JP6197806B2 - Engine control device - Google Patents

Description

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

  Conventionally, various studies have been conducted to improve the fuel efficiency of an engine. As one technique for improving the fuel efficiency, as disclosed in Patent Document 1, in a multi-cylinder engine having a plurality of cylinders, combustion in some cylinders is stopped in a predetermined operation region, and these cylinders are stopped. Is known that performs a reduced-cylinder operation in which the engine is put into a rest state and combustion is performed only in the remaining cylinders.

JP 58-187508 A

  According to the above technique, by stopping some of the cylinders, it is possible to reduce the pumping loss and the like caused by operating these cylinders, and to improve the fuel efficiency.

  However, there is still a high demand for improvement in fuel efficiency, and there is a demand for further improvement in fuel efficiency in an engine that stops combustion in some cylinders as described above.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an engine control device that can further improve fuel efficiency in a multi-cylinder engine that performs reduced-cylinder operation.

In order to solve the above problems, the present invention has a plurality of cylinders having an intake valve for opening and closing an intake port and an exhaust valve for opening and closing an exhaust port, and combustion of the air-fuel mixture is performed in all the cylinders. Is a device that controls an engine that can be switched between all-cylinder operation and reduced-cylinder operation in which combustion in a specific cylinder among a plurality of cylinders is stopped, and is provided in each cylinder. Ignition means for igniting the air-fuel mixture, fuel injection means provided in each cylinder for injecting fuel into these cylinders at a predetermined fuel injection timing, and an intake air amount that is the amount of air sucked into each cylinder Changeable intake air amount changing means, a valve stop mechanism for switching the intake valve and exhaust valve of the specific cylinder to a state in which the intake valve and the exhaust valve can be opened and closed, and a state in which the valve is held, the ignition means, fuel injection means, intake air Including volume change means and valve stop mechanism And control means for controlling each part of the engine, the control means, in the case where there is a switching request into the reduced-cylinder operation from the all-cylinder operation, the closing timing is compression bottom dead center of the intake valve of the particular cylinder If the gas is in the retarded timing and the gas in the cylinder is blown back to the intake port, at least the fuel injection timing in the specific cylinder is the same as the fuel before combustion injected into the cylinder. After the control is performed on the specific cylinder, the control is performed to retard the fuel injection timing to the predetermined timing by delaying the fuel injection timing to the predetermined timing, which can be prevented from being pushed out together with the blowback gas from the cylinder. From the first expansion stroke that the cylinder reaches after the end of this control to the next expansion stroke, the fuel injection and ignition for the specific cylinder are stopped within the switching start cycle. The controls the fuel injection means and the ignition means, the intake and exhaust valves of the specific cylinder driving the valve stop mechanism to switch to the closed holding state in the next cycle of the switch starting cycle (Claim 1).

  According to the present invention, at the time of switching from all-cylinder operation to reduced-cylinder operation, a part of the fuel injected into a specific cylinder is prevented from being discharged outside the cylinder without being converted into an effective engine output. In addition, the fuel efficiency can be improved and the exhaust performance can be improved by suppressing the discharge of unburned gas to the outside.

  Specifically, when fuel is accumulated in the intake port, if the intake / exhaust valve is opened and closed with ignition stopped in the switching start cycle, the intake port opens and the intake port enters the cylinder. As fuel flows in, the fuel may not be ignited (combusted), that is, may not be converted into effective engine torque and discharged out of the cylinder.

  That is, if the closing timing of the intake valve is set to a timing that is retarded from the compression bottom dead center and the gas in the cylinder is blown back to the intake port, the piston rises in the compression stroke. Along with this, the fuel in the cylinder is pushed out to the intake port together with the blowback gas to the intake port and stays in the intake port. Then, this fuel flows again into the cylinder from the intake port when the next intake valve is opened (next cycle). Here, if the fuel returned to the cylinder is not ignited, the fuel is not burned, but through the gap between the piston and the cylinder, or from the reduced cylinder operation to the all cylinder operation. As the exhaust valve opens at the time of recovery, the exhaust valve is discharged to the outside through the exhaust port.

  On the other hand, in the present invention, when the closing timing of the intake valve is the timing at which the gas in the cylinder returns to the intake port, the fuel injection timing is set in the cycle before the switching start cycle. The timing is delayed when the fuel in the cylinder is not pushed out to the intake port. Therefore, it is possible to avoid the fuel being pushed out to the intake port in the cycle before the switching start cycle. Therefore, in the switching start cycle, the fuel reflows into the cylinder from the intake port, and this reflowed fuel is not converted into effective engine torque, and is prevented from being discharged outside without being burned. And high fuel efficiency and exhaust performance can be secured.

