control device for internal combustion engine - Google Patents

Description

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

  Conventionally, an internal combustion engine having an exhaust variable valve timing mechanism capable of changing a phase angle (valve timing) of an exhaust valve is known. In such an internal combustion engine, for example, when the internal combustion engine is cold-started, the exhaust valve closes at the intake top dead end in order to reduce the discharge of unburned hydrocarbons (unburned HC) from the engine body. Control to advance the point is performed (for example, Patent Document 1).

  That is, when the engine is started, all of the fuel injected from the fuel injection valve does not burn, and a part of the fuel remains in the combustion gas as unburned HC. Here, in the apparatus described in Patent Document 1, when the combustion gas cannot be sufficiently re-inhaled into the combustion chamber due to the relationship between the pressure in the intake passage and the pressure in the exhaust passage, the exhaust valve The valve closing timing is advanced. As a result, a large amount of combustion gas remains in the combustion chamber even after the exhaust valve is closed, and this combustion gas is sucked into the combustion chamber in the intake stroke of the next cycle. For this reason, a large amount of combustion gas is re-intaken into the combustion chamber, so that unburned HC contained in the combustion gas is combusted in the next cycle. Thereby, unburned HC contained in exhaust gas can be reduced.

JP 2003-120348 A JP 2002-89302 A JP 2001-280228 A JP 2001-152854 A

  Incidentally, there are various controls other than the control described in Patent Document 1 as the control performed in the internal combustion engine having the exhaust variable valve timing mechanism capable of changing the working angle of the exhaust valve. One example is the early closing control of the exhaust valve during engine low load operation.

  In this exhaust early closing control, the closing timing of the exhaust valve is advanced as compared with the normal time at the time of engine low load operation or the like, and is advanced from the intake top dead center. As a result, the exhaust valve is closed before the piston reaches top dead center. For this reason, the combustion gas remaining in the combustion chamber is compressed by raising the piston after the exhaust valve is closed. Therefore, when the intake valve is opened, the pressure of the exhaust gas in the combustion chamber is high, and at least a part of the exhaust gas in the combustion chamber flows back into the intake port. Such a backflow of exhaust gas blows off the fuel adhering to the wall surface of the intake port and promotes atomization of the fuel injected from the fuel injection valve, so that the combustion state of the internal combustion engine can be improved.

  However, if the exhaust valve operating angle (that is, the valve opening time) cannot be changed by the exhaust variable valve timing mechanism, the efficiency of illustration of the internal combustion engine is reduced. In other words, when the working angle of the exhaust valve cannot be changed, advancing the closing timing of the exhaust valve leads to advancing the opening timing of the exhaust valve as it is. When the opening timing of the exhaust valve is advanced from the expansion bottom dead center, the period during which the piston is pushed down by the combustion gas is shortened. As a result, the energy of the combustion gas cannot be sufficiently converted to the kinetic energy of the piston, and the output torque from the internal combustion engine is reduced. In particular, the influence is remarkable during the deceleration operation of the internal combustion engine, and a torque shock due to a sudden decrease in the output torque may occur, or the output torque may decrease too much, leading to an engine stall.

  Accordingly, an object of the present invention is to provide a control device for an internal combustion engine that prevents the occurrence of torque fluctuations that cause deterioration in drivability or engine stall during deceleration operation of the internal combustion engine due to the execution of exhaust early closing control. It is in.

In order to solve the above-mentioned problem, in the first invention, a control device for an internal combustion engine comprising a fuel injection valve for injecting fuel into an intake port and an exhaust variable valve timing mechanism capable of changing the valve timing of the exhaust valve When the exhaust early closing control execution condition is satisfied, the exhaust valve closing timing is advanced from the intake top dead center so that the combustion gas in the combustion chamber enters the intake port when the intake valve opens. In the control apparatus for executing the exhaust early closing control for causing the engine to flow backward , the engine further includes torque detecting means for detecting the output torque output by the engine body. Even if it is established, if the output torque detected by the torque detecting means is expected to be smaller than the limit torque, the exhaust early closing control is executed. To stop.
According to the first aspect of the invention, when it is predicted that the output torque of the internal combustion engine will be too small, execution of the early exhaust closing control is prohibited. As a result, during the deceleration operation of the internal combustion engine, when the output torque of the internal combustion engine is sufficient, the combustion state of the internal combustion engine can be improved by performing the exhaust early closing control, and the output torque of the internal combustion engine is sufficient. If this is not the case, it is possible to prevent the occurrence of torque fluctuations that lead to deterioration of drivability and engine stall by prohibiting the early exhaust closing control.
“Limit torque” means that the minimum torque required to maintain the operation of the internal combustion engine, or to prevent sudden torque fluctuations compared to the output torque in several cycles before the current cycle. Means the minimum torque required.

