JP3861450B2 - Evaporative fuel treatment system for lean combustion internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an evaporated fuel processing device for an internal combustion engine mounted on an automobile or the like, and more particularly to an evaporated fuel processing device for a lean combustion internal combustion engine.
[0002]
[Prior art]
In an internal combustion engine mounted on an automobile or the like, a lean combustion internal combustion engine capable of burning an air-fuel ratio higher than the stoichiometric air-fuel ratio (oxygen excess state) is being developed in order to reduce fuel consumption. As such a lean combustion internal combustion engine, an in-cylinder injection type internal combustion engine in which a fuel injection valve is attached so that its injection hole faces a combustion chamber is known.
[0003]
In a low-load operation region, a direct injection internal combustion engine introduces fresh air into the combustion chamber during the intake stroke, injects fuel from the fuel injection valve during the subsequent compression stroke, and produces a combustible mixture only near the spark plug. Form. That is, the air-fuel mixture in the combustion chamber is in a so-called stratified state in which the vicinity of the spark plug is a combustible air-fuel mixture layer and the other region is an air layer. The stratified air-fuel mixture is burned using the combustible air-fuel mixture layer near the spark plug as an ignition source.
[0004]
In addition, in the cylinder injection internal combustion engine, in the middle load operation region, fresh air is introduced into the combustion chamber during the intake stroke, and at the same time, fuel is injected from the fuel injection valve. At this time, the amount of fuel injected from the fuel injection valve is such that the amount of fresh air relative to the amount of fuel becomes higher than the stoichiometric air-fuel ratio. In this case, a lean air-fuel mixture in which fuel and fresh air are homogeneously mixed is formed over substantially the entire area in the combustion chamber.
[0005]
Subsequently, in the high load operation region, the direct injection internal combustion engine introduces fresh air into the combustion chamber during the intake stroke and simultaneously injects fuel from the fuel injection valve. At this time, the amount of fuel injected from the fuel injection valve is such that the amount of fresh air with respect to the amount of fuel is substantially the stoichiometric air-fuel ratio. In this case, a stoichiometric mixture in which the fuel and the fresh air are homogeneously mixed is formed over the entire combustion chamber.
[0006]
As described above, the direct injection internal combustion engine can realize lean combustion in the low and medium load operation region, so that fuel consumption can be greatly reduced.
[0007]
On the other hand, the internal combustion engine is provided with an evaporative fuel processing device for processing evaporative fuel generated in a fuel tank or the like. This evaporative fuel processing device has a charcoal canister that temporarily stores evaporative fuel generated in a fuel tank, an air introduction passage that introduces air into the charcoal canister, and an intake pipe negative pressure that is generated in an intake passage downstream of the throttle valve. It comprises a negative pressure introduction passage for introducing into the charcoal canister and a flow rate control valve for adjusting the flow rate in the negative pressure introduction passage.
[0008]
In the evaporated fuel processing apparatus configured as described above, when the flow rate control valve is closed, the evaporated fuel generated in the fuel tank is adsorbed by an adsorbent such as activated carbon incorporated in the charcoal canister. When the flow control valve is opened, the intake pipe negative pressure generated in the intake passage is applied to the charcoal canister through the negative pressure introduction passage, and the atmosphere is sucked into the charcoal canister from the atmosphere introduction passage, The air sucked into the charcoal canister is sucked into the intake passage through the negative pressure introduction passage. In other words, an atmospheric flow that flows through the charcoal canister is generated.
The evaporative fuel adsorbed by the adsorbent is desorbed by the above-described atmospheric flow, and guided to the intake passage together with the atmosphere. The evaporated fuel and the air guided to the intake passage are introduced into the combustion chamber of the internal combustion engine while being mixed with fresh air from the upstream of the intake passage, and are burned and processed together with the fuel injected from the fuel injection valve.
[0009]
When such a fuel vapor processing apparatus is applied to a direct injection internal combustion engine, if the direct injection internal combustion engine is in a stratified combustion operation state, the vaporized fuel and the intake air are mixed and supplied into the combustion chamber. The combustion chamber may not be stratified and combustion may become unstable.
[0010]
In order to solve such a problem, a cylinder injection type internal combustion engine described in JP-A-4-194354 is known. This direct injection internal combustion engine supplies evaporated fuel to the intake passage only when the engine load is larger than a predetermined authorized load. That is, only when the internal combustion engine is in the homogeneous combustion operation state, the evaporated fuel is supplied to the intake passage, and the evaporated fuel is processed without making the combustion unstable.
[0011]
[Problems to be solved by the invention]
By the way, in a cylinder injection type internal combustion engine, the throttle valve is substantially fully opened in most of the operation region except during extremely low load operation in order to reduce drive loss due to the pumping action of intake air. Intake pipe negative pressure is less likely to occur in the intake pipe. For this reason, it is difficult to form an air flow that flows through the charcoal canister, and it is difficult to introduce a large amount of the evaporated fuel in the charcoal canister into the intake system.
[0012]
On the other hand, when the throttle valve is controlled to be closed in order to increase the intake pipe negative pressure in an in-cylinder injection type internal combustion engine, the negative pressure level of the intake pipe negative pressure increases, and the flow rate of the air flowing through the canister increases. As a result, the amount of evaporated fuel supplied to the internal combustion engine increases rapidly, and the combustion state of the internal combustion engine may become unstable.
[0013]
The present invention has been made in view of the above-described problems, and in an internal combustion engine in which a slot valve is substantially fully opened in most operating regions, such as an in-cylinder injection internal combustion engine, An object of the present invention is to provide a technique capable of increasing the purge amount of the evaporated fuel while stabilizing the combustion state of the engine.
[0014]
[Means for Solving the Problems]
The present invention employs the following means in order to solve the above-described problems.
[0015]
That is, an evaporative fuel processing apparatus for an internal combustion engine according to the present invention includes a lean combustion internal combustion engine capable of combusting an oxygen-rich mixture,
A purge passage that guides the evaporated fuel generated in a fuel tank attached to the lean combustion internal combustion engine to an intake passage of the lean combustion internal combustion engine;
A flow rate control valve for adjusting the flow rate of the purge passage;
Combustion state determination means for determining whether or not the combustion state of the lean combustion internal combustion engine is stable when performing purge of evaporated fuel;
Differential pressure changing means for changing the pressure difference between the upstream and downstream of the purge passage;
Purge control means for adjusting the amount of evaporated fuel introduced from the purge passage to the intake passage by controlling at least the differential pressure changing means according to the combustion state of the lean combustion internal combustion engine when purging the evaporated fuel;
It is characterized by providing.
[0016]
In the evaporated fuel processing apparatus configured as described above, when the flow control valve is opened, the evaporated fuel generated in the fuel tank is introduced into the intake passage through the purge passage, so-called evaporated fuel purge is performed. Is called. At this time, the purge control means controls at least the differential pressure changing means according to the combustion state determined by the combustion state determination means, and adjusts the amount of evaporated fuel introduced from the purge passage to the intake passage.
[0017]
In this case, the amount of evaporated fuel introduced from the purge passage to the intake passage is adjusted so that the combustion state of the lean combustion internal combustion engine does not become unstable, and as a result, the combustion state of the lean combustion internal combustion engine does not become unstable. As a result, the purge amount of the evaporated fuel is increased.
[0018]
When adjusting the purge amount of the evaporated fuel, the purge control means, for example, controls the differential pressure changing means to increase the pressure difference between the upstream and downstream of the purge passage as long as the combustion state is stable. The amount of evaporated fuel introduced from the passage to the intake passage may be increased.
[0019]
When the combustion state determining unit determines that the combustion state of the lean combustion internal combustion engine is unstable, the purge control unit includes a differential pressure changing unit to reduce the pressure difference between the upstream and downstream of the purge passage. The amount of evaporated fuel introduced from the purge passage to the intake passage may be reduced by control.
[0020]
In this case, the purge amount of the evaporated fuel is continuously increased as long as the combustion state of the lean combustion internal combustion engine is stable. When the combustion state of the lean combustion internal combustion engine becomes unstable, the purge amount is reduced, and the combustion state of the lean combustion internal combustion engine is stabilized. As a result, the purge amount of the evaporated fuel becomes the maximum amount within a range in which the combustion state of the lean combustion internal combustion engine does not become unstable, and both the stabilization of the combustion state of the lean combustion internal combustion engine and the securing of the purge amount of the evaporated fuel are compatible. Is done.
[0021]
Further, in order to purge more evaporated fuel within a range where the combustion state of the lean combustion internal combustion engine does not become unstable, it is desirable to finely adjust the purge amount in the vicinity of the limit region of the purge amount.
[0022]
Accordingly, when the purge control means determines that the combustion state is unstable by the combustion state determination means at the time of purging the evaporated fuel, the differential pressure is maintained to maintain the pressure difference between the upstream and downstream of the purge passage at that time. While controlling the changing means, the opening degree of the flow control valve may be corrected by a predetermined amount in the closing direction.
[0023]
The purge control means corrects the opening degree of the flow control valve by a predetermined amount in the closing direction and then determines the opening degree of the flow control valve when the combustion state determination means determines that the combustion state is stable. You may make it correct | amend in an opening direction with the correction amount less than fixed_quantity | quantitative_assay.
[0024]
On the other hand, the purge control means corrects the pressure difference between the upstream and downstream of the purge passage when the combustion state determining means determines that the combustion state is unstable after correcting the opening of the flow control valve by a predetermined amount in the closing direction. The differential pressure changing means may be controlled so as to reduce the pressure.
[0025]
Further, the purge control means controls the flow rate control valve so as to maintain the opening degree at that time when the combustion state determination means determines that the combustion state is unstable when purging the evaporated fuel, and the purge passage The differential pressure changing means may be controlled so as to reduce the pressure difference between the upstream side and the downstream side.
[0026]
Then, the purge control means reduces the pressure difference between the upstream and downstream of the purge passage, and if the combustion state determination means determines that the combustion state is stable, opens the flow control valve in the opening direction. A predetermined amount may be corrected.
[0027]
On the other hand, if the purge control means determines that the combustion state is unstable by the combustion state determination means after reducing the pressure difference between the upstream and downstream of the purge passage, the pressure difference between the upstream and downstream of the purge passage The differential pressure changing means may be controlled to further reduce the pressure.
[0028]
In short, the purge control means roughly adjusts the amount of evaporated fuel introduced from the purge passage to the intake passage by controlling the differential pressure changing means, and controls the flow rate control valve from the purge passage to the intake passage. It is preferable to finely adjust the amount of evaporated fuel introduced into the tank.
[0029]
Further, as the differential pressure changing means, the first opening that is substantially fully opened in the normal operation region is maintained, and the second opening that is closed from the first opening when purging is performed. Examples thereof include a throttle valve to be controlled and a positive pressure pump that sends out air at a desired pressure from upstream to downstream of the purge passage.
[0030]
Further, the purge control means may control the differential pressure changing means to return the pressure difference between the upstream and downstream of the purge passage to the normal pressure difference when the operating state of the internal combustion engine is changed. This is because when the internal combustion engine shifts from a non-idle state to an idle state during purge execution, when it shifts from a homogeneous combustion state to a stratified combustion state, or when the amount of evaporated fuel to be purged decreases, etc. Based on the knowledge of the inventor that the combustion state can be stabilized and the drive loss due to the pumping action of the intake air can be suppressed by returning the pressure difference between the upstream side and the downstream side to the normal pressure difference. .
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of an evaporated fuel processing apparatus for an internal combustion engine according to the present invention will be described below with reference to the drawings.
[0032]
<Embodiment 1>
FIG. 1 is a schematic configuration diagram of an internal combustion engine to which an evaporative fuel processing apparatus for a lean combustion internal combustion engine according to the present invention is applied. An internal combustion engine 1 shown in FIG. 1 is a four-cycle in-cylinder injection internal combustion engine that includes a plurality of cylinders 2 and includes a fuel injection valve 9 that directly injects fuel into each cylinder 2.
[0033]
The internal combustion engine 1 includes a cylinder block 1b in which a plurality of cylinders 2 and a cooling water channel 1c are formed, and a cylinder head 1a fixed to an upper portion of the cylinder block 1b.
[0034]
A crankshaft 4 that is an engine output shaft is rotatably supported on the cylinder block 1b, and the crankshaft 4 is connected to a piston 3 that is slidably loaded in each cylinder 2.
[0035]
A combustion chamber 5 surrounded by the top surface of the piston 3 and the cylinder head 1a is formed above the piston 3. The cylinder head 1 a is attached with a drop-down plug 6 so as to face the combustion chamber 5, and an igniter 6 a for applying a drive current to the drop-down plug 6 is connected to the drop-down plug 6. .
[0036]
Subsequently, the cylinder head 1 a is formed such that the open ends of the two intake ports 7 and the two exhaust ports 8 face the combustion chamber 5, and the fuel injection is performed so that the nozzle holes face the combustion chamber 5. A valve 9 is attached.
[0037]
The open ends of the intake / exhaust ports 7 and 8 are opened and closed by an intake valve 70 and an exhaust valve 80 that are supported by the cylinder head 1a so as to advance and retreat. The intake and exhaust valves 70 and 80 rotate around the cylinder head 1a. It is driven forward and backward by an intake camshaft 11 and an exhaust camshaft 12 that are freely supported.
[0038]
The intake side camshaft 11 and the exhaust side camshaft 12 are connected to the crankshaft 4 via a timing belt (not shown), and the rotational force of the crankshaft 4 is connected to the intake side camshaft 11 and the above described via the timing belt. It is transmitted to the exhaust side camshaft 12.
[0039]
One of the two intake ports 7 communicating with each cylinder 2 has a flow path formed linearly from an open end formed on the outer wall of the cylinder head 1a toward an open end facing the combustion chamber 5. The other intake port 7 is a helical port having a flow path formed so as to swivel from the open end of the outer wall of the cylinder head 1 a toward the open end of the combustion chamber 5.
[0040]
Each intake port 7 communicates with each branch pipe of an intake branch pipe 16 attached to the cylinder head 1a. A swirl control valve 10 that adjusts the flow rate in the branch pipe is provided in the branch pipe communicating with the straight port of the two intake ports 7. The swirl control valve 10 is composed of a step motor or the like, and an actuator 10a that opens and closes the swirl control valve 10 according to an applied current is attached.
