JP6123759B2 - Engine control device - Google Patents

Description

  The present invention is provided between the all-cylinder operation in which the combustion of the air-fuel mixture is performed in all the cylinders and the reduced-cylinder operation in which the combustion in the specific cylinder is stopped and the specific cylinder is brought into a resting state. The present invention relates to a device for controlling a switchable engine.

  2. Description of the Related Art Conventionally, in the field of a multi-cylinder engine having a plurality of cylinders, a technique for reducing cylinder operation is known in which combustion in some cylinders is stopped and the engine is stopped.

  Here, since the number of operating cylinders, that is, the number of output cylinders, decreases during the reduced-cylinder operation, the output of the entire engine may be reduced. Therefore, normally, during the reduced-cylinder operation, in order to increase the output of the operating cylinder, control is performed to increase the amount of each air sucked into the operating cylinder, that is, the intake amount.

  However, since there is a delay in the change in the intake air amount, even if the control for increasing the intake air amount is performed at the time of switching from the all cylinder operation to the reduced cylinder operation, the intake air amount does not increase immediately. There is a problem that the output is lowered and torque shock occurs.

  In response to this problem, Patent Document 1 discloses that a throttle valve provided in an intake passage communicating with each cylinder before stopping combustion of some cylinders when switching from full cylinder operation to reduced cylinder operation. An apparatus is disclosed that is configured to stop the combustion of some cylinders after changing the opening to the opening side so as to approach the opening at the time of reduced-cylinder operation, increasing the intake air amount for all cylinders, respectively. ing.

JP 11-336575 A

  In the device of Patent Document 1, since the intake air amount of each cylinder is increased before the combustion of some cylinders is stopped, the intake air amount of the operating cylinder is insufficient when the combustion of the cylinder is stopped, that is, when the reduced cylinder operation is started. Can be suppressed. However, simply increasing the intake air amount of each cylinder before the start of the reduced cylinder operation, that is, in a state where combustion is being performed in all cylinders, increases the output of the entire engine before starting the reduced cylinder operation. As a result, a torque shock occurs.

  The present invention has been made in view of the above circumstances, and provides an engine control device that can more reliably avoid the occurrence of a torque shock when switching from all-cylinder operation to reduced-cylinder operation. For the purpose.

In order to solve the above-described problems, the present invention provides a plurality of cylinders having an intake valve and an exhaust valve, and an ignition that is provided in each cylinder and applies ignition energy to an air-fuel mixture in these cylinders. All-cylinder operation in which combustion of the air-fuel mixture is performed in all the cylinders, and a throttle valve provided in an intake passage connected to each cylinder and capable of changing the amount of air sucked into these cylinders The reduction is performed when the operating state of the engine is in a predetermined reduced-cylinder operation region , and combustion in a specific cylinder among the plurality of cylinders is stopped and the specific cylinder is brought into a resting state. A device for controlling an engine that can be switched between cylinder operation and a valve stop mechanism that switches between a state in which the intake valve and the exhaust valve of the specific cylinder can be opened and closed and a state in which the valve is held closed; Above valve stop mechanism, throttle And a control means for controlling each part of the engine including the ignition means, and the control means reduces after a request for switching from all-cylinder operation to reduced-cylinder operation in which the specific cylinder is in a resting state. The throttle valve so that the amount of air sucked into each cylinder is larger than the amount of air during normal all-cylinder operation for which no switching request is issued during at least a part of the switching period until the cylinder operation is started. In the state where the opening of the cylinder is changed, the valve stop mechanism is controlled so that the intake / exhaust valves of all the cylinders can be opened and closed, and the transient all-cylinder control in which combustion is performed in all the cylinders is performed, and the above switching request is issued. and, when the operating region of the engine is changed to the specific operating region where combustion stability is predetermined equal to or less than a predetermined value among the down cylinder operating range during the switching period, the actual the transient all-cylinder control After that, when the throttle valve opening is changed so that the amount of air sucked into each cylinder is larger than the amount of air during normal all-cylinder operation, the number of specified cylinders is smaller than the number of all cylinders. The valve stop mechanism is controlled so that the intake and exhaust valves of the cylinders larger than the number of cylinders can be opened and closed, and combustion is performed only in cylinders that are smaller than the number of all cylinders and larger than the number of the specific cylinders. The intermediate reduction cylinder control is performed when the switching request is made and the engine operating area is changed to an operation area excluding the specific operation area in the reduced cylinder operation area. Without performing the transient all-cylinder control, the valve stop mechanism is controlled so that the intake and exhaust valves of the specific cylinder are held closed, and combustion in the specific cylinder is stopped, and the transient During all cylinder control The ignition timing of the ignition means is retarded so as to cancel the change in engine torque caused by the increase in the amount of air sucked into each cylinder, and the air sucked into each cylinder during the intermediate cylinder reduction control The ignition timing of the ignition means is changed so as to cancel the change in engine torque caused by the increase in the amount and the change in the number of cylinders in which combustion is being performed. The number is larger than the number of cylinders in which combustion is stopped (claim 1).

  According to the present invention, during the switching period from all-cylinder operation to reduced-cylinder operation, transient all-cylinder control is performed, and the intake air amount is increased before the start of reduced-cylinder operation that stops combustion in a specific cylinder. Therefore, at the start of the reduced-cylinder operation, the intake amount of each operating cylinder (cylinder that has been burned and output) is insufficient and the output of the operating cylinder, that is, the engine torque decreases. This can be avoided more reliably. Moreover, in the transient all-cylinder control, while increasing the intake air amount of each cylinder in this way, the ignition timing is retarded so as to cancel the increase in engine torque caused by the increase in the intake air amount. Therefore, it is possible to suppress an increase in engine torque accompanying an increase in the intake air amount of each cylinder, and more reliably avoid an increase or decrease in engine torque, that is, a torque shock, before and after switching from all-cylinder operation to reduced-cylinder operation. can do.

  Here, as described above, when the ignition timing is changed to the retard side, if the retard amount becomes excessively large, combustion may become unstable and misfire may occur. Alternatively, if the retard amount of the ignition timing is kept small to avoid misfire or the like, there arises a problem that the increase in engine torque cannot be sufficiently suppressed. On the other hand, in the present invention, during the switching period from the all-cylinder operation to the reduced-cylinder operation, the number of cylinders to be burned is increased to the total number and the specific number while increasing the intake air amount after performing the transient all-cylinder control. Since the intermediate cylinder reduction control is performed to reduce the number of operating cylinders, an increase in engine torque accompanying an increase in intake air amount can be suppressed by reducing the number of operating cylinders, and the retard amount of ignition timing is excessive. Can be avoided. In addition, during this intermediate reduction control, the ignition timing is controlled to the timing when the change in the engine torque caused by the change in the number of output cylinders and the increase in the intake air amount is canceled. At the time of switching, it is possible to more reliably suppress fluctuations in the engine torque and to ensure better drivability.

Moreover, in the present invention, the control means only when the combustion stability is a switching request to the reduced-cylinder operation from the all-cylinder operation in a preset operating region equal to or less than a predetermined value was, the intermediate down It has implemented a cylindrical control.

  Here, the combustion stability is an index for indicating the difficulty of misfire, and is obtained by dividing the minimum value of the engine torque when burned multiple times under the same conditions by the average value or multiple times under the same conditions. The probability that misfire does not occur when burned can be used.

In this case, the intermediate reduction cylinder control is performed in the operation region where the combustion stability falls below a predetermined value due to the retard of the ignition timing accompanying the execution of the transient all cylinder control, and there is a high possibility that misfire occurs. It is possible to more reliably avoid misfires due to this retarded ignition timing, and to ensure combustion stability even when the ignition timing is retarded due to the implementation of transient all-cylinder control. Since the intermediate cylinder reduction control is stopped in the avoidable operating range, the number of operating cylinders in which combustion is performed becomes the number that is not the total number that can ensure stable engine behavior or the number other than the number at the time of cylinder reduction operation. It is possible to avoid that the behavior of is temporarily unstable.
In the present invention, the control means controls the valve stop mechanism so that the intake / exhaust valve of the cylinder in which the combustion is stopped is closed during the intermediate reduction control, and the intermediate reduction control. It is preferable to stop the intermediate cylinder reduction control and start the cylinder reduction operation when the number of cycles reaches a predetermined number after starting the intermediate cylinder reduction control at the time of execution (Claim 2).

  Further, in the present invention, when the above intermediate reduction cylinder control is performed, the number of cycles from when there is a request to switch from all cylinder operation to reduced cylinder operation until the first stop of combustion in a predetermined cylinder, Preferably, the number of cycles from when the combustion in the predetermined cylinder is stopped to when the combustion in the new cylinder is stopped next is set in advance (Claim 3).

  In this way, the control configuration can be simplified, and the number of operating cylinders in which combustion is performed is the total number capable of ensuring stable engine behavior or the number of cycles other than the number during reduced-cylinder operation. Can be avoided more reliably by preventing the engine behavior from becoming unstable.

