JP6485466B2 - Engine evaporative fuel processing device - Google Patents

Description

  Conventionally, evaporative fuel generated in a fuel tank is introduced into an engine body through an intake passage and burned, thereby suppressing the evaporative fuel from being released into the atmosphere. In addition, as one technique for improving fuel efficiency, in a multi-cylinder engine having a plurality of cylinders, combustion in some cylinders is stopped in a predetermined operation region and the intake and exhaust valves of the cylinders are held closed. A technique is known in which operation is performed only with the remaining cylinders in a rest state.

  For example, Patent Document 1 discloses an engine capable of performing all-cylinder operation in which combustion is performed in all cylinders and reduced-cylinder operation in which combustion in some cylinders is stopped, and vaporized fuel generated in a fuel tank. An engine is disclosed that is configured to be introduced into the engine body via an intake passage.

Japanese Patent No. 4317386

  In order to suppress leakage of evaporated fuel from the fuel tank to the atmosphere, it is desirable to introduce more evaporated fuel into the intake passage. However, if the amount of evaporated fuel introduced into the intake passage is increased rapidly, The equivalence ratio of the engine suddenly changes and the engine torque varies. Therefore, it is desirable to gradually increase the amount of evaporated fuel introduced into the intake passage.

  However, if the amount of evaporated fuel is simply increased by a fixed amount, when the amount of air flowing through the intake passage changes, the equivalent ratio of the gas in the intake passage changes accordingly. The equivalent ratio of the gas inside tends to fluctuate. Therefore, in an engine capable of reducing cylinder operation, the amount of evaporated fuel is simply increased by a certain amount as described above when switching between all-cylinder operation and reduced-cylinder operation in which the amount of air flowing through the intake passage changes. When the control is performed, the equivalence ratio of the gas in the cylinder may greatly vary. In addition, since the engine torque is likely to fluctuate with the change in the number of cylinders in which the combustion is performed at the time of switching, the amount of fluctuation in the engine torque may increase due to the fluctuation in the equivalent ratio of the gas in the cylinder.

  The present invention has been made in view of the above circumstances, and in an engine capable of performing all-cylinder operation and reduced-cylinder operation, suppresses leakage of evaporated fuel generated in the fuel tank to the atmosphere. It is another object of the present invention to provide an evaporative fuel processing apparatus that can appropriately control the equivalent ratio of gas in a cylinder.

  In order to solve the above-mentioned problems, the present invention includes an engine body having an intake valve and an exhaust valve and formed with a plurality of cylinders, an intake passage for introducing intake air into the engine body, and a fuel tank for storing fuel. And all-cylinder operation in which combustion of the air-fuel mixture is performed in all cylinders, and reduced-cylinder operation in which combustion in a specific cylinder among a plurality of cylinders is stopped and the specific cylinder is deactivated An evaporative fuel processing device provided in an engine that can be switched between and a purge passage that is connected to the intake passage and introduces purge gas containing evaporated fuel evaporated in the fuel tank into the intake passage; and A purge valve capable of opening and closing the purge passage, and a control means for controlling the purge valve, the control means at the time of performing the purge for introducing the purge gas into the intake passage, An increase control is performed to control the purge valve so that an intake manifold equivalent ratio, which is an equivalent ratio of gas in the intake passage, increases, and based on the amount of air flowing through the intake passage when the increase control is performed. When changing the target intake manifold equivalent ratio, which is the target value of the intake manifold equivalent ratio, and when a switching request for switching the operation between the all cylinder operation and the reduced cylinder operation is issued during the increase control, An evaporative fuel processing device for an engine is provided in which the amount of change in the target intake manifold equivalent ratio based on the amount of air flowing through the intake passage is reduced for a predetermined period after the switching request is issued. ).

  According to the present invention, the purge valve is controlled so as to increase the intake manifold equivalent ratio, whereby it is possible to suppress a sudden change in the equivalent ratio of the gas in the cylinder, and the intake manifold equivalent ratio is a predetermined target value. The purge valve is controlled so that the intake manifold equivalent ratio, that is, the equivalent ratio of the gas before being introduced into the cylinder, can be more reliably set to an appropriate value. For this reason, it is possible to appropriately control the equivalence ratio of the gas in the cylinder to suppress fluctuations in the engine torque.

  In addition, since the target intake manifold equivalent ratio is changed based on the amount of air flowing through the intake passage, it is possible to prevent a sudden change in the equivalent ratio of the gas in the cylinder.

  Specifically, the intake manifold equivalent ratio varies depending on the amount of air flowing through the intake passage in addition to the amount of evaporated fuel introduced into the intake passage. Therefore, if the target intake manifold equivalent ratio is set regardless of the air amount, for example, when the intake manifold equivalent ratio decreases due to the increase in the air amount, the actual intake manifold equivalent ratio and the target intake manifold equivalent ratio And the opening of the purge valve increases rapidly in an attempt to eliminate this difference. Then, the amount of evaporated fuel introduced into the intake passage suddenly increases, and the equivalence ratio of the gas in the intake passage and the cylinder may change suddenly.

  In contrast, in this configuration, since the target intake manifold equivalent ratio is set based on the amount of air flowing through the intake passage as described above, the target intake manifold equivalent ratio is set to a value corresponding to the change in the air amount. And the separation between the target intake manifold equivalent ratio and the actual intake manifold equivalent ratio can be kept small. Accordingly, it is possible to prevent a sudden change in the opening degree of the purge valve and the equivalence ratio of the gas in the cylinder accompanying this deviation.

  However, at the time of switching between all-cylinder operation and reduced-cylinder operation, the amount of change in the amount of air flowing through the intake passage increases. Therefore, at this time, if the target intake manifold equivalent ratio is increased according to the amount of air in the same manner as during normal operation, the change in intake manifold equivalent ratio becomes excessive. In particular, since the equivalence ratio of the gas in the cylinder easily changes greatly due to the change in the air amount in the cylinder accompanying the switching at the time of the switching, the change of the intake manifold equivalent ratio is added to this, so that the equivalent ratio of the gas in the cylinder is increased. As a result, the engine torque may be excessively fluctuated.

  On the other hand, in this configuration, when changing between full cylinder operation and reduced cylinder operation, the amount of change in the target intake manifold equivalent ratio corresponding to the air amount is reduced, so that the gas in the cylinder at the time of switching is reduced. It is possible to suppress an excessive change in the equivalence ratio, and to appropriately control the equivalence ratio of the gas in the cylinder while performing the purge and realizing the switching.

  In the present invention, when a request for switching from all-cylinder operation to reduced-cylinder operation is issued, the control means increases the amount of air introduced into the engine body while performing combustion of the air-fuel mixture in all cylinders. When the preparation control is performed and the reduced-cylinder operation is started after the preparation control is performed, and when a request for switching from the all-cylinder operation to the reduced-cylinder operation is issued during the execution of the increase control, at least the preparation control is performed. It is preferable to reduce the amount of change in the target intake manifold equivalent ratio based on the amount of air flowing through the intake passage during a period during which the intake passage is maintained.

  According to this configuration, it is possible to increase the output of the working cylinder by securing the amount of air introduced into the working cylinder (cylinder in which combustion is performed) at the start of the reduced-cylinder operation by performing the preparation control. It is possible to suppress a decrease in engine torque that accompanies this decrease.

  In addition, since the amount of change in the target intake manifold equivalent ratio based on the amount of air flowing through the intake passage is reduced at least during the execution period of the preparation control, the amount of air flowing through the intake passage is increased by executing the preparation control. On the other hand, it is possible to suppress an excessive change in the intake manifold equivalent ratio and thus the equivalent ratio of the gas in the cylinder with the increase in the air amount.

  Further, in the above configuration, when a request for switching from the reduced cylinder operation to the all cylinder operation is issued, the control means performs a return control for reducing the amount of air introduced into the engine body while starting the all cylinder operation. In addition, when a request for switching from reduced-cylinder operation to all-cylinder operation is issued during the execution of the increase control, the target intake manifold equivalent ratio is changed based on the air amount at least during the period during which the return control is performed. It is preferable to reduce the amount (claim 3).

  According to this configuration, by performing the return control, the amount of air sucked into each cylinder immediately after returning at the time of all cylinder operation can be made smaller than that at the time of reducing cylinder operation. Accordingly, it is possible to suppress an increase in engine torque accompanying an increase in operating cylinders after returning from all-cylinder operation.

  In addition, since the amount of change in the target intake manifold equivalent ratio based on the amount of air flowing through the intake passage is reduced during the period of execution of the return control, the return control is performed to reduce the amount of air flowing through the intake passage. As the air amount decreases, it is possible to suppress an excessive change in the intake manifold equivalent ratio, and hence the equivalent ratio of the gas in the cylinder.

  In the above configuration, the control means estimates the current intake manifold equivalent ratio when the increase control is performed, and increases the intake manifold equivalent ratio based on the most recent change amount of the air amount flowing through the intake passage. After calculating the correction amount, it is preferable to calculate the target intake manifold equivalent ratio by adding the increase correction amount to the estimated intake manifold equivalent ratio.

  According to this configuration, since the target intake manifold equivalent ratio is set based on the current intake manifold equivalent ratio (estimated value) and the most recent change amount of the air amount flowing through the intake passage, the target intake manifold equivalent ratio is set to the air amount. It can be set to an appropriate value according to.

