JP2001271717A - Release suppressing device for fuel vapor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a release suppressing device for fuel vapor capable of suppressing an increase in suction resistance of an internal combustion engine while suppressing the release of fuel vapor to the outside. SOLUTION: This release suppressing device for fuel vapor is provided with an opening and closing valve 51 provided in a suction passage 32 of an engine 11, a bypass passage 52 connected with the suction passage 32 so as to bypass the opening and closing valve 51, and a suction member 53 provided in the bypass passage 52. The opening and closing valve 51 is closed when the engine 11 stops. When fuel vapor generated in the vicinity of a combustion chamber 16 in the suction passage 32 flows toward an upstream side, its flow is suppressed by both of a closed throttle valve 23 and the opening and closing valve 51. Moreover, the fuel vapor flowing onto the upstream side and entering the bypass passage 52 is sucked by the suction member 53. On the other hand, while the engine 11 is operated, the opening and closing valve 51 is opened to suppress an increase of suction resistance of the engine 11 by the opening and closing valve 51.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel vapor emission control device.

[0002]

2. Description of the Related Art In an internal combustion engine such as an automobile engine, when the engine stops, for example, fuel leaking from a fuel injection valve into an intake passage evaporates, so that fuel vapor is present in the intake passage. . In this state, fuel vapor may flow toward the upstream side of the intake passage and be discharged from the upstream end to the outside.
As disclosed in Japanese Patent No. 82192, provision of an adsorbent for adsorbing fuel vapor in an intake passage has been considered. In this case, even when fuel vapor is generated near the fuel injection valve when the engine is stopped, for example, the fuel vapor is adsorbed by the adsorbent when flowing toward the upstream side of the intake passage. Therefore, release of fuel vapor to the outside of the intake passage (the intake system of the internal combustion engine) is suppressed.

[0003]

However, if an adsorbent is provided in the intake passage as described in the above-mentioned publication, the adsorbent becomes intake resistance during engine operation (particularly at high engine speed), and pumping loss of the internal combustion engine is reduced. This leads to a decrease in engine output and deterioration of fuel efficiency.

The present invention has been made in view of such circumstances, and has as its object to suppress the increase in intake resistance of an internal combustion engine while suppressing the emission of fuel vapor to the outside. An object of the present invention is to provide a device for suppressing the release of steam.

[0005]

The means for achieving the above object and the effects thereof will be described below. In order to achieve the above object, according to the first aspect of the present invention, there is provided a fuel vapor emission suppression device for suppressing the emission of fuel vapor present in an intake system of an internal combustion engine to an outside when the internal combustion engine is stopped. In addition to the throttle valve of the engine, an opening / closing valve that closes when the engine is stopped and opens at least when the engine is running at a high engine speed is provided in the intake passage of the engine.

According to this configuration, when the fuel vapor in the intake passage flows toward the upstream end when the engine is stopped, the flow of the fuel vapor to the upstream side is reduced by both the throttle valve and the opening / closing valve in the closed state. Thus, the emission of fuel vapor from the intake system of the internal combustion engine to the outside is suppressed. In addition, at the time of engine operation, the on-off valve opens at least at the time of high engine rotation, so that an increase in intake resistance due to closing of the on-off valve is suppressed. Accordingly, it is possible to suppress the intake resistance of the internal combustion engine while suppressing the fuel vapor from being released from the intake system of the internal combustion engine to the outside.

It should be noted that the on-off valve may be such that the air circulation area in the intake system of the internal combustion engine is substantially "0" when the valve is closed. In this case, the on-off valve is operated during operation of the engine. Will be opened. Also, as an on-off valve,
When the valve is closed, an air flow area in the intake system that is limited to a predetermined value larger than “0” may be adopted,
In this case, the on-off valve may be closed when the engine is running at a low speed.

According to a second aspect of the present invention, in the first aspect of the present invention, the on-off valve limits an air flow area in an intake system of the internal combustion engine to a predetermined value or less when the valve is closed. An adsorbent for adsorbing fuel vapor is provided on the air flow path when the on-off valve is closed.

