JP2016151232A - Engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a fuel consumption performance while restricting occurrence of torque shock when an operation is changed over from a full cylinder operation to a reduced cylinder operation.SOLUTION: An engine in which a homogeneous combustion is carried out at each of cylinders is further controlled in such a way that, upon request for changing-over in operation from a full cylinder operation to a reduced cylinder operation, an intake amount increasing control for increasing an amount of intake of each of the cylinders 2A to 2D by more than the intake amount of normal full cylinder operation where the request for changing-over is not applied is performed by intake amount changing means 34a, 34b, the reduced cylinder operation is started after finishing of the intake amount increasing control and at the same time the combustion in each of the cylinders 2A to 2D is changed over to a stratified charge combustion by at least injecting fuel during a compression stroke with fuel injection means 12 during execution of the intake amount increasing control.SELECTED DRAWING: Figure 7

Description

  The present invention relates to an apparatus for controlling an engine that can be switched between an all-cylinder operation in which combustion of an air-fuel mixture is performed in all cylinders and a reduced-cylinder operation in which combustion in a specific cylinder is stopped.

  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.

  During the reduced-cylinder operation, the number of operating cylinders, that is, the number of cylinders to be output decreases, so that 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 each air amount sucked into the operating cylinder, that is, each intake air amount.

  Here, there is a delay in the intake air amount. For this reason, if the control for increasing the intake air amount is started simultaneously with the start of the reduced cylinder operation, the intake air amount is insufficient at the start of the reduced cylinder operation, resulting in a decrease in engine output, that is, a torque shock.

  On the other hand, it is conceivable to increase the intake air amount of each cylinder in advance before the start of the reduced cylinder operation. However, if the intake air amount of each cylinder is increased before the start of the reduced cylinder operation, that is, in a state where combustion is being performed in all the cylinders, the engine output before the start of the reduced cylinder operation becomes excessive and the reduced cylinder operation starts. Sometimes torque shocks occur.

  On the other hand, in Patent Document 1, before the start of the reduced cylinder operation, the throttle valve provided in the intake passage is changed to the open side to increase the intake amount of each cylinder to the intake amount during the reduced cylinder operation. The ignition timing of each cylinder is controlled to be retarded from the optimal ignition timing (MBT: Minimum Advance for Best Torque), thereby increasing the engine output while increasing the intake amount of each cylinder before the start of the reduced cylinder operation. An apparatus configured to suppress the increase is disclosed.

JP-A-5-332172

  The device of Patent Document 1 has a problem in that fuel efficiency is poor because the ignition timing is retarded from MBT when switching from full cylinder operation to reduced cylinder operation. In addition, there is a possibility that misfire may occur if the ignition timing is significantly retarded, or that the ignition timing cannot be retarded by a necessary amount in order to avoid this misfire, so that an increase in engine output, that is, a torque shock cannot be avoided.

  The present invention has been made in view of the above circumstances, and is an engine control device that can improve fuel efficiency while suppressing the occurrence of torque shock when switching from all-cylinder operation to reduced-cylinder operation. The purpose is to provide.

  In order to solve the above problems, the present invention has a plurality of cylinders, all-cylinder operation in which combustion of the air-fuel mixture is performed in all the cylinders, and a specific cylinder among the plurality of cylinders. A device that controls an engine that can be switched between reduced-cylinder operation in which combustion is stopped and in which homogeneous combustion is performed in each cylinder. Ignition means for performing ignition, fuel injection means provided in each cylinder for injecting fuel into these cylinders, intake air amount changing means capable of changing the intake air amount that is the amount of air sucked into each cylinder, and the ignition And a control means for controlling each part of the engine including a fuel injection means and an intake air amount changing means. When there is a request for switching from all-cylinder operation to reduced-cylinder operation, the control means uses the intake air amount changing means. Change the intake air amount of each cylinder Intake amount increase control is performed to increase the intake amount at the time of reduced cylinder operation, which is larger than the intake amount at the time of normal all cylinder operation where no request is issued, and the reduced cylinder operation is started after the intake amount increase control is completed. In addition, during execution of the intake air amount increase control, fuel is injected by the fuel injection means at least during the compression stroke, and combustion in each cylinder is switched to stratified combustion (claim 1). .

