JP4375209B2 - Evaporative fuel processing equipment - Google Patents

Description

  The present invention relates to an evaporative fuel processing apparatus, and more particularly to an evaporative fuel processing apparatus for processing evaporative fuel generated in the vicinity of an internal combustion engine mounted on a vehicle without releasing it into the atmosphere.

  Conventionally, for example, Japanese Unexamined Patent Application Publication No. 2002-221664 discloses a configuration in which an evaporative fuel treatment device is mounted on a hybrid vehicle. The fuel vapor processing apparatus includes a canister that captures fuel vapor generated in the fuel tank. When intake negative pressure is introduced to the canister during the operation of the internal combustion engine, the evaporated fuel inside the canister is purged by the flow of air and introduced to the internal combustion engine. For this reason, when the internal combustion engine is operating stably, the evaporated fuel in the canister can be purged in a relatively short time.

  In the hybrid vehicle, the internal combustion engine is frequently stopped in accordance with the traveling state of the vehicle. Since the intake negative pressure is not generated while the internal combustion engine is stopped, the canister purge cannot proceed. For this reason, it is not always easy to obtain a sufficient purge capability in the evaporated fuel processing apparatus mounted on the hybrid vehicle.

  According to the configuration disclosed in the above publication, it is determined whether or not the canister purge needs to be advanced in addition to the running state of the vehicle. When the necessity is recognized, the internal combustion engine is put into an operating state regardless of the traveling state of the vehicle. According to such processing, a desired purge capability can be reliably ensured in the hybrid vehicle. For this reason, according to the conventional evaporative fuel processing apparatus described above, extremely good emission characteristics can be realized on the hybrid vehicle.

JP 2002-221064 A JP 2004-76673 A JP-A-4-194334 JP-A-8-135510 JP 11-294268 A

  However, the above-described conventional apparatus starts an internal combustion engine that can originally be maintained in a stopped state as needed for purging. For this reason, this apparatus has an advantage in that it is easy to deteriorate the fuel consumption of the internal combustion engine, although it is advantageous in ensuring the purge opportunity.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an evaporative fuel processing apparatus that can sufficiently ensure a purge opportunity without deteriorating the fuel consumption of an internal combustion engine. And

In order to achieve the above object, a first invention is a fuel vapor processing apparatus,
A canister that adsorbs the evaporated fuel generated in the fuel tank;
A purge passage communicating the canister with an intake passage of an internal combustion engine;
Temperature determination means for determining whether or not the catalyst disposed in the exhaust passage of the internal combustion engine has an activation temperature or higher;
Stop condition determination means for determining success or failure of the stop condition of the internal combustion engine;
An electric motor for applying rotational torque to the internal combustion engine;
A post-stop purge means for realizing post-stop purge by rotating the internal combustion engine with the electric motor while the purge passage is in a conducting state when the catalyst is at an activation temperature or higher and the stop condition is satisfied. and, with a,
The post-stop purge means includes a rotational speed control means for controlling the rotational torque generated by the electric motor so that the engine rotational speed gradually decreases after the stop condition is satisfied .

The second invention is the first invention, wherein
An electronically controlled throttle valve that changes the throttle opening in response to an externally supplied drive signal;
Concentration detecting means for detecting the concentration of purge gas flowing out of the canister;
Throttle control means for increasing the throttle opening at the time of purging after the stop as the concentration of the purge gas is higher,
It is characterized by providing.

The fifth invention is the first invention, wherein
Concentration detection means for detecting the concentration of purge gas flowing out from the canister,
The engine speed control means slows down the engine speed at the time of purging after the stop as the purge gas concentration increases.

According to a sixth invention, in any one of the first to fifth inventions,
A variable valve timing mechanism capable of varying a valve overlap period in which both the intake valve and the exhaust valve are opened; and
During execution of the purge after the stop, VVT control means for controlling the variable valve timing mechanism so that the valve overlap disappears,
It is characterized by providing.

  According to the first invention, the internal combustion engine is driven by the electric motor when the catalyst is at the activation temperature or higher and the stop condition of the internal combustion engine is satisfied. At this time, the internal combustion engine functions as a pump, and the evaporated fuel in the canister is sent to the catalyst. As a result, the evaporated fuel burns in the catalyst and is processed without deteriorating the emission characteristics. The post-stop purge is realized without starting the internal combustion engine, that is, without injecting fuel into the internal combustion engine. For this reason, according to this invention, the opportunity of a purge can be increased, without deteriorating the fuel consumption of an internal combustion engine.

