JP2007218178A - Hydrocarbon discharge reduction device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrocarbon discharge reduction device of an internal combustion engine capable of effectively reducing a discharge or emission amount of hydrocarbon to the outside. <P>SOLUTION: The internal combustion engine (10) has a hydrocarbon adsorption execution means for passing air containing hydrocarbon remaining in an air intake system through a hydrocarbon adsorption material (33) with use of a pump means (45) during engine stop to adsorb the hydrocarbon with the hydrocarbon adsorption material (33). An air circulation path forming means is provided to form an air circulation path (51) for circulating air from a downstream side of the hydrocarbon adsorption material in the upstream side air intake system during execution of the hydrocarbon adsorption execution means. Even when the hydrocarbon adsorption execution means is executed and air containing hydrocarbon remaining in the air intake system is passed through the hydrocarbon adsorption material by the pump means, the air is circulated through the air circulation path formed by the air circulation path forming means and the hydrocarbon is inhibited from being discharged to the outside. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hydrocarbon emission reduction device for an internal combustion engine that reduces the emission of hydrocarbons (hereinafter also referred to as “HC”) from the internal combustion engine.

  In general, in recent automobiles, in order to reduce the amount of HC emitted, the amount of unburned HC is reduced by improving the combustion of the engine, and a catalyst such as a three-way catalyst is installed in the exhaust system to discharge HC from the engine. To purify.

  By the way, after the engine is stopped, a part of the fuel injected during the previous operation remains in the intake passage of the surge tank or the like due to blow-back or the like, and when the engine is stopped, the fuel leaks little by little from the fuel injector. (Hereinafter referred to as oil-tight leak) may diffuse into the intake passage. There is also known an internal combustion engine including a hydrocarbon adsorbent that adsorbs hydrocarbons remaining in the intake system in order to prevent the fuel (HC) diffused in the intake passage from being released into the atmosphere as it is. Yes.

  On the other hand, the fuel (HC) diffused into the intake passage and stopped by the hydrocarbon adsorbent after the engine is stopped is sucked into the cylinder at the next engine start. However, immediately after the start of cranking, fuel injection from the fuel injector is not started until the cylinder discrimination is completed, and combustion does not occur in the cylinder. Therefore, the HC sucked into the cylinder does not burn into the exhaust pipe. Discharged. In addition, at the time of cold start, since the exhaust system catalyst is in an inactive state, HC in the exhaust cannot be sufficiently purified. As a result, the HC adsorbed on the hydrocarbon adsorbent may be discharged into the atmosphere as it is.

  Therefore, conventionally, in order to eliminate such inconvenience, an HC adsorbent is provided between the throttle valve and the engine body of the internal combustion engine or in the intake passage on the upstream side of the throttle valve, and remains in the intake passage by this adsorbent. Various techniques for adsorbing HC have been proposed.

  As one example, in Patent Document 1, an HC adsorbent is installed upstream of a throttle valve, for example, in an air cleaner, and air is injected by a pump in the vicinity of an intake port every predetermined period while the internal combustion engine is stopped. Thus, a technique for adsorbing HC remaining in the intake passage to the HC adsorbent is disclosed.

  Further, in Patent Document 2, a canister for adsorbing fuel evaporative gas generated in a fuel tank is used as an HC adsorbent, and the engine is connected through an air suction passage connected to an intake passage downstream of a throttle valve. By performing an air suction operation with a suction pump while the operation is stopped, hydrocarbons floating in the vicinity of the intake port are sucked through the air suction passage, thereby adsorbing hydrocarbons floating in the vicinity of the intake port to the HC adsorbent of the canister Techniques for making them disclosed are disclosed.

JP 2005-30367 A JP 2005-30368 A

  By the way, although the techniques disclosed in Patent Document 1 and Patent Document 2 are different in positive pressure or negative pressure, both use a pump so that air containing floating hydrocarbons passes through the HC adsorbent. Therefore, hydrocarbons are adsorbed on the HC adsorbent.

  However, in the techniques disclosed in Patent Document 1 and Patent Document 2, air containing floating hydrocarbons is allowed to pass through the HC adsorbent using pressure or suction force by a pump, and then externally passed through a filter. To be discharged. As a result, particularly when the amount of floating hydrocarbons is large, the hydrocarbons may pass through these filters and be released to the outside.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a hydrocarbon emission reduction device for an internal combustion engine that can effectively reduce emission or emission of hydrocarbons to the outside. It is to be.