According to this structure, when the fuel vapor in the intake passage flows toward the upstream end when the engine is stopped, the fuel vapor flows to the adsorbent when passing through the air flow path when the on-off valve is closed. Since the fuel vapor is adsorbed, the release of fuel vapor from the intake system of the internal combustion engine to the outside can be accurately suppressed.

According to the third aspect of the present invention, the first or second aspect is provided.
In the invention described above, the on-off valve has an air flow area in the intake passage that is substantially "0" when the on-off valve is closed, and bypasses the on-off valve to an intake system of an internal combustion engine and the adsorbent. A bypass passage provided with:

With this configuration, when the fuel vapor in the intake passage flows toward the upstream end when the engine is stopped, the fuel vapor enters the bypass passage because the on-off valve is closed. Since the fuel vapor is adsorbed by the adsorbent in the bypass passage, the release of the fuel vapor from the intake system of the internal combustion engine to the outside can be accurately suppressed.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the on-off valve has an air flow area in the intake passage substantially “0” when the on-off valve is closed.
A bypass passage bypassing the on-off valve is provided in the intake system of the internal combustion engine, and the air passage area of the bypass passage is smaller than the air passage area of the intake passage.

With this configuration, when the fuel vapor in the intake passage flows toward the upstream end when the engine is stopped, it becomes difficult for the fuel vapor to pass through the bypass passage. The release of steam can be accurately suppressed.

According to the fifth aspect of the present invention, the third or fourth aspect is provided.
In the invention described in the above, an opening control means for controlling the opening of the on-off valve based on the engine operating state during the operation of the internal combustion engine is further provided.

[0015] The fuel vapor adsorbed by the adsorbent is carried to the combustion chamber by the air flowing through the bypass passage and flowing downstream during operation of the engine and is processed. Therefore, when the on-off valve is controlled to the closed side during engine operation, the amount of air passing through the bypass passage increases, the amount of fuel carried from the adsorbent to the combustion chamber increases, and purification of the adsorbent proceeds. According to the configuration in which the opening degree of the on-off valve is controlled in accordance with the engine operating state, the fuel vapor is not excessively conveyed from the adsorbent to the combustion chamber, and the combustion state is not deteriorated. The adsorbent can be purified by controlling the opening degree of the on-off valve so as not to excessively increase.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment in which the present invention is applied to a gasoline engine for an automobile will be described below with reference to FIGS.

As shown in FIG. 1, in an engine 11, a piston 12 is connected to a crankshaft 14 via a connecting rod 13.
Is converted into rotation of the crankshaft 14 by the connecting rod 13. Signal rotor 1 having a plurality of protrusions 14b on crankshaft 14
4a is attached. And the signal rotor 1
A crank position sensor 14c that outputs a pulse signal corresponding to each of the protrusions 14b when the crankshaft 14 rotates is provided on the side of 4a.

The intake system and the exhaust system of the engine 11 are provided with an intake passage 32 and an exhaust passage 33 connected to the combustion chamber 16. In the intake system of the engine 11, a throttle valve 23 for adjusting the intake air amount of the engine 11 is provided in the intake passage 32. The opening of the throttle valve 23 is detected by a throttle position sensor 44. Further, a vacuum sensor 36 for detecting the pressure in the intake passage 32 is provided in a portion of the intake passage 32 located downstream of the throttle valve 23. Note that, instead of the vacuum sensor 36, an air flow meter for detecting the intake air amount of the engine 11 may be provided.

The engine 11 is provided with a fuel injection valve 40 for injecting fuel into a portion near the combustion chamber 16 in the intake passage 32. Fuel is supplied to the fuel injection valve 40 at a predetermined pressure. When fuel is injected from the fuel injection valve 40 into the intake passage 32, an air-fuel mixture is formed by the fuel and air drawn into the combustion chamber 16 from the intake passage 32. Thereafter, the mixture is supplied to the combustion chamber 1
The ignition plug 41 is ignited and burns in a state where the fuel cell 6 is charged, and the engine 11 is driven by the combustion energy at this time. Further, the air-fuel mixture after combustion is sent to the exhaust passage 33 as exhaust gas.

