JP2001227421A - Hydrocarbon exhaust amount reducing device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an HC exhaust amount at the time of cranking. SOLUTION: An HC absorbent 18 formed of activated carbon, zeolite and a catalyst component (Pd, for instance) having an HC absorbent action is installed within an intake passage of a surge tank 15, etc. The HC absorbent 18 is substantially uniformly adhered to an inner wall surface of the intake passage (the surge tank 15) and an HC component diffused within the intake passage is made to be absorbed by the HC absorbent 18 while an engine is stopped, reducing intake pressure loss while the engine is operated. As a result, HC amount sucked into a cylinder can be reduced before fuel injection (before completion of a cylinder discrimination) in cranking and HC exhaust amount in the cranking can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for reducing the amount of hydrocarbons emitted from an internal combustion engine (hereinafter referred to as "HC").

[0002]

2. Description of the Related Art In recent automobiles, in order to reduce the amount of HC emission, 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 an exhaust pipe to discharge the HC from the engine. To purify HC.

[0003]

Incidentally, after the engine is stopped, a part of the fuel injected during the previous operation may remain in the intake passage such as a surge tank due to a blowback or the like. Also, when the engine is stopped, fuel may leak from the fuel injection valve little by little and diffuse into the intake passage. Due to these reasons, fuel (HC) diffused into the intake passage after the engine is stopped is drawn into the cylinder at the next engine start.

However, immediately after the start of cranking, 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, HC sucked into the cylinder burns. Without being discharged to the exhaust pipe. In addition, at the time of the cold start, since the catalyst in the exhaust pipe is in an inactive state, HC in the exhaust gas cannot be sufficiently purified. As a result, the HC accumulated in the intake passage is discharged to the atmosphere as it is, and this is the H at the start of cranking.
This was the cause of increasing C emissions.

[0005] The present invention has been made in view of such circumstances, and its object is to provide an H
It is an object of the present invention to provide a device for reducing hydrocarbon emissions of an internal combustion engine that can reduce C emissions.

[0006]

According to a first aspect of the present invention, there is provided an apparatus for reducing hydrocarbon emissions in an internal combustion engine, comprising the steps of: In this configuration, a hydrocarbon removing means for removing the (HC) component is provided. With this configuration, the HC component remaining in the intake passage can be removed by the hydrocarbon removing means while the engine is stopped, so that the HC that is drawn into the cylinder before the fuel injection during cranking (before the cylinder discrimination is completed).
The amount can be reduced, and the amount of HC emission during cranking can be reduced. Moreover, even if there is some fuel leakage from the fuel injection valve, it can be removed by the hydrocarbon removing means, so that the design criteria for the oil tightness of the seal portion of the fuel injection valve can be relaxed. Accordingly, the cost of the fuel injection valve can be reduced.

In this case, a hydrocarbon adsorbent for adsorbing hydrocarbons may be provided in the intake passage as the hydrocarbon removing means. With this configuration, it is possible to reduce the amount of HC emission during cranking with a simple configuration in which the hydrocarbon adsorbent is provided in the intake passage.

Various types of hydrocarbon adsorbents are conceivable. For example, as described in claim 3, the hydrocarbon adsorbent is made of at least one of activated carbon, zeolite, and a catalyst component capable of adsorbing hydrocarbons. It is good to form. Activated carbon, zeolite, and a catalyst component having a hydrocarbon-adsorbing effect are all excellent in the ability to adsorb HC, and therefore can efficiently adsorb HC in the intake passage.

Various methods are also conceivable for the method of installing the hydrocarbon adsorbing material. For example, it is preferable that the hydrocarbon adsorbing material be adhered to the inner wall surface of the intake passage substantially uniformly. . By doing so, the contact area between the HC diffused in the intake passage and the hydrocarbon adsorbent can be increased, and the HC adsorption ability can be increased.

Further, it is preferable that the hydrocarbon adsorbent is provided on the inner wall surface of the intake passage so as to reduce the intake pressure loss. By doing so, the intake performance during engine operation is not impaired, and a decrease in engine output can be prevented.