  An apparatus for reducing hydrocarbon emissions of an internal combustion engine according to an embodiment of the present invention that achieves the above object is provided with a hydrocarbon adsorbent using pumping means for supplying air containing hydrocarbons remaining in an intake system while the engine is stopped. In an internal combustion engine having a hydrocarbon adsorption execution means for allowing the hydrocarbon adsorbent to pass through and adsorbing hydrocarbons to the hydrocarbon adsorbent, the intake system from the downstream side to the upstream side of the hydrocarbon adsorbent during execution of the hydrocarbon adsorption execution means An air circulation path forming means for forming an air circulation path for circulating air therein is provided.

  According to the above aspect, even when the hydrocarbon adsorption executing means is executed while the engine is stopped, and the air containing hydrocarbons remaining in the intake system is passed through the hydrocarbon adsorbent by the pump means, this hydrocarbon adsorbent The air that has passed through circulates through the air circulation path formed by the air circulation path forming means. Accordingly, since air containing floating hydrocarbons is not discharged to the outside, the release of hydrocarbons to the outside is suppressed.

  Here, the hydrocarbon adsorption execution means includes an air suction passage communicated downstream of the throttle valve in the intake passage, a hydrocarbon adsorbent provided in the air suction passage, and a suction pump for performing an air suction operation. The air circulation path forming means preferably includes a three-way switching valve provided downstream of the suction pump, and an air circulation passage for communicating the three-way switching valve and the intake passage.

  According to this aspect, the three-way switching valve provided downstream of the suction pump is switched during the air suction operation by the suction pump and communicates with the intake passage via the air circulation passage. Therefore, since the air circulation path is formed simply by switching the three-way switching valve, the configuration can be simplified.

  Further, the hydrocarbon adsorption execution means uses a canister in the fuel evaporative emission control device of the fuel tank as a hydrocarbon adsorbent, and further, one end communicates with the intake port downstream from the throttle valve. The bypass passage may be provided with another pump means capable of forward / reverse rotation and another hydrocarbon adsorbent interposed.

  According to this embodiment, another pump means and another hydrocarbon adsorbent that are capable of forward and reverse rotation are interposed in a bypass passage having one end downstream of the throttle valve and the other end communicated with the intake port. Accordingly, by operating another pump means in the forward or reverse direction, it is possible to adsorb hydrocarbons to another hydrocarbon adsorbent or to send air to the intake port to improve the engine performance.

  In addition, for example, by operating another pump means in the forward rotation direction at the time of fuel cut during engine operation, fuel adhering to the intake port wall surface, so-called port wet, is adsorbed to another hydrocarbon adsorbent and exhausted. It is possible to prevent unburned hydrocarbons from being wasted in the system. Also, in hybrid vehicles, etc., the hydrocarbon present in the intake port is adsorbed by operating another pump means in the forward direction from when the ignition switch is turned on until the engine is actually started. Can be made.

  Further, the another pump means is rotated forward under a predetermined condition while the engine is stopped, and air containing hydrocarbons remaining in the intake port through the bypass passage is passed through another hydrocarbon adsorbent so as to be hydrocarbon. There may be provided another hydrocarbon adsorption execution means for adsorbing the catalyst to another hydrocarbon adsorbent.

  According to this embodiment, even when the amount of fuel evaporative gas in the fuel tank is large and the amount of already adsorbed in the canister is large, another hydrocarbon adsorption execution means is executed so that one end is in the downstream of the throttle valve and the other end is inhaled. By operating another pump means provided in the bypass passage connected to the port in the forward rotation direction, the hydrocarbon can be adsorbed by another hydrocarbon adsorbent, so that the hydrocarbon is released to the outside. Is reliably suppressed.

  The another pump unit may be provided with a performance improving unit that reverses the pump unit under a predetermined condition during operation of the engine and sends a predetermined amount of air through the bypass passage to the intake port.

  According to this aspect, by executing the performance improving means and operating the other pump means in the reverse direction under a predetermined condition during operation of the engine, a predetermined amount of air can be sent to the intake port. It is possible to improve the performance of the engine by preventing the pressure reduction of the intake port.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings. The present embodiment embodies a hydrocarbon emission reduction device for a four-cylinder gasoline injection engine mounted on a vehicle, and FIG. 1 is a configuration diagram showing an outline of the engine control system.