  According to the present invention, at the time of switching from the all-cylinder operation to the reduced-cylinder operation, the reduced-cylinder operation is started after the intake air amount increase control for increasing the intake air amount of each cylinder to the intake air amount during the reduced-cylinder operation. Therefore, the intake amount of the operating cylinder can be secured at the start of the reduced cylinder operation, and the output of the operating cylinder, that is, the engine torque can be suppressed from decreasing.

  Moreover, in the present invention, during the execution of the intake air amount increase control, fuel is injected during the compression stroke, and combustion in each cylinder is stratified combustion. Therefore, it is possible to suppress an increase in engine output accompanying an increase in the intake air amount without changing the ignition timing to the retard side, and to improve fuel efficiency.

  Specifically, in the homogeneous combustion, when the intake air amount is increased as described above, the injection amount must be increased accordingly, and the ignition timing is controlled in order to suppress the increase in engine output accompanying these increases. It is necessary to retard the fuel consumption performance. On the other hand, in the present invention, as described above, stratified combustion is performed when the intake air amount increases. That is, the combustion mode is such that the air-fuel ratio is combusted while the air excess ratio of the air-fuel mixture is relatively high in the entire cylinder by reducing the air excess ratio of the air-fuel mixture around the ignition means. Therefore, it is not necessary to increase the injection amount and retard the ignition timing in accordance with the increase of the intake amount, and high fuel efficiency can be ensured.

  In the present invention, during the execution of the intake air amount increase control, the control means controls the engine torque generated as the intake air amount of each cylinder increases as long as the intake air amount of each cylinder is less than a preset reference amount. In order to cancel the change, the ignition timing of the ignition means is changed to a timing retarded from the ignition timing during normal all-cylinder operation, and homogeneous combustion is performed in each cylinder. It is preferable to switch the combustion in each cylinder to stratified combustion after the amount exceeds the specified amount (Claim 2).

  If it does in this way, the stable combustion can be ensured, improving a fuel-consumption performance at the time of switching from all cylinder operation to reduction cylinder operation.

  That is, when stratified combustion is performed with a small amount of intake air, the air-fuel mixture around the ignition means becomes excessively rich, and there is a possibility that appropriate combustion cannot be realized. On the other hand, in the said structure, since stratified combustion is implemented in the state in which the intake air amount was ensured more than the reference amount, fuel consumption performance can be improved, ensuring appropriate combustion.

  In this configuration, when the intake air amount of each cylinder becomes equal to or greater than the reference amount during execution of the intake air amount increase control, the control means advances the ignition timing of the ignition means from the ignition timing at the previous homogeneous combustion. Stratified combustion is carried out in each cylinder at the same time, and the amount of fuel injected into each cylinder by the combustion injection means is set to be the same as the engine torque immediately before switching to stratified combustion. The amount is preferably controlled (claim 3).

  In this way, when performing stratified combustion, the increase in engine torque can be suppressed by reducing the fuel amount while the ignition timing is advanced, so that the fuel efficiency can be improved more reliably.

  In the present invention, the excess air ratio of each cylinder is set to a value close to 1 when performing homogeneous combustion, and is set to a value greater than 1 when performing stratified combustion (Claim 4).

  As described above, according to the engine control apparatus of the present invention, it is possible to improve fuel efficiency while suppressing the occurrence of torque shock at the time of 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 control which concerns on one Embodiment 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 the comparative example of this invention.

(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 (fuel injection means) 12 (FIG. 1) 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 main 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. .

  As shown in FIG. 1, the cylinder head 4 includes an injector 12 that injects fuel (gasoline) toward the combustion chamber 10 of each cylinder 2 </ b> A to 2 </ b> D as described above, and fuel and air injected from the injector 12. And an ignition plug (ignition means) 13 for igniting the air-fuel mixture by spark discharge. 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 stopped without burning 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. A throttle valve 34 a that can open and close a passage in the intake pipe 33 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 flow rate of the intake air introduced into the engine main body 1 is changed by opening and closing the throttle valve 34a, and the throttle valve 34a and the valve actuator 34b can change the intake air amount that is the amount of air sucked into each cylinder. Function as.

  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 disposed in the cylinder head 4, respectively.

  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 operating 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 along 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 known hydraulic lash adjusters 24 and 25 (hereinafter abbreviated as “HLA”, which is an acronym of “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 are rotated by 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 swing fulcrums 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 kept closed. For this reason, at the time of 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 / exhaust valve is held closed.