  In the above-described configuration, the control means sequentially increases and decreases to a basic increase correction amount determined in advance so as to increase as the amount of air flowing through the intake passage increases. It is preferable to calculate a value obtained by adding the amount as the increase correction amount.

  In this way, the target intake manifold equivalent ratio and the actual intake manifold equivalent ratio and the equivalent ratio of the gas in the cylinder are controlled to appropriate values according to the air amount itself flowing through the intake passage and the amount of change in the air amount. be able to.

  In the above configuration, the control means sets the successive correction amount to a value greater than 0 when the most recent change amount of the air amount flowing through the intake passage is greater than zero, and the most recent change amount of the air amount is When it is smaller than 0, it is preferable to set the successive correction amount to a value smaller than 0 (Claim 6).

  According to this configuration, even if the amount of air flowing through the intake passage increases with the acceleration of the engine and the like, and the intake manifold equivalent ratio decreases, the increase correction amount is set to a value larger than 0. The ratio can be maintained at a high value, and the increase correction amount is set to a value smaller than 0 even if the air amount decreases as the engine decelerates and the intake manifold equivalent ratio increases. The intake manifold equivalent ratio can be prevented from becoming excessively large with respect to the current intake manifold equivalent ratio, and the target intake manifold equivalent ratio, and the actual intake manifold equivalent ratio and the equivalent ratio of the gas in the cylinder can be appropriately controlled.

  In the above configuration, the control means is configured to reduce the increase correction amount and reduce the increase correction amount when a request for switching between the all cylinder operation and the reduced cylinder operation is issued during the execution of the increase control. It is preferable to reduce the amount of change in the target intake manifold equivalent ratio based on the amount (Claim 7).

  In this way, when the target intake manifold equivalent ratio is calculated by adding the increase correction amount to the current intake manifold equivalent ratio, the intake passage is changed at the time of switching between all-cylinder operation and reduced-cylinder operation with a simple calculation procedure. The amount of change of the target intake manifold equivalent ratio based on the amount of air flowing through the can be reduced.

  In the above-described configuration, when the request for switching between all-cylinder operation and reduced-cylinder operation is issued during the execution of the increase control, the control means issues the change request for the target intake manifold equivalent ratio for the predetermined period. It is preferable to maintain the value before being measured (claim 8).

  In this way, the change amount of the target intake manifold equivalent ratio based on the air amount can be easily reduced when switching between the all cylinder operation and the reduced cylinder operation.

  In the above-described configuration, a fuel injection valve for injecting fuel into the cylinder or the intake passage is provided, and the control means is a reference target fuel that is a target value of a total fuel amount to be supplied to the engine body based on an operating state of the engine body The target maximum purge fuel amount is calculated by subtracting the minimum injection amount of the fuel injection valve that ensures the linearity characteristic of the fuel injection valve from the reference target fuel amount, and at the start of the purge. The increase control is performed until the amount of the evaporated fuel introduced into the engine body through the purge passage reaches the target maximum purge fuel amount, and the evaporated fuel introduced into the engine body through the purge passage It is preferable to control the fuel injection valve so as to inject an amount of fuel obtained by subtracting the amount of fuel from the reference target fuel amount.

  According to this configuration, the reference target fuel amount is realized by fuel supply from the fuel injection valve to the engine body and fuel supply to the engine body by purging while appropriately controlling the equivalence ratio in the cylinder by performing increase control. As a result, the engine torque can be maintained at an appropriate value, and a large amount of evaporated fuel is introduced into the engine body while ensuring the linearity characteristics of the fuel injection valve, preventing leakage of evaporated fuel from the fuel tank to the atmosphere. it can.

  As described above, the equivalent ratio in the cylinder can be appropriately controlled while suppressing the leakage of the evaporated fuel generated in the fuel tank to the atmosphere.

1 is a schematic view of an engine system to which an evaporated fuel processing apparatus for an engine according to an embodiment of the present invention is applied. It is the block diagram which showed the control system of the engine system. It is the figure which showed the operating area | region of the engine. It is the flowchart which showed the control procedure at the time of the switch from all cylinder operation to reduced cylinder operation. It is the graph which showed the time change of each parameter at the time of switching to all cylinder operation and reduction cylinder operation. It is the flowchart which showed the control procedure of the purge valve. It is the flowchart which showed the front | former stage part of the calculation procedure of target purge mass flow rate. It is the flowchart which showed the middle step part of the calculation procedure of target purge mass flow. It is the flowchart which showed the latter part of the calculation procedure of target purge mass flow. It is the figure which showed typically the relationship between air variation | change_quantity, a target intake manifold equivalent ratio, and the present intake manifold equivalent ratio. It is the flowchart which showed the control procedure of the injector. It is the figure which showed the relationship between the injection pulse width and the injection quantity. It is the figure which showed the time change of the intake manifold equivalent ratio at the time of acceleration in this embodiment, and an intake manifold air quantity. It is the figure which showed the time change of the intake manifold equivalent ratio at the time of acceleration in a comparative example, and intake manifold air quantity. It is the figure which showed the time change of the intake manifold equivalent ratio at the time of the deceleration in this embodiment, and an intake manifold air quantity. It is the figure which showed the time change of the intake manifold equivalent ratio at the time of the deceleration in a comparative example, and intake manifold air quantity. It is the graph which showed the time change of each parameter at the time of switching to all cylinder operation and reduction cylinder operation.

(1) Overall Configuration of Engine FIG. 1 is a diagram showing a configuration of an engine system to which an evaporated fuel processing apparatus for an engine according to an embodiment of the present invention is applied. The engine system of the present embodiment includes a four-stroke engine main body 1, an intake passage 30 for introducing combustion air (intake air) into the engine main body 1, and exhaust for discharging exhaust from the engine main body 1 to the outside. A passage 35, a fuel tank 41 for storing fuel, and a purge system 40 for introducing evaporated fuel generated in the fuel tank 41 into the engine body 1 are provided. This engine system is provided in a vehicle, and the engine body 1 is used as a drive source for the vehicle. The engine body 1 is, for example, a four-cylinder engine having four cylinders 2 arranged in a direction orthogonal to the paper surface of FIG. 1, and is a gasoline engine mainly using gasoline as fuel.

  The engine body 1 includes a cylinder block 3 in which a cylinder 2 is formed, a cylinder head 4 provided on the upper surface of the cylinder block 3, and a piston 11 that is inserted into the cylinder 2 so as to be slidable back and forth. Yes. A combustion chamber 5 is formed above the piston 11.

  The piston 11 is connected to the crankshaft 15 via a connecting rod, and the crankshaft 15 rotates around the central axis according to the reciprocating motion of the piston 11. The cylinder block 3 is provided with a rotational speed sensor SN1 that detects the rotational speed of the crankshaft 15 as the rotational speed of the engine.

  The cylinder head 4 is provided with a pair of injectors 12 and spark plugs 13 for igniting a mixture of fuel and air injected from the injectors 12 by spark discharge.

  The injector 12 has a plurality of injection holes serving as fuel injection ports at the tip, and is provided so as to face the combustion chamber 5 of each cylinder 2 from the side on the intake side. A fuel rail 14 for storing fuel is connected to the injector 12 inside. The fuel rail 14 is connected to the fuel tank 41 via a pipe (not shown). The fuel rail 14 stores fuel pumped from the fuel tank 41. The injector 12 receives the supply of fuel stored in the fuel rail 14 and injects the fuel into the cylinder 2.

  The fuel rail 14 is provided with a fuel pressure sensor SN5 for detecting a fuel pressure that is a pressure of fuel stored in the fuel rail 14, that is, a fuel pressure injected by the injector 12.

  The spark plug 13 has an electrode for discharging sparks at the tip, and is provided so as to face the combustion chamber 5 of each cylinder 2 from above.

  The cylinder head 4 includes an intake port 6 for introducing air supplied from the intake passage 30 into the combustion chamber 5 of each cylinder 2, an intake valve 8 that opens and closes the intake port 6, and the combustion chamber 5 of each cylinder 2. Are provided with an exhaust port 7 for leading the exhaust gas generated in step 1 to the exhaust passage 35 and an exhaust valve 9 for opening and closing the exhaust port 7.

  The engine of the present embodiment is a variable cylinder engine capable of a reduced cylinder operation, which is an operation in which two of the four cylinders 2 are stopped without being burned and the remaining two cylinders are operated. During all-cylinder operation in which combustion is performed in all of 2, the ignition by the spark plug is performed in all four cylinders 2, while in reduced-cylinder operation, the ignition operation of the ignition plug 13 is performed in two cylinders whose ignition sequence is not continuous Is prohibited. Hereinafter, the two cylinders that are deactivated during the reduced-cylinder operation are referred to as specific cylinders 2. In some cases, a cylinder in which combustion is stopped is referred to as a non-operating cylinder, and a cylinder in which combustion is performed is referred to as an operating cylinder.

  In the reduced cylinder operation, the fuel injection by the injector 12 of the specific cylinder 2 is also stopped. Further, in the reduced cylinder operation, opening and closing of the intake valve 8 and the exhaust valve 9 of the specific cylinder 2 is prohibited. That is, in the present embodiment, a valve operating mechanism that can prohibit only opening and closing of the intake and exhaust valves 8 and 9 of the specific cylinder 2 is provided. During the reduced cylinder operation, the specific cylinder 2 is operated by this valve operating mechanism. The intake and exhaust valves 8 and 9 are held closed. In addition, as this valve operating mechanism, what is disclosed by patent 2016-44623 can be used, for example.

