JP2016180394A - Evaporation fuel control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To more securely supply appropriate amount of evaporation fuel to an intake passage.SOLUTION: An evaporation fuel control device for an internal combustion engine includes: a purge passage 43 for communicating a canister 42 and an intake passage 23 with each other; a purge valve 47 for opening/closing the purge passage 43; and a rotary pump 44 that is provided in the purge passage 43 to increase a pressure difference between an upstream end and a downstream end of the purge passage 43 as the rotational frequency increases. An opening of the purge valve 45 is controlled to an intermediate opening, and the rotational frequency of the pump is controlled to a target pump rotational frequency that is set to increase as the required purge amount increases. When a deviation between rotational frequency Np of the pump and target pump rotational frequency Npo is a reference deviation or larger, until the deviation becomes lower than the reference deviation, the opening of the purge valve 47 is corrected so that the amount of purge gas introduced to the intake passage 23 becomes the required purge amount according to the required purge amount and the rotational frequency of the pump 44.SELECTED DRAWING: Figure 3

Description

  The present invention includes a cylinder, an intake passage for introducing air into the cylinder, a fuel tank in which fuel is stored, and a canister that detachably adsorbs evaporated fuel generated in the fuel tank, and intake air from the canister The present invention relates to an evaporated fuel control device for an internal combustion engine in which purge gas containing evaporated fuel is introduced into a passage.

  Conventionally, evaporative fuel generated in a fuel tank is introduced into an intake passage via a canister and burned in a cylinder.

  For example, Patent Document 1 discloses a device including a purge passage that communicates a canister and an intake passage, an ON / OFF type on-off valve that opens and closes the purge passage, and a pump. In the device of Patent Document 1, the pressure difference between the upstream end and the downstream end of the purge passage is changed by changing the rotation speed of the pump while the on-off valve is opened, and is thereby introduced from the canister into the intake passage. The amount of purge gas is changed.

JP 2007-177727 A

  Here, since there is a response delay in the pump, it takes time until the rotational speed of the pump changes to the predetermined rotational speed. For this reason, the apparatus of Patent Document 1 has a problem that the amount of purge gas cannot be set to an appropriate amount until the pump changes to a predetermined rotational speed. In addition, since an appropriate amount of the evaporated fuel contained in the purge gas is not supplied into the cylinder, the air-fuel ratio in the cylinder may deviate from the target value, thereby deteriorating exhaust performance and the like.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an evaporated fuel control device for an internal combustion engine that can supply an appropriate amount of evaporated fuel to an intake passage more reliably. To do.

  In order to solve the above problems, the present invention provides a cylinder, an intake passage for introducing air into the cylinder, a fuel tank in which fuel is stored, and an evaporated fuel generated in the fuel tank so as to be detachable. An evaporative fuel control apparatus for an internal combustion engine, wherein a purge gas containing evaporative fuel desorbed from the canister is introduced into an intake passage, the purge passage communicating the canister and the intake passage, and the purge A purge valve provided in the passage for opening and closing the passage, a rotary pump provided in the purge passage for increasing the pressure difference between the upstream end and the downstream end of the purge passage as the rotational speed increases, and the purge valve Control means for controlling the opening degree and the rotation speed of the pump, the control means at least in a specific operating region, the opening degree of the purge valve The intermediate opening between the fully closed and fully opened is controlled, and the pump speed is controlled to a higher target pump speed as the required purge amount, which is the amount of purge gas required, increases. When the deviation between the rotation speed of the pump and the target pump rotation speed is equal to or greater than a predetermined reference deviation, the amount of purge gas introduced into the intake passage until the deviation becomes less than the reference deviation is The opening degree of the purge valve is corrected in accordance with the required purge amount and the rotational speed of the pump so as to be the required purge amount.