  In the present embodiment, one valve stop mechanism solenoid valve 42 is provided for one cylinder, and a total of two valve stop mechanism solenoid valves 42 are provided. Then, one valve stop mechanism solenoid valve 42 supplies hydraulic pressure to the valve stop mechanism 25a provided in the intake valve 8 of the first cylinder 2A and the valve stop mechanism 25a provided in the exhaust valve 9 of the first cylinder 2A. The other valve stop mechanism solenoid valve 42 is connected to the valve stop mechanism 25a provided in the intake valve 8 of the fourth cylinder 2D and the valve stop mechanism 25a provided in the exhaust valve 9 of the fourth cylinder 2D. Change the hydraulic pressure to be supplied at the same time.

(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 in the intake passage 30 is provided with an intake air amount sensor SN3 that detects an intake air amount that is an air amount that passes through the surge tank 32 and is introduced into each cylinder 2A to 2D. An intake pressure sensor SN4 is provided for detecting the pressure.

  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 (engine water temperature) 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 (engine speed, cylinder information, intake air amount, intake pressure, accelerator opening) Degree, engine 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, the spark plug 13, the valve actuator 34b (throttle valve 34a), and the solenoid valve 42 for valve stop mechanism (valve stop mechanism 25a), and is based on the result of the above calculation and the like. Then, a control signal for driving is output to each of these devices. 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, as functional elements, an operation request determination unit 51, a throttle valve control unit 52, a spark plug control unit 53, an injector control unit 54, a valve stop mechanism control unit 55, and a reduced cylinder operation start determination unit 56. .

  The driving request determination unit 51 determines whether the engine is operated based on engine operating conditions (engine load, engine speed, engine water temperature, etc.) specified from the detected values of the accelerator opening sensor SN5, the crank angle sensor SN1, and the water temperature sensor SN6. Which one of the reduced-cylinder operation and all-cylinder operation is selected is determined. 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 It is determined that there is a request for reduced-cylinder operation (operating only the second and third cylinders 2B and 2C). 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.

  Here, in this apparatus, even if it is determined by the operation request determination unit 51 that there is a request from the all-cylinder operation to the reduced-cylinder operation, the reduced-cylinder operation is not started immediately, and the preparation control for the reduced-cylinder operation is performed. The reduced-cylinder operation is started after completion of this preparation control. The reduced-cylinder operation start determination unit 56 determines whether to end the preparation control and start the reduced-cylinder operation, and performs determination based on the intake air amount or the like. The specific control contents of the preparation control and the specific determination procedure of the reduced-cylinder operation start determination unit 56 will be described later.

  The throttle valve control unit 52 controls the opening of the throttle valve 34a, that is, the intake amount of each cylinder.

  The spark plug controller 53 controls the ignition timing of the spark plug 13 and the like.

  The injector control unit 54 controls the injector 12 and controls the injection amount and the injection timing, which are the amount of fuel injected from the injector 12 to each cylinder 2A to 2D (combustion chamber 10 of each cylinder).

  The valve stop mechanism control unit 55 controls the solenoid valve 42 for the valve stop mechanism to control the hydraulic pressure supplied to the valve stop mechanism 25a of the S-HLA 25, that is, the intake and exhaust valves 8, 9 of the first and fourth cylinders 2A, 2D. The opening / closing operation is 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 at the time other than when the preparation control is performed, that is, at the time of normal all-cylinder operation and reduced-cylinder operation 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 calculated based on the required cylinder filling efficiency and a surge tank reference volume efficiency that is preset according to the operating state of the engine (engine speed, etc.).

  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, during the reduced cylinder operation, the number of operating cylinders that generate engine output decreases. Therefore, in order to generate the same engine output as during all cylinder operation, the operating cylinders (second, third) The output per cylinder of the cylinders 2B and 2C) needs to be larger than the output per cylinder during all cylinder operation. Therefore, it is necessary to increase the output (generated torque) per cylinder during the reduced-cylinder operation, and accordingly, it is necessary to increase the intake amount of each cylinder. 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 intake air amount of each cylinder, the pressure in the intake passage 30 (pressure downstream of the throttle valve 34a) needs to be higher than that during all-cylinder operation. 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 the larger side (open side).

  The spark plug controller 53 switches the control of the spark plug 13 of the idle cylinders (first and fourth cylinders 2A, 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 controller 54 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 prohibits driving of the spark plug 13 of the idle cylinders (first and fourth cylinders 2A, 2D).