Further, the hydrocarbon adsorbent may be accommodated in a recess formed in the inner wall of the intake passage. With this configuration, since the flow passage cross-sectional area of the intake passage is not narrowed by the hydrocarbon adsorbent, many hydrocarbon adsorbents are installed in the intake passage without increasing the intake pressure loss during engine operation. And the HC adsorption capacity can be increased.

Further, the hydrocarbon adsorbent may be provided upstream of the throttle valve. With this configuration, HC diffused upstream of the intake passage can also be adsorbed by the hydrocarbon adsorbent.

In this case, the hydrocarbon adsorbent may be installed in the case of the air cleaner. In the case of the air cleaner, the hydrocarbon adsorbent can be relatively easily installed.

When the hydrocarbon adsorbent is provided upstream of the throttle valve, the throttle valve and / or idle speed control valve may be opened while the engine is stopped. With this configuration, it is possible to ensure that the upstream side and the downstream side of the throttle valve of the intake passage communicate with each other while the engine is stopped, and to adsorb HC in the entire intake passage to the hydrocarbon adsorbent.

In a recent gasoline engine vehicle, in order to prevent the fuel evaporative gas from being released from the fuel tank into the atmosphere, the fuel evaporative gas discharged from the fuel tank is adsorbed by a canister, and the canister is adsorbed during operation of the engine. The fuel evaporative gas is purged into the intake passage.

In the case where such a fuel evaporative gas purging system is provided, a canister is used as the hydrocarbon removing means so as to communicate between the intake passage and the canister while the engine is stopped. May be. This makes it possible to adsorb HC in the intake passage to the canister while the engine is stopped, thereby removing HC in the intake passage. In this configuration, since the canister can be used as the hydrocarbon removing means, it is not necessary to newly provide a hydrocarbon removing means (hydrocarbon adsorbing material).
There is an advantage that the cost can be reduced.

In this case, if the space between the inlet and the outlet of the canister communicates with the space inside the canister, the communication between the intake passage and the canister while the engine is stopped causes the fuel to come out of the fuel tank. The fuel evaporated gas may leak into the intake passage through the space in the canister.

As a countermeasure, it is preferable that the space between the inlet and the outlet of the canister is not communicated with the space in the canister. With this configuration, even when the intake passage communicates with the canister while the engine is stopped, it is possible to prevent the fuel evaporative gas discharged from the fuel tank from passing through the canister and leaking into the intake passage.

According to a twelfth aspect of the present invention, a purge control valve provided in a fuel evaporative gas purge passage between the canister and the intake passage or an open / close valve provided in parallel with the purge valve is opened while the engine is stopped. Thus, the communication between the intake passage and the canister may be made while the engine is stopped. Generally, in a fuel evaporative gas purge system, a purge control valve for controlling a purge flow rate is provided in a fuel evaporative gas purge passage between a canister and an intake passage. The communication between the intake passage and the canister can be established. However, since a general purge control valve is constituted by a normally closed solenoid valve, in order to keep the purge control valve open while the engine is stopped, power is continuously supplied to the purge control valve while the engine is stopped. There is a need. In order to avoid this, a normally-open type on-off valve may be provided in parallel with the purge control valve. In this case, the on-off valve is maintained in the open state without energizing the on-off valve while the engine is stopped. Thus, a communication state between the intake passage and the canister is maintained through the on-off valve.

Further, a stirrer for stirring the air in the intake passage while the engine is stopped may be provided. With this configuration, the HC component in the intake passage does not stay at a position distant from the hydrocarbon removing unit during the stop of the engine, and HC in the intake passage is efficiently removed by convection of air generated by stirring of the air. Can be removed.

Alternatively, the air in the intake passage may be agitated by appropriately opening and closing the throttle valve while the engine is stopped. If you do this,
Since the air in the intake passage can be agitated using the throttle valve, there is no need to provide a new agitating member.

[0022]

[Embodiment (1)] An embodiment (1) of the present invention will be described below with reference to FIGS.
As shown in FIG. 1, an air cleaner 13 is provided at the most upstream portion of an intake pipe 12 of an engine 11 which is an internal combustion engine.
A throttle valve 14 for adjusting the throttle opening is provided downstream of the air cleaner 13. Further, a surge tank 15 is provided downstream of the throttle valve 14. The surge tank 15 includes the engine 11
An intake manifold 16 for introducing air into each cylinder is provided, and a fuel injection valve 17 for injecting fuel is attached near each intake port of the intake manifold 16 of each cylinder. The intake pipe 12, the air cleaner 13, the surge tank 15, and the intake manifold 16 constitute an intake passage.

