JP2016050510A - Control device of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further surely avoid occurrence of a torque shock at changeover to reduced-cylinder operation from full-cylinder operation.SOLUTION: When there is a changeover request to reduced-cylinder operation from full-cylinder operation, an opening 34a of a throttle valve is changed so that an air quantity sucked into each cylinder 2A to 2D becomes an air quantity at the reduced-cylinder operation which is larger than an air quantity at normal full-cylinder operation, performs preparation control for changing the ignition timing of ignition means to timing on a retard angle side rather than ignition timing at the normal full-cylinder operation so as to cancel an increase of engine torque which occurs accompanied with the opening change of the throttle valve, and starts the reduced-cylinder operation after the finish of the preparation control.SELECTED DRAWING: Figure 7

Description

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

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

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

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

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

JP 11-336575 A

  In the apparatus disclosed in Patent Document 1, the amount of air taken into each cylinder is increased before the combustion of some cylinders is stopped. Insufficient amount can be suppressed. However, if the amount of air sucked into each cylinder is simply increased before the start of the reduced cylinder operation, that is, when all the cylinders are combusting, the output of the entire engine before the start of the reduced cylinder operation is started. Will increase, and torque shock will also occur.

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

  In order to solve the above-described problems, the present invention provides a plurality of cylinders having an intake valve and an exhaust valve, and an ignition that is provided in each cylinder and applies ignition energy to an air-fuel mixture in these cylinders. All-cylinder operation in which combustion of the air-fuel mixture is performed in all the cylinders, and a throttle valve provided in an intake passage connected to each cylinder and capable of changing the amount of air sucked into these cylinders And a device that controls an engine that can be switched between a reduced-cylinder operation in which combustion in a specific cylinder among a plurality of cylinders is stopped and the specific cylinder is deactivated. Control for controlling each part of the engine including a valve stop mechanism that switches between a state in which the intake and exhaust valves of the cylinder can be opened and closed and a state in which the valve is kept closed, and the valve stop mechanism, the throttle valve, and the ignition means Means and When there is a request for switching from all-cylinder operation to reduced-cylinder operation, the control means reduces the amount of air sucked into each cylinder more than the amount of air during normal all-cylinder operation where the request for switching is not issued. The ignition timing of the ignition means is set to a normal value so that the opening amount of the throttle valve is changed so as to be the air amount at the time of cylinder operation and the increase in engine torque caused by the change in the opening amount of the throttle valve is canceled. Preliminary control is performed to change to a timing that is retarded from the ignition timing during all cylinder operation, and after completion of the preliminary control, the intake valve and exhaust valve of the specific cylinder are held closed by the valve stop mechanism. And ignition of the ignition means for the specific cylinder is stopped to start the reduced-cylinder operation (Claim 1).

  According to the present invention, when switching from all-cylinder operation to reduced-cylinder operation, the opening of the throttle valve is changed to the open side before starting reduced-cylinder operation, that is, before stopping combustion in a specific cylinder. Since the amount of air sucked into each cylinder is increased toward the amount of air for the reduced-cylinder operation, a sufficient amount of air is drawn into each operating cylinder at the start of the reduced-cylinder operation. It is possible to suppress a decrease in the output of the operating cylinder, that is, the engine torque at the start of the reduced cylinder operation. In addition, in the present invention, the ignition timing is retarded from the normal all-cylinder operation while changing the throttle valve opening to the open side to increase the amount of air sucked into each cylinder. However, the timing is changed to cancel the increase in engine torque that occurs with the change in the throttle valve opening. Therefore, it is possible to suppress an increase in engine torque due to an increase in the amount of air sucked into each cylinder, and increase / decrease in engine torque, that is, torque shock before and after switching from full cylinder operation to reduced cylinder operation. Can be more reliably avoided.

  In the present invention, the control means determines the ignition timing according to the operating conditions during the normal operation where the preparatory control is not performed, and the determined ignition timing exceeds the preset retard limit and is retarded. While the preparatory control is being performed, it is preferable to allow the ignition timing to exceed the retard limit and to become a retarded timing (Claim 2).