  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 extracted ignition timing is corrected based on the detected value of the intake pressure sensor SN4 and the like to determine the ignition timing. 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. The ignition timing stored in each map is set in the vicinity of the MBT (Minimum Advance for Best Torque) in each operating condition, that is, the time when the engine output becomes the highest.

  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 the reduced cylinder 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, In order to stop combustion in the idle cylinders (first and fourth cylinders 2A, 2D), fuel injection in the cylinders is prohibited.

  When the injector control unit 54 causes the injector 12 to perform fuel injection, the injector control unit 54 determines the injection amount and the injection timing according to the operating conditions and issues an instruction to the injector 12.

  In the present embodiment, during normal operation, homogeneous combustion in which the excess air ratio λ in the cylinder is 1, that is, homogeneous combustion under the stoichiometric air-fuel ratio is performed. Therefore, during normal operation, the injector control unit 54 determines the fuel amount at which the excess air ratio λ in the cylinder is approximately 1 as the injection amount based on the intake air amount of each cylinder. The intake air amount of each cylinder is estimated based on the detection value of the intake air amount sensor SN3 and the like. Further, the injector control unit 54 determines the injection timing to be a predetermined timing during the intake stroke during normal operation. As described above, in the present embodiment, during normal operation, a fuel amount such that the excess air ratio λ becomes approximately 1 is injected into the cylinder during the intake stroke, and homogeneous combustion is performed.

  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 a reduced-cylinder operation, the solenoid valve 42 for the valve stop mechanism is turned on to keep the intake and exhaust valves 8 and 9 of the deactivated cylinders (first and fourth cylinders 2A and 2D) closed.

(4-2) Preparation control (i) Control content As described above, in the reduced cylinder operation, the intake amount per cylinder is set so that the output per cylinder of the operating cylinder is larger than that in the all cylinder operation. Is increased. However, since there is a delay in the change in the intake air amount, the combustion of the deactivated cylinders (first and fourth cylinders 2A, 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, resulting in a torque shock. The preparation control is for avoiding the occurrence of this torque shock, and is started when the operation request determination unit 51 determines that there is a request for switching from all-cylinder operation to reduced-cylinder operation.

  As preparation control, the throttle valve control unit 52 performs control (intake amount increase control) for changing the opening of the throttle valve 34a so that the intake amount per cylinder becomes the intake amount at the time of the reduced cylinder operation. As described above, the intake amount per cylinder during the reduced-cylinder operation is set to be larger than the amount during normal all-cylinder operation where the preparation control is not performed. For this reason, the throttle valve control unit 52 sets the opening of the throttle valve 34a as a preparation control more than the opening at the time of normal all-cylinder operation, that is, the opening just before the request for switching from all-cylinder operation to reduced-cylinder operation. Control to open side.

  In the present embodiment, the throttle valve control unit 52 performs the same control as the control during the reduced-cylinder operation described in (4-1) as the preparation control, and when it is determined that the switching request has been made. Then, the opening degree of the throttle valve 34a is changed to the opening degree at the opening side at the time of the reduced cylinder operation and the opening side from the opening degree at the time of the all cylinder operation. That is, in this embodiment, when it is determined that there is a request for switching from the all-cylinder operation to the reduced-cylinder operation, the throttle valve control unit 52 immediately starts the control during the reduced-cylinder operation.

  As the preparation control, the valve stop mechanism control unit 55 performs control that enables the intake and exhaust valves of all the cylinders 2A to 2D to be opened and closed by turning off the solenoid valve 42 for the valve stop mechanism. That is, the valve stop mechanism control unit 55 does not immediately turn on the valve stop mechanism solenoid valve 42 even when the operation request determination unit 51 issues a request to switch from all-cylinder operation to reduced-cylinder operation. The intake and exhaust valves 8 and 9 of all the cylinders 2A to 2D can be opened and closed.

  In addition, the injector control unit 54 and the spark plug control unit 53 control the injector 12 and the spark plug 13 so that combustion is performed in all the cylinders 2A to 2D as the preparation control. That is, the injector control unit 54 and the spark plug control unit 53 immediately stop the cylinders (first and fourth cylinders) even if the operation request determination unit 51 issues a request for switching from all-cylinder operation to reduced-cylinder operation. The fuel injection and ignition are performed in all the cylinders 2A to 2D without stopping the fuel injection and ignition of the cylinders 2A and 2D).