  According to the present invention, since the rotational speed of the pump is controlled in accordance with the required purge amount in a specific operation region, an appropriate amount of purge gas, that is, evaporated fuel, can be introduced into the intake passage and the cylinder. In addition, if the deviation between the pump speed and the target pump speed is greater than or equal to a predetermined standard deviation, the opening of the purge valve will be equal to the required purge amount and the pump speed until this deviation becomes less than the standard deviation. Accordingly, the required purge amount is corrected so as to be realized. Therefore, the amount of purge gas can be made the required amount by changing the opening of the purge valve until the rotational speed of the pump reaches the target pump rotational speed. Therefore, it is possible to suppress the deviation of the purge gas amount from the required amount due to the delay in response of the pump, and it is possible to more reliably introduce the evaporated fuel into the appropriate amount intake passage.

  In the present invention, the target pump rotational speed and the intermediate opening degree are respectively determined when the pump rotational speed is set to the minimum rotational speed of the target pump rotational speed in the specific operation region and the purge valve is fully opened. The amount of purge gas supplied to the passage is supplied to the intake passage when the pump rotational speed is set to the maximum rotational speed of the target pump rotational speed in the specific operation region and the purge valve is set to the intermediate opening. It is preferably set to be equal to or greater than the amount of purge gas.

  In this way, the deviation of the purge gas amount from the required amount caused by the pump response delay can be eliminated by correcting the purge valve opening throughout the specific operation region. As a result, the amount of evaporated fuel introduced into the intake passage can be more reliably set to an appropriate amount.

  In the present invention, it is preferable that the intermediate opening is set to a constant opening regardless of the required purge amount.

  In this way, the control configuration of the purge valve opening can be simplified.

  In the present invention, it is preferable that the specific operation region is set to a region where the compressed self-ignition combustion of the air-fuel mixture having an air-fuel ratio larger than 1 is performed in the cylinder.

  As described above, in the present invention, the amount of evaporated fuel introduced into the intake passage can be appropriately controlled, so that the air-fuel ratio of the air-fuel mixture in the cylinder can be controlled more accurately. Therefore, according to this configuration, it is possible to realize appropriate compression self-ignition combustion while making the air-fuel ratio leaner than 1 more reliably.

  As described above, according to the evaporated fuel control apparatus for an internal combustion engine of the present invention, an appropriate amount of evaporated fuel can be more reliably supplied to the intake passage.

It is a figure showing composition of an engine system concerning one embodiment of the present invention. It is the figure which showed the operation area | region which concerns on a combustion form. It is the flowchart which showed the flow of control of purge amount. It is the figure which showed the relationship between request | requirement purge amount and target pump rotation speed. It is the figure which showed the relationship between request | requirement purge amount and DUTY ratio of a purge valve. It is the figure which showed the change of each parameter when a request | requirement purge amount increases.

(1) Overall Configuration of Engine FIG. 1 is a diagram showing a configuration of an engine system to which an evaporated fuel control device for an internal combustion engine according to an embodiment of the present invention is applied. The engine system of this embodiment includes a four-stroke engine main body 1, an intake passage 20 for introducing combustion air (intake air) into the engine main body 1, and an exhaust for discharging exhaust from the engine main body 1 to the outside. A passage 31 and a purge system 40 for introducing evaporated fuel generated in the fuel tank 41 into the engine body 1 are provided. The engine body 1 is, for example, a four-cylinder engine having four cylinders 2a arranged in a direction orthogonal to the paper surface of FIG.

  Here, the case where the engine body 1 is a gasoline engine mainly using gasoline as a fuel will be described.

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

  A combustion chamber 5 is formed above the piston 4. Fuel is injected from the injector 10 into the combustion chamber 5. The injected fuel / air mixture is combusted in the combustion chamber 5, and the piston 4 is pushed down by the expansion force generated by the combustion and reciprocates up and down.

  The piston 4 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 4.

  The cylinder block 2 is provided with an engine speed sensor SW1 that detects the speed of the crankshaft 15 as the engine speed.

  The cylinder head 3 is provided with a pair of injectors 10 and spark plugs 11 for igniting a mixture of fuel and air injected from the injectors 10 by spark discharge for each cylinder 2a.

