JP6156224B2 - Engine control device - Google Patents

Description

  The present invention relates to an engine control device that includes an intake valve and an exhaust valve and has a plurality of cylinders in which combustion of an air-fuel mixture is performed.

  Conventionally, in an engine having a plurality of cylinders for the purpose of improving fuel economy performance, the opening / closing operation of intake valves and exhaust valves of some cylinders is restricted and combustion of the air-fuel mixture in the cylinders is stopped. A cylinder reduction operation is performed in which the cylinder is put into a resting state and the engine is driven only by the remaining cylinders.

  Here, when such a reduced-cylinder operation is performed, rotational fluctuation and engine vibration increase due to a difference between the in-cylinder pressure of the cylinder in the inactive state and the in-cylinder pressure of the operating cylinder. There is a problem that comfort is impaired. Specifically, during the reduced-cylinder operation, the gas in the cylinder in the inactive state leaks to the crankcase side through the gap between the cylinder and the piston as the piston reciprocates, and is in the inactive state. The in-cylinder pressure of the cylinder is reduced and a large difference is generated between the in-cylinder pressure of the cylinder in operation, thereby increasing rotational fluctuation and engine vibration.

  To solve this problem, for example, in Patent Document 1, an auxiliary intake valve is provided in addition to the normal intake valve in a cylinder that is in a deactivated state, and the normal intake valve is closed during reduced-cylinder operation. An apparatus for opening the auxiliary valve during the compression process is disclosed. According to this device, since the intake air is introduced into the cylinder that is in the inactive state even during the reduced-cylinder operation by opening the auxiliary valve, the decrease in the in-cylinder pressure of the inactive state is suppressed, and the rotational fluctuation and engine Vibration can be reduced.

JP 58-187508 A

  In the apparatus of Patent Document 1, an auxiliary valve must be added in addition to a normal intake valve, which complicates the apparatus and increases the cost. In addition, since this apparatus opens the auxiliary valve for each compression process during the reduced cylinder operation, the effect of improving the fuel efficiency can be sufficiently obtained by performing the reduced cylinder operation due to the generation of mechanical resistance accompanying the auxiliary valve drive. I can't.

  The present invention has been made in view of the above points, and is an engine control device capable of ensuring high comfort while effectively obtaining the effect of improving fuel efficiency by performing reduced-cylinder operation with a simple device. The purpose is to provide.

In order to solve the above-described problems, the present invention provides an engine control device that includes an intake valve and an exhaust valve and has a plurality of cylinders in which combustion of an air-fuel mixture is performed. A valve stop mechanism for restricting the opening and closing operations of the intake valve and exhaust valve of a specific cylinder to keep the valve closed, and a control means capable of controlling each part of the engine including the valve stop mechanism, the control means Is a reduced cylinder that restricts the valve stop mechanism to open and close the intake and exhaust valves of the specific cylinder and stops the fuel supply to the specific cylinder when the engine is in a specific operating condition. The control is performed to perform the reduced-cylinder operation in which the specific cylinder is in a resting state, and during the reduced-cylinder operation, the valve stop mechanism performs the opening / closing operation of the intake valve of the specific cylinder for each specific period. Lift the regulation To open and close the intake valve and the air-fuel mixture to maintain the regulation of the opening and closing operation of the exhaust valve of the specific cylinder, and, in the cylinder cut during operation, for each predetermined period, which present in the specific cylinder The engine control apparatus is characterized in that the air-fuel mixture is combusted in the specific cylinder at the most retarded timing among the timings at which the entire amount can be combusted .

According to this apparatus, since the normal intake valve is opened during the reduced-cylinder operation and the intake air is introduced into the cylinder (specific cylinder) that is in the inactive state, an auxiliary valve is separately provided as in Patent Document 1 above. Rotational fluctuation caused by the pressure difference between the cylinder pressure of the deactivated cylinder and the cylinder pressure of the operating cylinder while suppressing the decrease of the cylinder pressure of the cylinder in the inactive state while suppressing the cost with a simple configuration as compared with the case Further, the vibration of the engine can be suppressed to a small level, and high comfort can be obtained. In addition, in this device, the intake valve is opened every specific period during the reduced-cylinder operation. That is, the intake valve is opened intermittently after a predetermined period. Therefore, the mechanical resistance associated with driving the intake valve can be kept small, and the effect of improving the fuel consumption performance by performing the reduced-cylinder operation can be effectively obtained.
In addition, during the reduced-cylinder operation, at the most retarded timing among the timings at which the entire amount of the air-fuel mixture existing in the specific cylinder can be combusted for each predetermined period, Since the air-fuel mixture is burned, the in-cylinder pressure of the cylinder in the inactive state can be increased by the combustion of the air-fuel mixture, and the decrease in the in-cylinder pressure of the cylinder in the inactive state can be suppressed for a longer period of time. . Therefore, engine rotation fluctuations and engine vibrations can be suppressed more reliably.

  In the present invention, the specific period is preferably set longer as the engine speed is higher.

  In this way, it is possible to more reliably suppress the deterioration of fuel consumption performance associated with driving the intake valve while ensuring high comfort.

  Specifically, rotational fluctuations and engine vibrations are more difficult to experience as the period is shorter, that is, as the engine speed is higher. Therefore, when the engine speed is high, comfort can be maintained even if the difference between the in-cylinder pressure of the cylinder in the inactive state and the in-cylinder pressure of the operating cylinder is relatively large. Therefore, if the specific period is made longer as the engine speed is higher in this way, the opportunity for opening the intake valve can be reduced and the deterioration of mechanical resistance and fuel efficiency can be reduced while maintaining comfort. it can.