  Thus, in this apparatus, even if the operation request determination unit 51 issues a request for switching from all-cylinder operation to reduced-cylinder operation, the intake / exhaust valves 8 and 9 of all the cylinders 2A to 2D are set by performing the preparation control. While being opened and closed, combustion is performed in all the cylinders 2A to 2D.

  Here, as described above, in the preparation control, the intake amount per cylinder is increased by the throttle valve control unit 52 to be larger than the intake amount during normal all-cylinder operation. For this reason, if the intake air amount is large in this way, if it is attempted to perform the same combustion in all cylinders 2A to 2D as in normal all-cylinder operation, that is, homogeneous combustion with an excess air ratio λ of about 1, the intake air amount Therefore, the amount of fuel must be increased accordingly, resulting in excessive engine output. Specifically, as the fuel amount increases, the engine output, that is, the engine torque, is higher than the engine output required by the driver or the like, which is the output during normal all-cylinder operation, that is, the engine output immediately before the start of the preparation control. turn into.

  Therefore, in the present apparatus, during the preparation control, the combustion in each cylinder is switched to stratified combustion. In the present embodiment, stratified combustion is performed while the excess air ratio λ of each cylinder is set to a value larger than 1 during the preparation control. That is, stratified combustion is performed by forming an air-fuel mixture that is combustible around the spark plug 13 and has a relatively low air excess rate while making the air excess rate of the entire air-fuel mixture in the cylinder relatively high. This is a combustion mode that allows proper combustion of the gas. Therefore, if stratified combustion is performed, it is not necessary to increase the fuel amount in accordance with the increase in intake air amount, and an increase in engine output can be avoided.

  However, stratified charge combustion is performed immediately after the start of the preparatory control and the intake air amount is relatively small, and the entire air-fuel mixture in the cylinder can be burned around the spark plug 13 while leaning (high excess air ratio). If an attempt is made to form an air-fuel mixture, the air-fuel mixture around the spark plug 13 becomes excessively rich (in a state where the excess air ratio is low), and there is a risk that misfire or the like may occur.

  Therefore, in this apparatus, after the start of the preparatory control, until the intake air amount becomes equal to or higher than a preset reference amount, stratified combustion is not performed and homogeneous combustion with an excess air ratio λ = 1 is performed. The injection amount is increased in accordance with the increase in the intake air amount, and the increase in engine output, that is, the engine torque accompanying the increase is suppressed by retarding the ignition timing. Specifically, the ignition timing is controlled to be retarded from the ignition timing during normal all-cylinder operation, that is, MBT during normal all-cylinder operation. The reference amount is an intake amount that enables stable stratified combustion, and is set in advance by experiments or the like.

  The above control is performed by the injector control unit 54 and the spark plug control unit 53.

  Specifically, the injector control unit 54 is a period until the intake air amount of each cylinder exceeds the reference amount after the preparation control is started (after it is determined that there is a request for switching from all cylinder operation to reduced cylinder operation). Performs the same control as during normal all-cylinder operation. That is, the injector control unit 54 determines the fuel amount at which the excess air ratio λ in the cylinder is approximately 1 as the injection amount based on the intake amount of each cylinder, and determines the injection timing as a predetermined timing during the intake stroke. . During this period, the spark plug control unit 53 calculates how much the intake air amount has increased with respect to the intake air amount during normal all-cylinder operation. The amount of retardation of the ignition timing corresponding to the amount of increase in the engine output (engine torque) corresponding to the amount of increase in the ignition timing is calculated, and the amount of retardation calculated from the ignition timing during normal all-cylinder operation (timing near MBT) The timing that is retarded by a certain amount is determined as the ignition timing. 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.

  On the other hand, when the intake air amount of each cylinder exceeds the reference amount, the injector control unit 54 sets the injection amount that can realize stratified combustion while maintaining the current engine output (engine output immediately before switching from homogeneous combustion to stratified combustion). calculate. That is, the injector control unit 54 has an injection amount such that the overall excess air ratio λ in each cylinder becomes λ> 1 based on the intake air amount detected by the intake air amount sensor SN3. An injection amount capable of obtaining the current engine output, that is, engine torque (engine output requested by the driver, that is, engine torque) when ignition is performed in the vicinity of MBT is calculated. Here, the injection amount for stratified combustion is set to an amount such that the excess air ratio λ in the entire cylinder is larger than 1.