  The injector 10 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 2a from the side on the intake side. The fuel stored in the fuel tank 41 is supplied to the injector 10 through a filter or the like.

  The spark plug 11 has an electrode for discharging sparks at the tip, and is provided so as to face the combustion chamber 5 of each cylinder 2a from above.

  The engine body 1 of the present embodiment has a geometric compression ratio (ratio between the combustion chamber volume when the piston 4 is at bottom dead center and the combustion chamber volume when the piston 4 is at top dead center). The engine is set to a relatively high value. The reason for setting such a high geometric compression ratio is to improve the theoretical thermal efficiency and to ensure the ignitability in CI combustion (compression self-ignition combustion) described later.

  The cylinder head 3 includes an intake port 6 for introducing air supplied from the intake passage 20 into the combustion chamber 5 of each cylinder 2a, an intake valve 8 for opening and closing the intake port 6, and the combustion chamber 5 of each cylinder 2a. Are provided with an exhaust port 7 for leading the exhaust gas generated in step 1 to the exhaust passage 31 and an exhaust valve 9 for opening and closing the exhaust port 7.

  The intake passage 20 has a single intake pipe 23 and a plurality of (four) independent intake passages 24 (perpendicular to the plane of FIG. 1) for individually connecting the intake pipe 23 and the intake port 6 of each cylinder 2a. Are arranged in the direction). A surge tank 22 having a predetermined volume is provided at the downstream end of the intake pipe 23, and an independent intake passage 24 extends from the surge tank 22 to each intake port 6.

  A throttle valve 25 capable of opening and closing the passage of the intake pipe 23 and an air flow sensor SW2 for detecting the flow rate of air (intake) taken into the engine body 1 are provided in the middle of the intake pipe 23. . In the present embodiment, the throttle valve 25 has an opening that is almost always fully open except when the fuel injection is stopped, in order to keep the pumping loss small.

  The exhaust passage 31 includes a single exhaust pipe and a plurality of (four) independent intake passages that individually connect the exhaust pipe and the exhaust port 7 of each cylinder 2a. The exhaust passage 31 is provided with a catalytic converter 39 in which a catalyst such as a three-way catalyst is incorporated. Further, the exhaust passage 31 is provided with an A / F sensor SW3 for detecting the air-fuel ratio (ratio of air to fuel) of the exhaust gas, and thus the air-fuel mixture in the cylinder 2a.

  For example, for the purpose of increasing the temperature in the cylinder 2a or keeping the combustion temperature low, the exhaust passage 31 and the intake pipe 23 are connected, and a part of the exhaust is recirculated to the intake pipe 23. An EGR system may be provided.

  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 23. Passage) 43.

  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 23 through the purge pipe 43 together with air. Hereinafter, this gas composed of evaporated fuel and air is referred to as purge gas.

  The purge pipe 43 is connected to a portion of the intake pipe 23 that is downstream of the throttle valve 25. In the present embodiment, the purge pipe 43 is connected to the surge tank 22.

  The purge pipe 43 is provided with an air pump (pump) 44 that changes the differential pressure between the upstream end (connection portion with the canister 42) and the downstream end (connection portion with the intake pipe 23) of the purge pipe 43. The air pump 44 is driven to rotate by a pump motor (not shown) to pressurize the gas in the purge pipe 43. The higher the number of revolutions, the higher the pressure of the purge pipe 43 where the air pump 44 is installed. Increase the differential pressure. The air pump 44 is provided with a pump rotation speed sensor SW4 that detects the rotation speed.