  In this way, during the normal operation, the ignition timing exceeds the preset retard limit, and the ignition timing is set to the retarded timing while avoiding misfire and the like, while performing the preparation control, It is possible to more reliably avoid the occurrence of torque shock before and after switching from all-cylinder operation to reduced-cylinder operation by reliably changing the engine torque increase caused by changing the throttle valve opening. it can.

  In addition, the control means prohibits the ignition timing from being retarded beyond a preset first retard limit during normal operation when the preparation control is not performed, while the preparation control is performed. If it is, the ignition timing is prohibited from being retarded beyond a preset second retard limit, and the second retard limit is set to be retarded from the first retard limit. (Claim 3).

  Even in this configuration, the second retard limit for the preparation control is set to be retarded from the first retard limit for the normal operation, so that the ignition timing is set to the retard limit set in advance during the normal operation. While avoiding misfire and the like, the ignition timing is reliably changed according to the timing to cancel the increase in engine torque that accompanies the change in throttle valve opening, while avoiding misfire and the like. Thus, it is possible to more reliably avoid the occurrence of torque shock before and after switching from all-cylinder operation to reduced-cylinder operation.

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

1 is a schematic plan view showing an overall configuration of an engine according to an embodiment of the present invention. It is sectional drawing of an engine main body. (A) It is a figure which shows a valve stop mechanism when a pivot part is a locked state. (B) It is a figure which shows the valve stop mechanism before a pivot part transfers to a lock release state. (C) It is a figure which shows a valve stop mechanism when a pivot part is a lock release state. It is the figure which showed the path | route of the hydraulic fluid of a valve stop mechanism. It is a block diagram which shows the control system of an engine. It is the figure which showed the all cylinder operation area | region and the reduced cylinder operation area | region. It is the flowchart which showed the control procedure at the time of the switch from all cylinder operation to reduction cylinder operation. It is the figure which showed the time change of each parameter at the time of implementing 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 conventional control. 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 12 (FIG. 1) described later is supplied to the combustion chamber 10. The supplied fuel burns in the combustion chamber 10, and the piston 11 pushed down by the expansion force due to the combustion reciprocates in the vertical direction.

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

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

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

  The engine of the present embodiment is a variable cylinder engine capable of performing an operation in which two of the four cylinders 2A to 2D are 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. An openable / closable throttle valve 34 a for adjusting the flow rate of intake air introduced into the engine body 1 is provided in the middle of the intake pipe 33. The intake pipe 33 is provided with a valve actuator 34b for driving the throttle valve 34a. The throttle valve 34a is opened and closed by the valve actuator 34b.

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

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

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

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

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

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

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

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

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

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

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

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

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

  As shown in FIG. 4, in 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 of the intake passage 30 is provided with an intake air amount sensor SN3 that detects the amount of air that passes through the surge tank 32 and is introduced into each of the cylinders 2A to 2D, and detects the pressure in the surge tank 32. An intake pressure sensor SN4 is provided.

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

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

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

  More specific functions of the ECU 50 will be described. The ECU 50 includes, 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 the engine 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. It is determined whether to select a reduced-cylinder operation or an all-cylinder operation. For example, as shown in FIG. 6, the operation request determination unit 51 pauses the first and fourth cylinders 2A and 2D when the engine load and the engine speed are in a specific operation region A1 that is relatively low (first 2) It is determined that there is a request for reduced-cylinder operation in which only the third cylinders 2B and 2C are operated. Conversely, when the engine load and the engine speed are in the remaining operation region A2 excluding the specific operation region A1, it is determined that there is a request for all-cylinder operation to operate all the first to fourth cylinders 2A to 2D. . In addition, the operation request determination unit 51 determines that the all-cylinder operation is performed when it is cold or acceleration / deceleration is severe. For example, when the engine water temperature detected by the water temperature sensor SN6 is equal to or lower than a predetermined value or when the change rate of the accelerator opening detected by the accelerator opening sensor SN5 is large, the operation request determination unit 51 operates all cylinders. Is determined to be implemented.