  In the present invention, the control means, after the request to switch from all cylinder operation to reduced cylinder operation, and before stopping the ignition and fuel injection of the specific cylinder, by the intake air amount changing means, Increase the intake air amount of each cylinder to the intake air amount during reduced-cylinder operation that is larger than the intake air amount during normal all-cylinder operation for which no switching request has been issued, and set the ignition timing of each cylinder to normal all-cylinder operation It is preferable to carry out a preparation control that is retarded from the ignition timing at that time (Claim 2).

  If it does in this way, it can avoid that a torque shock arises at the time of switching from all cylinder operation to reduction cylinder operation, improving fuel consumption performance as mentioned above.

  Specifically, in this configuration, the intake air amount is increased to the intake air amount during the reduced cylinder operation before the start of the reduced cylinder operation. Therefore, it is possible to avoid a decrease in engine torque due to an insufficient intake amount of the operating cylinder at the start of the reduced cylinder operation. In addition, with this configuration, it is possible to suppress the increase in engine torque accompanying the increase in the intake air amount by retarding the ignition timing. Therefore, fluctuations in engine torque can be suppressed before and after the start of reduced-cylinder operation, and the occurrence of torque shock can be avoided more reliably.

  Here, when the ignition timing is retarded as described above, the fuel efficiency may be lowered. However, in the present invention, as described above, fuel efficiency can be improved by suppressing a part of the fuel from being discharged outside without being converted into an effective engine output. Therefore, the improvement in the fuel consumption performance can compensate for the reduction in the fuel consumption performance and ensure high fuel consumption performance.

  In the present invention, the control means is configured such that the closing timing of the intake valve of the specific cylinder is a timing retarded from the compression bottom dead center in all cycles during the preparation control. When it is time for the gas inside to blow back to the intake port, it is preferable to perform control to retard the fuel injection timing to the predetermined time.

  In this way, it is not necessary to secure a cycle for changing the fuel injection timing between the end cycle of the preparation control and the start cycle (switching start cycle) of the reduced cylinder operation. Therefore, it is possible to start the reduced-cylinder operation earlier while suppressing the reinflow of fuel from the intake port into the cylinder in the switching start cycle, and it is possible to improve the fuel efficiency more reliably.

  As a configuration different from the above, when there is a request for switching from all-cylinder operation to reduced-cylinder operation, the control means compresses the closing timing of the intake valve of the specific cylinder in the cycle immediately before the switching start cycle. Control may be performed to retard the fuel injection timing to the predetermined timing when it is the timing retarded from the bottom dead center and when the gas in the cylinder returns to the intake port. ).

  This makes it possible to improve fuel efficiency by suppressing the reinflow of fuel from the intake port into the cylinder in the switching start cycle while setting the fuel injection timing to a more appropriate timing according to the operating conditions.

  As described above, according to the engine control apparatus of the present invention, fuel efficiency can be further improved in a multi-cylinder engine that performs 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 figure which showed typically the mode of fuel-injection timing, the ignition timing, and the intake / exhaust valve in the case where reflow of fuel arises. (A) It is the figure which showed typically the mode in the cylinder in an intake stroke. (B) It is the figure which showed typically the mode in the cylinder in a compression stroke. (C) It is the figure which showed typically a mode that the fuel was extruded to the intake port. (D) It is the figure which showed typically a mode that a fuel reflowed in a cylinder from an intake port. It is the figure which showed typically the mode of fuel injection timing, ignition timing, and an intake / exhaust valve when change control of fuel injection timing was implemented. It is the flowchart which showed the control procedure which concerns on one Embodiment of this invention at the time of the switch from all cylinder operation to reduced cylinder operation.

(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-stroke multi-cylinder gasoline engine mounted on a vehicle as a power source for traveling. Specifically, this engine is generated by an in-line four-cylinder engine main body 1 having four cylinders 2A to 2D arranged in a straight line, an intake passage 30 for introducing air into the engine main body 1, and the engine main body 1. And an exhaust passage 35 for discharging the exhaust gas.

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

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

  The piston 11 is connected to a crankshaft 15 that is an output shaft of the engine main body 1 via a connecting rod 14, and the crankshaft 15 rotates about the central axis in accordance with the reciprocating motion of the piston 11. . The crankshaft 15 rotates by 720 ° CA in one cycle, and in each of the cylinders 2A to 2D, four strokes of an intake stroke → compression stroke → expansion stroke → exhaust stroke are performed during 720 ° CA.