  According to the second aspect of the invention, the higher the purge gas concentration is, the greater the throttle opening during purging after stopping. The greater the throttle opening, the greater the amount of air flowing through the intake passage, and the more easily the purge gas is diluted. For this reason, according to the present invention, the air-fuel ratio of the gas reaching the catalyst can always be kept appropriate regardless of the concentration of the purge gas, and the combustibility of the evaporated fuel in the catalyst can be maintained well.

  According to the third aspect of the invention, the higher the purge gas concentration, the higher the engine speed during purging after stopping. As the engine speed increases, the amount of air flowing through the intake passage increases, so that the purge gas is easily diluted. For this reason, according to the present invention, the air-fuel ratio of the gas reaching the catalyst can always be kept appropriate regardless of the concentration of the purge gas, and the combustibility of the evaporated fuel in the catalyst can be maintained well.

  According to the fourth aspect of the present invention, the engine speed can be gently reduced after the start of the purge after the stop. If the engine speed decreases gently, the shock caused by the engine stop can be reduced. Further, while the engine speed is gradually decreasing, the purge can be continued after stopping with the internal combustion engine as a pump. Therefore, according to the present invention, it is possible to ensure a high purge capability without deteriorating the fuel consumption of the internal combustion engine while sufficiently suppressing the shock felt by the vehicle occupant.

  According to the fifth aspect of the invention, the higher the purge gas concentration, the slower the speed of decrease of the engine speed after the start of purge after stopping. The slower the engine speed decreases, the more difficult it is to reduce the amount of intake air and the easier it is to dilute the gas that reaches the catalyst. Moreover, the slower the rate of decrease, the longer the purge execution period after stopping, and the easier the purge opportunity is. Therefore, according to the present invention, the air-fuel ratio of the gas that reaches the catalyst can always be kept appropriate regardless of the concentration of the purge gas, and the higher the purge gas concentration, the more the opportunity for purging is secured. Is possible.

  According to the sixth aspect of the invention, the valve overlap can be eliminated together with the start of the purge after the stop. When the valve overlap disappears, the backflow of gas from the exhaust passage to the intake passage is prevented, so that the occurrence of backfire can be prevented. For this reason, according to the present invention, it is possible to reliably prevent the occurrence of backfire during the execution of the purge after stopping.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
FIG. 1 is a diagram for explaining the configuration of the first embodiment of the present invention. The system of the present invention is premised on mounting in a vehicle, more specifically in a hybrid vehicle, and includes a fuel tank 10. A canister 14 communicates with the fuel tank 10 through a vapor passage 12. The canister 14 includes activated carbon therein, and can adsorb evaporated fuel flowing in from the fuel tank 10.

  An atmospheric passage 16 communicates with the canister 14. A CCV 18 is provided in the atmospheric passage 16. The CCV 18 is an electromagnetic valve for blocking the atmospheric passage 16. Further, a purge passage 22 communicates with the canister 14. The purge passage 22 includes a purge VSV 24 and communicates with an intake passage 26 of the internal combustion engine at an end portion thereof. The intake passage 26 includes a throttle valve 30 downstream of the air filter 28. The throttle valve 30 is an electronically controlled valve mechanism and can change the throttle opening degree TA in response to a drive signal supplied from the outside.

  The purge passage 22 described above communicates with the intake passage 26 downstream of the throttle valve 30. The intake passage 26 communicates with an intake port 32 of the internal combustion engine. The intake port 32 is assembled with a fuel injection valve 33 for injecting fuel therein. An exhaust passage 34 communicates with the internal combustion engine. A catalyst 36 for purifying exhaust gas is incorporated in the exhaust passage 34.

  The internal combustion engine further includes an intake valve 38 and an exhaust valve 40. Variable valve mechanisms 42 and 44 are connected to the intake valve 38 and the exhaust valve 40, respectively. According to the variable valve mechanisms 42 and 44, the valve opening timing of the intake valve 38 and the valve opening timing of the exhaust valve 40 can be appropriately changed.

  The system of this embodiment includes an ECU (Electronic Control Unit) 50. The ECU 50 is supplied with outputs from various sensors mounted on the internal combustion engine. The ECU 50 is connected to various actuators mounted on the internal combustion engine, such as the fuel injection valve 33 and the throttle valve 30. The ECU 50 can appropriately drive the actuators based on the sensor outputs.

  The system of this embodiment further includes a motor generator (MG) 60. The MG 60 can function as a driving wheel of a vehicle or an electric motor that gives a driving torque to the internal combustion engine, and also functions as a generator that receives a driving torque from the driving wheel of the internal combustion engine or the vehicle and performs a power generation operation. Can do.