  In addition, a purge valve 45 that opens and closes the purge pipe 43 is provided at a portion downstream of the air pump 44 of the purge pipe 43 (on the intake pipe 23 side). The purge valve 45 is a DUTY control valve that repeatedly opens and closes, and the opening degree is changed by changing the DUTY ratio, which is the ratio of the valve opening period to the unit period that combines one valve opening period and the valve closing period. It is what is done. The purge valve 45 is an electromagnetic valve, and the DUTY ratio is the ratio of the energization period to the unit period including one energization period and one non-energization period. The purge valve 45 comprising the DUTY control valve is fully closed when the DUTY ratio is 0% and fully opened when 100%. Further, the opening degree, that is, the gas flow rate that passes through the valve in the unit period is changed almost in proportion to the duty ratio. More specifically, in the purge valve 45 according to the present embodiment, the DUTY ratio and the opening degree are not proportional to each other in the vicinity of the fully closed state and the fully opened state. For example, the DUTY ratio and the opening degree are proportional to each other between 5% and 95%. To do. Further, even if the DUTY ratio is not 100%, the valve opening is fully open at a value close to 100% (for example, a value of 95% or more).

(2) Control system Next, the control system of the engine system will be described. The engine system of this embodiment is mounted on a vehicle such as an automobile, and is controlled by an ECU (engine control unit) 60 provided in the vehicle. As is well known, the ECU 60 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 ECU 60. For example, the ECU 60 is electrically connected to an engine speed sensor SW1, an air flow sensor SW2, an A / F sensor SW3, and a pump speed sensor SW4, and input signals (engine speed, intake air flow rate) from these sensors. Information, the air-fuel ratio of the air-fuel mixture in the cylinder 2a, and the rotation speed of the air pump 44). Further, the vehicle is provided with an accelerator opening sensor SW5 for detecting the opening degree of the accelerator pedal 70 operated by the driver, a vehicle speed sensor SW6 for detecting the vehicle speed, and a shift stage sensor SW7 for detecting the shift stage. Detection signals from these sensors SW5 to SW7 are also input to the ECU 60. Note that the gear position may be calculated based on the vehicle speed detected by the vehicle speed sensor SW6 and the engine speed detected by the engine speed sensor SW1.

  ECU60 controls each part of an engine system, performing various calculations etc. based on the input signal from each sensor (SW1-SW7 grade | etc.,). That is, the ECU 60 includes the injector 10, the spark plug 11, the throttle valve 25, the intake valve 8 (a drive mechanism that drives the intake valve 8), the exhaust valve 9 (the drive mechanism that drives the exhaust valve 9), and the air pump 44 (the air pump 44). And a purge valve 45 (a drive mechanism for driving the purge valve 45) and the like, and outputs a control signal for driving to each of these devices based on the result of the calculation.

(I) Control of Engine Body FIG. 2 is a diagram conceptually showing a control map related to the combustion mode referred to by the ECU 60 during operation of the engine.

  In the present embodiment, as shown in this control map, in the first operation region A1 from the lowest load of the engine to the switching load T1, the air-fuel mixture is heated to a high temperature and pressure by the compression action of the piston 4, and near the compression top dead center. CI combustion for self-ignition (compression self-ignition combustion) is performed, and in the second operation region A2 from the switching load T1 to the maximum load, the air-fuel mixture is burned by flame propagation triggered by forced ignition by spark discharge from the spark plug 11 SI combustion (spark ignition combustion) is performed.

  In the present embodiment, in the first operating region A1, the air-fuel ratio of the air-fuel mixture in the cylinder 2a is made larger than 1, and lean CI combustion is performed.

  The ECU 60 sequentially determines in which operating region the engine is operating in the map of FIG. 2 from each value of the load (engine required torque based on the accelerator opening) and the engine speed during operation of the engine. The injector 10 and the like are controlled according to the area.

  Specifically, in the first operation region A1, ignition by the spark plug 11 is stopped and fuel is injected into the combustion chamber by the injector 10 during the intake stroke. On the other hand, in the second operation region A2, ignition by the spark plug 11 is performed.

  In this embodiment, as described above, the ECU 60 almost always sets the throttle valve 25 to an opening degree near the fully open position.

(Ii) Purge Control Next, control of purge gas introduced from the canister 42 into the intake pipe 23 will be described.

  First, the concentration learning of the evaporated fuel contained in the purge gas will be briefly described.