  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 air amount that is the amount of air taken into each cylinder. The spark plug controller 53 controls the spark plug 13. The injector control unit 54 controls the injector 12. The valve stop mechanism control unit 55 controls the valve stop mechanism solenoid valve 42 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 based on the required cylinder filling efficiency and the surge tank reference volume efficiency that is preset according to the engine operating state, for example, the engine speed, the phase of the intake VVT 29a, and the like. Calculated.

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

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

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

  The spark plug controller 53 switches the control of the spark plug 13 of the idle cylinders (first and fourth cylinders 2A and 2D) depending on whether the cylinder reduction operation or the all cylinder operation is performed. That is, when the engine is operating in all cylinders, the spark plug 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 combustion control unit 54 prohibits the driving of the spark plug 13 of the cylinder in order to stop the combustion in the idle cylinders (first and fourth cylinders 2A and 2D). To do.

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

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

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

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

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

(4-2) 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 idle cylinders (first and fourth cylinders 2A and 2D) is stopped immediately after a request for switching from all-cylinder operation to reduced-cylinder operation is performed. If the operation is started, the intake amount of the operating cylinders (the second and third cylinders 2B and 2C) is insufficient, the engine torque is reduced, and a torque shock may occur. 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 to change the opening of the throttle valve 34a so that the intake amount per cylinder becomes the intake amount during the reduced cylinder operation. As described above, the intake amount per cylinder during the reduced-cylinder operation is made larger than the intake amount per cylinder during the normal all-cylinder operation where the preparation control is not performed. Therefore, the throttle valve control unit 52 sets the opening of the throttle valve 34a as a preparatory control from 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. Also controls the opening 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 the preparation operation is started, the throttle valve The opening of 34a is changed to the opening at the time of reduced-cylinder operation, that is, the open side. That is, in the present embodiment, the throttle valve control unit 52 immediately starts the control during the reduced-cylinder operation when a request for switching from the all-cylinder operation to the reduced-cylinder operation is issued.

  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 also control the injector 12 and the spark plug 13 so that combustion is performed in all the cylinders 2A to 2D as 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).

  As described above, in this apparatus, even when 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 as the intake amount during the reduced cylinder operation and larger than the intake amount during the normal all cylinder operation. Therefore, if combustion is performed in all of the cylinders 2A to 2D in a state where the intake amount is large in this way, the engine torque is the torque at the time of normal all-cylinder operation, that is, the torque immediately before the start of the preparation control, and the driver It will be higher than the torque requested from

  Therefore, in the present apparatus, during the preparation control, the ignition timing is retarded to a timing at which an increase in engine torque caused by the increase in the intake air amount can be avoided. That is, in the preparation control, the spark plug control unit 53 controls the ignition timing to be retarded from the ignition timing during normal all-cylinder operation, that is, the ignition timing immediately before the start of the preparation control.

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

  Here, there is a risk of misfire if the ignition timing is retarded excessively. Therefore, in this embodiment, even when the semi-control is performed, the ignition timing is prevented from being retarded beyond a preset limit timing. However, when the preparation control is performed, the ignition timing is allowed to be retarded to a more retarded side than the retard limit in the normal control described in 4-1 above. That is, also in the preparation control, the spark plug control unit 53 determines a more advanced timing among the preset preparation control retard limit (second retard limit) and the above-determined ignition timing for preparation control. Is determined as the final ignition timing, but the retard limit for the preparation control is set to be more retarded than the retard limit used during normal operation. Note that the retard limit for the preparation control is set in advance for each of the operating conditions (engine speed, engine load, etc.), for example, and stored in a map, similarly to the retard limit at the normal time.

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

  As described above, the preparation control is a control for avoiding the occurrence of a torque shock due to a decrease in engine torque due to a shortage of intake air in the operating cylinder when switching from all-cylinder operation to reduced-cylinder operation. Therefore, the reduced-cylinder operation start determination unit 56 basically 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. .

  However, if the ignition timing is excessively retarded for a long time, the possibility of misfire increases. Therefore, in this embodiment, in order to avoid misfire more reliably, the reduced-cylinder operation start determination unit 56, when the period when the ignition timing becomes the retard limit for the preparation control exceeds a preset reference time, Even if the intake air amount has not reached the intake air amount during the reduced-cylinder operation, it is determined that the preparation control is ended and the reduced-cylinder operation is started.