In order to solve the above-mentioned problem, in the second invention, a control device for an internal combustion engine, comprising: a fuel injection valve that injects fuel into the intake port; and an exhaust variable valve timing mechanism that can change a valve timing of the exhaust valve. When the exhaust early closing control execution condition is satisfied, the exhaust valve closing timing is advanced from the intake top dead center so that the combustion gas in the combustion chamber enters the intake port when the intake valve opens. In the control apparatus for executing the exhaust early closing control for causing the engine to flow backward , the engine further includes torque detecting means for detecting the output torque output by the engine body. Even if it is established, if the output torque detected by the torque detection means is expected to be smaller than the limit torque, the ignition timing is advanced.
According to the second invention, the ignition timing is advanced when the output torque of the internal combustion engine is expected to be too small. As a result, during the deceleration operation of the internal combustion engine, when the output torque of the internal combustion engine is sufficient, the combustion state of the internal combustion engine can be improved by performing the exhaust early closing control, and the output torque of the internal combustion engine is sufficient. When the ignition timing is not advanced, it is possible to prevent the torque fluctuation that causes deterioration of drivability and engine stall by advancing the ignition timing.

In order to solve the above problems, in a third aspect of the invention, a control apparatus for an internal combustion engine, comprising: a fuel injection valve that injects fuel into the intake port; and an exhaust variable valve timing mechanism that can change a valve timing of the exhaust valve. When the exhaust early closing control execution condition is satisfied, the exhaust valve closing timing is advanced from the intake top dead center so that the combustion gas in the combustion chamber enters the intake port when the intake valve opens. In the control device that executes the exhaust early closing control to reversely flow , the engine speed is greater than the limit speed even when the exhaust early closing control execution condition is satisfied during the deceleration operation of the internal combustion engine. When it is expected to be low, execution of the exhaust early closing control is prohibited.
The “limit rotational speed” refers to the minimum engine rotational speed necessary for maintaining the operation of the internal combustion engine, or a sudden change in the engine rotational speed compared to the engine rotational speed in several cycles before the current cycle. It means the minimum engine speed necessary to prevent it from occurring.

In order to solve the above-described problems, in a fourth aspect of the invention, a control device for an internal combustion engine comprising a fuel injection valve that injects fuel into an intake port, and an exhaust variable valve timing mechanism that can change a valve timing of the exhaust valve. When the exhaust early closing control execution condition is satisfied, the exhaust valve closing timing is advanced from the intake top dead center so that the combustion gas in the combustion chamber enters the intake port when the intake valve opens. In the control device that executes the exhaust early closing control to reversely flow , the engine speed is greater than the limit speed even when the exhaust early closing control execution condition is satisfied during the deceleration operation of the internal combustion engine. If it is expected to decrease, the ignition timing is advanced.

According to a fifth aspect of the invention, in any one of the first to fourth aspects of the invention, during execution of the fuel cut control for stopping the fuel injection from the fuel injection valve, the above exhaust early closing control execution condition is satisfied. Even so, when the amount of fuel adhering to the wall surface of the intake port is smaller than the limit fuel amount, the execution of the exhaust early closing control is prohibited regardless of the output torque and the engine speed.
The “limit fuel amount” means the amount of fuel adhered to the wall such that if the amount of fuel adhered to the wall becomes smaller than that, the air-fuel ratio of the mixture cannot be quickly set to the target air-fuel ratio after the fuel cut control is completed. .

  In a sixth aspect of the invention, in any one of the first to fourth aspects of the invention, the amount of fuel attached to the wall surface adhering to the wall surface of the intake port during execution of fuel cut control for stopping fuel injection from the fuel injection valve Accordingly, the advance amount of the exhaust valve closing timing in the exhaust early closing control is controlled.

  According to a seventh aspect, in the fifth or sixth aspect, the wall surface attached fuel amount includes the combustion state of the previous cycle, the valve timing of the intake valve and the exhaust valve, the pressure in the intake passage, and the intake port of the current cycle. It is estimated based on the passing air amount and the fuel injection amount in the current cycle.

In an eighth aspect of the invention, in any one of the fifth to seventh aspects of the invention, immediately after the end of the fuel cut control, even if the exhaust early closing control execution condition is not satisfied, Close control is executed.

  According to a ninth invention, in the eighth invention, when the exhaust early closing control is executed immediately after the fuel cut control is finished, the exhaust valve in the exhaust early closing control according to the amount of fuel attached to the wall surface at the end of the fuel cut control. Set the advance amount of.

  According to the present invention, it is possible to prevent fluctuations in torque that cause deterioration in drivability and engine stall during deceleration operation of the internal combustion engine or the like due to execution of the early exhaust closing control.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing an entire internal combustion engine in which a control device of the present invention is used.

  Referring to FIG. 1, the engine body 1 includes a cylinder block 2, a cylinder head 3, a piston 4, a combustion chamber 5, a spark plug 6 disposed at the center of the top surface of the combustion chamber 5, an intake valve 7, an intake port 8, An exhaust valve 9 and an exhaust port 10 are provided. The intake port 8 is connected to a surge tank 12 via an intake branch pipe 11, and a fuel injection valve 13 for injecting fuel into the corresponding intake port 8 is arranged in each intake branch pipe 11. The exhaust valve 9 is provided with an exhaust variable valve timing mechanism A that can control the phase angle (that is, valve timing) of the exhaust valve 9. In this embodiment, the variable valve timing mechanism is provided only for the exhaust valve 9, but such a variable valve timing mechanism may be provided not only for the exhaust valve 9 but also for the intake valve 7.

