JP4655695B2 - Evaporative fuel processing equipment - Google Patents

Description

  The present invention relates to an evaporated fuel processing apparatus, and more particularly to an evaporated fuel processing apparatus for supplying evaporated fuel to individual cylinders when an internal combustion engine is started.

  Conventionally, for example, as disclosed in Japanese Utility Model Laid-Open No. 6-37548, a canister that adsorbs evaporated fuel generated inside a fuel tank is provided, and the evaporated fuel adsorbed inside the fuel tank is removed during operation of the internal combustion engine Devices for inhaling an internal combustion engine are known.

  More specifically, this apparatus includes a purge passage that connects the canister and the intake passage of the internal combustion engine, and a control valve that controls the conduction state of the purge passage. The control valve is duty-driven, thereby changing the flow resistance of the purge passage and controlling the flow rate of the evaporated fuel flowing from the canister toward the intake passage.

  The above-described conventional apparatus can cause the evaporated fuel adsorbed by the canister to flow into the cylinder of the internal combustion engine by appropriately driving the control valve with a duty during the operation of the internal combustion engine. In particular, this apparatus drives the control valve so that a larger amount of evaporated fuel is purged during cold start of the internal combustion engine than during normal operation. Since the evaporated fuel is already vaporized, if the evaporated fuel is supplied in a large amount at the cold start, the internal combustion engine shows a good startability. For this reason, according to the conventional apparatus, it is possible to give a good startability to the internal combustion engine.

Japanese Utility Model Publication No. 6-37548 JP-A-8-200166

  A multi-cylinder internal combustion engine mounted on a vehicle generally has a plurality of cylinder pairs that operate in the same phase with a stroke difference of 360 ° CA. For example, a four-cylinder internal combustion engine has two pairs of cylinders, and a six-cylinder internal combustion engine has three pairs of cylinders. Hereinafter, for the sake of convenience, a description will be given by taking a four-cylinder internal combustion engine as an example.

  In a four-cylinder internal combustion engine, the # 1 and # 4 cylinders usually constitute a cylinder pair, and the # 2 and # 3 cylinders usually constitute a cylinder pair. These cylinder pairs operate with a phase difference of 180 ° CA. For example, every time the crankshaft rotates 180 ° CA, the same stroke is performed in the order of # 4 → # 2 → # 1 → # 3. Is repeated so that the operation of the internal combustion engine proceeds.

  If the internal combustion engine is stopped with the # 1 cylinder reaching the vicinity of the intake top dead center, the intake stroke is started in the # 1 cylinder at the same time as the starter is turned on. Thereafter, when the rotation of about 180 ° CA occurs, the intake stroke is started in the # 3 cylinder, and when the rotation of 180 ° CA is further generated, the intake stroke of the # 4 cylinder is started.

  Ignition control and the like in an internal combustion engine must be performed in synchronization with the crank angle. For that purpose, after starting the internal combustion engine, it is necessary to first grasp the absolute position of the crankshaft and then continue to grasp the rotational position of the crankshaft. In order to satisfy this requirement, the internal combustion engine includes a crank angle sensor that generates a cylinder discrimination signal when a cylinder belonging to a specific cylinder pair reaches an intake top dead center.

  Specifically, in the case of a four-cylinder internal combustion engine, for example, the situation is expressed when the # 1 cylinder reaches the intake top dead center and when the # 4 cylinder reaches the intake top dead center. A crank angle sensor for generating a cylinder discrimination signal is provided. In such an internal combustion engine, after the starter is turned on, ignition processing can be performed when a cylinder discrimination signal is generated for the first time.

  For example, assume that the first cylinder discrimination signal is generated when the # 4 cylinder reaches the intake top dead center after the start of the internal combustion engine. Such a situation occurs when the internal combustion engine is stopped with the # 1 cylinder past the intake top dead center. If the # 1 cylinder slightly exceeds the intake top dead center and the internal combustion engine is stopped, after the starter is turned on, the intake stroke of the # 1 cylinder and the intake stroke of the # 3 cylinder Cylinder discrimination is performed at the stage where the processes are sequentially executed.

  Immediately after starting the internal combustion engine, the intake pipe pressure remains almost at atmospheric pressure, so that a large purge amount of evaporated fuel cannot be secured. In the above operation example, for the # 3 cylinder, an operation of 360 ° CA occurs after the starter is turned on and before the intake stroke is completed. In this case, it can be expected that the intake pipe pressure becomes negative to some extent before the intake stroke ends, and it is easy to ensure a sufficient purge time before the end of the intake stroke. That is, for the # 3 cylinder, conditions are set in which a desired amount of evaporated fuel can be easily sucked into the cylinder.

  On the other hand, for the # 1 cylinder, a negative pressure in the intake pipe pressure can hardly be expected, and the purge time can be secured only for a short time required for rotation of 180 ° CA. Therefore, in the first intake stroke performed in the # 1 cylinder, a sufficient amount of evaporated fuel cannot be sucked into the cylinder.

  The conventional apparatus uniformly supplies purge gas to all the cylinders without distinguishing the individual cylinders. Therefore, in this apparatus, after starting the internal combustion engine, the control valve can be opened quickly to perform control for supplying as much purge gas as possible to all the cylinders. According to such control, in the case of the above operation example, it is possible to supply sufficient fuel to the # 3 cylinder before the cylinder discrimination is made.

  However, according to the above control, a halfway amount of the evaporated fuel is sucked into the # 1 cylinder by the intake stroke that is started simultaneously with the starter being turned on. In such a fuel supply state, an appropriate explosion stroke (combustion) cannot be obtained. For this reason, the fuel sucked halfway is discharged into the exhaust system in the subsequent exhaust stroke without properly burning. In this regard, the above-described conventional apparatus has a characteristic that the evaporated fuel is easily blown through when the internal combustion engine is started.

  The present invention has been made to solve the above-described problem, and provides an evaporative fuel processing apparatus that can sufficiently improve the startability of an internal combustion engine without deteriorating the emission characteristics of the internal combustion engine. Objective.

In order to achieve the above object, a first invention provides an evaporative fuel processing apparatus for supplying evaporative fuel to an internal combustion engine having a plurality of pairs of cylinders operating in the same phase with a stroke difference of 360 ° CA. Because
A canister that stores evaporative fuel;
A purge passage communicating the canister to the intake port of each cylinder;
A purge control valve provided for each cylinder to control the conduction state between the intake port of each cylinder and the canister;
A first cylinder discrimination signal generating means for generating a first cylinder discrimination signal at a crank angle at which the specific cylinder reaches a specific state during operation of the internal combustion engine;
Second cylinder discrimination signal generating means for generating a second cylinder discrimination signal at a crank angle at which the cylinders constituting the specific cylinder and the cylinder pair reach the specific state;
The purge control valve of the first discrimination cylinder that performs the intake stroke immediately after the generation of the first cylinder discrimination signal and the purge control valve of the second discrimination cylinder that performs the intake stroke immediately after the generation of the second cylinder discrimination signal are simultaneously opened. Discriminating cylinder group purge means for realizing discriminating cylinder group purge,
The discriminating cylinder group purge is started when a first delay time has elapsed from the start of the internal combustion engine.

  According to a second aspect of the present invention, in the first aspect, the discrimination cylinder group purge is performed before an intake stroke that is executed for the first time after the first first cylinder discrimination signal or the first second cylinder discrimination signal is finished. It is characterized by being executed so as to be completed after securing a desired purge time.

  According to a third aspect of the present invention, in the first or second aspect, after the internal combustion engine is started, the purge control valves of the non-discrimination cylinders excluding the first discrimination cylinder and the second discrimination cylinder are respectively set to the discrimination cylinder. A non-discriminating cylinder purging means for realizing a purge in the non-discriminating cylinder by opening the valve by a method different from the group purge is provided.

Moreover, 4th invention is set in 3rd invention,
The non-discriminating cylinder purge means includes non-discriminating cylinder group purge means for simultaneously opening all of the purge control valves of the non-discriminating cylinders to realize non-discriminating cylinder group purge,
The non-discrimination cylinder group purge is started earlier than the discrimination cylinder group purge, and a desired purge time is secured before either the first cylinder discrimination signal or the second cylinder discrimination signal is issued. And then executed so as to be terminated.

  In a fifth aspect based on the fourth aspect, the non-discriminating cylinder group purge is performed when a second delay time shorter than the first delay time elapses from the starting time of the internal combustion engine. It is started.

The sixth invention is the third invention, wherein
A purge required time estimating means for estimating a purge required time required to supply a desired amount of evaporated fuel to the non-discriminating cylinder immediately after starting the internal combustion engine;
Comparing means for comparing the purge required time with the purgeable time,
The non-discriminating cylinder purge means includes
Normal control means for performing a purge in the non-discrimination cylinder prior to the discrimination cylinder group purge when the purge required time is equal to or less than the purgeable time;
Reversing control means for performing purging for the non-discriminating cylinders after the start of the discriminating cylinder group purge when the purge required time is longer than the purgeable time;
It is characterized by providing.

The seventh invention is the third invention, wherein
During operation of the internal combustion engine, a crank angle signal is generated for each predetermined crank angle, and after starting the internal combustion engine, a predetermined crank angle is determined from a position where the specific cylinder or a cylinder constituting the specific cylinder and the cylinder pair reaches the specific state. A crank angle signal generating means for starting to generate the crank angle signal from the stage where the rotational position of the crankshaft reaches a position that is traced back;
The discriminating cylinder group purge means starts the discriminating cylinder group purge when the crank angle signal is generated,
The non-discriminating cylinder purge means performs the purging of the non-discriminating cylinders in synchronization with a crank angle after the discrimination cylinder group purge.

  According to the first aspect of the present invention, the determination is made for the first determination cylinder that performs the intake stroke immediately after the generation of the first cylinder determination signal and the second determination cylinder that performs the intake stroke immediately after the generation of the second cylinder determination signal. Cylinder group purge can be performed. If the first cylinder discrimination signal is generated first after the internal combustion engine is started, the intake stroke may have started in the second discrimination cylinder simultaneously with the start. According to the present invention, in this case, the discrimination cylinder group purge is not started until the first delay time elapses after the internal combustion engine is started. For this reason, the amount of evaporated fuel sucked into the second discrimination cylinder, that is, the amount of evaporated fuel discharged to the exhaust system thereafter can be sufficiently suppressed. When the second cylinder discrimination signal is generated first after the internal combustion engine is started, the amount of evaporated fuel discharged from the first discrimination cylinder is sufficiently suppressed by the same principle.

  According to the second aspect of the invention, the discrimination cylinder group purge is performed so that a desired purge time is ensured before the first intake stroke in the first discrimination cylinder or the first intake stroke in the second discrimination cylinder ends. Executed. As a result, a sufficient amount of evaporated fuel is sucked into these cylinders in the first intake stroke. Therefore, according to the present invention, the startability of the internal combustion engine can be sufficiently improved.

  According to the third invention, the non-discriminating cylinder can be purged by a method different from that of the first discriminating cylinder and the second discriminating cylinder. Therefore, according to the present invention, it is possible to ensure a high degree of freedom with respect to the purge method, and as a result, it is possible to sufficiently improve both the emission characteristics and the startability.

  According to the fourth invention, in the non-discriminating cylinder, the non-discriminating cylinder group purge can be started prior to the discriminating cylinder group purge. The non-discrimination cylinder group purge is executed so that a sufficient purge time is ensured before the cylinder discrimination signal is generated. When the intake stroke is started in the first or second discriminating cylinder simultaneously with the start of the internal combustion engine, the intake stroke in the non-discriminating cylinder is started following the intake stroke. Then, the intake stroke of the non-discrimination cylinder is executed until immediately before the cylinder discrimination signal is generated. According to the non-discriminating cylinder group purge in the present invention, it is possible to create a situation suitable for supplying a sufficient amount of evaporated fuel to the non-discriminating cylinder in which the intake stroke is performed before the cylinder discrimination signal is generated. . Therefore, according to the present invention, the startability of the internal combustion engine can be sufficiently improved.

  According to the fifth aspect, after the start of the internal combustion engine is started, execution of the non-discriminating cylinder group purge can be prohibited until the second delay time elapses. The purge of the evaporated fuel becomes easier and more stable as the intake pipe pressure becomes negative. Therefore, according to the present invention, the stability of the non-discriminating cylinder group purge can be increased, and the stability of combustion in the non-discriminating cylinder can be increased.

  According to the sixth aspect of the present invention, when the required purge time is equal to or shorter than the purgeable time, that is, when a desired purge can be performed in the non-discriminating cylinder immediately after starting, the first purge for the non-discriminating cylinder is performed. It can run quickly and create a situation that is advantageous for a quick start. On the other hand, when the purge required time is longer than the purgeable time and sufficient purge cannot be performed in the non-discriminating cylinder, the initial purge execution timing for the non-discriminating cylinder is delayed to prevent halfway purge. be able to. Therefore, according to the present invention, even when a sufficiently long purge time is required at the start of the internal combustion engine, it is possible to reliably prevent the deterioration of the emission characteristics.

  According to the seventh aspect of the present invention, it is possible to execute the discrimination cylinder group purge that is synchronized with the crank angle before the cylinder discrimination signal is generated. Further, according to the present invention, the purge of the non-discriminating cylinder can also be executed in a state synchronized with the crank angle. For this reason, according to the present invention, there is little room to be affected by the event, and a highly stable purge can be realized.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
FIG. 1A is a diagram for explaining the mechanical configuration of the first embodiment of the present invention. FIG. 1B is a diagram for explaining the electrical configuration of the system of the present embodiment. As shown in FIG. 1A, the system of this embodiment includes an internal combustion engine 10. The internal combustion engine 10 includes a plurality of cylinders. Hereinafter, for convenience of explanation, it is assumed that the internal combustion engine 10 is a four-cylinder engine.

  Of the four cylinders included in the internal combustion engine 10, the # 2 cylinder and the # 3 cylinder form a “cylinder pair” that operates in the same phase with a stroke difference of 360 ° CA. On the other hand, the # 1 cylinder and the # 4 cylinder constitute a "cylinder pair" that satisfies the same relationship. The former cylinder pair and the latter cylinder pair operate with a phase difference of 180 ° CA.

  The four cylinders each incorporate an intake valve 12 that opens and closes an intake port and an exhaust valve 14 that opens and closes an exhaust port. FIG. 1A shows one of these cylinders. A branch pipe of the intake manifold 16 communicates with the intake port of each cylinder. The branch pipes for four cylinders gather at one end and communicate with the surge tank 18. A throttle valve 20 for controlling the conduction state of the intake passage is disposed upstream of the surge tank 18.