Immediately after the operation of the engine 11 is stopped, the state where the fuel pressure acts on the fuel injection valve 40 is maintained, and the fuel pressure causes the fuel to flow from the fuel injection valve 40 to the intake passage 32 slightly. It will leak. Here, FIG. 2 shows the transition of the total amount of fuel leakage from the fuel injection valve 40 to the intake passage 32 with the lapse of time immediately after the engine 11 is stopped. In FIG. 2, a predetermined time t1 immediately after the engine is stopped represents a period during which the fuel pressure causing the above-described fuel leakage acts on the fuel injection valve 40. Therefore, immediately after the engine is stopped, the fuel continues to leak for a predetermined time t1, and the total amount of the fuel gradually increases, and after the predetermined time t1, the total amount of the fuel has a constant value. .

Further, since the engine temperature is high immediately after the operation of the engine 11 is stopped, a large amount of fuel leaks from the fuel injection valve 40 to the intake passage 32, and a large amount of fuel vapor is generated in the intake passage 32. Becomes Here, FIG. 3 shows a change in the concentration of the fuel vapor in the intake passage 32 with the lapse of time immediately after the engine 11 is stopped. In FIG. 3, a predetermined time t2 immediately after the engine is stopped represents a time required for the engine temperature to decrease to a predetermined value (for example, 40 ° C. to 45 ° C.). Then, the concentration of the fuel vapor gradually increases from immediately after the engine is stopped until a predetermined time t2, and after the predetermined time t2, the concentration of the fuel vapor gradually decreases.

As described above, during a predetermined time immediately after the engine 11 is stopped, fuel leaks from the fuel injection valve 40 to the intake passage 32, and the fuel is easily evaporated because the engine temperature is relatively high. As a result, the fuel vapor in the intake passage 32 rapidly increases, and the fuel vapor may flow toward the upstream end of the intake passage 32 and may be discharged from the upstream end to the outside. In order to suppress the release of the fuel vapor to the outside, it is conceivable to provide an adsorbent for adsorbing the fuel vapor in the intake passage 32. However, in this case, the adsorbent becomes an intake resistance, and the pumping loss of the engine 11 increases, resulting in a decrease in engine output and a decrease in fuel efficiency.

Therefore, in this embodiment, a fuel vapor emission suppression device is provided which can suppress the emission of fuel vapor from the intake system of the engine 11 to the outside without increasing the intake resistance of the engine 11.

The release control device includes an opening / closing valve 51 provided at a position upstream of the throttle valve 23 in the intake passage 32 and controlled to be opened and closed by a motor 54, and an intake passage so as to bypass the opening / closing valve 51. 32 includes a bypass passage 52 connected to the upstream and downstream sides of the on-off valve 51 at 32, and an adsorbent 53 made of activated carbon or the like provided in the bypass passage 52.

The on-off valve 51 has a higher airtightness when the valve is closed than the airtightness when the throttle valve 23 is closed, and the air flow area of the intake passage 32 is substantially "0".
The on-off valve 51 and the intake passage 32
Almost no air flow occurs between the inner surface of the wing. When the on-off valve 51 is opened, the air circulation area in the intake system of the engine 11 is the sum of the air circulation area in the intake passage 32 and the air circulation area in the bypass passage 52. At the time of valve operation, the value becomes equal to the air flow area in the bypass passage 52. Therefore, the engine 11
The air flow area in the intake system is limited to a predetermined value or less, that is, the air flow area in the bypass passage 52, by closing the on-off valve.

Further, the emission control device includes an electronic control unit (hereinafter referred to as an ECU) 92 for controlling the operation of the engine 11. This ECU 92 has ROM, C
It is configured as an arithmetic and logic operation circuit including a PU, a RAM, a backup RAM, and the like. And the ECU 9
2, a crank position sensor 14c, a vacuum sensor 36, a throttle position sensor 44, a motor 54, and the like are connected.

