JP4292671B2 - Hydrocarbon emission reduction device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydrocarbon emission reduction device for an internal combustion engine provided with a catalyst for purifying hydrocarbons (hereinafter referred to as “HC”) in exhaust gas of the internal combustion engine.
[0002]
[Prior art]
In recent automobiles, in order to reduce HC emissions, 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 pipe to purify HC emitted from the engine. Like to do.
[0003]
[Problems to be solved by the invention]
By the way, after the engine is stopped, in the intake passage such as a surge tank, part of the fuel injected during the previous operation may remain due to blow-back or the like. Further, when the engine is stopped, fuel may leak little by little from the fuel injection valve and diffuse in the intake passage. For these reasons, the fuel (HC) diffused into the intake passage after the engine is stopped is sucked into the cylinder at the next engine start.
[0004]
However, immediately after the start of cranking, the fuel injection of the fuel injection valve is not started until the cylinder discrimination is completed, and combustion does not occur in the cylinder. Therefore, the HC sucked into the cylinder is not combusted in the exhaust pipe. To be discharged. In addition, at the time of cold start, since the catalyst in the exhaust pipe is in an inactive state, HC in the exhaust cannot be sufficiently purified. As a result, the HC accumulated in the intake passage is discharged into the atmosphere as it is, which causes an increase in the amount of HC discharged at the start of cranking.
[0005]
The present invention has been made in view of such circumstances. Therefore, the object of the present invention is to provide an internal combustion engine capable of reducing the discharge amount of HC accumulated in the intake passage into the atmosphere when the engine is stopped. The object is to provide a device for reducing hydrocarbon emissions.
[0006]
[Means for Solving the Problems]
  In order to achieve the above object, a hydrocarbon emission reduction device for an internal combustion engine according to claim 1 of the present invention is a hydrocarbon remaining in an intake passage of an internal combustion engine when the engine is stopped (hereinafter referred to as “residual hydrocarbon”). Is temporarily stored, and the residual hydrocarbon is released into the intake air after activation of the catalyst by the hydrocarbon release control means. That is, after the catalyst is activated, even if residual HC is not sufficiently burned in the cylinder and is discharged to the exhaust pipe, the HC can be purified by the active catalyst, and the amount of HC emission can be reduced. Can do. Here, the determination of the catalyst activity may be performed by detecting or estimating the catalyst temperature, or the catalyst activity may be determined based on whether or not the elapsed time after engine start is a predetermined time or more. .According to a first aspect of the present invention, there is provided a hydrocarbon adsorbent that adsorbs residual HC in the intake passage while the engine is stopped, and a switching means for switching the degree of contact between the hydrocarbon adsorbent and the intake air. When the hydrocarbon adsorbed on the adsorbent is released, the switching means is switched to a position where the degree of contact between the hydrocarbon adsorbent and the intake air is increased (hereinafter referred to as “hydrocarbon release position”). If the degree of contact between the hydrocarbon adsorbent and the intake air increases, the release of HC from the hydrocarbon adsorbent is promoted. In this configuration, the timing for switching between adsorption and release of residual HC can be freely set by the switching means, and control is easy.
[0007]
In recent vehicles, the air-fuel ratio of exhaust gas is detected by an air-fuel ratio sensor (or oxygen sensor) to perform air-fuel ratio feedback control. In general, the air-fuel ratio sensor is activated prior to the catalyst. Therefore, even before the catalyst is activated, the air-fuel ratio can be feedback-controlled to the target air-fuel ratio after the air-fuel ratio sensor is activated. Therefore, if a predetermined time required for the activation of the air-fuel ratio sensor has elapsed since the start, even if the release of residual HC is started, the fuel injection amount is corrected by the air-fuel ratio feedback control to reduce the fuel injection amount according to the residual HC release amount. As a result, the amount of HC discharged from the internal combustion engine is reduced.
[0008]
In this case, as described in claim 2, it is preferable that the air-fuel ratio is controlled to the target air-fuel ratio by correcting the fuel injection amount to be reduced in accordance with the residual hydrocarbon release amount during the residual hydrocarbon release control. . That is, if the fuel injection amount is corrected to be reduced by the amount of rich deviation due to the release of residual HC, the air-fuel ratio of exhaust gas can be prevented from deviating from the target air-fuel ratio (catalyst purification window), and the HC purification efficiency of the catalyst can be increased. Can do.