As shown in FIG. 2, a large number of particulate HC adsorbents 18 (hydrocarbon removing means) adhere to the inner wall surface of the surge tank 15 almost uniformly over the entire inner wall surface to such an extent that the intake pressure loss does not increase. The HC diffused into the intake passage while the engine is stopped is adsorbed by the HC adsorbent 18. The HC adsorbent 18 is made of activated carbon or a catalyst component (a noble metal such as Pd) having an HC adsorbing action. Alternatively, the HC adsorbent 19 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 a catalyst component. still,
As shown in FIG. 3, the inner wall surface of the surge tank 15
The adsorbent 19 may be coated in a layer.

According to the embodiment (1) described above, since the HC adsorbent 18 (19) is provided on the inner wall surface of the surge tank 15, the HC diffused into the intake passage while the engine is stopped is provided. It can be adsorbed by the HC adsorbent 18 (19). As a result, the HC that is drawn into the cylinder before the fuel injection (before the completion of the cylinder discrimination) at the time of the next cranking is performed.
By reducing the amount, the amount of HC emission at the time of cranking can be reduced, and the exhaust emission can be improved. In addition, even if there is some fuel leakage from the fuel injection valve 17, it can be adsorbed by the HC adsorbent 18 (19), so that the design criteria for the oil tightness of the seal portion of the fuel injection valve 17 are relaxed. Accordingly, the manufacture of the fuel injection valve 17 is facilitated and the manufacturing cost can be reduced.

In this embodiment (1), the granular (or layered) HC adsorbents 18 (19) are provided almost uniformly on the entire inner wall surface of the surge tank 15.
HC and HC adsorbent 18 diffused into the intake passage while the engine is stopped while reducing the intake pressure loss during engine operation.
(19) The contact area with (19) can be increased, and the HC adsorbing ability while the engine is stopped can be increased while preventing a decrease in engine output.

[Embodiment (2)] In the embodiment (1), the HC adsorbent 18 (1) is provided on the inner wall surface of the surge tank 15.
9) is provided, but in the embodiment (2) of the present invention, in order to prevent the cross-sectional area of the flow path of the surge tank 15 from being narrowed by the HC adsorbent, any one of FIGS. In the embodiment, the recesses 20 to 23 are formed on the inner wall of the surge tank 15, and the HC adsorbents 24 to 27 are accommodated in the recesses 20 to 23.

In the example of FIG. 4, a recess 20 is formed on one side of the surge tank 15, and the HC adsorbent 24 is formed in the recess 20.
To accommodate. In the example of FIG. 5, concave portions 21 are formed on both sides of the surge tank 15, respectively, and each concave portion 2 is formed.
1 accommodates an HC adsorbent 25. In the example of FIG. 6, a plurality of streamline concave portions 22 are formed in the upper part of the surge tank 15 so as to extend substantially in the intake direction, and the HC adsorbent 26 is accommodated in each concave portion 22. . In the example of FIG. 7, a plurality of streamline concave portions 23 are formed in the lower portion of the surge tank 15 so as to extend in a direction substantially perpendicular to the intake direction.
7 are accommodated. The shape, position, and number of each of the recesses 20 to 23 may be appropriately changed.

According to the embodiment (2) described above, H is formed in the recesses 20 to 23 formed on the inner wall of the surge tank 15.
Since the C adsorbents 24 to 27 are accommodated, the flow passage cross-sectional area of the surge tank 15 is not narrowed by the HC adsorbents 24 to 27. For this reason, many HC adsorbents 24 to 27 can be installed in the surge tank 15 without increasing the intake pressure loss during the operation of the engine, and the amount of adsorbed HC is increased, and the effect of reducing the amount of HC emission is increased. be able to.