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

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

  The engine of the present embodiment is a variable cylinder engine capable of performing an operation in which two of the four cylinders 2A to 2D are stopped without burning and the remaining two cylinders are operated, that is, a reduced-cylinder operation. . For this reason, the ignition sequence as described above is for normal operation that is not reduced-cylinder operation (during all-cylinder operation in which all four cylinders 2A to 2D are operated). On the other hand, during the reduced-cylinder operation, the ignition operation of the spark plug 13 is prohibited in two cylinders (the first cylinder 2A and the fourth cylinder 2D in this embodiment) whose ignition order is not continuous, and ignition is performed by skipping one. become.

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

  As shown in FIG. 1, the intake passage 30 includes four independent intake passages 31 communicating with the intake ports 6 of the cylinders 2 </ b> A to 2 </ b> D, and upstream ends of the individual intake passages 31 (on the upstream side in the intake flow direction). A surge tank 32 commonly connected to the end) and a single intake pipe 33 extending upstream from the surge tank 32. A throttle valve 34 a that can open and close a passage in the intake pipe 33 is provided in the middle of the intake pipe 33. The intake pipe 33 is provided with a valve actuator 34b for driving the throttle valve 34a. The throttle valve 34a is opened and closed by the valve actuator 34b. The flow rate of the intake air introduced into the engine main body 1 is changed by opening and closing the throttle valve 34a, and the throttle valve 34a and the valve actuator 34b can change the intake air amount that is the amount of air sucked into each cylinder. Function as.

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

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

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

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

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

  The valve operating mechanism 28 for the intake valve 8 includes an intake variable valve timing mechanism 28a (see FIG. 5) that changes the phase of the cam shaft 18 with respect to the crankshaft 15 and thereby changes the opening / closing timing of the intake valve 8. Is provided. The intake variable valve timing mechanism 28a is a well-known device, and a detailed description thereof is omitted. In the present embodiment, a hydraulic type is used as the intake variable valve timing mechanism 28a, and the valve opening timing of the intake valve 8 and the valve closing timing IVC of the intake valve 8 (hereinafter simply referred to simply as “hydraulic pressure”) are used in accordance with the supplied hydraulic pressure. , Sometimes referred to as intake valve closing timing). In the present embodiment, the opening / closing timing of the intake valve 8 is changed while the valve opening period is maintained constant.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

  The ECU 50 is electrically connected to these sensors SN1 to SN6, and based on signals input from the respective sensors, the various information engine speeds, cylinder information, intake air amount, intake air pressure, accelerator opening described above. Get the engine water temperature).

  And ECU50 controls each part of an engine, performing various determination, a calculation, etc. based on the input signal from each said sensor SN1-SN6. That is, the ECU 50 is electrically connected to the injector 12, spark plug 13, valve actuator 34b (throttle valve 34a), valve stop mechanism solenoid valve 42 (valve stop mechanism 25a), and intake variable valve timing mechanism 28a. Based on the result of the above calculation, a drive control signal is output to each of these devices. In this embodiment, there are a total of four sets of injectors 12 and spark plugs 13 at a rate of one set per cylinder. In FIG. 5, the injectors 12 and the spark plugs 13 are each represented by one block. . Further, one valve stop mechanism solenoid valve 42 is provided for each of the valve stop mechanism 25a of the first cylinder 2A and the valve stop mechanism 25a of the fourth cylinder 2D, for a total of two valve stop mechanisms. There is a solenoid valve 42 for use, and this is shown in one block in FIG.

  More specific functions of the ECU 50 will be described. The ECU 50 includes, as functional elements, an operation request determination unit 51, a throttle valve control unit 52, a spark plug control unit 53, an injector control unit 54, a valve stop mechanism control unit 55, a reduced cylinder operation start determination unit 56, an intake opening / closing timing control. A portion 57 is provided.

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

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

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

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

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

  The valve stop mechanism control unit 55 controls the solenoid valve 42 for the valve stop mechanism to control the hydraulic pressure supplied to the valve stop mechanism 25a of the S-HLA 25, that is, the intake and exhaust valves 8, 9 of the first and fourth cylinders 2A, 2D. The opening / closing operation is changed.

  The intake opening / closing timing control unit 57 controls the intake variable valve timing mechanism 28a to change the opening / closing timing of the intake valve 8.

  Details of the control contents of the control units 52 to 57 will be described below.