  In the present embodiment, based on the air-fuel ratio of the air-fuel mixture in the cylinder 2a detected by the A / F sensor SW3 and the amount of air introduced into the cylinder 2a estimated from the detection value of the airflow sensor SW2, etc. The amount of fuel supplied to 2a is estimated. Then, the amount of evaporated fuel supplied to the cylinder 2a is estimated by subtracting the amount of fuel injected from the injector 10 into the cylinder 2a from this amount of fuel. Then, the concentration of the evaporated fuel contained in the purge gas is estimated and learned from the required purge amount described later and the estimated evaporated fuel amount.

  In this embodiment, the concentration learning of the evaporated fuel is performed almost constantly during operation of the engine and is constantly updated. If the concentration learning has not yet been performed at the time of starting, etc., first, a small amount of purge gas is supplied to the intake pipe 23 under operating conditions with a low engine load such as idle operation. The concentration of the evaporated fuel is estimated based on the detected value of the A / F sensor SW3.

  Next, the purge gas flow rate control performed by the ECU 60 will be described with reference to the flowchart of FIG. The flowchart of FIG. 3 shows a control procedure after the evaporative fuel concentration learning is performed at least once.

  First, in step S1, the detected value (vehicle speed) of the vehicle speed sensor SW6, the detected value of the accelerator opening sensor SW5 (accelerator opening), the detected value of the shift speed sensor SW7 (shift speed), and the detection of the pump speed sensor SW4. Read the value (pump speed Np).

  Next, in step S2, the engine required torque is calculated based on the vehicle speed, accelerator opening, and gear position read in step S1.

  Next, in step S3, a required fuel amount that is a target value of the fuel amount to be supplied into the cylinder 2a is calculated based on the engine required torque calculated in step S2.

  Next, in step S4, based on the required fuel amount calculated in step S3, a required evaporated fuel amount that is the amount of evaporated fuel introduced into the cylinder 2a and the intake pipe 23 is calculated. Specifically, a certain amount of the required fuel amount is calculated as the required evaporated fuel amount. Thus, in the present embodiment, the required fuel amount, that is, the engine load and the required evaporated fuel amount are proportional.

  Next, in step S5, based on the required evaporated fuel amount calculated in step S4, the target purge gas amount per unit time introduced into the intake pipe 23, that is, the purge gas flow rate (hereinafter sometimes referred to as the purge amount). Calculate the requested purge amount that is the value. Specifically, the amount of purge gas including the required evaporated fuel amount is calculated as the required purge amount from the required evaporated fuel amount and the learned concentration of evaporated fuel.

  Next, in step S6, based on the required purge amount calculated in step S5, the target pump speed Npo, which is the target value of the speed of the air pump 44, and the basic DUTY, which is the basic value of the DUTY ratio of the purge valve 45, Set the ratio.

  In the present embodiment, the target pump speed Npo is set as shown in FIG.

  Specifically, in the low flow rate region (specific operation region) B1 in which the required purge amount is less than the preset reference purge amount Qp1, the target pump rotational speed Npo is set to the preset first rotational speed (minimum rotational speed). ) Between N1_min and the second rotation speed (maximum rotation speed) N1_max, the higher the required purge amount, the higher the setting. In this embodiment, the target pump speed Npo is increased in proportion to the required purge amount.

  The reference purge amount Qp1 is set to a value equal to or less than a certain percentage of the required fuel amount when the engine load becomes the switching load T1, and the low flow region B1 is a first operation region A1 in which lean CI combustion is performed. Included.

  In the high flow rate region B2 where the required purge amount is equal to or greater than the reference purge amount Qp1, the target pump rotational speed Npo is set so as to increase in proportion to the required purge amount from a value N2 lower than the second rotational speed N1_max.

  Further, the basic DUTY ratio is set as shown in FIG.