  In the above configuration, the number of cycles is set for each engine speed, and is preferably set to be higher as the engine speed is higher.

  In this way, this time is avoided while the number of operating cylinders in which the combustion is performed becomes an excessive number of times other than the total number that can ensure stable engine behavior or the number when the reduced cylinder operation is performed. Can be appropriately secured according to the engine speed.

  As described above, according to the engine control apparatus of the present invention, it is possible to more reliably avoid the occurrence of a torque shock when switching from all-cylinder operation to reduced-cylinder operation.

1 is a schematic plan view showing an overall configuration of an engine according to an embodiment of the present invention. It is sectional drawing of an engine main body. (A) It is a figure which shows a valve stop mechanism when a pivot part is a locked state. (B) It is a figure which shows the valve stop mechanism before a pivot part transfers to a lock release state. (C) It is a figure which shows a valve stop mechanism when a pivot part is a lock release state. It is the figure which showed the path | route of the hydraulic fluid of a valve stop mechanism. It is a block diagram which shows the control system of an engine. It is the figure which showed the all cylinder operation area | region and the reduced cylinder operation area | region. It is the flowchart which showed the control procedure at the time of the switch from all cylinder operation to reduction cylinder operation. It is the figure which showed the time change of each parameter at the time of implementing the control which concerns on one Embodiment of this invention in operation areas other than a specific operation area. It is the figure which showed the time change of each parameter at the time of implementing the control which concerns on the comparative example of this invention. It is the figure which showed the time change of each parameter at the time of implementing control which concerns on the other comparative example of this invention. It is the figure which showed the time change of each parameter at the time of implementing the control which concerns on one Embodiment of this invention in a specific driving | operation area | region. It is the figure which showed the time change of each parameter at the time of implementing the control which concerns on the comparative example of this invention in a specific driving | operation area | region.

(1) Overall Configuration of Engine FIG. 1 is a diagram showing an embodiment of an engine to which a control device of the present invention is applied. The engine shown in the figure is a 4-cycle multi-cylinder gasoline engine mounted on a vehicle as a power source for traveling. Specifically, this engine is generated by an in-line four-cylinder engine main body 1 having four cylinders 2A to 2D arranged in a straight line, an intake passage 30 for introducing air into the engine main body 1, and the engine main body 1. And an exhaust passage 35 for discharging the exhaust gas.

  FIG. 2 is a cross-sectional view of the engine body 1. As shown in the figure, an engine body 1 includes a cylinder block 3 in which the four cylinders 2A to 2D are formed, a cylinder head 4 provided on the upper side of the cylinder block 3, and an upper side of the cylinder head 4. It has a cam cap 5 provided and a piston 11 inserted into each of the cylinders 2A to 2D so as to be slidable back and forth.

  A combustion chamber 10 is formed above the piston 11, and fuel mainly composed of gasoline injected from an injector 12 (FIG. 1) described later is supplied to the combustion chamber 10. The supplied fuel burns in the combustion chamber 10, and the piston 11 pushed down by the expansion force due to the combustion reciprocates in the vertical direction.

  The piston 11 is connected to a crankshaft 15 that is an output shaft of the engine body 1 via a connecting rod 14, and the crankshaft 15 rotates about the central axis in accordance with the reciprocating motion of the piston 11. Yes.

  As shown in FIG. 1, the cylinder head 4 includes an injector 12 that injects fuel (gasoline) toward the combustion chamber 10 of each of the cylinders 2 </ b> A to 2 </ b> D, and a mixture of fuel and air injected from the injector 12. An ignition plug (ignition means) 13 for supplying ignition energy by spark discharge is provided. In the present embodiment, a total of four injectors 12 are provided at a rate of one for each cylinder, and a total of four spark plugs 13 are also provided at a rate of one for each cylinder.

  In the four-cycle four-cylinder gasoline engine as in this embodiment, the pistons 11 provided in the cylinders 2A to 2D move up and down with a phase difference of 180 ° (180 ° CA) in crank angle. Correspondingly, the ignition timing in each of the cylinders 2A to 2D is also set to a timing shifted in phase by 180 ° CA. Specifically, in order from the left side of FIG. 1, assuming that the cylinder 2A is the first cylinder, the cylinder 2B is the second cylinder, the cylinder 2C is the third cylinder, and the cylinder 2D is the fourth cylinder, the first cylinder 2A → the third cylinder Ignition is performed in the order of 2C → fourth cylinder 2D → second cylinder 2B.

  The engine of the present embodiment is a variable cylinder engine capable of performing an operation in which two of the four cylinders 2A to 2D are deactivated and the remaining two cylinders are operated, that is, a reduced cylinder operation. For this reason, the ignition sequence as described above is for normal operation that is not reduced-cylinder operation (during all-cylinder operation in which all four cylinders 2A to 2D are operated). On the other hand, during the reduced-cylinder operation, the ignition operation of the spark plug 13 is prohibited in two cylinders (the first cylinder 2A and the fourth cylinder 2D in this embodiment) whose ignition order is not continuous, and ignition is performed by skipping one. become.

  As shown in FIGS. 1 and 2, the cylinder head 4 has an intake port 6 for introducing air (intake air) supplied from the intake passage 30 into the combustion chamber 10 of each cylinder 2A to 2D, and each cylinder 2A. An exhaust port 7 for leading the exhaust gas generated in the 2D combustion chamber 10 to the exhaust passage 35 and an opening on the combustion chamber 10 side of the intake port 6 for controlling the introduction of intake air through the intake port 6 An intake valve 8 that opens and closes and an exhaust valve 9 that opens and closes an opening of the exhaust port 7 on the combustion chamber 10 side in order to control gas discharge from the exhaust port 7 are provided. In the present embodiment, a total of eight intake valves 8 are provided at a rate of two per cylinder, and a total of eight exhaust valves 9 are also provided at a rate of two per cylinder.

  As shown in FIG. 1, the intake passage 30 includes four independent intake passages 31 communicating with the intake ports 6 of the cylinders 2 </ b> A to 2 </ b> D, and upstream ends of the individual intake passages 31 (on the upstream side in the intake flow direction). A surge tank 32 commonly connected to the end) and a single intake pipe 33 extending upstream from the surge tank 32. An openable / closable throttle valve 34 a for adjusting the flow rate of intake air introduced into the engine body 1 is provided in the middle of the intake pipe 33. The intake pipe 33 is provided with a valve actuator 34b for driving the throttle valve 34a. The throttle valve 34a is opened and closed by the valve actuator 34b.

  The exhaust passage 35 has four independent exhaust passages 36 communicating with the exhaust ports 7 of the cylinders 2A to 2D, and one downstream end portion (end portion on the downstream side in the exhaust gas flow direction) of each independent exhaust passage 36. And a single exhaust pipe 38 extending downstream from the collective portion 37.

(2) Valve Mechanism Next, a mechanism for opening and closing the intake valve 8 and the exhaust valve 9 will be described in detail with reference to FIGS. The intake valve 8 and the exhaust valve 9 are driven to open and close in conjunction with the rotation of the crankshaft 15 by a pair of valve mechanisms 28 and 29 (FIG. 2) disposed in the cylinder head 4.

  The valve operating mechanism 28 for the intake valve 8 includes a return spring 16 that urges the intake valve 8 in the closing direction (upward in FIG. 2), a cam shaft 18 that rotates in conjunction with the rotation of the crankshaft 15, and a cam shaft. 18, a cam portion 18 a provided so as to rotate integrally with the shaft 18, a swing arm 20 that is periodically pressed by the cam portion 18 a, and a pivot portion 22 that serves as a swing fulcrum of the swing arm 20.

  Similarly, the valve operating mechanism 29 for the exhaust valve 9 includes a return spring 17 that urges the exhaust valve 9 in the closing direction (upward in FIG. 2), and a cam shaft 19 that rotates in conjunction with the rotation of the crankshaft 15. A cam portion 19a provided to rotate integrally with the cam shaft 19, a swing arm 21 periodically pressed by the cam portion 19a, and a pivot portion 22 serving as a swing fulcrum of the swing arm 20. ing.

  By the valve mechanisms 28 and 29 as described above, the intake valve 8 and the exhaust valve 9 are driven to open and close as follows. That is, when the camshafts 18 and 19 are rotated with the rotation of the crankshaft 15, the cam followers 20a and 21a that are rotatably provided at the substantially central portions of the swing arms 20 and 21 are periodically lowered by the cam portions 18a and 19a. While being pressed, the swing arms 20 and 21 swing and displace with the pivot portion 22 supporting one end thereof as a fulcrum. Accordingly, the other ends of the swing arms 20 and 21 press the intake and exhaust valves 8 and 9 downward against the urging force of the return springs 16 and 17, thereby opening the intake and exhaust valves 8 and 9. To do. The intake / exhaust valves 8 and 9 once opened are returned to the closed position again by the urging force of the return springs 16 and 17.