  As shown in FIG. 1, in the engine 10, an air cleaner 12 is provided at the most upstream portion of the intake pipe 11, and an air flow meter 13 for detecting the intake air amount is provided downstream thereof. The air flow meter 13 incorporates an intake air temperature sensor for detecting the intake air temperature. A throttle valve 14 whose opening degree is adjusted by a throttle actuator such as a DC motor is provided on the downstream side of the air flow meter 13. A surge tank 15 is provided downstream of the throttle valve 14, and an intake manifold 16 that introduces air into each cylinder of the engine 10 is communicated with the surge tank 15. Fuel injectors 17 for injecting fuel are attached in the vicinity of intake ports (not shown) for each cylinder of the intake manifold 16. The intake pipe 11, the surge tank 15, and the intake manifold 16 constitute an intake passage.

  Further, the surge tank 15 of the present embodiment is provided with a first HC adsorbent 18 as a hydrocarbon adsorbent at the bottom as a first floating HC treatment system, and is placed in the intake passage while the engine is stopped. Residual HC is adsorbed by the first HC adsorbent 18. In the present embodiment, a recess is formed in the bottom of the surge tank 15, and most of the first HC adsorbent 18 is accommodated in the recess, so that the first HC adsorbent 18 flows the surge tank 15. The road cross-sectional area is not reduced. Further, a purge air introduction pipe (not shown) for introducing purge air into the first HC adsorbent 18 is connected between the upstream side of the throttle valve 14 of the intake pipe 11 and the recess of the surge tank 15. In the middle of the purge air introduction pipe, for example, an open / close valve (not shown) constituted by an electromagnetic valve is provided. When this valve is closed, the introduction of purge air to the first HC adsorbent 18 is stopped, and the state in which the HC is adsorbed to the first HC adsorbent 18 and the state in which the release is completed is maintained. Is done. On the other hand, when the valve is opened, purge air is introduced into the first HC adsorbent 18, and the purge air flows into the surge tank 15 through a number of gaps in the first HC adsorbent 18. Then, HC is released from the first HC adsorbent 18 into the intake air.

  The exhaust pipe 21 is provided with a catalyst 22 such as a three-way catalyst for purifying CO, HC, NOx and the like in the exhaust gas, and the upstream side of the catalyst 22 detects the exhaust gas as a detection target, or the air-fuel ratio of the air-fuel mixture or An air-fuel ratio sensor 23 (linear air-fuel ratio sensor, oxygen sensor, etc.) for detecting rich / lean is provided.

  Further, the engine 10 is provided with a fuel evaporative emission control device for suppressing the evaporative gas (evaporative gas) generated in the fuel tank 31 from being discharged to the outside. That is, one end of an evaporation gas conduit 32 is connected to the fuel tank 31, and a canister 33 is connected to the other end of the evaporation gas conduit 32. The canister 33 stores a large number of adsorbents made of activated carbon, for example, for adsorbing fuel evaporative gas generated in the fuel tank 31. The canister 33 can communicate with the atmosphere side through a path including the canister conduit 37, the electromagnetic switching valve 41, the filter 49, and the like, and fresh air is introduced into the canister 33 through the path. The canister 33 is connected to the intake manifold 16 through a purge pipe 34, and an electromagnetically driven normally closed purge control valve 35 is provided in the middle of the purge pipe 34. Therefore, when the purge control valve 35 is opened, an intake negative pressure acts on the purge pipe 34. At that time, fresh air is introduced into the canister 33 through the canister conduit 37 and the like, so that the adsorbent in the canister 33 is introduced. The adsorbed fuel is released from the intake manifold 16 and discharged to the intake manifold 16. The amount of gas discharged to the intake manifold 16 (purge gas amount) is duty-controlled by a purge control valve 35.

  The canister conduit 37 connected to the canister 33 performs a leak check (leakage diagnosis) on the fuel evaporative gas flow path from the fuel tank 31 to the purge control valve 35 via the canister 33. The leak check module 40 is connected. The leak check module 40 includes an atmospheric communication passage 42 communicated with the canister conduit 37 via an electromagnetic switching valve 41, a negative pressure introduction passage 43, a check valve 44 provided in the negative pressure introduction passage 43, and a first check valve 44. 1, a reference orifice 47 provided in the middle of a bypass passage 46 that bypasses the electromagnetic switching valve 41 and communicates with the canister conduit 37 and the negative pressure introduction passage 43, and a bypass passage 46 downstream of the reference orifice 47. The pressure sensor 48 is provided. A filter 49 is provided at the outlet of the atmosphere communication passage 42 outside the leak check module 40, and an electromagnetically driven three-way switching valve 50 is provided upstream of the filter 49. It is possible to communicate with the downstream side of the throttle valve 14 in the intake pipe 11 via the three-way switching valve 50 and the intake communication passage 51. The electromagnetic switching valve 41 is held in a state where it communicates between a and b in FIG. 1 when not energized, and is set to shift to a state where it communicates between a and c in FIG. .