  The surge tank 12 is connected to the outlet of the compressor 15a of the exhaust turbocharger 15 via an intake duct 14, and the inlet of the compressor 15a is connected to an air cleaner 17 via an intake air amount detector 16 using, for example, heat rays. A throttle valve 19 driven by an actuator 18 is disposed in the intake duct 14.

  On the other hand, the exhaust port 10 is connected to an inlet of an exhaust turbine 15b of an exhaust turbocharger 15 via an exhaust manifold 20, and an outlet of the exhaust turbine 15b is connected to a catalytic converter 22 containing, for example, a three-way catalyst via an exhaust pipe 21. Is done. An air-fuel ratio sensor 23 is disposed in the exhaust pipe 21.

  The electronic control unit 30 is composed of a digital computer, and is connected to each other by a bidirectional bus 31. A ROM (Read Only Memory) 32, a RAM (Random Access Memory) 33, a CPU (Microprocessor) 34, an input port 35 and an output port 36. It comprises. The output signal of the intake air amount detector 16 and the output signal of the air-fuel ratio sensor 23 are input to the input port 35 via the corresponding AD converters 37, respectively. A pressure sensor 26 for detecting the pressure in the combustion chamber 5 and a temperature sensor 24 for detecting the gas temperature in the combustion chamber 5 are disposed on the top surface of the combustion chamber 5. The output signal of the temperature sensor 24 is input to the input port 35 via the corresponding AD converter 37. A pressure sensor 25 for detecting the pressure in the intake passage is disposed in the surge tank 12, that is, in the intake passage downstream of the throttle valve 19, and the output signal of the pressure sensor 25 is also a corresponding AD converter. 37 to the input port 35.

  A load sensor 41 that generates an output voltage proportional to the amount of depression of the accelerator pedal 40 is connected to the accelerator pedal 40, and the output voltage of the load sensor 41 is input to the input port 35 via the corresponding AD converter 37. The Further, a crank angle sensor 42 that generates an output pulse every time the crankshaft rotates, for example, 30 ° is connected to the input port 35, and the ECU 30 calculates the engine speed based on the output of the crank angle sensor 42. On the other hand, the output port 36 is connected to the spark plug 6, the fuel injection valve 13, the throttle valve drive actuator 18, and the exhaust variable valve timing mechanism A through a corresponding drive circuit 38.

  FIG. 2 shows an exhaust variable valve timing mechanism A attached to the end of the camshaft 50 for driving the exhaust valve 9 in FIG. Referring to FIG. 2, the exhaust variable valve timing mechanism A includes a timing pulley 51 that is rotated in a direction indicated by an arrow through a timing belt by a crankshaft (not shown) of an engine body, and a cylinder that rotates together with the timing pulley 51. A rotating shaft 53 that rotates together with the cylindrical housing 52, rotates together with the exhaust valve driving camshaft 50, and can rotate relative to the cylindrical housing 52; A plurality of partition walls 54 extending and vanes 55 extending from the outer peripheral surface of the rotating shaft 53 to the inner peripheral surface of the cylindrical housing 52 between the partition walls 54 are provided. An advance hydraulic chamber 56 and a retard hydraulic chamber 57 are formed.

  The hydraulic oil supply control to the hydraulic chambers 56 and 57 is performed by a hydraulic oil supply control valve 58. The hydraulic oil supply control valve 58 includes hydraulic ports 59 and 60 connected to the hydraulic chambers 56 and 57, a hydraulic oil supply port 62 discharged from the hydraulic pump 61, a pair of drain ports 63 and 64, And a spool valve 65 that performs communication cutoff control between the ports 59, 60, 62, 63, and 64.

  When the cam phase of the exhaust valve driving camshaft 50 should be advanced, the spool valve 65 is moved to the right in FIG. 2 and the hydraulic oil supplied from the supply port 62 is advanced via the hydraulic port 59. The hydraulic oil in the retard hydraulic chamber 57 is discharged from the drain port 64 while being supplied to the hydraulic chamber 56. At this time, the rotating shaft 53 is rotated relative to the cylindrical housing 52 in the direction of the arrow.

  On the other hand, when the cam phase of the cam shaft 50 for driving the exhaust valve should be retarded, the spool valve 65 is moved to the left in FIG. 2, and the hydraulic oil supplied from the supply port 62 causes the hydraulic port 60 to move. The hydraulic oil in the advance hydraulic chamber 56 is discharged from the drain port 63 while being supplied to the retard hydraulic chamber 57. At this time, the rotating shaft 53 is rotated relative to the cylindrical housing 52 in the direction opposite to the arrow.

  If the spool valve 65 is returned to the neutral position shown in FIG. 2 while the rotation shaft 53 is rotated relative to the cylindrical housing 52, the relative rotation operation of the rotation shaft 53 is stopped, and the rotation shaft 53 The relative rotation position at that time is held. Therefore, the exhaust variable valve timing mechanism A can advance or retard the phase of the cam of the exhaust valve driving camshaft 50 by a desired amount.