  The intake passage 30 has a single intake pipe 33 and a plurality of (four) independent intake passages 31 (perpendicular to the plane of FIG. 1) for individually connecting the intake pipe 33 and the intake port 6 of each cylinder 2. Are arranged in the direction). A surge tank 32 having a predetermined volume is provided at the downstream end of the intake pipe 33, and an independent intake passage 31 extends from the surge tank 32 to each intake port 6.

  A throttle valve 34 capable of opening and closing the passage of the intake pipe 33 is provided in a portion upstream of the surge tank 32 in the intake pipe 33.

  An air flow sensor SN2 for detecting a flow rate of air taken into the engine main body 1 through this portion is provided in a portion of the intake pipe 33 upstream of the throttle valve 34. Further, the surge tank 32 is provided with an intake pressure sensor SN3 for detecting the pressure in the surge tank 32, that is, the pressure in the portion of the intake pipe 33 downstream of the throttle valve 34.

  The exhaust passage 35 is provided with a catalyst device 90 containing a catalyst such as a three-way catalyst. Further, the exhaust passage 35 is provided with an A / F sensor SN4 for detecting the air-fuel ratio (ratio of air to fuel) of the exhaust gas, and thus the air-fuel mixture in the combustion chamber 5.

  The purge system 40 includes a canister 42 that detachably adsorbs the evaporated fuel evaporated in the fuel tank 41, a purge air pipe 49 that introduces air into the canister 42, and a purge pipe (purge) that connects the canister 42 and the intake pipe 33. Passage) 43. The purge pipe 43 is connected to a portion of the intake pipe 33 between the throttle valve 34 and the surge tank 32.

  The evaporated fuel adsorbed on the canister 42 is desorbed from the canister 42 by the air introduced from the purge air pipe 49. The evaporated fuel desorbed from the canister 42 is introduced into the intake pipe 33 through the purge pipe 43 together with air. Hereinafter, a gas composed of evaporated fuel and air flowing through the purge pipe 43 is referred to as a purge gas. The evaporated fuel contained in the purge gas is called purge fuel.

  The purge pipe 43 is provided with a purge valve 45 that opens and closes the purge pipe 43. The purge valve 45 is a DUTY control valve, and is opened and closed by changing the DUTY ratio, which is the ratio of the valve opening period to the unit period that combines the valve opening period and the valve closing period. Has been changed. The purge valve 45 is an electromagnetic valve, and the DUTY ratio is a ratio of the energization period to the unit period including one energization period and one non-energization period. The purge valve 45 is fully closed when the DUTY ratio is 0% and fully opened when 100%.

  Hereinafter, opening the purge valve 45 and introducing purge gas into the intake pipe 33 and thus into each cylinder 2 is referred to as purging or executing (implementing) purging.

(2) Control system The control system of an engine system is demonstrated using FIG. The engine system of this embodiment is controlled by a PCM (powertrain control module) 100 mounted on a vehicle. The PCM 100 is a microprocessor including a CPU, a ROM, a RAM, an I / F, and the like, and corresponds to a control unit according to the present invention.

  Information from various sensors is input to the PCM 100. For example, the PCM 100 is electrically connected to the rotation speed sensor SN1, the airflow sensor SN2, the intake pressure sensor SN3, the A / F sensor SN4, and the fuel pressure sensor SN5, and receives input signals from these sensors. Further, the vehicle is provided with an accelerator opening sensor SN6 for detecting the opening of an accelerator pedal (not shown) operated by a driver, a vehicle speed sensor SN7 for detecting a vehicle speed, and the like. The detection signal is also input to the PCM 100. The PCM 100 executes various calculations based on input signals from the sensors (SN1 to SN7, etc.), and drives the injector 12, the purge valve 45 (actuator that drives the purge valve 45), and the throttle valve 34 (drives the throttle valve 34). Control signals by outputting command signals to the actuator).

  The PCM 100 includes an operation region determination unit 102, a spark plug control unit 104, an intake / exhaust valve control unit 106, a throttle valve control unit 108, an injector control unit 110, and a purge valve control unit 112 as functional elements. Each control unit 102, 104, 106, 108, 110, 112 performs a calculation every predetermined time and outputs a signal to each unit.

  The operation region determination unit 102 determines whether the engine is operating in a reduced-cylinder operation region in which reduced-cylinder operation is to be performed or an all-cylinder operation region in which all-cylinder operation is to be performed. In the present embodiment, as shown in FIG. 3, the reduced-cylinder operation region A1 is set in the medium-speed low-load region where the engine speed is N_min or more and N_max or less and the engine load is Tq_min or more and Tq_max or less. The all-cylinder operation region A2 is set in the operation region.

  When the engine operating region is switched from the all-cylinder operating region A2 to the reduced-cylinder operating region A1, the operating region determining unit 102 determines that a request for switching from the all-cylinder operating to the reduced-cylinder operating is issued, and the engine operating region is When the reduced-cylinder operation region A1 is switched to the all-cylinder operation region A2, it is determined that a request for switching from the all-cylinder operation to the reduced-cylinder operation has been issued.

  The intake / exhaust valve control unit 106 changes the opening / closing operation of the intake / exhaust valves 8 and 9 of the specific cylinder 2 during the reduced cylinder operation. The intake / exhaust valve control unit 106 allows the intake / exhaust valves 8 and 9 of all cylinders 2 to be opened and closed during all cylinder operation, while closing the intake and exhaust valves 8 and 9 of the specific cylinder 2 during reduced cylinder operation. Hold.

  The throttle valve control unit 108 controls the opening degree of the throttle valve 34, that is, the amount of air (intake amount) introduced into the engine body 1 (each cylinder 2).

  The spark plug control unit 104 controls the ignition timing of the spark plug 13 and the like. The spark plug control unit 104 drives the spark plugs 13 of all cylinders 2 during all cylinder operation, and stops driving the spark plugs 13 of the specific cylinder 2 during the reduced cylinder operation to ignite the specific cylinder 2. Stop.

  The injector control unit 110 performs calculations related to the injector 12, calculates an injection amount that is the amount of fuel injected from the injector 12 into the cylinder 2, and outputs a signal corresponding to the injection amount to the injector 12. The injector control unit 110 drives the injectors 12 of all the cylinders 2 during all-cylinder operation, and stops the fuel injection of the specific cylinders 2 by stopping driving the injectors 12 of the specific cylinder 2 during the reduced-cylinder operation.

  The purge valve control unit 112 performs an operation related to the purge valve 45, calculates a command value for the DUTY ratio of the purge valve 45 (hereinafter, appropriately referred to as a purge valve command DUTY ratio), and outputs a signal corresponding thereto to the purge valve 45.

(2-1) Control at the time of switching between all-cylinder operation and reduced-cylinder operation The control at the time of switching between all-cylinder operation and reduced-cylinder operation will be described.

(I) Control at the time of switching from all-cylinder operation to reduced-cylinder operation In the reduced-cylinder operation, the number of cylinders 2 in which combustion is performed is smaller than that during all-cylinder operation. As a result, it is necessary to make the amount of air (intake amount) introduced per cylinder 2 of the operating cylinder 2 larger than that during all-cylinder operation. However, since there is a delay in the change in the intake air amount, if the intake air amount is increased while starting the reduced cylinder operation immediately after the request for switching from the all cylinder operation to the reduced cylinder operation is issued, There is a risk that the engine torque will drop due to insufficient intake air and a torque shock will occur.

  Therefore, in the present embodiment, preparation control for avoiding the torque shock is performed when switching from all-cylinder operation to reduced-cylinder operation.

  In the preparation control, the intake air amount introduced into the entire engine body 1 and the intake air amount per cylinder 2 are set at the same operating conditions (engine speed, engine load, etc.) except when switching between full cylinder operation and reduced cylinder operation. More than the normal all-cylinder operation. Specifically, the throttle valve control unit 108 changes the opening of the throttle valve 34 to the opening side from the opening at the time of normal all-cylinder operation, that is, the opening just before the switching request is issued.

  Here, when the intake amount per cylinder 2 is increased while combustion is being performed in all the cylinders 2 in this way, the engine torque is the torque during normal all-cylinder operation and is required by the driver or the like. It will be higher than.

  Therefore, in the preparation control, the ignition plug control unit 104 changes the ignition timing to a timing retarded from the ignition timing during normal all-cylinder operation so as to cancel the increase in engine torque accompanying the increase in intake air amount. .

  In this preparatory control, the intake amount per cylinder 2 is the intake amount per cylinder 2 during normal reduced cylinder operation (intake required during normal reduced cylinder operation except when switching between full cylinder operation and reduced cylinder operation). It ends when it reaches (amount). Then, the reduced-cylinder operation is started after completion of the preparation control.

  FIG. 4 is a flowchart showing a control flow when switching from all-cylinder operation to reduced-cylinder operation performed by the PCM 100.

  First, in step S101, the PCM 100 (operation region determination unit 102) determines whether or not there is a request for switching from all-cylinder operation to reduced-cylinder operation.