  In the present invention, it is preferable that the control means starts the cylinder reduction control at a timing at which the cylinder enters a resting state in a state where intake air before combustion is introduced into the specific cylinder. ).

  In this way, the cylinder reduction control is started in a state in which intake air is introduced to the cylinder to be deactivated, that is, in a state in which the cylinder pressure of the cylinder to be deactivated is secured high. The in-cylinder pressure of the engine can be maintained high, and the rotational fluctuation and engine vibration caused by the decrease in the in-cylinder pressure can be suppressed to a small level.

  Further, as a different form from the above configuration, the control means starts the cylinder reduction control at a timing when the cylinder is in a resting state in a state where the burned gas remains without being discharged from the specific cylinder. (Claim 4).

  Even in this case, since the cylinder reduction operation is started in a state where the cylinder pressure of the cylinder that is in the inactive state due to the combustion of the air-fuel mixture is increased, the decrease in the in-cylinder pressure of the cylinder in the inactive state is suppressed to be small, Rotational fluctuations and engine vibration caused by the decrease in the in-cylinder pressure can be reduced.

Specifically, when the combustion pressure is too high, the difference between this combustion pressure, that is, the cylinder pressure and the pressure on the crankcase side increases, so that a relatively large amount of gas leaks from the cylinder to the crankcase side immediately after combustion. As a result, the in-cylinder pressure of the cylinder in the resting state thereafter cannot be kept high. On the other hand, if the combustion timing is set to the above timing, the in-cylinder pressure can be increased by the combustion of the air-fuel mixture, and the leakage of gas in the cylinder can be suppressed by avoiding an excessive increase in the combustion pressure. It is possible to suppress a decrease in the cylinder pressure of the idle cylinder for a longer period of time.
The present invention also includes the following configurations.
An engine control device having an intake valve and an exhaust valve and having a plurality of cylinders in which a mixture of air and fuel is burned, and opening and closing an intake valve and an exhaust valve of a specific cylinder among the plurality of cylinders A valve stop mechanism that regulates the operation and holds the valve in a closed state; and a control unit that can control each part of the engine including the valve stop mechanism. The control unit is provided when the engine is in a specific operating condition. The valve stop mechanism restricts the opening / closing operation of the intake valve and the exhaust valve of the specific cylinder, and performs the cylinder reduction control for stopping the fuel supply to the specific cylinder, so that the specific cylinder is in a dormant state. In the reduced-cylinder operation, the restriction of the opening and closing operation of the intake valve of the specific cylinder by the valve stop mechanism is canceled and the intake valve is opened and closed during the reduced-cylinder operation . And the above decrease During operation, for each predetermined period, the timing of the most retarded side of the timing capable of total amount combust a mixture present in the above-mentioned specific cylinder, to combust a mixture in the specific cylinder The specific period is a period until it is determined that the in-cylinder pressure of the specific cylinder is less than a reference pressure set in advance in order to suppress the rotational fluctuation and vibration of the engine during the reduced cylinder operation. Engine control device.
An engine control device having an intake valve and an exhaust valve and having a plurality of cylinders in which a mixture of air and fuel is burned, and opening and closing an intake valve and an exhaust valve of a specific cylinder among the plurality of cylinders A valve stop mechanism that regulates the operation and holds the valve in a closed state; and a control unit that can control each part of the engine including the valve stop mechanism. The control unit is provided when the engine is in a specific operating condition. The valve stop mechanism restricts the opening / closing operation of the intake valve and the exhaust valve of the specific cylinder, and performs the cylinder reduction control for stopping the fuel supply to the specific cylinder, so that the specific cylinder is in a dormant state. In the reduced-cylinder operation, the restriction of the opening and closing operation of the intake valve of the specific cylinder by the valve stop mechanism is canceled and the intake valve is opened and closed during the reduced-cylinder operation . And the above decrease During operation, for each predetermined period, the timing of the most retarded side of the timing capable of total amount combust a mixture present in the above-mentioned specific cylinder, to combust a mixture in the specific cylinder In the specific period, the differential pressure between the in-cylinder pressure of the specific cylinder and the in-cylinder pressure of the operating cylinder that continues combustion in the reduced-cylinder operation suppresses rotational fluctuation and vibration of the engine during the reduced-cylinder operation. An engine control device that is a period until a predetermined value is provided.
In the above-described configuration, the control means is an engine control device that maintains the restriction of the opening / closing operation of the exhaust valve of the specific cylinder during the specific period.

  As described above, according to the present invention, it is possible to secure high comfort while effectively obtaining the effect of improving the fuel consumption performance by performing the reduced-cylinder operation with a simple device.

It is a figure showing one embodiment of an engine to which an engine control device of the present invention is applied. It is a schematic sectional drawing of the engine shown in FIG. (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 control system of the engine shown in FIG. It is the flowchart which showed the control procedure at the time of reduced cylinder operation. (A) It is the figure which showed the restriction | limiting timing of the opening / closing operation | movement of the intake / exhaust valve of a dormant cylinder. (B) It is the figure which showed the restriction | limiting timing of the opening / closing operation | movement of the intake / exhaust valve of a dormant cylinder. It is the figure which showed the relationship between an engine speed and specific time. It is the figure which showed the effect of the engine control apparatus which concerns on this invention. It is the flowchart which showed the control procedure at the time of the reduced cylinder driving | running in the engine control apparatus which concerns on other embodiment. It is the figure which showed the relationship between an engine speed and a reference pressure in embodiment shown in FIG.

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

  As shown in FIG. 2, the engine body 1 includes a cylinder block 3 in which the four cylinders 2 </ b> A to 2 </ b> D 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 (fuel mainly composed of gasoline) injected from an injector 12 (see 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.