  In the internal combustion engine of the present embodiment, control for advancing the closing timing of the exhaust valve 9 during engine low load operation, particularly during deceleration operation and idle operation of the internal combustion engine (hereinafter referred to as “exhaust early closing control”). Done. That is, during normal operation of the internal combustion engine, as shown in FIG. 3 (A), the exhaust valve 9 is opened at a valve opening timing VO slightly before the exhaust bottom dead center, and slightly above the intake top dead center. The valve is closed at a later valve closing timing VC. However, during deceleration operation and idling operation of the internal combustion engine, as shown in FIG. 3B, the exhaust valve 9 is opened at the valve opening timing VO substantially before the exhaust bottom dead center and the intake top dead center. The valve is closed slightly before the closing timing VC. Here, when the valve opening timing VO and the valve closing timing VC of the exhaust valve 9 with respect to the crank angle are referred to as the “phase angle” of the exhaust valve 9, in the internal combustion engine of the present embodiment, the exhaust valve 9 It can be said that the phase angle is advanced compared to that during normal operation.

  As can be seen from FIG. 3 (B), when the exhaust early closing control is performed, the closing timing of the exhaust valve 9 is set to the advance side with respect to the intake top dead center. Therefore, the exhaust valve 9 is closed before the piston 4 reaches its top dead center. For this reason, when the piston 4 rises after the exhaust valve 9 is closed, the combustion gas remaining in the combustion chamber 5 is compressed. Therefore, at this time, the pressure of the combustion gas in the combustion chamber 5 is higher than the pressure of the intake gas in the intake port 8. Thus, when the intake valve 7 is opened while the pressure of the combustion gas in the combustion chamber 5 is high, the combustion gas in the combustion chamber 5 blows out into the intake port 8 and flows backward.

  On the other hand, in the internal combustion engine of the present embodiment, fuel is injected into the intake port 8 by the fuel injection valve 13, but since the amount of air passing through the intake port 8 is small during engine low load operation, The injected fuel is not atomized properly, or a part of the injected fuel is not vaporized and adheres to the wall surface of the intake port 8.

  On the other hand, when the exhaust early closing control as described above is executed, the combustion gas flows back into the intake port 8 at a relatively high pressure, so that atomization of the injected fuel is promoted and the intake port 8 The fuel adhering to the wall surface is blown off by the combustion gas. As a result, the injected fuel is finely atomized and vaporized and sucked into the combustion chamber 5, so that the combustion state of the internal combustion engine at the time of engine low load operation is improved.

  By the way, when the exhaust variable valve timing mechanism A as in the present embodiment is adopted, when the valve closing timing VC of the exhaust valve 9 is advanced as shown in FIG. VO is also advanced. For this reason, the exhaust valve 9 is opened long before the piston 4 reaches the bottom dead center. Therefore, the exhaust valve 9 is opened while the piston 4 is being pushed down by the combustion gas. For this reason, if the exhaust valve 9 opens early, the combustion energy obtained by the combustion of the air-fuel mixture cannot be appropriately converted into kinetic energy. Therefore, when the exhaust early closing control is executed, the output torque obtained by the internal combustion engine becomes small.

  If the output torque obtained by execution of the early exhaust closing control is reduced, the output torque of the internal combustion engine is abruptly lowered depending on the engine operating state, and a large torque shock is generated, leading to deterioration of drivability. Also, depending on the engine operating state, an output torque sufficient to maintain the operation of the internal combustion engine cannot be obtained, leading to a stop (engine stall) of the internal combustion engine.

  Therefore, in the embodiment of the present invention, when the exhaust early closing control execution condition is satisfied, the internal combustion engine is controlled so as to prevent a torque fluctuation that causes deterioration of drivability and engine stall. Yes. Hereinafter, the control of the internal combustion engine in the embodiment of the present invention will be described in detail.

  In the embodiment of the present invention, as described above, when the exhaust early closing control execution condition is satisfied, for example, during engine low load operation where the engine load is a predetermined load or less, during deceleration operation of the internal combustion engine, or idle operation In the inside, exhaust early closing control is executed. However, during the deceleration operation of the internal combustion engine, even when the exhaust early closing control execution condition is satisfied, it is expected that the output torque of the internal combustion engine is lower than the limit torque or lower than the limit torque. In such a case, execution of the early exhaust closing control is prohibited.

  Here, the limit torque is the minimum torque required to maintain the operation of the internal combustion engine, or necessary to prevent sudden torque fluctuations compared to the output torque in the several cycles before the current cycle. Means the lowest torque. For example, the limit torque is calculated based on various parameters representing the operating state of the internal combustion engine such as the engine speed and the engine load, in addition to the output torque of the internal combustion engine up to the previous cycle.