[0010]
  In this case, the claim3As described above, the air-fuel ratio may be controlled to the target air-fuel ratio by correcting the fuel injection amount to decrease when the switching means is switched to the hydrocarbon release position. In this way, the fuel injection amount can be corrected by the amount of rich deviation due to the release of residual HC, so that the air-fuel ratio of the exhaust gas can be prevented from deviating from the target air-fuel ratio (catalyst purification window), and the HC purification of the catalyst. Efficiency can be increased.
[0011]
  In recent years, in order to promote combustion in a cylinder, a tumble generation valve provided in an intake passage is driven to change the intake air flow to generate a tumble flow in the cylinder. In an internal combustion engine equipped with such a tumble generating valve, the claims4As described above, the hydrocarbon adsorbing material may be provided in the vicinity of the tumble generating valve, and this tumble generating valve may be used as the switching means. In this way, since HC can be released from the hydrocarbon adsorbent using the tumble production valve, it is not necessary to provide a new switching means, and the cost can be reduced accordingly.
[0012]
  Or claims5As described above, the hydrocarbon adsorbent may be provided in the vicinity of the throttle valve or the idle speed control valve, and the throttle valve or the idle speed control valve may be used as the switching means. Also in this case, since the throttle valve or the idle speed control valve can be used as the switching means, it is not necessary to newly provide a switching means, and the cost can be reduced.
[0013]
  Claims6As described above, when releasing the hydrocarbon adsorbed on the hydrocarbon adsorbent, the outside air may be introduced into the hydrocarbon adsorbent by the outside air introduction means. In this way, the release timing of HC can be freely set according to the introduction timing of outside air, and control is easy.
[0014]
  Further claims7As described above, the residual HC release control may be executed during a period in which the intake air amount is equal to or greater than a predetermined amount. That is, if the residual HC is released when the intake air amount is large, the ratio of the HC release amount (rich component increase amount) to the intake air amount can be reduced, and the rich deviation of the air-fuel ratio can be suppressed to be small.
[0015]
  Claims8As described above, the in-cylinder charged air amount may be increased by introducing the outside air or increasing the throttle opening during the residual hydrocarbon release control. In this way, the increase in the rich component due to the release of residual HC can be offset by the increase in the lean component (oxygen) due to the introduction of outside air or the increase in the throttle opening, thereby preventing a rich shift in the air-fuel ratio. be able to.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
[Embodiment (1)]
Hereinafter, an embodiment (1) of the present invention will be described with reference to FIGS. As shown in FIG. 1, a throttle valve 14 that adjusts the throttle opening is provided in an intake pipe 12 of an engine 11 that is an internal combustion engine, and a surge tank 15 is provided downstream of the throttle valve 14. The surge tank 15 is provided with an intake manifold 16 for introducing air into each cylinder of the engine 11, and a fuel injection valve 17 for injecting fuel is attached in the vicinity of the intake port of the intake manifold 16 of each cylinder. . The intake pipe 12, the surge tank 15, and the intake manifold 16 constitute an intake passage.
[0017]
The surge tank 15 is provided with an HC adsorbing material 18 so that the HC adsorbing material 18 adsorbs HC remaining in the intake passage when the engine is stopped (hereinafter referred to as “residual HC”). The HC adsorbent 18 is made of activated carbon or a catalyst component having an HC adsorption action (for example, a noble metal such as Pd). Alternatively, the HC adsorbent 18 may be formed by supporting Pd or the like on an alumina layer, or may be formed of zeolite. Of course, the HC adsorbent 18 may be formed by combining two or more of activated carbon, zeolite, and catalyst components.
[0018]
In this embodiment (1), a recess 19 is formed on one side of the surge tank 15, and the HC adsorbent 18 is accommodated in the recess 19. Is not narrowed. Further, on the upstream side of the HC adsorbent 18, an on-off valve 20 (switching means) driven by a motor, a solenoid or the like is provided. When the on-off valve 20 is switched to the closed position shown by the solid line in FIG. 1, the contact degree between the intake air flowing through the surge tank 15 and the HC adsorbent 18 is reduced and HC is adsorbed by the HC adsorbent 18. Hold. On the other hand, when the on-off valve 20 is switched to the valve open position (hydrocarbon release position) indicated by a dotted line in FIG. 1, a part of the intake air flowing in the surge tank 15 flows toward the HC adsorbent 18, and the intake air and the HC The degree of contact with the adsorbent 18 increases and HC is released from the HC adsorbent 18.