[0041]
The intake branch pipe 16 is connected to a surge tank 17, and the surge tank 17 is connected to an air cleaner box 19 via an intake pipe 18. A vacuum sensor 20 for outputting an electrical signal corresponding to the pressure in the surge tank 17 is attached to the surge tank 17.
[0042]
A throttle valve 21 for adjusting the flow rate in the intake pipe 18 is attached to the intake pipe 18. The throttle valve 21 is composed of a step motor or the like, and an actuator 22 that opens and closes the throttle valve 21 according to an applied current is attached.
[0043]
The throttle valve 21 is provided with a throttle position sensor 23 that outputs an electrical signal corresponding to the opening of the throttle valve 21 and an accelerator lever (not shown) that rotates in conjunction with the accelerator pedal 24. .
[0044]
An accelerator position sensor 25 that outputs an electrical signal corresponding to the rotation position of the accelerator lever (the amount of depression of the accelerator pedal 24) is attached to the accelerator lever.
[0045]
An air flow meter 26 that outputs an electric signal corresponding to the mass of fresh air (intake air mass) flowing through the intake pipe 18 is attached to the intake pipe 18 upstream of the throttle valve 21.
[0046]
On the other hand, each exhaust port 8 communicates with each branch pipe of an exhaust branch pipe 27 attached to the cylinder head 1 a, and the exhaust branch pipe 27 is connected to an exhaust pipe 29 via a first catalyst 28. The exhaust pipe 29 is connected to a muffler (not shown) downstream. A first air-fuel ratio sensor 30 that outputs an electric signal corresponding to the air-fuel ratio of the exhaust gas flowing through the exhaust branch pipe 27 is attached to the exhaust branch pipe 27.
[0047]
A second catalyst 31 is provided in the middle of the exhaust pipe 29, and the exhaust pipe 29 downstream of the second catalyst 31 corresponds to the air-fuel ratio of the exhaust gas flowing out from the second catalyst 31. A second air-fuel ratio sensor 32 that outputs an electrical signal is attached.
[0048]
The first catalyst 28 is a three-way catalyst having a smaller capacity than the second catalyst 31, and the second catalyst 31 is a three-way catalyst, a nitrogen oxide storage reduction catalyst, or the like.
[0049]
Next, the internal combustion engine 1 is provided with a fuel tank 33 and a charcoal canister 34 for temporarily storing the evaporated fuel generated in the fuel tank 33. The fuel tank 33 and the charcoal canister 34 are connected to each other through an evaporative fuel passage 35. A flow path in the evaporative fuel passage 35 is provided in the middle of the evaporative fuel passage 35 in accordance with the pressure in the fuel tank 33. A tank internal pressure control valve 36 that opens and closes is attached.
[0050]
The tank internal pressure control valve 36 is configured by combining a positive pressure valve and a negative pressure valve. The positive pressure valve opens when the pressure in the fuel tank 33 increases due to an increase in evaporated fuel, and the negative pressure valve When the pressure in the fuel tank 33 decreases due to the decrease, the valve opens. An atmospheric air introduction passage 37 is connected to the charcoal canister 34, and this atmospheric introduction passage 37 is connected to the intake pipe 18 positioned between the air flow meter 26 and the throttle valve 21.
[0051]
Further, a negative pressure introduction passage 38 is connected to the charcoal canister 34, and the negative pressure introduction passage 38 is connected to the intake pipe 18 downstream of the throttle valve 21. An electromagnetic valve 39 as a flow rate control valve for adjusting the flow rate in the negative pressure introduction passage 38 is attached in the middle of the negative pressure introduction passage 38.
[0052]
The atmospheric introduction passage 37 and the negative pressure introduction passage 38 that communicate with each other via the charcoal canister 34 realize a purge passage according to the present invention (hereinafter, the charcoal canister 34, the atmospheric introduction passage 37, and the negative pressure introduction passage 38 are generically named). (Referred to as purge passage 49).
[0053]
The internal combustion engine 1 is also provided with an electronic control unit (ECU) 40 for engine control. The ECU 40 includes a vacuum sensor 20, a throttle position sensor 23, an accelerator position sensor 25, an air flow meter. 26, the first air-fuel ratio sensor 30 and the second air-fuel ratio sensor 32, a timing rotor 13a attached to the end of the crankshaft 4, and an electromagnetic pickup 13b attached to the cylinder block 1b in the vicinity of the timing rotor 13a Various sensors such as a crank position sensor 13 and a water temperature sensor 14 attached to the cylinder block 1b are connected to each other via electric wiring so as to detect the temperature of the cooling water flowing in the cooling water passage 1c of the cylinder block 1b.
[0054]
Furthermore, an igniter 6a, a fuel injection valve 9, an actuator 10a, an actuator 22, an electromagnetic valve 39, and the like are connected to the ECU 40 through electric wiring.
[0055]
The ECU 40 determines the operating state of the internal combustion engine 1, the evaporated fuel adsorption state of the charcoal canister 34, and the like using the output signals from the various sensors as parameters, and according to the determination results, the igniter 6a, the fuel injection valve 9, and the actuator 10a. Various controls of the actuator 22 and the electromagnetic valve 39 are performed.
[0056]
Here, as shown in FIG. 2, the ECU 40 includes a CPU 42, a ROM 43, a RAM 44, a backup RAM 45, an input port 46, and an output port 47 that are connected to each other by a bidirectional bus 41, and the input port 46. A / D converter (A / D) 48 connected to the.
[0057]
The input port 46 receives signals output from the crank position sensor 13, the throttle position sensor 23, and the accelerator position sensor 25 and transmits the output signals to the CPU 42 or the RAM 44. Further, the input port 46 receives signals output from the water temperature sensor 14, the vacuum sensor 20, the air flow meter 26, and the first and second air-fuel ratio sensors 30 and 32 via the A / D 48, and outputs them. The signal is transmitted to the CPU 42 or the RAM 44.
[0058]
The output port 47 outputs a control signal output from the CPU 42 to the igniter 6a, the fuel injection valve 9, the actuator 10a, the actuator 21, or the electromagnetic valve 39.
[0059]
The ROM 43 performs a fuel injection amount control routine for determining a fuel injection amount, a fuel injection timing control routine for determining fuel injection timing, an ignition timing control routine for determining ignition timing, or a purge of evaporated fuel. Application programs such as a purge execution control routine for execution, various control maps, and the like are stored.
[0060]
The control map is, for example, a fuel injection amount control map showing the relationship between the operating state of the internal combustion engine 1 and the fuel injection amount, a fuel injection timing control map showing the relationship between the operating state of the internal combustion engine 1 and the fuel injection timing, and the internal combustion engine An ignition timing control map showing the relationship between the operating state of the engine 1 and the ignition timing, a first reference value (upper limit value within an allowable range) for determining the state of combustion fluctuation, and the engine speed of the internal combustion engine 1 These are a first reference value control map showing the relationship, a second reference value control map showing the relationship between the second reference value for determining the state of combustion fluctuation and the engine speed of the internal combustion engine 1, and the like.
[0061]
The RAM 44 stores output signals of the sensors, calculation results of the CPU 42, and the like. The calculation result is, for example, an engine speed calculated from an output signal of the crank position sensor 13. The output signal of each sensor, the calculation result of the CPU 42 and the like are rewritten to the latest data every time the crank position sensor 13 outputs a signal.
[0062]
Subsequently, the RAM 44 is set when the combustion state of the internal combustion engine 1 is unstable ("1" is stored) and reset when the combustion state of the internal combustion engine 1 is stable ("0"). ”Is stored), an area for storing the combustion state identification flag (FDLN) is set.
[0063]
Furthermore, an idle determination flag (FIDL) storage area and a purge idle determination flag (FPIDL) storage area are set in the RAM 44. These idle determination flag (FIDL) storage area and purge idle determination flag (FPDLD) storage area are set when the internal combustion engine 1 is in an idle state ("1" is stored), and when the internal combustion engine 1 is in a non-idle state ("0" is stored).
[0064]
The backup RAM 45 is a non-volatile memory that retains data even after the internal combustion engine 1 is stopped.
[0065]
The CPU 42 operates in accordance with an application program stored in the ROM 43, determines the operating state of the internal combustion engine 1 from the output signals of the sensors, and determines the fuel injection amount and fuel injection timing from the determined operating state and each control map. The ignition timing, the opening / closing timing of the solenoid valve 39, the opening degree (duty ratio) of the solenoid valve 39, and the like are calculated. Then, the CPU 42 outputs a control signal for the igniter 6a, the fuel injection valve 9, the actuator 10a, the actuator 21, or the electromagnetic valve 39 based on the calculation result.
[0066]
For example, when the CPU 42 determines that the operation state of the internal combustion engine 1 is in the low load operation region from the output signals of various sensors, the CPU 42 transmits a control signal to the actuator 10a to realize the stratified combustion, so that the swirl control valve 10 And the throttle valve 21 is substantially fully opened by transmitting a control signal to the actuator 22, and a drive current is applied to the fuel injection valve 9 during the compression stroke of each cylinder 2 to perform the compression stroke injection. Do. In this case, in the combustion chamber 5 of each cylinder 2, a combustible air-fuel mixture layer is formed only in the vicinity of the spark plug 6, and an air layer is formed in other regions, thereby realizing stratified combustion.
[0067]
When determining that the engine operating state is in the medium load operating region, the CPU 42 transmits a control signal to the actuator 10a to reduce the opening of the swirl control valve 10 in order to achieve homogeneous combustion by the lean air-fuel mixture, Further, during the intake stroke of each cylinder 2, a drive current is applied to the fuel injection valve 9 to perform intake stroke injection. In this case, a lean air-fuel mixture in which air and fuel are homogeneously mixed is formed over substantially the entire area in the combustion chamber 5 of each cylinder 2, and homogeneous combustion is realized.
[0068]
If it is determined that the engine operation state is in the high load operation region, the CPU 42 transmits a control signal to the actuator 10a to fully open the swirl control valve 10 in order to realize homogeneous combustion by the air-fuel mixture near the stoichiometric air-fuel ratio. And a control signal is transmitted to the actuator 22 so that the throttle valve 21 has an opening corresponding to the amount of depression of the accelerator pedal (the output signal value of the accelerator position sensor 25), and further, the fuel injection valve 9 during the intake stroke of each cylinder 2 Intake stroke injection is performed by applying a drive current to the. In this case, a stoichiometric air-fuel ratio mixture in which air and fuel are homogeneously mixed is formed over substantially the entire area in the combustion chamber 5 of each cylinder 2 to achieve homogeneous combustion.
[0069]
It should be noted that the CPU 42 is configured to prevent the torque fluctuation of the internal combustion engine 1 during the compression stroke and the intake air when the shift from the stratified combustion control to the homogeneous combustion control or from the homogeneous combustion control to the stratified combustion control. A drive current is applied to the fuel injection valve 9 in two strokes. In this case, in the combustion chamber 5 of each cylinder 2, a combustible air-fuel mixture layer is formed in the vicinity of the spark plug 6, and a lean air-fuel mixture layer is formed in other regions, so-called weak stratified combustion is realized. .
[0070]
Next, the CPU 42 normally performs control so as to close the electromagnetic valve 39 when purging the evaporated fuel. In this state, when the evaporated fuel in the fuel tank 33 increases and the pressure in the fuel tank 33 exceeds a predetermined value, the tank internal pressure control valve 36 is opened, and the evaporated fuel passage 35 becomes conductive. The evaporated fuel in the fuel tank 33 is introduced into the charcoal canister 34 through the evaporated fuel passage 35 and is once adsorbed by an adsorbent such as activated carbon built in the charcoal canister 34.
[0071]
Further, the CPU 42 determines whether or not a purge execution condition for the evaporated fuel is satisfied every predetermined time. As the purge execution condition, for example, the warm-up of the internal combustion engine 1 and the first and second catalysts 28 and 31 is completed, the fuel injection amount from the fuel injection valve 9 is a predetermined amount or more, or the internal combustion engine Examples of the condition include that a predetermined time or more has elapsed after the engine 1 is started.
[0072]
If it is determined that the purge execution condition as described above is satisfied, the CPU 42 opens the electromagnetic valve 39. In this case, the negative pressure introduction passage 38 becomes conductive, and thereby the purge passage 49 becomes conductive.
[0073]
Here, the intake pipe 18 upstream of the throttle valve 21 upstream of the purge passage 49 becomes substantially atmospheric pressure, but the intake pipe 18 downstream of the purge passage 49 downstream of the throttle valve 21 is negative due to the generation of negative intake pipe pressure. Because of the pressure, a pressure difference is generated between upstream and downstream of the purge passage 49.
[0074]
Due to the pressure difference described above, a part of the air flowing in the intake pipe 18 upstream of the throttle valve 21 flows into the purge passage 49 and is guided into the intake pipe 18 downstream of the throttle valve 21. That is, in the purge passage 49, an atmospheric flow that flows through the charcoal canister 34 is generated.
[0075]
At that time, the evaporated fuel adsorbed by the adsorbent in the charcoal canister 34 is desorbed from the adsorbent in response to the atmospheric flow, and is introduced into the intake pipe 18 downstream of the throttle valve 21 together with the atmospheric air. The evaporated fuel thus introduced into the intake pipe 18 is introduced into the combustion chamber 5 while being mixed with fresh air flowing from the upstream inside the intake pipe 18 and combusted together with the fuel injected from the fuel injection valve 9. And processed.
[0076]
By the way, in the internal combustion engine 1, since the throttle valve 21 is substantially fully opened in most operating regions as described above, intake pipe negative pressure is hardly generated in the intake pipe 18 downstream of the throttle valve 21. As a result, the pressure difference between the upstream and downstream sides of the purge passage 49 is reduced, and the flow rate of the atmosphere flowing through the charcoal canister 34 is reduced. Therefore, the evaporated fuel in the charcoal canister 34 may not be completely purged into the intake pipe 18. There is.
[0077]
Therefore, the CPU 42 controls the actuator 22 so that the opening degree of the throttle valve 21 becomes smaller than the normal opening degree when purging the evaporated fuel.
[0078]
In this case, since the amount of fresh air flowing into the intake pipe 18 downstream of the throttle valve 21 decreases, the intake pipe negative pressure increases, and the pressure difference between the upstream and downstream of the purge passage 49 increases. Thus, the throttle valve 21 and the actuator 22 implement the differential pressure changing means according to the present invention.