  The internal combustion engine 10 includes a fuel injection valve 22 for each cylinder. The fuel injection valve 22 can inject fuel into the intake port of each cylinder. A purge passage 24 communicates with the vicinity of the intake port. The purge passage 24 is prepared for each cylinder, and each has a D-VSV 26. The D-VSV 26 is a control valve that opens and closes in response to a duty signal. According to the D-VSV 26, the conduction state of the purge passage 24 can be substantially controlled.

  The purge passages 24 for the four cylinders all communicate with the canister 28. The canister 28 incorporates activated carbon therein, and includes a vapor inflow hole 30 and an air hole 32. The vapor inflow hole 30 communicates with the fuel tank via a vapor passage (not shown). The air holes 32 communicate with the atmosphere as shown in FIG.

  Inside the fuel tank, there is a gas containing evaporated fuel. This gas flows into the canister 28 from the vapor inflow hole 30 when refueling, for example. At this time, the canister 28 adsorbs the evaporated fuel contained in the gas and causes only the air to flow out from the atmospheric hole 32. As a result, the canister 28 is in a state where the evaporated fuel is adsorbed.

  The system of this embodiment can appropriately open the D-VSV 26 of each cylinder during the operation of the internal combustion engine 10. While the internal combustion engine 10 is in operation, intake negative pressure is generated. When the D-VSV 26 is opened, the negative pressure is guided to the canister 28. As a result, a flow of air flowing in from the atmospheric hole 32 is generated inside the canister 28, and the evaporated fuel is purged by the flow of air. In the system of this embodiment, the evaporated fuel adsorbed by the canister 28 can be caused to flow into the individual cylinders in this way.

  As shown in FIG. 1B, the system of the present embodiment includes an ECU (Electronic Control Unit) 40. An ignition switch (IG) 42, a starter switch 44, a crank angle sensor 46, and a water temperature sensor 48 are connected to the ECU 40. The ECU 40 is connected to a D-VSV 26 disposed in the # 1 cylinder to the # 4 cylinder.

  The crank angle sensor 46 generates a pulse signal every time the crankshaft rotates 30 ° CA, and when the # 1 cylinder piston passes the intake top dead center, and the # 4 cylinder piston indicates the intake top dead center. When passing, a cylinder discrimination signal is generated. When the ECU 40 receives the cylinder discrimination signal indicating that the # 4 cylinder has reached the intake top dead center after the internal combustion engine 10 is started, the ECU 40 recognizes that the crank angle is 0 ° CA. When the cylinder discrimination signal indicating that the # 1 cylinder has reached the intake top dead center is received, the crank angle is recognized as 360 ° CA at that time. Hereinafter, this recognition of the crank angle is referred to as “cylinder discrimination”.

  As described above, the ECU 40 can finish the cylinder discrimination at the timing when the # 1 cylinder or the # 4 cylinder reaches the intake top dead center after the internal combustion engine 10 is started. When the cylinder discrimination is completed, the ECU 40 can continue to specify the rotational position of the crankshaft by counting the pulse signals generated every 30 ° CA thereafter.

[Operation of Embodiment 1]
Normally, the internal combustion engine 10 is started in a situation where the internal combustion engine 10 is not warmed up. Under such circumstances, since the fuel is difficult to vaporize, when the fuel is injected from the fuel injection valve 22, a situation occurs in which part of the fuel remains in a liquid state and does not contribute to combustion. On the other hand, if the fuel adsorbed by the canister 28 is purged and supplied to the internal combustion engine 10, the already vaporized fuel can be supplied, and good combustibility can be obtained even in a low temperature environment.

  For this reason, the system of the present embodiment realizes a desired fuel supply by stopping the fuel supply by the fuel injection valve 22 and purging the evaporated fuel in the canister 28 when the internal combustion engine 10 is started. . More specifically, the system according to this embodiment is configured so that, when the internal combustion engine 10 is started, the D-VSV 26 disposed for each cylinder is appropriately opened while the fuel injection valve 22 is closed, so that the individual cylinders are opened. An appropriate amount of evaporated fuel was supplied.

(Crank angle asynchronous purge and crank angle synchronous purge)
In order to improve the responsiveness of the internal combustion engine 10 at the time of starting, it is desirable to supply fuel to each cylinder as early as possible. As a method for satisfying this requirement, for example, it is conceivable to start supplying purge fuel to all cylinders simultaneously with the start of the internal combustion engine 10. That is, it is conceivable that the D-VSV 26 is opened in all the cylinders without synchronizing with the crank angle when the internal combustion engine 10 is started.

  Hereinafter, the purge performed asynchronously with the crank angle in this manner is referred to as “crank angle asynchronous purge”. On the other hand, the purge by controlling the opening and closing of the D-VSV 26 in synchronization with the crank angle is referred to as “crank angle synchronous purge”.

  FIG. 2 is a timing chart for explaining an operation example when the crank angle asynchronous purge is started simultaneously with the start of the internal combustion engine 10. 2A shows the engine speed NE immediately after the internal combustion engine 10 is started. FIG. 2B shows the transition of the stroke in each cylinder. Further, FIG. 2C is a diagram for explaining a purge rule (hereinafter referred to as “comparative example”) used here.

  The comparative example shown in FIG. 2 is realized when the internal combustion engine 10 is stopped with the # 1 cylinder slightly exceeding the intake top dead center. In this case, as shown in FIG. 2 (B), the intake stroke of the # 1 cylinder is started simultaneously with the start of the internal combustion engine 10, and thereafter, the intake stroke of the # 3 cylinder when the crankshaft rotates about 180 ° CA. Is started. When the rotation of 180 ° CA further occurs, the # 4 cylinder reaches the intake top dead center, and a cylinder discrimination signal is issued at that time.

  The triangular waveform repeatedly drawn in FIG. 2B indicates the value of the crank angle counter CCRNK that is counted based on the output of the crank angle sensor 46 after completion of cylinder discrimination. That is, the ECU 40 sets the crank angle counter CCRNK to a value corresponding to 0 ° CA (specifically, “0”) when the cylinder discrimination signal indicating that the # 4 cylinder has reached the intake top dead center is recognized. Thereafter, CCRNK is counted up every time a pulse signal is issued from the crank angle sensor 46 every 30 ° CA, and every time the crank angle reaches 720 ° CA, that is, every time the # 4 cylinder reaches the intake top dead center. Reset to zero.

  When the cylinder discrimination signal that is first generated after the internal combustion engine 10 is started indicates that the # 1 cylinder has reached the intake top dead center, the crank angle counter CCRNK receives 360 to receive the signal. A CA corresponding value (specifically 12) is set. In this case, every time the crank angle rotates by 30 ° CA, CCRNK is counted up with “12” as an initial value. In any case, after the cylinder discrimination is completed, the ECU 40 looks at the value of the crank angle counter CCRNK to determine what rotational position the crankshaft is, that is, what state each cylinder of the internal combustion engine 10 is in. Can be detected.

  A white arrow shown in FIG. 2C indicates a period in which purging is performed in each cylinder, that is, a period in which the D-VSV 26 of each cylinder is opened, according to the purge rule of the comparative example. Show. Specifically, FIG. 2C shows that crank angle asynchronous purge is performed for all cylinders for a relatively long time simultaneously with the start of the internal combustion engine 10, and after cylinder discrimination, # 3 → # 4 → # 2 → This shows how the crank angle synchronous purge is executed in the order of # 1.

  Immediately after the internal combustion engine 10 is started, since the intake pipe pressure MV is hardly negative, the purge amount per unit time is small. For this reason, it is necessary to secure sufficient time for the crank angle asynchronous purge performed immediately after starting. According to the example shown in FIG. 2, by starting the crank angle asynchronous purge immediately after starting, it is possible to ensure a sufficient purge time before the intake stroke of the # 3 cylinder ends. For this reason, according to this example, a sufficient amount of evaporated fuel can be supplied to the # 3 cylinder at the end of cylinder discrimination. As a result, as shown in FIG. 2B, the first explosion can be obtained in the # 3 cylinder when the rotation of about 180 ° CA occurs after the cylinder discrimination.

  The evaporated fuel purged into the intake system by the crank angle asynchronous purge is sucked into each cylinder by sequentially performing the intake stroke in the # 4 cylinder, # 2 cylinder, and # 1 cylinder after cylinder discrimination. Further, according to the comparative example shown in FIG. 2, the crank angle synchronous purge is executed before the start of the intake stroke for the cylinder in which the evaporated fuel is consumed by the crank angle asynchronous purge (see FIG. 2C). Since the intake pipe pressure MV becomes negative after the first explosion occurs, the crank angle synchronous purge can sufficiently supply the amount of evaporated fuel in a short time.

  As described above, according to the purge rule of the comparative example shown in FIG. 2, after the internal combustion engine 10 is started, an appropriate amount of evaporated fuel can be quickly and sequentially sucked into each cylinder. For this reason, according to such a purge rule, it is possible to start the internal combustion engine 10 with excellent responsiveness.

(Problems of the comparative example)
However, in the case of the comparative example shown in FIG. 2, a part of the evaporated fuel by the crank angle asynchronous purge may be slightly discharged from the # 1 cylinder in an unburned state. That is, according to the example shown in FIG. 2, the crank angle asynchronous purge is started simultaneously with the start of the internal combustion engine 10, and the intake stroke in the # 1 cylinder is started. Then, the intake stroke started in the # 1 cylinder is ended in the middle of execution of the crank angle asynchronous purge.

  At the stage where the intake stroke is performed in the # 1 cylinder, the intake pipe pressure MV is hardly reduced to a negative pressure. Therefore, the amount of evaporated fuel purged until the intake stroke ends is small. However, even if it is slight, the evaporated fuel is sucked into the inside by the first intake stroke in the # 1 cylinder.

  The # 1 cylinder reaches the compression top dead center when the # 4 cylinder reaches the intake top dead center, that is, when cylinder discrimination is performed. However, at this stage, since the amount of evaporated fuel sucked into the cylinder is small, proper combustion cannot be obtained. For this reason, the evaporated fuel sucked into the # 1 cylinder is discharged to the exhaust system in an unburned state in the subsequent exhaust stroke.

  In the internal combustion engine 10, the intake stroke may be started in the # 4 cylinder simultaneously with the start-up. In this case, due to the same phenomenon, a part of the evaporated fuel by the crank angle asynchronous purge is slightly discharged from the # 4 cylinder in an unburned state. In order to maintain good emission characteristics when the internal combustion engine 10 is started, it is desirable that such fuel discharge does not occur. In this regard, the comparative example shown in FIG. 2 is not necessarily the best purge rule for reducing the emission of the internal combustion engine 10.

(Characteristic operation of the first embodiment)
FIG. 3 is a timing chart for explaining the characteristic operation of the system of this embodiment. The timing chart shown in FIG. 3 is the same as the chart of the comparative example shown in FIG. 2 except that the crank angle asynchronous purge rule shown in FIG. 3C is changed.

  As shown in FIG. 3C, in the present embodiment, the crank angle asynchronous purge is performed for the # 2, # 3 cylinder group and the # 1, # 4 cylinder group at different timings. . Specifically, the group purge for the # 2 and # 3 cylinders is started simultaneously with the start of the internal combustion engine 10, and the group for the # 1 and # 4 cylinders is started after a certain delay time thereafter. Is done.

  FIG. 3 illustrates a case where the internal combustion engine 10 starts the intake stroke with the # 1 cylinder simultaneously with the start-up. In this case, according to the purge rule of the present embodiment described above, the following situation occurs. That is, in the # 1 cylinder, the start of the crank angle asynchronous purge is delayed, so that the amount of evaporated fuel sucked in the first intake stroke, that is, the amount of evaporated fuel discharged in an unburned state becomes almost zero. (Refer to FIG. 3 (C) # 1 purge). In the # 3 cylinder, since the start of the crank angle asynchronous purge is not delayed, a sufficient amount of evaporated fuel is sucked in the first intake stroke (refer to # 3 purge in FIG. 3C).

  The delay times for the # 1 and # 4 cylinders are set to such values that the crank angle asynchronous purge in these cylinders is completed before the end of cylinder discrimination in the case shown in FIG. In other words, the delay time is set to such a value that the crank angle asynchronous purge in the # 1 and # 4 cylinders is completed before the end of the second intake stroke after the starter is turned on. For example, the time until the end of the second intake stroke after the starter is turned on (the time until cylinder discrimination ends in the case shown in FIG. 3) is 0.4 sec, and the time required for the crank angle asynchronous purge is 1 In the case of .5 sec, the delay time is set to 0.25 sec. According to such a setting, a sufficient amount of evaporated fuel is also sucked into the # 4 cylinder by the first intake stroke (see # 4 purge in FIG. 3C).

  For the # 2 cylinder, the largest margin is ensured between the end timing of the crank angle asynchronous purge and the end timing of the first intake stroke. For this reason, a sufficient amount of evaporated fuel is also sucked into the # 2 cylinder in the first intake stroke (refer to # 2 purge in FIG. 3C). As described above, according to the purge rule of the present embodiment, when the internal combustion engine 10 starts starting from the intake stroke of the # 1 cylinder, the fuel is appropriately supplied to the individual cylinders and the unburned fuel is supplied. Can be sufficiently suppressed.

  In addition to the case illustrated in FIG. 3, the internal combustion engine 10 may start from the intake stroke of the # 4 cylinder. In this case, in the operation shown in FIG. 3, an operation in which # 1 and # 4, and # 2 and # 3 are interchanged is realized. As a result, fuel can be appropriately supplied to each cylinder while sufficiently suppressing the amount of unburned fuel discharged from the # 4 cylinder.

  The internal combustion engine 10 may be started from a state where the phase of 180 ° CA is shifted from the case illustrated in FIG. 3. Specifically, the engine may be started from the intake stroke of # 2 cylinder or # 3 cylinder. According to the purge rule of the present embodiment, in this case, crank angle asynchronous purge suitable for starting can be realized more than equivalent to the case where the comparative example shown in FIG. 2 is used.

  That is, according to the purge rule of the present embodiment, the group purge for the # 2 and # 3 cylinders is started simultaneously with the start of the internal combustion engine 10, and then the group purge for # 1 and # 4 is started after a predetermined delay time. Is done. Therefore, if the start is started from the intake stroke of the # 2 cylinder or the # 3 cylinder, a certain amount of evaporated fuel is sucked into the # 2 or # 3 cylinder in the first intake stroke according to this rule. It cannot be avoided. In this regard, the purge rule of this embodiment is the same as that of the comparative example shown in FIG.