  When the determination in step S101 is NO and there is no request for switching to the reduced cylinder operation, the process proceeds to step S10 and the all cylinder operation is maintained. On the other hand, when the determination in step S101 is YES and a request for switching to reduced cylinder operation is issued, the process proceeds to step S103.

  In step S103, the opening degree of the throttle valve 34 is changed to the opening side with respect to the opening degree during normal all-cylinder operation. Next, in step S104, the ignition timing is set to the retard side with respect to the timing during normal all-cylinder operation.

  Next, in step S105, it is determined whether or not the intake air amount per cylinder 2 has reached the intake air amount per cylinder 2 during normal reduced-cylinder operation. If the determination in step S105 is yes, the process proceeds to step S106. On the other hand, if the determination in step S105 is NO and the intake air amount per cylinder 2 has not reached the intake air amount per cylinder 2 during normal reduced-cylinder operation, the process returns to step S101, and steps S101 to S101 are performed. Step S105 is repeated.

  In step S106 which proceeds with the determination in step S105 being YES, reduced-cylinder operation is started. That is, the ignition and fuel injection in the specific cylinder 2 are stopped, the intake / exhaust valves 8 and 9 of the specific cylinder 2 are held closed, and the ignition timing of the working cylinder 2 is set to the timing at the time of normal cylinder reduction operation. To do.

(Ii) Control when returning from reduced-cylinder operation to full-cylinder operation Unlike the switching from full-cylinder operation to reduced-cylinder operation described above, when switching from reduced-cylinder operation to full-cylinder operation, that is, switching to all-cylinder operation. When returning, all-cylinder operation is started immediately after a request to return to all-cylinder operation (request to switch from reduced-cylinder operation to all-cylinder operation) is issued. That is, as soon as the return request to the all-cylinder operation is issued, the PCM 100 cancels the prohibition of ignition in the specific cylinder 2, cancels the prohibition of fuel injection, and the intake and exhaust valves 8 and 9 of the specific cylinder 2. Release the closed valve.

  Here, as described above, in the reduced-cylinder operation, the intake amount per cylinder 2 is made larger than that in the normal all-cylinder operation. Therefore, it is necessary to reduce the intake amount per cylinder 2 when returning from the reduced cylinder operation to the all cylinder operation. However, as described above, there is a delay in the change in the intake air amount. Therefore, immediately after returning to the all-cylinder operation, the intake amount of each cylinder 2 becomes larger than the amount during normal all-cylinder operation, and the engine torque becomes excessive, which may cause a torque shock.

  Therefore, in the present embodiment, when returning to the all-cylinder operation, while performing the all-cylinder operation in which combustion is performed in all the cylinders 2, the intake amount introduced into the entire engine body 1 is reduced, and the engine torque is reduced. Return control is performed to retard the ignition timing so as to cancel out the excess. Specifically, when there is a request to return to all-cylinder operation, the throttle valve control unit 108 changes the opening of the throttle valve 34 closer to the closing side than the opening during the reduced-cylinder operation, and the spark plug control unit 104 The ignition timing is changed to the retarded side with respect to the normal all-cylinder operation timing.

  FIG. 5 shows changes in parameters when switching between all-cylinder operation and reduced-cylinder operation. FIG. 5 shows a state where a request for switching to the reduced cylinder operation is issued at time t1 and a return request for the all cylinder operation is issued at time t10 in a state where the all cylinder operation is being performed. ing.

  As shown in FIG. 5, when a request for switching to reduced cylinder operation is issued at time t1, preparation control is started, the number of operating cylinders 2 is maintained at four, and all cylinder operation is maintained while the throttle is maintained. The valve 34 is controlled to open. As a result, the total intake amount in FIG. 5 and the intake amount introduced into the entire engine body 1 increases. The ignition timing is retarded as the intake air amount increases. As a result, the charging efficiency, that is, the intake amount per cylinder 2 is increased in a state where fluctuations in the engine torque are substantially suppressed. Thereafter, when the charging efficiency reaches the charging efficiency in the reduced-cylinder operation at time t2, the preparation control is finished, the number of operating cylinders 2 is reduced to two, and the reduced-cylinder operation is started. Here, as shown in FIG. 5, when the reduced-cylinder operation is started, the total intake air amount is reduced toward a value substantially the same as the value immediately before time t1. Hereinafter, the intake air amount introduced into the entire engine body 1 may be simply referred to as a total intake air amount.

  Further, as shown in FIG. 5, when a return request to all cylinder operation is issued at time t10, the number of operating cylinders 2 is immediately set to four and all cylinder operation is started. At the same time when the return request is issued, the return control is started, the throttle valve 34 is controlled to the closed side, and the ignition timing is retarded from that during normal all-cylinder operation. As a result, the total intake amount increases immediately after returning to the all-cylinder operation at time t10, but the total intake amount thereafter decreases toward the value during normal all-cylinder operation. After that, at time t11, the opening of the throttle valve 34 is reduced to the opening at the time of normal all-cylinder operation, and then the total intake amount reaches the value at the time of normal all-cylinder operation at time t12 (one cylinder). When the intake air amount per 2 reaches the normal intake air amount), the retard control of the ignition timing is stopped and the return control is finished. And it becomes normal all-cylinder operation.

(2-2) Purge Valve Control Procedure Next, the purge valve 45 control procedure will be described with reference to FIGS.

  As shown in FIG. 6, the PCM 100 first reads detection values of the sensors SN1 to SN7 and the like in step S1.

  Next, in step S2, a target intake air amount is calculated. The target intake air amount is a mass flow rate of air to be supplied to the engine body 1 (specifically, to be supplied to each cylinder 2). The PCM 100 calculates a required torque, which is a torque required for the engine body 1 based on the accelerator opening, the vehicle speed, and the like, and calculates the charging efficiency of the cylinder 2 necessary for realizing the required torque. The target intake air amount is calculated on the basis of the charging efficiency and the engine speed.

  Next, in step S3, a cylinder required fuel amount (reference target fuel amount) Qcyl is calculated based on the operating state of the engine body. The cylinder required fuel amount Qcyl is a total amount of fuel to be supplied to the engine body 1 (specifically, to be supplied to each cylinder 2). The PCM 100 calculates the required cylinder fuel amount Qcyl based on the charging efficiency calculated as described above, the engine speed, and the like.

  Next, in step S4, it is determined whether or not a purge execution condition that is an operation condition for executing the purge is satisfied. For example, when the fuel is cut, it is determined that the purge execution condition is not satisfied.

  If the determination in step S4 is NO and the purge execution condition is not satisfied, the process proceeds to step S5 to stop the purge, and is the target value of the volume flow rate of the purge gas introduced into the engine body 1 (each cylinder 2). The target purge volume flow rate is set to 0, and the process proceeds to step S10.

  On the other hand, if the determination in step S4 is YES and the purge execution condition is satisfied, the process proceeds to step S6.

  In step S6, a minimum injection amount Qinj_min is set. The minimum injection amount Qinj_min is a minimum value of the injection amount of the injector 12 that ensures the linearity characteristic of the injector 12. Specifically, under a condition where the fuel pressure is constant, the injection amount of the injector 12 basically increases or decreases in proportion to the command value. However, as shown in FIG. 12 in which the horizontal axis is the injection period corresponding to the injection pulse width, that is, the injection amount command value, and the vertical axis is the actual injection amount, the injection amount and the injection are in the region B1 where the injection amount is less than the predetermined amount. The injection amount is proportional to the injection pulse width only in the region B2 where the injection amount is not less than the predetermined amount, and the minimum injection amount Qinj_min is this predetermined amount.

  Here, the minimum injection amount Qinj_min varies depending on the fuel pressure. Therefore, in step S6, the minimum injection amount Qinj_min is set based on the fuel pressure. In this embodiment, the relationship between the fuel pressure and the minimum injection amount Qinj_min is obtained in advance in an experiment or the like in the PCM 100 and stored in a table. Extracted as Qinj_min.

  Next, in step S7, a target maximum purge fuel amount Qcharge_max is calculated. The target maximum purge fuel amount Qcharge_max is a purge fuel amount that can be supplied to the engine body 1 (each cylinder 2) while ensuring the linearity characteristics of the injector 12 and with the output torque of the engine body 1 being the required torque. This is the maximum value, and is calculated by subtracting the minimum injection amount Qinj_min from the cylinder required fuel amount Qcyl.

  Next, in step S8, the target purge mass flow rate is calculated while using the target maximum purge fuel amount Qcharge_max.

  7 to 9 are flowcharts showing the calculation procedure of the target purge mass flow rate.

  As shown in FIG. 7, first, in step S21, the PCM 100 calculates a target maximum intake manifold equivalent ratio based on the target maximum purge fuel amount Qcharge_max and the like. The intake manifold equivalent ratio is the equivalent ratio of the gas in the intake passage 30 and is the equivalent ratio of the mixed gas of the air introduced into the intake passage 30 from the outside of the engine system and the purge gas introduced into the intake passage 30 from the purge pipe 43. It is. Specifically, the intake manifold equivalent ratio is an equivalent ratio of the gas in the intake pipe 33 immediately before being introduced into the cylinder 2. The target maximum intake manifold equivalent ratio is an intake manifold equivalent ratio that is estimated to be realized when the purge fuel corresponding to the target maximum purge fuel amount Qcharge_max is introduced into the intake pipe 33.