  The cylinder head 4 is provided with an injector 12 for injecting fuel (gasoline) toward the combustion chamber 10 of each of the cylinders 2A to 2D, and an ignition energy by spark discharge for the mixture of fuel and air injected from the injector 12. An ignition plug 13 (see FIG. 1) for supplying and burning the air-fuel mixture 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, that is, the combustion 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 Fuel is injected from the injector 12 in the order of 2C → the fourth cylinder 2D → the second cylinder 2B, and the mixture is ignited by the spark plug 13, and the mixture is combusted in this order.

  The engine of this 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 combustion order (ignition order) as described above is that during 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, fuel injection by the injector 12 and ignition of the spark plug 13 in two cylinders (specific cylinders, the first cylinder 2A and the fourth cylinder 2D in the present embodiment) whose combustion order (ignition order) is not continuous. The operation is prohibited and combustion is performed by skipping one. Hereinafter, a cylinder in which the ignition operation is prohibited during the reduced cylinder operation may be referred to as a pause cylinder.

  The cylinder head 4 is generated in the intake port 6 for introducing the air (intake) supplied from the intake passage 30 into the combustion chamber 10 of each cylinder 2A to 2D and the combustion chamber 10 of each cylinder 2A to 2D. An exhaust port 7 for leading exhaust gas to the exhaust passage 35, an intake valve 8 for opening and closing the opening of the intake port 6 on the combustion chamber 10 side in order to control the introduction of intake air through the intake port 6, and the exhaust port 7 And an exhaust valve 9 for opening and closing an opening of the exhaust port 7 on the combustion chamber 10 side in order to control gas discharge from the exhaust port 7. 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.

  The intake passage 30 is commonly connected to four independent intake passages 31 communicating with the intake ports 6 of the cylinders 2A to 2D and upstream ends (ends on the upstream side in the intake air flow direction) of the individual intake passages 31. And a single intake pipe 33 extending upstream from the surge tank 32. An openable / closable throttle valve 34 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 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. 2 and 3A to 3C. 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. When pressed, the swing arms 20 and 21 swing and displace with the pivot portion 22 supporting one end thereof as a fulcrum. Along with this, 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. . The opened intake / exhaust valves 8 and 9 are returned to the closed position again by the urging force of the return springs 16 and 17 as the pressing force by the cam portions 18a and 19a is removed.

  The pivot portion 22 is supported by known hydraulic lash adjusters 24 and 25 that automatically adjust the valve clearance to zero (hereinafter abbreviated as “HLA” in the acronym of “Hydraulic Lash Adjuster”). 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 to allow or restrict the opening / closing operation of the intake / exhaust valves 8 and 9 depending on whether the engine is in a reduced cylinder operation or an all cylinder operation. Yes. That is, the HLA 25 allows the intake / exhaust valves 8 and 9 of the first and fourth cylinders 2A and 2D, which are idle cylinders when the cylinder is operated, to be opened and closed, while the idle cylinders are operated when the engine is reduced. The intake and exhaust valves 8 and 9 of the certain first and fourth cylinders 2A and 2D are restricted from opening and closing, and the intake and exhaust valves 8 and 9 are held in the closed state. The HLA 25 has a valve stop mechanism 25a shown in FIGS. 3A to 3C as a mechanism for restricting the opening / closing operation of the intake and exhaust valves 8 and 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 the opening / closing operation of the intake and exhaust valves 8 and 9 is always allowed. Below, in order to distinguish these HLA24 and 25, the HLA25 provided with the valve stop mechanism 25a is especially called S-HLA25 (Abbreviation of Switchable-Hydraulic LashAdjuster).

  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. Each lock pin 252 is driven by hydraulic pressure, and when a predetermined hydraulic pressure is supplied, the lock pin 252 is inserted into the through hole 251a, and the pivot portion 22 is locked.

  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 and as described above, the top portion of the pivot portion 22 becomes the swing fulcrum of the swing arms 20 and 21, and the cam portions 18 a and 19 a are rotated by the rotation of the cam shafts 18 and 19. When the cam followers 20a, 21a are 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. For this reason, during all-cylinder operation in which all four cylinders 2A to 2D are operated, the valve stop mechanism 25a opens and closes the intake and exhaust valves 8 and 9 of the first and fourth cylinders 2A and 2D with the pivot portion 22 locked. Ensure that operation is allowed.

  On the other hand, when the pair of lock pins 252 are pressed radially inward by the hydraulic pressure, the pair of lock pins 252 approach each other against the tensile force of the lock spring 253 as shown in FIG. It moves to the direction (diameter direction inner side of the outer cylinder 251). As a result, the engagement 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 that is movable in the axial direction.

  In this unlocked state, the pivot portion 22 is pressed downward against the urging force of the lost motion spring 254, thereby realizing a 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, and the intake / exhaust valves 8, 9 are not displaced. 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 valve stop mechanism 25a supplies the hydraulic pressure to the lock pin 252 to bring the pivot portion 22 into the unlocked state, whereby the first, The intake / exhaust valves 8 and 9 of the fourth cylinders 2A and 2D are restricted from opening and closing, and the intake and exhaust valves 8 and 9 are held in the closed state.

(3) Control system Next, an engine control system will be described. Each part of the engine of this 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 and a rotation speed of the crankshaft 15. The crank angle sensor SN1 outputs a pulse signal according to the rotation of a crank plate (not shown) that rotates integrally with the crankshaft 15. Based on this pulse signal, the rotation angle (crank angle) of the crankshaft 15 is output. ) And the rotation speed are specified. Hereinafter, the rotational speed of the crankshaft 15 is referred to as “engine speed”.