  For example, the minimum torque required to maintain the operation of the internal combustion engine becomes a lower value as the engine speed is higher. This is because if the engine speed is high, even if the output torque is small and the engine speed is reduced, the internal combustion engine will not easily stop. In addition, the minimum torque required to prevent sudden torque fluctuations changes according to the output torque up to the previous cycle, and increases as the output torque up to the previous cycle increases. For example, the deviation between the output torque up to the previous cycle and the minimum torque is substantially constant.

  In addition, the case where the torque is expected to be lower than the limit torque is a case where the limit torque is not actually reached but may be lower than the limit torque. It means a case where the torque is slightly lower than the torque.

  As described above, according to the internal combustion engine of the present embodiment, in principle, during the low load operation of the internal combustion engine, the fuel is attached to the intake port and the fuel injected from the fuel injection valve 13 by the exhaust early closing control. In addition, the prevention of the early exhaust gas closing control under certain conditions prevents a large torque shock or the internal combustion engine from being stopped. Therefore, according to the present embodiment, inappropriate torque fluctuations can be prevented while keeping the combustion of the internal combustion engine as good as possible.

  In the above embodiment, the exhaust early closing control is prohibited when the output torque of the internal combustion engine is lower than the limit torque or when it is expected to be lower than the limit torque. However, the conditions for prohibiting the execution of the exhaust early closing control are not limited to the above conditions. For example, when the engine speed is lower than the limit speed or when it is expected to be lower than the limit speed, the exhaust early closing is performed. Execution of control may be prohibited.

  In this case, the critical engine speed is the minimum engine speed required to maintain the operation of the internal combustion engine, or a sudden change in the engine speed compared to the engine speed in the previous few cycles. It means the minimum engine speed necessary to avoid the engine. This limit rotational speed is calculated based on various parameters representing the operating state of the internal combustion engine such as output torque and engine load, in addition to the engine rotational speed up to the previous cycle, for example. Even when the condition for prohibiting the execution of the early exhaust closing control is set to such a condition, it is possible to prevent an inappropriate torque fluctuation from occurring as in the above embodiment.

  By the way, during the deceleration operation of the internal combustion engine, fuel cut control that does not perform fuel injection from the fuel injection valve 13 is performed according to the engine load and the like. During this fuel cut control, basically no torque is generated, so that no torque shock occurs as described above. Further, when there is a possibility that the internal combustion engine may stop, the fuel cut control is stopped, so that the internal combustion engine does not stop during the fuel cut control. For this reason, during execution of the fuel cut control, inadequate torque fluctuation due to the execution of the exhaust early closing control basically does not occur. Therefore, in the present embodiment, the exhaust early closing control is basically executed during the fuel cut control even during the deceleration operation of the internal combustion engine.

  However, if the early exhaust closing control is executed during the fuel cut control, the air / fuel ratio of the air-fuel mixture sucked into the combustion chamber 5 after the fuel cut control may not be able to be an appropriate air / fuel ratio.

  That is, when the fuel cut control is not executed, a part of the fuel injected from the fuel injection valve 13 adheres to the wall surface of the intake port 8 even if the exhaust early closing control described above is executed. The fuel adhering to the wall surface of the intake port 8 in this way is blown off by the air flowing from the surge tank 12 or the combustion gas flowing backward from the combustion chamber 5 in the subsequent cycle. By repeating such a cycle, a certain amount of fuel is always attached to the wall surface of the intake port 8. The fuel injected from the fuel injection valve 13 is set so that the air-fuel ratio of the air-fuel mixture becomes the target air-fuel ratio (for example, the theoretical air-fuel ratio) in consideration of the fuel blown off from the wall surface of the intake port 8. .

  However, during the fuel cut control, no fuel is injected from the fuel injection valve 13, so that no new fuel adheres to the wall surface of the intake port 8. On the other hand, the fuel adhering to the wall surface of the intake port 8 before the fuel cut control is blown off by the air flowing from the surge tank 12 and further flows backward from the combustion chamber 5 when the early exhaust closing control is executed. Also blown away by the combustion gas. In this way, when the fuel that has already adhered to the wall surface of the intake port 8 is merely blown away without newly adhering fuel, all the fuel that has adhered to the wall surface of the intake port 8 is eventually blown away. End up.

  As described above, when the fuel cut control is terminated in a state where all the fuel adhering to the wall surface of the intake port 8 has been blown off, the fuel injected from the fuel injection valve 13 is discharged from the wall surface of the intake port 8. The air-fuel ratio of the air-fuel mixture can be appropriately controlled because it is set in consideration of the fuel to be blown off and the amount of fuel that adheres to the wall surface of the intake port 8 among the injected fuel increases. Disappear. In particular, since a large amount of oxygen is stored in the three-way catalyst in the catalytic converter 22 at the end of the fuel cut control, the exhaust gas discharged from the engine main body 1 is restored to restore the oxygen storage capacity of the three-way catalyst. Although it is necessary to make the air-fuel ratio as rich as possible, the air-fuel ratio of the exhaust gas does not easily become rich because there is no fuel blown off from the wall surface of the intake port 8.