  During operation of the engine 10, the purge control valve 35 is turned on (opened) and the electromagnetic switching valve 41 is held in the state shown in the figure (communication between a and b), and fresh air is introduced by the intake negative pressure as described above. Then, the adsorbed fuel of the canister 33 is discharged to the intake manifold 16 via the purge pipe 34. Further, for example, when a leak check of the fuel evaporative gas flow path is performed immediately after the engine 10 is stopped, the purge control valve 35 is turned off (closed) and the electromagnetic switching valve 41 is energized to communicate between ac. State. Thereby, the inside of the fuel evaporative gas flow path becomes a sealed space. Then, the first suction pump 45 is driven by the motor M1 to depressurize the inside of the fuel evaporative gas passage, and a leak check is performed based on the pressure change at that time.

  Further, in the present embodiment, as a second floating HC treatment system, a communication passage (bypass passage) that communicates the downstream side of the throttle valve 14 of the intake pipe 11 and the intake port (not shown) of the engine 10. ) 60 is provided, and a second HC adsorbent 61 is interposed in the middle. In the communication path 60, between the intake pipe 11 and the second HC adsorbent 61, for example, a flow control valve 62 constituted by an electromagnetically driven duty control valve and a motor M2 capable of forward and reverse rotation are provided. A second pump 63 to be driven is provided. The second pump 63 sucks air in the intake port during forward rotation and returns it to the downstream side of the throttle valve 14 in the intake pipe 11, and air (air) downstream of the throttle valve 14 in the intake pipe 11 during reverse rotation. Is sucked and discharged to the intake port.

  The first HC adsorbent 18 and the second HC adsorbent 61 described above are formed of activated carbon or a catalyst component having an HC adsorption action (for example, a noble metal such as Pd). Alternatively, it may be formed by supporting Pd or the like on an alumina layer, or may be formed of zeolite. Of course, you may make it form combining 2 or more types among activated carbon, a zeolite, and a catalyst component.

  An electronic control unit (hereinafter referred to as an ECU) 70 is mainly composed of a microcomputer. The ECU 70 includes an air-fuel ratio detection signal of the air-fuel ratio sensor 23, other intake air amount signal, intake air temperature signal, engine cooling water. A water temperature signal, an engine speed signal, a throttle opening or an accelerator opening signal indicating the amount of depression of the accelerator pedal, an operation signal of an ignition switch (hereinafter referred to as IG switch), and the like are input. The ECU 70 controls the driving of the fuel injector 17 based on various input signals, and at the same time, the purge control valve 35, the electromagnetic switching valve 41, the motor M1 of the first suction pump 45, the flow rate control valve 62, and the second pump. The driving of the motor M2 etc. 63 is controlled. Further, the ECU 70 is provided with a soak timer for measuring the elapsed time after the engine is stopped.

  In the engine 10, HC remains in the vicinity of the intake port such as the intake manifold 16 due to fuel leaking from the fuel injector 17 (oil-tight leak), fuel blowing back from the combustion chamber, fuel inflow from the PCV passage, and the like. Even after the operation is stopped, the HC remains. If this residual HC is left unattended, floating HC in the vicinity of the intake port is sucked into the engine combustion chamber along with cranking at the next engine start, and is further discharged unburned. Therefore, in the present embodiment, floating HC in the vicinity of the intake port is sucked while the engine is stopped, thereby suppressing HC discharge when starting the engine. Details will be described below.

  FIG. 2 is a flowchart showing an example of a control procedure of air suction processing performed while the engine is stopped. This processing is performed as a function of the ECU 70. This air suction process is started by the ECU 70 when the time measured by the soak timer reaches a predetermined time. Specifically, a predetermined time (for example, 90 minutes) or more has elapsed since the engine was stopped (ignition OFF). Sometimes implemented. However, in practice, it is desirable that the air suction process be performed after the time when it is predicted that the oil-tight leak of the fuel injector 17 will be eliminated after the engine is stopped and the floating HC concentration near the intake port is stabilized. Then, the main air suction process is performed every predetermined time (for example, 8 hours) after the predetermined time has elapsed since the engine stopped.