  In the internal combustion engine 10, the intake stroke of the # 1 or # 4 cylinder is performed following the intake stroke of the # 2 or # 3 cylinder. In the internal combustion engine 10 of the present embodiment, the intake stroke ends when a time of about 0.4 seconds elapses after the starter is turned on. On the other hand, according to the purge rule of this embodiment, the delay time for the # 1 and # 4 cylinders is set so that the crank angle asynchronous purge for these cylinders ends before the elapse of 0.4 sec. For this reason, even in the purge rule of this embodiment, when the second intake stroke after the starter is turned on is performed in the # 1 or # 4 cylinder, a sufficient amount of evaporated fuel is supplied to those cylinders. be able to. The purge rule of this embodiment is the same as that of the comparative example shown in FIG.

  The stability of the purge improves as the intake pipe pressure MV becomes negative. For this reason, the stability of the crank angle asynchronous purge is improved as the execution time is later. According to the purge rule of this embodiment, the start timing of the crank angle asynchronous purge in the # 1 or # 4 cylinder is delayed by the delay time as compared with the case of the comparative example shown in FIG. For this reason, when comparing the purge stability for these cylinders, the case according to the purge rule of the present embodiment is superior to the case according to the comparative example shown in FIG. Therefore, according to the purge rule of the present embodiment, even when the internal combustion engine 10 is started from the intake stroke of the # 2 or # 3 cylinder, as described above, a more preferable crank than the case according to the comparative example. Angular asynchronous purge can be realized.

[Specific Processing in Embodiment 1]
Hereinafter, with reference to FIGS. 4 to 8, the contents of specific processing executed by the ECU 40 in the present embodiment in order to realize the above-described crank angle asynchronous purge will be described.
FIG. 4 is a flowchart of a main routine executed by the ECU 40 to realize crank angle asynchronous purge. This routine is repeatedly started at predetermined time intervals while the ignition switch (IG) of the vehicle is turned on.

  When the routine shown in FIG. 4 is started, first, it is determined whether or not the start purge condition is satisfied (step 100). The start purge condition is a condition that is satisfied under a situation in which the internal combustion engine 10 is to be started by the evaporated fuel captured by the canister 28. Specifically, this condition is recognized when the internal combustion engine 10 is cold-started in a state where a sufficient amount of evaporated fuel is adsorbed by the canister 28.

  If it is confirmed that the starting purge condition is satisfied, it is next determined whether or not the count value of the crank angle counter CCRNK is −1 or less (step 102). As described above, the crank angle counter CCRNK is set to a value corresponding to 0 ° CA (0) or a value corresponding to 360 ° CA (12) when the cylinder discrimination signal is generated. The count value CCRNK is maintained at −1 until generation of a cylinder discrimination signal is recognized. For this reason, the processing of this step 102 is equivalent to determining whether or not a cylinder discrimination signal has not been generated.

  After the starter is turned ON, until the cylinder discrimination signal is generated, in step 102, the establishment of CCRNK ≦ −1 is recognized. In this case, the crank angle asynchronous purge for the groups of # 2 and # 3 cylinders is then executed (step 104). The crank angle asynchronous purge for the # 2 and # 3 cylinders is thereafter terminated when a predetermined execution time KTST1 is counted. The contents of the crank angle asynchronous purge executed here will be described in detail later with reference to FIG. 5 and FIG.

  Next, it is determined whether the elapsed time after the starter is turned on, that is, whether the cranking time TST has reached the delay time KST1 (step 106). While this determination is denied, the current processing cycle is immediately terminated thereafter. On the other hand, if it is confirmed that TST ≧ KST1 is established, crank angle asynchronous purge for the # 1 and # 4 cylinder groups is executed (step 108). The crank angle asynchronous purge for the # 1 and # 4 cylinders is thereafter terminated when a predetermined execution time KTST2 is counted. The contents of the crank angle asynchronous purge executed here will be described later in detail with reference to FIG. 7 and FIG.

  When the cylinder discrimination signal is generated after the internal combustion engine 10 is started, 0 or 12 is set in the crank angle counter CCRNK. After this setting, in step 102, it is determined that CCRNK ≦ −1 is not satisfied. In this case, execution of start purge control, that is, control for crank angle synchronous purge is commanded (step 110). After this process is executed, control (crank angle synchronous purge control) for opening and closing the D-VSV 26 of each cylinder in synchronization with the crank angle is started.

  When a further time elapses after the crank angle synchronous purge is started, the internal combustion engine 10 is sufficiently warmed up and the necessity for the start purge disappears. When this necessity disappears, the establishment of the start purge condition is denied in step 100, and the start of normal fuel injection control is commanded (step 112). After this process is executed, normal operation control using the fuel injection valve 22 is started thereafter.

  According to the processing described above, the group purge for the # 2 and # 3 cylinders is started simultaneously with the start of the internal combustion engine 10, and then the group purge for the # 1 and # 4 cylinders is started when the delay time KST1 has elapsed. can do. For this reason, according to the system of this embodiment, it is possible to realize crank angle asynchronous purge in accordance with the purge rule shown in FIG.

  FIG. 5 is a flowchart of the first routine executed in step 104 shown in FIG. This routine is executed in order to realize crank angle asynchronous purge for the # 2 and # 3 cylinders.

  According to the purge rule described above (see FIG. 3), continuous crank angle asynchronous purge is performed in each cylinder. However, if the crank angle asynchronous purge is continuously performed, the purge gas flow is stabilized and gas mixing is not promoted. On the other hand, if the crank angle asynchronous purge is intermittently performed at an appropriate cycle, the purge gas flow is disturbed, and gas mixing can be promoted. Therefore, in this embodiment, the crank angle asynchronous purge is intermittently performed in each cylinder.

  In the routine shown in FIG. 5, first, the period counter TSYUK1 is incremented in order to realize the above function (step 120). Next, it is determined whether TSYUK1 is equal to or greater than the cycle determination value KSYUK1 (step 122).

  The cycle determination value KSYUK1 is a value corresponding to one cycle in which the D-VSV 26 is opened and closed when intermittent crank angle asynchronous purge is executed. On the other hand, the maximum value (value greater than or equal to KSYUK) is set in the cycle counter TSYUK1 by the initial process. Therefore, when the process of step 122 is executed for the first time after the internal combustion engine 10 is started, it is recognized that TSYUK1 ≧ KSYUK1.

  When the establishment of TSYUK1 ≧ KSYUK1 is recognized, it is determined that the start time of a new driving cycle of the D-VSV 26 has arrived. In this case, first, the cycle counter TSYUK1 is reset to 0 (step 124), and then the number of asynchronous purge executions CPGST1 is incremented (step 126). The number of executions CPGST1 is set to 0 by the initial process. For this reason, the value CPGST1 coincides with the number of asynchronous purges actually executed for the # 2 and # 3 cylinders after the starter is turned on.

  In the routine shown in FIG. 5, it is next determined whether or not the number of asynchronous purge executions CPGST1 is equal to or greater than the number of guards KCST1 (step 128). The guard count KCST1 is a guard value imposed on the number of executions of crank angle asynchronous purge for the # 2 and # 3 cylinders. If it is determined that the number of executions CPGST1 is equal to or greater than the number of guards KCST1, then this routine is immediately terminated without opening the D-VSV 26 in order to avoid excessive purge.

  On the other hand, if it is determined that the execution count CPGST1 is smaller than the guard count KCST1, it is further determined whether the accumulated purge time TSPGST1 is equal to or longer than the guard time KTST1 (step 130). The accumulated purge time TSPGST1 is a value obtained by integrating the periods during which crank angle asynchronous purge for the # 2 and # 3 cylinders has been executed since the start of the internal combustion engine. On the other hand, the guard time KTST1 is a guard value imposed on the execution time of the crank angle asynchronous purge for these cylinders. When it is determined that the accumulated time TSPGST1 is equal to or longer than the guard time KTST1, this routine is immediately terminated thereafter to avoid excessive purge.

  If it is determined that the accumulated purge time TSPGST1 has not yet reached the guard time KTST1, the D-VSVs 26 of the # 2 and # 3 cylinders are simultaneously opened (step 132). Apart from this routine, the ECU 40 executes a process of closing those D-VSVs 26 when the execution time TPGST1 has elapsed. In the present embodiment, the execution time TPGST1 is set to an appropriate value shorter than the cycle determination value KSYUK1. Therefore, according to the above processing, the D-VSV 26 of the # 2 and # 3 cylinders can be opened and closed only once during the period of KSYUK1.

  When the above processing ends, next, the accumulated purge TSPGST1 is updated by adding the execution time TPGST1 to the current accumulated purge time TSPGST1 (step 224). According to the above processing, each time the crank angle asynchronous purge is executed once for the # 2 and # 3 cylinders, the cumulative purge time TSPGST1 can be extended by the execution time TPGST1, and the value can be appropriately updated.

  After the processing in steps 132 and 134 is executed, until the time corresponding to the cycle determination value KSYUK1 has elapsed, it is determined in step 122 that the condition is not satisfied each time the routine shown in FIG. In this case, the processing cycle is terminated without any further processing thereafter. Then, when the time corresponding to the cycle determination value KSYUK1 has elapsed, the processing after step 124 is repeated again.

  As a result, according to the system of this embodiment, the crank angle synchronous purge is intermittently performed in the # 2 and # 3 cylinders until the number of purges reaches the guard number KCST1 or until the accumulated purge time reaches the guard time KTST1. Can proceed.

  The series of processes shown in FIG. 5 can be executed with the period determination value KSYUK1 and the execution time TPGST1 as constant values. However, if these values are appropriately changed in accordance with the state of the internal combustion engine 10, the control accuracy of the crank angle asynchronous purge can be further increased.

  FIG. 6 is a flowchart of the second routine executed in step 104 shown in FIG. 4 from the above viewpoint. This routine is executed only once immediately after the internal combustion engine 10 is started, prior to the start of the routine shown in FIG.

  In the routine shown in FIG. 6, first, the cycle determination value KSYUK1 is calculated (step 140). As shown in the frame of step 140, the ECU 40 stores a map that defines the cycle determination value KSYUK1 in relation to the coolant temperature THW. Here, according to this map, cycle determination value KSYUK1 is set. According to this map, the cycle determination value KSYUK1 is set to a larger value as the cooling water temperature THW is lower. The ISC opening that determines the amount of intake air during idling is set to be larger at lower temperatures. As a result, the intake pipe pressure MV is less likely to be negative at lower temperatures. In order to stably purge the evaporated fuel in an environment in which the intake pipe pressure MV is difficult to be negative, it is desirable that the crank angle asynchronous purge period is large. According to the processing of step 140, the cycle determination value KSYUK1 can be set so as to meet the request. For this reason, according to the system of the present embodiment, the evaporated fuel can be always stably supplied to the internal combustion engine 10 without being affected by the temperature environment at the time of starting.

  In the routine shown in FIG. 6, next, the guard count KCST1 is calculated (step 142). As shown in the frame of step 142, the ECU 40 stores a map that defines the guard count KCST1 in relation to the cooling water temperature THW. Here, guard count KCST1 is set according to this map. According to this map, the guard count KCST1 is set to a larger value as the cooling water temperature THW is lower. In the internal combustion engine 10, as the temperature is lower, it becomes difficult to secure the purge flow rate due to the effect of the ISC opening, and the amount of fuel required for starting increases due to the effect of friction. For this reason, it is appropriate that the guard number KCST1 for the crank angle asynchronous purge is set to a larger value as the cooling water temperature THW at the start is lower. According to the processing of step 142, it is possible to set the guard count KCST1 so as to meet the request.

  In the routine shown in FIG. 6, next, an execution time TPGST1 for one crank angle asynchronous purge is set (step 144). As shown in the frame of step 144, the ECU 40 stores a map that defines the execution time TPGST1 in relation to the coolant temperature THW and the ISC opening. Here, the execution time TPGST1 is set according to this map. According to this map, the execution time TPGST1 per time is set to a larger value as the cooling water temperature THW is lower and the ISC opening is larger. In order to appropriately purge the evaporated fuel necessary for start-up in a situation where the coolant temperature THW is low and the ISC opening is large, it is appropriate to secure a large execution time TPGST1 per time. According to the processing of step 144, the execution time TPGST1 can be set so as to meet the request.

  In the routine shown in FIG. 6, next, a guard time KTST1 is calculated (step 146). As shown in the frame of step 146, the ECU 40 stores a map that defines the guard time KTST1 in relation to the coolant temperature THW. Here, the guard time KTST1 is set according to this map. According to this map, the guard time KTST1 is set to a larger value as the cooling water temperature THW is lower. In the internal combustion engine 10, the total purge time required for purging the necessary amount of evaporated fuel becomes longer as the temperature is lower. According to the processing in this step 146, the guard time KTST1 can be determined so as to meet the request.

  As described above, according to the routine shown in FIG. 6, according to the starting state of the internal combustion engine 10, the cycle determination value KSYUK1, the crank angle asynchronous purge execution time TPGST1 per time, the crank angle asynchronous purge guard The number of times KCST1 and the guard time KTST1 can be set to appropriate values. Therefore, according to the routines shown in FIGS. 5 and 6, in the crank angle asynchronous purge for the # 2 and # 3 cylinders, the evaporative fuel can be supplied with high accuracy while promoting the evaporative fuel mixing.

  FIGS. 7 and 8 are flowcharts of routines executed to realize crank angle asynchronous purge for the # 1 and # 4 cylinders, that is, first and second routines executed in step 108 shown in FIG. is there. The routine shown in FIG. 7 is the same as the routine shown in FIG. 5 except that TSYUK1, KSYUK1, CPGST1, KCST1, TSPGST1, and KTST1 in FIG. 5 are replaced with TSYUK2, KSYUK2, CPGST2, KCST2, TSPGST2, and KTST2, respectively. The same. The routine shown in FIG. 8 is the same as the routine shown in FIG. 6 except that KSYUK1, KCST1, TPGST1, and KTST1 in FIG. 6 are replaced with KSYUK2, KCST2, TPGST2, and KTST2, respectively. Therefore, according to these routines, evaporative fuel can be supplied with high accuracy while promoting mixing of evaporative fuel in the crank angle asynchronous purge for the # 1 and # 4 cylinders.

  By the way, in Embodiment 1 mentioned above, although the internal combustion engine 10 is limited to a 4 cylinder type, this invention is not limited to this. That is, the internal combustion engine only needs to have a plurality of cylinder pairs such as a 6-cylinder type or an 8-cylinder type. Further, even when a 6-cylinder or 8-cylinder internal combustion engine is used, in the case of the first embodiment, the crank angle asynchronous purge is delayed in the cylinder pair that performs the intake stroke immediately after the generation of the cylinder discrimination signal. The same effect can be obtained.