[Basic operation of the first embodiment]
In the system according to the present embodiment, for example, at the time of refueling, the CCV 18 is opened to open the canister 14 to the atmosphere. When refueling is performed in this state, the gas present in the fuel tank 10, that is, the gas containing the evaporated fuel flows into the canister 14 through the vapor passage 12. At this time, the canister 14 adsorbs the evaporated fuel in the gas and releases only the air component not containing the fuel component from the atmospheric passage 16 to the atmosphere.

  The system according to the present embodiment adsorbs the evaporated fuel to the canister 14 by the same operation under a situation where a large amount of evaporated fuel is generated in the fuel tank 10 in addition to refueling. According to such a function, it is possible to effectively prevent the fuel vapor from flowing out to the atmosphere.

  The system of this embodiment performs control for purging the canister 14 during operation of the internal combustion engine, more specifically, during normal operation involving fuel injection by the fuel injection valve 33. Hereinafter, this control is referred to as “normal purge control”.

  During execution of the normal purge control, the CCV 18 is opened, and the purge VSV 24 is driven to open and close at an appropriate duty ratio. When the purge VSV 24 opens during normal operation of the internal combustion engine, intake negative pressure is introduced to the canister 14. As a result, air is sucked from the atmospheric passage 16, the canister 14 is purged by the air, and purge gas containing evaporated fuel flows into the intake passage 26.

  During normal operation of the internal combustion engine, known air-fuel ratio feedback control is executed so that the exhaust air-fuel ratio becomes the stoichiometric air-fuel ratio. If the purge gas is richer than the stoichiometric air-fuel ratio, the exhaust air-fuel ratio is biased toward the rich side. On the other hand, if the purge gas is lean, the exhaust air-fuel ratio also becomes a value biased lean. For this reason, it is possible to estimate the concentration of the purge gas by looking at the deviation of the exhaust air-fuel ratio.

  The ECU 50 learns the purge gas concentration FGPG based on the deviation of the exhaust air-fuel ratio while executing the air-fuel ratio feedback control during the normal operation. Based on the concentration FGPG, the fuel injection amount is corrected to increase or decrease so that the influence of the purge gas is offset. For this reason, according to the system of the present embodiment, it is possible to process the evaporated fuel adsorbed by the canister 14 without deteriorating the emission characteristics during normal operation of the internal combustion engine. The correction method using FGPG is not a main part of the present invention and is a publicly known matter, and therefore detailed description thereof is omitted here.

[Characteristic Operation in Embodiment 1]
The canister 14 cannot adsorb evaporated fuel beyond a certain capacity. Therefore, in order to prevent the vaporized fuel generated in the fuel tank 10 from being released into the atmosphere, the amount of fuel adsorbed on the canister 14 can be made as small as possible, that is, the canister 14 can be purged. It is desirable to ensure as much as possible.

  On the other hand, the normal purge control described above is for purging the canister during operation of the internal combustion engine. For this reason, when the operation of the internal combustion engine does not continue sufficiently, a large purge amount cannot be ensured by the normal purge control. In particular, in a hybrid vehicle, since the internal combustion engine is frequently stopped, it is difficult to ensure a sufficient purge amount by the normal purge control.

  By the way, in the system of this embodiment, the catalyst 36 is heated to a high temperature by exhaust heat during normal operation of the internal combustion engine. This temperature is maintained above the activation temperature for a certain period after the internal combustion engine is stopped. For this reason, for a while after the internal combustion engine is stopped, the catalyst 36 can burn the fuel.

  In the system of the present embodiment, the internal combustion engine can be rotated while stopping fuel injection by using the MG 60 as a power source. The internal combustion engine functions as a pump that sends out the gas on the intake side to the exhaust side during its rotation. For this reason, in the system of the present embodiment, after the stop of the internal combustion engine is commanded, that is, after the fuel injection to the internal combustion engine is stopped, the MG 60 is driven with the purge VSV 24 open for a while. Thus, the evaporated fuel in the canister 14 can be led to the catalyst 36 and burned.

  If the internal combustion engine is rotated using the MG 60 as a power source, it is not necessary to inject fuel unnecessarily to the internal combustion engine. For this reason, according to the purge method described above, after the stop command for the internal combustion engine is issued, the canister 14 can be purged without wasteful fuel injection. Therefore, in this embodiment, in order to ensure a purge opportunity, in addition to the normal purge control, the purge after the stop command described above is executed. Hereinafter, this purge is referred to as “purge after stop”.

[Specific Processing in Embodiment 1]
FIG. 2 is a flowchart of a routine executed by the ECU 50 in order to realize the purge after stop. In the routine shown in FIG. 2, it is first determined whether or not a stop condition for the internal combustion engine is satisfied (step 100). In a hybrid vehicle, even if the vehicle IG is on, for example, this condition is satisfied when the vehicle speed becomes zero.