[Embodiment (3)] In the above embodiments (1) and (2), the HC adsorbent is provided in the surge tank 15, but the embodiment (3) of the present invention shown in FIG. In this configuration, the HC adsorbent 28 is installed in the case 13a of the air cleaner 13 provided at the most upstream portion of the intake pipe 12, and an electronic throttle system for driving the throttle valve 29 by a motor (not shown) is mounted. age,
While the engine is stopped, the engine control circuit (not shown) opens the throttle valve 29 as shown in FIG.
I try to make it.

According to the embodiment (3), the HC adsorbent 2
8 is installed upstream of the throttle valve 29 (inside the air cleaner case 13a), and the throttle valve 29 is opened when the engine is stopped.
9 can be reliably communicated between the upstream side and the downstream side, and the HC in the entire intake passage can be reliably adsorbed to the HC adsorbent 28.

Further, in the present embodiment (3), the HC adsorbent 28 is installed in the air cleaner case 13a, so that the HC adsorbent 28 is installed in the surge tank 15 or the like.
There are few restrictions, and the HC adsorbent 28 can be easily installed.

In a system having an idle speed control valve for controlling the amount of bypass air of the throttle valve 29 during idle operation, the idle speed control valve may be opened while the engine is stopped. However, while the engine is stopped, the throttle valve 29
Can reliably communicate the upstream side and the downstream side.
Alternatively, both the throttle valve 29 and the idle speed control valve may be opened.

However, the throttle valve 29 (idle speed control valve) may not be opened while the engine is stopped. This is because even when the throttle valve 29 is fully closed, a gap is formed around the throttle valve 29 so that intake air required for idling operation can be supplied to the engine 11.
This is because the upstream side and the downstream side of No. 9 can communicate with each other.

[Embodiment (4)] In an embodiment (4) of the present invention, as shown in FIG. 9, a canister 33 is connected to a fuel tank 30 via a fuel evaporative gas purge passage 31, and inside the canister 33, An adsorbent 34 such as activated carbon for adsorbing fuel evaporative gas is accommodated. On the other hand, a fuel evaporative gas purge passage 36 for purging (releasing) the fuel evaporative gas adsorbed by the adsorbent 34 into the intake pipe 12 is provided between the canister 33 and the intake pipe 12. A purge control valve 37 for adjusting a purge flow rate is provided in the middle of the passage 36. The purge control valve 37 is constituted by a normally closed solenoid valve. An atmosphere opening / closing valve 35 is provided on the bottom surface of the canister 33, and the atmosphere opening / closing valve 35 is opened to introduce the atmosphere into the canister 33 during the execution of the purge of the fuel evaporative gas.

In the fuel evaporative gas purge passage 36,
A bypass passage 38 that bypasses the purge control valve 37 is provided, and a normally open on-off valve 39 is provided in the middle of the bypass passage 38. Further, in the canister 33, an upper space portion of the adsorbent 34 is partitioned by a partition plate 40,
Inlet portion 41 into which fuel evaporative gas flows from fuel tank 30
An outlet 42 through which the fuel evaporative gas in the canister 33 flows out to the intake pipe 12 side is configured so as not to communicate with a space in the canister 33.

An engine control circuit (not shown) controls the purge flow rate by closing the on-off valve 39 and controlling the opening of the purge control valve 37 during operation of the engine. On the other hand, when the engine is stopped, the purge control valve 37 is closed and the on-off valve 39 is opened, whereby the intake pipe 12 and the canister 33 are opened.
Are communicated through the bypass passage 38. Thus, HC in the intake passage can be adsorbed by the adsorbent 34 of the canister 33 to remove HC in the intake passage.

In the embodiment (4) described above, since the canister 33 is used as the hydrocarbon removing means, there is no need to newly provide a hydrocarbon removing means (HC adsorbent), and the demand for cost reduction can be satisfied. Can be.

If the space between the inlet portion 41 and the outlet portion 42 of the canister 33 is communicated with a space inside the canister 33, the intake pipe 12 and the canister 33 can be connected while the engine is stopped. In addition, there is a possibility that the fuel evaporative gas discharged from the fuel tank 30 leaks into the intake pipe 12 through the space in the canister 33.

In this regard, in this embodiment (4), the canister 33 partitions the space between the inlet 41 and the outlet 42 with the partition plate 40, and the space between the inlet 41 and the outlet 42 is the canister 33. The internal space is not communicated with the intake pipe 12 and the canister 33 while the engine is stopped.
Can be prevented from leaking from the fuel tank 30 through the canister 33 to the intake pipe 12.