  Therefore, in the embodiment of the present invention, the amount of fuel adhering to the wall surface of the intake port 8 (hereinafter referred to as “wall surface adhering fuel amount”) during the fuel cut control is estimated, and the estimated wall surface adhering fuel amount is estimated. The execution of exhaust early closing control is adjusted based on the above. Specifically, in the present embodiment, when the estimated amount of fuel adhered to the wall surface is smaller than a predetermined limit fuel amount, the exhaust gas is exhausted regardless of the parameters such as the output torque and engine speed of the internal combustion engine described above. Prohibit early closing control. Here, the limit fuel amount means a wall-attached fuel amount such that the air-fuel ratio of the air-fuel mixture cannot be quickly set to the target air-fuel ratio after the fuel cut control is finished when the wall-attached fuel amount is further reduced.

  In this way, the fuel adhering to the wall surface of the intake port 8 has flowed back from the combustion chamber 5 by prohibiting the exhaust early closing control when the amount of fuel adhering to the wall surface decreases during execution of the fuel cut control. It will not be blown away by the combustion gas. As a result, while the fuel cut control is being performed, some amount of fuel is maintained on the wall surface of the intake port 8, so that the air-fuel ratio of the air-fuel mixture can be controlled relatively well even after the fuel cut control is completed. it can.

  Alternatively, the advance amount of the exhaust valve 9 in the exhaust early closing control may be adjusted according to the amount of fuel adhering to the wall surface estimated during the fuel cut control. In this case, the advance amount of the exhaust valve 9 is reduced as the amount of fuel attached to the wall surface decreases. As a result, the fuel adhering to the wall surface of the intake port 8 is less likely to be blown off by the combustion gas flowing backward from the combustion chamber 5 as the amount of fuel adhering to the wall surface decreases. For this reason, some fuel is maintained on the wall surface of the intake port 8 during the fuel cut control.

  Next, a method for estimating the amount of fuel attached to the wall surface will be described. In the present embodiment, as will be described later, the wall-attached fuel amount in the current cycle is estimated based on the amount of combustion gas blowback in the current cycle and the intake air amount and fuel injection amount in the current cycle.

  First, in the present embodiment, the intake air amount detector 16 detects the in-cylinder charged air amount (the amount of air charged in the combustion chamber 5) in the previous cycle, and also detects the fuel injection amount and the ignition timing. Is done. Based on these parameters, the combustion state of the air-fuel mixture in the combustion chamber 5 in the previous cycle (in particular, the in-cylinder temperature and the in-cylinder pressure) can be estimated. Thus, by estimating the combustion state of the air-fuel mixture in the combustion chamber 5 in the previous cycle, the amount of combustion gas remaining in the combustion chamber 5 at each point in the expansion stroke can be estimated. Note that the combustion state of the air-fuel mixture in the previous cycle may be directly detected by the pressure sensor 26 and the temperature sensor 24 provided on the top surface of the combustion chamber 5 as shown in FIG.

  Next, the closing timing of the exhaust valve 9 and the opening timing of the intake valve 7 in the current cycle are detected, and the pressure in the intake passage is detected by the pressure sensor 25 in the intake passage. Thus, the amount of combustion gas in the combustion chamber 5 when the exhaust valve 9 is closed is estimated based on the combustion state of the air-fuel mixture in the combustion chamber 5 and the closing timing of the exhaust valve 9 in the previous cycle. The pressure of the combustion gas in the combustion chamber 5 when the intake valve 7 is opened can be estimated from the opening timing of the intake valve 7. Further, based on the pressure in the intake passage when the intake valve 7 is opened, particularly the pressure in the intake port 8, and the pressure of the combustion gas in the combustion chamber 5 when the intake valve 7 is opened, The amount of blow-back can be estimated.

  Of the fuel adhering to the wall surface of the intake port 8, the amount of fuel released from the wall surface of the intake port 8 due to the return of the combustion gas (hereinafter referred to as "wall surface separation fuel amount") The relationship is as shown in FIG. Therefore, the amount of fuel desorbed from the wall accompanying the blowback of the combustion gas based on the combustion state of the air-fuel mixture in the previous cycle, the closing timing of the exhaust valve 9, the opening timing of the intake valve 7, and the pressure in the intake passage. Can be estimated.

  Further, in the present embodiment, the amount of air passing through the intake port 8 in the current cycle is detected by the intake air amount detector 16, the temperature of the engine coolant is detected by a water temperature sensor (not shown), and the current cycle is detected. The fuel injection amount at is detected. Based on the fuel injection amount in the current cycle, the amount of air passing through the intake port 8, and the engine coolant temperature, the amount of fuel adhering to the wall surface of the intake port 8 out of the fuel injected from the fuel injection valve 13 is Based on the amount of air that is detected and passes through the intake port 8, it is possible to estimate the amount of wall surface separation fuel that accompanies the intake of air.

  As described above, according to the present embodiment, the amount of fuel desorbed from the wall surface accompanying the blow-back of combustion gas, the amount of fuel adhering to the wall surface of the intake port 8 as a result of fuel injection, and the amount of fuel desorbed from the wall surface as a result of air intake. And the change amount of the fuel amount adhering to the wall surface of the intake port 8 in the current cycle can be estimated based on these. Then, by repeating such calculation, it is possible to estimate the wall surface attached fuel amount in each cycle.