  The cylinder head 4 is provided with a cam angle sensor SN3. The cam angle sensor SN3 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 pressure sensor SN4 that detects the pressure of intake air introduced into the cylinders 2A to 2D of the engine body 1.

  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.

  The ECU (control means) 50 is electrically connected to these sensors SN1 to SN5, and based on signals input from the respective sensors, the above-described various information (crank angle, engine rotation speed, vibration intensity, Cylinder discrimination information, accelerator opening, etc.).

  Moreover, ECU50 controls each part of an engine, performing various determination, a calculation, etc. based on the input signal from each said sensor SN1-SN5. That is, the ECU 50 is electrically connected to the injector 12, the spark plug 13, the throttle valve 34, and the valve stop mechanism 25a, and outputs drive control signals to these devices based on the results of the above calculations and the like. To do. In the present embodiment, there are a total of four sets of injectors 12 and spark plugs 13 at a rate of one set per cylinder, but in FIG. 4, each of the injectors 12 and the spark plugs 13 is represented by one block. . Further, the valve stop mechanism 25a is connected to each intake-side and exhaust-side S-HLA 25 provided for the first cylinder 2A and each intake-side and exhaust-side S-HLA 25 provided for the fourth cylinder 2D. There is one each, and there are a total of four valve stop mechanisms 25a, which are represented by one block in FIG.

  More specific functions of the ECU 50 will be described. The ECU 50 controls the reduction of cylinders to realize the reduced cylinder operation (the valve stop mechanism 25a regulates the opening and closing operations of the intake valves and the exhaust valves of the idle cylinders 2A and 2D, and the air-fuel mixture in the idle cylinders 2A and 2D. An operation request determination unit 51, a valve control unit 52, and a combustion control unit 53 are provided as specific functional elements related to control for stopping combustion.

  The operation request determination unit 51 determines whether the engine has reduced cylinder operation or all cylinder operation based on the engine operating conditions (load, rotational speed, etc.) specified from the detected values of the accelerator opening sensor SN5 and the crank angle sensor SN1. It is determined whether to realize. For example, the operation request determination unit 51 deactivates the deactivated cylinders (first and fourth cylinders) 2A and 2D when the engine rotation speed and load are in a specific operation condition that is relatively low (second and third cylinders). It is determined that there is a request for reduced-cylinder operation (operating only the cylinders 2B and 2C). Conversely, when the remaining operating conditions except for the specific operating conditions are present, it is determined that there is a request for all-cylinder operation for operating all of the first to fourth cylinders 2A to 2D.

  The valve control unit 52 switches the operating state (whether the opening / closing operation is permitted or restricted) of the intake / exhaust valves 8 and 9 of the idle cylinders (first and fourth cylinders) 2A and 2D. Specifically, during the reduced cylinder operation, the valve control unit 52 supplies the hydraulic pressure to the valve stop mechanism 25a so that the pivot part 22 of the valve stop mechanism 25a is in the unlocked state (see FIG. 3C). Thus, the opening and closing operations of the intake and exhaust valves 8 and 9 of the idle cylinders (first and fourth cylinders) 2A and 2D are restricted, and the intake and exhaust valves 8 and 9 are maintained in the closed state. On the other hand, during the all-cylinder operation, the valve control unit 52 controls the hydraulic pressure supplied to the valve stop mechanism 25a so that the pivot unit 22 is in the locked state (see FIG. 3A), thereby The fourth cylinder) 2A, 2D intake and exhaust valves 8, 9 are allowed to open and close.

  Further, in the present embodiment, as will be described later, during the reduced-cylinder operation, the intake valves 8 of the idle cylinders (first and fourth cylinders) 2A and 2D are configured to be opened at specific intervals. The controller 52 supplies the hydraulic pressure to the valve stop mechanism 25a so that the opening / closing operation of the intake valves 8 of the idle cylinders (first and fourth cylinders) 2A and 2D is allowed for each specific period during the reduced cylinder operation. To control.

  The combustion control unit 53 switches the control of the injectors 12 and the spark plugs 13 of the idle cylinders (first and fourth cylinders) 2A and 2D according to the reduced cylinder operation or the all cylinder operation. That is, during all-cylinder operation, the combustion controller 53 drives the injectors 12 and spark plugs 13 of all the cylinders 2A to 2D to execute fuel injection and ignition, and burns the air-fuel mixture in all the cylinders 2A to 2D. Let On the other hand, during the reduced-cylinder operation, the combustion control unit 53 drives the injector 12 and the spark plug 13 of the cylinder to stop the combustion of the air-fuel mixture in the idle cylinders (first and fourth cylinders) 2A and 2D. To stop.

(4) Details of control during reduced-cylinder operation Details of control during reduced-cylinder operation performed by the ECU 50 will be described using the flowchart of FIG.

  First, in step S1, the ECU 50 determines whether or not there is a reduced cylinder operation request. This determination is performed by the operation request determination unit 51 as described above, and the operation request determination unit 51 determines that there has been a reduced-cylinder operation request when the operation condition becomes a specific operation condition.

  If the determination in step S1 is NO, step S1 is repeated.

  On the other hand, if the determination in step S1 is YES, that is, if it is determined by the operation request determination unit 51 that there has been a reduction cylinder operation request, the ECU 50, specifically the valve control unit 52, determines that the idle cylinder (first, first 4 cylinders) It is determined whether the current operation timing of each of 2A and 2D is the timing after the closing of each intake valve 8 and before the start of combustion (fuel injection by the injector 12 and ignition by the spark plug 13). That is, the valve control unit 52 determines whether or not the deactivated cylinders (first and fourth cylinders) 2A and 2D are in a state after the intake air before combustion is introduced inside thereof.