(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 preset in accordance with the engine operating state, for example, the engine speed and the opening / closing timing of the intake valve 8. Is 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, during the reduced cylinder operation, the number of operating cylinders that generate engine output decreases. Therefore, in order to generate the same engine output as during all cylinder operation, the operating cylinders (second, third) The output per cylinder of the cylinders 2B and 2C) needs to be larger than the output per cylinder during all cylinder operation. For this reason, it is necessary to increase the output (generated torque) per cylinder during the reduced-cylinder operation, and accordingly, it is necessary to increase the intake amount (priority efficiency) of each cylinder. In other words, the target value of the intake air amount per cylinder during the reduced cylinder operation is larger than the target value of the intake air amount per cylinder during the all cylinder operation. In order to increase the intake air amount of each cylinder, the pressure in the intake passage 30 (pressure downstream of the throttle valve 34a) needs to be higher than that during all-cylinder operation. Therefore, as a result, at the time of reduced cylinder operation, the throttle valve upstream / downstream pressure ratio becomes closer to 1 than at the time of all cylinder operation, and the opening of the throttle valve 34a at the time of reduced cylinder operation is the opening at the time of all cylinder operation. Is controlled to the larger side (open side).

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

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

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

  When causing the injector 12 to perform fuel injection, the injector control unit 54 determines the injection amount and fuel injection timing according to the operating conditions and issues an instruction to the injector 12. For example, the injector control unit 54 stores a map of preset injection amounts and fuel injection timings for the engine speed and the engine load, and extracts values corresponding to the engine speed and the engine load from this map. At the same time, the extracted value is corrected based on the detected value of the intake air amount sensor SN3 and the like, and the injection amount and the fuel injection timing are determined.

  In the present embodiment, as shown in FIG. 7, the fuel injection timing is basically determined at a timing that is during the intake stroke and is advanced from the intake valve closing timing IVC. Fuel is injected into the inside. FIG. 7 schematically shows fuel injection timing, ignition timing, and opening / closing states of the intake and exhaust valves 8 and 9. In FIG. 7, EX represents the lift curve of the exhaust valve, and IN represents the intake valve. Represents the lift curve.

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

  The intake opening / closing timing control unit 57 determines the opening / closing timing of the intake valve 8 according to the operating conditions (engine speed, engine load, reduced cylinder operation or all cylinder operation, etc.), and this opening / closing timing is realized. Thus, an instruction is issued to the intake variable valve timing mechanism 28a.

(4-2) Control at start of reduced-cylinder operation As described above, in the reduced-cylinder operation, the injector control unit 54 prohibits fuel injection to the idle cylinders (first and fourth cylinders 2A, 2D) and performs injection. The ignition plug control unit 53 prohibits the driving of the ignition plugs 13 of the deactivated cylinders to stop the ignition, and the valve stop mechanism control unit 55 holds the intake and exhaust valves 8 and 9 of the deactivated cylinders closed. However, in this embodiment, these controls are started sequentially instead of simultaneously when the reduced cylinder operation is started.

  Specifically, as shown in FIG. 7, first, the fuel injection stop and the ignition stop are the same cycle (from a predetermined expansion stroke to the next expansion stroke, specifically, 720 ° CA after a predetermined ignition timing. Between). On the other hand, the intake and exhaust valves 8 and 9 are held closed in the next cycle (from the next expansion stroke to the next expansion stroke, specifically, between 720 ° CA after ignition is stopped). Therefore, in the switching start cycle that is a cycle for starting the stop of combustion, the fuel injection is stopped and the ignition is stopped in a state where the intake and exhaust valves 8 and 9 are opened and closed. The intake / exhaust valves 8 and 9 are held closed during 720 ° CA after the start cycle. FIG. 7 shows an example in which the fuel injection timing change control described later is not performed.

(4-3) Preparation Control As described above, in the reduced-cylinder operation, the intake amount per cylinder is increased so that the output per cylinder of the operating cylinder is larger than that in the all-cylinder operation. However, since there is a delay in the change in the intake air amount, the combustion of the deactivated cylinders (first and fourth cylinders 2A, 2D) is stopped immediately after a request for switching from all-cylinder operation to reduced-cylinder operation is performed. If the operation is started, the intake amount of the operating cylinders (the second and third cylinders 2B and 2C) is insufficient, and the engine torque may be reduced, resulting in a torque shock. The preparation control is for avoiding the occurrence of this torque shock, and is started when the operation request determination unit 51 determines that there is a request for switching from all-cylinder operation to reduced-cylinder operation.