[0079]
However, if the pressure difference between the upstream and downstream of the purge passage 49 is simply increased by correcting the opening of the throttle valve 21, the mixture in the combustion chamber 5 is changed by the change in the purge amount of the evaporated fuel and the intake air amount. Since the combustion state of the internal combustion engine 1 becomes unstable, the CPU 42 corrects the opening of the throttle valve 21 in accordance with the combustion fluctuation of the internal combustion engine 1.
[0080]
Further, in order to purge more evaporated fuel within a range where the combustion state of the internal combustion engine 1 does not become unstable, it is necessary to finely adjust the purge amount in the vicinity of the limit region of the purge amount. If the pressure difference between the upstream and downstream sides of the purge passage 49 is changed by correcting the opening, the change in the purge amount becomes relatively large, and it is difficult to finely adjust the purge amount.
[0081]
On the other hand, in the present embodiment, the purge amount is roughly adjusted by correcting the opening of the throttle valve 21, and the purge amount is finely adjusted by correcting the opening of the electromagnetic valve 39. Thus, the purge control means according to the present invention is realized by the CPU 42 controlling the throttle valve 21 (actuator 22) and the electromagnetic valve 39.
[0082]
Here, specific processing relating to purge execution control will be described with reference to the timing chart of FIG.
[0083]
The CPU 42 first determines the combustion state of the internal combustion engine 1 when the purge execution condition is satisfied. Examples of the parameters for determining the combustion state of the internal combustion engine 1 include engine speed fluctuation, combustion pressure sensor output signal value, combustion light sensor output signal value, ion current value generated during combustion, and the like. In the present embodiment, the engine speed fluctuation will be described as an example.
[0084]
The engine speed fluctuation is a change amount of the engine speed per unit time, and the CPU 42 determines the engine speed (first engine speed) at a certain time point and the engine speed (first engine speed) after a predetermined time from that time point. 2 is calculated as engine speed fluctuation: DLN.
[0085]
Subsequently, the CPU 42 determines whether or not the engine speed fluctuation DLN is within an allowable range. Specifically, the CPU 42 accesses the first reference value control map in the ROM 43, and calculates the first reference value: DLNS1 corresponding to the engine speed at that time. Then, the CPU 42 compares the engine speed fluctuation: DLN with the first reference value: DLNS1.
[0086]
At this time, if the engine speed fluctuation DLN is equal to or less than the first reference value DLNS1, the CPU 42 considers that the combustion state of the internal combustion engine 1 is stable, and the engine speed fluctuation DLN is first. If it is larger than DLNS1, the combustion state of the internal combustion engine 1 is regarded as unstable. Thus, CPU42 implement | achieves the combustion state determination means concerning this invention.
[0087]
In the example of FIG. 3, since the engine speed fluctuation: DLN is smaller than the first reference value: DLNS1 before the purge is started (left side of (1) in the figure), the CPU 42 is in the combustion state of the internal combustion engine 1. The solenoid valve 39 is driven so that the opening degree becomes the maximum opening degree: MAXDPG ((1) in the figure).
[0088]
At this time, since the purge passage 49 is in a conducting state, an atmospheric flow that flows through the charcoal canister 34 is generated due to a pressure difference between the upstream and downstream of the purge passage 49. Due to this atmospheric flow, the evaporated fuel adsorbed on the adsorbent in the charcoal canister 34 is desorbed from the adsorbent and guided into the intake pipe 18.
[0089]
Subsequently, in order to increase the intake pipe negative pressure downstream of the throttle valve 21, the CPU 42 sets the opening of the throttle valve 21 to a normal opening when purging is not performed (hereinafter referred to as standard opening: TAS). ) To a predetermined opening: an opening (TAS−SΔTA) closed by SΔTA ((2) in the figure).
[0090]
The predetermined opening: SΔTA is a value that is updated whenever the opening of the throttle valve 21 is corrected in the closing direction, and is calculated by adding the predetermined value: ΔTA to the previous SΔTA. When calculating the initial value of the predetermined opening: SΔTA, the previously calculated predetermined opening: SΔTA is regarded as “0”.
[0091]
Further, when the predetermined opening: SΔTA is preset with an upper limit: SΔTAMAX, and the predetermined opening: SΔTA calculated at the time of update becomes larger than the upper limit: SΔTAMAX The upper limit value: SΔTAMAX is used as the predetermined opening: SΔTA.
[0092]
When the opening degree of the throttle valve 21 is corrected in the closing direction by the predetermined opening degree: SΔTA, the amount of fresh air flowing to the intake pipe 18 downstream of the throttle valve 21 is reduced. The degree increases, and the pressure difference between the upstream and downstream of the purge passage 49 increases. As a result, the flow rate of the atmosphere flowing through the charcoal canister 34 increases, and the amount of evaporated fuel introduced from the charcoal canister 34 to the intake pipe 18 also increases.
[0093]
On the other hand, when the amount of evaporated fuel introduced into the intake pipe 18 increases, the state of the air-fuel mixture supplied to the combustion chamber 5 changes, and the engine speed fluctuation: DLN becomes larger than before the purge is executed. The engine speed fluctuation: DLN is calculated again after a predetermined time has elapsed from the time when the opening degree of the valve 21 is corrected in the closing direction, and the calculated engine speed fluctuation: DLN is compared with the first reference value: DLNS1.
[0094]
At this time, if the engine speed fluctuation: DLN is equal to or less than the first reference value: DLNS1, the CPU 42 updates the predetermined opening: SΔTA, and updates the standard opening: TAS after updating the predetermined opening: Subtract SΔTA to calculate a new opening: TA. Then, the CPU 42 controls the actuator 22 so that the opening of the throttle valve 21 becomes a new opening: TA. In this case, the throttle valve 21 is further driven in the closing direction by ΔTA. Such correction of the opening degree of the throttle valve 21 in the closing direction is repeated as long as the engine speed fluctuation: DLN is equal to or less than the first reference value: DLNS.
[0095]
When the opening degree correction in the closing direction of the throttle valve 21 is repeated, the engine speed fluctuation: DLN becomes larger than the first reference value: DLNS1 ((3) in the figure), the CPU 42 determines the combustion state of the internal combustion engine 1 Is written to the combustion state identification flag (FDLN) storage area of the RAM 44.
[0096]
Further, the CPU 42 cancels the opening degree correction in the closing direction of the throttle valve 21 and maintains the opening degree of the throttle valve 21 at that time: TA (TA = TAS−ΔSTAMAX in the example of FIG. 3). 22 is controlled.
[0097]
And CPU42 performs the following processes in order to suppress engine speed fluctuation: DLN.
[0098]
First, the CPU 42 corrects the opening degree of the electromagnetic valve 39 by a predetermined amount: ΔDPG in the closing direction so as to slightly reduce the purge amount of the evaporated fuel. In this case, since the flow path of the purge passage 49 is narrowed, the amount of evaporated fuel introduced into the internal combustion engine 1 is reduced, and the engine speed fluctuation: DLN is reduced.
[0099]
After correcting the opening degree of the electromagnetic valve 39 in the closing direction, the CPU 42 determines whether or not the combustion state of the internal combustion engine 1 has become stable. Specifically, the CPU 42 calculates the engine speed fluctuation DLN after correcting the opening degree of the electromagnetic valve 39 and accesses the second reference value control map of the ROM 43 to obtain the engine speed at that time. The corresponding second reference value: DLNS2 is calculated. Then, the CPU 42 compares the engine speed fluctuation: DLN with the second reference value: DLNS2 ((4) in the figure).
[0100]
Here, the second reference value: DLNS2 is a value obtained by adding a sufficient margin to the first reference value: DLNS, and is set to be smaller than the first reference value: DLNS1. If the DLN is equal to or less than the second reference value DLNS2, the CPU 42 can consider that the combustion state of the internal combustion engine 1 is sufficiently stable.
[0101]
In the example of FIG. 3, since the engine speed fluctuation: DLN is smaller than the second reference value: DLNS2 at time (4) in the figure, the CPU 42 determines that the combustion state of the internal combustion engine 1 is sufficiently stable. Therefore, the opening degree of the electromagnetic valve 39 is slightly corrected in the opening direction in order to increase the purge amount of the evaporated fuel again. The correction amount in this case is an amount obtained by adding a positive number: K less than “1” to a predetermined amount: ΔDPG (= K · ΔDPG), and is an amount smaller than the predetermined amount: ΔDPG. Such correction of the opening degree of the electromagnetic valve 39 in the opening direction is repeated as long as the engine speed fluctuation: DLN is equal to or less than the second reference value: DLNS2 ((5) to (6) in the figure).
[0102]
When the opening degree of the electromagnetic valve 39: DPG reaches the maximum opening degree: MAXDPG by repeating the opening degree correction of the electromagnetic valve 39 in the opening direction, the CPU 42 corrects the opening degree of the electromagnetic valve 39 in the opening direction. Then, the combustion state identification flag (FDDLN) storage area of the RAM 44 is accessed and "0" is written ((6) in the figure). Then, the CPU 42 restarts the opening degree correction in the closing direction of the throttle valve 21.
[0103]
On the other hand, when the engine speed fluctuation: DLN does not become equal to or less than the second reference value: DLNS2 at (4) in FIG. 3, the combustion of the internal combustion engine 1 is corrected by correcting the opening of the electromagnetic valve 39 in the closing direction. If the state is not stable, the CPU 42 further corrects the opening degree of the electromagnetic valve 39 by a predetermined amount: ΔDPG in the closing direction, as shown in the timing chart of FIG.
[0104]
After a predetermined time has elapsed from when the opening degree of the solenoid valve 39 is corrected by a predetermined amount: ΔDPG ((4) ′ in the figure), the CPU 42 calculates the engine speed fluctuation: DLN, and calculates the calculated engine speed. Number variation: DLN and second reference value: DLNS2 are compared again.
[0105]
At this time, if the engine speed fluctuation: DLN is larger than the second reference value: DLNS2, the CPU 42 further corrects the opening degree of the electromagnetic valve 39 by a predetermined amount: ΔDPG in the closing direction. At the middle (4) ', since the engine speed fluctuation: DLN is smaller than the second reference value: DLNS2, it is considered that the combustion state of the internal combustion engine 1 is sufficiently stable, and the opening of the solenoid valve 39 Is corrected in the opening direction by a predetermined amount: K · ΔDPG.
[0106]
As described above, by adjusting the purge amount of the evaporated fuel according to the combustion state of the internal combustion engine 1, the purge amount can be increased within a range in which the combustion state does not become unstable.
[0107]
When the internal combustion engine 1 shifts from the non-idle state to the idle state during the purge execution, or when the internal combustion engine 1 shifts from the homogeneous combustion state to the stratified combustion state, the CPU 42 opens the opening degree TA of the throttle valve 21 as a standard opening. Degree: Return to TAS to stabilize the combustion state and suppress drive loss due to the pumping action of intake air.
[0108]
Further, when the amount of evaporated fuel to be purged decreases, the CPU 42 immediately returns the opening degree TA of the throttle valve 21 to the standard opening degree TAS, and stops normal purge control or purge execution. Good. Here, when the amount of evaporated fuel decreases, for example, when it is detected that the concentration of evaporated fuel has dropped below a predetermined concentration, the amount of evaporated fuel adsorbed in the charcoal canister 34 has decreased below a predetermined amount. For example, it is possible to detect such a situation.
[0109]
Hereinafter, the operation and effect of the present embodiment will be described.
[0110]
The CPU 42 executes an idle determination routine shown in FIG. 5 and a purge execution control routine shown in FIG. 6 every predetermined time.
[0111]
First, in the idle determination routine, the CPU 42 inputs an output signal of the accelerator position sensor 25 in S501, and determines whether or not the depression amount of the accelerator pedal 24 is “0”, that is, whether or not the accelerator is in an off state. To do.
[0112]
If it is determined in S501 that the depression amount of the accelerator pedal 24 is “0”, the CPU 42 regards the internal combustion engine 1 as being in an idle state, and proceeds to S502.
[0113]
In S502, the CPU 42 accesses the idle determination flag (FIDL) storage area of the RAM 44, and determines whether “1” is stored.
[0114]
If it is determined in S502 that “1” has already been stored in the idle determination flag (FIDL) storage area of the RAM 44, the CPU 42 once ends the execution of this routine.
[0115]
On the other hand, if it is determined in S502 that “0” is stored in the idle determination flag (FIDL) storage area, the CPU 42 proceeds to S503 and writes “1” in the idle determination flag (FIDL) storage area. .
[0116]
Subsequently, the CPU 42 proceeds to S504 and writes “1” in the purge idle determination flag (FPIDL) storage area of the RAM 44. When the execution of the process of S504 is completed, the CPU 42 ends the execution of this routine once.
[0117]
If it is determined in S501 that the amount of depression of the accelerator pedal 24 is not "0", the CPU 42 considers that the internal combustion engine 1 is in a non-idle state and proceeds to S505, where the idle determination flag (FIDL) in the RAM 44 is determined. After writing “0” in the storage area, the execution of this routine is temporarily terminated.
[0118]
Next, in the purge execution control routine, the CPU 42 determines whether or not the purge execution condition is satisfied in S601, and when it is determined that the purge execution condition is not satisfied, the execution of this routine is once ended.
[0119]
On the other hand, if it is determined in S601 that the purge execution condition is satisfied, the CPU 42 proceeds to S602 to determine whether or not “1” is stored in the purge idle determination flag (FPIDL) storage area of the RAM 44. .
[0120]
If it is determined in S602 that “0” is stored in the purge idle determination flag (FPIDL) storage area, the CPU 42 considers that the internal combustion engine 1 is in a non-idle state, and proceeds to S605. In S605, the CPU 42 calculates the engine speed fluctuation: DLN at that time.
[0121]
Subsequently, the CPU 42 proceeds to S606, accesses the first reference value control map of the ROM 43, and calculates the first reference value: DLNS1 corresponding to the engine speed at that time. Then, the CPU 42 compares the engine speed fluctuation calculated in S605: DLN and the first reference value: DLNS1.
[0122]
If it is determined in S606 that the engine speed fluctuation: DLN is equal to or less than the first reference value: DLNS1, the CPU 42 regards the combustion state of the internal combustion engine 1 as being stable, and proceeds to S608.