  If it is determined in step 100 that the internal combustion engine stop condition is not satisfied, it can be determined that there is no need for purge after stop. In this case, after the stop air amount integrated value SGA is reset to 0 (step 102), the determination air amount TGA is set (step 104).

  The post-stop air amount integrated value SGA is an integrated value of the intake air amount after the stop condition of the internal combustion engine is satisfied, that is, an integrated value of the air amount supplied to the catalyst 36 after the fuel injection is stopped. Here, since the stop condition has not yet been established, the value SGA is set to zero.

  The temperature of the catalyst 36 decreases with time after the fuel injection is stopped. The temperature decreases earlier as the amount of air flowing through the catalyst 36 increases. The determination air amount TGA is an upper limit value of the air amount that allows the catalyst 36 to maintain the activation temperature after the fuel injection to the internal combustion engine is stopped. This upper limit value increases as the temperature of the catalyst 36 during operation of the internal combustion engine increases. Therefore, as shown in the frame of step 104, the ECU 50 stores a map that defines the determination air amount TGA in relation to the catalyst temperature.

  In step 104, specifically, first, the catalyst temperature is detected. Next, the determination air amount TGA corresponding to the detected catalyst temperature is read with reference to the above map. As a result, the determination air amount TGA is appropriately set to the upper limit value of the post-stop air amount at which the catalyst 36 can maintain the activation temperature.

  When the above processing is completed, normal purge control is then performed (step 106). According to the normal purge control, as described above, the canister 14 can be purged during the normal operation of the internal combustion engine without deteriorating the emission characteristics.

  If the internal combustion engine stop condition is satisfied, the determination in step 100 is affirmed. In this case, first, integration processing of the post-stop air amount integrated value SGA is executed (step 108).

  Next, it is determined whether the post-stop air amount integrated value SGA is greater than or equal to the determination air amount TGA (step 110). If it is determined that the SGA has reached the TGA, it can be determined that the catalyst 36 has already fallen below the activation temperature, that is, it is time to finish the purge after stopping. In this case, thereafter, the variable valve mechanisms 42 and 44 and the throttle valve 30 are returned to the starting state (step 112), and further, the purge VSV 24 and the MG 60 are turned off (steps 114 and 116). After stopping, the purge is completed.

  On the other hand, if it is determined in step 110 that the post-stop air amount integrated value SGA has not reached the determination air amount TGA, it can be determined that the catalyst 36 still maintains the activation temperature. In this case, it is next determined whether or not the normal purge time TPGON is equal to or greater than the determination value KPG100 (step 118).

  The normal purge time TPGON is an execution integration time of normal purge control that is counted for each trip, that is, for each period after the IG is turned on. On the other hand, the determination value KPG100 is a standard purge time required to purge the evaporated fuel adsorbed by the canister 14 to some extent. Therefore, if it is recognized in step 118 that TPGON ≧ KPG100 is established, it can be determined that the canister 14 is properly purged by the normal purge control, and that it is not necessary to perform the purge after stopping. In this case, the processes of steps 112 to 116 are subsequently executed.

  On the other hand, if it is determined in step 118 that TPGON ≧ KPG100 is not established, it can be determined that the purge by the normal purge control is insufficient and that it is necessary to perform the purge after the stop. In this case, throttle closing control is first executed (step 120).

  As shown in the frame of step 120, the ECU 50 stores a map that defines the throttle opening degree TA in relation to the engine speed NE. In step 120, specifically, the throttle opening degree TA corresponding to the current engine speed NE is read according to this map, and the throttle valve 30 is controlled so that the TA is realized.

  During the execution of the purge after the stop, the internal combustion engine is in an operating state by being driven by the MG 60. At this time, if the throttle opening TA is too large, intake negative pressure is not generated and the canister 14 cannot be purged. On the other hand, if the throttle opening TA is too small, excessive intake negative pressure is generated, so-called oil rise (a phenomenon in which oil flows from the periphery of the piston into the combustion chamber) and oil fall (oil from the circumference of the valve stem to the combustion chamber). Phenomenon).

  These phenomena can be prevented by controlling the intake negative pressure generated during the execution of the purge after stopping to an appropriate value. Then, the intake negative pressure at the time of purging after stopping can be set to an appropriate value by setting the throttle opening TA to an appropriate value according to the engine speed NE. The map shown in the frame of step 120 is determined by conformance or the like so as to satisfy the above requirement. For this reason, according to the system of the present embodiment, it is possible to generate an appropriate intake negative pressure that does not cause an oil increase or an oil decrease after the start of the purge after the stop.