  In the air suction process shown in the flowchart of FIG. 2, in step S201, ECU power ON processing is performed to turn on the power supply system of various devices related to air suction. In subsequent steps S202 to S204, the air suction execution conditions are satisfied. It is determined whether or not it has been done. That is, in step S202, it is determined whether or not the engine water temperature is in a predetermined temperature range (for example, 0 to 60 ° C.), and in step S203, the intake air temperature is in a predetermined temperature range (for example, 0 to 60 ° C.). In step S204, it is determined whether air suction is not performed after the engine is stopped. As conditions for performing air suction, it is possible to use that the engine oil temperature and the transmission oil temperature are within a predetermined temperature range in addition to the above. And if each implementation condition is satisfy | filled, it will progress to step S205 and an air suction process will be performed. More specifically, all of the purge control valve 35, the electromagnetic switching valve 41, and the first suction pump 45 are turned on, and the three-way switching valve 50 is also turned on, that is, the three-way switching of the atmosphere communication path 42. The communication to the filter 49 side through the valve 50 is switched to the intake communication passage 51 side, and air suction is executed.

  On the other hand, when the engine water temperature or the intake air temperature is equal to or higher than a predetermined value, the temperature in the vicinity of the intake port (intake manifold 16) is high, and it is considered that the high boiling point HC is filled in the vicinity of the intake port. Therefore, the air suction by the first suction pump 45 is prohibited until the temperature in the vicinity of the intake port decreases and the high boiling point HC is liquefied.

  At the time of such air suction, the purge control valve 35 is turned on (opened) so that the intake manifold 16 and the canister 33 communicate with each other, and air suction by the first suction pump 45 is performed in this state. As a result, HC floating in the vicinity of the intake port is sucked through the purge pipe 34 and is adsorbed by the canister 33. At this time, the pump 45 is driven while the air suction flow rate of the first suction pump 45 is limited so that the HC does not blow through the canister 33. Specifically, the air suction flow rate is limited by intermittently driving the first suction pump 45 or limiting the drive voltage or drive current of the first suction pump 45.

  Further, when the fuel stored in the fuel tank 31 is highly volatile, the air suction is executed when the fuel evaporative gas is adsorbed to the canister 33 to the full capacity. Then, although the HC floating near the intake port is not adsorbed to the canister 33, as described above, the atmosphere communication path 42 is switched to the intake communication path 51 side via the three-way switching valve 50, and the intake pipe 11 Therefore, the air is only circulated and HC is not released to the outside through the filter 49. During the air circulation, the floating HC is adsorbed by the first HC adsorbent 18 provided at the bottom of the surge tank 15.

  Thereafter, in step S206, it is determined whether or not a predetermined time (for example, about 1 minute) has elapsed after the start of air suction. If the predetermined time has not elapsed, the present processing is terminated. If the predetermined time has elapsed, the process proceeds to step S207, and the ECU power is turned off.

  After the fuel (HC) is adsorbed to the canister 33 as described above, the purge control valve 35 is opened according to the engine operating state at that time during engine operation, and the HC adsorbed to the canister 33 passes through the purge pipe 34. Released. That is, at this time, both the electromagnetic switching valve 41 and the first suction pump 45 are turned off, and the three-way switching valve 50 is also turned off, that is, the intake air communication via the three-way switching valve 50 in the atmosphere communication path 42. Communication to the passage 51 side is switched to the filter 49 side. When the canister purge execution condition is satisfied, such as that the engine 10 is in a driving state, the engine speed is greater than or equal to a predetermined value, and the intake air amount is greater than or equal to a predetermined value, the purge control valve 35 is turned on. A canister purge is performed.

  According to the embodiment described above in detail, the following excellent effects can be obtained.

  Air suction through the purge pipe 34 is performed while the engine is stopped, so that floating HC in the vicinity of the intake port is efficiently adsorbed to the canister 33. Further, during engine operation, high boiling point HC is mixed and floats in the vicinity of the intake port due to fuel blowback from the combustion chamber, but the floating HC is not adsorbed to the canister 33 as a hydrocarbon adsorbent. , A decrease in HC adsorption performance can be suppressed. As described above, at the next engine start, it is possible to suppress a situation in which floating HC in the vicinity of the intake port is sucked into the combustion chamber and discharged without being burned with cranking. As a result, the HC emission amount can be effectively reduced.

  Further, by using the canister 33 as a hydrocarbon adsorbent and by using the first suction pump 45 (negative pressure pump) of the leak check module 40, it is possible to prevent an increase in cost. Since the three-way switching valve 50 is disposed upstream of the filter 49 and the intake communication passage 51 communicated with the downstream side of the throttle valve 14 via the three-way switching valve 50 is provided, Even when the adsorption capacity is exceeded, HC is prevented from being released to the outside.