  If this determination is YES, the ECU 50 starts the reduced cylinder control (step S3). That is, in step S3, the valve controller 52 supplies the hydraulic pressure to the valve stop mechanism 25a so that the pivot portion 22 is in the unlocked state (see FIG. 3C). (Fourth cylinder) The intake / exhaust valves 8 and 9 of 2A and 2D are kept closed. Further, the combustion control unit 53 stops driving the injectors 12 and the spark plugs 13 of the idle cylinders (first and fourth cylinders) 2A and 2D.

  On the other hand, when the determination in step S2 is NO, the process returns to step S1. That is, the ECU 50 waits for the determinations in step S1 and step S2 to be YES, and starts the cylinder reduction control.

  FIGS. 6A and 6B are diagrams showing the restriction timing of the opening / closing operation of the intake and exhaust valves 8 and 9 of the idle cylinder. 6A and 6B show opening / closing timings of the intake and exhaust valves 8 and 9 and driving timings of the injector 12 and the spark plug 13 with the horizontal axis as the crank angle. 6 (a) and 6 (b), the lift curve of the intake valve 8 is expressed as “IN”, and the lift curve of the exhaust valve 9 is expressed as “EX”.

  In FIG. 6A, the timing ts at which it is determined by the operation request determination unit 51 that there has been a reduction cylinder operation request starts combustion after the intake valve 8 is closed (fuel injection by the injector 12 and ignition by the ignition plug 13). This is the previous case. In this case, as soon as it is determined that the reduced cylinder operation request has been made, the drive of the injector 12 and the spark plug 13 is stopped and the opening / closing operation of the intake / exhaust valves 8 and 9 of the idle cylinder is restricted. Immediately thereafter, the combustion and the opening of the intake and exhaust valves 8, 9 are stopped.

  On the other hand, in FIG. 6B, the timing ts at which it is determined by the operation request determination unit 51 that there has been a reduction cylinder operation request is the closing of the intake valve 8 after the start of combustion (fuel injection by the injector 12 and ignition by the ignition plug 13). This is the case before the valve (in the figure, the expansion stroke is illustrated). In this case, the drive of the injector 12 and the spark plug 13 is stopped after the exhaust valve 9 and the intake valve 8 are opened and closed. At the same time, the opening and closing operations of the intake and exhaust valves 8 and 9 of the rest cylinder are restricted. That is, after the exhaust valve 9 is opened and closed, the combustion gas in the deactivated cylinder is exhausted, and then, after the intake valve 8 is opened and closed and intake air is introduced into the deactivated cylinder, the combustion and intake and exhaust valves 8 and 9 are opened. Is stopped.

  In the present embodiment, the restriction timing and the combustion stop timing of the opening and closing operations of the intake and exhaust valves 8 and 9 of the idle cylinders (first and fourth cylinders) 2A and 2D are set in this way, so that the idle cylinder (first cylinder) 1 and 4 cylinders) 2A and 2D are switched to a resting state in which intake air before combustion is introduced inside thereof. Note that the drive stop signal to the injector 12 and the spark plug 13 and the switching command signal to the valve stop mechanism 25a are timings when the injector 12, the spark plug 13 and the intake / exhaust valves 8 and 9 are operated as described above. It may be issued at any timing. In the above description, the fuel injection is performed by the injector 12 after the intake valve 8 is closed. However, when the fuel injection is performed by the injector 12 during the valve opening period of the intake valve 8, the intake valve is closed. Since fuel has already been injected into the combustion chamber 10 at the timing after the valve and before the start of combustion, if there is a reduction cylinder operation request at this timing, the reduction cylinder control is performed until the intake valve next opens and closes. You may make it wait for a start. Of course, even if combustion has already been injected, combustion is stopped if the driving of the spark plug 13 is stopped, so the cylinder reduction control may be started at the above timing.

  In step S4, which proceeds after step S3, a timer is set. That is, when the idle cylinders (first and fourth cylinders) 2A, 2D are deactivated and the reduced cylinder operation is started, the timer is set and the time from the start of the reduced cylinder operation is measured.

  In step S5, which proceeds after step S4, the valve control unit 52 determines whether the timer value, that is, the elapsed time T from the start of the reduced cylinder operation, is shorter than a preset specific time (specific period) T0.

  As shown in FIG. 7, the specific time T0 is set to a shorter value as the engine speed is higher. The valve control unit 52 stores a map corresponding to the graph shown in FIG. 7 of the preset engine speed and the specific time T0, and extracts the specific time T0 corresponding to the current engine speed from this map. To do. The specific time T0 is set to a value of 720 ° CA or more, and the determination in step S5 is YES after at least two cycles have passed. For example, the specific time T0 is set to a value of about 10 s at an engine speed of 2000 rpm.

  If the determination in step S5 is no, the process proceeds to step S10.

  On the other hand, when the elapsed time T from the start of the reduced cylinder operation is equal to or greater than the specific time T0 and the determination in step S5 is YES, the valve control unit 52 allows the intake valve 8 to open and close and opens the intake valve 8 ( Open and close) (step S6). That is, the valve control unit 52 supplies the hydraulic pressure to the valve stop mechanism 25a so that the pivot part 22 is in the locked state (see FIG. 3A), and the idle cylinders (first and fourth cylinders) 2A, The 2D intake valve 8 can be opened and closed. Here, the valve control unit 52 controls the valve stop mechanism 25a so that the intake valve 8 opens and closes while the valve closing operation of the exhaust valve 9 is maintained. By this opening / closing operation of the intake valve 8, intake air is newly introduced into the idle cylinders (first and fourth cylinders) 2A and 2D.