  The pivot portion 22 is supported by a known hydraulic lash adjuster 24, 25 (hereinafter abbreviated as “HLA”, which is an acronym for “Hydraulic Lash Adjuster”) that automatically adjusts the valve clearance to zero. Among them, the HLA 24 automatically adjusts the valve clearances of the second cylinder 2B and the third cylinder 2C on the center side in the cylinder row direction, and the HLA 25 is the first cylinder 2A and the first cylinders at both ends in the cylinder row direction. The valve clearance of the 4-cylinder 2D is automatically adjusted.

The HLA 25 for the first cylinder 2A and the fourth cylinder 2D has a function of switching whether the intake / exhaust valves 8 and 9 are opened / closed or stopped depending on whether the engine is in a reduced cylinder operation or an all cylinder operation. That is, the HLA 25 opens and closes the intake and exhaust valves 8 and 9 of the first and fourth cylinders 2A and 2D during the entire cylinder operation of the engine, while the first and fourth cylinders 2A and 2D operate during the reduced cylinder operation of the engine. The intake / exhaust valves 8 and 9 are stopped in the closed state. For this reason, the HLA 25 has a valve stop mechanism 25a shown in FIG. 3 as a mechanism for stopping the opening / closing operation of the intake and exhaust valves 8, 9. On the other hand, the HLA 24 for the second cylinder 2B and the third cylinder 2C does not include the valve stop mechanism 25a and does not have a function of stopping the opening / closing operation of the intake and exhaust valves 8 and 9. Below, in order to distinguish these HLA24 and 25, HLA25 provided with the valve stop mechanism 25a
This is particularly referred to as S-HLA25 (abbreviation of Switchable-Hydraulic Lash Adjuster).

  The valve stop mechanism 25a of the S-HLA 25 includes a bottomed outer cylinder 251 that accommodates the pivot portion 22 so as to be slidable in the axial direction, and two through-holes provided on the peripheral surface of the outer cylinder 251 so as to face each other. A pair of lock pins 252 capable of entering and exiting 251a and capable of switching the pivot portion 22 between a locked state and an unlocked state; a lock spring 253 that urges the lock pins 252 radially outward; and an inner bottom portion of the outer cylinder 251 And a lost motion spring 254 that presses and urges the pivot portion 22 above the outer cylinder 251.

  As shown in FIG. 3A, when the lock pin 252 is fitted in the through hole 251a of the outer cylinder 251, the pivot portion 22 is in a locked state in which it is fixed while protruding upward. In this locked state, as shown in FIG. 2, the top portion of the pivot portion 22 serves as the swing fulcrum of the swing arms 20 and 21, so that the cam portions 18a and 19a rotate the cam followers 20a and 21a as the cam shafts 18 and 19 rotate. When pressed downward, the intake / exhaust valves 8, 9 are displaced downward against the urging force of the return springs 16, 17, and the intake / exhaust valves 8, 9 are opened. Therefore, at the time of all cylinder operation in which all the four cylinders 2A to 2D are operated, the intake / exhaust valves 8 and 9 of the first and fourth cylinders 2A and 2D are opened and closed by the pivot portion 22 being locked. The

  To release the locked state as described above, the pair of lock pins 252 are pressed radially inward. Then, as shown in FIG. 3B, the pair of lock pins 252 move in a direction approaching each other (in the radial direction of the outer cylinder 251) against the tensile force of the lock spring 253. Thereby, the fitting between the lock pin 252 and the through hole 251a of the outer cylinder 251 is released, and the pivot portion 22 is in an unlocked state in which it can move in the axial direction.

  With the change to the unlocked state, the pivot portion 22 is pressed downward against the urging force of the lost motion spring 254, thereby realizing the valve stop state as shown in FIG. That is, the return springs 16 and 17 that urge the intake and exhaust valves 8 and 9 upward have a stronger urging force than the lost motion spring 254 that urges the pivot portion 22 upward. In the released state, when the cam portions 18a and 19a press the cam followers 20a and 21a downward as the cam shafts 18 and 19 rotate, the top portions of the intake and exhaust valves 8 and 9 become the swing fulcrum of the swing arms 20 and 21. The pivot portion 22 is displaced downward against the urging force of the lost motion spring 254. That is, the intake / exhaust valves 8 and 9 are maintained in a closed state. For this reason, during the reduced-cylinder operation in which the first and fourth cylinders 2A and 2D are deactivated, the intake and exhaust valves 8 and 9 of the first and fourth cylinders 2A and 2D are set by releasing the valve stop mechanism 25a. Is stopped and the intake and exhaust valves 8 and 9 are maintained in the closed state.

  The valve stop mechanism 25a is a hydraulic drive type, and the valve stop mechanism 25a, more specifically, the lock pin 252 of the valve stop mechanism 25a is driven by hydraulic pressure. The lock pin 252 enters and exits the through hole 251a according to the supplied hydraulic pressure, and the lock pin 252 and the through hole 251a of the outer cylinder 251 are fitted / released.

  As shown in FIG. 4, hydraulic oil is supplied from the oil pump 41 to the valve stop mechanism 25a. A solenoid valve 42 is provided in the oil path between the oil pump 41 and the valve stop mechanism 25a, and the solenoid valve 42 changes the hydraulic pressure supplied from the oil pump 41 to the valve stop mechanism 25a. Specifically, when the solenoid valve 42 is not energized, that is, when the solenoid valve 42 is OFF, the oil path between the oil pump 41 and the valve stop mechanism 25a is closed by the solenoid valve 42, and the lock pin 252 The outer cylinder 251 is fitted with the through hole 251a, the pivot portion 22 is locked, and the intake / exhaust valve is driven to open and close accordingly. On the other hand, when the solenoid valve 42 is energized, that is, when the solenoid valve 42 is ON, the oil passage between the oil pump 41 and the valve stop mechanism 25a is opened, and the lock pin 252 and the through hole 251a of the outer cylinder 251 Is released, the pivot portion 22 is unlocked, and the intake and exhaust valves are held closed accordingly.

  As shown in FIG. 4, in this embodiment, one solenoid valve 42 is provided for one cylinder, and a total of two solenoid valves 42 are provided. Specifically, one first cylinder solenoid valve 42a is connected to a valve stop mechanism 25a provided in the intake valve 8 of the first cylinder 2A and a valve stop mechanism 25a provided in the exhaust valve 9 of the first cylinder 2A. The hydraulic pressure to be supplied is changed at the same time, and the other fourth cylinder solenoid valve 42b is a valve stop mechanism 25a provided in the intake valve 8 of the fourth cylinder 2D and a valve stop provided in the exhaust valve 9 of the fourth cylinder 2D. The hydraulic pressure supplied to the mechanism 25a is changed simultaneously. In this embodiment, the solenoid valves 42a and 42b are individually driven, so that the intake / exhaust valves 8 and 9 of the first cylinder and the intake / exhaust valves 8 and 9 of the fourth cylinder are opened and closed. Can be changed individually.

(3) Control system Next, an engine control system will be described. Each part of the engine of the present embodiment is comprehensively controlled by an ECU (engine control unit, control means) 50 shown in FIG. As is well known, the ECU 50 is a microprocessor including a CPU, a ROM, a RAM, and the like.

  The engine and the vehicle are provided with a plurality of sensors for detecting the state quantities of the respective parts, and information from each sensor is input to the ECU 50.

  For example, the cylinder block 3 is provided with a crank angle sensor SN1 that detects a rotation angle (crank angle) and a rotation speed of the crankshaft 15. The crank angle sensor SN1 outputs a pulse signal in accordance with the rotation of a crank plate (not shown) that rotates integrally with the crankshaft 15. Based on the pulse signal, the rotation angle and the rotation speed of the crankshaft 15 are output. That is, the engine speed is specified.

  The cylinder head 4 is provided with a cam angle sensor SN2. The cam angle sensor SN2 outputs a pulse signal according to the passage of the teeth of the signal plate that rotates integrally with the camshaft (18 or 19), and this signal and the pulse signal from the crank angle sensor SN1 Based on this, cylinder discrimination information indicating which cylinder is in which stroke is specified.

  The surge tank 32 of the intake passage 30 is provided with an intake air amount sensor SN3 that detects the amount of air introduced through the surge tank 32 into each of the cylinders 2A to 2D, that is, the intake air amount. An intake pressure sensor SN4 that detects pressure is provided.

  The vehicle is provided with an accelerator opening sensor SN5 that detects an opening degree of an accelerator pedal (accelerator opening degree) that is operated by a driver and that is not shown. A water temperature sensor SN6 that detects the temperature of the coolant that cools the engine body 1 is also provided.

  The ECU 50 is electrically connected to these sensors SN1 to SN6, and based on signals input from the sensors, the above-described various information (crank angle, engine speed, intake air amount, intake pressure, accelerator opening) Degree, cooling water temperature).