  Specifically, the PCM 100 is necessary to introduce the purge fuel corresponding to the target maximum purge fuel amount Qpurge_max into the intake pipe 33 from the target maximum purge fuel amount Qpurge_max and the purge gas fuel concentration (hereinafter referred to as purge gas concentration). The purge gas mass flow rate is calculated, and the target maximum intake manifold equivalent ratio is calculated from the gas amount obtained by combining the purge gas mass flow rate and the air mass flow rate detected by the air flow sensor SN2 and the target maximum purge fuel amount Qpurge_max. . The procedure for calculating the purge gas concentration will be described later.

  In the present embodiment, when the execution of the purge is started, the intake manifold equivalent ratio is configured to increase toward the target maximum intake manifold equivalent ratio, and the target intake manifold equivalent ratio that is a target value at each time of the intake manifold equivalent ratio is configured. Is gradually increased toward the target maximum intake manifold equivalent ratio. As described above, the purge valve control unit 112 performs calculation every predetermined time, and calculates the target intake manifold equivalent ratio every time.

  In step S22, the current value of the intake manifold air amount (i), which is the amount of air in the intake pipe 33, specifically, the amount of air in the intake pipe 33 immediately before being introduced into the cylinder 2 is estimated. To do.

  In the present embodiment, the current intake manifold air amount (i) is estimated using the detection value of the intake pressure sensor SN3, the detection value of the airflow sensor SN2, and the like. Here, i is a counter indicating the number of operation cycles. After step S22, the process proceeds to step 23.

  In step S23, an air change amount ΔQa (i) that is a change amount of the intake manifold air amount is calculated. Specifically, a value obtained by subtracting the previous intake manifold air amount (i−1), that is, the intake manifold air amount calculated one calculation cycle before, from the intake manifold air amount (i) calculated in step S22 is an air change amount ΔQa. (I).

  Next, in step S24, the current intake manifold equivalent ratio (i) is estimated.

  In the present embodiment, the current intake manifold equivalent is calculated using the current intake manifold air amount (i) calculated in step S22, the purge gas concentration, the mass flow rate of the purge gas calculated based on the DUTY ratio of the purge valve 45 as will be described later, and the like. Estimate the ratio (i).

  Next, in step S25, it is determined whether or not switching from all-cylinder operation to reduced-cylinder operation is in progress. Specifically, in step S25, after the preparation control is started in response to a request for switching from all-cylinder operation to reduced-cylinder operation, the intake manifold air amount is reduced to the air amount during normal reduced-cylinder operation. It is determined whether or not it is a period until the time t1, that is, whether or not it is a period from time t1 to time t3 in FIG.

  If the determination in step S25 is yes and the process is in the middle of switching from all-cylinder operation to reduced-cylinder operation, the process proceeds to step S26. On the other hand, if the determination in step S25 is no, the process proceeds to step S27.

  In step S27, it is determined whether or not the process is returning from the reduced cylinder operation to the all cylinder operation. Specifically, in step S27, a period from when the return control is started in response to the request for return to all cylinder operation until the intake manifold air amount decreases to the air amount during normal all cylinder operation. Whether it is a period from time t10 to time t12 in FIG.

  If the determination in step S27 is YES and the process is returning from the reduced cylinder operation to the all cylinder operation, the process proceeds to step S26. On the other hand, if the determination in step S27 is no, the process proceeds to step S28 shown in FIG.

  In step S26, the target intake manifold equivalent ratio (i) is set to the previous target intake manifold equivalent ratio (i-1). That is, the target intake manifold equivalent ratio (i) is maintained at a value immediately before steps S25 and S27 and immediately before a switching request is issued. After step S26, the process proceeds to step S35 shown in FIG.

  On the other hand, in step S28 that proceeds when the determination in step S27 is NO, a basic increase correction amount F (i) used for calculating the target intake manifold equivalent ratio (i) is calculated as described later. The basic increase correction amount F (i) is calculated to a value larger than zero. The basic increase correction amount F (i) is calculated based on the current intake manifold air amount (i), and is set to a larger value as the current intake manifold air amount (i) is larger.

  Next, in step S29, it is determined whether or not the air change amount ΔQa (i) calculated in step S28 is zero. That is, it is determined whether the engine operating state is in a steady state and the intake manifold air amount is maintained at a constant value. In step S29, it is not necessary to determine whether or not the air change amount ΔQa (i) is strictly 0, and whether or not the air change amount ΔQa (i) is substantially 0, that is, What is necessary is just to determine whether the air quantity of intake manifold has not changed substantially. Therefore, for example, in step S29, it may be determined whether or not the absolute value of the air change amount ΔQa (i) is smaller than a predetermined value greater than zero.

  If the determination in step S29 is YES and the air change amount ΔQa (i) is 0 and the intake air amount is kept constant, the process proceeds to step S30.

  In step S30, a value obtained by adding the basic increase correction amount F (i) calculated in step S28 to the current intake manifold equivalent ratio (i) calculated in step S24 is set as the target intake manifold equivalent ratio (i). After step S30, the process proceeds to step S35.

  On the other hand, if the determination in step S29 is NO and the air change amount ΔQa (i) is not 0 but the intake air amount has changed, the process proceeds to step S31. For example, when the vehicle and the engine are accelerated, the intake air amount increases and the air change amount ΔQa (i) becomes a value larger than 0, and the determination in step S29 is NO. Further, when the vehicle and the engine are decelerated, the intake air amount decreases, and the air change amount ΔQa (i) becomes a value smaller than 0, and the determination in step S29 becomes NO.

  In step S31, as will be described later, a sequential correction amount G (i) used for calculating the target intake manifold equivalent ratio (i) is calculated based on the air change amount ΔQa (i). When the air change amount ΔQa (i) is larger than 0, the sequential correction amount G (i) is also set to a value larger than 0, and when the air change amount ΔQa (i) is smaller than 0, the sequential change amount G (i) is sequentially set. The correction amount G (i) is also set to a value smaller than 0. The successive correction amount G (i) is set to a larger value as the air change amount ΔQa (i) is larger. For example, the successive correction amount G (i) is calculated by multiplying the air change amount ΔQa (i) by a predetermined coefficient (> 0).

  After step S31, the process proceeds to step S32. In step S32, a value obtained by adding the basic increase correction amount F (i) and the sequential correction amount G (i) to the current intake manifold equivalent ratio (i) is set as the target intake manifold equivalent ratio (i).

  After step S32, the process proceeds to step S33. In step S33, it is determined whether or not the target intake manifold equivalent ratio (i) calculated in step S32 is smaller than the previous target intake manifold equivalent ratio (i-1). If the determination in step S33 is no, the process proceeds to step S35.

  On the other hand, when the determination in step S32 is YES and the target intake manifold equivalent ratio (i) is smaller than the previous target intake manifold equivalent ratio (i-1), the process proceeds to step S34. In step S34, the target intake manifold equivalent ratio (i) is maintained at the previous target intake manifold equivalent ratio (i-1), and the process proceeds to step S35.

  As shown in FIG. 9, in step S35, it is determined whether or not the target intake manifold equivalent ratio (i) calculated as described above is equal to or greater than the target maximum intake manifold equivalent ratio calculated in step S21.

  If the determination in step S35 is NO and the target intake manifold equivalent ratio (i) is less than the target maximum intake manifold equivalent ratio, the process proceeds to step S37.

  On the other hand, if the determination in step S35 is YES and the target intake manifold equivalent ratio (i) is greater than or equal to the target maximum intake manifold equivalent ratio, the process proceeds to step S36. In step S36, the target intake manifold equivalent ratio (i) is set to the target maximum intake manifold equivalent ratio (i). After step S36, the process proceeds to step S37.

  In step S37, the target purge mass flow rate is calculated based on the target intake manifold equivalent ratio (i). The target purge mass flow rate (i) is the mass flow rate of the purge gas necessary for realizing the target intake manifold equivalent ratio (i). The target intake manifold equivalent ratio (i), the air flow rate detected by the air flow meter, the purge gas concentration, etc. Based on the above. After step S37, the process proceeds to step S9 shown in FIG.

  In step S9, the target purge volume flow rate (i) is calculated by converting the target purge mass flow rate (i) into the volume flow rate based on the temperature and pressure of the purge gas. In the present embodiment, the temperature and pressure of the purge gas are atmospheric temperature and pressure.

  After step S9, the process proceeds to step S10, and the purge valve command DUTY ratio is calculated based on the target purge volume flow rate (i).

  In this embodiment, the differential pressure across the purge valve 45 is calculated, and the purge valve command DUTY ratio is determined based on this differential pressure and the target purge volume flow rate.

  Specifically, the pressure loss of the purge pipe 43 is calculated, and the value obtained by subtracting this pressure loss from the atmospheric pressure is set as the pressure upstream of the purge valve 45 of the purge pipe 43, and the intake pressure detected by the intake pressure sensor SN3. Is the pressure downstream of the purge valve 45, and the differential pressure across the purge valve 45 is calculated. Further, the relationship between the differential pressure, the volume flow rate of the purge gas, and the DUTY ratio of the purge valve is preliminarily set as a map by experiments or the like and stored in the PCM 100. The DUTY ratio corresponding to the pressure and the target purge volume flow rate is extracted and determined as the purge valve command DUTY ratio.