Incidentally, as shown in FIG.
Is inserted into the adsorbent 34 of the canister 33, so that the canister 3
The space between the inlet 41 and the outlet 42 of the third canister 33 may not be communicated with each other in the space inside the canister 33.

Since a purge control valve 37 is provided in the fuel evaporative gas purge passage 36 between the canister 33 and the intake pipe 12, if the purge control valve 37 is opened while the engine is stopped, the intake air Tube 12 and canister 3
3 can be communicated. However, in a general fuel evaporative gas purging system, as described above, the purge control valve 37 is a normally-closed solenoid valve. Therefore, it is necessary to maintain the purge control valve 37 in an open state while the engine is stopped. It is necessary to keep energizing the purge control valve 37 while the engine is stopped, so that the battery is burdened,
Problems such as heat generation of the purge control valve 37 occur.

In consideration of such circumstances, in the present embodiment (4), the normally open on-off valve 39 is provided in the bypass passage 38 which bypasses the purge control valve 37, so that the engine is stopped while the engine is stopped. Even without energizing the on-off valve 39,
The on-off valve 39 is maintained in the open state, and the communication between the intake pipe 12 and the canister 33 can be maintained in a communicating state.

However, the bypass passage 38 and the opening / closing valve 39 may be omitted, and the purge control valve 37 may be opened while the engine is stopped so that the communication between the intake pipe 12 and the canister 33 is established. In this case, the purge control valve 37 may be a normally-open solenoid valve.

[Embodiment (5)] In an embodiment (5) of the present invention shown in FIG. 11, in addition to the structure of the embodiment (1), the surge tank 15 is driven by a motor, a solenoid, or the like. A stirring member 43 is provided, and an engine control circuit (not shown) stirs the stirring member 43 a predetermined number of times while the engine is stopped to stir the air in the intake passage. Note that a configuration may be adopted in which a stirring member 43 is added to the configuration of any of the embodiments (2) to (4). In addition, the installation position of the stirring member 43 is not limited to the inside of the surge tank 15 and may be appropriately changed.

In the structure of the embodiment (5) of the present invention, the convection of air can be forcibly generated in the intake passage by the stirring operation of the stirring member 43 even when the engine is stopped. The HC component in the inside does not stay in a place away from the hydrocarbon removing means such as the HC adsorbent, and the HC in the intake passage can be efficiently removed.

When an electronic throttle system is provided, the air in the intake passage may be stirred by opening and closing the throttle valve a predetermined number of times while the engine is stopped. With this configuration, the air in the intake passage can be agitated by using the throttle valve, so that it is not necessary to newly provide an agitating member, and the cost does not increase. In addition, the present invention can be implemented with appropriate modifications such that an HC adsorbent (hydrocarbon removing means) may be installed in the intake pipe 12, the intake manifold 16, or the like.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a main part on an engine intake side showing an embodiment (1).

FIG. 2 is a partial enlarged cross-sectional view of a surge tank for explaining an installation mode of the HC adsorbent according to the embodiment (1).

FIG. 3 is a partially enlarged cross-sectional view of a surge tank for explaining another installation mode of the HC adsorbent of the embodiment (1).

FIG. 4 is a view showing an installation form (first example) of the HC adsorbent according to the embodiment (2).
Cross-sectional view of the intake system for explaining example)

FIG. 5 is a view showing an installation form (second embodiment) of the HC adsorbent according to the embodiment (2).
Cross-sectional view of engine intake system for explaining example)

FIG. 6 is a view showing an installation mode (third embodiment) of the HC adsorbent according to the embodiment (2).
(A) is a longitudinal sectional view of a main part, and (b) is a transverse sectional view of the same.

FIG. 7 is a view showing an installation form (fourth embodiment) of the HC adsorbent according to the embodiment (2).
(A) is a longitudinal sectional view of a main part on the engine intake side, and (b) is a transverse sectional view of the same.

FIG. 8 is a longitudinal sectional view of a main part on the engine intake side showing the embodiment (3).