  And ECU50 controls each part of an engine, performing various determination, a calculation, etc. based on the input signal from each said sensor SN1-SN6. That is, the ECU 50 is electrically connected to the injector 12, spark plug 13, valve actuator 34b (throttle valve 34a), and valve stop mechanism solenoid valve 42. Each outputs a control signal for driving. In this embodiment, there are a total of four sets of injectors 12 and spark plugs 13 at a rate of one set per cylinder. In FIG. 5, the injectors 12 and the spark plugs 13 are each represented by one block. . Further, one valve stop mechanism solenoid valve 42 is provided for each of the valve stop mechanism 25a of the first cylinder 2A and the valve stop mechanism 25a of the fourth cylinder 2D, for a total of two valve stop mechanisms. There is a solenoid valve 42 for use, and this is shown in one block in FIG.

  More specific functions of the ECU 50 will be described. The ECU 50 includes an operation request determination unit 51, a throttle valve control unit 52, a spark plug control unit 53, an injector control unit 54, and a valve stop mechanism control unit 55 as functional elements.

  The operation request determination unit 51 determines the engine operation based on the engine operating conditions (engine load, engine speed, engine water temperature, etc.) specified from the detected values of the accelerator opening sensor SN4, the crank angle sensor SN1, and the water temperature sensor SN6. It is determined whether to select a reduced-cylinder operation or an all-cylinder operation. For example, as shown in FIG. 6, the operation request determination unit 51 pauses the first and fourth cylinders 2A and 2D when the engine load and the engine speed are in a specific operation region A1 that is relatively low (first 2) It is determined that there is a request for reduced-cylinder operation in which only the third cylinders 2B and 2C are operated. Conversely, when the engine load and the engine speed are in the remaining operation region A2 excluding the specific operation region A1, it is determined that there is a request for all-cylinder operation to operate all the first to fourth cylinders 2A to 2D. . In addition, the operation request determination unit 51 determines that the all-cylinder operation is performed when it is cold or acceleration / deceleration is severe. For example, when the engine water temperature detected by the water temperature sensor SN6 is equal to or lower than a predetermined value or when the change rate of the accelerator opening detected by the accelerator opening sensor SN5 is large, the operation request determination unit 51 operates all cylinders. Is determined to be implemented.

  The throttle valve control unit 52 controls the opening of the throttle valve 34a, that is, the intake air amount that is the amount of air taken into each cylinder. The spark plug controller 53 controls the spark plug 13. The injector control unit 54 controls the injector 12. The valve stop mechanism control unit 55 controls the solenoid valves 42a and 42b for each valve stop mechanism, respectively, and the hydraulic pressure supplied to the valve stop mechanism 25a of the S-HLA 25, that is, intake and exhaust of the first and fourth cylinders 2A and 2D. The opening and closing operations of the valves 8 and 9 are respectively changed.

Details of the control contents of the control units 52 to 55 will be described next.
(4) Control content (4-1) Basic control First, the control content of each control unit other than when switching from all-cylinder operation to reduced-cylinder operation, that is, each control unit during normal all-cylinder operation and reduced-cylinder operation The contents of control will be described.

  The throttle valve control unit 52 controls the valve actuator 34b so as to achieve the target torque set according to the detected value of the accelerator opening sensor SN5, that is, the amount of depression of the accelerator pedal, and the opening of the throttle valve 34a. To change.

  Specifically, the throttle valve control unit 52 obtains the required cylinder charging efficiency, which is a charging efficiency necessary for realizing the target torque, based on the target torque, and is necessary for realizing the required cylinder charging efficiency. The required air amount in the intake passage which is the amount of air in the intake passage 30 is obtained. Specifically, the required air amount in the intake passage is based on the required cylinder filling efficiency and the surge tank reference volume efficiency that is preset according to the engine operating state, for example, the engine speed, the phase of the intake VVT 29a, and the like. Calculated.

  Next, the throttle valve control unit 52 controls the throttle valve 34a based on the required air amount in the intake passage, the current air amount in the intake passage 30, and the air flow rate taken into the cylinder from the intake passage 30. A required throttle passage air flow rate, which is a target value of the passing air flow rate, is obtained. The throttle valve control unit 52 calculates the opening degree of the throttle valve (target throttle valve opening degree) necessary for realizing the air flow rate based on the required throttle passing air flow rate, Thus, the opening degree of the throttle valve 34a is controlled.

  The target throttle valve opening can be calculated using, for example, Bernoulli's theorem. In other words, the flow rate of air passing through the throttle valve 34a is determined by the ratio of the opening of the throttle valve 34a to the pressure ratio between the upstream side and the downstream side of the throttle valve 34a (the ratio of the pressure on the downstream side to the upstream side, hereinafter the throttle upstream / downstream pressure). Therefore, the pressure on the upstream side and the downstream side of the throttle valve 34a is detected by a sensor, and the target throttle valve opening can be calculated based on the detected value and the required throttle passage air flow rate. . Specifically, the opening degree of the throttle valve 34a, the throttle valve upstream / downstream pressure ratio, and the air flow rate passing through the throttle valve 34a are obtained in advance, and these relationships are stored in a map and detected from this map. The opening degree of the throttle valve 34a corresponding to the throttle upstream / downstream pressure ratio and the required throttle passage air flow rate may be extracted and set to the target throttle valve opening degree. For example, this map is set so that the opening degree of the throttle valve 34a increases as the throttle valve upstream / downstream pressure ratio is closer to 1 when the flow rate of air passing through the throttle valve 34a is constant.

  Here, since the number of cylinders to be operated / output decreases during the reduced cylinder operation, in order to generate the same engine output as in the all cylinder operation, the operating cylinders (second and third cylinders 2B, 2C) ) Needs to be larger than the output per cylinder during all cylinder operation. Therefore, during the reduced cylinder operation, it is necessary to increase the output (generated torque) per cylinder, and accordingly, it is necessary to increase the amount of air sucked into each cylinder (intake amount). In other words, the target value of the intake air amount per cylinder during the reduced cylinder operation is larger than the target value of the intake air amount per cylinder during the all cylinder operation. In order to increase the amount of air taken into each cylinder, the pressure in the intake passage 30 (pressure downstream of the throttle valve 34a) needs to be higher than when all cylinders are operating. Therefore, as a result, at the time of reduced cylinder operation, the throttle valve upstream / downstream pressure ratio becomes closer to 1 than at the time of all cylinder operation, and the opening of the throttle valve 34a at the time of reduced cylinder operation is the opening at the time of all cylinder operation. Is controlled to be larger (open side).

  The spark plug controller 53 switches the control of the spark plug 13 of the idle cylinders (first and fourth cylinders 2A and 2D) depending on whether the cylinder reduction operation or the all cylinder operation is performed. That is, when the engine is operating in all cylinders, the spark plug control unit 53 drives the spark plugs 13 of all the cylinders 2A to 2D to perform ignition. On the other hand, when the engine is in the reduced cylinder operation, the spark plug control unit 53 drives the spark plug 13 of the cylinder to stop combustion in the idle cylinders (first and fourth cylinders 2A and 2D). Ban.

  In addition, when operating the spark plug 13, the spark plug control unit 53 determines the ignition timing according to the operating conditions and issues an instruction to the spark plug 13. Specifically, the ignition plug control unit 53 stores a map of ignition timing preset for the engine speed and the engine load, and the ignition plug control unit 53 uses the map to determine the engine speed and the engine load. The ignition timing corresponding to the load is extracted, and the basic ignition timing is determined by correcting the extracted ignition timing based on the detected value of the intake pressure sensor SN4. Two types of maps for the ignition timing are prepared for reduced-cylinder operation and for all-cylinder operation, and a map corresponding to the operation is used.

  Here, if the determined basic ignition timing is excessively retarded, there is a risk of misfire. Therefore, in the present embodiment, the spark plug controller 53 determines the final ignition timing so that the ignition timing is not retarded beyond a preset retard limit. That is, the spark plug control unit 53 determines a timing on the more advanced side of the determined basic ignition timing and the retard limit as the final ignition timing. For example, the retard limit is preset and stored for each operating condition (engine speed, engine load, etc.), and the spark plug control unit 53 extracts the retard limit corresponding to the operating condition from this map. Compare with the basic ignition timing.

  The injector control unit 54 switches the control of the injector 12 of the idle cylinders (first and fourth cylinders 2A and 2D) according to whether the cylinder reduction operation or the all cylinder operation. That is, the injector control unit 54 performs fuel injection by driving the injectors 12 of all the cylinders 2A to 2D when the engine is operated in all cylinders, and on the other hand, when the engine is operated in reduced cylinders, The fuel injection to the deactivated cylinders (first and fourth cylinders 2A and 2D) is prohibited.

  Further, the injector control unit 54 determines the injection amount in accordance with the operating conditions (engine speed, engine load, and whether or not all cylinders are operated, etc.) when causing the injector 12 to perform fuel injection. An instruction is given to the injector 12.