  As described above, when the determination in step S4 is NO and the process proceeds to step S5 and the target purge volume flow rate is set to 0, the purge valve command DUTY ratio is 0%.

  After step S10, the process proceeds to step S11. In step S11, the purge valve command DUTY ratio signal set in step S10 is output to the purge valve 45.

  In this way, in this embodiment, when the purge is started, the target intake manifold equivalent ratio, and thus the intake manifold equivalent ratio, is increased toward the target maximum intake manifold equivalent ratio. When the increase control for increasing the intake manifold equivalent ratio is performed, the total value of the basic increase correction amount F calculated based on the current intake manifold air amount and the sequential correction amount G calculated based on the air change amount ΔQa. Is added to the current intake manifold equivalent ratio, and the value is set as the target intake manifold equivalent ratio. Further, the target intake manifold equivalent ratio (i) is maintained to be equal to or higher than the previous target intake manifold equivalent ratio (i-1).

  FIG. 10 is a schematic diagram showing the relationship between the air change amount ΔQa, the target intake manifold equivalent ratio s, and the current intake manifold equivalent ratio u. As shown in FIG. 7, when the air change amount ΔQa is 0, the target intake manifold equivalent ratio s is set to a value larger by the basic increase correction amount F than the current intake manifold equivalent ratio u. When the air change amount ΔQa is larger than 0, that is, when the intake manifold air amount is increasing at the time of acceleration or the like, the target intake manifold equivalent ratio s is calculated from the current intake manifold equivalent ratio u by the basic increase correction amount. After increasing by F, the value is successively increased by the correction amount G. On the other hand, when the air change amount ΔQa is smaller than 0, that is, at the time of deceleration or the like, and the intake manifold air amount is decreasing, the target intake manifold equivalent ratio s is changed from the current intake manifold equivalent ratio u to the basic increase correction amount. The value is obtained by subtracting the absolute value of the correction amount G from the value that is larger by F.

  By controlling the purge valve 45 as described above, as shown in FIG. 5, the target intake manifold equivalent ratio and the intake manifold equivalent ratio are gradually increased until the preparation control is started at time t1. The amount of purge fuel introduced into the intake pipe 33 is gradually increased from time t1. On the other hand, during the period from time t1 to time t3 and during the switching from all-cylinder operation to reduced-cylinder operation, the target intake manifold equivalent ratio is maintained at the previous value, that is, the value immediately before the start of the preparation control. Is maintained at the value immediately before the start of the preparation control. As shown in FIG. 5, the intake manifold equivalent ratio is maintained constant. As described above, during the period from time t1 to time t3, the preparation control and the switching from all-cylinder operation to reduced-cylinder operation are performed. Since the total intake air amount and therefore the intake manifold air amount increase or decrease, the purge fuel amount, which is the amount of purge fuel introduced into the intake pipe 33, changes.

  Similarly, the target intake manifold equivalent ratio and the intake manifold equivalent ratio are maintained at values immediately before the start of the return control during the period from time t10 to time t12 and during the return to the all-cylinder operation. Further, the intake manifold equivalent ratio is kept constant from time t10 to time t12, but the purge fuel amount changes as the intake manifold air amount changes.

(2-3) Injector Control Procedure Next, a procedure for calculating the injection amount of the injector 12 (command injection amount that is a command value of the injection amount of the injector 12) will be described with reference to FIG.

  First, in step S41, the PCM 100 reads the cylinder required fuel amount Qcyl calculated in step S3, the purge valve command DUTY ratio set in step S10, and the like.

  Next, in step S42, an actual purge volume flow rate that is the current value of the volume flow rate of the purge gas introduced into the engine body 1 is estimated.

  Specifically, after calculating the volume flow rate of the basic purge gas based on the current DUTY ratio of the purge valve 45 and the differential pressure across the purge valve 45 calculated in the calculation process of step S10, The volume flow rate of the purge gas is estimated by correcting the voltage supplied to 45, the drive frequency of the purge valve 45, and the temperature around the purge valve 45.

  Next, in step S43, the actual purge volume flow rate calculated in step S42 is converted into a mass flow rate to calculate the actual purge mass flow rate.

  Next, in step S44, an actual purge fuel amount Qcharge_r that is the amount of purge fuel currently introduced into the engine body 1 is estimated. Specifically, the actual purge fuel amount Qcharge_r is calculated based on the actual purge mass flow rate and the purge gas concentration calculated in step S43.

  Next, in step S45, a value obtained by subtracting the actual purge fuel amount Qpurge_r from the cylinder required fuel amount Qcyl is calculated as the basic injection amount.

  Next, in step S46, the basic injection amount is A / F_feedback corrected to calculate a command injection amount. That is, in the present embodiment, the injection amount of the injector 12 is corrected so that the actual air-fuel ratio of the gas in the exhaust passage 35 detected by the A / F sensor SN4 becomes a preset target value. The basic injection amount is corrected with this correction amount.

  After step S46, the process proceeds to step S47, and the command injection amount calculated in step S46 is injected to the injector 12.

  As described above, in the present embodiment, the injection amount of the injector 12 is basically set to an amount obtained by subtracting the actual purge fuel amount Qpurge_r, that is, the amount of purge fuel introduced into the engine body 1 from the required cylinder fuel amount Qcyl. The

(2-4) Purge concentration estimation procedure Next, a purge gas concentration estimation procedure will be described.

  In the present embodiment, the purge gas concentration is estimated based on the air-fuel ratio of the gas in the exhaust passage 35 detected by the A / F sensor SN4 under the predetermined operating condition in which the purge is executed. Specifically, the deviation between the preset target value of the air-fuel ratio of the exhaust passage 35 and the actual air-fuel ratio detected by the A / F sensor SN4 is caused by supplying the purge fuel to the engine body 1. If it occurs, the purge gas concentration is estimated on the basis of the deviation amount and the mass flow rate of the purge gas. In the present embodiment, the average value of the deviation amount and the average value of the flow rate of the purge gas are calculated under the predetermined operating conditions, and the purge gas concentration is estimated using these values.

(3) Operation, etc. As described above, in the present embodiment, at the start of purge, the target intake manifold equivalent ratio, and thus the intake manifold equivalent ratio, gradually increases toward the target maximum intake manifold equivalent ratio. As a result, the opening degree of the purge valve 45 is changed. Therefore, it is possible to suppress sudden changes in the intake manifold equivalent ratio and the equivalent ratio of the gas in the cylinder 2 due to the start of the purge. Further, the purge valve 45 is controlled so that the intake manifold equivalent ratio becomes a predetermined target value, and the intake manifold equivalent ratio, that is, the equivalent ratio of the gas before being introduced into the cylinder can be more reliably set to an appropriate value. The equivalence ratio of the gas before combustion in the cylinder 2 can be appropriately controlled. Therefore, engine torque and exhaust gas performance can be improved.

  In addition, during normal operation except when switching between all-cylinder operation and reduced-cylinder operation, the air change amount ΔQa that is the change amount of the intake manifold air amount, that is, the sequential amount calculated based on the change amount of the air amount in the intake pipe 33 The target intake manifold equivalent ratio is calculated by adding the current intake manifold equivalent ratio to the increase correction amount obtained by combining the correction amount G and the basic increase correction amount F calculated based on the intake manifold air amount. Therefore, it is possible to reduce the amount of evaporated fuel remaining in the fuel tank earlier by introducing more purge gas into the intake pipe 33 while suppressing a sudden change in the intake manifold equivalent ratio and the equivalent ratio of the gas in the cylinder. .

  Specifically, as described above, the equivalent ratio of the gas in the cylinder can be appropriately controlled by controlling the purge valve so that the intake manifold equivalent ratio becomes a predetermined target value. However, for example, when the opening degree of the purge valve is changed so that the intake manifold equivalent ratio is simply increased from the current intake manifold equivalent ratio by a predetermined value regardless of the air change amount ΔQa and the intake manifold air amount. When the intake manifold air amount changes during acceleration / deceleration or the like, the opening of the purge valve is changed without taking into account the change in intake manifold equivalent ratio caused by the change in intake manifold air amount. For this reason, the amount of purge fuel introduced into the intake pipe 33 becomes excessive and the fluctuation of the equivalent ratio of the gas in the cylinder 2 becomes large, or the amount of purge fuel introduced into the intake pipe 33 becomes too small. There is a possibility that the amount of evaporated fuel remaining in the fuel tank 41 cannot be reduced sufficiently.

  This will be described in detail with reference to FIGS. FIGS. 13 and 14 show the target intake manifold equivalent ratio and intake manifold equivalent ratio (actual intake manifold equivalent ratio, hereinafter referred to as actual intake manifold equivalent ratio) when the intake manifold air amount is increased, for example, during engine acceleration. The time change of intake manifold air quantity is shown typically. FIG. 15 and FIG. 16 schematically show these temporal changes when the intake manifold air amount is reduced during deceleration or the like. FIGS. 13 and 15 are diagrams when the control according to the present embodiment is performed, and FIGS. 13 and 16 are comparative examples. As described above, the intake manifold equivalent ratio is simply changed to the current intake manifold equivalent. It is a figure when the opening degree of a purge valve is changed so that it may increase only a fixed value from ratio (actual intake manifold equivalent ratio).