When the engine 11 is stopped, the ECU 92 controls the driving of the motor 54 and closes the on-off valve 51. Immediately after stopping the engine 11,
Fuel vapor is generated in a portion of the intake passage 32 located near the combustion chamber 16 due to fuel leakage from the fuel injection valve 40, and the fuel vapor flows toward the upstream side of the intake passage 32. The flow of the fuel vapor to the upstream side is suppressed by both the throttle valve 23 and the on-off valve 51 in the closed state. When the on-off valve 51 is closed, the fuel vapor enters the bypass passage 52 when flowing to the upstream side of the intake passage 32, and is adsorbed by the adsorbent 53 in the bypass passage 52. Therefore, after the engine 11 is stopped, the discharge of fuel vapor from the upstream end of the intake passage 32 to the outside is suppressed.

When the engine 11 is started and the operation is started while the engine 11 is stopped, air in the intake passage 32 is sucked into the combustion chamber 16. And
During operation immediately after the start of the engine 11, the ECU 9
2 controls the drive of the motor 54 to fully open the on-off valve 51 and suppresses an increase in the intake resistance of the engine 11 by the on-off valve 51. When the on-off valve 51 is fully open, air hardly flows through the bypass passage 52 to the combustion chamber 16 side, and most of the air sucked into the combustion chamber 16 passes only through the intake passage 32.

After starting the engine 11, the intake passage 3
2 is sucked into the combustion chamber 16,
When the fuel is stopped, the fuel vapor that tends to flow in the intake passage 32 to the upstream side is adsorbed by the adsorbent 53, so that the engine 1
The fuel vapor sucked into the combustion chamber 16 together with the air at the start of the first operation is reduced. Therefore, when the engine 11 starts, fuel vapor is sucked into the combustion chamber 16 together with air, and this fuel vapor causes the air-fuel ratio of the air-fuel mixture in the combustion chamber 16 to deviate from an appropriate value, thereby deteriorating the combustion state of the air-fuel mixture. Can be suppressed.

During the operation of the engine 11,
The fuel vapor adsorbed by the adsorbent 53 is transported to the combustion chamber 16 by the air flowing through the bypass passage 52 and flowing downstream during the operation of the engine 11 and is processed. Therefore, as the amount of air passing through the bypass passage 52 increases, the amount of fuel carried from the adsorbent 53 to the combustion chamber 16 increases, and the purification of the adsorbent 53 proceeds. The amount of air passing through the bypass passage 52 during operation of the engine 11 is changed by adjusting the opening of the on-off valve 51.

The ECU 92 adjusts the opening of the on-off valve 51 in accordance with the operating state of the engine 11, such as the engine speed NE, the intake pressure PM, and the throttle opening TA. That is,
The ECU 92 determines the engine load (combustion during one combustion cycle) from the engine speed NE determined based on the detection signal from the crank position sensor 14c and the intake pressure PM determined based on the detection signal from the vacuum sensor 36. The amount of gas sucked into the chamber 16) is calculated. And
The motor 54 is driven and controlled based on the engine load and a throttle opening TA or the like obtained based on a detection signal from the throttle position sensor 44, and the opening of the on-off valve 51 is adjusted.

The opening degree of the on-off valve 51 thus adjusted is
The value is such that the fuel is not excessively carried from the adsorbent 53 to the combustion chamber 16 to deteriorate the combustion state, and the intake resistance of the engine 11 by the on-off valve 51 does not excessively increase. When the operation state of the engine 11 is located on the slightly low load side in the high load region and the throttle opening TA is a value slightly closer to the closed side than the fully opened state, the opening degree of the on-off valve 51 becomes smaller than the fully opened state. The degree of opening is slightly closed. By controlling the opening degree of the on-off valve 51, the adsorbent 53 can be purified without deteriorating the combustion state or increasing the intake resistance.