  When the above process is completed, the purge VSV 24 is thereafter opened (ON state) (step 122), and the drive control of the MG 60 is started (step 124). When these processes are executed, an appropriate intake negative pressure is introduced to the canister 14 and the purge of the canister 14 is started.

  FIG. 3 is a timing chart for explaining the post-stop purge operation realized by the above processing. Specifically, FIG. 3A is a waveform showing a purge execution state. FIG. 3B is a waveform showing a change in the engine speed NE. In these figures, the solid line shows the waveform when purge after stop is executed, and the broken line shows the waveform when purge after stop is not executed.

  As shown in FIG. 3, when the purge is not executed after the stop (see the broken line), after the stop command is issued to the internal combustion engine, the engine speed NE is quickly reduced to 0, and the purge is quickly stopped. Is done. On the other hand, in the system of the present embodiment, after the stop command is issued to the internal combustion engine, the internal combustion engine is driven by the MG 60 until the post-stop air amount integrated value SGA reaches the determination air amount TGA. As a result, post-stop purge without fuel injection is realized. For this reason, according to the system of the present embodiment, the purge opportunity can be increased without substantially deteriorating the fuel consumption of the internal combustion engine.

  By the way, in the first embodiment described above, when TPGON ≧ KPG100 is not satisfied, that is, when it is determined that the execution time of the normal purge control is insufficient, the purge is always started after stopping. However, even if the condition is not satisfied, as long as the elapsed time after turning on the IG is insufficient, the start of the purge after the stop may be suspended regardless of the failure.

  In a hybrid vehicle, the stop condition for the internal combustion engine is frequently satisfied, so the stop condition may be satisfied immediately after the IG is turned on. When the vehicle is traveling on a congested road, the stop condition of the internal combustion engine is repeatedly established thereafter, and a situation in which sufficient purge cannot be obtained only by the normal purge control occurs. On the other hand, when the vehicle can travel smoothly thereafter, the canister 14 can be purged only by the normal purge control, and it is not always necessary to perform the purge after the stop.

  As described above, if the execution of purge after stopping is suspended while the elapsed time from IG ON is insufficient, the purge execution scene after stopping is appropriate for normal purge control alone, such as when traveling on a congested road. It can be limited to scenes where purging cannot be expected. For this reason, if the post-stop purge execution condition is (i) TPGON ≧ KPG100 is not satisfied, and (ii) a sufficient time has elapsed after the IG is turned on, the post-stop purge is executed more appropriately. You can limit and save waste.

  Moreover, in Embodiment 1 mentioned above, although it is premised on mounting an evaporative fuel processing apparatus in a hybrid vehicle, this invention is not limited to this. That is, the fuel vapor processing apparatus according to the present invention may be mounted on an eco-run vehicle that performs idling stop.

  In the eco-run vehicle, the stop of the internal combustion engine may be instructed while the IG is turned on, as in the hybrid vehicle. Further, the eco-run vehicle is equipped with a starter motor that gives a driving torque to the internal combustion engine. For this reason, if the MG 60 in the first embodiment is replaced with a starter motor, the above-described purge after stop can be realized even in an eco-run vehicle, and the same effect as in the first embodiment can be obtained.

  Furthermore, the fuel vapor processing apparatus according to the present invention is not limited to a hybrid vehicle or an eco-run vehicle, and may be mounted on a normal vehicle. As in the case of the eco-run vehicle, if the starter motor is replaced with the MG 60, the above-described purge after stop can be realized even in the normal vehicle. And according to such a modification, the effect of increasing the opportunity of purging can be acquired, without deteriorating a fuel consumption in a normal vehicle.

  In the first embodiment described above, whether the catalyst 36 is at or above the activation temperature is determined based on the post-stop air amount integrated value SGA, but the determination method is limited to this. is not. That is, whether or not the catalyst 36 is equal to or higher than the activation temperature may be determined based on an actual measurement value of the temperature. The several types of modifications described above can be similarly performed in other embodiments described below.

  In the first embodiment described above, the ECU 50 executes the process of step 110, so that the “temperature determination means” in the first invention executes the process of step 100, and thus the first invention. The “stop condition determining means” in FIG. 6 implements the “post-stop purge means” in the first aspect of the present invention by executing the processing of steps 122 and 124 described above.

Embodiment 2. FIG.
[Features of Embodiment 2]
Next, a second embodiment of the present invention will be described with reference to FIG. The system of the present embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 4 described later in the system shown in FIG.