  As shown in FIGS. 13 and 14, until the intake air amount starts to increase with acceleration at time t <b> 3, the actual intake manifold equivalent ratio is substantially controlled to the previously calculated target intake manifold equivalent ratio by changing the opening of the purge valve 45. Is done. For example, in the comparative example shown in FIG. 14, when the target intake manifold equivalent ratio P (t21) is set to a predetermined value at time t1, the opening of the purge valve 45 is changed so as to realize this. At t22, the actual intake manifold equivalent ratio Q (t22) is set to the predetermined value. Until the time t23, the target intake manifold equivalent ratio P and the actual intake manifold equivalent ratio Q are appropriately increased. However, when the increase in intake air amount starts at time t23, the actual intake manifold equivalent ratio Q (t24) does not reach the target intake manifold equivalent ratio P (t23) at time t24. The amount of increase in equivalence ratio is kept small.

  Here, in the comparative example, as described above, the target intake manifold equivalent ratio P is set to a value obtained by adding a constant value α to the actual intake manifold equivalent ratio Q, and the target intake manifold equivalent calculated at time t24 is set. The intake manifold equivalent ratio to be realized at time t5 with the ratio P (t24) is a value obtained by adding a constant value α to the actual intake manifold equivalent ratio Q (t24) at time t24. That is, in the comparative example, the increase amount of the target intake manifold equivalent ratio P between the time t24 and the time t23 is substantially equal to the increase amount of the actual intake manifold equivalent ratio Q between the time t24 and the time t32. Be controlled. Therefore, as described above, when the increase amount of the actual intake manifold equivalent ratio Q from time t23 is suppressed to be small at time t24, the increase amount of the target intake manifold equivalent ratio P is similarly reduced and is calculated at time t24. The target intake manifold equivalent ratio P (t24) is kept small. This also occurs after time t24 (during the period when the intake manifold air amount is increasing). Therefore, in the comparative example, as shown in FIG. 14, after the time t23, the increase in the target intake manifold equivalent ratio P is suppressed, and accordingly, the actual intake manifold equivalent ratio Q, and hence the purge fuel introduced into the intake pipe 33 is reduced. The amount is not increased appropriately, and the amount of evaporated fuel remaining in the fuel tank 41 cannot be sufficiently reduced.

  On the other hand, as shown in FIG. 13, at the time t24 immediately after the increase of the intake manifold air amount at the time t23, the actual intake manifold equivalent ratio u (t24) is comparatively similar to the comparative example also in this embodiment. It can be suppressed to a small value. However, in this embodiment, the basic increase correction amount F set according to the intake manifold air amount and the sequential correction amount G set according to the air change amount ΔQa are added to the actual intake manifold equivalent ratio u (t24). Thus, the target intake manifold equivalent ratio s (t24) is calculated. Therefore, the target intake manifold equivalent ratio s (t24) is set to a relatively high value at time t24, and the actual intake manifold equivalent ratio u (t25) at time t5 is maintained at a high value. Similarly, after the time t24, the target intake manifold equivalent ratio s is set to a high value, and the actual intake manifold equivalent ratio u and thus the amount of purge fuel introduced into the intake pipe 33 is appropriately increased. Therefore, in this embodiment, the actual intake manifold equivalent ratio u can be appropriately increased even under operating conditions in which the intake manifold equivalent ratio tends to decrease as the intake manifold air amount increases, and the purge introduced into the intake pipe 33 The amount of fuel remaining in the fuel tank 41 can be reduced early by appropriately increasing the amount of fuel.

  As shown in FIG. 16, in the comparative example, when deceleration starts at time t33 and the intake manifold air amount decreases, the actual intake manifold equivalent ratio Q (t34) becomes the target intake manifold equivalent ratio P ( It becomes larger than t33). Further, the value obtained by adding the constant value α to the excessive actual intake manifold equivalent ratio Q (t34) is set as the next target intake manifold equivalent ratio P (t34), so that the next target intake manifold equivalent ratio P (t34) is also set. It becomes an excessively large value. Therefore, in the comparative example, the amount of increase in the target intake manifold equivalent ratio P and the actual intake manifold equivalent ratio Q becomes larger than when there is no change in the intake manifold air amount shown by the broken line, that is, during steady operation. Therefore, in the comparative example, the increase amount of the purge fuel introduced into the intake pipe 33 becomes excessive, and the fluctuation of the equivalence ratio of the gas in the cylinder and the fluctuation of the engine torque become large.

  On the other hand, in the present embodiment, as described above, when the intake manifold air amount decreases, a value obtained by subtracting the absolute value of the correction amount G from the value obtained by adding the basic increase correction amount F to the actual intake manifold equivalent ratio u. Is the target intake manifold equivalent ratio s. Therefore, as shown in FIG. 15, after time t33, it is possible to avoid an excessive increase in the target intake manifold equivalent ratio s, and thus the actual intake manifold equivalent ratio u, and appropriately increase them. Therefore, it is possible to suppress the fluctuation of the equivalence ratio of the gas in the cylinder and the fluctuation of the engine torque from increasing.

  Further, in the present embodiment, by calculating the target intake manifold equivalent ratio in accordance with the intake manifold air amount, it is possible to prevent the target intake manifold equivalent ratio and the actual intake manifold equivalent ratio from being greatly separated. . And it can suppress that the opening degree of the purge valve 45 changes suddenly in order to eliminate this separation, and the sudden change of the intake manifold equivalent ratio and the equivalent ratio of the gas in a cylinder resulting from this changes.

  Specifically, when the intake manifold air amount increases with the acceleration of the engine or the like as described above, the increase amount of the actual intake manifold equivalent ratio can be kept small. Therefore, in this state, when the target intake manifold equivalent ratio is simply increased by a fixed amount, the increase in the actual intake manifold equivalent ratio is small with respect to the increase in the target intake manifold equivalent ratio, so that these separations increase. On the other hand, in this embodiment, since the target intake manifold equivalent ratio is calculated based on the intake manifold air amount, the target intake manifold equivalent ratio can be adjusted to an appropriate value according to the increase or decrease of the intake manifold air amount, The separation between the target intake manifold equivalent ratio and the actual intake manifold equivalent ratio can be kept small.

  In particular, in the present embodiment, the target intake manifold equivalent ratio is set to a value obtained by adding an increase correction amount calculated based on the intake manifold air amount to the current intake manifold equivalent ratio. The deviation from the ratio can be reduced more reliably.

  Thus, if the target intake manifold equivalent ratio is calculated based on the intake manifold air amount, a sudden change in the equivalent ratio in the cylinder can be basically reduced.

  However, in the engine that switches the engine operation between the all-cylinder operation and the reduced-cylinder operation as in the present embodiment, when the target intake manifold equivalent ratio is changed based on the intake manifold air amount at the time of this switching, as in other operations. As the intake manifold air amount fluctuates greatly with switching, the fluctuation amount of the target intake manifold equivalent ratio increases. At the time of switching, the equivalence ratio in the cylinder 2 is likely to change due to this switching. For this reason, if the target intake manifold equivalent ratio and the intake manifold equivalent ratio change greatly at the time of switching, the variation amount of the equivalent ratio in the cylinder 2 may become excessive.

  On the other hand, in the present embodiment, when a switching request between the all cylinder operation and the reduced cylinder operation is issued, the target intake manifold equivalent ratio is maintained at the target intake manifold equivalent ratio immediately before the switch request. For this reason, it is possible to prevent the variation amount of the equivalence ratio in the cylinder 2 from becoming excessive by suppressing the variation of the intake manifold equivalent ratio. This will be specifically described with reference to FIG. FIG. 17 is an enlarged view of a part of the graph shown in FIG. In FIG. 17, the broken line in the intake manifold equivalent ratio and purge fuel amount graph shows the target intake manifold in the same procedure (procedure for performing steps S28 to S34) at the time of switching between the all cylinder operation and the reduced cylinder operation. The change when the equivalent ratio is calculated is shown.

  As shown by the broken line in FIG. 17, if the target intake manifold equivalent ratio is calculated in the same procedure as during other operations when switching from all-cylinder operation to reduced-cylinder operation from time t1 to time t3, preparation is performed. The target intake manifold equivalent ratio, and therefore the intake manifold equivalent ratio, rapidly increases as the intake air amount increases as control is performed. Along with this, the amount of purge fuel also increases rapidly. For this reason, the equivalence ratio in the cylinder 2 is not stable, and the amount of fluctuation may be excessive. Similarly, when the target intake manifold equivalent ratio is calculated in the same procedure as during other operations when returning from reduced-cylinder operation to all-cylinder operation, all-cylinder operation starts from time t10 to time t12. Accordingly, when the intake manifold air amount increases, the target intake manifold equivalent ratio, and thus the intake manifold equivalent ratio, rapidly increases. For this reason, the equivalence ratio in the cylinder is not stable, and the fluctuation amount may be excessive.

  In contrast, in the present embodiment, as shown by the solid line in FIG. 17, the target intake manifold equivalent ratio and the intake manifold equivalent ratio increase rapidly from time t1 to time t3 and from time t10 to time t12. Can be avoided, and the equivalence ratio in the cylinder can be stabilized.