According to the above-described embodiment, the following effects can be obtained. (1) Immediately after the engine 11 is stopped, fuel vapor is generated in a portion of the intake passage 32 located near the combustion chamber 16 due to fuel leakage from the fuel injection valve 40, and this fuel vapor flows upstream of the intake passage 32. It starts to flow toward the side.
However, the flow of the fuel vapor to the upstream side is suppressed by both the throttle valve 23 and the on-off valve 51 in the closed state. When the engine 11 is stopped, the on-off valve 5
1 is in a closed state, so that fuel vapor flows through the intake passage 3
2 flows into the bypass passage 52 when flowing upstream, and is adsorbed by the adsorbent 53 in the bypass passage 52. Therefore, after the engine 11 is stopped, the discharge of fuel vapor from the upstream end of the intake passage 32 to the outside is suppressed.
On the other hand, while the engine 11 is operating, the on-off valve 51 is opened, so that an increase in the intake resistance of the engine 11 due to the on-off valve 51 is suppressed. Accordingly, it is possible to suppress an increase in intake resistance by the on-off valve 51 during operation of the engine 11 while suppressing discharge of fuel vapor from the intake passage 32 to the outside when the engine 11 is stopped.

(2) When the engine 11 is stopped, the intake passage 3
When the engine 11 starts, when the air in the intake passage 32 is sucked into the combustion chamber 16 when the engine 11 is started, the fuel vapor is generated together with the air. Inhalation into the combustion chamber 16 can be reduced. Therefore, when the engine 11 starts, fuel vapor is sucked into the combustion chamber 16 together with air, and this fuel vapor causes the air-fuel ratio of the air-fuel mixture in the combustion chamber 16 to deviate from an appropriate value, thereby deteriorating the combustion state of the air-fuel mixture. Can be suppressed.

(3) During operation of the engine 11,
The on-off valve 51 according to the operating state of the engine 11, such as the engine speed NE, the intake pressure PM, and the throttle opening TA.
Is adjusted, and the amount of air that carries fuel vapor from the adsorbent 53 to the combustion chamber 16 through the bypass passage 52 is adjusted. Due to the opening degree control of the on-off valve 51 based on the operating state of the engine 11 as described above, the opening degree of the on-off valve 51 is such that fuel is excessively transferred from the adsorbent 53 to the combustion chamber 16 and the combustion state deteriorates. And the intake resistance of the engine 11 by the on-off valve 51 does not excessively increase. When the operation state of the engine 11 is located on the slightly low load side in the high load region and the throttle opening TA is a value slightly closer to the closed side than the fully opened state, the opening degree of the on-off valve 51 becomes smaller than the fully opened state. The degree of opening is slightly closed. By controlling the opening degree of the on-off valve 51, the adsorbent 53 can be purified without deteriorating the combustion state or increasing the intake resistance.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, the evaporative fuel from the intake system to the outside is provided by closing the on-off valve when the engine is stopped and limiting the air circulation area of the engine intake system to a predetermined value or less without providing the adsorbent in the bypass passage. Is to suppress the release of Further, in this embodiment, a mechanism for driving an on-off valve, an arrangement structure of a bypass passage, and the like are different from those of the first embodiment.

FIG. 4 is a schematic diagram showing an intake system of the engine 11 provided with the emission control device of the present embodiment. In the release suppression device of the present embodiment, the bypass passage 5
2 is an on-off valve 51 in the intake passage 32 as shown in FIG.
Is provided in a portion corresponding to. Bypass passage 52
Is formed so that the air circulation area thereof is not smaller than the air circulation area of the intake passage 32.

Then, the on-off valve 5 after the engine is stopped
When the valve 1 is closed, the air flow area between the on-off valve 51 and the inner surface of the intake passage 32 becomes substantially “0”, and the air flow is permitted only through the bypass passage 52. Is limited to a predetermined value or less (less than the air circulation area of the bypass passage 52). In this state, when the fuel vapor in the intake passage 32 flows toward the upstream of the intake passage 32, the flow of the fuel vapor to the upstream side is opened and the throttle valve 23 and the open / close valve are opened. 51. Therefore, the release of fuel vapor from the upstream end of the intake passage 32 to the outside is suppressed.