  The valve stop mechanism control unit 55 switches the control of the solenoid valve 42 for the valve stop mechanism in accordance with the reduced cylinder operation or the all cylinder operation. That is, when the engine is operating in all cylinders, the valve stop mechanism controller 55 enables the intake / exhaust valves 8 and 9 of all the cylinders 2A to 2D to be opened and closed by turning off the solenoid valve 42. When the cylinder is in the reduced cylinder operation, the solenoid valve 42 for the valve stop mechanism is turned on to hold the intake and exhaust valves 8 and 9 of the deactivated cylinders (first and fourth cylinders 2A and 2D) closed.

(4-2) Control at the time of switching from all-cylinder operation to reduced-cylinder operation As described above, in the reduced-cylinder operation, in order to increase the output per cylinder of the operating cylinder compared to that during all-cylinder operation, The intake amount per cylinder is increased. However, since there is a delay in the change in the intake air amount, the combustion of the idle cylinders (first and fourth cylinders 2A and 2D) is stopped immediately after a request for switching from all-cylinder operation to reduced-cylinder operation is performed. If the operation is started, the intake amount of the operating cylinders (the second and third cylinders 2B and 2C) is insufficient, and the engine torque may be reduced to cause a torque shock. Therefore, in this device, when the operation request determination unit 51 issues a request for switching from all-cylinder operation to reduced-cylinder operation, the intake air amount is reduced in order to avoid the occurrence of the torque shock while keeping all the cylinders in operation. The transient all-cylinder control that increases and retards the ignition timing is started. Then, the reduced-cylinder operation is started after the end of this control. In addition to this transient all-cylinder control, in addition to this transient all-cylinder control, the total number of cylinders to be deactivated is increased under specific operating conditions where it is impossible to avoid the occurrence of torque shock only by performing this control. Intermediate reduction control is carried out to a number (three in this embodiment) between (four in the present embodiment) and the number at the time of reduced cylinder operation (two in this embodiment).

(I) Control at the time of switching under operating conditions other than specific operating conditions First, the control contents when there is a request for switching from all-cylinder operation to reduced-cylinder operation under operating conditions other than the specific operating conditions described above. explain.

  When there is a request for switching from all-cylinder operation to reduced-cylinder operation, the throttle valve control unit 52 performs the transient all-cylinder control so that the intake air amount per cylinder becomes the intake air amount during the reduced-cylinder operation. Implement control to change the opening. As described above, the intake amount per cylinder during the reduced-cylinder operation needs to be larger than the intake amount per cylinder during the normal all-cylinder operation. Therefore, when there is a request for switching from all-cylinder operation to reduced-cylinder operation, the throttle valve control unit 52 changes the opening of the throttle valve 34a from the opening during normal all-cylinder operation, that is, from all-cylinder operation to reduced-cylinder operation. The intake air amount is increased toward the intake air amount during the reduced-cylinder operation so that the opening amount is more open than the opening degree immediately before the switch request is issued.

  In the present embodiment, when there is a request for switching from the all-cylinder operation to the reduced-cylinder operation, the throttle valve control unit 52 causes the intake amount per cylinder to be a larger amount during the reduced-cylinder operation than during the all-cylinder operation. In addition, the opening of the throttle valve 34a is changed to the open side. That is, in the present embodiment, the throttle valve control unit 52 starts the control for the reduced cylinder operation as soon as a request for switching from the all cylinder operation to the reduced cylinder operation is issued.

  On the other hand, the valve stop mechanism control unit 55 maintains the OFF state of the solenoid valves 42a and 42b for each valve stop mechanism even when there is a request for switching from all-cylinder operation to reduced-cylinder operation. The intake and exhaust valves can be opened and closed. Further, the injector control unit 54 and the spark plug control unit 53 also have the injector 12 and the spark plug so that the combustion in all the cylinders 2A to 2D is maintained even when there is a request for switching from the all-cylinder operation to the reduced-cylinder operation. 13 is controlled. That is, the injector control unit 54 and the spark plug control unit 53 stop the fuel injection and ignition of the deactivated cylinders (first and fourth cylinders 2A and 2D) even when there is a request for switching from all-cylinder operation to reduced-cylinder operation. Without performing fuel injection and ignition in all the cylinders 2A to 2D.

  As described above, in this device, even when the operation request determination unit 51 issues a request for switching from all-cylinder operation to reduced-cylinder operation, the intake and exhaust valves 8 and 9 of all the cylinders 2A to 2D are driven to open and close. Combustion is performed in all the cylinders 2A to 2D.

  Here, as described above, when there is a request for switching from all-cylinder operation to reduced-cylinder operation, the intake amount per cylinder is the intake amount during the reduced-cylinder operation by the throttle valve control unit 52, and the normal all-cylinder operation. It is made larger than the intake amount during operation. Therefore, if combustion is performed in all of the cylinders 2A to 2D in such a large intake amount state, the engine torque is the torque at the time of normal all-cylinder operation, that is, the torque immediately before the switching determination, and the driver It will be higher than the torque requested from

  Therefore, in this device, when there is a request to switch from all-cylinder operation to reduced-cylinder operation, the ignition timing is increased to a timing at which the increase in engine torque caused by the increase in the intake air amount can be avoided while increasing the intake air amount. Be retarded. That is, when there is a request for switching from all-cylinder operation to reduced-cylinder operation, the spark plug control unit 53 issues the ignition timing as the transient all-cylinder control, that is, the ignition timing during normal all-cylinder operation, that is, the above switching request. Control is performed so that the ignition timing is retarded from the immediately preceding ignition timing.

  Specifically, the spark plug control unit 53 calculates how much the actual intake air amount has increased with respect to the intake air amount during normal all-cylinder operation. A retardation amount corresponding to the increase amount of the engine torque corresponding to the increase amount of the intake air amount is calculated. In the present embodiment, the spark plug control unit 53 stores a map of the intake air amount increase amount and the retard amount that are set in advance for each operating condition (engine speed, engine load, etc.). Then, the retard amount corresponding to the operating condition and the calculated increase amount of the intake air amount is extracted. Then, the spark plug control unit changes the timing retarded by the calculated retard amount from the basic ignition timing during normal all-cylinder operation determined according to the procedure described in (4-1). It is determined as the ignition timing.

  The transient all-cylinder control (control that allows the intake and exhaust 8 and 9 to be opened / closed in all cylinders and increases the intake air amount while retarding the combustion and retards the ignition timing) This is carried out until the intake amount at the time of reduced-cylinder operation is increased, and when the intake amount per cylinder increases to the intake amount at the time of reduced-cylinder operation, intake / exhaust valves 8 of the deactivated cylinders (first and fourth cylinders 2A, 2D). , 9 are held closed, and the combustion of the deactivated cylinders (first and fourth cylinders 2A, 2D) is stopped and the reduced-cylinder operation is started.

(Ii) Control at the time of switching under a specific operating condition Here, basically, by executing the transient all-cylinder control, an increase in engine torque is avoided when switching from all-cylinder operation to reduced-cylinder operation. Can be avoided. However, if the ignition timing is excessively retarded, misfire occurs, which may cause torque shock. Therefore, in this device, when there is a request for switching from all-cylinder operation to reduced-cylinder operation, as described above, under specific operation conditions where there is a high possibility of misfire due to the retard of the ignition timing as described above, After performing the above-mentioned transient all-cylinder control, the intermediate reduction-cylinder control is performed so that the number of cylinders to be deactivated is between the total number and the number at the time of reduced-cylinder operation, and the engine torque is reduced by reducing the number of operating cylinders. The ignition timing is prevented from being retarded excessively in order to reduce the engine torque.

  In the present embodiment, when the combustion stability falls below the reference value due to the retard of the ignition timing in the transient all-cylinder control and is in a specific operation region (region indicated by C in FIG. 6), Assume that the operating conditions are met. That is, it is assumed that the specific operation condition is satisfied when the entire cylinder operation area A1 is changed to the specific operation area C included in the reduced cylinder operation area A2.

  Here, in this embodiment, the combustion stability is a value obtained by dividing the minimum value of the engine torque when burned multiple times under the same conditions by the average value, and the lower this value, the worse the combustion stability. A value representing is used. And the area | region where combustion stability becomes below a predetermined reference value (for example, 0.5) is made into the area | region where combustion stability is bad and misfire is easy to produce. More specifically, in this embodiment, the timing when the combustion stability becomes the reference value (0.5 or the like) is the misfire limit timing that is the ignition timing at which misfire occurs, and the ignition timing is the misfire limit timing. A value obtained by dividing the average value of the engine torque by the average value of the engine torque at the normal basic ignition timing, that is, by setting the ignition timing as the misfire limit timing, how much the engine torque can be reduced from the normal time. This value (hereinafter, this value is referred to as the torque reduction possibility rate) is less than a predetermined value, for example, less than 0.5, and the ignition timing is retarded to the misfire limit timing with the implementation of transient all cylinder control. However, the engine torque can only be reduced to less than a predetermined value times the normal torque (for example, 0.5 times), and when the transient all-cylinder control is performed, the intake air amount is increased while avoiding misfire. With Region is difficult to retarding the ignition timing to a timing that can avoid an increase in engine torque occurs, the specific operation region is set to (hereinafter, simply is referred specific region).