  The system of the first embodiment described above determines the throttle opening degree TA so that the intake negative pressure becomes an appropriate value based on the engine speed NE at the time of purge after stop. That is, in the first embodiment, the throttle opening degree TA is always determined based on the engine speed NE regardless of the concentration of the purge gas flowing out from the canister 14.

  During the execution of the purge after the stop, the air-fuel mixture of the air flowing through the throttle valve 30 and the purge gas flowing out of the canister 14 flows into the catalyst 36. At this time, if the gas flowing into the catalyst 36 is excessively rich, even if the temperature of the catalyst 36 is sufficiently high, incomplete combustion of the fuel may occur due to insufficient oxygen.

  For this reason, when the concentration of the purge gas is high, in order to dilute the purge gas, it is desired to increase the intake air amount, that is, to increase the throttle opening TA. In order to satisfy such a requirement, the system of the present embodiment reflects the vapor concentration in the purge gas in the throttle opening TA when performing the purge after stopping.

[Specific Processing in Second Embodiment]
FIG. 4 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. The routine shown in FIG. 4 is the same as the flowchart shown in FIG. 2 except that steps 130 and 132 are inserted after step 120. In FIG. 4, the same steps as those shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  That is, in the routine shown in FIG. 4, after the throttle opening degree TA corresponding to NE is set in step 120, it is determined whether or not the engine speed NE is greater than or equal to the determined speed KNE (step 130). Immediately after the purge is started after the stop, the engine speed NE is still maintained at a high value. Under such circumstances, a large amount of intake air GA is ensured regardless of the throttle opening TA.

  If the intake air amount GA is large, the purge gas reaches the catalyst 36 in a sufficiently diluted state during execution of the purge after stopping. For this reason, under such a situation, the purge after stopping can be executed without considering the concentration of the purge gas. For the above reasons, if it is recognized in step 130 that NE ≧ KNE is established, then the processing of steps 122 and 124 is executed without confirming the purge gas concentration.

  On the other hand, if it is determined in step 130 that NE ≧ KNE is not established, that is, if it is determined that the engine speed NE is sufficiently reduced, the throttle opening degree TA is set based on the vapor concentration. Processing is performed. As shown in the frame of step 132, the ECU 50 stores a map that defines the throttle opening TA in relation to the vapor concentration in the purge gas. Further, as described above, the ECU 50 learns the purge gas concentration FGPG during execution of the normal purge control.

  In step 132, specifically, referring to the map, the throttle valve 30 is read so that the throttle opening degree TA corresponding to the learning value of the purge gas concentration FGPG is read and the read TA is realized. The process which controls is performed. When these processes are completed, the processes of steps 122 and 124 are subsequently executed to realize purge after stopping.

  According to the series of processes described above, after the NE falls below the KNE, the throttle opening TA can be increased as the purge gas concentration increases. Therefore, according to the system of this embodiment, even when the concentration of the purge gas is extremely high, it is possible to effectively prevent the excessively rich gas from being supplied to the catalyst 36 during the execution of the purge after the stop. Can do.

  In the second embodiment described above, the ECU 50 learns the purge gas concentration FGPG, so that the “concentration detection means” in the second invention executes the process of step 132, thereby executing the process in the second invention. “Throttle control means” is realized.

Embodiment 3 FIG.
[Features of Embodiment 3]
Next, a third embodiment of the present invention will be described with reference to FIG. The system of the present embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 5 described later in the system shown in FIG.

  In the above-described second embodiment, when the purge gas concentration is high, the throttle opening TA is increased to increase the intake air amount GA at the time of purging after stopping in order to dilute the purge gas. Incidentally, the intake air amount GA can be increased not only by increasing the throttle opening degree TA but also by increasing the engine speed NE. Therefore, in the present embodiment, the higher the purge gas concentration, the higher the engine speed NE during purging after stopping.

[Specific Processing in Embodiment 3]
FIG. 5 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. The routine shown in FIG. 5 is similar to the routine shown in FIG. 4 except that steps 120 and 130 are eliminated and that step 140 is inserted between steps 122 and 124. Hereinafter, in FIG. 5, the description of the same steps as the routine shown in FIG. 4 is omitted or simplified.

  That is, in the routine shown in FIG. 5, when it is determined in step 118 that the normal purge time TPGON has not reached the determination value KPG100, the processing in step 132, that is, the throttle opening degree TA is immediately adjusted according to the vapor concentration. The control to make the opening degree is executed.

  Further, in this routine, after the process of step 122, the target engine speed NET is set based on the vapor concentration (purge gas concentration FGPG) (step 140). In step 124, the state of MG 60 is controlled so that engine speed NE matches target engine speed NET.