[0123]
If it is determined in S606 that the engine speed fluctuation: DLN is larger than the first reference value: DLNS1, the combustion state of the internal combustion engine 1 is regarded as unstable, and the process proceeds to S607. In S607, the CPU 42 accesses the combustion state identification flag (FDLN) storage area of the RAM 44 and writes “1”.
[0124]
In S606, the CPU 42, which determines that the engine speed variation: DLN is equal to or less than the first reference value: DLNS1, or has completed the processing of S607, proceeds to S608, and the combustion state identification flag (FDDLN) in the RAM 44. The storage area is accessed to determine whether “1” is stored.
[0125]
If it is determined in S608 that “0” is stored in the combustion state identification flag (FDDLN) storage area, the CPU 42 proceeds to S609 and sets the opening degree: DPG of the electromagnetic valve 39 to the maximum opening degree: MAXDPG. Then, a drive pulse signal corresponding to the maximum opening: MAXDPG is applied to the electromagnetic valve 39.
[0126]
At this time, since the purge passage 49 is in a conducting state, the charcoal canister 34 is moved by the pressure difference between the upstream of the purge passage 49 (the intake pipe 18 upstream of the throttle valve 21) and the downstream (the intake pipe 18 downstream of the throttle valve 21). A flowing air flow is generated. Due to the flow of the atmosphere, the evaporated fuel adsorbed in the charcoal canister 34 is desorbed and introduced into the intake pipe 18 downstream of the throttle valve 21 together with the atmosphere, and the purge of the evaporated fuel is started.
[0127]
Next, the CPU 42 proceeds to S610, where the predetermined opening degree previously calculated from a predetermined area of the RAM 44: SΔTA (SΔTA when correcting the opening degree in the closing direction of the throttle valve 21 for the first time after starting the purge execution). = 0), and a predetermined value: ΔTA is added to the predetermined opening: SΔTA to calculate a new predetermined opening: SΔTA (= SΔTA + ΔTA).
[0128]
Subsequently, the CPU 42 proceeds to S611, and subtracts the predetermined opening: SΔTA calculated in S610 from the standard opening: TAS to obtain a new opening: TA (= TAS−SΔ) of the throttle valve 21. TA) is calculated. Then, the CPU 42 controls the actuator 22 so that the actual opening of the throttle valve 21 coincides with the new opening: TA, and the execution of this routine is once ended.
[0129]
In this case, the throttle valve 21 is driven in the closing direction, and the amount of fresh air flowing to the intake pipe 18 downstream of the throttle valve 21 decreases, so the negative pressure level of the intake pipe negative pressure increases. As a result, the pressure difference between the upstream and downstream of the purge passage 49 increases, and the flow rate of the atmosphere flowing through the charcoal canister 34 increases, so the amount of evaporated fuel purged from the charcoal canister 34 to the intake pipe 18 increases. .
[0130]
On the other hand, if it is determined in S608 that “1” is stored in the combustion state identification flag (FDDLN) storage area, the CPU 42 has already purged the evaporated fuel, and the combustion of the internal combustion engine 1 is thereby performed. It is considered that the state is unstable, and the process proceeds to S612.
[0131]
In S612, the CPU 42 determines whether or not the opening degree: DPG of the electromagnetic valve 39 at that time is smaller than the maximum opening degree: MAXDPG, that is, the opening degree of the electromagnetic valve 39 is closed in order to stabilize the combustion state of the internal combustion engine 1. It is determined whether or not the correction has been made.
[0132]
If it is determined in S612 that the opening degree: DPG of the electromagnetic valve 39 is not smaller than the maximum opening degree: MAXDPG (DPG = MAXDPG), the CPU 42 proceeds to S613, where the opening degree of the electromagnetic valve 39: DPG A predetermined amount: ΔDPG is subtracted to calculate a new opening: DPG, and a drive pulse signal corresponding to the new opening: DPG is applied to the electromagnetic valve 39.
[0133]
In this case, since the electromagnetic valve 39 is closed by a predetermined amount: ΔDPG, the flow path of the purge passage 49 is narrowed, and the amount of evaporated fuel introduced from the charcoal canister 34 to the intake pipe 18 is reduced. As a result, the evaporated fuel supplied to the internal combustion engine 1 is reduced, and the engine speed fluctuation of the internal combustion engine 1 is reduced.
[0134]
In S614, the CPU 42 calculates the engine speed fluctuation DLL after correcting the opening degree of the electromagnetic valve 39 in the closing direction, and accesses the second reference value control map in the ROM 43 to access the engine speed at that time. The second reference value: DLNS2 corresponding to is calculated. Then, the CPU 42 stabilizes the combustion state of the internal combustion engine 1 by correcting whether or not the engine speed fluctuation: DLN is equal to or less than the second reference value: DLNS2, that is, the opening degree correction of the electromagnetic valve 39 in the closing direction. It is determined whether or not.
[0135]
When it is determined in S614 that the engine speed fluctuation: DLN is equal to or less than the second reference value: DLNS2, the CPU 42 regards the combustion state of the internal combustion engine 1 as being stable, and proceeds to S615.
[0136]
In S615, the CPU 42 calculates a new opening degree: DPG (= DPG + K · ΔDPG) by adding a predetermined amount: K · ΔDPG to the electromagnetic valve 39 opening degree: DPG at that time. Next, in S616, the CPU 42 determines whether or not the new opening: DPG (= DPG + K · ΔDPG) calculated in S615 is equal to or greater than the maximum opening: MAXDPG.
[0137]
If it is determined in S616 that the opening calculated in S615: DPG (= DPG + K · ΔDPG) is less than the maximum opening: MAXDPG, the CPU 42 corresponds to the opening calculated in S615: DPG. After the drive pulse signal to be applied is applied to the electromagnetic valve 39, execution of this routine is terminated.
[0138]
In this case, since the electromagnetic valve 39 is opened by a predetermined amount: K · ΔDPG, the flow path of the purge passage 49 is slightly expanded, and the amount of evaporated fuel introduced from the charcoal canister 34 to the intake pipe 18 is slightly increased.
[0139]
If it is determined in S616 that the opening calculated in S615: DPG (= DPG + K · ΔDPG) is equal to or greater than the maximum opening: MAXDPG, the CPU 42 proceeds to S617 and sets the maximum opening: MAXDPG to the solenoid valve. A new opening of 39: DPG is considered, and a drive pulse signal corresponding to the maximum opening: MAXDPG is applied to the solenoid valve 39.
[0140]
Subsequently, in S618, the CPU 42 writes “0” in the combustion state identification flag (FDLN) storage area of the RAM 44, and ends the execution of this routine.
[0141]
After that, when this routine is re-executed, if the engine speed fluctuation: DLN is equal to or smaller than the first reference value: DLNS1 in S606, that is, the opening of the solenoid valve 39 is changed to the maximum opening: MAXDPG. If the combustion state of the internal combustion engine 1 is stable thereafter, the CPU 42 determines in S608 that the combustion state identification flag (FDLN) is “0”. And CPU42 restarts the opening degree correction | amendment to the closing direction of the throttle valve 21 in S609-S611.
[0142]
If it is determined in S614 that the engine speed fluctuation: DLN is larger than the second reference value: DLNS2, the CPU 42 proceeds to S619 and further opens the opening of the electromagnetic valve 39 by a predetermined amount: ΔDPG. The drive pulse signal corresponding to the corrected opening: DPG (= DPG−ΔDPG) is applied to the electromagnetic valve 39, and the execution of this routine is terminated.
[0143]
Thereafter, when this routine is re-executed, the CPU 42 determines that “1” is stored in the combustion state identification flag (FDDLN) storage area in S608, and the opening degree DPG of the electromagnetic valve 39 is maximum in S612. Opening degree: It is determined that it is smaller than MAXDPG.
[0144]
The CPU 42 again compares the engine speed fluctuation: DLN and the second reference value: DLNS2 in S614. If the engine speed fluctuation: DLN is larger than the second reference value: DLNS2, the CPU 42 performs electromagnetic processing in S619. The opening degree of the valve 39 is further corrected in the closing direction by a predetermined amount: ΔDPG. If the engine speed fluctuation: DLN is equal to or smaller than the second reference value: DLNS2, the opening degree of the electromagnetic valve 39 is opened in S616 to S618. It will be corrected in the direction.
[0145]
When the internal combustion engine 1 shifts from the non-idle state to the idle state during the execution of the purge, the CPU 42 determines that “1” is stored in the purge idle determination flag (FPIDL) storage area in S602. Become. In this case, the CPU 42 controls the actuator 22 to return the opening degree of the throttle valve 21 to the standard opening degree: TAS in S603, and then writes “0” in the purge idle determination flag (FPIDL) storage area of the RAM 44 in S604. Thereafter, the processing after S605 is executed.
[0146]
That is, when the internal combustion engine 1 shifts from the non-idle state to the idle state during the purge execution, the CPU 42 once performs the purge execution control after returning the opening degree of the throttle valve 21 to the standard opening degree.
[0147]
As described above, the CPU 42 repeatedly executes the purge execution control routine, so that the purge amount of the evaporated fuel becomes the maximum amount within a range where the combustion state of the internal combustion engine 1 does not become unstable. Therefore, according to the present embodiment, stabilization of the combustion state and securing of the maximum purge amount can be achieved at a high level.
[0148]
<Embodiment 2>
A second embodiment of a fuel vapor processing apparatus according to the present invention will be described with reference to the drawings. Here, a configuration different from that of the first embodiment will be described, and description of the same configuration will be omitted.
[0149]
In the first embodiment described above, an example in which the combustion state is stabilized only by correcting the opening of the electromagnetic valve 39 when the combustion state of the internal combustion engine 1 becomes unstable due to the purge of the evaporated fuel has been described. However, in the present embodiment, an example in which the combustion state is stabilized by using both the correction of the opening of the electromagnetic valve 39 and the correction of the opening of the throttle valve 21 will be described.
[0150]
In this case, when the combustion state of the internal combustion engine 1 becomes unstable, the CPU 42 first corrects the opening degree of the electromagnetic valve 39 by a predetermined amount in the closing direction. Thus, when the combustion state is stabilized, the CPU 42 performs control to gradually open the electromagnetic valve 39 as in the first embodiment described above. On the other hand, if the combustion state is not stabilized just by closing the electromagnetic valve 39 by a predetermined amount, the CPU 42 corrects the opening degree of the throttle valve 21 by a predetermined amount to stabilize the combustion state. .
[0151]
Specifically, as shown in FIG. 7, the CPU 42 repeatedly corrects the opening degree of the throttle valve 21 in the closing direction ((3) in the figure), and then the engine speed fluctuation: DLN is the first reference value. When larger than DLNS1, “1” is written in the combustion state identification flag (FDDLN) storage area of the RAM 44, and the opening degree DPG of the electromagnetic valve 39 is corrected in the closing direction by a predetermined amount: ΔDPG.
[0152]
After correcting the opening degree of the solenoid valve 39 in the closing direction (4 in the figure), the CPU 42 compares the engine speed fluctuation: DLN with the second reference value: DLNS2.
[0153]
At this time, if the engine speed fluctuation: DLN is equal to or less than the second reference value: DLNS2, the CPU 42 sets the opening degree of the electromagnetic valve 39 to a predetermined amount: K ·, as in the first embodiment. ΔDPG is corrected in the opening direction, but if the engine speed fluctuation: DLN is greater than the second reference value: DLNS2, the predetermined amount: VΔTA is added to the opening degree TA of the throttle valve 21 at that time New throttle valve 21 opening: TA is calculated. Then, the CPU 42 drives the actuator 22 in order to make the actual throttle valve 21 opening coincide with the new throttle valve 21 opening: TA.
[0154]
In this case, since the opening degree of the throttle valve 21 is changed in the opening direction by a predetermined amount: VΔTA, the amount of fresh air flowing to the intake pipe 18 downstream of the throttle valve 21 is increased, and the negative pressure of the intake pipe negative pressure The degree becomes lower. As a result, the pressure difference between the upstream and downstream of the purge passage 49 is reduced, the amount of evaporated fuel purged from the charcoal canister 34 to the intake pipe 18 is reduced, and the engine speed fluctuation is reduced.
[0155]
The CPU 42 again compares the engine speed fluctuation: DLN and the second reference value: DLNS2 after the predetermined time has elapsed from the time when the opening of the throttle valve 21 is corrected in the opening direction ((4) in the figure), If the engine speed fluctuation: DLN is larger than the second reference value: DLNS2, the CPU 42 further corrects the opening degree of the throttle valve 21 in the opening direction by a predetermined amount: VΔTA. Such correction of the opening degree of the throttle valve 21 in the opening direction is repeated until the engine speed fluctuation: DLN becomes equal to or less than the second reference value: DLNS2.
[0156]
On the other hand, when the engine speed fluctuation becomes equal to or smaller than the second reference value: DLNS2 by correcting the opening of the throttle valve 21 in the opening direction, the CPU 42, as in the first embodiment, The opening degree of the electromagnetic valve 39 is corrected in the opening direction by a predetermined amount: K · ΔDPG.
[0157]
In the present embodiment, when the combustion state becomes unstable, first, the opening of the solenoid valve 39 is corrected in the closing direction. If the combustion state is not stabilized, the throttle valve 21 is opened. In this example, the opening degree of the throttle valve 21 is corrected in the opening direction. If the combustion state is not stabilized, the opening degree of the electromagnetic valve 39 is corrected in the closing direction. You may do it.
[0158]
Hereinafter, the operation and effect of the present embodiment will be described.
[0159]
The CPU 42 executes a purge execution control routine as shown in FIG. 8 every predetermined time. The processing of S801 to S818 of this purge execution control routine is the same as S601 to S618 of the purge execution control routine of FIG.
[0160]
However, in S807, it is determined that “1” is stored in the combustion state identification flag (FDDLN) storage area, and in S814, the engine speed fluctuation after correcting the opening of the solenoid valve 39 in the closing direction: DLN is the first. When it is determined that the reference value of 2 is greater than DLNS2, the CPU 42 regards that the combustion state cannot be stabilized only by correcting the opening of the electromagnetic valve 39, and proceeds to S819.
[0161]
In S819, the CPU 42 calculates a new opening: TA (= TA + VΔTA) by adding a predetermined amount: VΔTA to the opening: TA of the throttle valve 21 at that time. The CPU 42 controls the actuator 22 so that the actual opening of the throttle valve 21 matches the opening calculated in S819: TA (= TA + VΔTA), and the execution of this routine is terminated.