  In the first embodiment described above, the D-VSV 26 corresponds to the “purge control valve” in the first aspect of the invention, and the crank angle sensor 46 has the first cylinder discrimination signal generating means and the second cylinder discrimination. It corresponds to a signal generating means. Here, the # 1 cylinder and the # 4 cylinder correspond to the “first discrimination cylinder” and the “second discrimination cylinder” in the first invention, respectively. Further, here, the “discrimination cylinder group purge means” in the first aspect of the present invention is realized by the ECU 40 executing the processing of steps 106 and 108.

  In the first embodiment described above, the # 2 cylinder and the # 3 cylinder correspond to the “non-discriminating cylinder” in the third aspect of the invention, and the ECU 40 executes the process of step 104 to execute the process. The “non-discriminating cylinder purge means” in the third invention and the “non-discriminating cylinder group purge means” in the fourth invention are realized.

Embodiment 2. FIG.
[Features of Embodiment 2]
Next, a second embodiment of the present invention will be described with reference to FIG. 9 and FIG. The system of the present embodiment can be realized by causing the ECU 40 to execute a routine shown in FIG. 10 described later in place of the routine shown in FIG. 4 in the system of the first embodiment.

  FIG. 9 is a timing chart for explaining the operation of the system of this embodiment. The timing chart shown in FIG. 9 is the same as the chart shown in FIG. 3 except that the start timing of the crank angle asynchronous purge for the # 2 and # 3 cylinders is delayed.

  In the first embodiment described above, the group purge for the # 2 and # 3 cylinders is started simultaneously with the start of the internal combustion engine 10. However, as described above, the stability of the crank angle asynchronous purge improves as the intake pipe pressure MV becomes negative, that is, as the purge start timing is delayed.

  As shown in FIG. 9C, in the present embodiment, after the internal combustion engine 10 is started, group purge for the cylinders # 2 and # 3 is started after a certain delay time, and then a certain delay time has elapsed. At the time, the group purge for the # 1 and # 4 cylinders is started. According to such a setting, the stability of the crank angle asynchronous purge for the # 2 and # 3 cylinders can be enhanced, and the startability of the internal combustion engine 10 can be further improved as compared with the case of the first embodiment. Can do.

[Specific Processing in Second Embodiment]
FIG. 10 is a flowchart of a main routine executed by the ECU 40 in the present embodiment in order to realize the above function. This routine is the same as the routine shown in FIG. 4 except that step 180 is inserted after step 102. In FIG. 10, the same steps as those shown in FIG. 4 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 10, when CCRNK ≦ −1 is established in step 102, that is, when it is determined that the cylinder determination is not completed, the cranking time TST is set to the second delay time KST2. It is determined whether or not it has been reached (step 180). While this determination is negative, the process of step 104 is jumped, and then the process of step 106 is executed.

  The second delay time KST2 is a time equal to or shorter than the delay time KST1 used for the determination in step 106. For this reason, when the condition of step 180 is denied, the determination of step 106 is inevitably denied. Therefore, if the condition of step 180 is negative, the current processing cycle is ended immediately thereafter.

  On the other hand, when it is determined in step 180 that the cranking time TST has reached the second delay time KST2, group purge for the # 2 and # 3 cylinders is executed in step 104. Thereafter, when the cranking time TST reaches the delay time KST1, the group purge for the # 1 and # 4 cylinders is executed (steps 106 and 108).

  As described above, according to the routine shown in FIG. 10, after starting the internal combustion engine 10, the crank angle asynchronous purge is executed in accordance with the rules shown in FIG. Therefore, according to the system of the present embodiment, it is possible to improve the startability of the internal combustion engine 10 by increasing the purge accuracy for the # 2 and # 3 cylinders as compared with the case of the first embodiment. it can.

Embodiment 3 FIG.
[Features of Embodiment 3]
Next, a third embodiment of the present invention will be described with reference to FIGS. The system of the present embodiment causes the ECU 40 to execute the routine shown in FIG. 12 described later in place of the routine shown in FIG. 4 in the system of the first embodiment, and further executes routines shown in FIG. 13 to FIG. This can be realized by executing.

  FIG. 11 is a timing chart for explaining an example of an operation realized in the system of the present embodiment. Hereinafter, this operation is referred to as “inversion operation”. More specifically, FIG. 11A shows the transition of the stroke in each cylinder realized in the case of the reversing operation. FIG. 11B is a chart for explaining a purge rule used in the inversion operation. Further, FIG. 11C is a chart for explaining conditions for executing the reversal operation.

  As shown in FIG. 11B, in the reversing operation, after the internal combustion engine 10 is started, first, the group purge for the # 1, # 4 cylinders is performed, and then the group purge for the # 2, # 3 cylinders is performed. The That is, in the reversal operation, the order of execution of the group purge for the # 2 and # 3 cylinders and the group purge for the # 1 and # 4 cylinders are reversed as compared with the case of the second embodiment described above (see FIG. 9). Yes. Hereinafter, the operation in the second embodiment is referred to as “normal operation” in order to distinguish it from the inversion operation.

  FIG. 11 illustrates the operation when the internal combustion engine 10 is started from the intake stroke of the # 1 cylinder. In this case, after the internal combustion engine 10 is started, a time of about 0.4 sec is secured until the first intake stroke in the # 3 cylinder is completed (that is, until the cylinder discrimination is completed). In the case of normal operation, as shown in FIG. 11C, 0.4 sec is the maximum time during which group purge can be performed on the # 2 and # 3 cylinders (purgeable time).

  On the other hand, the time required for group purge for supplying an appropriate amount of evaporated fuel to these cylinders varies depending on various factors. For example, the required time becomes longer as the cooling water temperature THW at the start of the internal combustion engine 10 is lower. And at the time of cold start, said required time may become longer than the purgeable time at the time of normal operation, as shown in FIG.11 (C).

  Under such circumstances, even if the group purge for the # 2 and # 3 cylinders is started simultaneously with the start of the internal combustion engine 10, the vaporized fuel is sufficiently supplied to the # 3 cylinder in the first intake stroke of the # 3 cylinder. I can't. If the amount of fuel supplied to the # 3 cylinder is insufficient, a proper explosion cannot be obtained in the subsequent explosion stroke, and unburned fuel may be exhausted.

  Therefore, the system according to the present embodiment performs the crank angle asynchronous purge by the normal operation only when the purgeable time longer than the purge required time for the cylinders # 2 and # 3 can be secured by the normal operation. If the required time for purging for the # 2 and # 3 cylinders cannot be ensured by the normal operation, the crank angle asynchronous purge is performed by the reversing operation.

  According to the reverse operation, after the internal combustion engine 10 is started, the group purge for the # 1 and # 4 cylinders is performed first. As shown in FIG. 11, when the internal combustion engine 10 is started from the intake stroke of the # 1 cylinder, this group purge may be ended before the intake stroke first performed in the # 4 cylinder is completed. That is, the purgeable time in this case is prolonged by the intake stroke in the # 4 cylinder as compared with the purgeable time for the # 2 and # 3 cylinders during normal operation. For this reason, the # 4 cylinder can suck a sufficient amount of evaporated fuel in the first intake stroke.

  In the case of the reverse operation, as described above, the group purge for the # 2 and # 3 cylinders is executed after the group purge for the # 1 and # 4 cylinders (hereinafter, this requirement is referred to as “delay condition”). Further, the group purge for the # 2 and # 3 cylinders is started so as to be completed before the end of the intake stroke executed for the first time in those cylinders after cylinder discrimination. More specifically, when the internal combustion engine 10 is started from the intake stroke of the # 1 cylinder, the group purge for the # 2 and # 3 cylinders is finished before the end of the first intake stroke in the # 2 cylinder. (Hereinafter, this requirement is referred to as “end condition”).

  According to the reversal operation rule described above, for example, in the case shown in FIG. 11, the execution timing of the crank angle asynchronous purge in the # 3 cylinder overlaps with the execution timing of the first intake stroke in that cylinder. If both are overlapped, a part of the evaporated fuel by the crank angle asynchronous purge is sucked into the # 3 cylinder and then discharged in an unburned state. The amount of fuel discharged can be made smaller as the group purge start timing for the # 2 and # 3 cylinders is delayed.

  The inversion operation in the present embodiment is executed so as to satisfy the above delay condition. That is, the group purge for the # 2 and # 3 cylinders is started after the start of the group purge for the # 1 and # 4 cylinders. As a result, according to the system of the present embodiment, it is possible to create a favorable situation for reducing the amount of fuel discharged from the # 2 or # 3 cylinder.

  In particular, in the present embodiment, the group purge start timing for the # 2 and # 3 cylinders during the reversing operation is delayed as much as possible as long as the above-described end condition is satisfied. As long as the above end condition is satisfied, a sufficient amount of evaporated fuel can be taken into the cylinder in the intake stroke that is executed for the first time in the # 2 or # 3 cylinder after cylinder discrimination. If the start time of the group purge for the # 2 and # 3 cylinders is delayed as long as that condition is satisfied, the amount of fuel discharged from those cylinders can be minimized. For this reason, according to the system of the present embodiment, excellent startability and emission characteristics can be imparted to the internal combustion engine 10 even when the reversing operation is performed.

[Specific Processing in Second Embodiment]
FIG. 12 is a flowchart of a main routine executed by the ECU 40 in the present embodiment in order to appropriately realize the normal operation and the inversion operation. This routine is the same as the routine shown in FIG. 10 except that steps 190 to 202 are inserted after step 102. Hereinafter, of the steps shown in FIG. 12, the same steps as those shown in FIG. 10 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 12, when CCRNK ≦ −1 is recognized in step 102, that is, when it is determined that the cylinder determination is not completed, the condition for switching from the normal operation to the reverse operation is satisfied. It is determined whether or not there is (step 190).

  When the start of the internal combustion engine 10 is requested, the ECU 40 calculates the purgeable time and the purge time required for the normal operation based on the coolant temperature THW and the like. Specifically, the time required until the second intake stroke (the first intake stroke at # 3 in FIG. 11) after the internal combustion engine 10 is started is calculated as the “purgeable time”. Further, assuming that the D-VSV 26 is opened immediately after the internal combustion engine 10 is started, a purge necessary for supplying a desired amount of evaporated fuel to the cylinder (# 3 cylinder in FIG. 11) in which the second intake stroke is performed. Time is calculated as "Purge time".

  In step 190, the purgeable time calculated as described above is compared with the purge time. If it is determined that purgeable time ≧ purge required time is satisfied, it is determined that the condition for switching to the reversing operation is not satisfied. In this case, the reverse purge flag NPGST is reset to “0” to indicate that the normal operation has been selected (step 192). Thereafter, the crank angle asynchronous purge by the normal operation is realized by executing the processing after step 180.

  On the other hand, if it is determined in step 190 that purgeable time ≧ purge required time is not satisfied, it is determined that the condition for switching to the reverse operation is satisfied. In this case, first, “1” is set to the inversion purge flag NPGST to indicate that the inversion operation has been selected (step 194).

  Next, it is determined whether the crank time TST has reached the third delay time KST3 (step 196). Then, while the establishment of TST ≧ KST3 is not recognized, step 198 is jumped. On the other hand, when the establishment is recognized, the group purge for the cylinders # 1 and # 4 is executed (step 198).

  According to the above processing, the group purge for the # 1 and # 4 cylinders can be started when the third delay time KST3 has elapsed after the internal combustion engine 10 is started. Note that the processing content of step 198 is substantially the same as the processing content of step 108, and therefore the description thereof is omitted here.

  In the routine shown in FIG. 12, it is next determined whether the crank time TST has reached the fourth delay time KST4 (step 200). Then, while the establishment of TST ≧ KST4 is not recognized, step 202 is jumped. On the other hand, when the establishment is recognized, the group purge for the # 2 and # 3 cylinders is executed (step 202).

  According to the above processing, the group purge for the # 1 and # 4 cylinders can be started when the fourth delay time KST4 has elapsed after the internal combustion engine 10 is started. Note that the processing content of step 198 is substantially the same as the processing content of step 108, and therefore the description thereof is omitted here.

  The fourth delay time KST4 is a value set so that both the “delay condition” and the “end condition” described above are satisfied. For this reason, according to the system of the present embodiment, the reversing operation in accordance with the rules shown in FIG. 11 is realized, so that the engine 10 has good startability and emission characteristics even under extremely cold conditions. Can be granted.

(Necessity of correction purge)
In the operation example shown in FIG. 11, the group purge for the # 1 and # 4 cylinders and the intake stroke for the # 4 cylinder are executed continuously. For this reason, the evaporated fuel supplied by crank angle asynchronous purge is sufficiently sucked into the # 4 cylinder. In this operation example, the group purge for the # 2 and # 3 cylinders and the intake stroke for the # 2 cylinder are continuously executed. For this reason, the evaporated fuel by the crank angle synchronous purge is sufficiently sucked into the # 2 cylinder.

  However, in the # 1 cylinder that forms a cylinder pair with the # 4 cylinder, the intake stroke is not started for a while after the group purge for these cylinders is completed. For the # 3 cylinder that forms a cylinder pair with the # 2 cylinder, the intake stroke is not started immediately after the group purge for these cylinders is completed.

  The concentration of the evaporated fuel sucked into the intake port by the crank angle asynchronous purge decreases with time. For this reason, in the operation example shown in FIG. 11, it is difficult for the # 1 cylinder and the # 3 cylinder to suck a sufficient amount of evaporated fuel in the intake stroke performed after the crank angle asynchronous purge is executed.

  Further, for the # 1 cylinder, the first intake stroke started simultaneously with the start of the internal combustion engine 10 overlaps with the first half of the group purge for the # 1 and # 4 cylinders. For this reason, a part of the evaporated fuel supplied by the crank angle asynchronous purge is slightly sucked into the # 1 cylinder in the first intake stroke and discharged in an unburned state. As a result, the amount of evaporated fuel remaining in the intake port of the # 1 cylinder is reduced by that amount.

  Also for the # 3 cylinder, the execution period of the intake stroke that is performed for the first time after the internal combustion engine 10 is started overlaps with the first half of the group purge for the # 2 and # 3 cylinders. For this reason, the fuel reduction that occurs in the intake port of the # 1 cylinder also occurs in the # 3 cylinder. Since the first intake stroke in the # 3 cylinder is executed later than the first intake stroke in the # 1 cylinder, that is, after the intake pipe pressure MV has been reduced to a negative pressure, it is rather in the intake port. This decrease in fuel is more likely to occur in the # 3 cylinder than in the # 1 cylinder.