In the intake passage 32, an air flow meter 37 for detecting an intake air amount is provided at a position corresponding to the downstream of the bypass passage 52. The air flow meter 37 is provided in place of the vacuum sensor 36 (FIG. 1) of the first embodiment, detects the amount of intake air of the engine 11, and outputs a corresponding detection signal to the ECU 92. When the on-off valve 51 is closed, since the air flow meter 37 is provided near the bypass passage 52, the air passing through the bypass passage 52 also passes through the air flow meter 37.

Next, a structure for driving the on-off valve 51 to open and close will be described. The opening / closing valve 51 is driven not by the motor 54 as in the first embodiment, but by an actuator 71 that operates using a negative pressure generated downstream of the throttle valve 23 in the intake passage 32.

The actuator 71 has a diaphragm 75 made of an elastic body and partitions the housing 72 into an atmosphere chamber 73 and a negative pressure chamber 74, and a rod 76 connecting the diaphragm 75 and the on-off valve 51. . In the actuator 71, the atmosphere chamber 73 is
The negative pressure chamber 74 is open to the outside, and communicates with the vacuum tank 78 via the negative pressure passage 77. The vacuum tank 78 communicates with a downstream side of the throttle valve 23 in the intake passage 32 of the engine 11 via a suction passage 79 provided with a check valve 79a. The check valve 79a is connected to the vacuum tank 7 from the intake passage 32.
The check valve 79a keeps the pressure in the vacuum tank 78 at a value on the vacuum side of the atmospheric pressure.

The vacuum passage 77 is provided with a vacuum switching valve (VSV) 61.
The VSV 61 includes an electromagnetic solenoid (not shown), and is connected to the ECU 92. And ECU
The VSV 61 operates by the 92 controlling the voltage application to the electromagnetic solenoid, so that the negative pressure chamber 74 communicates with the vacuum tank 78 or the atmosphere. Engine 11
When the negative pressure chamber 74 communicates with the vacuum tank 78 by the operation of the VSV 61 during the operation of, air is sucked from the negative pressure chamber 74 based on the negative pressure in the tank 78. As a result, the diaphragm 75 moves against the rod 7 against its own elastic force.
6 is protruded, and the on-off valve 51 is opened based on the protrusion of the rod 76. Also, VSV
When the negative pressure chamber 74 communicates with the atmosphere by the operation of 61, the diaphragm 75 is displaced in a direction in which the rod 76 is immersed by its own elastic force, and the opening and closing valve 51 is closed based on the immersion of the rod 76.

When the engine 11 is stopped, the ECU 92 controls the VSV 61 to close the on-off valve 51, and suppresses the release of fuel vapor from the upstream end of the intake passage 32 to the outside after the engine 11 is stopped. During the operation of the engine 11, the ECU 92 sets the engine speed NE.
To control the open / close state of the on-off valve 51 based on the VSV 61.

That is, the ECU 92 determines the engine speed NE.
For example, when the engine speed is equal to or higher than a predetermined engine speed that is higher than the idle engine speed, the VSV 61 is controlled to open the on-off valve 51, and the intake resistance of the engine 11 caused by the closing of the on-off valve 51 is reduced. When the engine speed NE is low, such as idling, the ECU 92 controls the VSV 61 to close the on-off valve 51 so that the air drawn into the combustion chamber 16 passes through the bypass passage 52. I do.
In this manner, the air passing through the bypass passage 52 also passes through the air flow meter 37 at a position corresponding to the downstream side of the bypass passage 52 in the intake passage 32.

Under the condition that the engine speed NE is constant, the flow velocity of the air passing through the air flow meter 37 is larger than when the on-off valve 51 is opened and the air flow area in the intake system of the engine 11 is large. It becomes higher when the on-off valve 51 is closed and the air circulation area in the intake system of the engine 11 becomes smaller. In the air flow meter 37, the detection accuracy of the amount of intake air tends to be lower when the flow velocity of the air passing therethrough is low than when the flow velocity is high. However, when the flow velocity of the air becomes low such as when the engine is running at a low speed, the on-off valve 51 is closed to reduce the air flow area in the intake system of the engine 11 and the air is
The flow velocity of the air is increased by allowing the air to pass through only the air. Further, the air flow meter 37 is connected to the bypass passage 52.
The air having the increased flow rate as described above passes through the air flow meter 37.
Therefore, even when the engine 11 is running at a low speed, the flow velocity of the air passing through the air flow meter 37 is maintained at a value that can ensure the detection accuracy of the intake air amount.