  Specifically, in the low flow rate region B1, the basic DUTY ratio is between 0% and 100% so that the basic opening of the purge valve 45 is an intermediate opening between fully closed and fully opened. Set to an intermediate value. In the present embodiment, this intermediate value is set to a constant value D1 (hereinafter referred to as a low flow basic DUTY ratio as appropriate) regardless of the required purge amount, and the basic opening of the purge valve 45 is required in the low flow region B1. The opening degree is constant regardless of the purge amount. Further, as described above, the low flow basic DUTY ratio is set to a value within a range (for example, between 5% and 95%) in which the opening degree of the purge valve 45 is proportional to the DUTY ratio.

  Further, in the high flow rate region B2, the basic DUTY ratio is set to 100%, and the basic opening of the purge valve 45 is fully opened.

  Here, the first rotation speed N1_min and the low flow rate basic DUTY ratio D1 are set as follows. That is, when the rotation speed of the air pump 44 is the first rotation speed N1_min and the DUTY ratio of the purge valve 45 is the low flow basic DUTY ratio D1, the purge amount becomes the minimum value of the required purge amount, and the rotation of the air pump 44 When the number is set to the first rotation speed N1_min and the purge valve 45 is fully opened (the duty ratio is a value close to 100% and the valve opening degree and the duty ratio are in a maximum range (for example, 95%)), the purge is performed. The amount is set to be equal to or greater than the maximum required purge amount (reference purge amount Qp1) in the low flow rate region B1.

  In step S7 following step S6, the rotational speed of the air pump 44 is controlled to the target pump rotational speed Npo set in step S6. Specifically, the driving force of the pump motor is changed so that the rotation speed of the air pump 44 becomes the target pump rotation speed Npo.

  In step S8 following step S7, it is determined whether the requested purge amount calculated in step S5 is less than the reference purge amount Qp1. That is, it is determined whether or not the vehicle is operating in the low flow rate region B1.

  When the determination in step S8 is NO and the required purge amount is equal to or greater than the reference purge amount Qp1 and the operation is performed in the high flow rate region B2, the process proceeds to step S10, and the DUTY ratio is controlled to the basic DUTY ratio. As described above, in the high flow rate region B2, the basic DUTY ratio is set to 100%, and in step S10, the DUTY ratio is set to 100% and the purge valve 45 is fully opened. After step S10, the process ends (returns to step S1).

  On the other hand, if the determination in step S8 is YES and the required purge amount is less than the reference purge amount Qp1, and the operation is performed in the low flow rate region B1, the process proceeds to step S11.

  In step S11, whether or not the deviation (absolute value of these differences) between the target pump speed Npo set in step S6 and the current pump speed Np detected in step S1 is less than a preset reference deviation. Determine whether. The reference deviation is set to a value close to 0, for example.

  If the determination in step S11 is YES and the pump rotational speed Np has reached the rotational speed at which the deviation from the target pump rotational speed Npo is less than the reference deviation, the process proceeds to step S12, where the DUTY ratio is set as the basic. Control to DUTY ratio. As described above, in the low flow rate region B1, the basic DUTY ratio is set to the low flow basic DUTY ratio D1, which is an intermediate value. In step S12, the DUTY ratio is set to the low flow basic DUTY ratio D1, and the purge valve 45 The opening is an intermediate opening. After step S12, the process ends (returns to step S1).

  On the other hand, if the determination in step S11 is NO and the pump rotational speed Np has not reached the rotational speed at which the deviation from the target pump rotational speed Npo is less than the reference deviation, the process proceeds to step S13.

  In step S13, the required purge amount is realized based on the DUTY ratio of the purge valve 45 based on the current pump rotational speed Np (the pump rotational speed Np detected in step S1) and the required purge amount set in step S5. Correct as follows. That is, the DUTY ratio is corrected to a DUTY ratio that allows the purge amount to be the required purge amount at the current pump speed Np. In the present embodiment, the relationship among the pump rotational speed Np, the DUTY ratio, and the purge amount is obtained in advance by experiments or the like, and is stored in the ECU 60 as a map. The ECU 60 determines the required purge amount and the current pump rotation from this map. A DUTY ratio corresponding to the number Np is extracted. After step S13, the process ends (returns to step S1). In this embodiment, the DUTY ratio is corrected within a range in which the DUTY ratio and the valve opening are proportional.