  The control content of each control unit at the time of switching under specific operating conditions (specific operating region C) will be described.

  When there is a request for switching from all-cylinder operation to reduced-cylinder operation in the specific operation region C, the throttle valve control unit 52 has a request for switching in another operation region described in (i). The same control (transient all-cylinder control, control for increasing the intake air amount) is performed.

  Specifically, the throttle valve control unit 52 performs the all-cylinder operation when there is a request for switching from the all-cylinder operation to the reduced-cylinder operation in the specific operation region C, that is, in accordance with the transition to the specific operation region C. Even when it is determined that there has been a request for switching from the reduced cylinder operation to the reduced cylinder operation, the same control as the control during the reduced cylinder operation is started, and the opening of the throttle valve 34a is changed to the open side, The opening of the throttle valve 34a is changed to the open side so that the intake air amount increases toward the intake air amount during the reduced cylinder operation.

  Further, when there is a request for switching from all-cylinder operation to reduced-cylinder operation in the specific operation region C, the combustion cycle (one cycle is 720 ° CA) is set in advance after this request is issued. Until the number of cycles elapses, the spark plug control unit 53, the injector control unit 54, and the valve stop mechanism control unit 55 are also controlled in the same manner as when there is a switching request in the other operation regions described in (i) (transient total (Cylinder control) is performed. That is, until the first number of cycles elapses, the control units 53 to 55 allow the intake and exhaust valves 8 and 9 of all the cylinders to be opened and closed and the combustion is performed in all the cylinders. Further, the spark plug control unit 53 calculates how much the actual intake air amount has increased with respect to the intake air amount during normal all-cylinder operation, and calculates the intake air amount from the basic ignition timing during normal all-cylinder operation. The timing retarded by the retard amount corresponding to the increased amount is determined as the final switching ignition timing.

  On the other hand, when there is a request for switching from all-cylinder operation to reduced-cylinder operation in the specific operation region C, when the first number of cycles elapses, intermediate reduction-cylinder control is started. A part of the cylinders that are in the inactive state during the cylinder operation are in the inactive state. In the present embodiment, the first cylinder 2A is deactivated.

  That is, when the first cycle number elapses, the valve stop mechanism control unit 55 turns on only the valve stop mechanism solenoid valve 42a of the first cylinder 2A and turns on only the intake and exhaust valves 8 and 9 of the first cylinder 2A. The injector control unit 54 stops the injection of only the injector 12 of the first cylinder 2A, and the spark plug control unit 53 stops the ignition of only the spark plug 13 of the first cylinder 2A.

  Then, the spark plug control unit 53 cancels the decrease in engine torque associated with the first cylinder 2A being deactivated and its output being stopped as intermediate reduction cylinder control, so that the engine torque becomes constant. Then, control for changing the ignition timing is started. That is, the spark plug control unit 53 is caused by a decrease in engine torque associated with the first cylinder 2A being brought into a resting state and an increase in engine torque associated with an increase in intake air amount from normal all-cylinder operation. The ignition timing is determined so as to cancel the change in engine torque from the normal all-cylinder operation (immediately before the request for switching from all-cylinder operation to reduced-cylinder operation). Immediately after the first cylinder 2A is deactivated, the engine torque is lower than the time when all the cylinders immediately before are in operation, so the ignition timing cancels the decrease in engine torque. , It is controlled to the advance side from the time immediately before this. Thereafter, the ignition timing is again changed to the retard side as the intake air amount increases.

  In the present embodiment, the spark plug control unit 53 includes the first cylinder 2A in a deactivated state, the operating cylinders are set to three cylinders, and the intake air amount sucked into each cylinder is the intake air amount during all-cylinder operation. A map of the ignition timing for the engine speed and the engine load (engine torque) in a state of being stored is stored, and the spark plug control unit 53 determines the ignition timing according to the engine speed and the engine load from this map. And the extracted ignition timing is corrected based on the detected value of the intake pressure sensor SN4 and the like to determine the basic ignition timing. Then, the spark plug controller calculates how much the actual intake air amount has increased with respect to the intake air amount during normal all-cylinder operation, and calculates the retard amount corresponding to the increase amount of the intake air amount. The timing that is retarded by the retard amount from the basic ignition timing is determined as the final ignition timing.

  The throttle valve control unit 52 performs the same control during the transient all-cylinder control and during the intermediate reduction cylinder control. That is, when there is a request for switching from all-cylinder operation to reduced-cylinder operation, the throttle valve control unit 52 subsequently performs control to continuously increase the intake air amount toward the intake air amount during the reduced-cylinder operation.

  When there is a request for switching from all-cylinder operation to reduced-cylinder operation in the specific operation region C, the state in which only the first cylinder 2A is stopped continues for a preset second number of cycles. Later, all of the deactivated cylinders, that is, the fourth cylinder 2D in addition to the first cylinder 2A are deactivated, and the reduced cylinder operation is started.

  That is, when the combustion cycle has elapsed for the second number of cycles since the first cylinder 2A has been deactivated, the valve stop mechanism control unit 55 also sets the valve stop mechanism solenoid valve 42b of the fourth cylinder 2D to the ON state. The intake and exhaust valves 8 and 9 of the fourth cylinder 2D in addition to the one cylinder 2A are closed and the injector control unit 54 stops the injection of the injector 12 of the fourth cylinder 2D in addition to the first cylinder 2A, and controls the spark plug. The unit 53 stops ignition of the spark plug 13 of the fourth cylinder 2D in addition to the first cylinder 2A.

  In the present embodiment, the first cycle number and the second cycle number are set to increase as the engine speed increases, and a predetermined cylinder is first set after a request for switching from all-cylinder operation to reduced-cylinder operation is issued. The time until the (first cylinder 2A) is deactivated and the time until the next predetermined cylinder (fourth cylinder 2D) is deactivated are substantially constant regardless of the engine speed. Is set to

(Iii) Flow of control at the time of switching from all-cylinder operation to reduced-cylinder operation The flow of control at the time of switching from the above-described all-cylinder operation to reduced-cylinder operation is shown in the flowchart of FIG.

  First, in step S1, the engine load, the engine speed, the water temperature, the accelerator opening, and the like specified by the detection values of the sensors are read. Next, in step S2, it is determined whether or not there has been a request from the all-cylinder operation to the reduced-cylinder operation. As described above, this determination is performed by the operation request determination unit 51. The operation request determination unit 51 determines whether the engine load and the engine speed are in the predetermined operation region C, whether the engine water temperature is equal to or higher than the predetermined temperature, or whether the accelerator is opened. It is determined whether or not there has been a request from the all-cylinder operation to the reduced-cylinder operation depending on whether or not the rate of change of the degree is equal to or greater than a predetermined value.

  If the determination in step S2 is NO and it is determined that there is no request from all-cylinder operation to reduced-cylinder operation (should not be shifted from all-cylinder operation to reduced-cylinder operation), the process proceeds to step S3. Maintain cylinder operation. On the other hand, if the determination in step S2 is YES and there is a request from the all cylinder operation to the reduced cylinder operation, the process proceeds to step S4.

  In step S4, the oil pump 41 increases the oil pressure of the oil passage between the oil pump 41 and the valve stop mechanism 25a, specifically, the oil passage between the oil pump 41 and the valve valve for stop valve solenoid. . This is because the intake / exhaust valves 8 and 9 of the deactivated cylinders (first and fourth cylinders 2A and 2D) are more reliably closed when the reduced cylinder operation is started. In this way, before starting the reduced cylinder operation, the oil pressure in the oil passage between the oil pump 41 and the valve stop mechanism solenoid valve 42 is increased, but the valve stop mechanism solenoid valve 42 is in the OFF state. At this time, the lock pin 252 of the valve stop mechanism 25a and the through hole 251a are maintained in a disengaged state, and the intake and exhaust valves 8 and 9 of the idle cylinders (first and fourth cylinders 2A and 2D) are maintained. Open / close drive.

  In step S5 following step S4, transient all-cylinder control is performed. That is, the opening degree of the throttle valve 34a is changed to the opening side compared with the normal all-cylinder operation. In the present embodiment, as described above, the throttle valve control unit 52 starts the control during the reduced cylinder operation, and opens the throttle valve 34a so that the intake amount per cylinder becomes the intake amount during the reduced cylinder operation. Change to open side. Further, the ignition timing is set to the retarded angle side compared with the normal all-cylinder operation. In the present embodiment, as described above, the spark plug controller 53 delays the ignition timing from the ignition timing during normal all-cylinder operation by an amount corresponding to the amount of increase in the intake air amount from the intake air amount during all-cylinder operation. The horned timing is determined as the final ignition timing.

  In step S6 following step S5, it is determined whether or not the operation region is a specific operation region C.