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

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

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

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

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

  Here, as described above, in the preparation control, the intake amount per cylinder is increased by the throttle valve control unit 52 to be larger than the intake amount during normal all-cylinder operation. Therefore, when combustion is performed in all the cylinders 2A to 2D in a state where the intake air amount is large in this way, the engine output is the output during normal all-cylinder operation, that is, the engine output immediately before the start of the preparation control, and the driver It will be higher than the engine output required from the etc.

  Therefore, in the present apparatus, during the preparation control, the ignition timing is retarded to a timing at which the increase in engine output caused by the increase in the intake air amount can be suppressed. 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 output 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.

  The above preparation control is performed until it is determined by the reduced-cylinder operation start determination unit 56 that the preparation control is finished and the reduced-cylinder operation is started.

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

(4-4) Control of fuel injection timing during preparatory control As described above, in this embodiment, the fuel injection timing is basically the timing during the intake stroke in which the intake valve 8 is open. Fuel is injected into the combustion chamber 10 with the valve 8 open. Therefore, the fuel injected into the combustion chamber 10 in the previous cycle passes through the intake valve 8 and is pushed out to the intake port 6, and enters the combustion chamber 10 from the intake port 6 in the next cycle (next intake stroke). May re-enter.

  This will be specifically described with reference to FIG. As shown in FIG. 8A, first, when fuel is injected from the injector 12 into the combustion chamber 10, the injected fuel diffuses into the combustion chamber 10. Here, in a state where the piston 11 is lowered and the volume of the combustion chamber 10 is increased, the fuel in the combustion chamber 10 does not flow into the intake port 6 and flows into the combustion chamber 10 even if the intake valve 8 is open. Stay. However, as shown in FIG. 8B, if the intake valve 8 is still open when the piston 11 is raised to some extent after the compression bottom dead center is exceeded by a predetermined amount, the fuel is increased as the piston 11 is raised. The gas in the combustion chamber 10 including a part passes through the intake valve 8 and is pushed out to the intake port 6. When the intake valve 8 is closed in this state, a part of the fuel stays in the intake port 6 as shown in FIG. Then, as shown in FIG. 8D, the fuel remaining in the intake port 6 flows again into the combustion chamber 10 together with air during the intake stroke of the next cycle, that is, when the intake valve 8 is opened.

  As described above, the intake valve closing timing IVC is a timing that is retarded by a predetermined amount from the compression bottom dead center BDC, and the timing at which the gas in the combustion chamber 10 blows back to the intake port 6 as the piston 11 rises. In some cases, a part of the fuel is pushed out to the intake port 6 and flows again into the combustion chamber 10 in the intake stroke of the next cycle. The intake valve closing timing IVC at which the gas in the cylinder blows back to the intake port 6 is a timing when the piston 11 is raised to some extent as described above, and is, for example, about 30 ° CA or more from the compression bottom dead center. It is a retarded time.

  Here, when the fuel is pushed out to the intake port 6 in the cycle before the switching start cycle, combustion occurs from the intake port 6 as the intake valve 8 is opened in the switching start cycle. The fuel will flow again into the chamber 10. However, as described above, the ignition is already stopped in the switching start cycle. Therefore, in this case, the fuel re-entered into the combustion chamber 10 is discharged out of the cylinder through a gap between the cylinder and the piston without burning. That is, a part of the fuel is discharged without being converted into an effective engine output, and the fuel efficiency is deteriorated.

  Therefore, in the present embodiment, when the intake valve closing timing IVC is set to the timing when the gas in the combustion chamber 10 blows back to the intake port 6, the fuel is supplied to the intake port 6 in the cycle before the switching start cycle. Avoid being pushed out.

  Specifically, when the intake valve closing timing IVC is a timing at which the gas in the combustion chamber 10 is blown back to the intake port 6 during the execution of the preparation control, as shown in FIG. The fuel injection timing of the fourth cylinders 2 </ b> A, 2 </ b> D) is set to a timing at which the extrusion of fuel from the combustion chamber 10 to the intake port 6 can be avoided. In the present embodiment, the fuel injection timing of the deactivated cylinders (first and fourth cylinders 2A, 2D) is set to a specific timing that is the most advanced timing among the timings at which the above-described extrusion can be avoided.

  Here, the specific timing is a timing on the advance side of a predetermined amount from the intake valve closing timing IVC, and the intake valve 8 is opened, but the valve opening amount is small, and fuel is injected into the combustion chamber 10. However, it is a time when the fuel can hardly pass through the intake valve 8 and flow into the intake port 6. Therefore, if the fuel injection timing is set to be retarded from the specific timing, it is possible to prevent the fuel from being pushed out from the combustion chamber 10 to the intake port 6 via the intake valve 8. The specific time is set, for example, to a timing that is about 50 ° CA ahead of the intake valve closing timing IVC.