  For the above reasons, in the case of the operation example shown in FIG. 11, that is, when the internal combustion engine 10 is started from the intake stroke of the # 1 cylinder and then crank angle asynchronous purge is performed by the reversing operation, The # 2 cylinder can sufficiently suck the evaporated fuel by the crank angle asynchronous purge, but the # 1 and # 3 cylinders cannot sufficiently suck the evaporated fuel amount by the crank angle asynchronous purge. Will occur.

  The same situation occurs when the internal combustion engine 10 is started from the intake stroke of the # 4 cylinder. In this case, specifically, the evaporated fuel by the crank angle asynchronous purge can be sufficiently sucked into the # 1 cylinder and the # 3 cylinder, but the # 4 cylinder and the # 2 cylinder can be sucked by the crank angle asynchronous purge. A situation occurs in which it is difficult to sufficiently inhale the amount of evaporated fuel.

  That is, when the crank angle asynchronous purge is executed by the reversal operation, a cylinder that performs an intake stroke immediately after generation of the cylinder discrimination signal (hereinafter referred to as “first intake cylinder”), and an intake stroke that follows the cylinder are performed. The cylinder (hereinafter referred to as “second intake cylinder”) sufficiently inhales the evaporated fuel by the crank angle asynchronous purge. On the other hand, in this case, the two cylinders that perform intake following the second intake cylinder (hereinafter referred to as “third intake cylinder” and “fourth intake cylinder”) simply perform crank angle asynchronous purge, It is difficult to sufficiently supply evaporated fuel. For this reason, when the crank angle asynchronous purge by the reversing operation is executed, the system of the present embodiment has a shortage of evaporated fuel after the crank angle asynchronous purge is completed for the third intake cylinder and the fourth intake cylinder. It was decided to perform a correction purge to compensate for the minute.

  In FIG. 11B, the white arrow indicated by reference numeral 50 in the column of the # 1 cylinder indicates the execution period of the correction purge for the third intake cylinder. In addition, a white arrow indicated by reference numeral 52 in the column of the # 3 cylinder in FIG. 11B indicates a correction purge execution period for the fourth intake cylinder. When these correction purges are executed, sufficient evaporated fuel can be supplied to the third intake cylinder and the fourth intake cylinder in the first intake stroke after cylinder discrimination. For this reason, according to the system of the present embodiment, when the crank angle asynchronous purge is executed by the reversing operation, extremely excellent startability can be realized.

  The necessity for the correction purge is not limited to the case where the reverse operation is used, but also occurs when the normal operation is used. Hereinafter, this necessity will be described with reference to FIG. 9 again. FIG. 9 is a timing chart showing the operation when the crank angle asynchronous purge is executed by the normal operation after the internal combustion engine 10 is started from the intake stroke of the # 1 cylinder as described above.

  In the operation example shown in FIG. 9, the intake stroke of the # 3 cylinder is executed so as to overlap at the end of the group purge for the # 2 and # 3 cylinders. For this reason, the evaporated fuel supplied by the crank angle asynchronous purge is sufficiently sucked into the # 3 cylinder. In this operation example, the group purge for the # 1 and # 4 cylinders and the intake stroke for the # 4 cylinder are continuously executed. For this reason, the vaporized fuel by the crank angle synchronous purge is sufficiently sucked into the # 4 cylinder.

  However, in the # 2 cylinder and the # 1 cylinder, the intake stroke is not started for a while after the crank angle asynchronous purge for these cylinders is completed. Further, for the # 1 cylinder, since the initial intake stroke overlaps with the start timing of the crank angle asynchronous purge, there is a possibility that a part of the purge fuel is exhausted in an unburned state. For this reason, in the case of the operation example shown in FIG. 9, that is, when the internal combustion engine 10 is started from the intake stroke of the # 1 cylinder and thereafter the crank angle asynchronous purge is performed by the normal operation, the # 3 cylinder and # 4 Although the cylinder can sufficiently suck the evaporated fuel by the crank angle asynchronous purge, the # 1 cylinder and the # 2 cylinder have a situation in which it is difficult to sufficiently suck the evaporated fuel amount by the crank angle asynchronous purge. .

  That is, when the crank angle asynchronous purge is executed by the normal operation, the cylinder that performs the intake stroke immediately before the generation of the cylinder discrimination signal (hereinafter referred to as “immediately intake cylinder”), and the intake stroke that follows the cylinder are performed The first intake cylinder sufficiently sucks the evaporated fuel by the crank angle asynchronous purge. On the other hand, in this case, the evaporated fuel is sufficiently supplied to the two cylinders that perform intake following the first intake cylinder, that is, the second intake cylinder and the third intake cylinder only by performing the crank angle asynchronous purge. It is hard to be done.

  Therefore, in the system of the present embodiment, when the crank angle asynchronous purge by the normal operation is executed, the second intake cylinder (# 2 cylinder in FIG. 9) and the third intake cylinder (# 1 cylinder in FIG. 9). On the other hand, after the crank angle asynchronous purge is completed, a correction purge for compensating for the shortage of the evaporated fuel is performed. When these correction purges are executed, sufficient evaporated fuel can be supplied to the second intake cylinder and the third intake cylinder in the first intake stroke after cylinder discrimination. For this reason, according to the system of the present embodiment, extremely excellent startability can be realized even when the crank angle asynchronous purge is executed by the normal operation.

(Crank angle synchronous purge start setting)
By the way, the system of this embodiment starts crank angle synchronous purge after execution of crank angle asynchronous purge. In order to prevent excessive fuel supply to the individual cylinders, the crank angle synchronous purge needs to be sequentially executed from the cylinder in which the evaporated fuel by the crank angle asynchronous purge has been properly lost from the intake port.

  As described above, the system of the present embodiment executes the crank angle asynchronous purge according to either the normal operation or the reverse operation. In the case of normal operation (see FIG. 9), the evaporated fuel in the intake port first disappears in the cylinder that performs the intake stroke immediately before the generation of the cylinder discrimination signal, that is, the immediately preceding intake cylinder (# 3 cylinder in FIG. 9). . Subsequently to the cylinder discrimination, the evaporated fuel in the intake port sequentially disappears in the order of the first intake cylinder, the second intake cylinder, and the third intake cylinder. For this reason, in the case of normal operation, it is appropriate to start the crank angle synchronous purge with the immediately preceding intake cylinder as the start cylinder after completion of cylinder discrimination.

  On the other hand, in the case of the reversing operation (see FIG. 11), the evaporated fuel in the intake port is the cylinder located at the intake top dead center when the cylinder discrimination signal is generated, that is, the first intake cylinder (# 4 cylinder in FIG. 11). In FIG. 4, the first disappearance occurs when the intake stroke is executed following the cylinder discrimination. Thereafter, the evaporated fuel in the intake port sequentially disappears as the intake stroke is executed in the order of the second intake cylinder, the third intake cylinder, and the fourth intake cylinder. Therefore, in the case of the reversing operation, it is appropriate to start the crank angle synchronous purge with the first intake cylinder as the start cylinder after the completion of the first intake stroke in the first intake cylinder.

  As described above, in the system of the present embodiment, the start timing of the crank angle synchronous purge and the start cylinder differ depending on whether the crank angle asynchronous purge is executed by the normal operation or the reverse operation. It will be. For this reason, in the system of the present embodiment, prior to the start of the crank angle synchronous purge, the start timing and the start cylinder of the crank angle synchronous purge can be appropriately set based on how the crank angle asynchronous purge is executed. is necessary.

  The correction purge and the crank angle synchronization purge described above can be realized by the ECU 40 appropriately executing the routines shown in FIGS. FIG. 13 is a main routine for realizing these functions. This routine is repeatedly started every time a pulse signal is issued from the crank angle sensor 46, that is, every time the crankshaft rotates 30 ° CA.

  When the routine shown in FIG. 13 is started, it is first determined whether or not the # 4 cylinder has reached the intake top dead center (step 210). If a cylinder discrimination signal corresponding to the # 4 cylinder has been issued in the current processing cycle, the discrimination in step 210 is affirmed. In this case, the crank angle counter CCRNK is set to 0 (step 212), and then 1 is set to the cylinder discrimination flag FTDC (step 214).

  On the other hand, if it is determined in step 210 that the # 4 cylinder has not reached the intake top dead center, it is then determined whether the # 1 cylinder has reached the intake top dead center (step 216). ). Specifically, it is determined here whether or not a cylinder determination signal corresponding to the # 1 cylinder has been generated. As a result, if the above determination is affirmed, 12 is set in the crank angle counter CCRNK (step 217), and then the process of step 214 is executed.

  If it is determined in step 216 that the # 1 cylinder has not reached the intake top dead center, it is next determined whether 1 is set in the cylinder discrimination flag FTDC (step 218). The cylinder discrimination flag FTDC is set to 0 by the initial process when the internal combustion engine 10 is started. For this reason, after the internal combustion engine 10 is started, 0 is set in FTDC while the cylinder discrimination signal has not yet been generated. In this case, the determination in step 218 is denied, -1 is set in the crank angle counter CCRNK (step 220), and then the number of intakes is cleared (step 222), and then the current processing cycle is terminated. .

  On the other hand, if this routine is performed after the cylinder discrimination is completed, in step 218, it is recognized that FTDC = 1. In this case, the crank angle counter CCRNK is incremented (step 224).

  In the routine shown in FIG. 13, following the process of step 214 or the process of step 224, the current crank angle matches the intake timing of any cylinder, that is, any cylinder It is determined whether the angle reaches the top dead center (step 226).

  Specifically, the ECU 40 affirms the determination of “intake timing” when the crank angle counter CCRNK matches any one of 0, 6, 12, and 18. For example, this determination is affirmed when the cylinder discrimination signal is first issued (CCRNK = 0 or 12). If this determination is affirmative, then the cylinder number of the intake cylinder is calculated (step 228). The ECU 40 stores the value of the crank angle counter CCRNK corresponding to the intake top dead center for each cylinder. Here, as shown in the frame of step 228, the intake cylinder number corresponding to the current CCRNK is calculated according to the storage.

  Next, the intake air number counter is incremented (step 230). The intake number counter is a counter for counting the number of intakes that occurred after cylinder discrimination, and is set to 0 by the initial process when the internal combustion engine 10 is started. Therefore, the intake number counter is set to 1 when the first intake timing is recognized, that is, when the first cylinder discrimination signal corresponding to the # 4 or # 1 cylinder is generated.

  In the routine shown in FIG. 13, it is next determined whether or not the current intake timing is the first timing (step 232). Specifically, it is determined whether or not the intake air number counter is 1. As a result, when it is determined that it is the first intake timing, a preparation for starting the crank angle synchronous purge and a series of processes for realizing the correction purge described above are executed.

  Here, first, a map number to be used in the current start purge is set (step 234). It is appropriate that the execution time TPG of the crank angle synchronous purge to be set for each cylinder is longer as the cooling water temperature THW is lower. For this reason, the ECU 40 stores a plurality of maps for determining the synchronous purge execution time TPG using the cooling water temperature THW as a parameter. As shown in the frame of step 234, the ECU 40 also stores a number setting map that defines the relationship between a specific cooling water temperature region and the map number adapted in that region. In step 234, the map number that matches the current coolant temperature THW is read according to the number setting map.

  Next, a setting map for the purge time TPG is selected (step 236). The ECU 40 stores a map in which the crank angle synchronous purge execution time TPG is determined in relation to the number of executions of the synchronous purge. A plurality of maps are prepared using the cooling water temperature THW as a parameter. In step 236, the map numbered in step 234 is selected from those maps as a map to be used in the current start purge. The map shown in the frame of step 236 is the map selected by the above processing.

  The crank angle synchronous purge is started when the engine speed NE starts to rise toward the idle speed. In the process in which the engine speed NE rises, the intake pipe pressure MV suddenly becomes negative. As the intake pipe pressure MV becomes negative, the purge flow rate per unit time increases and the purge time required to purge the desired fuel amount is shortened. For this reason, it is appropriate that the crank angle synchronous purge execution time TPG is gradually shortened as the number of purges increases.

  The execution time TPG map used in the present embodiment is set in relation to “the number of purges + 1” as shown in the frame of step 236. Here, “the number of purges” means the number of crank angle synchronous purges already performed. Therefore, “the number of purges + 1” is, for example, “1” at the timing when the first crank angle synchronization purge is to be executed, “2” at the timing when the second crank angle synchronization purge is to be executed, and the Nth crank angle synchronization. It becomes “N” at the timing when the purge should be executed.

  According to the above map, the execution time TPG decreases as the “purge number + 1” increases, and eventually converges to the minimum value. For this reason, according to the above map, the execution time TPG can always be appropriately set in the process in which the negative pressure of the intake pipe pressure MV advances as the engine speed NE rises.

  In the routine shown in FIG. 13, next, a setting map for the purge advance amount CRNKPG is selected (step 238). In the system of the present embodiment, the crank angle CRNKPGS for starting the crank angle synchronous purge in each cylinder is set to an angle advanced by the purge advance amount CRNKPG from the crank angle at which the intake stroke is started in that cylinder. I am going to do that. As in the case of the execution time TPG, the ECU 40 stores a plurality of maps in which the coolant advancement amount CRNKPG is set with the cooling water temperature THW as a parameter. In step 238, the map numbered in step 234 is selected from those maps as a map to be used in the current start purge. The map shown in the frame of step 238 is the map selected by the above processing.

  As described above, the purge time TPG of the crank angle synchronous purge is shortened as the number of purge executions increases. The crank angle synchronous purge needs to be finished before the intake stroke in the corresponding cylinder is finished. Therefore, if the purge execution time TPG is long, the purge advance amount CRNKPG needs to be increased.

  The map of the purge advance amount CRNKPG used in the present embodiment is set so that the purge advance amount CRNKPG decreases as the “purge number + 1” increases, as in the map of the execution time TPG. For this reason, according to the above map, it is possible to set an appropriate purge advance amount CRNKPG corresponding to the length of the execution time TPG.

  In the routine shown in FIG. 13, next, the starting cylinder STPG for crank angle synchronous purge is set, and further, the correction purge is executed for the insufficiently purged cylinder (step 240).

  FIG. 14 is a flowchart for explaining the contents of a series of processes executed in step 240 described above. As shown in FIG. 14, first, it is determined whether or not the reverse purge flag NPGST is 0 (step 250). The reverse purge flag NPGST is a flag that is set to “0” when the crank angle asynchronous purge is performed by the normal operation and is set to “1” when the purge is performed by the reverse operation (FIG. 12, step 192). 194). Therefore, according to the processing of this step 250, it can be determined whether the crank angle asynchronous purge is performed in the normal operation or the reverse operation.