[0162]
In this case, since the throttle valve 21 is opened by a predetermined amount: VΔTA, the amount of fresh air flowing to the intake pipe 18 downstream of the throttle valve 21 is increased, and the intake pipe negative pressure in the intake pipe 18 downstream of the throttle valve 21 is increased. The degree of negative pressure becomes low. As a result, the pressure difference between the upstream and downstream of the purge passage 49 is reduced, and the flow rate of the atmosphere flowing through the charcoal canister 34 is reduced, so that the amount of evaporated fuel introduced from the charcoal canister 34 to the intake pipe 18 is reduced. The engine speed fluctuation becomes smaller.
[0163]
Thereafter, when this routine is re-executed, the CPU 42 determines in S808 that “1” is stored in the combustion state identification flag (FDDLN) storage area, and the opening degree DPG of the electromagnetic valve 39 is maximum in S812. Opening degree: It is determined that it is smaller than MAXDPG, and the process proceeds to S814.
[0164]
In S814, the CPU 42 compares the engine speed fluctuation: DLN and the second reference value: DLNS2, and if the engine speed fluctuation: DLN is equal to or less than the second reference value: DLNS2, the opening degree of the electromagnetic valve 39 is determined. Are executed in the opening direction, the processing of S815 to S818 is executed.
[0165]
On the other hand, if it is determined in S814 that the engine speed fluctuation: DLN is greater than the second reference value: DLNS2, the CPU 42 executes the process of S819 again to further increase the opening degree TA of the throttle valve 21: a predetermined amount: Correct in the opening direction by VΔTA.
[0166]
As described above, when the CPU 42 repeatedly executes the purge execution control routine, the same effects as those of the first embodiment described above can be obtained.
[0167]
<Embodiment 3>
A third embodiment of the fuel vapor processing apparatus according to the present invention will be described with reference to the drawings. Here, a configuration different from that of the first embodiment will be described, and description of the same configuration will be omitted.
[0168]
In the first and second embodiments described above, when the combustion state of the internal combustion engine 1 becomes unstable due to the purge of the evaporated fuel, the opening degree TA of the throttle valve 21 is not returned to the standard opening degree TAS. In the present embodiment, the throttle valve 21 has the opening degree TA: once returned to the standard opening degree TAS to stabilize the combustion state, and then the throttle valve 21 is stabilized. An example of restarting the opening correction in the closing direction of 21 will be described.
[0169]
In this case, when the combustion state of the internal combustion engine 1 becomes unstable during execution of the purge control, the CPU 42 controls the actuator 22 to return the opening degree TA of the throttle valve 21 to the standard opening degree TAS. The electromagnetic valve 39 is controlled so as to maintain the opening degree: DPG at that time.
[0170]
When the combustion state of the internal combustion engine 1 is stabilized by returning the opening degree of the throttle valve 21: TA to the standard opening degree: TAS, the CPU 42 corrects the opening degree: DPG of the electromagnetic valve 39 by a predetermined amount in the opening direction. To increase the purge amount.
[0171]
On the other hand, if the combustion state of the internal combustion engine 1 is not stabilized simply by returning the opening degree of the throttle valve 21 to the standard opening degree, the CPU 42 corrects the opening degree: DPG of the electromagnetic valve 39 by a predetermined amount in the closing direction. Stabilize the combustion state.
[0172]
Specifically, as shown in FIG. 9, the CPU 42 repeatedly corrects the opening degree of the throttle valve 21 in the closing direction ((3) in the figure), and then the engine speed fluctuation: DLN is the first reference value. When larger than DLNS1, “1” is written in the combustion state identification flag (FDDLN) storage area of the RAM 44, and the actuator 22 is controlled to return the opening degree TA of the throttle valve 21 to the standard opening degree TAS.
[0173]
When the opening degree of the throttle valve 21: TA is returned to the standard opening degree: TAS ((3) in FIG. 3), the CPU 42 recalculates the engine speed fluctuation: DLN and compares it with the second reference value: DLNS2. .
[0174]
At that time, if the engine speed fluctuation: DLN is equal to or less than the second reference value: DLNS2, the CPU 42 opens the opening degree: DPG of the electromagnetic valve 39 in the opening direction as in the first embodiment. The predetermined amount: K · ΔDPG is corrected, but in the example of FIG. 9, since the engine speed fluctuation: DLN is larger than the second reference value: DLNS2 at the time of (3) ′ in the figure, the CPU 42 Corrects the opening degree: DPG of the electromagnetic valve 39 by a predetermined amount: ΔDPG in the closing direction.
[0175]
After a predetermined time has elapsed since the opening of the electromagnetic valve 39: DPG was corrected in the closing direction, the CPU 42 compares the engine speed fluctuation: DLN with the second reference value: DLNS2.
[0176]
At this time, if the engine speed fluctuation: DLN is larger than the second reference value: DLNS2, the CPU 42 further corrects the opening degree: DPG of the electromagnetic valve 39 in the closing direction by a predetermined amount: ΔDPG. In the example, since the engine speed: DLN is smaller than the second reference value: DLNS2 at (4) in the figure, the CPU 42 opens the opening degree: DPG of the electromagnetic valve 39 by a predetermined amount: K · ΔDPG. Correct in the direction.
[0177]
Hereinafter, the operation and effect of the present embodiment will be described.
[0178]
The CPU 42 repeatedly executes a purge execution control routine as shown in FIG. 10 every predetermined time. The processing of S1001 to S1011 of this purge execution control routine is the same as the processing of S601 to S611 of the purge execution control routine of FIG.
[0179]
However, if it is determined in S1008 that “1” is stored in the combustion state identification flag (FDDLN) storage area of the RAM 44, the CPU 42 proceeds to S1012 and sets the opening: TA of the throttle valve 21 to the standard opening: Actuator 22 is driven to return to TAS.
[0180]
In this case, since the throttle valve 21 is returned to the standard opening degree TAS, the amount of fresh air flowing into the intake pipe 18 downstream of the throttle valve 21 is greatly increased, and the negative pressure degree of the intake pipe negative pressure is greatly reduced. . As a result, the pressure difference between the upstream and downstream sides of the purge passage 49 is also greatly reduced, the amount of evaporated fuel introduced from the charcoal canister 34 to the intake pipe 18 is greatly reduced, and the engine speed fluctuation: DLN is also significantly reduced. Become.
[0181]
After returning the throttle valve 21 to the standard opening: TAS, the CPU 42 proceeds to S1013, calculates the engine speed fluctuation: DLN, and accesses the second reference value control map in the ROM 43 to obtain the second reference value. : Calculate DLNS2. Then, the CPU 42 compares the engine speed fluctuation: DLN with the second reference value: DLNS2.
[0182]
If it is determined in S1013 that the engine speed fluctuation: DLN is equal to or smaller than the second reference value: DLNS2, the CPU 42 returns the throttle valve 21 to the standard opening: TAS, so that the combustion state of the internal combustion engine 1 changes. It is considered stable and the process proceeds to S1014.
[0183]
In S1014, the CPU 42 calculates a new opening degree: DPG (= DPG + K · ΔDPG) by adding a predetermined amount: K · ΔDPG to the opening degree: DPG of the electromagnetic valve 39 at that time.
[0184]
In S1015, the CPU 42 determines whether or not the opening degree: DPG (= DPG + K · ΔDPG) calculated in S1014 is equal to or larger than the maximum opening degree: MAXDPG.
[0185]
If it is determined in S1015 that the opening degree calculated in S1014: DPG (= DPG + K · ΔDPG) is less than the maximum opening degree: MAXDPG, the CPU 42 determines the opening degree calculated in S1014: DPG (DPG + K After applying the drive pulse signal corresponding to ΔDPG) to the solenoid valve 39, the execution of this routine is temporarily terminated.
[0186]
If it is determined in S1015 that the opening degree calculated in S1014: DPG (= DPG + K · ΔDPG) is equal to or larger than the maximum opening degree: MAXDPG, the CPU 42 sets the maximum opening degree: MAXDPG in the solenoid valve 39 in S1016. A new opening degree: DPG is regarded, and a drive pulse signal corresponding to the maximum opening degree: MAXDPG is applied to the electromagnetic valve 39.
[0187]
Subsequently, the CPU 42 writes “0” in the combustion state identification flag (FDLN) storage area of the RAM 44 in S1017, and then ends the execution of this routine.
[0188]
On the other hand, if it is determined in S1013 that the engine speed fluctuation: DLN is larger than the second reference value: DLNS2, the CPU 42 closes the opening degree: DPG of the electromagnetic valve 39 by a predetermined amount: ΔDPG in S1018. After the correction, the execution of this routine is terminated.
[0189]
In this case, since the electromagnetic valve 39 is closed by a predetermined amount: ΔDPG, the flow path of the purge passage 49 is narrowed, the amount of evaporated fuel introduced from the charcoal canister 34 to the intake pipe 18 is reduced, and the engine speed fluctuation is small. Become.
[0190]
Thereafter, when the CPU 42 re-executes this routine and determines in S1013 that the engine speed fluctuation: DLN is equal to or smaller than the second reference value: DLNS2, the opening degree of the electromagnetic valve 39 is slightly increased in the opening direction. The processing of S1014 to S1017 is executed for correction.
[0191]
As described above, the CPU 42 can repeatedly increase the purge amount of the evaporated fuel within a range in which the combustion state of the internal combustion engine 1 does not become unstable by repeatedly executing the purge execution control routine. In addition, when the combustion state of the internal combustion engine 1 becomes unstable, the opening degree of the throttle valve 21 is immediately returned to the standard opening degree, so that the combustion state is easily stabilized.
[0192]
<Embodiment 4>
A fourth embodiment of a fuel vapor processing apparatus according to the present invention will be described with reference to the drawings. Here, a configuration different from the above-described first embodiment will be described, and description of the same configuration will be omitted.
[0193]
FIG. 11 is a schematic configuration diagram of an internal combustion engine to which the evaporated fuel device according to the present embodiment is applied. In the example of FIG. 11, the upstream of the air introduction passage 37, that is, the upstream of the purge passage 49 is connected to the positive pressure pump 50 instead of the intake pipe 18 upstream of the throttle valve 21.
[0194]
As shown in FIG. 12, the positive pressure pump 50 is connected to an output port 47 of the ECU 40 through an electrical wiring, and sends out atmospheric air having a pressure corresponding to the magnitude of a voltage applied from the ECU 40.
[0195]
In this case, when performing the purge of the evaporated fuel, the CPU 42 changes the applied voltage of the positive pressure pump 50 while maintaining the opening degree of the throttle valve 21 at the normal opening degree so that the upstream side of the purge passage 49 is increased. Adjust the pressure difference with the downstream. Thus, the positive pressure pump 50 implements the differential pressure changing means according to the present invention.
[0196]
The CPU 42 performs rough adjustment of the purge amount by controlling the positive pressure pump 50 while maintaining the opening degree TA of the throttle valve 21: TA at a constant opening degree (for example, standard opening degree: TAS), and the electromagnetic valve 39 is controlled. The purge amount is finely adjusted by controlling.
[0197]
Here, a specific process of the purge execution control in the present embodiment will be described along the timing chart of FIG.
[0198]
When the purge execution condition is satisfied, the CPU 49 calculates the engine speed fluctuation: DLN and the first reference value: DLNS1, and determines whether the engine speed fluctuation: DLN is equal to or less than the first reference value: DLNS1. Is determined.
[0199]
At this time, if the engine speed fluctuation DLN is equal to or less than the first reference value DLNS1, the CPU 42 considers that the combustion state of the internal combustion engine 1 is stable, and the engine speed fluctuation DLN is first. If it is larger than DLNS1, the combustion state of the internal combustion engine 1 is regarded as unstable.
[0200]
In the example of FIG. 13, since the engine speed fluctuation: DLN is smaller than the first reference value: DLNS1 before the purge is started (left side of (1) in the figure), the CPU 42 is in the combustion state of the internal combustion engine 1. The solenoid valve 39 is driven so that the opening degree becomes the maximum opening degree: MAXDPG ((1) in the figure).
[0201]
Subsequently, the CPU 42 applies a predetermined voltage: SΔVP to the positive pressure pump 50 in order to increase the pressure upstream of the purge passage 49 ((2) in the figure). The predetermined voltage: SΔVP is a value that is updated whenever the delivery pressure of the positive pressure pump 50 is increased, and is calculated by adding the predetermined value: ΔVP to the previous predetermined voltage: SΔVP. When the initial value of the predetermined voltage: SΔVP is calculated, the previous predetermined voltage: SΔVP is regarded as “0”.
[0202]
An upper limit value SΔVPMAX is set in advance for the predetermined voltage SΔVP, and when the predetermined voltage SΔVP calculated at the time of update becomes larger than the upper limit value SΔVPMAX, The upper limit value: SΔVPMAX is used as the predetermined voltage: SΔVP.
[0203]
The positive pressure pump 50 to which the predetermined voltage: SΔVP is applied delivers the atmosphere at a pressure corresponding to the predetermined voltage: SΔVP. As described above, since the air sent from the positive pressure pump 50 is introduced upstream of the purge passage 49, the pressure upstream of the purge passage 49 increases. On the other hand, since the intake pipe negative pressure is generated in the intake pipe 18 downstream of the purge passage 49, that is, downstream of the throttle valve 21, the pressure difference between the upstream and downstream of the purge passage 49 becomes large. As a result, the flow rate of the atmosphere flowing through the charcoal canister 34 increases, and the amount of evaporated fuel introduced from the charcoal canister 34 to the intake pipe 18 also increases.
[0204]
As described above, when the amount of evaporated fuel introduced into the intake pipe 18 increases, the state of the air-fuel mixture supplied to the combustion chamber 5 changes, and the engine speed fluctuation: DLN becomes larger than before the purge is executed. The engine speed fluctuation: DLN is calculated again after a predetermined time has elapsed from the time when the predetermined voltage: SΔVP is applied to the positive pressure pump 50, and the calculated engine speed fluctuation: DLN and the first reference value: DLNS1 are calculated. Compare.