  In the above-described embodiment, the canister 33 of the fuel evaporative emission control device is used as the hydrocarbon adsorbent. However, as described above, when the evaporation gas is adsorbed to the extent that it exceeds the adsorption capacity of the canister 33. There is a possibility that a high concentration of HC is introduced into the intake pipe 11 at the time of air suction, and the adsorption capacity of the first HC adsorbent 18 as the first floating HC treatment system may be exceeded. In order to prevent this, an embodiment using the second floating HC treatment system including the second HC adsorbent 61 will be described below as a second embodiment of the present invention.

  FIG. 3 is a flowchart showing an example of a control procedure of air suction processing that is also performed while the engine is stopped in the second embodiment of the present invention, and this processing is performed as a function of the ECU 70. This air suction process is started by the ECU 70 when the time measured by the soak timer reaches a predetermined time, and specifically, is executed when a predetermined time or more has elapsed since the engine was stopped (ignition OFF). However, in practice, it is desirable that the air suction process be performed after the time when it is predicted that the oil-tight leak of the fuel injector 17 will be eliminated after the engine is stopped and the floating HC concentration near the intake port is stabilized. Then, the main air suction process is performed every predetermined time (for example, 8 hours) after the predetermined time has elapsed since the engine stopped.

  In the air suction process shown in the flowchart of FIG. 3, in step S301, an ECU power ON process is performed to turn on the power supply system of various devices related to air suction. In subsequent step S302, the engine water temperature is kept within a predetermined temperature range ( For example, in step S303, it is determined whether the intake air temperature is in a predetermined temperature range (for example, 0-60 ° C). In step S304, the engine is stopped. Thereafter, whether or not air suction execution conditions are satisfied is determined based on whether or not air suction is not performed. And if each implementation condition is satisfy | filled, it will progress to step S305 and an air suction process will be performed. More specifically, both the flow rate control valve 62 and the motor M2 of the second pump 63 are turned on, the flow rate control valve 62 is opened, and the second pump 63 is driven in the forward rotation direction to suck air. Is executed. Thus, the floating HC in the vicinity of the intake port is adsorbed by the second HC adsorbent 61 via the communication path 60.

  On the other hand, when the engine water temperature or the intake air temperature is equal to or higher than a predetermined value, the temperature in the vicinity of the intake port (intake manifold 16) is high, and it is considered that the high-boiling point HC is filled in the vicinity of the intake port. The air suction by the second pump 63 is prohibited until the high-boiling point HC is liquefied until the temperature near the intake port is lowered, which is the same as in the previous embodiment. Thereafter, in step S306, it is determined whether or not a predetermined time (for example, about 1 minute) has elapsed after the start of air suction. If the predetermined time has not elapsed, the present processing is terminated. If the predetermined time has elapsed, the process proceeds to step S307, where ECU power-off processing is executed.

  In addition, this 2nd embodiment may be performed together with the above-mentioned 1st embodiment, or separately.

  Next, the HC desorption (purge) processing of the second HC adsorbent 61 in the second floating HC processing system will be described with reference to the flowchart shown in FIG. This HC desorption process is a process performed at a predetermined cycle during engine operation, and this process is performed as a function of the ECU 70. Therefore, in step S401, the amount of HC adsorbed by the HC adsorbent 61 is acquired. This HC adsorption amount is, for example, an estimated amount of HC adsorption amount adsorbed to the HC adsorbent 61 by the above-described air suction process of FIG. 3 executed while the engine is stopped, and is adsorbed by one air suction process. The amount of HC adsorbed is obtained by an experiment or the like in advance and mapped, and it is obtained based on the value and how many times of air suction processing have been executed, or the progress of desorption processing described later. Then, in the next step S402, it is determined whether or not the desorption has been completed. If it has been completed, this process is terminated.

  On the other hand, if it is determined in step S402 that the desorption is not completed, the process proceeds to step S403, and it is determined whether the desorption condition is satisfied. This may be determined, for example, based on whether or not the warm-up of the catalyst 22 and the air-fuel ratio sensor 23 has been completed. Even when the warm-up is not completed, this process is temporarily terminated. When the warm-up is completed, the process proceeds to step S404, and the HC desorption process is performed. Specifically, the flow control valve 62 is opened to a predetermined opening. The opening degree of the flow rate control valve 62 can be changed according to the processing capacity of the catalyst 22, and when the warming up of the catalyst 22 is completely finished, the opening degree is increased, and the second HC adsorbent The air flow rate passing through 61 is increased. In the next step S405, the HC desorption amount is calculated based on the air flow rate that has passed through the second HC adsorbent 61. Further, in step S406, the HC adsorption amount acquired in step S401 and the step S405. Based on the calculated HC desorption amount, the residual HC adsorption amount in the second HC adsorbent 61 is calculated and stored, and this routine is temporarily terminated.