  The ECU 50 stores a map that defines the target engine speed NET in relation to the vapor concentration. As shown in the frame of step 140, this map is set so that the higher the vapor concentration, the higher the NET value. For this reason, according to the series of processes described above, during the execution of the post-stop purge, the higher the vapor concentration, the larger the throttle opening TA and the higher the engine speed NE.

  The intake air amount GA generated during the execution of the purge after the stop increases as the engine speed NE increases. For this reason, according to the system of the present embodiment, a high-concentration purge gas can be diluted with a higher capacity than in the case of the third embodiment. For this reason, according to the system of this embodiment, even when the purge gas has a very high concentration, it is possible to reliably prevent incomplete combustion of the fuel during the execution of the purge after stopping.

  In the third embodiment described above, the ECU 50 learns the purge gas concentration FGPG, so that the “concentration detection means” in the third invention executes the processing of step 140 described above, thereby the third invention. The “rotational speed control means” in FIG.

Embodiment 4 FIG.
[Features of Embodiment 4]
Next, a fourth embodiment of the present invention will be described with reference to FIG. 6 and FIG. The system of the present embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 6 described later in the system shown in FIG.

  The systems of the first to third embodiments described above drive the MG 60 so that a constant low-speed engine speed is maintained after the internal combustion engine stop condition is satisfied. In this case, immediately after the stop condition is satisfied, the engine speed NE rapidly decreases. In order to reduce the shock felt by the vehicle occupant, the smaller the change in the engine speed NE that occurs at this point, the better.

  Therefore, in the system of the present embodiment, after the stop condition of the internal combustion engine is satisfied, the engine speed NE is gradually decreased, and the purge after stop is realized by using the decrease period of NE. According to such a method, the canister 14 can be purged by purging after stopping while sufficiently suppressing the shock felt by the passenger.

[Specific Processing in Embodiment 4]
FIG. 6 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. The routine shown in FIG. 6 is substantially the same as the routine shown in FIG. 5 except that step 140 is replaced with steps 150 to 154. Hereinafter, in FIG. 6, the description of the same steps as the routine shown in FIG. 5 is omitted or simplified.

  That is, in the routine shown in FIG. 6, after the throttle opening degree TA is controlled by the process of step 132, it is determined whether or not the engine speed NE is equal to or higher than the determined speed KNE100 (step 132). As described above, when the stop condition of the internal combustion engine is satisfied, the system of the present embodiment implements the post-stop purge while gradually reducing the engine speed NE. The above-described determination rotational speed KNE100 is the lowest engine rotational speed at which purging should be continued after the stop. For this reason, when it is recognized that NE ≧ KNE100 is not established, it is determined that the engine speed NE has sufficiently decreased, and that it is time to finish the purge after the stop. In this case, the processes of steps 112 to 116 are subsequently executed.

  On the other hand, if it is determined in step 150 that the NE is equal to or higher than KNE100, processing for realizing post-stop purge is executed. Here, first, a decrease width ΔNE of the engine speed NE is set based on the vapor concentration (purge gas concentration FGPG) (step 152). Next, the target engine speed NET = NE−ΔNE is calculated by subtracting the above ΔNE from the current engine speed NE.

  As shown in the frame of step 152, the ECU 50 stores a map in which ΔNE is determined in relation to the vapor concentration, and determines ΔNE according to the map. According to this map, as the vapor concentration is higher, the decrease width ΔNE is made smaller. Therefore, the target rotational speed NET tends to gradually decrease as the vapor concentration increases.

  After the target rotational speed NET is set, the post-stop purge process is executed so that the engine rotational speed NE matches the target rotational speed NET (steps 122 and 124).

  FIG. 7 is a timing chart for explaining the post-stop purge operation realized by the above processing. Specifically, FIG. 7A is a waveform showing the purge execution state. FIG. 7B is a waveform showing a change in the engine speed NE. In these figures, the solid line shows the waveform when purge after stop is executed, and the broken line shows the waveform when purge after stop is not executed.

  As shown in FIG. 7, according to the system of the present embodiment, the engine speed NE can be gradually reduced after the stop condition for the internal combustion engine is established. For this reason, according to the system of the present embodiment, the internal combustion engine can be brought into a stopped state without causing a large shock after the stop condition of the internal combustion engine is established.

  In the system of the present embodiment, the rate of decrease in the engine speed NE is made slower as the vapor concentration is higher. As a result, in this system, the higher the vapor concentration, the longer the purge stop period after the stop condition of the internal combustion engine is established. For this reason, according to the system of the present embodiment, the evaporated fuel in the canister 14 can be efficiently and efficiently purged by the purge after stoppage.