[0205]
At this time, if the engine speed fluctuation: DLN is equal to or less than the first reference value: DLNS1, the CPU 42 updates the predetermined voltage: SΔVP to calculate a new applied voltage: VP, and calculates the calculated applied voltage. : VP is applied to the positive pressure pump 50. Such an update process of the applied voltage: VP is repeated as long as the engine speed fluctuation: DLN is equal to or less than the first reference value: DLNS.
[0206]
When the engine voltage fluctuation: DLN becomes greater than the first reference value: DLNS1 ((3) in the figure) by repeating the update process of the applied voltage: VP of the positive pressure pump 50, the CPU 42 determines the combustion state of the internal combustion engine 1. Is written to the combustion state identification flag (FDLN) storage area of the RAM 44. Furthermore, the CPU 42 stops the update process of the applied voltage: VP, and maintains the applied voltage: VP (VP = SΔVPMAX in the example of FIG. 13) at that time.
[0207]
And CPU42 performs the following processes in order to suppress engine speed fluctuation: DLN.
[0208]
First, the CPU 42 corrects the opening degree: DPG of the electromagnetic valve 39 by a predetermined amount: ΔDPG in the closing direction so as to slightly reduce the purge amount of the evaporated fuel. In this case, since the flow path of the purge passage 49 is narrowed, the amount of evaporated fuel introduced into the internal combustion engine 1 is reduced, and the engine speed fluctuation: DLN is reduced.
[0209]
The CPU 42 determines whether or not the combustion state of the internal combustion engine 1 has become stable after correcting the opening degree DPG of the electromagnetic valve 39 in the closing direction. Specifically, the CPU 42 calculates the engine speed fluctuation: DLN after correcting the opening degree of the electromagnetic valve 39: DPG in the closing direction, and the calculated engine speed fluctuation: DLN is the second reference value: DLNS2. It is determined whether or not the following has occurred ((4) in the figure).
[0210]
In the example of FIG. 13, since the engine speed fluctuation: DLN is smaller than the second reference value: DLNS2 at time (4) in the figure, the CPU 42 determines that the combustion state of the internal combustion engine 1 is sufficiently stable. Therefore, in order to increase the purge amount of the evaporated fuel, the opening degree DPG of the electromagnetic valve 39 is corrected by a predetermined amount K · ΔDPG in the opening direction. Such correction of the opening degree of the electromagnetic valve 39 in the opening direction is repeated as long as the engine speed fluctuation: DLN is equal to or less than the second reference value: DLNS2 ((5) to (6) in the figure).
[0211]
When the opening degree correction of the electromagnetic valve 39 in the opening direction is repeated and the opening degree DPG of the electromagnetic valve 39 reaches the maximum opening degree MAXDPG, the CPU 42 ends the opening degree correction of the electromagnetic valve 39 and the RAM 44. The combustion state identification flag (FDLN) storage area is accessed and "0" is written ((6) in the figure). Thereafter, the CPU 42 restarts the update process of the applied voltage: VP.
[0212]
On the other hand, if the engine speed fluctuation: DLN does not become equal to or less than the second reference value: DLNS2 at time (4) in FIG. 13, the CPU 42 sets the solenoid valve 39 as shown in the timing chart of FIG. Opening: DPG is further corrected in the closing direction by a predetermined amount: ΔDPG.
[0213]
The opening of the solenoid valve 39: DPG is closed in a predetermined direction: ΔDPG is corrected. After a predetermined time has elapsed ((4) 'in the figure), the CPU 42 calculates the engine speed fluctuation: DLN and calculates The engine speed fluctuation: DLN and the second reference value: DLNS2 are compared again.
[0214]
At this time, if the engine speed fluctuation: DLN is larger than the second reference value: DLNS2, the CPU 42 further corrects the opening degree: DPG of the electromagnetic valve 39 by a predetermined amount: ΔDPG in the closing direction. In the example of FIG. 14, since the engine speed fluctuation: DLN is smaller than the second reference value: DLNS2 at the time of (4) in the figure, it is considered that the combustion state of the internal combustion engine 1 is sufficiently stable and electromagnetic The opening degree of the valve 39: DPG is corrected in the opening direction by a predetermined amount: K · ΔDPG.
[0215]
As described above, by adjusting the purge amount of the evaporated fuel according to the combustion state of the internal combustion engine 1, the purge amount can be increased within a range in which the combustion state does not become unstable.
[0216]
When the internal combustion engine 1 shifts from the non-idle state to the idle state during the purge execution, or when the internal combustion engine 1 shifts from the homogeneous combustion state to the stratified combustion state, the CPU 42 initially sets the applied voltage: VP of the positive pressure pump 50. Value: Return to ΔVP to stabilize the combustion state.
[0217]
When the amount of evaporated fuel to be purged decreases, the CPU 42 immediately returns the applied voltage: VP of the positive pressure pump 50 to the initial value: ΔVP, and stops normal purge control or purge execution. Also good.
[0218]
Hereinafter, the operation and effect of the present embodiment will be described.
[0219]
The CPU 42 executes an idle determination routine and a purge execution control routine every predetermined time. The idle determination routine is the same as the idle determination routine according to the first embodiment described above, and a description thereof is omitted here.
[0220]
FIG. 15 is a flowchart showing a purge execution control routine according to the present embodiment. In this purge execution control routine, the CPU 42 determines whether or not the purge execution condition is satisfied in S1501, and terminates the execution of this routine if it is determined that the purge execution condition is not satisfied.
[0221]
On the other hand, if it is determined in S1501 that the purge execution condition is satisfied, the CPU 42 proceeds to S1502 and determines whether or not “1” is stored in the purge idle determination flag (FPIDL) storage area of the RAM 44. .
[0222]
If it is determined in S1502 that “0” is stored in the purge idle determination flag (FPDLD) storage area, the CPU 42 considers that the internal combustion engine 1 is in a non-idle state, and proceeds to S1505. In S1505, the CPU 42 calculates the engine speed fluctuation: DLN at that time.
[0223]
Subsequently, the CPU 42 proceeds to S1506, accesses the first reference value control map of the ROM 43, and calculates the first reference value: DLNS1 corresponding to the engine speed at that time. Then, the CPU 42 compares the engine speed fluctuation: DLN calculated in S1505 with the first reference value: DLNS1.
[0224]
If it is determined in S1506 that the engine speed fluctuation: DLN is equal to or less than the first reference value: DLNS1, the CPU 42 considers that the combustion state of the internal combustion engine 1 is stable, and proceeds to S1508.
[0225]
If it is determined in S1506 that the engine speed fluctuation: DLN is greater than the first reference value: DLNS1, the combustion state of the internal combustion engine 1 is regarded as unstable, and the process proceeds to S1507. In S1507, the CPU 42 accesses the combustion state identification flag (FDLN) storage area of the RAM 44 and writes “1”.
[0226]
In S1506, the CPU 42, which determines that the engine speed fluctuation: DLN is equal to or less than the first reference value: DLNS1, or has completed the processing of S1507, proceeds to S1508, and the combustion state identification flag (FDDLN) in the RAM 44 The storage area is accessed to determine whether “1” is stored.
[0227]
If it is determined in S1508 that “0” is stored in the combustion state identification flag (FDDLN) storage area, the CPU 42 proceeds to S1509 and sets the opening degree: DPG of the electromagnetic valve 39 to the maximum opening degree: MAXDPG. Then, a drive pulse signal corresponding to the maximum opening degree: MAXDPG is applied to the electromagnetic valve 39.
[0228]
In S1510, the CPU 42 reads out the previously calculated predetermined voltage: SΔVP from the predetermined area of the RAM 44, adds a predetermined value: ΔVP to the predetermined voltage: SΔVP, and creates a new predetermined voltage: SΔVP ( = SΔVP + VP).
[0229]
In S1511, the CPU 42 sets the predetermined voltage: SΔVP calculated in S1510 as a new applied voltage: VP. Then, the CPU 42 applies a new applied voltage: VP to the positive pressure pump 50, and temporarily ends the execution of this routine.
[0230]
In this case, the applied voltage of the positive pressure pump 50 is increased, and the pressure of the atmosphere sent from the positive pressure pump 50 is increased, so that the pressure difference between the upstream and downstream of the purge passage 49 is increased. As a result, the flow rate of the atmosphere flowing through the charcoal canister 34 increases, and the amount of evaporated fuel purged from the charcoal canister 34 to the intake pipe 18 increases.
[0231]
On the other hand, if it is determined in S1508 that “1” is stored in the combustion state identification flag (FDDLN) storage area, the CPU 42 has already performed the purge of the evaporated fuel, thereby causing the combustion of the internal combustion engine 1 to occur. The state is considered unstable, and the process proceeds to S1512.
[0232]
In S1512, the CPU 42 closes the opening degree DPG of the electromagnetic valve 39 to stabilize whether the opening degree DPG of the electromagnetic valve 39 at that time is smaller than the maximum opening degree MAXDPG, that is, to stabilize the combustion state of the internal combustion engine 1. It is determined whether or not the direction has been corrected.
[0233]
If it is determined in S1512 that the opening degree: DPG of the electromagnetic valve 39 is not smaller than the maximum opening degree: MAXDPG (DPG = MAXDPG), the CPU 42 proceeds to S1513, and the opening degree of the electromagnetic valve 39 at that time: DPG A predetermined amount: ΔDPG is subtracted to calculate a new opening: DPG, and a drive pulse signal corresponding to the new opening: DPG is applied to the electromagnetic valve 39.
[0234]
At this time, since the electromagnetic valve 39 is closed by a predetermined amount: ΔDPG, the flow path of the purge passage 49 becomes narrow, and the amount of evaporated fuel introduced from the charcoal canister 34 to the intake pipe 18 decreases. As a result, the evaporated fuel supplied to the internal combustion engine 1 is reduced, and the engine speed fluctuation of the internal combustion engine 1 is reduced.
[0235]
In S1514, the CPU 42 calculates the engine speed fluctuation: DLN after correcting the opening degree of the electromagnetic valve 39 in the closing direction, and accesses the second reference value control map in the ROM 43 to access the engine speed at that time. The second reference value: DLNS2 corresponding to is calculated. Then, the CPU 42 corrects the combustion state of the internal combustion engine 1 by correcting whether or not the engine speed fluctuation: DLN is equal to or less than the second reference value: DLNS2, that is, by opening the opening of the electromagnetic valve 39 in the closing direction. Determine whether it is stable or not.
[0236]
If it is determined in S1514 that the engine speed fluctuation: DLN is equal to or less than the second reference value: DLNS2, the CPU 42 regards the combustion state of the internal combustion engine 1 as being stable, and proceeds to S1515.
[0237]
In S1515, the CPU 42 calculates a new opening: DPG (= DPG + K · ΔDPG) by adding a predetermined amount: K · ΔDPG to the opening: DPG of the electromagnetic valve 39 at that time. Next, in S1516, the CPU 42 determines whether or not the opening degree: DPG (= DPG + K · ΔDPG) calculated in S1515 is equal to or larger than the maximum opening degree: MAXDPG.
[0238]
If it is determined in S1516 that the opening calculated in S1515: DPG (= DPG + K · ΔDPG) is less than the maximum opening: MAXDPG, the CPU 42 corresponds to the opening calculated in S1515: DPG. After the drive pulse signal to be applied is applied to the electromagnetic valve 39, execution of this routine is terminated.
[0239]
In this case, since the electromagnetic valve 39 is opened by a predetermined amount: K · ΔDPG, the flow path of the purge passage 49 is slightly expanded, and the amount of evaporated fuel introduced from the charcoal canister 34 to the intake pipe 18 is slightly increased.
[0240]
If it is determined in S1516 that the opening degree calculated in S1515: DPG (= DPG + K · ΔDPG) is greater than or equal to the maximum opening degree: MAXDPG, the CPU 42 proceeds to S1517 and sets the maximum opening degree: MAXDPG to the solenoid valve. A new opening of 39: DPG is considered, and a drive pulse signal corresponding to the maximum opening: MAXDPG is applied to the solenoid valve 39.
[0241]
Subsequently, in S1518, the CPU 42 writes “0” in the combustion state identification flag (FDLN) storage area of the RAM 44, and ends the execution of this routine.
[0242]
Thereafter, when this routine is re-executed, if the engine speed fluctuation: DLN is equal to or smaller than the first reference value: DLNS1 in S1506, that is, the opening degree of the electromagnetic valve 39: DPG is changed to the maximum opening degree: MAXDPG. If the combustion state of the internal combustion engine 1 is stable even after the change, the CPU 42 determines that the combustion state identification flag (FDLN) is “0” in S1508. And CPU42 restarts the update process of the applied voltage of the positive pressure pump 50 in S1509-S1511.
[0243]
If it is determined in S1514 that the engine speed variation: DLN is greater than the second reference value: DLNS2, the CPU 42 proceeds to S1519 and further increases the opening degree: DPG of the electromagnetic valve 39 by a predetermined amount: ΔDPG. The correction is made in the closing direction, a drive pulse signal corresponding to the corrected opening degree: DPG (= DPG−ΔDPG) is applied to the electromagnetic valve 39, and the execution of this routine is terminated.
[0244]
Thereafter, when this routine is re-executed, the CPU 42 determines in S1508 that “1” is stored in the combustion state identification flag (FDDLN) storage area, and in S1512, the opening degree of the solenoid valve 39: DPG is the maximum. Opening: It is determined that it is not MAXDPG.
[0245]
Then, the CPU 42 compares the engine speed fluctuation: DLN with the second reference value: DLNS2 again in S1514. If the engine speed fluctuation: DLN is larger than the second reference value: DLNS2, the CPU 42 performs electromagnetic processing in S1519. The opening degree of the valve 39: DPG is further corrected in the closing direction by a predetermined amount: ΔDPG, and if the engine speed fluctuation: DLN is equal to or smaller than the second reference value: DLNS2, the opening degree of the electromagnetic valve 39 in S1516 to S1518 : DPG is corrected by a predetermined amount: K · ΔDPG.
[0246]
On the other hand, when the internal combustion engine 1 shifts from the non-idle state to the idle state during the execution of the purge, the CPU 42 determines that “1” is stored in the purge idle determination flag (FPIDL) storage area in S1502. Become. In this case, the CPU 42 returns the applied voltage: VP of the positive pressure pump 50 to the initial value (= ΔVP) in S1503, and then writes “0” in the purge idle determination flag (FPIDL) storage area of the RAM 44 in S1504. , Processing after S1505 is executed.