  If it is confirmed that NPGST = 0, it can be determined that the crank angle asynchronous purge is executed in the normal operation (see FIG. 9). In this case, the cylinder that starts the intake stroke with a delay of three strokes from the current intake cylinder is set as the crank angle synchronous purge start cylinder STPG (step 252). In the case of normal operation, as described above, the intake cylinder immediately before the end of the intake stroke immediately before cylinder discrimination becomes the crank angle synchronous purge start cylinder (see FIG. 9). This step 252 is executed at the time of cylinder discrimination, that is, when the first intake cylinder starts intake. Therefore, according to the above rule, the immediately preceding intake cylinder (# 3 cylinder in FIG. 9) can be correctly set as the start cylinder.

  When the processing of step 252 is completed, it is next determined whether or not the current value of the crank angle counter CCRNK is 0 (step 254). If the establishment of CCRNK = 0 is recognized, it can be determined that the # 4 cylinder is the first intake cylinder. In this case, it can be further determined that the # 2 cylinder is the second intake cylinder and the # 1 cylinder is the third intake cylinder.

  When the crank angle asynchronous purge is executed in the normal operation, as described above, the second intake cylinder and the third intake cylinder are the target cylinders for the correction purge. Therefore, when the establishment of CCRNK = 0 is recognized, the # 2 cylinder and the # 3 cylinder can be specified as correction purge target cylinders at that time.

  When the above determination is made, first, a correction purge time # 2T for the # 2 cylinder is calculated (step 256). As shown in the frame of step 256, the ECU 40 stores a map that defines the correction purge time # 2T in relation to the crank time until cylinder discrimination is made. According to this map, the corrected purge time # 2T is set to a longer time as the crank time required for cylinder discrimination is shorter.

  When the crank time required for cylinder discrimination is short, it can be estimated that the cylinder discrimination is completed when the crankshaft slightly moves after the starter is turned on. In this case, it is predicted that the intake pipe pressure MV is maintained at a value near atmospheric pressure at the end of cylinder discrimination. That is, in this case, it can be determined that there is a high possibility that the supply amount of the evaporated fuel by the crank angle asynchronous purge is insufficient. According to the processing of step 256, in such a case, the correction purge time # 2T can be extended. For this reason, according to the system of the present embodiment, the shortage of the evaporated fuel amount due to the crank angle asynchronous purge can be appropriately compensated by the correction purge.

  When the above processing is completed, the ECU 40 executes output processing for the D-VSV 26 of the # 2 cylinder (step 258). Here, specifically, a signal requesting opening of the corrected purge time # 2T is supplied to the D-VSV 26 of the # 2 cylinder. As a result, a correction purge that compensates for the shortage of evaporated fuel is realized in the # 2 cylinder.

  In the routine shown in FIG. 14, next, the corrected purge time # 1T for the third intake cylinder, that is, the # 1 cylinder is calculated (step 260). As shown in the frame of step 260, the ECU 40 stores a map that defines the corrected purge time # 1T in relation to the crank time required for cylinder discrimination. According to this map, the corrected purge time # 1T is set to a longer time as the cylinder discrimination time is shorter for the same reason as that for setting the corrected purge time # 2T.

  In the third intake cylinder, part of the evaporated fuel by the crank angle asynchronous purge is discharged to the exhaust system. As a result, the third intake cylinder needs to be subjected to more correction purge with respect to the second intake cylinder. Corresponding to this necessity, the map of the corrected purge time # 1T is shifted in the long time direction as a whole compared with the map of the corrected purge time # 2T. Therefore, according to the processing in step 260, the correction purge time # 1T for the # 1 cylinder can be set appropriately.

  When the above processing is completed, the ECU 40 executes output processing for the D-VSV 26 of the # 1 cylinder (step 262). Here, specifically, a signal requesting opening of the corrected purge time # 1T is supplied to the D-VSV 26 of the # 1 cylinder. As a result, a correction purge that compensates for the shortage of evaporated fuel is realized in the # 1 cylinder.

  In the routine shown in FIG. 14, if it is determined in step 254 that CCRNK = 0 is not satisfied, it can be determined that the # 1 cylinder is the first intake cylinder. In this case, it can be determined that the # 3 cylinder and the # 4 cylinder are the second intake cylinder and the third intake cylinder, respectively, and are the targets of the correction purge.

  If the above determination is made, processing similar to the processing in steps 256 to 262 described above is executed for cylinders # 3 and # 4 (steps 264 to 270). As a result, in each of the # 3 cylinder and the # 4 cylinder, an appropriate correction purge that compensates for the shortage of evaporated fuel is realized.

  In the routine shown in FIG. 14, if it is determined in step 250 that NPGST = 0 is not established, it can be determined that the crank angle asynchronous purge is executed in the reverse operation (see FIG. 11). In this case, the cylinder that starts the intake stroke with a delay of four strokes from the current intake cylinder is set as the crank angle synchronous purge start cylinder STPG (step 272). In the case of the reversal operation, as described above, the first intake cylinder that starts the intake stroke at the same time as the cylinder determination becomes the crank angle synchronous purge start cylinder (see FIG. 11). Since this step 272 is executed at the time of cylinder discrimination, according to the above rules, the first intake cylinder (# 4 cylinder in FIG. 11) can be correctly set as the start cylinder.

  When the processing in step 272 is completed, it is next determined whether or not the current value of the crank angle counter CCRNK is 0 (step 274). If the establishment of CCRNK = 0 is recognized, it can be determined that the # 4 cylinder is the first intake cylinder. In this case, it can be further determined that the # 1 cylinder is the third intake cylinder and the # 3 cylinder is the fourth intake cylinder.

  When the crank angle asynchronous purge is executed in the reverse operation, as described above, the third intake cylinder and the fourth intake cylinder are the target cylinders for the correction purge. Therefore, if the establishment of CCRNK = 0 is recognized, it can be determined that the # 1 cylinder and the # 3 cylinder are the target cylinders for the correction purge at that time.

  In the routine shown in FIG. 14, when the above determination is made, the same processing as the processing in steps 256 to 262 described above is executed for the # 1 cylinder and the # 3 cylinder (steps 276 to 282). As a result, in each of the # 3 cylinder and the # 4 cylinder, an appropriate correction purge that compensates for the shortage of evaporated fuel is realized.

  On the other hand, if it is determined in step 274 that CCRNK = 0 is not satisfied, it can be determined that the # 1 cylinder is the first intake cylinder. In this case, it can be determined that the # 4 cylinder and the # 2 cylinder are the third intake cylinder and the fourth intake cylinder, respectively, and they are the targets of the correction purge.

  When the above determination is made, processing similar to the processing in steps 256 to 262 described above is executed for the # 4 cylinder and # 2 cylinder (steps 284 to 290). As a result, in each of the # 4 cylinder and the # 2 cylinder, an appropriate correction purge that compensates for the shortage of evaporated fuel is realized.

  Steps 228 to 240 shown in FIG. 13 and steps 250 to 290 shown in FIG. 14 are executed as a series of processes when a cylinder discrimination signal is first generated after the internal combustion engine 10 is started. When the crank angle sensor 46 generates a pulse signal after the next time, the condition of step 226 or the condition of step 232 is negated in the routine shown in FIG.

  When the condition of step 136 or step 142 is negative, the purge amount (crank angle synchronous purge execution time TPG) and the purge start timing (start crank angle CRNKPGS) are set (step 300). Specifically, first, an execution time TPG to be applied to the next crank angle synchronous purge is calculated based on the map selected in step 236 and the number of executed purges at the current time. Next, the purge advance amount CRNKPG to be applied to the next crank angle synchronous purge is calculated based on the map selected in step 238 and the number of purges that have been executed at the present time.

  When the above processing is completed, the next crank angle synchronous purge start crank angle CRNKPGS is set (step 302). Here, first, the intake crank angle (intake CRNK) of the cylinder to be purged is read. Next, a value obtained by advancing the intake CRNK by the purge advance amount CRNKPG is set as the purge start crank angle CRNKPGS.

Next, the contents of specific processing executed by the ECU 40 to realize crank angle synchronous purge, that is, to actually open and close the D-VSV 26 will be described.
FIG. 15 is a flowchart of a routine executed by the ECU 40 for the above purpose. The routine shown in FIG. 15 is started every time the crank angle sensor 46 generates a pulse signal. When this routine is started, first, it is determined whether or not the count value of the crank angle counter CCRNK coincides with the purge start crank angle CRNKPGS (step 310).

  As a result, if the establishment of CCRNK = CRNKPGS is denied, it is determined that the start of crank angle synchronous purge is not requested, and the current processing cycle is immediately terminated. On the other hand, when the establishment of CCRNK = CRNKPGS is recognized, the process for executing the crank angle synchronous purge is advanced.

  Here, first, the number of executions of crank angle synchronous purge is incremented (step 302). Next, it is determined whether the current synchronous purge is the first synchronous purge or, specifically, whether the number of executions of the synchronous purge is “1” (step 304).

  If it is determined that the current purge is the first synchronous purge, the purge target is set to the start cylinder STPG set by the processing of step 252 or step 272 (see FIG. 14) (step 316). Next, the D-VSV 26 of the starting cylinder STPG is opened (step 318). Thereafter, the ECU 40 closes the D-VSV 26 when the execution time TPG set by the process of step 300 (see FIG. 13) has elapsed. According to the above processing, in the start cylinder STPG, the crank angle synchronous purge is executed over the execution time TPG from the purge start crank angle CRNKPGS.

  According to the processing of steps 300 and 302 described above (see FIG. 13), every time the crank angle synchronous purge is executed, the purge execution time TPG and the start crank angle CRNKPGS are rewritten to the values to be applied to the next purge. It is done. When the count value of the crank angle counter CCRNK coincides with the newly rewritten start crank angle CRNKPGS, the condition of step 310 shown in FIG. 15 is satisfied, and the processing after step 312 is executed again.

  This time, since the condition of step 314 is not satisfied, the process of step 320 is executed following the process. Here, a cylinder delayed by one stroke with respect to the currently stored purge cylinder is set as a new purge target. Thereafter, the process of step 318 is executed for the D-VSV 26 of the cylinder newly targeted for purging. By repeatedly executing the above processing, the crank angle synchronization purge is executed appropriately in each cylinder. As a result, according to the system of the present embodiment, the internal combustion engine 10 can be started extremely well.

  In the above-described third embodiment, the ECU 40 estimates the time required for the crank angle asynchronous purge that should be ensured immediately after the internal combustion engine 10 is started, thereby realizing the “purge required time estimating means” in the sixth invention. In addition, the “comparison means” according to the sixth aspect of the present invention is realized by executing the processing of step 190. In addition, here, the ECU 40 executes the process of step 104 shown in FIG. 12, so that the “normal control means” in the sixth invention executes the process of step 202 described above. "Inversion control means" is realized respectively.

Embodiment 4 FIG.
[Features of Embodiment 4]
Next, a fourth embodiment of the present invention will be described with reference to FIGS. The system of the present embodiment can be realized by causing the ECU 40 to execute routines shown in FIGS. 17 and 18 described later in the system of the first embodiment.

  In the above-described systems of the first to third embodiments, after the internal combustion engine 10 is started, before starting the cylinder discrimination signal, the crank angle asynchronous purge is performed to increase the start response. However, since the crank position at the start of the internal combustion engine 10 is not always stable, it is difficult to always supply desired fuel to each cylinder by the crank angle asynchronous purge method.

  By the way, in the internal combustion engine 10, the # 1 cylinder piston and the # 4 cylinder piston operate in the same phase in relation to the rotational position of the crankshaft, although there is a stroke difference of 360 °. . The crank angle sensor 46 used in this embodiment can generate a signal corresponding to the rotational position of the crankshaft after the pistons of those cylinders reach the position of 210 ° CA before top dead center. .

  Therefore, the ECU 40 cannot determine which of the # 1 cylinder and the # 4 cylinder is the first intake cylinder until the cylinder determination signal is issued, but from 210 ° CA before the cylinder determination signal is generated, In relation to the piston positions of the # 1 cylinder and the # 4 cylinder, the rotational position of the crankshaft can be specified. In other words, the ECU 40 of the present embodiment cannot specify the crank angle within 720 ° CA until the cylinder discrimination signal is issued, but is 360 ° CA from the time 210 ° CA before the cylinder discrimination signal is issued. It is possible to specify the crank angle.

  After the internal combustion engine 10 is started, it is not always necessary to specify the crank angle within 720 ° CA when performing the group purge for the # 1 cylinder and the # 4 cylinder. That is, if the crank angle can be specified within 360 ° CA, it is possible to perform group purge for the # 1 cylinder and the # 4 cylinder in synchronization with the crank angle. Also, if the group purge is started from 210 ° CA before the cylinder discrimination signal is generated, the purge start timing is greatly delayed compared to when the crank angle asynchronous purge is executed. There is nothing. Therefore, in this embodiment, immediately after the internal combustion engine 10 is started, early purge by crank angle synchronous purge is executed instead of crank angle asynchronous purge.

  FIG. 16 is a timing chart for explaining the operation of the system of this embodiment. More specifically, FIG. 16A shows the transition of the stroke of each cylinder after the internal combustion engine 10 is started. FIG. 16B is a chart for explaining the purge rules used in the present embodiment.

  As shown in FIG. 16B, in this embodiment, after starting the internal combustion engine 10, a crank angle signal is generated at 210 ° CA before cylinder discrimination, and at the same time, the group purge for the # 1, # 4 cylinders is performed. Is started. The group purge for the # 1 and # 4 cylinders only needs to be completed immediately after the cylinder discrimination and before the intake stroke performed in the # 1 or # 4 cylinder ends. Therefore, a sufficient purgeable time can be secured for this group purge.

  When the group purge is started at 210 ° CA before cylinder discrimination, the period of 30 ° CA after the start of the group purge overlaps with the intake stroke of the # 1 cylinder or the # 4 cylinder. However, at this stage, the intake pipe negative pressure MV is hardly negative. For this reason, the amount of fuel sucked into the cylinder in the intake stroke, that is, the amount of fuel discharged in an unburned state can be suppressed very slightly.