  When determination of step S6 is NO and it is not the specific driving | operation area | region C, it progresses to step S7. In step S7, it is determined whether the intake air amount has reached the intake air amount during the reduced-cylinder operation. If the determination in step S7 is yes, the process proceeds to step S8. On the other hand, if the determination in step S7 is no, the process returns to step S5. That is, when the operation region C is not in the specified range (NO in step S6), step S5, that is, transient all-cylinder control is performed until the intake amount reaches the intake amount during the reduced cylinder operation (determination in step S7 is YES). To be implemented.

  If the determination in step S6 is YES and the specific operation region C is present, the process proceeds to step S9. In step S9, it is determined whether or not the first cycle number has elapsed since the request for switching from all-cylinder operation to reduced-cylinder operation was issued. If the determination in step S9 is yes, the process proceeds to step S10. On the other hand, if the determination in step S9 is no, the process returns to step S5. That is, in the case of the specific operation region C (determination in step S6 is YES), step S5, that is, transient all-cylinder control is performed until the first number of cycles elapses (determination in step S9 is YES).

  In step S10, which proceeds to a case where the determinations in steps S6 and S9 are YES (when the combustion cycle is in the specific operation region C and the first cycle number has elapsed), the intermediate cylinder reduction control is performed. It is in a dormant state. That is, the drive of the injector 12 and the spark plug 13 of the first cylinder 2A is stopped, the combustion in the first cylinder 2A is stopped, and the valve valve stop mechanism solenoid valve 42a of the first cylinder 2A is turned on. The intake / exhaust valves 8, 9 of the first cylinder 2A are held closed. Then, in step S11, which proceeds after step S10, intermediate reduction control is also performed for the ignition timing of the operating cylinder, and the ignition timing of the operating cylinder is changed so that the engine torque becomes constant. In the present embodiment, as described above, the spark plug controller 53 retards the ignition timing from the basic ignition timing at the time of three cylinders by an amount corresponding to the amount of increase in the intake air amount with respect to the intake air amount during all cylinder operation. The timing is determined as the final ignition timing.

  After step S11, it is determined in step S12 whether or not the second number of combustion cycles has elapsed since the determination in step S9 was YES and the first cylinder 2A was deactivated. If this determination is YES, the process proceeds to step S8. On the other hand, if this determination is NO and the second number of cycles has not elapsed, the process proceeds to step S13, and control for increasing the intake air amount is continued as intermediate reduction cylinder control, and steps S10 and S11 are performed. To do. That is, the intake air amount is increased, the first cylinder 2A is maintained in a resting state, and the ignition timing is controlled to be constant torque.

  In step S8, reduced-cylinder operation is started. That is, the ignition and fuel injection of all the deactivated cylinders (first and fourth cylinders 2A, 2D) are stopped, and all the valve stop mechanism solenoid valves 42a, 42b are turned on to deactivate the deactivated cylinders (first, The intake and exhaust valves 8, 9 of the fourth cylinders 2A, 2D) are held closed. Further, the ignition control of the operating cylinders (second and third cylinders 2B and 2C) is switched to the control during normal reduced-cylinder operation.

(5) Operation, etc. (i) Switching under operating conditions other than specific operating conditions FIG. 8 shows the results when the control according to this embodiment is performed. As a comparative example, FIG. 9 shows the results when the reduced cylinder operation is started immediately when the above switching request is made without performing the control for increasing the intake air amount and the control for retarding the ignition timing. FIG. 10 shows the result when only the control for increasing the amount is performed. In these figures, the uppermost graph shows the change of the switching flag from all-cylinder operation to reduced-cylinder operation, and changes from 0 to 1 when a request for switching from all-cylinder operation to reduced-cylinder operation is issued. To do.

  As shown in FIG. 9, immediately after a request for switching from all-cylinder operation to reduced-cylinder operation at time t1, combustion of the idle cylinders (first and fourth cylinders 2A, 2D) is stopped and two operating cylinders are used. In this case, although the throttle valve 34a is changed to the open side with the start of the reduced cylinder operation, the intake amount (intake amount per cylinder, charging efficiency) does not immediately increase to the target value during the reduced cylinder operation. For this reason, the output from these operating cylinders is not ensured due to a shortage of intake air in the operating cylinders (second and third cylinders 2B, 2C), and the engine torque drops rapidly, resulting in a torque shock.

  Also, as shown in FIG. 10, after a request for switching from all-cylinder operation to reduced-cylinder operation at time t1, the combustion in the idle cylinders (first and fourth cylinders 2A and 2D) is not stopped immediately. First, when the throttle valve 34a is changed to the open side to increase the intake air amount (intake amount per cylinder, charging efficiency Ce) to the target value for the reduced cylinder operation, and then the reduced cylinder operation is started. Although the decrease in engine torque is avoided, the intake amount of these cylinders increases while combustion is being performed in all the cylinders. As a result, the output of each cylinder increases and the engine torque increases. Therefore, even in this case, when the reduced-cylinder operation is started at time t2, the engine torque suddenly decreases and a torque shock occurs.

  On the other hand, in the apparatus according to the present embodiment, the transient all-cylinder control is performed, and immediately after a request for switching from the all-cylinder operation to the reduced-cylinder operation at time t1, as shown in FIG. During the cylinder operation, the combustion of the deactivated cylinders (first and fourth cylinders 2A, 2D) is not stopped, and the throttle valve 34a is changed to the open side to reduce the intake amount (intake amount per cylinder, charging efficiency). In addition, the ignition timing is retarded in accordance with the amount of increase in the intake air amount. Therefore, it is possible to avoid an increase in output from each cylinder while increasing the intake air amount, and to avoid an increase or decrease in engine torque. In other words, the engine torque can be maintained substantially constant when switching from all-cylinder operation to reduced-cylinder operation, and generation of torque shock can be avoided during this switching.

(Ii) Switching under a specific operation condition (specific operation region C) FIG. 11 shows a result when the control according to the present embodiment is performed, and in the specific region C, from all-cylinder operation to reduced-cylinder operation. The result when it is determined that there has been a request for switching from all-cylinder operation to reduced-cylinder operation by shifting from the all-cylinder operation region A2 to the specific region C is shown. Further, as a comparative example, FIG. 12 shows a result when only the transitional all-cylinder control is performed without performing the intermediate reduction cylinder control when the switching request is made in a specific operation region C.

  As described above, in the specific operation region C, the normal ignition timing is set to a time that is relatively close to the retarded side (a time when there is a high possibility of misfire). Therefore, as shown in FIG. 12, in response to a request to switch from all-cylinder operation to reduced-cylinder operation at time t1, the throttle valve 34a is changed to the open side and the intake air amount (the intake air amount per cylinder, the charge amount) If the ignition timing is retarded while increasing (efficiency), the combustion stability falls below the reference value when the ignition timing is retarded from the predetermined timing, causing misfiring, etc., causing engine torque fluctuations Resulting in. If the ignition timing is fixed at a limit timing at which no misfire occurs as shown by the broken line in FIG. 12 in order to avoid this misfire, etc., the engine torque increases as the intake air amount increases and decreases at time t3. When the cylinder operation is started, a torque shock is also generated.

  On the other hand, as shown in FIG. 11, in the present embodiment, when there is a switching request in a specific operation region C, the period from when this switching request is made until the first cycle elapses (see FIG. 11). 11 between t1 and t2), while performing combustion in all cylinders (first to fourth cylinders 2A to 2D), the throttle valve 34a is changed to the open side and the intake amount (intake amount per cylinder, filling) (Efficiency) is increased toward the amount during reduced-cylinder operation, and control (transient all-cylinder control) is performed to retard the ignition timing according to the amount of increase in intake air, and thereafter (after time t2), intake air While continuing the control to increase the amount, only the first cylinder 2A is deactivated and combustion is performed in three cylinders (intermediate reduction cylinder control). Therefore, after time t2, an increase in engine torque can be suppressed by reducing the number of output cylinders, and it is necessary to retard the ignition timing excessively in order to suppress an increase in engine torque accompanying an increase in intake air amount. Disappears. Therefore, it is possible to avoid the misfire and torque fluctuation caused by excessive retardation of the ignition timing, or the increase in engine torque associated with fixing the ignition timing to a predetermined timing in order to avoid the misfire. Occurrence can be avoided. In particular, after the time t2, the ignition timing is controlled so that the engine torque before the time t2 is maintained (intermediate cylinder reduction control). Can be reliably avoided. Specifically, as shown in FIG. 11, when the first cylinder 2A is deactivated at time t2, the ignition timing is sufficiently advanced from the previous ignition timing, that is, the misfire limit. Can be advanced. Therefore, the ignition timing is retarded as the intake amount increases after time t2, but the timing is sufficiently advanced from the misfire limit, and the engine torque is kept constant from time t1 to t3. can do.

  As described above, according to the apparatus according to the present embodiment, it is possible to more reliably avoid the occurrence of torque shock when switching from all-cylinder operation to reduced-cylinder operation, and to improve drivability. it can.

(6) Modified Example Here, in the above embodiment, when there is a switch from the all-cylinder operation to the reduced-cylinder operation in the specific operation region C, that is, the transition from the all-cylinder operation region A1 to the specific operation region C. In connection with this, only the case where it has been determined that there has been a request for switching from all-cylinder operation to reduced-cylinder operation has been described. Tube control may be performed.