[0247]
That is, when the internal combustion engine 1 shifts from the non-idle state to the idle state during the purge execution, the CPU 42 once returns the applied voltage of the positive pressure pump 50 to the initial value and then performs the purge execution control.
[0248]
As described above, the CPU 42 repeatedly executes the purge execution control routine, so that the purge amount of the evaporated fuel becomes the maximum amount within a range where the combustion state of the internal combustion engine 1 does not become unstable. As a result, both the stabilization of the combustion state and the maximum purge amount can be achieved at a high level.
[0249]
<Embodiment 5>
In the above-described fourth embodiment, the example in which the differential pressure changing means is realized only by the positive pressure pump 50 has been described. However, in the present embodiment, the throttle valve 21 and the positive pressure pump 50 are used in combination. An example of realizing the changing means will be described.
[0250]
In this case, the CPU 42 performs rough adjustment of the purge amount by controlling the opening degree TA of the throttle valve 21 while keeping the opening degree DPG of the electromagnetic valve 39 constant (for example, fully open), so that the positive pressure pump The purge amount is finely adjusted by controlling 50 applied voltage: VP.
[0251]
Here, specific control of the purge amount in the present embodiment will be described along the timing chart of FIG.
[0252]
When the purge execution condition is satisfied, the CPU 49 calculates the engine speed fluctuation: DLN and the first reference value: DLNS1, and determines whether the engine speed fluctuation: DLN is equal to or less than the first reference value: DLNS1. Is determined.
[0253]
In the example of FIG. 16, since the engine speed fluctuation: DLN is smaller than the first reference value: DLNS1 before the purge is started (left side of (1) in the figure), the CPU 42 performs the combustion of the internal combustion engine 1. Assuming that the state is stable, the solenoid valve 39 is fully opened, and a voltage (maximum voltage: MAXVP) at which the atmospheric delivery pressure from the positive pressure pump 50 becomes the maximum pressure is applied to the positive pressure pump 50 (in the figure). (1)).
[0254]
At this time, an atmospheric flow that flows through the charcoal canister 34 is generated by the pressure difference between the atmospheric pressure pumped from the positive pressure pump 50 and the intake pipe negative pressure generated in the intake pipe 18. The vapor flow in the charcoal canister 34 is introduced into the intake pipe 18 by this atmospheric flow, and the purge is started.
[0255]
Subsequently, in order to increase the intake pipe negative pressure downstream of the throttle valve 21, the CPU 42 closes the opening degree TA of the throttle valve 21 by a predetermined opening degree S: TA from the standard opening degree TAS (TAS). -SΔTA) ((2) in the figure).
[0256]
When the opening degree of the throttle valve 21 is corrected in the closing direction by the predetermined opening degree SΔTA, the amount of fresh air flowing to the intake pipe 18 downstream of the throttle valve 21 is reduced. The degree of negative pressure increases, and the pressure difference between the upstream and downstream of the purge passage 49 increases. As a result, the flow rate of the atmosphere flowing through the charcoal canister 34 increases, and the amount of evaporated fuel introduced from the charcoal canister 34 to the intake pipe 18 also increases.
[0257]
On the other hand, when the amount of evaporated fuel introduced into the intake pipe 18 increases, the state of the air-fuel mixture supplied to the combustion chamber 5 changes, and the engine speed fluctuation: DLN becomes larger than before the purge is executed. Opening of the valve 21: TA in the closing direction Predetermined opening: SΔTA corrected engine speed fluctuation: DLN is calculated again after elapse of a predetermined time, and calculated engine speed fluctuation: DLN and the first reference Value: Compare with DLNS1.
[0258]
At this time, if the engine speed fluctuation: DLN is equal to or smaller than the first reference value: DLNS1, the CPU 42 updates the predetermined opening: SΔTA and further increases the opening: TA of the throttle valve 21 by a predetermined amount: Correct by ΔTA in the closing direction to further increase the negative pressure degree of the intake pipe negative pressure.
[0259]
When the engine speed variation: DLN becomes larger than the first reference value: DLNS1 ((3) in the figure) by correcting the opening of the throttle valve 21 in the closing direction, the CPU 42 determines that the combustion state of the internal combustion engine 1 is Assuming that the state has become unstable, “1” is written in the combustion state identification flag (FDLN) storage area of the RAM 44.
[0260]
Further, the CPU 42 cancels the correction of the opening degree of the throttle valve 21 in the closing direction and maintains the opening degree of the throttle valve 21 at that time: TA (TA = TAS−ΔSTAMAX in the example of FIG. 16). 22 is controlled.
[0261]
Then, the CPU 42 reduces the applied voltage: VP of the positive pressure pump 50 by a predetermined amount: ΔVP to slightly reduce the purge amount of the evaporated fuel. In this case, since the atmospheric delivery pressure of the positive pressure pump 50 is slightly reduced, the pressure difference between the upstream and downstream of the purge passage 49 is also slightly reduced. As a result, the flow rate of the atmosphere flowing through the charcoal canister 34 is slightly reduced, and the amount of evaporated fuel supplied from the charcoal canister 34 to the intake pipe 18 is slightly reduced.
[0262]
The CPU 42 calculates the engine speed fluctuation: DLN after reducing the applied voltage: VP of the positive pressure pump 50, and determines whether or not the calculated engine speed fluctuation: DLN is equal to or less than the second reference value: DLNS2. Discriminate ((4) in the figure).
[0263]
In the example of FIG. 16, since the engine speed fluctuation: DLN is smaller than the second reference value: DLNS2 at time (4) in the figure, the CPU 42 determines that the combustion state of the internal combustion engine 1 is sufficiently stable. Therefore, the applied voltage: VP of the positive pressure pump 50 is slightly increased in order to increase the purge amount of the evaporated fuel. In this case, the correction amount is an amount (= K · ΔVP) obtained by adding the positive value: K less than “1” to the predetermined value: ΔVP (= K · ΔVP), and is an amount smaller than the predetermined value: ΔVP. . This process is repeated as long as the engine speed fluctuation: DLN is equal to or less than the second reference value: DLNS2 ((5) to (6) in the figure).
[0264]
When the applied voltage: VP reaches the maximum voltage: MAXVP by repeating the correction of the applied voltage: VP, the CPU 42 ends the correction of the applied voltage and accesses the combustion state identification flag (FDDLN) storage area of the RAM 44. Write “0” ((6) in the figure). Then, the CPU 42 restarts the opening correction of the throttle valve 21 in the opening direction.
[0265]
On the other hand, in (4) in FIG. 16, when the engine speed fluctuation: DLN does not become equal to or less than the second reference value: DLNS2 due to the correction of the applied voltage: VP, the CPU 42 is shown in the timing chart of FIG. Thus, the applied voltage: VP is further reduced by a predetermined value: ΔVP.
[0266]
After a predetermined time has elapsed from when the applied voltage: VP is reduced by the predetermined value: ΔVP ((4) ′ in the figure), the CPU 42 calculates the engine speed fluctuation: DLN, and calculates the calculated engine speed fluctuation: DLN. And the second reference value: DLNS2.
[0267]
At that time, if the engine speed fluctuation: DLN is larger than the second reference value: DLNS2, the CPU 42 further reduces the applied voltage: VP by a predetermined value: ΔVP. In the example of FIG. Since the engine speed fluctuation: DLN is smaller than the second reference value: DLNS2 at the time of (4) ', it is considered that the combustion state of the internal combustion engine 1 is sufficiently stable, and the applied voltage: VP is set to a predetermined value: Increase by K · ΔVP.
[0268]
Hereinafter, the operation and effect of the present embodiment will be described.
[0269]
The CPU 42 executes a purge execution control routine shown in FIG. 18 every predetermined time.
In this purge execution control routine, the CPU 42 determines whether or not the purge execution condition is satisfied in S1801, and terminates the execution of this routine if it is determined that the purge execution condition is not satisfied.
[0270]
On the other hand, if it is determined in S1801 that the purge execution condition is satisfied, the CPU 42 proceeds to S1802 and determines whether or not “1” is stored in the purge idle determination flag (FPIDL) storage area of the RAM 44. .
[0271]
If it is determined in S1802 that “0” is stored in the purge idle determination flag (FPIDL) storage area, the CPU 42 considers that the internal combustion engine 1 is in a non-idle state, and proceeds to S1805. In S1805, the CPU 42 calculates engine speed fluctuation: DLN at that time.
[0272]
Subsequently, the CPU 42 proceeds to S1806, accesses the first reference value control map of the ROM 43, and calculates the first reference value: DLNS1 corresponding to the engine speed at that time. Then, the CPU 42 compares the engine speed fluctuation calculated in S1805: DLN with the first reference value: DLNS1.
[0273]
If it is determined in S1806 that the engine speed fluctuation: DLN is equal to or less than the first reference value: DLNS1, the CPU 42 regards the combustion state of the internal combustion engine 1 as stable, and proceeds to S1808.
[0274]
If it is determined in S1806 that the engine speed fluctuation: DLN is greater than the first reference value: DLNS1, the combustion state of the internal combustion engine 1 is regarded as unstable, and the process proceeds to S1807. In S 1807, the CPU 42 accesses the combustion state identification flag (FDLN) storage area of the RAM 44 and writes “1”.
[0275]
In S1806, the CPU 42, which determines that the engine speed fluctuation: DLN is equal to or less than the first reference value: DLNS1, or has completed the processing of S1807, proceeds to S1808, and combusts state identification flag (FDDLN) in the RAM 44. It is determined whether or not “1” is stored in the storage area.
[0276]
If it is determined in S1808 that “0” is stored in the combustion state identification flag (FDDLN) storage area, the CPU 42 proceeds to S1809 and drives the solenoid valve 39 so that the opening degree of the solenoid valve 39 is fully opened. To do.
[0277]
Next, in S1810, the CPU 42 sets the applied voltage: VP of the positive pressure pump 50 to the maximum voltage: MAXVP, and applies the maximum voltage: MAXVP to the positive pressure pump 50.
[0278]
In this case, the atmosphere pumped from the positive pressure pump 50 flows upstream of the purge passage 49 and the intake pipe negative pressure generated in the intake pipe 18 downstream of the throttle valve 21 is applied downstream of the purge passage 49. A large pressure difference is generated between the upstream and downstream of the purge passage 49, and an atmospheric flow that flows through the charcoal canister 34 is generated. Due to this atmospheric flow, the evaporated fuel adsorbed by the adsorbent in the charcoal canister 34 is desorbed from the adsorbent and introduced into the intake pipe 18.
[0279]
Next, the CPU 42 proceeds to S1811, reads the predetermined opening: SΔTA previously calculated from the predetermined area of the RAM 44, and adds a predetermined value: ΔTA to the predetermined opening: SΔTA, thereby obtaining a new predetermined opening. Opening angle: SΔTA (= SΔTA + ΔTA) is calculated.
[0280]
Subsequently, the CPU 42 proceeds to S1812 and subtracts the predetermined opening: SΔTA calculated in S1811 from the standard opening: TAS to obtain a new opening: TA (= TAS−SΔ) of the throttle valve 21. TA) is calculated. Then, the CPU 42 controls the actuator 22 so that the actual opening of the throttle valve 21 coincides with the new opening: TA, and the execution of this routine is once ended.
[0281]
In this case, the throttle valve 21 is driven in the closing direction, and the amount of fresh air flowing to the intake pipe 18 downstream of the throttle valve 21 decreases, so the negative pressure level of the intake pipe negative pressure increases. This further increases the pressure difference between the upstream and downstream of the purge passage 49 and increases the flow rate of the atmosphere flowing through the charcoal canister 34, so that the amount of evaporated fuel purged from the charcoal canister 34 to the intake pipe 18 increases. To do.
[0282]
On the other hand, if it is determined in S1808 that “1” is stored in the combustion state identification flag (FDDLN) storage area of the RAM 44, the CPU 42 has already purged the evaporated fuel, thereby causing the internal combustion engine 1 to It is considered that the combustion state is unstable, and the process proceeds to S1813.
[0283]
In S1813, the CPU 42 has corrected the applied voltage: VP to stabilize the combustion state of the internal combustion engine 1 whether the applied voltage: VP of the positive pressure pump 50 at that time is smaller than the maximum voltage: MAXVP. Determine whether or not.
[0284]
If it is determined in S1813 that the applied voltage: VP of the positive pressure pump 50 is not smaller than the maximum voltage: MAXVP (VP = MAXVP), the CPU 42 proceeds to S1814, and from the applied voltage: VP (= MAXVP) at that time. A new applied voltage: VP (= MAXVP−ΔVP) is calculated by subtracting the predetermined value: ΔVP, and the new applied voltage: VP is applied to the positive pressure pump 50.
[0285]
At this time, since the atmospheric pressure of the positive pressure pump 50 becomes small, the pressure difference between the upstream and downstream of the purge passage 49 becomes small, and the amount of evaporated fuel introduced from the charcoal canister 34 to the intake pipe 18 decreases. As a result, the evaporated fuel supplied to the internal combustion engine 1 is reduced, and the engine speed fluctuation of the internal combustion engine 1 is reduced.
[0286]
In S1815, the CPU 42 calculates the engine speed fluctuation: DLN after correcting the applied voltage of the positive pressure pump 50, and accesses the second reference value control map of the ROM 43 to correspond to the engine speed at that time. Second reference value to be calculated: DLNS2. Then, the CPU 42 determines whether or not the engine speed fluctuation: DLN is equal to or less than the second reference value: DLNS2, that is, whether the combustion state of the internal combustion engine 1 is stabilized by correcting the applied voltage: VP. To do.
[0287]
If it is determined in S1815 that the engine speed fluctuation: DLN is equal to or smaller than the second reference value: DLNS2, the CPU 42 regards the combustion state of the internal combustion engine 1 as being stable, and proceeds to S1816.
[0288]
In S1816, the CPU 42 calculates a new applied voltage: VP (= VP + K · ΔVP) by adding a predetermined value: K · ΔVP to the applied voltage: VP at that time. In S1817, the CPU 42 determines whether or not the applied voltage: VP (= VP + K · ΔVP) calculated in S1816 is equal to or greater than the maximum voltage: MAXVP.
[0289]
If it is determined in S1817 that the applied voltage calculated in S1816: VP (= VP + K · ΔVP) is less than the maximum voltage: MAXVP, the CPU 42 applies the applied voltage calculated in S1816: VP (= VP + K). After ΔVP) is applied to the positive pressure pump 50, execution of this routine is terminated.