FIG. 9 is a longitudinal sectional view of a main part on the engine intake side showing the embodiment (4).

FIG. 10 is a longitudinal sectional view of a canister showing a modification of the embodiment (4).

FIG. 11 is a longitudinal sectional view of a main part on the engine intake side showing an embodiment (5).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe (intake passage), 13 ... Air cleaner (intake passage), 13a ... Case, 14 ... Throttle valve, 15 ... Surge tank (intake passage), 16 ... Intake manifold (intake passage) ), 18 ... H
C adsorbent (hydrocarbon removing means), 19 ... HC adsorbent, 2
0 to 23 recess, 24 to 27 HC adsorbent, 28 HC
Adsorbent, 29: throttle valve, 30: fuel tank, 31
... fuel evaporative gas purge passage, 33 ... canister (hydrocarbon removing means), 34 ... adsorbent, 36 ... fuel evaporative gas purge passage, 37 ... purge control valve, 39 ... open / close valve, 40 ... partition plate, 41 ... inlet part, 42 ... outlet part, 43 ... stirring member.

Claims (14)

[Claims] 1. A device for reducing the amount of hydrocarbons discharged from an internal combustion engine, comprising: a hydrocarbon removing device for removing hydrocarbon components remaining in an intake passage of the internal combustion engine when the engine is stopped. A hydrocarbon emission reducing device for an internal combustion engine, comprising: 2. The apparatus for reducing hydrocarbon emissions of an internal combustion engine according to claim 1, wherein a hydrocarbon adsorbent for adsorbing hydrocarbons is provided in the intake passage as the hydrocarbon removing means. 3. The carbonization of an internal combustion engine according to claim 2, wherein the hydrocarbon adsorbent is formed of at least one of activated carbon, zeolite, and a catalyst component having an action of adsorbing hydrocarbons. Hydrogen emission reduction device. 4. The apparatus according to claim 2, wherein the hydrocarbon adsorbent is substantially uniformly attached to an inner wall surface of the intake passage. 5. The carbonization of an internal combustion engine according to claim 2, wherein the hydrocarbon adsorbent is provided on an inner wall surface of the intake passage so as to reduce an intake pressure loss. Hydrogen emission reduction device. 6. The hydrocarbon discharge of an internal combustion engine according to claim 2, wherein the hydrocarbon adsorbent is accommodated in a recess formed in an inner wall of the intake passage. Volume reduction device. 7. The system according to claim 2, wherein the hydrocarbon adsorbent is provided upstream of a throttle valve.
7. The hydrocarbon emission reduction device for an internal combustion engine according to any one of claims 6 to 6. 8. The apparatus according to claim 7, wherein the hydrocarbon adsorbent is installed in a case of an air cleaner. 9. The device for reducing hydrocarbon emissions of an internal combustion engine according to claim 7, wherein the throttle valve and / or the idle speed control valve are opened while the engine is stopped. 10. A canister for adsorbing fuel evaporative gas is provided in a fuel evaporative gas purge passage connecting the intake passage and a fuel tank, and the evaporative gas is purged from the canister to the intake passage during operation of the engine. 2. The hydrocarbon according to claim 1, further comprising a fuel evaporative gas purge system, wherein the canister is used as the hydrocarbon removing unit, and the intake passage communicates with the canister while the engine is stopped. 3. Emission reduction device. 11. The canister has a space in the canister between an inlet through which fuel evaporative gas flows in from the fuel tank and an outlet through which fuel evaporative gas in the canister flows out toward the intake passage. 11. The device for reducing hydrocarbon emissions of an internal combustion engine according to claim 10, wherein the device is configured so as not to communicate. 12. When the engine is stopped by opening a purge control valve provided in a fuel evaporative gas purge passage between the canister and the intake passage or an on-off valve provided in parallel with the engine during the stop of the engine. And a communication between the intake passage and the canister.
2. The device for reducing hydrocarbon emissions of an internal combustion engine according to claim 1. 13. The apparatus according to claim 1, further comprising a stirring member for stirring air in the intake passage when the engine is stopped. 14. The hydrocarbon discharge amount of the internal combustion engine according to claim 1, wherein air in the intake passage is agitated by appropriately opening and closing a throttle valve while the engine is stopped. Reduction device.