(3) Operation etc. As described above, in this embodiment, in the low flow rate region B1 where the required purge amount is less than the reference purge amount Qp1, the low flow rate basic DUTY ratio in which the DUTY ratio of the purge valve 45 is basically an intermediate value. The opening degree of the purge valve 45 is set to the intermediate opening degree as D1.

  On the other hand, when the required fuel amount changes at the time of acceleration / deceleration, the required purge amount changes, and when the target pump rotational speed Npo changes with the change in the required purge amount, the target pump rotational speed Npo When the pump rotational speed Np has not reached the rotational speed at which the deviation is less than the reference deviation, the pump rotational speed Np is changed toward the target pump rotational speed Npo, and the DUTY ratio is corrected, thereby purging. The amount is controlled to the required purge amount.

  Therefore, in the low flow rate region B1, an appropriate amount of purge gas, that is, evaporated fuel, can be introduced into the intake pipe 23 by changing the pump rotational speed Np, and the purge amount deviates from the required purge amount due to the response delay of the air pump 44. Therefore, the purge gas and the evaporated fuel can be more reliably introduced into the intake pipe 23 in an appropriate amount.

  This will be specifically described with reference to FIG. FIG. 6 is a diagram schematically showing temporal changes in the purge amount, the pump speed, and the DUTY ratio of the purge valve 45 when the required purge amount increases with acceleration or the like. In FIG. 6, a solid line indicates a state when the above control according to the present embodiment is performed, and a chain line indicates a state in a comparative example in which the control of steps S <b> 11 and S <b> 13 is omitted.

  When the required purge amount increases rapidly at time t1, the target pump speed also increases rapidly. However, since the rotation of the air pump 44 has a response delay, the pump rotation speed does not increase immediately. Therefore, in the case of the comparative example, that is, when the DUTY ratio of the purge valve 45 is not corrected based on the pump rotational speed or the like, the purge amount increases only gradually and the deviation of the purge amount from the target value (required purge amount) is large. Become. Therefore, in the case of this comparative example, the amount of evaporated fuel introduced into the intake pipe 23 is greatly deviated from the required amount of evaporated fuel, and the air-fuel ratio of the air-fuel mixture in the cylinder 2a is largely deviated from the target air-fuel ratio.

  On the other hand, in this embodiment, when the required purge amount and the target pump rotational speed increase rapidly at time t1, the DUTY ratio of the purge valve 45 is corrected according to the current pump rotational speed and the required purge amount. In the example shown in FIG. 6, immediately after time t1, the purge valve 45 is fully opened by setting the DUTY ratio of the purge valve 45 to a value close to 100%, which is larger than the low flow rate basic DUTY ratio D1. As the pump speed increases, the DUTY ratio of the purge valve 45 decreases. Therefore, the purge amount can be increased to the required purge amount at an early stage and maintained at the required purge amount. Therefore, the air-fuel ratio of the air-fuel mixture in the cylinder 2a can be set to an appropriate value.

  In particular, in the present embodiment, as described above, the low flow rate region B1 is set to be included in the first operation region A1 where the lean CI combustion is performed. Therefore, if the air-fuel ratio of the air-fuel mixture shifts in this region B1 (A1), proper combustion may not be realized, and engine performance may be significantly deteriorated. For example, misfire may occur or exhaust performance may deteriorate. On the other hand, as described above, in this embodiment, the air-fuel ratio of the air-fuel mixture in the cylinder 2a can be maintained at an appropriate value in the low flow rate region B1, so that appropriate combustion can be realized.