[0290]
In this case, since the atmospheric delivery pressure of the positive pressure pump 50 slightly increases, the flow rate in the purge passage 49 slightly increases, and the amount of evaporated fuel introduced from the charcoal canister 34 to the intake pipe 18 also slightly increases.
[0291]
If it is determined in S1817 that the applied voltage: VP (= VP + K · ΔVP) calculated in S1816 is greater than or equal to the maximum voltage: MAXVP, the CPU 42 proceeds to S1818 and sets the maximum voltage: MAXVP to the new applied voltage. : VP is considered, and the maximum voltage: MAXVP is applied to the positive pressure pump 50.
[0292]
Subsequently, in S1819, the CPU 42 writes “0” in the combustion state identification flag (FDLN) storage area of the RAM 44, and ends the execution of this routine.
[0293]
Thereafter, when this routine is re-executed, if the engine speed fluctuation: DLN is equal to or smaller than the first reference value: DLNS1 in S1806, that is, the applied voltage of the positive pressure pump 50 is changed to the maximum voltage: MAXVP. If the combustion state of the internal combustion engine 1 is still stable thereafter, the CPU 42 determines that “0” is stored in the combustion state identification flag (FDLN) storage area in S1808. And CPU42 restarts the opening degree correction | amendment to the closing direction of the throttle valve 21 in S1809-S1812.
[0294]
If it is determined in S1815 that the engine speed fluctuation: DLN is greater than the second reference value: DLNS2, the CPU 42 proceeds to S1820 and further increases the applied voltage: VP of the positive pressure pump 50 to a predetermined value: ΔVP. And the execution of this routine is terminated.
[0295]
Thereafter, when this routine is re-executed, the CPU 42 determines in S1808 that “1” is stored in the combustion state identification flag (FDDLN) storage area, and in S1813, the applied voltage: VP is the maximum voltage: MAXVP. It will be judged that there is no.
[0296]
Then, the CPU 42 compares the engine speed fluctuation: DLN with the second reference value: DLNS2 again in S1815, and if the engine speed fluctuation: DLN is larger than the second reference value: DLNS2, it is applied in the process of S1820. If the voltage: VP is further reduced by a predetermined value: ΔVP and the engine speed fluctuation: DLN is equal to or smaller than the second reference value: DLNS2, the applied voltage: VP is set to a predetermined value: K · ΔVP in S1816 to S1819. Enlarge.
[0297]
Further, when the internal combustion engine 1 shifts from the non-idle state to the idle state during the execution of the purge, the CPU 42 determines that “1” is stored in the purge idle determination flag (FPIDL) storage area in S1802. Become. In this case, the CPU 42 drives the actuator 22 to return the opening degree of the throttle valve 21: TA to the standard opening degree: TAS in S1803, and then sets “0” in the purge idle determination flag (FPIDL) storage area of the RAM 44 in S1804. After the writing, the processing after S1805 is executed.
[0298]
That is, when the internal combustion engine 1 shifts from the non-idle state to the idle state during the purge execution, the CPU 42 performs the purge execution control after the throttle valve 21 is once returned to the standard opening TAS.
[0299]
As described above, even when the differential pressure changing means is realized by using the throttle valve 21 and the positive pressure pump 50 in combination, the same operations and effects as those of the first embodiment can be obtained.
[0300]
In the first to fifth embodiments described above, the CPU 42 changes the pressure difference between the upstream and downstream of the purge passage 49 or corrects the opening of the electromagnetic valve 39 so that the fuel injection valve 9 is in an injection state. For example, the fuel injection amount, the fuel injection timing, or the injection direction may be changed. Further, the CPU 42 uses various parameters (TAS, ΔTA, ΔDPG, ΔVP) and various reference values (DLNS1) as parameters such as the concentration of evaporated fuel and the engine operating state (intake air amount, engine speed, engine load). , DLNS2) and the like may be changed.
[0301]
【The invention's effect】
In the evaporated fuel processing apparatus for an internal combustion engine according to the present invention, when the evaporated fuel is purged into the intake passage, the pressure difference between the upstream and downstream of the purge passage is increased as long as the combustion state of the internal combustion engine is stable. The amount of evaporated fuel introduced from the purge passage to the intake passage is increased. When the combustion state of the internal combustion engine becomes unstable, the purge amount of the evaporated fuel is reduced.
[0302]
As a result, the purge amount of the evaporated fuel can be increased without destabilizing the combustion state of the internal combustion engine, and both stabilization of the combustion state and securing of the purge amount of evaporated fuel can be achieved at a high level. It becomes.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an internal combustion engine to which an evaporated fuel processing apparatus according to the present invention is applied.
FIG. 2 is a block diagram showing an internal configuration of the ECU according to the first embodiment.
FIG. 3 is a timing chart (1) showing purge execution control according to the first embodiment.
FIG. 4 is a timing chart (2) showing purge execution control according to the first embodiment.
FIG. 5 is a flowchart showing an idle determination routine.
FIG. 6 is a flowchart showing a purge execution control routine according to the first embodiment.
FIG. 7 is a timing chart showing purge execution control according to the second embodiment.
FIG. 8 is a flowchart showing a purge execution control routine according to the second embodiment.
FIG. 9 is a timing chart showing purge execution control according to the third embodiment.
FIG. 10 is a flowchart showing a purge execution control routine according to a third embodiment.
FIG. 11 is a schematic configuration diagram of an internal combustion engine to which an evaporated fuel processing apparatus according to a fourth embodiment is applied.
FIG. 12 is a block diagram showing an internal configuration of an ECU according to a fourth embodiment.
FIG. 13 is a timing chart (1) showing purge execution control according to the fourth embodiment.
FIG. 14 is a timing chart (2) showing purge execution control according to the fourth embodiment.
FIG. 15 is a flowchart showing a purge execution control routine according to a fourth embodiment;
FIG. 16 is a timing chart (1) showing purge execution control according to the fifth embodiment;
FIG. 17 is a timing chart (2) showing purge execution control according to the fifth embodiment.
FIG. 18 is a flowchart showing a purge execution control routine according to the fifth embodiment;
[Explanation of symbols]
18 ... Intake pipe
21 ... Throttle valve
22 ... Actuator
23 ... Throttle position sensor
24 ... Accelerator pedal
25 ... Accelerator position sensor
33 ... Fuel tank
34 ... Charcoal canister
35 ... Evaporative fuel passage
36 ... Solenoid valve
37 ... Air introduction passage
38 ... Negative pressure introduction passage
39 ... Solenoid valve
40 ... ECU
42 ... CPU
43 ... ROM
44 ... RAM
49 ... Purge passage
50 ... Positive pressure pump

Claims (10)

A lean combustion internal combustion engine capable of combusting an oxygen-rich mixture,
A purge passage that guides the evaporated fuel generated in a fuel tank attached to the lean combustion internal combustion engine to an intake passage of the lean combustion internal combustion engine;
A flow rate control valve for adjusting the flow rate of the purge passage;
Combustion state determination means for determining whether or not the combustion state of the lean combustion internal combustion engine is stable when performing purge of evaporated fuel;
Differential pressure changing means for changing the pressure difference between the upstream and downstream of the purge passage;
Purge control means for adjusting the amount of evaporated fuel introduced from the purge passage to the intake passage by controlling at least the differential pressure changing means according to the combustion state of the lean combustion internal combustion engine when purging the evaporated fuel; With
As long as the combustion state of the lean combustion internal combustion engine is stable, the purge control means controls the differential pressure changing means to increase the pressure difference between the upstream and downstream of the purge passage, and from the purge passage An evaporative fuel processing apparatus for a lean combustion internal combustion engine , characterized in that the amount of evaporative fuel introduced into the intake passage is increased. A lean combustion internal combustion engine capable of combusting an oxygen-rich mixture,
A purge passage that guides the evaporated fuel generated in a fuel tank attached to the lean combustion internal combustion engine to an intake passage of the lean combustion internal combustion engine;
A flow rate control valve for adjusting the flow rate of the purge passage;
Combustion state determination means for determining whether or not the combustion state of the lean combustion internal combustion engine is stable when performing purge of evaporated fuel;
Differential pressure changing means for changing the pressure difference between the upstream and downstream of the purge passage;
Purge control means for adjusting the amount of evaporated fuel introduced from the purge passage to the intake passage by controlling at least the differential pressure changing means according to the combustion state of the lean combustion internal combustion engine when purging the evaporated fuel; With
The purge control means changes the differential pressure to reduce the pressure difference between the upstream and downstream of the purge passage when the combustion state determining means determines that the combustion state is unstable when purging the evaporated fuel. An evaporative fuel processing apparatus for a lean burn internal combustion engine , characterized in that the amount of evaporative fuel introduced from the purge passage to the intake passage is reduced by controlling the means. A lean combustion internal combustion engine capable of combusting an oxygen-rich mixture,
A purge passage that guides the evaporated fuel generated in a fuel tank attached to the lean combustion internal combustion engine to an intake passage of the lean combustion internal combustion engine;
A flow rate control valve for adjusting the flow rate of the purge passage;
Combustion state determination means for determining whether or not the combustion state of the lean combustion internal combustion engine is stable when performing purge of evaporated fuel;
Differential pressure changing means for changing the pressure difference between the upstream and downstream of the purge passage;
Purge control means for adjusting the amount of evaporated fuel introduced from the purge passage to the intake passage by controlling at least the differential pressure changing means according to the combustion state of the lean combustion internal combustion engine when purging the evaporated fuel; With
The purge control means is configured to maintain the pressure difference between the upstream and downstream of the purge passage at that time when the combustion state determining means determines that the combustion state is unstable when purging the evaporated fuel. An evaporative fuel processing apparatus for a lean combustion internal combustion engine characterized by controlling the differential pressure changing means and correcting the opening of the flow control valve by a predetermined amount in the closing direction. The purge control means corrects the opening of the flow control valve by a predetermined amount in the closing direction, and determines that the combustion state is stable by the combustion state determination means, the opening of the flow control valve 4. The evaporative fuel processing device for a lean burn internal combustion engine according to claim 3 , wherein the correction is made in the opening direction with a correction amount less than a predetermined amount. The purge control means corrects the opening degree of the flow rate control valve by a predetermined amount in the closing direction, and determines that the combustion state is unstable by the combustion state determination means, the upstream and downstream of the purge passage. 4. The evaporative fuel processing apparatus for a lean burn internal combustion engine according to claim 3, wherein the differential pressure changing means is controlled to reduce the pressure difference. A lean combustion internal combustion engine capable of combusting an oxygen-rich mixture,
A purge passage that guides the evaporated fuel generated in a fuel tank attached to the lean combustion internal combustion engine to an intake passage of the lean combustion internal combustion engine;
A flow rate control valve for adjusting the flow rate of the purge passage;
Combustion state determination means for determining whether or not the combustion state of the lean combustion internal combustion engine is stable when performing purge of evaporated fuel;
Differential pressure changing means for changing the pressure difference between the upstream and downstream of the purge passage;
Purge control means for adjusting the amount of evaporated fuel introduced from the purge passage to the intake passage by controlling at least the differential pressure changing means according to the combustion state of the lean combustion internal combustion engine when purging the evaporated fuel; With
When the purge control means determines that the combustion state is unstable by the combustion state determination means at the time of purging the evaporated fuel, the purge control means controls the flow rate control valve so as to maintain the opening degree at that time, An evaporative fuel processing apparatus for a lean combustion internal combustion engine , wherein the differential pressure changing means is controlled to reduce a pressure difference between upstream and downstream of a purge passage. The purge control means opens the opening of the flow control valve when the combustion state determination means determines that the combustion state is stable after reducing the pressure difference between the upstream and downstream of the purge passage. 7. The evaporative fuel processing apparatus for a lean burn internal combustion engine according to claim 6 , wherein a predetermined amount is corrected in the direction. When the combustion state determining means determines that the combustion state is unstable after reducing the pressure difference between the upstream and downstream sides of the purge passage, the purge control means determines the difference between the upstream and downstream sides of the purge passage. 7. The evaporative fuel processing apparatus for a lean burn internal combustion engine according to claim 6, wherein the differential pressure changing means is controlled to further reduce the pressure difference. A lean combustion internal combustion engine capable of combusting an oxygen-rich mixture,
A purge passage that guides the evaporated fuel generated in a fuel tank attached to the lean combustion internal combustion engine to an intake passage of the lean combustion internal combustion engine;
A flow rate control valve for adjusting the flow rate of the purge passage;
Combustion state determination means for determining whether or not the combustion state of the lean combustion internal combustion engine is stable when performing purge of evaporated fuel;
Differential pressure changing means for changing the pressure difference between the upstream and downstream of the purge passage;
Purge control means for adjusting the amount of evaporated fuel introduced from the purge passage to the intake passage by controlling at least the differential pressure changing means according to the combustion state of the lean combustion internal combustion engine when purging the evaporated fuel; With
The differential pressure changing means is a throttle valve that adjusts the intake air flow rate in the intake passage, and maintains a first opening that is substantially fully open in a normal operation range, and the first opening when purging is performed. An evaporative fuel treatment apparatus for a lean combustion internal combustion engine , wherein the evaporative fuel treatment apparatus is controlled so that the second opening degree is more closed. A lean combustion internal combustion engine capable of combusting an oxygen-rich mixture,
A purge passage that guides the evaporated fuel generated in a fuel tank attached to the lean combustion internal combustion engine to an intake passage of the lean combustion internal combustion engine;
A flow rate control valve for adjusting the flow rate of the purge passage;
Combustion state determination means for determining whether or not the combustion state of the lean combustion internal combustion engine is stable when performing purge of evaporated fuel;
Differential pressure changing means for changing the pressure difference between the upstream and downstream of the purge passage;
Purge control means for adjusting the amount of evaporated fuel introduced from the purge passage to the intake passage by controlling at least the differential pressure changing means according to the combustion state of the lean combustion internal combustion engine when purging the evaporated fuel; With
The lean control is characterized in that the purge control means controls the differential pressure changing means to return the pressure difference between the upstream and downstream of the purge passage to a normal pressure difference when the operating state of the internal combustion engine is changed. A fuel vapor processing apparatus for an internal combustion engine .

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