  In step S7, which proceeds after step S6, the combustion control unit 53 performs combustion in the idle cylinders (first and fourth cylinders) 2A and 2D. That is, the combustion control unit 53 drives the injectors 12 and the spark plugs 13 of the idle cylinders (first and fourth cylinders) 2A and 2D to supply fuel into the idle cylinders (first and fourth cylinders) 2A and 2D. The air-fuel mixture in these cylinders is ignited and burned while being supplied.

  Here, in this embodiment, in this step S7, the combustion control unit 53 causes the spark plug 13 to ignite the air-fuel mixture at the most retarded timing when the supplied fuel can be burned in its entirety. The combustion of the air-fuel mixture is started at this timing. Here, the “total amount” includes not only the exact total amount but also an amount close to the total amount.

  Further, in the present embodiment, the expansion immediately after the intake air is newly introduced into the deactivated cylinders (first and fourth cylinders) 2A and 2D in step S6, that is, immediately after the intake stroke in which the new intake air is introduced. In the stroke, the mixture of the intake air and the fuel is burned.

  The opening / closing operation of the intake valves 8 of the deactivated cylinders (first and fourth cylinders) 2A and 2D in step S6 and the combustion in the deactivated cylinders 2A and 2D in step S7 are performed for only one cycle. Therefore, after step S7, the reduced cylinder control is resumed for only one cycle in step S8. That is, the opening / closing operation of the intake valves 8 of the deactivated cylinders (first and fourth cylinders) 2A, 2D is stopped again, the exhaust valve 9 is maintained in the opening / closing operation stop state, and combustion is stopped.

  After step S8, the ECU 50 resets the timer (step S9).

  After step S9, in detail, the operation request determination unit 51 determines whether or not there is a request to return to the reduced cylinder operation (step S10). Specifically, the operation request determination unit 51 determines that there has been a request to return to all-cylinder operation when the operation condition deviates from a specific operation condition.

  If this determination is YES, the ECU 50 ends the reduced-cylinder control and performs all-cylinder control for realizing normal all-cylinder operation (step S11). That is, the valve control unit 52 controls the hydraulic pressure of the valve stop mechanism 25a so that the pivot part 22 is in a locked state (see FIG. 3A), so that the idle cylinders (first and fourth cylinders) 2A, The 2D intake and exhaust valves 8 and 9 can be opened and closed, and the combustion control unit 53 resumes driving of the injectors 12 and the spark plugs 13 of the idle cylinders (first and fourth cylinders) 2A and 2D.

  On the other hand, when determination of step S10 is NO, ECU50 implements step S5-S10. However, in steps S5 to S10 performed after the second time, the elapsed time T is not the time from the start of the reduced cylinder operation, but the intake valves 8 in steps S6 and 7, that is, the (first and fourth cylinders) 2A and 2D. Is the elapsed time T from when the valve is opened and combustion is performed.

(5) Operation, etc. As described above, in the engine to which the engine control device according to the present embodiment is applied, during the reduced-cylinder operation (from the start of the reduced-cylinder operation to the return to the all-cylinder operation) The intake valve 8 of the idle cylinder is opened every specific time T0. Therefore, it is possible to secure high comfort by suppressing rotational fluctuation and engine vibration during the reduced-cylinder operation.

  This will be specifically described with reference to FIG. FIG. 8 shows the change over time from the start of the reduced cylinder operation (time t1) of the cylinder pressure of the deactivated cylinder. In FIG. 8, the solid line indicates the change in the in-cylinder pressure in the engine according to the present embodiment, and the broken line indicates the case where the intake valve 8 of the idle cylinder is normally closed during the reduced-cylinder operation unlike the present embodiment. A change in the in-cylinder pressure is shown.

  As shown in FIG. 8, when the reduced cylinder operation is started at time ta, the in-cylinder pressure of the deactivated cylinder gradually decreases as the opening / closing operation of the intake valve 8 and the combustion of the deactivated cylinder are stopped. To go. This is because the gas in the idle cylinder leaks to the crankcase side through the gap between the cylinder and the piston as the piston reciprocates. When the in-cylinder pressure of the idle cylinder is greatly reduced, the difference from the in-cylinder pressure of the operating cylinder, that is, the cylinder in which intake / exhaust is performed and combustion is performed increases. As a result, the rotational fluctuation increases and the engine vibration increases.

  As shown by the broken line in FIG. 8, when the intake valve 8 of the deactivated cylinder is always closed during the reduced cylinder operation, the cylinder pressure of the deactivated cylinder is greatly reduced at time t10. The vibration increases beyond the allowable range.

  In contrast, in the engine according to the present embodiment, as described above, the idle cylinder 8 is opened and intake air is introduced at the time (t1) when the specific time T0 has elapsed after the start of the reduced cylinder operation. Therefore, as shown by the solid line in FIG. 8, the in-cylinder pressure can be recovered before the in-cylinder pressure of the deactivated cylinder is significantly reduced. Here, the in-cylinder pressure is once recovered by the intake valve 8 being kept closed again, and then gradually decreases again. In the present embodiment, the intake valve 8 of the deactivated cylinder 8 is set at every specific time T0. Is opened (t2, t3, t4), so that the in-cylinder pressure of the deactivated cylinder 8 is prevented from decreasing beyond the allowable range over the entire period during which the reduced-cylinder operation is performed. It is possible to avoid the engine vibration from increasing beyond an allowable range.