  The fuel injection timing change control is performed by the injector control unit 54. That is, the injector control unit 54 first determines whether or not the intake valve closing timing IVC is a timing when the gas in the combustion chamber 10 blows back to the intake port 6. In the present embodiment, the injector control unit 54 pre-sets and stores the blow-back start valve closing timing IVC0 that is the most advanced timing among the intake valve closing timings IVC at which this blow-back occurs, and the injector control unit 54 Determines whether or not the current intake valve closing timing IVC is behind the blowback start valve closing timing IVC0. Then, when the current intake valve closing timing IVC is on the more retarded side than the blow-back start valve closing timing IVC0, the injector control unit 54 performs the fuel injection timing of the idle cylinders (first and fourth cylinders 2A, 2D). Is changed to the above specific time. The current intake valve closing timing IVC can be specified based on the detection value of the cam angle sensor SN2.

  The procedure for changing the fuel injection timing may be as follows. That is, the operating conditions (engine speed, engine load, etc.) in which the intake valve closing timing IVC is retarded from the reflow start closing valve timing IVC0 and reflow occurs are specified in advance. The fuel injection time may be changed to a specific time. For example, when the intake valve closing timing IVC is stored as a map of the engine speed and the engine load, and the intake valve closing timing IVC is determined according to the engine speed and the engine load, the intake valve closing timing IVC is determined. The fuel injection timing may be changed to a specific timing when IVC is at a predetermined engine speed and engine load that are retarded from the blowback start valve closing timing IVC0. Furthermore, as a map of the fuel injection timing, a normal map and a map in which the fuel injection timing at the predetermined engine speed and engine load is changed to a specific time are set and stored in advance, and these maps are switched. Thus, the fuel injection timing may be changed.

(4-5) Flow of control when switching from all-cylinder operation to reduced-cylinder operation The above-described preparation control flow performed by the ECU 50 will be described with reference to the flowchart of FIG.

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

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

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

  In step S5 following step S4, it is determined whether or not the current intake valve closing timing IVC is retarded from the blowback start valve closing timing IVC0. If this determination is NO, the process proceeds to step S7. On the other hand, when this determination is YES and the intake valve closing timing IVC is retarded from the reblow start valve closing timing IVC0, that is, when the gas in the cylinder containing fuel is pushed out to the intake port 6. Advances to step S6. In step S6, the fuel injection timing is changed to a specific timing. In the present embodiment, as described above, only the fuel injection timing of the deactivated cylinders (first and fourth cylinders 2A and 2D) is changed. As described above, steps S5 and S6 are performed by the injector control unit 54. After step S6, the process proceeds to step S7.

  It should be noted that, as described above, instead of step S5, whether or not the intake valve closing timing IVC is a predetermined operating condition (engine speed, engine load, etc.) that is retarded from the blow-back start valve closing timing IVC0. In the case of this predetermined operating condition, the process may proceed to step S6 to change the fuel injection timing to a specific timing. Further, instead of steps S5 and S6, the map for setting the fuel injection timing is switched to a map in which the fuel injection timing of the predetermined operating condition is changed to a specific timing, and in the case of the predetermined operating condition, A specific time may be extracted as the fuel injection time.

  In step S7, the intake air amount is increased toward the intake air amount during the reduced cylinder operation. In the present embodiment, as described above, the throttle valve control unit 52 changes the opening of the throttle valve 34a to the opening at the time of reduced cylinder operation on the open side rather than at the time of normal full cylinder operation, and thereby the intake air amount Is increased toward the amount during reduced-cylinder operation.

  In step S8, which is the next step after step S7, the ignition timing is retarded from the ignition timing during normal all-cylinder operation. In the present embodiment, as described above, the ignition plug control unit 53 causes the ignition timing to be changed to the normal all-time only at the timing corresponding to the amount of intake increased from the amount of intake during all-cylinder operation (at the start of preparation control). Delayed from the ignition timing during cylinder operation.

  In step S9 following step S8, it is determined whether or not the intake air amount is equal to or greater than the intake air amount during the reduced cylinder operation. If the determination in step S9 is NO, the process returns to step S5, and steps S5 to S8 are repeated until the determination in step S9 is YES. That is, the preparation control for retarding the ignition timing while increasing the intake air amount is continued until the intake air amount becomes equal to or greater than the intake air amount during the reduced-cylinder operation. (Only when the intake valve closing timing IVC is behind the blowback start valve closing timing IVC0) is executed. On the other hand, if the determination in step S9 is YES and the intake air amount has increased beyond the intake air amount during the reduced cylinder operation, the process proceeds to step S10.