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

  First, in step S1, the engine load, the engine speed, the water temperature, the accelerator opening, and the like specified by the detection values of the sensors are read. Next, in step S2, it is determined whether or not there has been a request from the all-cylinder operation to the reduced-cylinder operation. As described above, this determination is performed by the operation request determination unit 51. The operation request determination unit 51 determines whether the engine load and the engine speed are 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 from all-cylinder operation to reduced-cylinder operation (should not be shifted from all-cylinder operation to reduced-cylinder operation), the process proceeds to step S3. Maintain cylinder operation. On the other hand, if the determination in step S2 is YES and there is a request from the all cylinder operation to the reduced cylinder operation, the process proceeds to step S4.

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

  In step S5 following step S4, the opening of the throttle valve 34a is changed to the opening side rather than the normal all-cylinder operation.

  In step S6, which proceeds after step S5, the ignition timing is set to the retarded side with respect to the normal all-cylinder operation. In the present embodiment, as described above, the spark plug control unit 53 sets the ignition timing from an ignition timing during normal all-cylinder operation to an amount corresponding to an increase in intake air amount from the target intake air amount during all-cylinder operation. Of the retarded ignition timing and the retard limit for preparation control, the timing on the advance side is determined as the final ignition timing.

  In step S7 following step S6, it is determined whether the intake air amount has reached the intake air amount during the reduced cylinder operation. If the determination in step S7 is yes, the process proceeds to step S9. On the other hand, if the determination in step S7 is NO and the intake air amount has not reached the intake air amount during the reduced-cylinder operation, the process proceeds to step S8, and the time when the ignition timing becomes the retard limit for preparation control continues for a predetermined time. It is determined whether or not.

  If the determination in step S8 is YES and the time when the ignition timing reaches the retard limit for preparation control continues for a predetermined time, the process proceeds to step S9. On the other hand, if the determination in step S8 is NO, the process returns to step S4, and steps S5 to S8 are repeated.

  In step S9, reduced-cylinder operation is started. That is, when the intake air amount reaches the intake air amount during the reduced-cylinder operation (determination in step S7 is YES) or when the preparation control retard limit continues for a predetermined time (determination in step S8 is YES), the reduced-cylinder operation starts. Then, the ignition and fuel injection of the deactivated cylinders (first and fourth cylinders 2A and 2D) are stopped, and the solenoid valve 42 for the valve stop mechanism is turned on to deactivate the deactivated cylinders (first and fourth cylinders 2A and 2D). ) Are closed and the ignition control of the operating cylinders (second and third cylinders 2B and 2C) is switched to the control during normal reduced-cylinder operation.

(5) Operation, etc. FIG. 8 shows the results when the control according to this embodiment is performed. As a comparative example, the results when the above preparation control is not performed are shown in FIGS. FIG. 9 shows the result when the reduced-cylinder operation is started immediately when the switching request is made, and FIG. 10 does not carry out the control for retarding the ignition timing in the preparation control at the time of the switching. Is the result of the case. In these figures, the uppermost graph shows the change of the switching flag from all-cylinder operation to reduced-cylinder operation, and changes from 0 to 1 when a request for switching from all-cylinder operation to reduced-cylinder operation is issued. To do.

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

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

  On the other hand, in the apparatus according to the present embodiment, as shown in FIG. 8, after there is a request for switching from all-cylinder operation to reduced-cylinder operation at time t1, the idle cylinders (first, fourth) (Cylinders 2A, 2D) without stopping combustion, the throttle valve 34a is changed to the open side, and the intake air amount (intake amount per cylinder, charging efficiency) is increased to the amount during the reduced cylinder operation. Furthermore, the ignition timing is retarded in accordance with the amount of increase in the intake air amount. Therefore, it is possible to avoid an increase in output from each cylinder while increasing the intake air amount, and to avoid an increase or decrease in engine torque. In other words, the engine torque can be maintained substantially constant when switching from all-cylinder operation to reduced-cylinder operation, and generation of torque shock can be avoided during this switching.