  In addition, when the intake air amount of each cylinder becomes equal to or greater than the reference amount, the injector control unit 54 determines the injection timing to be a predetermined time set in the compression stroke. In the present embodiment, the injection timing is the latter stage of the compression stroke.

  When the intake air amount of each cylinder becomes equal to or larger than the reference amount, the spark plug control unit 53 returns the ignition timing that has been retarded from the ignition timing (timing near MBT) during normal all-cylinder operation to the advance side. . That is, the ignition timing is changed to a timing that is more advanced than the ignition timing immediately before switching from homogeneous combustion to stratified combustion. In the present embodiment, the spark plug controller 53 sets the timing in the vicinity of MBT during stratified combustion as the ignition timing.

(Ii) Preparation Control End and Reduced Cylinder Operation Start Timing The preparation control is performed until it is determined by the reduced cylinder operation start determination unit 56 that preparation control is ended and reduced cylinder operation is started.

  In the present embodiment, the reduced-cylinder operation start determination unit 56 determines that the preparation control is ended and the reduced-cylinder operation is started when the intake amount per cylinder increases to the intake amount during the reduced-cylinder operation.

(Iii) Flow of preparation control The flow of preparation control performed by the ECU 50 will be described with reference to the flowchart of FIG.

  First, in step S1, reading of the engine load, the engine speed, the engine water temperature (water temperature), the accelerator opening, the intake air amount, and the like specified by the detection values of the sensors is performed. Next, in step S2, it is determined whether or not there has been a request for switching from all-cylinder operation to 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 within a predetermined operation range, whether the engine water temperature is equal to or higher than a predetermined temperature, or whether the accelerator opening 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 change rate of the cylinder is greater than a predetermined value.

  If the determination in step S2 is NO and it is determined that there is no request for switching from all-cylinder operation to reduced-cylinder operation (should not shift from all-cylinder operation to reduced-cylinder operation), the process proceeds to step S3. Maintain all-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 for more reliably holding the intake and exhaust valves 8 and 9 of the deactivated cylinders (first and fourth cylinders 2A and 2D) at the start of the reduced cylinder operation. 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 Open / close drive.

  In step S5 following step S4, the intake air amount is increased toward the intake air amount during the reduced-cylinder operation. In the present embodiment, as described above, the throttle valve control unit 52 changes the opening of the throttle valve 34a to the opening at the time of reduced cylinder operation on the open side rather than at the time of normal full cylinder operation, and thereby the intake air amount Is increased toward the amount during reduced-cylinder operation.

  In step S6, which proceeds after step S5, the injection amount is increased and the ignition timing is retarded from the ignition timing during normal all-cylinder operation. In the present embodiment, as described above, the injector control unit 54 increases the injection amount so that the excess air ratio λ in the cylinder becomes approximately 1 as the intake amount increases. Further, the ignition plug control unit 53 delays the ignition timing from the ignition timing during normal all-cylinder operation by a timing corresponding to the amount of intake air increased from the intake amount during all-cylinder operation (at the start of preparation control). Horned.

  In step S7 following step S6, it is determined whether or not the intake amount per cylinder is equal to or greater than the reference amount. If the determination in step S7 is NO, the process returns to step S5, and steps S5 and S6 are repeated until the determination in step S7 becomes YES. On the other hand, if the determination in step S7 is YES and the intake air amount has increased above the reference amount, the process proceeds to step S8.

  In step S8, stratified combustion is performed while the intake air amount is increased. In the present embodiment, the throttle valve controller 52 maintains the opening of the throttle valve 34a at the opening during the reduced-cylinder operation, and the intake air amount continues to increase. Further, the injector control unit 54 sets the injection amount so that the excess air ratio λ in the entire cylinder is larger than 1, and the amount that realizes stratified combustion while maintaining the engine output (engine torque). In addition, the injection timing is changed to a predetermined timing during the compression stroke. Furthermore, the ignition timing is returned to the advance side with respect to the timing in step S6, and is set to a timing near the MBT during stratified combustion.

  In step S9 following step S8, it is determined whether or not the intake air amount is equal to or greater than the intake air amount during the reduced cylinder operation. If the determination in step S9 is NO, the process returns to step S8, and step S8 is repeated until the determination in step S9 becomes YES. On the other hand, if the determination in step S9 is YES and the intake air amount is greater than or equal to the intake air amount during the reduced cylinder operation, the process proceeds to step S10.