  In the system according to the present embodiment, after the cylinder discrimination signal is generated, the crank angle synchronous purge is sequentially executed in each cylinder. At this time, for the # 1 cylinder and the # 4 cylinder, the crank angle synchronous purge is executed so that the influence of the group purge executed before the cylinder discrimination is offset. For example, in the case shown in FIG. 16, when the cylinder discrimination signal is generated, the # 4 cylinder reaches the intake top dead center. At this time, an appropriate amount of fuel is supplied to the # 4 cylinder by the group purge. Therefore, the first crank angle synchronous purge for the # 4 cylinder is corrected so that the fuel purge amount becomes substantially zero.

  When the intake stroke of the # 4 cylinder is finished, the intake stroke of the # 2 cylinder is then started. Group purge is not performed for the # 2 cylinder. For this reason, the # 2 cylinder is supplied with the fuel amount necessary for obtaining an appropriate explosion by crank angle synchronous purge without being corrected for reduction.

  When the intake stroke of the # 2 cylinder is completed, the intake stroke of the # 1 cylinder is then started. Group purge is performed for the # 1 cylinder. However, for this cylinder, there is a certain amount of time until the intake stroke starts after the end of the group purge. For this reason, the # 1 cylinder is supplied with fuel for compensating for a decrease in fuel concentration in the intake port by crank angle synchronous purge.

  When the intake stroke of the # 1 cylinder is finished, the intake stroke of the # 3 cylinder is then started. No group purge is performed for the # 3 cylinder. For this reason, as in the case of the # 2 cylinder, the amount of fuel necessary for obtaining an appropriate explosion is supplied to the # 3 cylinder by crank angle synchronous purge without being corrected for reduction.

  After the cylinder discrimination signal is generated, when the intake stroke of all the cylinders is completed, the effect of the group purge disappears in all the cylinders. For this reason, after the intake stroke is completed, the crank angle synchronous purge is executed at an appropriate timing without performing the reduction correction in each cylinder.

[Specific Processing in Embodiment 4]
The crank angle synchronous purge according to the rules shown in FIG. 16 can be realized by the ECU 40 executing the routines shown in FIGS. 17 and 18. FIG. 17 is a flowchart of a routine that is executed to realize group purge by crank angle synchronization for the # 1 and # 4 cylinders immediately after the internal combustion engine 10 is started. This routine is the same as the routine shown in FIG. 4 except that steps 104 to 108 are replaced with steps 330 to 334. Hereinafter, of the steps shown in FIG. 17, the same steps as those shown in FIG. 4 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 17, when it is determined in step 102 that CCRNK ≦ −1 is satisfied, that is, when it is determined that the cylinder determination signal has not yet been generated, the value of the crank angle counter CCRNK is set to the initial value. It is determined whether the set value is KCCRNK (step 330). The crank angle counter CCRNK is set to a minimum value (negative value) by initial processing when the internal combustion engine 10 is started. Thereafter, when the crank angle sensor issues a −210 ° CA corresponding signal at a crank position of 210 ° CA before cylinder discrimination, an initial set value KCCRNK (for example, −7) is set in CCRNK. Therefore, according to the processing in step 330, it is substantially determined whether or not the rotational position of the crankshaft has reached 210 ° CA before the cylinder determination after the internal combustion engine 10 is started.

  If it is determined that CCRNK = KCCRNK does not hold, it can be determined that the time to start the group purge for the # 1 and # 4 cylinders has not come. In this case, the current processing cycle is immediately terminated. On the other hand, when the establishment of CCRNK = KCCRNK is recognized, it can be determined that the start time of the group purge for the # 1 and # 4 cylinders has come. In this case, next, the group purge execution time TPGST11 is calculated (step 332).

  As shown in the frame of step 332, the ECU 40 stores a map that defines the execution time TPGST11 in relation to the cooling water temperature THW. This map is determined so that the execution time TPGST11 becomes longer as the cooling water temperature THW is lower.

  The friction of the internal combustion engine 10 increases as the cooling water temperature THW decreases. For this reason, the internal combustion engine 10 becomes difficult to start as the coolant temperature THW is lower. Further, in the internal combustion engine 10, control is performed such that the ISC opening is increased and the amount of idle air is increased as the coolant temperature THW is lower. Then, as the amount of idle air increases, the intake pipe pressure MV at the time of start-up becomes difficult to be negative, and as a result, the purge of evaporated fuel is less likely to occur.

  According to the process of step 332, the lower the coolant temperature THW, the longer the group purge execution time TPGST11 by synchronizing the crank angle, and the situation where the evaporated fuel is more easily purged can be created. Therefore, according to the system of the present embodiment, the group purge execution time TPGST11 can be appropriately set so that an appropriate amount of evaporated fuel is always purged regardless of the coolant temperature THW at the time of starting.

  In the routine shown in FIG. 17, next, the D-VSV 26 of the # 1 cylinder and the # 4 cylinder are simultaneously opened (step 334). Apart from this routine, the ECU 40 executes a process of closing those D-VSVs 26 when the execution time TPGST11 has elapsed. According to these processes, after the internal combustion engine 10 reaches the crank angle of −210 ° CA, the group purge for the # 1 and # 4 cylinders can be performed by crank angle synchronization over the execution time TPGST11. it can.

  FIG. 18 is a flowchart of a routine executed by the ECU 40 to sequentially perform crank angle synchronous purge in each cylinder after generation of the cylinder discrimination signal. This routine is started at the same time as the generation of the cylinder discrimination signal, and thereafter repeatedly started every predetermined crank rotation angle.

  In the routine shown in FIG. 18, first, a reference value for the crank angle synchronous purge execution time TPG is set (step 340). The reference value of the execution time TPG set here is the execution time TPG ignoring the effect of the group purge on the # 1, # 4 cylinders, that is, the evaporated fuel necessary for obtaining an appropriate explosion for each cylinder. Is the time itself to supply.

  As shown in the frame of step 340, the ECU 40 stores a map in which the reference value of the execution time TPG is defined in relation to “the number of purges + 1”. Here, “the number of purges” means the number of executions of the crank angle synchronous purge executed after the generation of the cylinder discrimination signal. Therefore, “the number of purges + 1” is, for example, “1” at the timing when the first crank angle synchronization purge is to be executed, “2” at the timing when the second crank angle synchronization purge is to be executed, and the Nth crank angle synchronization. It becomes “N” at the timing when the purge should be executed.

  In the system of this embodiment, simultaneously with the generation of the cylinder discrimination signal, a crank angle synchronous purge is required for the first intake cylinder (# 4 cylinder in FIG. 16) (in reality, the purge is performed to correct the influence of the group purge). Is not done). That is, the first crank angle synchronous purge is required for the first intake cylinder. Thereafter, the second crank angle synchronous purge, the third crank angle synchronous purge, and the fourth crank angle synchronous purge are required for the second intake cylinder, the third intake cylinder, and the fourth intake cylinder, respectively. Is done.

  The first intake cylinder sucks the evaporated fuel in the first intake stroke, and then performs an explosion stroke when the third intake cylinder performs the intake stroke. Therefore, according to the system of the present embodiment, the first explosion of the internal combustion engine 10 occurs at the timing when the third intake cylinder performs the intake stroke. The engine speed NE rises rapidly from the time when the intake stroke starts in the fourth intake cylinder after the first explosion occurs. Then, the intake pipe pressure MV abruptly becomes negative after the rise, that is, around the end of the intake stroke in the fourth intake cylinder.

  The fourth crank angle synchronous purge, that is, the first crank angle synchronous purge for the fourth intake cylinder needs to be completed before the intake stroke in the cylinder ends. Therefore, the fourth crank angle synchronous purge needs to be performed before the intake pipe pressure MV becomes negative. On the other hand, the fifth crank angle synchronous purge can be performed in an environment in which the intake pipe pressure MV suddenly becomes negative. For this reason, the reference value of the execution time TPG necessary for purging the desired amount of evaporated fuel is greatly different between the first to fourth crank angle synchronous purges and the fifth and subsequent crank angle synchronous purges. Become.

  For the reasons described above, in the map shown in the frame of step 340, the TPG for the first to fourth crank angle synchronous purges is set long, and the TPG for the fifth and subsequent crank angle synchronous purges is set short. For this reason, according to the process of step 340, an appropriate reference value for the execution time TPG can be set for each crank angle synchronous purge executed after the cylinder discrimination is completed.

  In the routine shown in FIG. 18, it is next determined whether or not the initial signal generation time TCRNK is equal to or greater than the determination value KTCRNK (step 342). The initial signal generation time TCRNK is a time required from when the internal combustion engine 10 is started until a signal corresponding to 210 ° CA before cylinder discrimination is issued. Therefore, when the establishment of TCRNK ≧ KTCRNK is recognized, it can be determined that it took a relatively long time to realize the crank rotation position of 210 ° CA before cylinder discrimination.

  If it takes a long time to reach 210 ° CA before cylinder discrimination, it can be estimated that the crank angular velocity during cranking is slow. In this case, it can be estimated that the negative pressure of the intake pipe pressure MV has hardly progressed at the start of the group purge by crank angle synchronization. For this reason, if the establishment of TCRNK ≧ KTCRNK is recognized in step 342, the correction time STPG for offsetting the influence is calculated on the assumption that the supply amount of the evaporated fuel amount by the group purge is small. (Step 344).

  Next, the final value of the crank angle synchronous purge execution time TPG is obtained by subtracting the correction time STPG set by the process of step 344 from the reference value of the execution time TPG set by the process of step 340. Is calculated (step 346).

  As shown in the frame of step 344, the ECU 40 stores a map in which the correction time STPG to be used when the amount of fuel vapor by group purge is small is defined in relation to “purge time + 1”. According to this map, the correction time STPG is set only for the first crank angle synchronous purge and the third crank angle synchronous purge. Further, according to this map, a correction time STPG substantially equal to the reference time of the execution time TPG is set for the first crank angle synchronous purge, and for the third crank angle synchronous purge, A correction time STPG that is about 1/2 to 1/3 of the reference value is set.

  According to this setting, the final execution time TPG for the first crank angle synchronous purge is almost zero, and the final execution time TPG for the third crank angle synchronous purge is the TPG reference. The value is sufficiently smaller than the value. For other crank angle synchronous purges, the TPG reference value set in step 340 is set as the final execution time TPG as it is. That is, according to the above setting, the execution time TPG of each crank angle synchronous purge is determined so as to coincide with the purge rule shown in FIG. 16 on the assumption that the amount of evaporated fuel by the group purge is relatively small. be able to.

  In the routine shown in FIG. 18, if the establishment of TCRNK ≧ KTCRNK is denied in step 342, it can be determined that the crank rotational position of 210 ° CA before cylinder discrimination has been realized in a short time after starting the internal combustion engine 10. . In this case, it can be estimated that the crank angular speed at the time of cranking is fast and that the negative pressure of the intake pipe pressure MV has progressed to some extent before the start of the group purge. For this reason, if it is denied in step 342 that TCRNK ≧ KTCRNK is established, a correction time STPG for offsetting the influence is calculated on the assumption that a large amount of evaporated fuel is supplied by the group purge. (Step 348).

  As shown in the frame of step 348, the ECU 40 stores a map in which the correction time STPG to be used when the amount of fuel evaporated by group purge is large is defined in relation to “purge time + 1”. In this map, the correction time STPG for the first to fourth crank angle synchronous purge is set to be slightly larger than the value determined in the map shown in the frame of step 344.

  When the map shown in the frame of step 348 is used, the final execution time TPG for the first crank angle synchronous purge is almost zero, and the final execution time TPG for the third crank angle synchronous purge is The value is sufficiently small compared to the TPG reference value, and the final value of the execution time TPG for the second and fourth crank angle synchronous purges is also slightly smaller than the TPG reference value. Become. When a large amount of evaporated fuel flows into the intake ports of the # 1 and # 4 cylinders due to the group purge, a part of them also flows into the intake ports of # 2 and # 3. According to the above processing, the influence time can be offset and the execution time TPG of each crank angle synchronous purge can be determined so as to coincide with the purge rule shown in FIG.

  In the routine shown in FIG. 18, the purge advance amount CRNKPG is set following the processing of step 346 (step 350). As shown in the frame of step 350, the ECU 40 stores a map in which the purge advance amount CRNKPG is determined in relation to “the number of purges + 1”. Here, the purge advance amount CRNKPG is set according to the map.

  Next, the start crank angle CRNKPGS for the next crank angle synchronous purge is set (step 352). Here, first, the intake crank angle (intake CRNK) of the cylinder to be purged is read. Next, a value obtained by advancing the intake CRNK by the purge advance amount CRNKPG is set as the purge start crank angle CRNKPGS.

  Next, it is determined whether or not the count value of the crank angle counter CCRNK matches the purge start crank angle CRNKPGS (step 354). As a result, when the establishment of CCRNK = CRNKPGS is recognized, the D-VSV 26 of the corresponding cylinder is opened (step 356). The opened D-VSV 26 is closed by another routine process when the execution time TPG set in step 346 has elapsed. Finally, the number of purges is incremented and the current processing cycle is terminated.

  As described above, according to the routines shown in FIGS. 17 and 18, the group purge for the # 1 and # 4 cylinders and the subsequent crank angle synchronous purge can be realized according to the purge rule shown in FIG. . For this reason, according to the system of the present embodiment, it is possible to achieve excellent start-up response and good emission characteristics without using crank angle asynchronous purge.

  In the fourth embodiment described above, the crank angle sensor 46 that generates a signal at 210 ° CA before cylinder discrimination corresponds to the “crank angle signal generating means” in the seventh aspect of the invention, and the cylinder The position of 210 ° CA before determination corresponds to “a position that is back by a predetermined crank angle from the position that reaches the specific state” in the seventh aspect of the invention.

Embodiment 5. FIG.
[Features of Embodiment 5]
Next, a fifth embodiment of the present invention will be described with reference to FIGS. The system of the present embodiment is realized by causing the ECU 40 to execute the routines shown in FIGS. 20 and 21 described later instead of the routines shown in FIGS. 17 and 18 described above in the system of the fourth embodiment. Can do.

  In the system of the fourth embodiment described above, the target of early group purge by crank angle synchronization is limited to only # 1 and # 4 cylinders. That is, in the fourth embodiment, for the # 2 and # 3 cylinders, early purge by group purge is not performed, but only crank angle synchronous purge after cylinder discrimination is performed.

  Immediately before the generation of the cylinder discrimination signal, the intake stroke is performed in the # 2 cylinder or the # 3 cylinder. For this reason, if purging of those cylinders is performed before the cylinder discrimination signal is generated, a part of the evaporated fuel supplied by the purge is blown out. According to the method of the fourth embodiment described above, it is possible to reliably prevent such blow-by from occurring in the # 2 cylinder and the # 3 cylinder.