According to the embodiment described in detail above, the following effects can be obtained. (4) When the fuel vapor present in the intake passage 32 flows toward the upstream side after the engine 11 is stopped, the flow of the fuel vapor toward the upstream side is in a closed state.
3 and the opening / closing valve 51. Therefore, after the engine 11 is stopped, it is possible to suppress the release of the fuel vapor from the upstream end of the intake passage 32 to the outside. Further, during operation of the engine 11, when the engine speed NE is equal to or higher than a predetermined speed higher than the idle speed, the on-off valve 51 is opened. Can be suppressed.

(5) Since the air passage area of the bypass passage 52 is smaller than the air passage area of the intake passage 32, when the fuel vapor in the intake passage 32 flows upstream after the engine 11 is stopped, the fuel vapor is bypassed. It becomes difficult to pass through the passage 52, and the release of fuel vapor from the upstream end of the intake passage 32 to the outside can be suppressed more accurately.

(6) When the engine is running at a low speed, the on-off valve 51 is closed and the air flow meter 37 is connected to the bypass passage 5.
2 at a position corresponding to the downstream of the engine 11.
Even at the time of low rotation, the flow velocity of the air passing through the air flow meter 37 is maintained at a value that can ensure the detection accuracy of the intake air amount. Therefore, the amount of intake air of the engine 11 obtained based on the detection signal from the air flow meter 37 can be made accurate, and various controls based on the amount of intake air can be appropriately performed.

The above embodiments can be modified as follows, for example. In the first embodiment, the opening of the on-off valve 51 during the operation of the engine 11 is adjusted according to the operating state of the engine 11, but such opening adjustment of the on-off valve 51 is not necessarily performed. For example, during operation of the engine 11, the on-off valve 51 may always be fully opened, and the adsorbent 53 may be purified by air passing through the bypass passage 52 while the on-off valve 51 is fully opened.

When the on-off valve 51 is always fully opened during operation of the engine 11 as described above, the on-off valve 51 is
Instead of being driven by 4, the opening / closing valve 51 may be opened / closed by a negative pressure type actuator that is operated using a negative pressure generated in the intake passage 32, for example.
In this case, since the expensive motor 54 does not need to be used, the cost of the emission control device can be reduced.

In the first embodiment, it is not always necessary to provide the adsorbent 53 in the bypass passage 52. Even if the adsorbent 53 is omitted, by closing the on-off valve 51, the air flow area in the intake system of the engine 11 is reduced, and the flow of the fuel vapor flowing in the intake passage 32 toward the upstream side is closed. It is suppressed by both the throttle valve 23 and the on-off valve 51 in the valve state. Therefore, engine 1
After the first stop, the discharge of fuel vapor from the upstream end of the intake passage 32 to the outside can be suppressed.

In the second embodiment, the bypass passage 5
2, an adsorbent may be provided as shown by a two-dot chain line in FIG. In this case, when the engine 11 is stopped, the fuel vapor in the intake passage 32 flows to the upstream side and is adsorbed by the adsorbent 80 when trying to pass through the bypass passage 52. The release of fuel vapor can be more accurately suppressed.

In the second embodiment, it is not always necessary to close the on-off valve 51 when the engine 11 rotates at a low speed. In the second embodiment, the air circulation area of the bypass passage 52 does not necessarily need to be smaller than the air circulation area of the intake passage 32.

In the second embodiment, the opening and closing control of the on-off valve 51 is performed by the first
It may be performed by a motor as in the embodiment. In this case, the opening degree of the on-off valve 51 can be adjusted according to the operating state of the engine 11.