  In the present embodiment, as described above, the purge amount becomes the minimum value of the required purge amount when the rotational speed of the air pump 44 is the first rotational speed N1_min and the DUTY ratio of the purge valve 45 is the low flow basic DUTY ratio D1. In addition, when the pump rotational speed is set to the first rotational speed N1_min and the purge valve 45 is fully opened, the purge amount is set to be equal to or greater than the maximum required purge amount (reference purge amount Qp1) in the low flow rate region B1. One rotation speed N1_min and a low flow basic DUTY ratio are set. Therefore, even if the required purge amount suddenly increases from the minimum amount to the maximum amount (reference purge amount Qp1) in the low flow rate region B1, the purge amount is quickly made the required purge amount by correcting the DUTY ratio of the purge valve 45. Can be changed.

(4) Modification In the above embodiment, the basic DUTY ratio in the low flow rate region B1 has been described as being constant regardless of the required purge amount. However, the basic DUTY ratio indicates that the opening degree of the purge valve 45 is fully closed and fully open. Any intermediate value may be used as long as the intermediate opening is between, and it may be set to change according to the required purge amount. For example, the basic DUTY ratio may be set to be proportional to the required purge amount. However, if the basic DUTY ratio in the low flow rate region B1 is constant regardless of the required purge amount, the DUTY ratio of the purge valve 45 does not need to be changed frequently, and the control configuration can be simplified.

  Further, the combustion mode in the low flow rate region B1 is not limited to the above. However, when the lean CI combustion is performed in the region B1 as described above, appropriate combustion can be realized by appropriately controlling the air-fuel ratio, and a high effect can be obtained.

  Moreover, it is good also considering the whole operation area | region as the low flow volume area | region B1 (area | region where control of step S11-S13 is implemented). That is, in FIG. 3, steps S8 and S10 may be omitted.

1 Engine body 2a Cylinder 42 Canister 43 Purge pipe (Purge passage)
44 Air pump (pump)
45 Purge valve 60 ECU (control means)

Claims (4)

A cylinder, an intake passage for introducing air into the cylinder, a fuel tank in which fuel is stored, and a canister that detachably adsorbs the evaporated fuel generated in the fuel tank, and the evaporated fuel removed from the canister An internal combustion engine evaporative fuel control device in which a purge gas containing is introduced into an intake passage,
A purge passage communicating the canister and the intake passage;
A purge valve provided in the purge passage for opening and closing the passage;
A rotary pump that is provided in the purge passage and increases the pressure difference between the upstream end and the downstream end of the purge passage as the rotational speed increases;
Control means for controlling the opening of the purge valve and the rotational speed of the pump,
The control means includes
At least in a specific operation region, the opening of the purge valve is controlled to an intermediate opening between the fully closed and fully opened, and the target is set higher as the required purge amount, which is the amount of purge gas required, increases. While controlling the number of revolutions of the pump to the number of revolutions of the pump and when the deviation between the number of revolutions of the pump and the target number of revolutions of the pump is equal to or larger than a predetermined reference deviation, the time until the deviation becomes less than the reference deviation And evaporating the internal combustion engine, wherein the opening of the purge valve is corrected in accordance with the required purge amount and the rotational speed of the pump so that the amount of purge gas introduced into the intake passage becomes the required purge amount. Fuel control device. An evaporative fuel control device for an internal combustion engine according to claim 1,
The target pump speed and the intermediate opening are respectively supplied to the intake passage when the pump speed is set to the minimum speed of the target pump speed in the specific operation region and the purge valve is fully opened. The amount of purge gas is equal to or greater than the amount of purge gas supplied to the intake passage when the pump rotational speed is set to the maximum rotational speed of the target pump rotational speed in the specific operating region and the purge valve is set to the intermediate opening. An evaporative fuel control device for an internal combustion engine, characterized in that An evaporative fuel control device for an internal combustion engine according to claim 1 or 2,
The evaporative fuel control device for an internal combustion engine, wherein the intermediate opening is set to a constant opening regardless of the required purge amount. An evaporative fuel control device for an internal combustion engine according to any one of claims 1 to 3,
The evaporative fuel control device for an internal combustion engine, wherein the specific operation region is set to a region where compression self-ignition combustion of an air-fuel ratio greater than 1 is performed in a cylinder.

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