  In step S10, reduced-cylinder operation is started. That is, the ignition and fuel injection of the deactivated cylinders (first and fourth cylinders 2A, 2D) are stopped, and the intake and exhaust valves 8, 9 of the deactivated cylinders (first, fourth cylinders 2A, 2D) are stopped in the next cycle. The valve is held closed. In addition, the ignition timing and fuel injection timing of the operating cylinders (second and third cylinders 2B and 2C) are switched to the normal timing of the reduced cylinder operation (the timing near the MBT during the reduced cylinder operation).

(5) Operation, etc. As described above, the intake valve 8 and the exhaust valve 9 are connected in the cycle after the switching start cycle in which the fuel injection and ignition of the idle cylinders (first and fourth cylinders 2A, 2D) are stopped. If the valve is kept closed, in the switching start cycle, the fuel reflows into the cylinder from the intake port 6 together with the opening of the intake valve 8, and this fuel may not be converted into effective engine torque. In addition, the unburned fuel passes through the clearance between the piston and the cylinder, and the exhaust valve 7 is opened when the exhaust valve 9 is opened when returning from the reduced cylinder operation to the all cylinder operation. May be discharged.

  On the other hand, in this embodiment, as described above, the intake valve closing timing IVC is retarded from the blowback start valve closing timing IVC0, and the intake valve closing timing IVC is a timing at which the blowback occurs. In some cases, the fuel injection timing is changed to a specific timing, that is, a time when fuel is not pushed out to the intake port 6, and after this change, a reduced-cylinder operation, that is, fuel injection stop and ignition stop is started. Therefore, as described above, it is possible to avoid that some fuel is not converted into effective engine torque and is discharged to the outside without being burned, and fuel efficiency and exhaust performance can be improved. .

  In the present embodiment, since the preparation control is performed as described above, the intake amount of the operating cylinders (second and third cylinders 2C, 2D) is insufficient at the start of the reduced cylinder operation, and the engine torque is reduced. Can be avoided. In addition, an increase in engine torque accompanying an increase in the intake air amount can be suppressed by retarding the ignition timing, and fluctuations in the engine torque can be suppressed before and after the start of the reduced cylinder operation.

  Here, when the ignition timing is retarded, the fuel efficiency may be lowered. However, in the present embodiment, as described above, fuel efficiency can be improved by suppressing a part of the fuel from being discharged outside the cylinder without being converted into an effective engine output. Therefore, the improvement in the fuel consumption performance can compensate for the reduction in the fuel consumption performance and ensure high fuel consumption performance.

(6) Modification Here, in the above embodiment, the fuel injection timing is changed to a specific timing if the intake valve closing timing IVC is always retarded from the blowback start valve closing timing IVC0 during the execution of the preparation control. However, this control may be performed during the period from the end of the preparation control to the start of the reduced cylinder operation. However, in this case, a cycle for changing the fuel injection timing must be secured between the end cycle of the preparation control and the start cycle (switching start cycle) of the reduced-cylinder operation, and the reduced-cylinder operation can be performed early. May not be able to start, and the fuel efficiency may deteriorate. Therefore, it is preferable to always perform the above control during the execution of the preparation control. Of course, when the end timing of the preparation control, that is, the final cycle for executing the preparation control can be predicted, only in this final cycle or a plurality of cycles including this final cycle (the number of cycles less than the cycle for executing the preparation control). The above-mentioned control only needs to be carried out in (). In this case, the fuel injection timing can be set to an appropriate time according to the operating conditions, and part of the fuel can be prevented from being discharged out of the cylinder without being burned, thereby ensuring high fuel efficiency. be able to. In particular, if the above control is performed only in the final cycle, the engine performance can be kept high by setting the fuel injection timing to an appropriate timing according to the operating conditions.

  The implementation of the preparation control may be omitted. In this case, the fuel injection timing is set to a specific timing in a cycle including at least the cycle immediately before the switching start cycle among the cycles from the request for switching from all-cylinder operation to reduced-cylinder operation to the switching start cycle. Control to be changed (only when the intake valve closing timing IVC is on the more retarded side than the reblow start valve closing timing IVC0) may be performed. At this time, in particular, if this control is performed only in the cycle immediately before the switching start cycle, the fuel injection timing can be set to an appropriate time according to the operating conditions.