  Further, in the present embodiment, since intake is introduced into the idle cylinder every specific time T0 and fuel is supplied and ignited every specific time T0 to perform combustion, the in-cylinder pressure is further increased by combustion. Can be recovered. In particular, in the present embodiment, combustion is started at the timing at which the entire amount of supplied fuel can be burned and at the most retarded timing. Therefore, it is possible to effectively increase the in-cylinder pressure and suppress a decrease in the in-cylinder pressure over a longer period. That is, when the combustion timing is relatively advanced, the combustion pressure increases and the in-cylinder pressure can be instantaneously increased, but the difference between the in-cylinder pressure and the pressure on the crankcase side increases, Immediately after that, a relatively large amount of gas leaks from the inside of the cylinder to the crankcase side, and there is a possibility that the cylinder pressure of the cylinder in the resting state cannot be maintained high. On the other hand, if the combustion timing is set to the above timing, the in-cylinder pressure can be increased by the combustion of the air-fuel mixture, and the leakage of gas in the cylinder can be suppressed by avoiding an excessive increase in the combustion pressure. It is possible to suppress a decrease in the cylinder pressure of the idle cylinder for a longer period of time.

  Moreover, in the engine according to the present embodiment, since the intake valve 8 is opened and burned intermittently, the intake valve 8 can be driven while keeping the rotational fluctuation and engine vibration small to ensure high comfort. The accompanying mechanical resistance and the increase in energy loss accompanying the drive of the injector 12 and the spark plug 13 can be suppressed to a low level, and high fuel efficiency can be ensured. Further, since the normal intake valve 8 is used as a means for introducing intake air into the deactivated cylinder, the apparatus can be simplified and cost can be reduced as compared with a case where an auxiliary valve or the like is separately provided.

  In addition, rotational fluctuations and engine vibrations are more difficult to experience as the cycle is shorter, i.e., the higher the engine speed, and when the engine speed is high, the in-cylinder pressure of the cylinders in the idle state and Comfort can be maintained even if the difference between the cylinder pressure and the cylinder pressure is relatively large. On the other hand, in the engine according to the present embodiment, the specific time T0 is set to a shorter value as the engine speed is higher. For this reason, it is possible to more reliably suppress the deterioration of the fuel consumption performance associated with the driving of the intake valve 8 by suppressing the number of driving machines for the intake valve 8 while ensuring high comfort.

  In the engine according to the present embodiment, as described above, the cylinder reduction control is started after the intake air before combustion is introduced inside, and the in-cylinder pressure is introduced inside before intake air before combustion is introduced. Since the deactivated cylinder is deactivated in a state in which the cylinder is secured at a high level, the cylinder pressure of the deactivated cylinder during the subsequent cylinder reduction operation can be maintained relatively high, and this also causes the rotational fluctuation during the cylinder reduction operation. And engine vibration can be suppressed small.

(6) Modified Example Here, in the above-described embodiment, the same timing is used to specify the timing at which intake is introduced into a deactivated cylinder (timing at which the intake valve 8 is opened) and the timing at which combustion is performed in the deactivated cylinder. Although described in the case of every time T0, these timings may be different. That is, the combustion may be performed for a while after the intake air is introduced.

  Further, in the above embodiment, the timing at which the cylinder reduction control is started in each idle cylinder is the timing after the intake valve 8 is closed and before the start of combustion (fuel injection by the injector 12 and ignition by the ignition plug 13). The case where the reduced cylinder control is started at the timing when the deactivated cylinder is deactivated while the intake air before combustion is introduced inside the cylinder is explained, but the gas after combustion is not discharged inside the deactivated cylinder. The cylinder reduction control may be started at the timing when the deactivated cylinder is deactivated in the remaining state. Specifically, when the operation timing of each idle cylinder is after the start of combustion (fuel injection by the injector 12 and ignition by the ignition plug 13) and before the exhaust valve 9 starts to open, the cylinder reduction control is started. Also good. In this way, since the cylinder reduction operation is started in a state where the in-cylinder pressure is ensured to be high by the combustion gas, the in-cylinder pressure of the deactivated cylinder during the subsequent cylinder reduction operation is maintained higher and the cylinder reduction operation is performed. The rotation fluctuation and engine vibration of the engine can be kept small.

  Moreover, the start timing of the combustion performed in the idle cylinder during the reduced cylinder operation is not limited to the above. However, as described above, if the combustion start timing is set to the most retarded timing among the timings at which the entire air-fuel mixture existing in the idle cylinder can be combusted, the combustion pressure can be kept low, so The leakage of the gas to the crankcase side is suppressed to a low level, and the in-cylinder pressure is effectively increased, whereby the decrease in the in-cylinder pressure can be suppressed for a longer period.

  Moreover, although the said embodiment demonstrated the case where the said specific period T0 was the time preset with respect to the engine speed, the setting of the specific period T0 is not restricted to this. For example, the specific period T0 may be a value that changes in accordance with the value of the in-cylinder pressure of the deactivated cylinder. That is, the period until the in-cylinder pressure value of the deactivated cylinder reaches a predetermined value is defined as a specific period T0, and the intake valve 8 of the deactivated cylinder is opened every period T0, that is, every time the in-cylinder pressure value of the deactivated cylinder becomes a predetermined value. Valves may be performed. The control procedure at the time of reduced cylinder operation in this case is shown in the flowchart of FIG. The flowchart of FIG. 9 is different from the flowchart of FIG. 5 in the part related to step S15, and the other parts are the same. Specifically, in this case, instead of the determination in step S5, that is, whether or not the elapsed time T is equal to or greater than the predetermined time T0, the determination in step S15, that is, the cylinder pressure Pc of the idle cylinder is set in advance. It is determined whether or not it is less than the reference pressure Pc0. When this determination is YES, the intake valve 8 is opened and burned. In this case, as shown in FIG. 10, it is preferable to set the reference pressure Pc0 to a lower value as the engine speed is higher. In this way, the higher the engine speed, that is, the less the rotation fluctuation and engine vibration are felt, the fewer the opportunities for the determination in step S15 to be YES, that is, the opening of the intake valve 8 and the combustion opportunity are reduced. Fuel efficiency can be increased while maintaining comfort.