  Next, engine performance improvement processing (1) and (2) executed in a state where the HC desorption processing of the second HC adsorbent 61 in the second floating HC processing system described above is completed will be described with reference to FIG. This will be described with reference to the flowchart shown in FIG. These engine performance improvement processes are performed for the purpose of increasing the air flow rate under predetermined operating conditions of the engine 10, and the processes are performed at a predetermined cycle as a function of the ECU 70.

  Therefore, in the engine performance improvement process (1), it is determined in step S501 whether or not the HC desorption process of the second HC adsorbent 61 has been completed. This is performed in the same manner as the determination in step S402 described above, and when the desorption is not completed, this process is temporarily terminated. As a result of the determination, if the desorption is completed, the process proceeds to the next step S502. In this step S502, whether or not the engine 10 is under a predetermined operating condition, for example, whether or not the engine 10 is in a high rotational speed (for example, 3000 rpm or more) that requires a relatively large amount of intake air, Determination is made based on the engine speed signal input to ECU 70. When the engine speed is not high, this process is temporarily terminated. Conversely, when the engine speed is high, the flow proceeds to step S503, and the flow control valve 62 is opened as a performance improvement process. The opening of the flow control valve 62 is opened to a predetermined opening in accordance with the engine speed. That is, as the engine speed increases, the opening degree increases, and the air flow rate through the communication path 60 increases. Thus, since the engine 10 is supplied with air introduced into the intake port via the communication passage 60 in addition to the air sucked through the intake manifold 16, the output performance can be improved. is there.

  As for the engine performance improving process (2), it is similarly determined in step S601 whether or not the HC desorption process of the second HC adsorbent 61 has been completed. This is performed in the same manner as in the determinations in steps S402 and S501 described above. When the desorption is not completed, this process is temporarily terminated. As a result of the determination, if desorption is completed, the process proceeds to the next step S602. In step S602, whether the engine 10 is under a predetermined operating condition, for example, in this embodiment, whether the throttle opening or the accelerator opening is equal to or greater than a predetermined opening is input to the ECU 70. It is determined based on the throttle opening or accelerator opening signal. If it is not greater than the predetermined opening, this process is temporarily terminated. On the other hand, when the opening is equal to or greater than the predetermined opening degree, the process proceeds to step S603 where the flow rate control valve 62 is opened and the motor M2 of the second pump 63 is turned on as the performance improvement process (2). 63 is driven in the reverse direction. Thus, when a predetermined amount of air is sent to the intake port through the communication passage 60, the effect of pulsation due to the intake phase difference between the cylinders is eliminated by a kind of supercharging action that prevents the pressure drop of the intake port. The engine performance is improved.

  At this time, the opening degree of the flow control valve 62 is preferably opened while being adjusted to a predetermined opening degree in accordance with the throttle opening degree or the accelerator opening degree from the viewpoint of preventing the occurrence of a torque step.

  In the present embodiment, for example, when the fuel is cut during engine operation, the second pump 63 is operated in the forward rotation direction to perform air suction, and the fuel adhering to the intake port wall surface, so-called port wet, is removed. When the second HC adsorbent 61 is adsorbed or the engine 10 is mounted on a hybrid vehicle, the second pump is provided between the time when the ignition switch is turned on and the time when the engine is actually started. By operating 63 in the forward direction, air suction is performed, and hydrocarbons present in the intake port can be adsorbed. Hereinafter, these air suction processes will be described with reference to the flowcharts shown in FIGS. These air suction processes are executed as a function of the ECU 70 at a predetermined time and period.

  First, in the air suction process at the time of fuel cut, in step S701, it is determined based on the drive control signal to the fuel injector 17 whether or not it is in the fuel cut state. When not in the fuel cut state, this process is temporarily terminated. Conversely, when in the fuel cut state, the process proceeds to step S702, where it is determined whether or not the second HC adsorbent 61 has an adsorption capacity. When the above-described HC desorption process such as immediately after the start of the engine 10 is not completed, this process is temporarily terminated. As a result of the determination, for example, when the desorption is completed and there is an adsorption remaining capacity, the process proceeds to the next step S703, the flow control valve 62 is opened, the motor M2 of the second pump 63 is turned on, and the first The second pump 63 is driven in the forward direction. Thus, this air suction process during fuel cut prevents the fuel adhering to the intake port wall surface, so-called port wet, from being adsorbed by the second HC adsorbent 61 and being discharged to the exhaust system wastefully. .