[0019]
On the other hand, the exhaust pipe 21 of the engine 11 is provided with a catalyst 22 such as a three-way catalyst that purifies HC in the exhaust gas, and an air-fuel ratio sensor 23 (or oxygen) that detects the air-fuel ratio of the exhaust gas upstream of the catalyst 22. Sensor).
[0020]
The engine control circuit (hereinafter referred to as “ECU”) 24 is mainly composed of a microcomputer, controls the fuel injection amount and ignition timing, and stores the HC release control program of FIG. 2 stored in a ROM (storage medium). By executing the above, the release timing of the HC adsorbed on the HC adsorbent 18 while the engine is stopped is controlled after the activation of the catalyst 22 or after a predetermined time has elapsed from the start.
[0021]
Hereinafter, processing contents of the HC release control program of FIG. 2 will be described. This program is periodically executed after the ignition switch is turned on, for example, and serves as a hydrocarbon emission control means in the claims. When the program is started, first, at step 101, it is determined whether or not the elapsed time after the start is equal to or longer than a predetermined time T1. The predetermined time T1 is set to a time (for example, 100 seconds) necessary for the catalyst 22 to be in an active state after starting. Therefore, if the elapsed time after the start does not reach the predetermined time T1, it is determined that the catalyst 22 is in an inactive state, the process proceeds to step 102, the on-off valve 20 is held in the closed position, and the HC is stopped while the engine is stopped. The HC adsorbed on the adsorbent 18 is continuously held in the state adsorbed on the HC adsorbent 18.
[0022]
Thereafter, the routine proceeds to step 103, where it is determined whether or not the elapsed time after starting is a predetermined time T2 or more and the intake air amount Ga is a predetermined amount G1 (for example, 10 g / s) or more. Here, the predetermined time T2 is set to a time (for example, 30 seconds) necessary for the air-fuel ratio sensor 23 to be in an active state after starting. Accordingly, the air-fuel ratio sensor 23 is activated and the air-fuel ratio feedback control based on the output of the air-fuel ratio sensor 23 is started when the predetermined time T2 elapses from the start, so that HC is released from the HC adsorbent 18. Even if the air-fuel ratio deviates richly, the fuel injection amount is corrected to decrease by the air-fuel ratio feedback control, and the rich deviation is corrected.
[0023]
If the elapsed time after the start does not reach the predetermined time T2, it is determined that the air-fuel ratio sensor 23 is in an inactive state, the process proceeds to step 105 without opening the on-off valve 20, and a high temperature restart (start In order to determine whether or not the catalyst 22 is in an active state from the beginning, it is determined whether or not the temperature of the catalyst 22 is lower than the activation temperature Ta (for example, 300 ° C.). The temperature of the catalyst 22 may be detected by a temperature sensor (not shown) installed on the catalyst 22, or may be estimated from the cooling water temperature or the like. If the temperature of the catalyst 22 is lower than the activation temperature Ta, since the catalyst 22 is in an inactive state, this program is terminated while the on-off valve 20 is closed.
[0024]
During the period when the catalyst 22 is inactive, only when it is determined as “Yes” in step 103, that is, the elapsed time after the start is equal to or longer than the predetermined time T2 (after activation of the air-fuel ratio sensor 23), and the intake air Only during the period when the amount Ga is equal to or greater than the predetermined amount G1, the routine proceeds from step 103 to step 104, the on-off valve 20 is opened to release HC from the HC adsorbent 18, and fuel injection is performed according to the amount of HC released. The amount is corrected to decrease (see FIG. 4). The fuel injection amount decrease correction amount A is calculated according to the integrated value of the valve opening time of the on-off valve 20 by the table of FIG. As the valve opening time integrated value of the on-off valve 20 increases, the amount of HC released from the HC adsorbent 18 decreases. Therefore, in the table of FIG. 3, the amount of decrease correction A decreases as the valve opening time integrated value of the on-off valve 20 increases. It is set to be. By the fuel injection amount reduction correction in step 104 and the air-fuel ratio feedback control described above, the fuel injection amount reduction correction according to the HC release amount from the HC adsorbent 18 is performed with good response.
[0025]
On the other hand, when it is determined that the elapsed time after the start is equal to or longer than the predetermined time T1 (“Yes” in Step 101) or the temperature of the catalyst 22 is equal to or higher than the activation temperature Ta (“No” in Step 105), the catalyst 22 is activated. In step 106, the on-off valve 20 is held open to release HC from the HC adsorbent 18, and the fuel injection amount reduction correction is executed. Also in this case, the reduction correction amount A is calculated by the table of FIG.