  In this case, as the value of the in-cylinder pressure of the inactive cylinder, an in-cylinder pressure sensor capable of detecting the in-cylinder pressure may be provided in the inactive cylinder, or the value of the in-cylinder pressure estimated from rotational fluctuations may be used. .

  Further, instead of the in-cylinder pressure value of the deactivated cylinder, the difference between the in-cylinder pressure of the deactivated cylinder and the in-cylinder pressure of the operating cylinder is used, and the intake valve 8 of the deactivated cylinder is opened each time the differential pressure reaches a predetermined value. May be performed. Also in this case, the differential pressure estimated from the rotational fluctuation or the like may be used as the differential pressure.

2A to 2D cylinder
8 Intake valve
9 Exhaust valve 25a Valve stop mechanism 50 ECU (control means)

Claims (7)

A control device for an engine having a plurality of cylinders that includes an intake valve and an exhaust valve and in which combustion of a mixture of air and fuel is performed,
A valve stop mechanism for restricting the opening and closing operations of an intake valve and an exhaust valve of a specific cylinder among the plurality of cylinders and holding the valve closed;
Control means capable of controlling each part of the engine including the valve stop mechanism,
The control means includes
When the engine is in a specific operating condition, the valve stop mechanism controls the opening / closing operation of the intake valve and the exhaust valve of the specific cylinder, and the cylinder reduction control for stopping the fuel supply to the specific cylinder. And performing a reduced-cylinder operation in which the specific cylinder is in a dormant state,
During the reduced-cylinder operation, the restriction of the opening / closing operation of the intake valve of the specific cylinder by the valve stop mechanism is released for each specific period to open / close the intake valve, and the exhaust valve of the specific cylinder The most retarded timing among the timings at which the air-fuel mixture existing in the specific cylinder can be burned in full for each predetermined period while maintaining the regulation of the opening / closing operation and during the reduced cylinder operation An engine control apparatus for burning an air-fuel mixture in the specific cylinder . The engine control device according to claim 1,
The engine control apparatus is characterized in that the specific period is set longer as the engine speed is higher. The engine control apparatus according to claim 1 or 2,
The engine control device according to claim 1, wherein the control means starts the cylinder reduction control at a timing when the cylinder enters a resting state in a state where intake air before combustion is introduced into the specific cylinder. The engine control apparatus according to claim 1 or 2,
The engine control is characterized in that the control means starts the cylinder reduction control at a timing when the cylinder is in a resting state in a state where the burned gas remains without being discharged from the specific cylinder. apparatus. A control device for an engine having a plurality of cylinders that includes an intake valve and an exhaust valve and in which combustion of a mixture of air and fuel is performed,
A valve stop mechanism for restricting the opening and closing operations of an intake valve and an exhaust valve of a specific cylinder among the plurality of cylinders and holding the valve closed;
Control means capable of controlling each part of the engine including the valve stop mechanism,
The control means includes
When the engine is in a specific operating condition, the valve stop mechanism controls the opening / closing operation of the intake valve and the exhaust valve of the specific cylinder, and the cylinder reduction control for stopping the fuel supply to the specific cylinder. And performing a reduced-cylinder operation in which the specific cylinder is in a dormant state,
During the reduced-cylinder operation, the restriction of the opening / closing operation of the intake valve of the specific cylinder by the valve stop mechanism is released for each specific period to open / close the intake valve , and during the reduced-cylinder operation, Each time period, the air-fuel mixture is burned in the specific cylinder at the most retarded timing among the timings at which the entire air-fuel mixture existing in the specific cylinder can be burned .
The specific period is a period until it is determined that the in-cylinder pressure of the specific cylinder is less than a reference pressure set in advance in order to suppress rotation fluctuation and vibration of the engine during the reduced cylinder operation. An engine control device. A control device for an engine having a plurality of cylinders that includes an intake valve and an exhaust valve and in which combustion of a mixture of air and fuel is performed,
A valve stop mechanism for restricting the opening and closing operations of an intake valve and an exhaust valve of a specific cylinder among the plurality of cylinders and holding the valve closed;
Control means capable of controlling each part of the engine including the valve stop mechanism,
The control means includes
When the engine is in a specific operating condition, the valve stop mechanism controls the opening / closing operation of the intake valve and the exhaust valve of the specific cylinder, and the cylinder reduction control for stopping the fuel supply to the specific cylinder. And performing a reduced-cylinder operation in which the specific cylinder is in a dormant state,
During the reduced-cylinder operation, the restriction of the opening / closing operation of the intake valve of the specific cylinder by the valve stop mechanism is released for each specific period to open / close the intake valve , and during the reduced-cylinder operation, Each time period, the air-fuel mixture is burned in the specific cylinder at the most retarded timing among the timings at which the entire air-fuel mixture existing in the specific cylinder can be burned .
In the specific period, a differential pressure between an in-cylinder pressure of the specific cylinder and an in-cylinder pressure of an operating cylinder that continues combustion in the reduced-cylinder operation is provided to suppress rotational fluctuation and vibration of the engine during the reduced-cylinder operation. An engine control device characterized by a period until the predetermined value is reached. The engine control device according to claim 5 or 6 ,
The control device for an engine, wherein the control means maintains the restriction of the opening / closing operation of the exhaust valve of the specific cylinder during the specific period.

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