  Further, in this embodiment, the amount of purge fuel introduced into the engine body 1 is gradually increased toward the target maximum purge fuel amount Qcharge_max, and finally controlled to this target maximum purge fuel amount Qcharge_max. The injection amount of the injector 12 is controlled to a value obtained by subtracting the amount of purge fuel introduced into the engine body 1 from the cylinder required fuel amount Qcyl. Here, as described above, the target maximum purge fuel amount Qpurge_max is a value obtained by subtracting the minimum injection amount Qinj_min from the cylinder required fuel amount Qcyl. Therefore, during the purge, the injection amount of the injector 12 is gradually decreased toward the minimum injection amount Qinj_min and finally controlled to the minimum injection amount Qinj_min.

  Therefore, during the purge, the engine torque can be maintained at an appropriate value with the total amount of fuel introduced into the engine body 1 as the cylinder required fuel amount Qcyl, and the injection amount of the injector 12 as the minimum injection amount Qinj_min. Thus, a large amount of purge fuel (a purge fuel corresponding to the target maximum purge fuel amount Qpurge_max) can be introduced into the engine body 1 while ensuring the controllability of the fuel amount by the injector 12 by ensuring the linearity characteristic of 12 and evaporative fuel. Can be prevented from leaking into the atmosphere.

(4) Modified Example In the above embodiment, the period (predetermined period) for maintaining the target intake manifold equivalent ratio (i) at the target intake manifold equivalent ratio immediately before the switch request is issued after the switch request is issued is shown in FIG. It is a period from time t1 to time t3, the period from when the preparation control is started until the intake manifold air amount decreases to the air amount during normal reduced cylinder operation, and from time t10 to time t12 in FIG. When the return control is being carried out, more specifically, when the intake manifold air amount is reduced to the air amount during normal all-cylinder operation after the return control is started However, it may be set only during the execution period of the preparation control and during the execution period of the return control.

  In the above embodiment, the target intake manifold equivalent ratio (i) is maintained at the previous target intake manifold equivalent ratio (i-1) at the time of switching between all-cylinder operation and reduced-cylinder operation, thereby immediately before a switching request is issued. Although the case where the target intake manifold equivalent ratio is maintained has been described, the target intake manifold equivalent ratio (i) may be increased with respect to the previous target intake manifold equivalent ratio (i-1).

  However, even in this case, the target intake manifold equivalent ratio change amount based on the intake manifold air amount is smaller than the target intake manifold equivalent ratio change amount based on the intake manifold air amount during operation other than switching. Calculate the intake manifold equivalent ratio.

  Specifically, at the time of switching, steps S28 to S34 in FIG. 8 may be performed to calculate the target intake manifold equivalent ratio. However, in this case, even if the air change amount ΔQa, which is the change amount of the intake manifold air amount, is the same, the sequential correction amount G set based on the air change amount ΔQa is different from the other operation when switching. The value is smaller than the hour. For example, when the successive correction amount G is calculated by multiplying the air change amount ΔQa by a predetermined coefficient, the coefficient at the time of switching is made smaller than the coefficient at the time of operation other than at the time of switching. Alternatively, even if the intake manifold air amount is the same, the basic increase correction amount F set based on the intake manifold air amount is set to a value smaller at the time of switching than at the time of other operations. Alternatively, at the time of switching, both the successive correction amount G and the basic increase correction amount F may be made smaller than those other than at the time of switching. Further, at the time of switching, control may be performed so that one of the successive correction amount G and the basic increase correction amount F is set to zero.

  In the above embodiment, the basic increase correction amount F is changed according to the intake manifold air amount. However, the basic increase correction amount F may be set to a constant value. Even in this case, the target intake manifold equivalent ratio and the actual intake manifold equivalent ratio can be appropriately controlled by setting the successive correction amount G according to the air change amount ΔQa. However, if the basic increase correction amount F is changed according to the intake manifold air amount, the intake manifold equivalent ratio can be controlled more reliably by a value corresponding to the intake manifold air amount.

  In the above-described embodiment, the case where the injector 12 directly injects fuel into the cylinder 2 has been described. However, the injector 12 may inject fuel into the intake passage 30.

1 Engine body 12 Injector (fuel injection valve)
30 Intake passage 41 Fuel tank 42 Canister 43 Purge pipe (Purge passage)
45 Purge valve 100 PCM (control means)

Claims (9)

Combustion of air-fuel mixture in all cylinders, including an engine body having an intake valve and an exhaust valve and a plurality of cylinders formed, an intake passage for introducing intake air into the engine body, and a fuel tank for storing fuel Evaporation provided in an engine that can be switched between all-cylinder operation in which combustion is performed and reduced-cylinder operation in which combustion in a specific cylinder among a plurality of cylinders is stopped and the specific cylinder is in a rest state A fuel processor,
A purge passage connected to the intake passage for introducing a purge gas containing evaporated fuel evaporated in the fuel tank into the intake passage;
A purge valve capable of opening and closing the purge passage;
Control means for controlling the purge valve,
The control means implements an increase control for controlling the purge valve so that an intake manifold equivalent ratio, which is an equivalent ratio of gas in the intake passage, increases when performing purge for introducing the purge gas into the intake passage. When the increase control is performed, the target intake manifold equivalent ratio, which is the target value of the intake manifold equivalent ratio, is changed based on the amount of air flowing through the intake passage, and all cylinder operation is performed during the execution of the increase control. When a switching request for switching the operation with the reduced-cylinder operation is issued, a change amount of the target intake manifold equivalent ratio based on the amount of air flowing through the intake passage is determined for a predetermined period after the switching request is issued. An evaporative fuel processing device for an engine characterized by being made smaller. The evaporative fuel processing device for an engine according to claim 1,
When a request for switching from all-cylinder operation to reduced-cylinder operation is issued, the control means performs preparation control to increase the amount of air introduced into the engine body while performing combustion of the air-fuel mixture in all cylinders. When the reduction control operation is started after the preparation control is performed and a request for switching from the all-cylinder operation to the reduction cylinder operation is issued during the execution of the increase control, at least the period during which the preparation control is performed An evaporative fuel processing device for an engine, wherein the change amount of the target intake manifold equivalent ratio based on the amount of air flowing through the intake passage is reduced. The evaporated fuel processing apparatus for an engine according to claim 1 or 2,
When a request for switching from reduced-cylinder operation to full-cylinder operation is issued, the control means performs return control for reducing the amount of air introduced into the engine body while starting full-cylinder operation, and the increase control When a request for switching from reduced-cylinder operation to all-cylinder operation is issued during the execution of the above, at least a period during which the return control is being performed, the amount of change in the target intake manifold equivalent ratio based on the amount of air flowing through the intake passage An evaporative fuel processing apparatus for an engine characterized by reducing the size of the engine. In the evaporative fuel processing apparatus of the engine in any one of Claims 1-3,
The control means estimates the current intake manifold equivalent ratio when performing the increase control, and calculates an increase correction amount of the intake manifold equivalent ratio based on the most recent change amount of the air amount flowing through the intake passage. Then, the target intake manifold equivalent ratio is calculated by adding the increase correction amount to the estimated intake manifold equivalent ratio. The evaporated fuel processing apparatus for an engine according to claim 4,
The control means adds a sequential correction amount that is increased or decreased according to the most recent change amount of the air amount to a basic increase correction amount that is predetermined so as to increase as the air amount flowing through the intake passage increases. What is calculated as the increase correction amount is a fuel vapor processing apparatus for an engine. The evaporated fuel processing apparatus for an engine according to claim 5,
The control means sets the successive correction amount to a value greater than 0 when the most recent change amount of the air amount flowing through the intake passage is greater than 0, and when the most recent change amount of the air amount is less than zero. Is a fuel vapor processing apparatus for an engine, wherein the successive correction amount is set to a value smaller than 0. In the evaporative fuel processing apparatus of the engine in any one of Claims 4-6,
The control means is configured to reduce the increase correction amount when a request for switching between all-cylinder operation and reduced-cylinder operation is issued during the execution of the increase control, and based on the amount of air flowing through the intake passage. An evaporative fuel processing device for an engine, characterized in that a change amount of a target intake manifold equivalent ratio is reduced. In the evaporative fuel processing apparatus of the engine in any one of Claims 1-7,
When the switching request between the all-cylinder operation and the reduced-cylinder operation is issued during the execution of the increase control, the control means sets the target intake manifold equivalent ratio to a value before the switching request is issued for the predetermined period. An evaporative fuel processing device for an engine characterized by being maintained in the above. In the evaporative fuel processing apparatus of the engine in any one of Claims 1-8,
A fuel injection valve for injecting fuel into the cylinder or the intake passage;
The control means sets a reference target fuel amount that is a target value of the total fuel amount to be supplied to the engine main body based on the operating state of the engine main body, and the fuel injection valve of the fuel injection valve that ensures the linearity characteristics of the fuel injection valve. The target maximum purge fuel amount is calculated by subtracting the minimum value of the injection amount from the reference target fuel amount, and the amount of evaporated fuel introduced into the engine body via the purge passage at the start of the purge is the target maximum fuel amount. The increase control is performed until the amount of purge fuel is reached, and the fuel is injected so as to inject an amount of fuel obtained by subtracting the amount of evaporated fuel introduced into the engine body through the purge passage from the reference target fuel amount. An evaporative fuel processing apparatus for an engine characterized by controlling an injection valve.

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