[0026]
According to the embodiment (1) described above, the residual HC in the intake passage is adsorbed by the HC adsorbent 18 while the engine is stopped, and the on-off valve 20 is opened after the catalyst 22 is activated after starting. Since HC is released from the HC adsorbent 18, even if the HC released from the HC adsorbent 18 is not sufficiently burned in the cylinder and is discharged to the exhaust pipe 21, the HC is released by the active catalyst 22. Can be purified. In addition, the fuel injection amount can be corrected to be reduced in accordance with the amount of HC released from the HC adsorbent 18 by the fuel injection amount reduction correction and air-fuel ratio feedback control in step 104 of FIG. Deviation from the target air-fuel ratio (purification window of the catalyst 22) can be prevented, and the HC purification efficiency at the catalyst 22 can be increased. As a result, the amount of HC emissions into the atmosphere can be effectively reduced.
[0027]
Further, in the present embodiment (1), even before the catalyst 22 is activated, after a predetermined time T2 has elapsed from the start (after the activation of the air-fuel ratio sensor 23), as shown in FIG. Is equal to or greater than the predetermined amount G1, the on-off valve 20 is opened to release HC from the HC adsorbent 18, and the fuel injection amount is corrected to decrease in accordance with the HC release amount. Thus, even if HC is released from the HC adsorbent 18 before the catalyst 22 is activated, the HC from the HC adsorbent 18 is corrected by the fuel injection amount reduction correction and the air-fuel ratio feedback control in step 104 of FIG. The fuel injection amount reduction correction according to the released amount can be performed with very good response, and the amount of HC discharged from the engine 11 into the exhaust pipe 21 can be reduced. Moreover, since HC is released from the HC adsorbent 18 during a period when the intake air amount Ga is equal to or greater than the predetermined amount G1, the ratio of the HC release amount (rich component increase amount) to the intake air amount can be reduced, and the air-fuel ratio can be reduced. Rich shift can be reduced.
[0028]
In the present embodiment (1), an on-off valve 20 is provided on the upstream side of the HC adsorbent 18, and the on-off valve 20 is opened to increase the degree of contact between the intake air and the HC adsorbent 18, Since HC is released from the HC adsorbent 18, the HC release timing can be freely set by the on-off valve 20, and the specification of HC release control can be easily changed.
[0029]
In the embodiment (1), the recess 19 is formed on one side of the surge tank 15. However, as shown in the example of FIG. 5, the recess 25 is formed on both sides of the surge tank 15, and each recess 25 is formed. The HC adsorbent 26 may be accommodated therein, and an on-off valve 27 may be provided on the upstream side of each HC adsorbent 26. Alternatively, as in the example of FIG. 6, a plurality (or one) of recesses 28 may be formed in the upper portion of the surge tank 15 so as to extend substantially in the intake direction, and the HC adsorbent 29 is placed in each recess 28. The on-off valve 30 may be provided on the downstream side (or upstream side) of each HC adsorbent 29 by accommodating.
[0030]
The switching means for switching the degree of contact between the HC adsorbent and the intake air may use, for example, a sliding shutter that slides along the exposed surface of the HC adsorbent, in addition to the on-off valve. Can be implemented.
[0031]
In the present invention, the processing of steps 103 and 104 (processing of releasing HC during the period when the catalyst 22 is inactive) in FIG. 2 is omitted, or the processing of either one of steps 101 and 105 is performed. May be omitted.
[0032]
[Embodiment (2)]
Next, Embodiment (2) of this invention is demonstrated using FIG. 7 thru | or FIG. As shown in FIG. 7, the intake manifold 16 is provided with a tumble generating valve 31 for generating a tumble flow in the cylinder. The tumble generating valve 31 opens and closes the lower half of the flow passage cross section of the intake manifold 16. An HC adsorbent 32 is fixed to the inner wall surface of the intake manifold 16 upstream of the tumble generating valve 31. The HC adsorbent 32 is formed in a streamline extending substantially in the intake direction so as not to cause intake pressure loss.