  In the above embodiment, the case where the fuel injection timings of the idle cylinders (the first and fourth cylinders 2A and 2D) are changed to the specific timing has been described. However, these fuel injection timings are retarded from the specific timing. You may change at the time. However, if the fuel injection timing is changed to a specific timing which is the most advanced timing of the time when the fuel is pushed out to the intake port 6, the time from the fuel injection timing to the ignition timing is secured, and before the ignition Fuel and air can be mixed well.

  Further, in the above-described embodiment, the case where only the fuel injection timing of the idle cylinders (first and fourth cylinders 2A and 2D) is changed has been described. However, the fuel of the operating cylinders (second and third cylinders 2B and 2C) are simultaneously changed. The injection timing may be changed.

  In the above embodiment, the case where the intake air amount is changed by opening / closing the throttle valve 34a, that is, the case where the intake air amount is increased by changing the throttle valve 34a to the open side in the preparation control has been described. The means for changing (increasing) is not limited to this. For example, the intake air amount may be changed (increased) by changing the intake valve closing timing IVC by the intake variable valve timing mechanism 28a. Further, means capable of changing the valve lift of the intake valve 8 may be used, and the intake air amount may be changed (increased) by changing the valve lift.

  Moreover, although the said embodiment demonstrated the example which applied the control apparatus of this invention to the 4-cylinder gasoline engine, the form of the engine which can apply the control apparatus of this invention is not restricted to this. For example, a multi-cylinder engine other than four cylinders such as 6 cylinders or 8 cylinders may be targeted, and another type of internal combustion engine such as a diesel engine, an ethanol fuel engine, or an LPG engine may be targeted.

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

Claims (4)

A plurality of cylinders having an intake valve that opens and closes an intake port and an exhaust valve that opens and closes an exhaust port, and an all-cylinder operation in which combustion of an air-fuel mixture is performed in all the cylinders; A device for controlling an engine that can be switched between reduced cylinder operation in which combustion in a cylinder is stopped,
Ignition means provided in each cylinder for igniting an air-fuel mixture in these cylinders;
Fuel injection means provided in each cylinder for injecting fuel into these cylinders at a predetermined fuel injection timing;
An intake air amount changing means capable of changing an intake air amount that is an air amount sucked into each cylinder;
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 ignition means, fuel injection means, intake air amount changing means, and valve stop mechanism,
The control means includes
When there is a request to switch from all- cylinder operation to reduced-cylinder operation, the closing timing of the intake valve of the specific cylinder is a timing retarded from the compression bottom dead center, and the gas in the cylinder is in the intake port When it is time to blow back to at least the fuel injection timing in the specific cylinder, it is possible to avoid the uncombusted fuel injected into the cylinder from being pushed out together with the blowback gas from the cylinder into the intake port. Retard at a given time ,
After the control for retarding the fuel injection timing to the predetermined timing is performed on the specific cylinder, the switching cycle is from the first expansion stroke that the specific cylinder reaches after the end of the control to the next expansion stroke. The fuel injection unit and the ignition unit are controlled so that fuel injection and ignition for the specific cylinder are stopped in the switching start cycle, and the specific cylinder is performed in a cycle subsequent to the switching start cycle. An engine control device for driving the valve stop mechanism so that the intake valve and the exhaust valve of the engine are switched to a closed valve holding state . The engine control device according to claim 1,
The control means performs the intake of each cylinder by the intake air amount changing means after a request for switching from full cylinder operation to reduced cylinder operation and before stopping ignition and fuel injection of the specific cylinder. The amount is increased to an intake air amount during reduced cylinder operation that is larger than an intake air amount during normal all cylinder operation for which no switching request has been issued, and the ignition timing of each cylinder is set to an ignition timing during normal all cylinder operation An engine control device that performs preparatory control for retarding the angle. The engine control device according to claim 2,
The control means is configured such that the closing timing of the intake valve of the specific cylinder is a timing retarded from the compression bottom dead center in all cycles during the preparation control, and the gas in the cylinder is A control apparatus for an engine, which performs control for retarding the fuel injection timing to the predetermined timing when it is time to blow back to the intake port. The engine control apparatus according to claim 1 or 2,
When there is a request for switching from all-cylinder operation to reduced-cylinder operation, the control means determines that the closing timing of the intake valve of the specific cylinder is retarded from the compression bottom dead center in the cycle immediately before the switching start cycle. An engine control device that performs control to retard the fuel injection timing to the predetermined timing when the gas in the cylinder is back to the intake port.

Images