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

(6) Modified Example Here, in the above-described embodiment, the case where the ignition timing is prohibited from being retarded beyond the preset retard limit for the preparatory control when performing the preparatory control has been described. The restriction on the ignition timing may be released. That is, when the preparation control is performed, the retard amount of the ignition timing may be allowed without limitation. However, if the ignition timing is retarded excessively, misfire or the like may occur. Therefore, if the above regulation is performed, this misfire or the like can be avoided more reliably.

  In the above embodiment, the case where the retard limit for preparation control is set to the retard side with respect to the retard limit at the normal time has been described, but these may be set to the same value. However, if the retard limit for the preparation control is set to the more retarded side and the ignition timing is allowed to become more retarded during the preparation control, the ignition timing is adjusted in accordance with the increase in the intake amount while avoiding misfire and the like. The angle can be retarded more appropriately, and the occurrence of torque shock can be avoided more reliably.

  Further, in the above embodiment, it is determined whether or not the preparation control is ended and the reduced cylinder operation is started, whether or not the intake amount has reached the intake amount during the reduced cylinder operation, and the ignition timing is the preparation control. Although the case where it performed by whether the period used as the retard limit was continued more than predetermined period was demonstrated, the specific content of this determination is not restricted to this. For example, the determination based on the ignition timing may be omitted. Further, regarding the determination of the ignition timing, instead of the above determination, it may be determined that the preparation control is terminated when the ignition timing reaches a predetermined timing. In addition, regarding the determination of the intake air amount, instead of the above determination, it may be determined that the preparation control is terminated when the difference between the actual intake air amount and the intake air amount during the reduced cylinder operation becomes a predetermined value or less. Also, instead of determining the intake air amount, the engine torque when the reduced-cylinder operation is temporarily started is estimated every time during the preparation control, and the estimated engine torque and the current engine torque, that is, requested by the driver, etc. It may be determined that the preparation control is terminated when the difference from the engine torque that has been set is equal to or less than a predetermined value.

  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 13 Spark plug (ignition means)
25a Valve stop mechanism 50 ECU (control means)

Claims (3)

A plurality of cylinders provided with an intake valve and an exhaust valve, ignition means provided in each cylinder for applying ignition energy to an air-fuel mixture in these cylinders, and an intake passage connected to each cylinder All-cylinder operation in which air-fuel mixture combustion is performed in all cylinders, and combustion in a specific cylinder among a plurality of cylinders Is an apparatus that controls an engine that can be switched between a reduced-cylinder operation in which the specific cylinder is stopped and the specific cylinder is deactivated.
A valve stop mechanism for switching between a state in which the intake valve and the exhaust valve of the specific cylinder can be opened and closed and a state in which the valve is held;
Control means for controlling each part of the engine including the valve stop mechanism, the throttle valve, and the ignition means,
When there is a request for switching from all-cylinder operation to reduced-cylinder operation, the control means reduces the amount of air sucked into each cylinder more than the amount of air during normal all-cylinder operation where no request for switching is issued. The ignition timing of the ignition means is set to a normal value so that the opening amount of the throttle valve is changed so as to be the air amount at the time of cylinder operation and the increase in engine torque caused by the change in the opening amount of the throttle valve is canceled. Preliminary control is performed to change to a timing that is retarded from the ignition timing during all cylinder operation, and after completion of the preliminary control, the intake valve and exhaust valve of the specific cylinder are held closed by the valve stop mechanism. And stopping the ignition of the ignition means of the specific cylinder and starting the reduced-cylinder operation. The engine control device according to claim 1,
The control means determines the ignition timing according to the operating conditions during normal operation when the preparation control is not performed, and the determined ignition timing exceeds the preset retard limit and becomes the retarded timing While the preparatory control is being performed, the engine control device is characterized in that the ignition timing is allowed to exceed the retard limit and become a retarded timing. The engine control device according to claim 1 or 2,
The control means prohibits the ignition timing from being retarded beyond a preset first retard limit during normal operation when the preparation control is not performed, while the preparation control is performed. The ignition timing is prohibited from being retarded beyond the preset second retard limit,
The engine control apparatus according to claim 1, wherein the second retard limit is set to be retarded from the first retard limit.

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