  Next, in the air suction process before starting the engine, it is determined in step S801 whether an ignition switch (IG) is ON, and in step S802, it is determined whether the engine is before starting. If it is not ON or not before starting, this process is terminated. If the ignition switch (IG) is ON and the engine is not started, the process proceeds to step S803, the flow control valve 62 is opened, the motor M2 of the second pump 63 is turned ON, and the second pump 63 is turned ON. Are driven in the forward direction. Thus, the air suction process is executed when the engine 10 is stopped before starting, and hydrocarbons present in the intake port are adsorbed. In order to reliably prevent HC discharge during cranking, it is desirable to remove floating HC in the vicinity of the intake port immediately before the start of cranking. According to the present embodiment, removal of floating HC is preferably performed. Can do. Thereby, HC discharge at the time of cranking can be prevented more reliably.

It is a schematic diagram which shows the outline | summary of one embodiment of this invention. It is a flowchart which shows one form of the air suction process control of embodiment of this invention. It is a flowchart which shows one form of the other air suction process control of embodiment of this invention. It is a flowchart which shows one form of the desorption process control of embodiment of this invention. It is a flowchart which shows one form of the performance improvement process (1) control of embodiment of this invention. It is a flowchart which shows one form of the performance improvement process (2) control of embodiment of this invention. It is a flowchart which shows one form of the air suction process control at the time of fuel cut of embodiment of this invention. It is a flowchart which shows one form of the air suction process control before engine starting of embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Engine 11 Intake pipe 12 Air cleaner 13 Air flow meter 14 Throttle valve 15 Surge tank 16 Intake manifold 17 Fuel injector 18 First HC adsorbent 21 Exhaust pipe 22 Catalyst 23 Air-fuel ratio sensor 31 Fuel tank 32 Evaporative gas conduit 33 Canister (HC adsorbent )
34 Purge piping 35 Purge control valve 37 Canister conduit 40 Leak check module 41 Electromagnetic switching valve 42 Atmospheric communication passage 43 Negative pressure introduction passage 44 Check valve 45 First suction pump 46 Bypass passage 47 Reference orifice 48 Pressure sensor 49 Filter 50 Three-way switching valve 51 Intake communication passage M1 motor 60 Communication passage 61 Second HC adsorbent 62 Flow control valve 63 Second pump M2 motor 70 Electronic control unit (ECU)

Claims (5)

An internal combustion engine provided with a hydrocarbon adsorption execution means for causing air containing hydrocarbons remaining in the intake system to pass through the hydrocarbon adsorbent using the pump means while the engine is stopped and adsorbing hydrocarbons to the hydrocarbon adsorbent In
An air circulation path forming means for forming an air circulation path for circulating air from the downstream side to the upstream side of the hydrocarbon adsorbent during the execution of the hydrocarbon adsorption execution means is provided. Hydrocarbon emission reduction device for internal combustion engines.   The hydrocarbon adsorption execution means includes an air suction passage communicated downstream of a throttle valve in an intake passage, a hydrocarbon adsorbent provided in the air suction passage, and a suction pump for performing an air suction operation. The circulation path forming means includes a three-way switching valve provided downstream of the suction pump, and an air circulation path that allows the three-way switching valve and the intake passage to communicate with each other. Hydrocarbon emission reduction device for internal combustion engines.   The hydrocarbon adsorption execution means uses a canister in the fuel evaporative emission control device of the fuel tank as a hydrocarbon adsorbent, and further, a bypass passage having one end communicating with the intake port downstream of the throttle valve and the other end 3. A hydrocarbon emission reduction device for an internal combustion engine according to claim 1 or 2, further comprising a bypass passage in which another pump means capable of forward and reverse rotation and another hydrocarbon adsorbent are interposed. .   The another pump means is rotated forward under a predetermined condition while the engine is stopped, and air containing hydrocarbons remaining in the intake port through the bypass passage is passed through another hydrocarbon adsorbent to separate hydrocarbons. 4. The hydrocarbon emission reduction device for an internal combustion engine according to claim 3, further comprising another hydrocarbon adsorption execution means for adsorbing to said hydrocarbon adsorbent. The said another pump means is reversely rotated under a predetermined condition during operation of the engine, and comprises a performance improving means for sending a predetermined amount of air through the bypass passage to the intake port. Hydrocarbon emission reduction device for internal combustion engines.

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