  5 and 6 are flowcharts showing a control routine of the exhaust early closing execution control by the control device of the present embodiment. The illustrated control routine is performed by interruption at regular time intervals.

  In the control routine shown in FIGS. 5 and 6, first, in step S10, it is determined whether or not the engine operation state is a deceleration operation state or an idle operation state. If it is determined in step S10 that the vehicle is decelerating or idling, the process proceeds to step S11. In step S11, it is determined whether or not fuel cut control (F / C control) is being executed. If it is determined in step S11 that the fuel cut control is not being executed, that is, if it is determined that the fuel cut control is not being executed while the vehicle is decelerating or idling, the process proceeds to step S12. In step S12, in addition to the output torque of the internal combustion engine up to the previous cycle, the limit torque is calculated based on various parameters representing the operating state of the internal combustion engine such as the engine speed and the engine load. Next, in steps S13 and S14, it is determined whether or not it is immediately after the end of the fuel cut control and whether or not the output torque (detected torque) detected by the torque sensor (not shown) is smaller than the limit torque. . In steps S13 and S14, when it is determined not immediately after the end of the fuel cut control and the detected torque is smaller than the limit torque, the process proceeds to step S15, and the early exhaust closing control is prohibited. On the other hand, if it is determined in steps S13 and S14 that the fuel cut control has just ended or that the detected torque is greater than or equal to the limit torque, the process proceeds to step S16, and the exhaust early closing control is executed.

  On the other hand, if it is determined in step S11 that the fuel cut control is being performed, that is, if it is determined that the fuel cut control is being performed while the vehicle is decelerating or idling, the process proceeds to step S17. . In step S17, the amount of fuel attached to the wall surface to the intake port 8 is calculated by the method described above. Next, in step S18, it is determined whether or not the wall surface attached fuel amount calculated in step S17 is smaller than the limit fuel amount. If it is determined in step S18 that the wall-attached fuel flow rate is smaller than the limit fuel amount, the process proceeds to step S19, and the exhaust early closing control is prohibited. On the other hand, when it is determined in step S18 that the amount of fuel attached to the wall surface is equal to or greater than the above limit fuel amount, the routine proceeds to step S20, where exhaust early closing control is executed.

  On the other hand, if it is determined in step S10 that the engine operating state is during deceleration operation or idle operation, the process proceeds to step S21. In step S21, it is determined whether or not it is immediately after the end of the fuel cut control. Here, the term “immediately after the end of the fuel cut control” means that, for example, after the end of the fuel cut control, a predetermined period of time that is expected to be required for the amount of fuel attached to the wall surface to return to the normal amount has not elapsed. Means cases. If it is determined in step S21 that the fuel cut control has just ended, that is, if it is determined that the fuel cut control has not ended during deceleration operation or idle operation but immediately after the fuel cut control ends, the routine proceeds to step S22 and the exhaust gas is exhausted quickly. Close control is executed. On the other hand, if it is determined in step S21 that it is not immediately after the end of the fuel cut control, that is, if it is determined that the vehicle is not being decelerated or idling and is not immediately after the end of the fuel cut control, the routine proceeds to step S23 and the exhaust is performed. The early closing control is prohibited and the control routine is terminated.

  Next, the control apparatus of 2nd embodiment of this invention is demonstrated. The control device of the second embodiment is basically the same in configuration and control as the first embodiment. However, in the control device of the second embodiment, when the exhaust early closing control execution condition is satisfied during the deceleration operation of the internal combustion engine, if the output torque of the internal combustion engine is lower than the limit torque, the exhaust early The ignition timing is advanced by the spark plug 6 instead of prohibiting the execution of the closing control.

  In general, when the ignition timing is advanced, combustion of the air-fuel mixture in the combustion chamber 5 is performed early, so that the combustion energy obtained by the combustion of the air-fuel mixture is efficiently converted into kinetic energy of the piston. As a result, the output torque of the internal combustion engine can be increased. Therefore, according to this embodiment, when the output torque of the internal combustion engine is lower than the limit torque or expected to be lower than the limit torque, the output torque can be supplemented by advancing the ignition timing. Thereby, it can prevent that a big torque shock arises or an internal combustion engine stops.

  That is, according to the present embodiment, during the low load operation of the internal combustion engine, the early exhaust gas closing control promotes the adhesion of the fuel to the intake port and the atomization of the fuel injected from the fuel injection valve 13, and is constant. By advancing the ignition timing under the above conditions, it is possible to prevent a large torque shock or the internal combustion engine from stopping. Therefore, according to the present embodiment, inappropriate torque fluctuations can be prevented while keeping the combustion of the internal combustion engine as good as possible. In particular, during idling of the internal combustion engine (except during cold start), there may be a case where the hydraulic pressure sufficient to drive the exhaust variable valve timing mechanism A cannot be obtained by the hydraulic pump. In such a case, the exhaust valve 9 cannot be changed, so that the exhaust early closing control cannot be prohibited. Therefore, in such a case, it is effective to suppress the occurrence of inappropriate torque fluctuation by advancing the ignition timing.