[0033]
In this case, when the tumble generating valve 31 is located at the closed position indicated by the solid line in FIG. 7, the intake air in the intake manifold 16 flows to the side opposite to the HC adsorbent 32 (the upper half of the intake manifold 16). Therefore, the degree of contact between the intake air and the HC adsorbent 32 is reduced, and the HC adsorbent 32 is held in an adsorbed state. On the other hand, when the tumble generating valve 31 is switched to the valve open position indicated by the dotted line in FIG. 7, the intake air in the intake manifold 16 also flows to the HC adsorbent 32 side (lower half of the intake manifold 16). The degree of contact between the HC adsorbent 32 and HC is released from the HC adsorbent 32. Thereby, the tumble generating valve 31 plays the same role as the on-off valve 20 of the embodiment (1), and functions as a switching means in the claims.
[0034]
In the present embodiment (2), the ECU 24 executes the HC release control program of FIG. 8 and uses the tumble generating valve 31 to set the HC release timing from the HC adsorbent 32 in the same manner as in the above embodiment (1). Control. Specifically, after the start-up, until the catalyst 22 is activated, the tumble generating valve 31 is held in the closed position, and the HC adsorbent 32 is held in a state where HC is adsorbed (steps 201 and 202). However, even if the catalyst 22 is inactive, if the predetermined time T2 or more has elapsed from the start and the intake air amount Ga is the predetermined amount G1 or more, the routine proceeds to step 204 where the tumble generating valve 31 is opened. HC is released from the HC adsorbent 32 and the fuel injection amount is corrected to decrease. The fuel injection amount decrease correction amount A is calculated according to the integrated value of the valve opening time of the tumble generating valve 31 by the table of FIG. Further, after the activation of the catalyst 22, the routine proceeds to step 206, where the tumble generation valve 31 is normally controlled, and when the tumble generation valve 31 is opened, HC is released from the HC adsorbent 32 and the fuel injection amount is corrected to decrease. To do.
[0035]
In the embodiment (2) described above, the same effect as that of the embodiment (1) can be obtained. In addition, in the present embodiment (2), the tumble generating valve 31 is used as a switching means for switching the degree of contact between the intake air and the HC adsorbent 32, so that it is not necessary to newly provide a switching means, and a cost reduction is required. Can also be met.
[0036]
[Embodiment (3)]
In the embodiment (3) of the present invention shown in FIG. 10, an electronic throttle system for driving the throttle valve 33 with a motor (not shown) or the like is mounted, and the bypass air amount is controlled in the bypass passage 34 of the throttle valve 33. A plurality of streamline HC adsorbents 36 are provided on the inner wall surface of the intake pipe 12 downstream of the throttle valve 33 and upstream of the junction 34a of the bypass passage 34. It is fixed.
[0037]
In this case, when the throttle valve 33 is located at the closed position shown by the solid line in FIG. 10, the intake air in the intake pipe 12 is downstream of the HC adsorbent 36 even if the idle speed control valve 35 is opened. Therefore, the degree of contact between the intake air and the HC adsorbent 36 is reduced, and the HC adsorbent 32 is held in an adsorbed state. On the other hand, when the throttle valve 33 is switched to the valve open position indicated by the dotted line in FIG. 10, the intake air in the intake pipe 12 flows along the HC adsorbent 36, so the degree of contact between the intake air and the HC adsorbent 36 increases. Then, HC is released from the HC adsorbent 36. Thereby, the throttle valve 33 plays the same role as the tumble generating valve 31 of the embodiment (2), and functions as a switching means in the scope of the claims.
[0038]
In the present embodiment (3), the throttle valve 33 is used to control the HC release timing from the HC adsorbent 32 by the same method as in the above embodiment (2). Therefore, the HC release control program used in the present embodiment (3) only needs to read “tumble generation valve” as “throttle valve” in the processing of steps 202, 204 and 206 of the HC release control program of FIG.
[0039]
In the embodiment (3) described above, the throttle valve 33 is used as a switching means for switching the degree of contact between the intake air and the HC adsorbent 36, so that a switching means is newly provided as in the embodiment (2). There is no need and the cost can be reduced. Note that an HC adsorbent may be installed on the downstream side of the idle speed control valve 35, and the idle speed control valve 35 may be used as switching means for switching the degree of contact between the intake air and the HC adsorbent.