  In the fourth embodiment described above, the “rotational speed control means” in the fourth or fifth aspect of the present invention is realized by the ECU 50 executing the processing of steps 152 and 154. Here, the “concentration detection means” in the fifth aspect of the present invention is realized by the ECU 50 learning the purge gas concentration FGPG.

Embodiment 5 FIG.
[Features of Embodiment 5]
Next, a fifth embodiment of the present invention will be described with reference to FIG. The system of the present embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 8 described later in the system shown in FIG.

  As in the case of the first embodiment, the system of the present embodiment includes variable valve mechanisms 42 and 44. During operation of the internal combustion engine, the variable valve mechanisms 42 and 44 are usually controlled so that a valve overlap period occurs. For this reason, when the purge is started after stopping while the variable valve mechanisms 42 and 44 are maintained, the purge gas is pumped at the valve timing at which the valve overlap occurs.

  According to the valve timing at which the valve overlap occurs, a phenomenon occurs in which the high temperature gas in the exhaust passage 34 flows backward to the intake passage 32 every time the exhaust valve 40 and the intake valve 38 are both opened. If purge gas is introduced into the intake passage 32 as purge is performed after stopping, backfire may occur due to the backflow of the high-temperature gas. Such backfire causes the temperature of the intake system to rise, and also prevents the complete combustion of fuel in the catalyst 36. Therefore, in the system of the present embodiment, the state of the variable valve mechanisms 42 and 44 is changed so that the valve overlap disappears with the start of the purge after the stop.

[Specific Processing in Embodiment 5]
FIG. 8 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. The routine shown in FIG. 8 is the same as the routine shown in FIG. 2 except that step 160 is inserted after step 120. In FIG. 8, the same steps as those shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  According to the routine shown in FIG. 8, when it is determined that purge after stopping is performed, steps 122 and 124 are executed after execution of the VVT retardation control (step 160). The VVT retardation control is a control for moving the variable valve mechanisms 42 and 44 so that the valve overlap disappears. According to the above procedure, it is possible to reliably prevent backfire from occurring during the execution of purge after stopping. For this reason, according to the system of the present embodiment, the proper post-stop purge can be stably advanced without causing any inconveniences such as deterioration of emission and temperature rise of the intake system.

  In the fifth embodiment described above, the “VVT control means” according to the sixth aspect of the present invention is realized by the ECU 50 executing the process of step 160.

It is a figure for demonstrating the structure of Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. 3 is a timing chart for explaining the operation of the first embodiment of the present invention. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention. It is a flowchart of the routine performed in Embodiment 4 of this invention. It is a timing chart for demonstrating operation | movement of Embodiment 4 of this invention. It is a flowchart of the routine performed in Embodiment 5 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel tank 14 Canister 22 Purge passage 26 Intake passage 30 Throttle valve 42,44 Variable valve mechanism 34 Exhaust passage 36 Catalyst 50 ECU (Electronic Control Unit)
60 Motor generator (MG)

Claims (4)

A canister that adsorbs the evaporated fuel generated in the fuel tank;
A purge passage communicating the canister with an intake passage of an internal combustion engine;
Temperature determination means for determining whether or not the catalyst disposed in the exhaust passage of the internal combustion engine has an activation temperature or higher;
Stop condition determination means for determining success or failure of the stop condition of the internal combustion engine;
An electric motor for applying rotational torque to the internal combustion engine;
A post-stop purge means for realizing post-stop purge by rotating the internal combustion engine with the electric motor while the purge passage is in a conducting state when the catalyst is at an activation temperature or higher and the stop condition is satisfied. and, with a,
The post-stop purge means includes a rotational speed control means for controlling a rotational torque generated by the electric motor so that the engine rotational speed gradually decreases after the stop condition is satisfied. . An electronically controlled throttle valve that changes the throttle opening in response to an externally supplied drive signal;
Concentration detecting means for detecting the concentration of purge gas flowing out of the canister;
Throttle control means for increasing the throttle opening at the time of purging after the stop as the concentration of the purge gas is higher,
The evaporative fuel processing apparatus according to claim 1, further comprising: Concentration detection means for detecting the concentration of purge gas flowing out from the canister,
It said speed control means, the higher the concentration of the purge gas, fuel vapor treatment system according to claim 1, wherein the slow rate of decrease engine speed during the stop after purging. A variable valve timing mechanism capable of varying a valve overlap period in which both the intake valve and the exhaust valve are opened; and
During execution of the purge after the stop, VVT control means for controlling the variable valve timing mechanism so that the valve overlap disappears,
The evaporative fuel processing apparatus of any one of Claims 1 thru | or 3 characterized by the above-mentioned.

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