  In the above, the case of an internal combustion engine having an exhaust turbocharger has been described as an example. However, the present invention is not limited to this, and can be similarly applied to an internal combustion engine having no exhaust turbocharger.

It is a figure which shows the whole internal combustion engine in which the control apparatus of this invention is used. It is a figure which shows an exhaust variable valve timing mechanism. It is a figure which shows the valve opening timing and valve closing timing of an exhaust valve. It is a figure which shows the relationship between the amount of return of combustion gas, and the amount of wall surface separation fuel. It is a part of flowchart which shows the control routine of exhaust early closing execution control. It is a part of flowchart which shows the control routine of exhaust early closing execution control.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine body 2 Cylinder block 3 Cylinder head 4 Piston 5 Combustion chamber 7 Intake valve 8 Intake port 9 Exhaust valve 10 Exhaust port 13 Fuel injection valve 50 Exhaust valve drive camshaft A Variable valve timing mechanism

Claims (9)

A control device for an internal combustion engine comprising a fuel injection valve for injecting fuel into an intake port and an exhaust variable valve timing mechanism capable of changing the valve timing of the exhaust valve. When the exhaust valve close timing is advanced from the intake top dead center and the exhaust valve closes when the intake valve is opened, the control device performs the exhaust early closing control for causing the combustion gas in the combustion chamber to flow backward into the intake port .
A torque detecting means for detecting an output torque output by the engine body;
During deceleration operation of the internal combustion engine, when the output torque detected by the torque detecting means is expected to be smaller than the limit torque even when the exhaust early closing control execution condition is satisfied, A control device that prohibits execution of the exhaust early closing control. A control device for an internal combustion engine comprising a fuel injection valve for injecting fuel into an intake port and an exhaust variable valve timing mechanism capable of changing the valve timing of the exhaust valve. When the exhaust valve close timing is advanced from the intake top dead center and the exhaust valve closes when the intake valve is opened, the control device performs the exhaust early closing control for causing the combustion gas in the combustion chamber to flow backward into the intake port .
A torque detecting means for detecting an output torque output by the engine body;
During deceleration operation of the internal combustion engine, when the output torque detected by the torque detecting means is expected to be smaller than the limit torque even when the exhaust early closing control execution condition is satisfied, A control device that advances the ignition timing. A control device for an internal combustion engine comprising a fuel injection valve for injecting fuel into an intake port and an exhaust variable valve timing mechanism capable of changing the valve timing of the exhaust valve. When the exhaust valve close timing is advanced from the intake top dead center and the exhaust valve closes when the intake valve is opened, the control device performs the exhaust early closing control for causing the combustion gas in the combustion chamber to flow backward into the intake port .
During the deceleration operation of the internal combustion engine, even when the exhaust early closing control execution condition is satisfied, if the engine speed is expected to be lower than the limit rotational speed, the exhaust early closing control is performed. A control device that prohibits execution. A control device for an internal combustion engine comprising a fuel injection valve for injecting fuel into an intake port and an exhaust variable valve timing mechanism capable of changing the valve timing of the exhaust valve. When the exhaust valve close timing is advanced from the intake top dead center and the exhaust valve closes when the intake valve is opened, the control device performs the exhaust early closing control for causing the combustion gas in the combustion chamber to flow backward into the intake port .
When the internal combustion engine is decelerating, the ignition timing is advanced if the engine speed is expected to be lower than the limit speed even when the exhaust early closing control execution condition is satisfied. ,Control device.   During execution of fuel cut control for stopping fuel injection from the fuel injection valve, the amount of fuel adhering to the wall surface on the intake port wall surface is reduced even when the exhaust early closing control execution condition is satisfied. The control device according to any one of claims 1 to 4, wherein when the amount of fuel is smaller than a limit fuel amount, execution of the exhaust early closing control is prohibited regardless of output torque and engine speed.   During execution of fuel cut control for stopping fuel injection from the fuel injection valve, the advance amount of the closing timing of the exhaust valve in the exhaust early closing control according to the amount of fuel adhering to the wall surface of the intake port The control apparatus for an internal combustion engine according to any one of claims 1 to 4, which controls the engine.   The amount of fuel adhering to the wall surface is based on the combustion state of the previous cycle, the valve timing of the intake and exhaust valves, the pressure in the intake passage, the amount of air passing through the intake port of the current cycle, and the fuel injection amount of the current cycle. The control device according to claim 5 or 6, which is estimated. The control according to any one of claims 5 to 7 , wherein the exhaust early closing control is executed immediately after the fuel cut control is finished, even if the exhaust early closing control execution condition is not satisfied. apparatus.   The exhaust valve advance angle amount in the exhaust early closing control is set according to the amount of fuel adhering to the wall surface at the end of the fuel cut control when the exhaust early closing control is executed immediately after the fuel cut control is finished. The control device described.

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