  In step S10, reduced-cylinder operation is started. That is, ignition and fuel injection of the deactivated cylinders (first and fourth cylinders 2A and 2D) are stopped, the solenoid valve 42 for the valve stop mechanism is turned ON, and the deactivated cylinders (first and fourth cylinders 2A and 2D) are turned on. The intake / exhaust valves 8 and 9 are held closed, and the ignition timing of the operating cylinders (second and third cylinders 2B and 2C) is the normal timing when the cylinder is reduced (timing near the MBT when the cylinder is reduced) Can be switched to. Further, the injection amount and the injection timing are the amount and timing at the time of normal reduced-cylinder operation, and the excess air ratio λ is close to 1, and the amount and timing at which homogeneous combustion is realized are switched.

(5) Operation, etc. FIG. 8 shows an example of changes in parameters when switching from full cylinder operation to reduced cylinder operation in the present embodiment. Further, in FIG. 9, as a comparative example, in the case where the stratified charge combustion is omitted in the preparation control and the ignition timing retardation control is performed after the switching request is made until the reduced cylinder operation is started. The change of each parameter at the time of the switching is shown. 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.

  In both the examples of FIGS. 8 and 9, when there is a request for switching 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 increases accordingly. Go. Moreover, immediately after time t1, in any case, the homogeneous combustion with the excess air ratio λ = 1 is performed, and the injection amount is increased in accordance with the increase of the intake air amount. Further, the ignition timing is retarded in accordance with the increase in the intake air amount and the injection amount. By retarding the ignition timing, immediately after time t1, the intake air amount and the injection amount are increased as described above, but the engine output (engine torque) does not increase and the engine output (engine Torque) is maintained.

  Here, in the example shown in FIG. 9, the switching to the stratified combustion is not performed as described above, and the homogeneous combustion is performed until time t2 when the intake air amount becomes the intake air amount during the reduced cylinder operation. Therefore, in this example, the injection amount continues to increase as the intake amount increases until time t2, and the ignition timing continues to be retarded accordingly.

  In the example of FIG. 9 as well, as in the example according to the present embodiment shown in FIG. 8, when the intake air amount becomes the amount at the time of reduced cylinder operation, the operating (combustion) cylinder is reduced to two, and the valve stop mechanism The solenoid valve is turned on, and the ignition timing is set to the timing for normal reduced cylinder operation, so that reduced cylinder operation is started.

  As shown in FIG. 9, in the case where homogeneous combustion is carried out even at the time of switching, in order to avoid an increase in engine output while increasing the intake air amount, the reduced-cylinder operation is performed after the switching request is made. During the period until the start of ignition, the injection amount must be increased and the ignition timing must continue to be retarded. For this reason, much of the combustion energy of the injected fuel is not converted into an effective engine output, and the fuel efficiency deteriorates.

  On the other hand, in the example according to the present embodiment shown in FIG. 8, the stratified charge combustion is switched at time t3 when the intake air amount becomes the reference amount, and the engine output is maintained (not increased or decreased). The amount is returned to the same level as the injection amount during normal all-cylinder operation, and the ignition timing is returned to the vicinity of MBT. Then, this stratified combustion is performed until time t2 when the intake air amount becomes the intake air amount during the reduced cylinder operation.

  Therefore, in the example according to this embodiment shown in FIG. 8, the injection amount indicated by the broken line in FIG. 8 is from the time t3 when the intake air amount becomes the reference amount to the time t2 when the reduced cylinder operation is started. The injection amount can be made smaller than the injection amount in the example of FIG. 9, and the fuel efficiency can be improved.

  As described above, in this embodiment, at the time of switching from all-cylinder operation to reduced-cylinder operation, an increase in injection amount can be avoided while suppressing an increase (fluctuation) in engine output (engine torque), Fuel efficiency can be improved.

  Moreover, in this embodiment, the fluctuation | variation of an engine output can be suppressed more reliably. Specifically, FIG. 9 shows the case where the ignition timing continues to be retarded while maintaining the engine output until time t2 when the reduced-cylinder operation is started, but when the ignition timing is excessively retarded. May cause misfire and change engine output. In addition, if the retard of the ignition timing is limited to avoid this misfire, an increase in engine output may not be avoided. In contrast, in the present embodiment, as described above, at least when the intake air amount becomes the reference amount (after time t3 in FIG. 8), the ignition timing is returned to the advance side. Therefore, it is possible to avoid fluctuations in engine output due to misfire or misfire avoidance as described above, and to more reliably suppress fluctuations in engine output when switching from all-cylinder operation to reduced-cylinder operation.