In each of the above embodiments, it is not always necessary to provide the bypass passage 52, and the on-off valve 51 is closed so that the intake passage 3 after the engine 11 is stopped.
The discharge of fuel vapor from the upstream end of the fuel cell 2 to the outside may be suppressed. In this case, when the on-off valve 51 is closed, the air flow area between the on-off valve 51 and the inner surface of the intake passage 32 may be substantially “0”, or may be a predetermined value larger than “0”. You may make it become. When the air flow area is substantially “0”, the on-off valve 51 is closed when the engine is stopped and is opened when the engine is operating. When the air flow area is set to a predetermined value larger than "0", the on-off valve 51 is closed when the engine is stopped and the engine is running at a low speed, and the rotation speed is higher than the low speed. It is possible to open the valve at a number.

In each of the above embodiments, the fuel vapor generated by the fuel leaking from the fuel injection valve 40 is exemplified as the fuel vapor generated in the intake passage 32 when the engine 11 is stopped. The release to the outside is suppressed by the release suppression device. That is, the engine 11
In some cases, a blow-by gas reducing device is provided to return the air-fuel mixture leaking from the combustion chamber 16 into the crankcase to the intake passage. Further, when an evaporative fuel processing device is provided, which once collects fuel vapor generated in a fuel supply system such as a fuel tank and sends out the collected fuel vapor to the intake passage 32 during the operation of the engine 11 for processing. There is also. Then, while the engine 11 is stopped, fuel (fuel vapor) leaks into the intake passage 32 from the blow-by gas reducing device or the evaporated fuel processing device,
Although this may flow toward the upstream side of the intake passage 32, the emission of the fuel vapor to the outside is also suppressed by the emission suppression device.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an overall configuration of an engine to which a release control device according to a first embodiment is applied.

FIG. 2 is a graph showing a change in a total amount of fuel leakage from a fuel injection valve with a lapse of time immediately after an engine stop.

FIG. 3 is a graph showing a change in the concentration of fuel vapor in an intake passage with the lapse of time immediately after an engine stop.

FIG. 4 is a schematic diagram showing an intake system of an engine to which the emission control device of the second embodiment is applied.

[Explanation of symbols]

11 ... engine, 14 c ... crank position sensor,
32 ... intake passage, 36 ... vacuum sensor, 44 ... throttle position sensor, 51 ... open / close valve, 52 ... bypass passage, 53 ... adsorbent, 54 ... motor, 61 ... vacuum switching valve (VSV), 71 ... actuator, 77 ... Negative pressure passage, 78 ... Vacuum tank, 79 ...
Suction passage, 79a ... check valve, 80 ... adsorbent, 92 ...
Electronic control unit (ECU).

Claims (5)

[Claims] 1. A fuel vapor emission suppression device for suppressing the emission of fuel vapor present in an intake system of an internal combustion engine to the outside when the internal combustion engine is stopped, comprising: a throttle valve of the engine in an intake passage of the internal combustion engine; In addition, a fuel vapor emission suppression device is provided with an on-off valve that closes when the engine is stopped and opens at least when the engine is running at a high engine speed. 2. The fuel vapor emission suppression device according to claim 1, wherein the on-off valve limits an air flow area in an intake system of the internal combustion engine to a predetermined value or less when the valve is closed. An apparatus for suppressing fuel vapor emission, comprising an adsorbent for adsorbing fuel vapor on an air flow path when the on-off valve is closed. 3. The fuel vapor emission control device according to claim 2, wherein the on-off valve has an air flow area in the intake passage substantially “0” when the on-off valve is closed. A fuel vapor emission suppression device, wherein a bypass passage bypassing the on-off valve and including the adsorbent is provided in an intake system. 4. The fuel vapor emission control device according to claim 1, wherein the on-off valve has an air flow area in the intake passage substantially “0” when the on-off valve is closed. A fuel vapor emission suppression device, wherein a bypass passage bypassing the on-off valve is provided in an intake system, and an air circulation area of the bypass passage is smaller than an air circulation area of the intake passage. 5. The fuel vapor emission suppression device according to claim 3, further comprising an opening control means for controlling an opening of the on-off valve based on an engine operating state during operation of the internal combustion engine. Fuel vapor emission suppression device.