  However, for the # 2 and # 3 cylinders, it is desirable that the purge start time be early in order to ensure the purge time. Further, if the purge start timing is advanced, gas mixing in the intake port is promoted, and combustibility in the # 2 and # 3 cylinders is also improved. If the group purge is performed on the # 2 and # 3 cylinders, starting at the time when the cylinder discrimination signal is generated or immediately before it is generated, fuel blowout from these cylinders is prevented and The purge time can be advanced compared to the case of the fourth embodiment.

  FIG. 19 is a timing chart for explaining a purge rule used in the present embodiment. As shown in FIG. 19B, in this embodiment, the group purge for the # 2 and # 3 cylinders is started in synchronization with the crank angle simultaneously with the generation of the cylinder discrimination signal. As a result, the first purge time for the fourth intake cylinder (# 3 cylinder in FIG. 19) is remarkably advanced as compared with the fourth embodiment. Therefore, according to the system of the present embodiment, in particular, the startability of the internal combustion engine 10 can be improved by improving the combustibility of the fourth intake cylinder at the start.

[Specific Processing in Embodiment 5]
The crank angle synchronous purge according to the rules shown in FIG. 19 can be realized by the ECU 40 executing the routines shown in FIGS. FIG. 20 is executed particularly in order to realize a group purge for the # 1 and # 4 cylinders and a group purge for the # 2 and # 3 cylinders immediately after the internal combustion engine 10 is started. It is a flowchart of a routine. This routine is the same as the routine shown in FIG. 17 except that steps 360 to 364 are added after step 334. Hereinafter, of the steps shown in FIG. 20, the same steps as those shown in FIG. 17 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 20, it is determined whether the value of the crank angle counter CCRNK is the second initial set value KCCRNK2 following the processing of steps 330 to 334 (step 360). In this embodiment, a negative integer is counted in the crank angle counter CCRNK according to the output of the crank angle sensor 46 after the time of 210 ° CA before cylinder discrimination, and is set to 0 or 12 simultaneously with cylinder discrimination. On the other hand, the second initial set value KCCRNK2 is the crank position where the group purge for the # 2 and # 3 cylinders should be started, that is, the earliest that can start the group purge for those cylinders without causing fuel blow-off. It is set to a preset value as a value representing the crank position. In the present embodiment, since the group purge for the # 2 and # 3 cylinders is started simultaneously with the cylinder discrimination, the second initial set value KCCRNK2 is particularly set to “0” or “12”.

  If the condition of CCRNK = KCCRNK2 is denied in step 360, it can be determined that the start time of the group purge for the # 2 and # 3 cylinders has not come. In this case, the current processing cycle is immediately terminated. On the other hand, when the establishment of CCRNK = KCCRNK2 is recognized, it can be determined that the start time of the group purge for the # 2 and # 3 cylinders has come. In this case, next, the group purge execution time TPGST12 is calculated (step 362).

  As shown in the frame of step 362, the ECU 40 stores a map that defines the execution time TPGST12 in relation to the cooling water temperature THW. This map is determined so that the execution time TPGST12 becomes longer as the coolant temperature THW is lower for the same reason as the map of TPGST11 used in step 332. In step 362, the execution time TPGST12 is calculated by referring to the map.

  In the routine shown in FIG. 20, the D-VSV 26 of the # 2 cylinder and the # 3 cylinder is then opened simultaneously (step 364). Apart from this routine, the ECU 40 executes a process of closing those D-VSVs 26 when the execution time TPGST12 has elapsed. According to these processes, after the cylinder discrimination signal is generated, the group purge for the # 2 and # 3 cylinders can be performed by crank angle synchronization over the execution time TPGST12.

  FIG. 21 is a flowchart of a routine executed by the ECU 40 in this embodiment in order to sequentially perform crank angle synchronous purge in each cylinder after generation of the cylinder discrimination signal. This routine is the same as the routine shown in FIG. 18 except that step 340 is replaced with step 370 and steps 344 to 350 are replaced with steps 372 to 376. In FIG. 21, the same steps as those shown in FIG. 18 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 21, first, a reference value for the crank angle synchronous purge execution time TPG is set (step 370). As shown in the frame of step 340, the ECU 40 stores a map in which the reference value of the execution time TPG is defined in relation to “the number of purges + 1”. “Number of purges” is the number of executions of crank angle synchronous purge executed after generation of the cylinder discrimination signal. Therefore, “the number of purges + 1” is, for example, “1” at the timing when the first crank angle synchronization purge should be executed, “2” at the timing when the second crank angle synchronization purge should be executed, and the Nth crank angle synchronization. It becomes “N” at the timing when the purge should be executed. In this step 370, a reference value for the execution time TPG is set according to this map based on the number of purges described above.

  In this embodiment, the reference value of the execution time TPG described above is that the fuel required for the first explosion is supplied to all the cylinders by the group purge for the # 1, # 4 cylinders and the group purge for the # 2, # 3 cylinders. It is set on the assumption that For this reason, the map shown in the frame of step 370 is set so that the execution time TPG becomes 0 for the first four times. This map is set so that the execution time TPG for the fifth and subsequent crank angle synchronous purges is the time for purging an appropriate amount of fuel for one intake.

  When the processing in step 370 is completed, it is next determined in step 342 whether the initial signal generation time TCRNK is equal to or greater than the determination value KTCRNK. As a result, when the establishment of TCRNK ≧ KTCRNK is recognized, it can be estimated that the cranking speed is slow and the purge amount of the evaporated fuel by the group purge has not reached the predetermined amount. In this case, a correction time ATPG for compensating for the shortage of the group purge is calculated (step 372).

  As shown in the frame of step 372, the ECU 40 stores a map that defines the correction time ATPG in relation to “the number of purges + 1”. This map is set so that the correction time ATPG becomes a non-zero value only for the first four times. Insufficient fuel supply due to group purge affects the first to fourth intake strokes after cylinder discrimination. These deficiencies can be compensated only by the first to fourth crank angle synchronous purge. The non-zero correction time ATPG set in the above map is set to a value for compensating for the fuel shortage due to the group purge. For this reason, according to the process of step 372, the correction time ATPG for appropriately compensating for the shortage of fuel due to the group purge can be set for each crank angle synchronous purge.

  On the other hand, if the establishment of TCRNK ≧ KTCRNK is denied in step 342, it can be estimated that the cranking speed is sufficiently high and the fuel vapor amount is sufficiently purged by the group purge. That is, in this case, it can be determined that there is no shortage in the amount of evaporated fuel by the group purge, and that the correction time ATPG for compensating for the shortage is unnecessary. In this case, the process of step 372 is jumped. As a result, the correction time ATPG is maintained at the initial value 0.

  In the routine shown in FIG. 21, the crank angle synchronous purge execution time TPG is then added by adding the correction time ATPG set by the above-described process to the reference value of the execution time TPG set by the process of step 370. Is calculated (step 374).

  Next, the purge advance amount CRNKPG is set (step 376). As shown in the frame of step 376, the ECU 40 stores a map in which the purge advance amount CRNKPG is determined in relation to “the number of purges + 1”. Here, the purge advance amount CRNKPG is set according to the map. According to this map, the purge advance amount CRNKPG is zero from the first time to the fourth time. Accordingly, the crank angle synchronous purge from the first time to the fourth time is started at the same time when the first intake cylinder to the fourth intake cylinder reach the intake top dead center.

  Thereafter, similarly to the routine shown in FIG. 18 described above (see the fourth embodiment), the processing of steps 352 to 358 is performed, so that the crank angle synchronous purge is appropriately executed in each cylinder.

  As described above, according to the routines shown in FIGS. 20 and 21, according to the purge rule shown in FIG. 19, the group purge for the # 1, # 4 cylinders, the group purge for the # 2, # 3 cylinders, and the subsequent crank Angle synchronous purge can be realized. For this reason, according to the system of the present embodiment, it is possible to achieve excellent start-up response and good emission characteristics without using crank angle asynchronous purge.

  In the fifth embodiment described above, the group purge for the # 2 and # 3 cylinders is started simultaneously with the generation of the cylinder discrimination signal, but the start timing is not limited to this. That is, in the present embodiment, the crank angle sensor 46 generates a signal synchronized with the crank angle before the generation of the cylinder discrimination signal, as in the case of the fourth embodiment. For this reason, the group purge start timing for the # 2 and # 3 cylinders may be set before the cylinder discrimination signal is generated, as long as no fuel blow-through occurs from those cylinders.

It is a figure for demonstrating the structure of Embodiment 1 of this invention. It is a timing chart for demonstrating operation | movement of a comparative example. 3 is a timing chart for explaining the operation of the first embodiment of the present invention. It is a flowchart of the main routine performed in Embodiment 1 of the present invention. It is a flowchart of the 1st routine performed in step 104 shown in FIG. It is a flowchart of the 2nd routine performed in step 104 shown in FIG. It is a flowchart of the 1st routine performed in step 108 shown in FIG. It is a flowchart of the 2nd routine performed in step 108 shown in FIG. It is a timing chart for demonstrating operation | movement of Embodiment 2 of this invention. It is a flowchart of the main routine performed in Embodiment 2 of the present invention. It is a timing chart for demonstrating the inversion operation implement | achieved in Embodiment 3 of this invention. It is a flowchart of the main routine performed in Embodiment 3 of the present invention. It is a flowchart of the routine performed in order to implement | achieve crank angle synchronous purge in Embodiment 3 of this invention. FIG. 10 is a flowchart of a routine that is executed to determine a start cylinder for crank angle synchronous purge and to implement correction purge in Embodiment 3 of the present invention. It is a flowchart of the routine performed in order to open and close D-VSV in Embodiment 3 of this invention. It is a timing chart for demonstrating operation | movement of Embodiment 4 of this invention. FIG. 10 is a flowchart of a routine that is executed to realize group purge for # 1, # 4 cylinders in a fourth embodiment of the present invention. 14 is a flowchart of a routine that is executed in order to realize crank angle synchronous purge after cylinder discrimination in the fourth embodiment of the present invention. It is a timing chart for demonstrating operation | movement of Embodiment 5 of this invention. 16 is a flowchart of a routine that is executed in order to realize group purge for # 1, # 4 cylinders and group purge for # 2, # 3 cylinders in the fifth embodiment of the present invention. FIG. 10 is a flowchart of a routine that is executed to realize crank angle synchronous purge after cylinder discrimination in a fifth embodiment of the present invention.

Explanation of symbols

10 Internal combustion engine 16 Intake manifold 24 Purge passage 26 D-VSV
28 Canister 40 ECU (Electronic Control Unit)
46 Crank angle sensor
MV intake pipe pressure
THW Cooling water temperature
NE engine speed
CCRNK Crank angle counter
TST cranking time
KST1, KST3 # 1, # 4 cylinder asynchronous purge delay time
Asynchronous purge delay time for KST2, KST4 # 2, # 3 cylinders
KST3
KCCRNK Initial value of CCRNK (−7)
KCCRNK2 Second initial set value (0 or 12)

Claims (7)

An evaporative fuel processing apparatus for supplying evaporative fuel to an internal combustion engine having a plurality of pairs of cylinders operating in the same phase with a stroke difference of 360 ° CA,
A canister that stores evaporative fuel;
A purge passage communicating the canister to the intake port of each cylinder;
A purge control valve provided for each cylinder to control the conduction state between the intake port of each cylinder and the canister;
A first cylinder discrimination signal generating means for generating a first cylinder discrimination signal at a crank angle at which the specific cylinder reaches a specific state during operation of the internal combustion engine;
Second cylinder discrimination signal generating means for generating a second cylinder discrimination signal at a crank angle at which the cylinders constituting the specific cylinder and the cylinder pair reach the specific state;
The purge control valve of the first discrimination cylinder that performs the intake stroke immediately after the generation of the first cylinder discrimination signal and the purge control valve of the second discrimination cylinder that performs the intake stroke immediately after the generation of the second cylinder discrimination signal are simultaneously opened. Discriminating cylinder group purge means for realizing discriminating cylinder group purge,
The evaporative fuel processing apparatus is characterized in that the discriminating cylinder group purge is started when a first delay time has elapsed since the start of the internal combustion engine.   The discriminating cylinder group purge is finished after securing a desired purge time before the first intake stroke is completed after the first first cylinder discriminating signal or the first second cylinder discriminating signal is issued. The evaporative fuel processing apparatus according to claim 1, wherein the evaporative fuel processing apparatus is executed.   After starting the internal combustion engine, the purge control valves of the non-discriminating cylinders excluding the first discriminating cylinder and the second discriminating cylinder are opened by a method different from the discriminating cylinder group purge. The evaporative fuel processing apparatus according to claim 1, further comprising a non-discriminating cylinder purge unit that realizes a purge. The non-discriminating cylinder purge means includes non-discriminating cylinder group purge means for simultaneously opening all of the purge control valves of the non-discriminating cylinders to realize non-discriminating cylinder group purge,
The non-discrimination cylinder group purge is started earlier than the discrimination cylinder group purge, and a desired purge time is secured before either the first cylinder discrimination signal or the second cylinder discrimination signal is issued. 4. The evaporative fuel processing apparatus according to claim 3, wherein the evaporative fuel processing apparatus is executed so as to be terminated.   5. The evaporation according to claim 4, wherein the non-discriminating cylinder group purge is started when a second delay time shorter than the first delay time elapses from the start of the internal combustion engine. Fuel processor. A purge required time estimating means for estimating a purge required time required to supply a desired amount of evaporated fuel to the non-discriminating cylinder immediately after starting the internal combustion engine;
Comparing means for comparing the purge required time with the purgeable time,
The non-discriminating cylinder purge means includes
Normal control means for performing a purge in the non-discrimination cylinder prior to the discrimination cylinder group purge when the purge required time is equal to or less than the purgeable time;
Reversing control means for performing purging for the non-discriminating cylinders after the start of the discriminating cylinder group purge when the purge required time is longer than the purgeable time;
The evaporative fuel processing apparatus of Claim 3 characterized by the above-mentioned. During operation of the internal combustion engine, a crank angle signal is generated for each predetermined crank angle, and after starting the internal combustion engine, a predetermined crank angle is determined from a position where the specific cylinder or a cylinder constituting the specific cylinder and the cylinder pair reaches the specific state. A crank angle signal generating means for starting to generate the crank angle signal from the stage where the rotational position of the crankshaft reaches a position that is traced back;
The discriminating cylinder group purge means starts the discriminating cylinder group purge when the crank angle signal is generated,
4. The evaporative fuel processing apparatus according to claim 3, wherein the non-discriminating cylinder purge means executes the purging of the non-discriminating cylinder in synchronization with a crank angle after the discrimination cylinder group purge.

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