(6) Modified example Here, in the above-described embodiment, when there is a request for switching from the all-cylinder operation to the reduced-cylinder operation, first, the homogeneous combustion is performed, and the increase in the injection amount and the ignition timing in accordance with the increase in the intake air amount. Although the case where the lag is delayed and the intake air amount becomes equal to or higher than the reference amount and the stratified combustion is switched to has been described, the stratified combustion may be switched immediately after the switching request is made. In this way, fuel efficiency can be further improved.

  However, as described above, since the intake air amount is small, the mixture around the spark plug may become excessively rich and misfire may occur when stratified combustion is performed. Therefore, in such a case, the ignition timing is retarded while performing homogeneous combustion immediately after the request for switching from all-cylinder operation to reduced-cylinder operation and while the intake air amount is less than the reference amount. Is preferred.

  In the above embodiment, the case where the intake air amount is changed by opening / closing the throttle valve 34a, that is, the case where the intake air amount is increased by changing the throttle valve 34a to the open side in the preparation control has been described. The means for changing (increasing) is not limited to this. For example, a means capable of changing the valve timing or valve lift of the intake valve 8 may be used, and the intake air amount may be changed (increased) by changing the valve timing or valve lift.

  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 6 cylinders or 8 cylinders may be targeted, and another type of internal combustion engine such as a diesel engine, an ethanol fuel engine, or an LPG engine may be targeted.

DESCRIPTION OF SYMBOLS 1 Engine main body 2A-2D Cylinder 8 Intake valve 9 Exhaust valve 12 Injector (fuel injection means)
13 Spark plug (ignition means)
50 ECU (control means)

Claims (4)

Switchable between all-cylinder operation with multiple cylinders and combustion of air-fuel mixture in all cylinders and reduced-cylinder operation in which combustion in a specific cylinder among multiple cylinders is stopped And a device for controlling an engine in which homogeneous combustion is performed in each cylinder,
Ignition means provided in each cylinder for igniting an air-fuel mixture in these cylinders;
Fuel injection means provided in each cylinder for injecting fuel into these cylinders;
An intake air amount changing means capable of changing an intake air amount that is an air amount sucked into each cylinder;
Control means for controlling each part of the engine including the ignition means, fuel injection means and intake air amount changing means,
The control means includes
When there is a request to switch from all-cylinder operation to reduced-cylinder operation, the cylinder intake operation in which the intake air amount of each cylinder is greater than the intake air amount during normal all-cylinder operation when the request for switching is not issued by the intake air amount changing means. The intake air amount increase control for increasing the intake air amount at the time is performed, and after the intake air amount increase control is finished, the reduced cylinder operation is started,
A control apparatus for an engine, characterized in that, during execution of the intake air amount increase control, fuel is injected at least during the compression stroke by the fuel injection means to switch the combustion in each cylinder to stratified combustion. The engine control device according to claim 1,
The control means includes
While the intake air amount increase control is being performed, while the intake air amount of each cylinder is less than a preset reference amount, the ignition means is controlled so as to cancel the change in engine torque caused by the increase of the intake air amount of each cylinder. Homogeneous combustion is performed in each cylinder while changing the ignition timing to a timing that is retarded from the ignition timing during normal all-cylinder operation, and after the intake amount of each cylinder exceeds the above reference amount, The engine control device is characterized in that combustion in the engine is switched to stratified combustion. The engine control device according to claim 2,
When the intake air amount of each cylinder becomes equal to or greater than the reference amount during execution of the intake air amount increase control, the control means sets the ignition timing of the ignition means to a timing that is more advanced than the ignition timing at the previous homogeneous combustion. While stratified combustion is performed in each cylinder, the amount of fuel injected into each cylinder by the combustion injection means is controlled so that the engine torque is the same as the engine torque immediately before switching to stratified combustion. An engine control device. The engine control device according to any one of claims 1 to 3,
The engine control device is characterized in that the control means controls the excess air ratio of each cylinder to a value close to 1 when the homogeneous combustion is performed and to a value larger than 1 when the stratified combustion is performed.

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