[0040]
In the above embodiments (2) and (3), the HC adsorbents 32 and 36 are fixed to the inner wall surface of the intake passage. However, the installation form of the HC adsorbent may be changed as appropriate, for example, As shown in FIG. 11, a large number of granular HC adsorbents 37 may be attached substantially uniformly to the inner wall surface of the intake manifold 16 (or the intake pipe 12 or the surge tank 15). Alternatively, as shown in FIG. 12, the HC adsorbent 38 may be coated in layers on the inner wall surface of the intake manifold 16 (or the intake pipe 12 or the surge tank 15).
[0041]
[Embodiment (4)]
In the embodiment (4) of the present invention, as shown in FIG. 13A, an air pump 41 (outside air introduction means) is connected to the recess 19 formed in the surge tank 15 via an air introduction pipe 40. When releasing HC from the HC adsorbent 18 in the recess 19, the ECU 24 opens the on-off valve 20 and drives the air pump 41 to introduce outside air into the HC adsorbent 18 such as activated carbon in the recess 19. Thus, the release of HC from the HC adsorbent 18 is promoted by the action of both the intake air and the introduced outside air.
[0042]
In the present embodiment (4), the HC release timing can be freely set according to the opening timing of the on-off valve 20 and the outside air introduction timing, and the HC release control can be easily performed. Further, the increase in the rich component due to the release of residual HC can be offset by the increase in the lean component due to the introduction of the outside air, and the effect of preventing the deviation of the air-fuel ratio can also be obtained.
[0043]
Further, as shown in FIG. 13 (b), the upstream side of the throttle valve 14 of the intake pipe 12 and the recess 19 of the surge tank 15 are connected by an air introduction pipe 48, and control is performed halfway through the air introduction pipe 48. When the valve 49 is provided and HC is released from the HC adsorbent 18 in the recess 19, the on-off valve 20 is opened, the control valve 49 is opened, and the intake air is introduced into the recess 19 through the air introduction pipe 48. It is also possible to promote the release of HC from the HC adsorbent 18 by introducing it into the HC adsorbent 18 such as activated carbon.
[0044]
13A or 13B, the on-off valve 20 is omitted, and the HC release timing is set only by the external air introduction timing by the air pump 41 or only by the intake air introduction timing by the control valve 49. Also good.
[0045]
Further, the installation form of the HC adsorbent may be variously changed. For example, as shown in FIG. 14, a plurality of recesses 43 are formed in the lower part of the surge tank 15 so as to extend in a direction substantially perpendicular to the intake direction. An opening / closing valve 45 is provided on the upstream side of the HC adsorbent 44 accommodated in each recess 43, and an air pump 47 is connected to each recess 43 via an air introduction pipe 46, so that the HC adsorbent in the recess 43 is released when HC is released. The outside air may be introduced toward 44. Alternatively, as shown in FIG. 15, the upstream side of the throttle valve 14 of the intake pipe 12 and each recess 43 of the surge tank 15 are connected by an air introduction pipe 50, and a control valve is provided in the middle of the air introduction pipe 50. 51 may be provided. In any case, the on-off valve 45 may be omitted, and the HC release timing may be set only by the outside air introduction timing by the air pump 47 or only by the intake air introduction timing by the control valve 51.
[0046]
  In addition, the present invention, HWhile releasing C, the amount of air charged in the cylinder may be increased by increasing the throttle opening to prevent the rich deviation of the air-fuel ratio.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an engine control system showing an embodiment (1).
FIG. 2 is a flowchart showing a process flow of an HC release control program according to the embodiment (1).
FIG. 3 is a diagram conceptually showing a table of fuel injection amount reduction correction amounts according to the embodiment (1).
FIG. 4 is a time chart for explaining an execution example of HC release control according to the embodiment (1).
FIG. 5 is a cross-sectional view of the main part on the engine intake side for explaining a modification (first example) of the embodiment (1).
6A and 6B are diagrams for explaining a modified example (second example) of the embodiment (1), in which FIG. 6A is a longitudinal sectional view of the main part on the engine intake side, and FIG.
FIG. 7 is a longitudinal sectional view of the main part on the engine intake side showing the embodiment (2).
FIG. 8 is a flowchart showing the flow of processing of the HC release control program of the embodiment (2).
FIG. 9 is a diagram conceptually illustrating a table of fuel injection amount reduction correction amounts according to the embodiment (2).
FIG. 10 is a longitudinal sectional view of the main part on the engine intake side showing the embodiment (3).
FIG. 11 is a partially enlarged cross-sectional view of the intake manifold for explaining another installation mode (first example) of the HC adsorbent.