  However, if the intermediate reduction cylinder control is performed only under the operating conditions in which misfire is likely to occur, the intermediate reduction cylinder control is performed under conditions other than the operating conditions while avoiding misfires under the operating conditions. Occurrence of engine vibration or the like can be avoided to improve drivability.

  In other words, in the intermediate reduction cylinder control, the number of cylinders in which combustion is performed is set to a total number that can ensure stable engine behavior or a number different from the number at the time of reduction cylinder operation, and therefore the engine behavior may become unstable. There is. Specifically, in the above-described embodiment, engine vibration may be increased because combustion is performed only in three cylinders by performing the intermediate reduction control. For this reason, if the number of opportunities for performing the intermediate cylinder reduction control is reduced, it is possible to suppress an increase in engine vibration and noise.

  In the above-described embodiment, the case where the specific operation region C is set to a region where the torque reduction possibility rate is less than a predetermined value has been described. However, the setting criterion for the specific operation region C is not limited thereto. For example, the torque reduction possibility rate may be a region other than 0.5. In addition, as an index of combustion stability that replaces the above-mentioned combustion stability, the probability that misfire does not occur when burned multiple times under the same conditions is used, and the ignition timing at which this probability becomes a predetermined value is used as the misfire limit timing. As a result, a specific operation region C may be set. Further, a region where the ignition timing set in advance according to the engine speed and the engine load is close to a predetermined limit time may be set as a specific operation region.

  Further, if the ignition timing exceeds the preset limit timing and becomes retarded by performing the ignition timing retard control, it is not determined whether or not it is in a specific operation region set in advance. May be implemented.

  In the above embodiment, when the intermediate reduction control is performed, the period from when there is a request for switching from all-cylinder operation to reduced-cylinder operation until the start of the intermediate reduction control, that is, the switching request. The period until the predetermined cylinder is deactivated for the first time, and the period after the predetermined cylinder is deactivated for the first time until the other cylinder is deactivated (after the first cylinder 2A is deactivated) The case in which the period from when the fourth cylinder 2D is deactivated to when the reduced cylinder operation is started is described with the number of cycles set in advance, but the setting of these periods is not limited to this. For example, these periods may be defined by time. Further, the first or next cylinder may be deactivated when the ignition timing is retarded to a preset limit timing in accordance with the control for retarding the ignition timing. Further, the stop control of these cylinders may be performed when the intake air amount reaches a predetermined value.

  However, if each period is defined by the number of cycles as in the above embodiment, the control configuration can be simplified, and the period when the engine behavior becomes unstable due to the intermediate reduced cylinder operation is excessive. Thus, it is possible to more reliably avoid deterioration of drivability. In addition, when the above period is defined by whether or not the ignition timing and intake air amount have reached a predetermined value, the ignition timing and intake air amount must be determined from the predetermined value, resulting in a delay in control. There is a risk that misfires and the like cannot be sufficiently avoided. However, if each period is defined by the number of cycles, such control delay can be avoided, and more appropriate control and thus better drivability can be ensured.

  In the above embodiment, the case has been described where the number of cycles corresponding to these periods (the first cycle number and the second cycle number) is set higher as the engine speed is higher. However, these cycle numbers depend on the engine speed. It may be constant. However, if the number of cycles is increased as the engine speed is higher, the time corresponding to each of the above periods can be made substantially constant regardless of the operating conditions. Therefore, it is possible to appropriately secure each time while avoiding that the driver feels uncomfortable when the engine behavior becomes unstable due to the execution of the intermediate cylinder reduction control.

  In the above embodiment, when the intermediate cylinder reduction control is not performed, it is determined whether or not the transient all cylinder control is terminated and the cylinder reduction operation is started. The case where the determination is made depending on whether or not the determination is made has been described, but the specific content of this determination is not limited to this. For example, as in the case of the intermediate reduction cylinder control, the reduction cylinder operation is configured to start when a predetermined number of cycles or a predetermined time elapses after a request to switch from all cylinder operation to reduced cylinder operation. Also good.

  Moreover, although the said embodiment demonstrated the example which applied the control apparatus of this invention to the 4-cylinder gasoline engine, the form of the engine which can apply the control apparatus of this invention is not restricted to this. For example, a multi-cylinder engine other than four cylinders such as six cylinders or eight cylinders may be targeted. Then, when there are three or more cylinders that are deactivated during the reduced-cylinder operation, the number of cylinders that are deactivated when switching from the all-cylinder operation to the reduced-cylinder operation may be gradually increased. For example, in the case of a 6-cylinder engine and when two cylinders are put into a resting state during a reduced-cylinder operation, the number of cylinders to be put into a resting state may be gradually increased from 5 toward 2 as intermediate reduction-cylinder control. Good. Specifically, the number of cylinders to be deactivated may be changed from 5 → 4 → 3 → 2, 5 → 4 → 2, 5 → 3 → 2, and the like. Also, other types of internal combustion engines such as diesel engines, ethanol fuel engines, and LPG engines may be targeted.

DESCRIPTION OF SYMBOLS 1 Engine main body 2A-2D Cylinder 8 Intake valve 9 Exhaust valve 13 Spark plug (ignition means)
25a Valve stop mechanism 50 ECU (control means)

Claims (4)

A plurality of cylinders provided with an intake valve and an exhaust valve, ignition means provided in each cylinder for applying ignition energy to an air-fuel mixture in these cylinders, and an intake passage connected to each cylinder All-cylinder operation in which the air-fuel mixture is combusted in all the cylinders and the reduced-cylinder operation in which the engine operating state is predetermined. An apparatus for controlling an engine that is implemented when in a region and is switchable between a reduced-cylinder operation in which combustion in a specific cylinder among the plurality of cylinders is stopped and the specific cylinder is in a resting state Because
A valve stop mechanism for switching between a state in which the intake valve and the exhaust valve of the specific cylinder can be opened and closed and a state in which the valve is held;
Control means for controlling each part of the engine including the valve stop mechanism, the throttle valve, and the ignition means,
The control means includes
The amount of air sucked into each cylinder during at least a part of the switching period from when there is a request for switching from all-cylinder operation to reduced-cylinder operation in which the specific cylinder is deactivated until the reduced-cylinder operation is started. The valve so that the intake / exhaust valves of all the cylinders can be opened and closed in a state where the opening of the throttle valve is changed so as to be larger than the air amount during normal all-cylinder operation where the switching request is not issued. Implemented all-cylinder control that controls the stop mechanism and performs combustion in all cylinders.
When there is a request for switching, and the engine operating region changes to a predetermined specific operating region in which the combustion stability is equal to or less than a predetermined value in the reduced-cylinder operating region , the transient is performed during the switching period. After performing all cylinder control, the throttle valve opening is changed so that the amount of air sucked into each cylinder is larger than the amount of air during normal all cylinder operation. The valve stop mechanism is controlled so that the intake / exhaust valves of the cylinders that are at least less than the number of the specific cylinders can be opened and closed, and in the cylinders that are less than the total number of cylinders and greater than the number of the specific cylinders On the other hand, while performing intermediate reduction cylinder control that performs combustion only at
When the switching request is made and the engine operating range is changed to an operating range other than the specific operating range in the reduced-cylinder operating range, the intermediate all-cylinder control is not performed and the transient all-cylinder control is performed. Controlling the valve stop mechanism so that the intake / exhaust valve of the specific cylinder is closed after the execution of the combustion, and stopping combustion in the specific cylinder,
At the time of the transient all-cylinder control, the ignition timing of the ignition means is retarded so as to cancel the change in the engine torque caused by the increase in the amount of air taken into each cylinder,
Above the intermediate cylinder cut control when to change the ignition timing of said ignition means so as to cancel the change in the engine torque caused by the change of the number of cylinders to increase and combustion of the amount of air sucked into each cylinder is performed ,
An engine control apparatus characterized in that the number of cylinders in which combustion is performed is larger than the number of cylinders in which combustion is stopped during the intermediate reduction control. The engine control device according to claim 1,
The control means controls the valve stop mechanism so that the intake / exhaust valve of the cylinder in which the combustion is stopped is closed during the intermediate reduction control, and when the intermediate reduction control is performed, An engine control device characterized by stopping the intermediate cylinder reduction control and starting the cylinder reduction operation when the number of cycles reaches a predetermined number after the intermediate cylinder reduction control is started . The engine control device according to claim 2 ,
When the above intermediate reduction cylinder control is performed, the number of cycles from when there is a request to switch from all cylinder operation to reduced cylinder operation until the combustion in the predetermined cylinder is stopped for the first time, and within the predetermined cylinder The engine control device according to claim 1, wherein the number of cycles from when the combustion in the engine is stopped to when the combustion in the new cylinder is stopped next is preset. The engine control device according to claim 3,
The engine control device according to claim 1, wherein the number of cycles is set for each engine speed, and is set to be higher as the engine speed is higher.

Images