FIG. 12 is a partially enlarged cross-sectional view of the intake manifold for explaining another installation mode (second example) of the HC adsorbent.
13A is a cross-sectional view of the main part on the engine intake side showing the embodiment (4), and FIG. 13B is a cross-sectional view of the main part on the engine intake side showing a modification of the embodiment (4).
14A is a longitudinal sectional view of a main part on the engine intake side showing another embodiment (first example), and FIG. 14B is a transverse sectional view of the same.
FIG. 15 is a longitudinal sectional view of a main part on the engine intake side showing another embodiment (second example).
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe (intake passage), 15 ... Surge tank (intake passage), 16 ... Intake manifold (intake passage), 18 ... HC adsorbent, 20 ... On-off valve (switching means), DESCRIPTION OF SYMBOLS 22 ... Catalyst, 24 ... ECU (hydrocarbon release control means), 26 ... HC adsorbent, 27 ... Open / close valve (switching means), 29 ... HC adsorbent, 30 ... Open / close valve (switching means), 31 ... Tumble generation valve (Switching means), 32 ... HC adsorbent, 33 ... throttle valve (switching means), 35 ... idle speed control valve, 36 to 38 ... HC adsorbent, 40 ... air introduction pipe (outside air introduction means), 41 ... air pump ( Outside air introduction means), 44 ... HC adsorbent, 45 ... Open / close valve (switching means), 46 ... Air introduction pipe (outside air introduction means), 47 ... Air pump (outside air introduction means), 48 ... Air introduction pipe, 49 ... Control valve , 50 Air introduction pipe, 51 ... control valve.

Claims (8)

In a hydrocarbon emission reduction device for an internal combustion engine equipped with a catalyst for purifying hydrocarbons in exhaust gas of the internal combustion engine,
Hydrocarbon release control for temporarily storing hydrocarbons (hereinafter referred to as “residual hydrocarbons”) remaining in the intake passage of the internal combustion engine when the engine is stopped and releasing the residual hydrocarbons into the intake air after the activation of the catalyst Means ,
A hydrocarbon adsorbent that adsorbs residual hydrocarbons in the intake passage while the engine is stopped;
Switching means for switching the degree of contact between the hydrocarbon adsorbent and the intake air,
The hydrocarbon release control means is a position for increasing the degree of contact between the hydrocarbon adsorbent and the intake air when the hydrocarbon adsorbed on the hydrocarbon adsorbent is released (hereinafter referred to as “hydrocarbon release position”). hydrocarbon emissions reduction apparatus for an internal combustion engine, characterized in that switching to "hereinafter).   The hydrocarbon release control means controls the air-fuel ratio to the target air-fuel ratio by correcting the fuel injection amount of the fuel injection valve to be reduced according to the residual hydrocarbon release amount during the residual hydrocarbon release control. The apparatus for reducing hydrocarbon emissions of an internal combustion engine according to claim 1. The hydrocarbon release control means controls the air-fuel ratio to a target air-fuel ratio by correcting the fuel injection amount of the fuel injection valve to decrease when the switching means is switched to the hydrocarbon release position. 3. The hydrocarbon emission reduction device for an internal combustion engine according to 1 or 2 . Said hydrocarbon adsorbent is provided in the vicinity of the tumble generation valve installed in the intake passage, wherein the tumble generation valve to any one of claims 1 to 3, characterized in that used as the switching means Hydrocarbon emission reduction device for internal combustion engines. Said hydrocarbon adsorbent is provided in the vicinity of the throttle valve or idle speed control valve, any one of claims 1 to 3, characterized by using the throttle valve or the idle speed control valve as said switching means hydrocarbon emissions reduction apparatus for an internal combustion engine according to. Internal combustion according to any one of claims 1 to 5, characterized in that it comprises a fresh air introducing means for introducing the outside air into the hydrocarbon adsorbent when releasing hydrocarbons adsorbed on the hydrocarbon adsorbent Engine hydrocarbon emission reduction device. The hydrocarbon discharge of the internal combustion engine according to any one of claims 1 to 6 , wherein the hydrocarbon release control means executes the release control of the residual hydrocarbon during a period in which the intake air amount is a predetermined amount or more. Quantity reduction device. The hydrocarbon emissions control means according to any one of claims 1 to 7, characterized in that increasing the cylinder air charge amount by an increase in the outside air introduction or throttle opening during the controlled release of the residual hydrocarbons Hydrocarbon emission reduction device for internal combustion engines.

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