JP3444006B2 - Evaporative fuel treatment system for internal combustion engine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel vapor treatment system for an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, in an internal combustion engine of an automobile or the like, fuel is sent from a fuel tank to a fuel injection device of the internal combustion engine by a fuel pump and then supplied to the internal combustion engine through a fuel injection valve of the fuel injection device. ing. here,
When the operating state of the internal combustion engine is low, such as when idling, the surplus fuel of the fuel sent by the fuel pump is sent back to the fuel tank. The excess fuel receives heat from a high temperature place such as a cylinder head around the pipe while flowing in the pipe, and the temperature of the fuel may rise by the time of returning to the fuel tank. Also,
If the outside air temperature is high while the engine is stopped, the fuel temperature may rise due to heating of the fuel tank. When the fuel temperature in the fuel tank rises, the pressure in the fuel tank rises due to the evaporated fuel in the fuel tank, which may deform the fuel tank. Therefore, an internal combustion engine mounted on an automobile or the like discharges evaporated fuel to the outside of the fuel tank so as to reduce the pressure inside the fuel tank.

However, if the vaporized fuel having a high concentration is directly exposed to the atmosphere, there is a problem that it gives off an offensive odor.
In a conventional automobile, the vaporized fuel is trapped in activated carbon as an adsorption layer to prevent the vaporized fuel from being directly exposed to the atmosphere. Then, by circulating air through the activated carbon, the evaporated fuel adsorbed by the activated carbon is separated, and this evaporated fuel is purged together with air into the intake passage of the internal combustion engine, and burned together with the injected fuel in the combustion chamber to change the evaporated fuel. I'm trying to handle it.
An example of this type of evaporated fuel processing device for an internal combustion engine is disclosed in JP-A-61-53451. In this evaporated fuel processing device, all the evaporated fuel introduced from the fuel tank is always passed through the activated carbon to temporarily adsorb a large amount of the evaporated fuel generated in the fuel tank to the activated carbon. The intake passage is prevented from being purged. as a result,
The fluctuation of the air-fuel ratio that occurs when the purging action is performed is made as small as possible.

[0004]

However, the activated carbon conventionally used as an adsorbent for adsorbing the vaporized fuel gradually deteriorates when the adsorption and desorption of the vaporized fuel are repeated. Therefore, when a large amount of evaporated fuel introduced from the fuel tank is always passed through the activated carbon as in the above-described evaporated fuel processing device, the activated carbon is severely deteriorated. If the activated carbon deteriorates, it will not be adsorbed by the evaporated fuel activated carbon but will be directly purged into the intake passage of the internal combustion engine. Is started,
As a result, the air-fuel ratio is greatly affected by fluctuations in the amount of evaporated fuel purged in the intake passage, causing a problem of roughening.

According to the present invention, the vaporized fuel purged in the intake passage is made variable by varying the capacity of the adsorption layer interposed between the fuel tank and the intake passage in accordance with the amount of vaporized fuel introduced from the fuel tank to the adsorption layer. The purpose of the present invention is to reduce the deterioration of the adsorption layer while preventing the amount from changing rapidly.

[0006]

To achieve the above object, according to the present invention, an adsorption layer for temporarily storing evaporated fuel is interposed between a fuel tank and an engine intake passage, and evaporation in the adsorption layer is performed. In an evaporative fuel treatment system for an internal combustion engine in which fuel is purged into an engine intake passage, the engine is operated from the adsorption layer.
During the purging process where the evaporated fuel is purged into the intake passage ,
Adsorption layer capacity changing means for increasing the capacity of the adsorption layer interposed between the fuel tank and the engine intake passage is provided when the amount of evaporated fuel introduced from the fuel tank to the adsorption layer is large compared to when it is small. Further, according to the present invention, an evaporated fuel control valve for controlling the amount of evaporated fuel guided from the fuel tank to the adsorption layer is provided between the fuel tank and the adsorption layer, and the evaporated fuel control valve is a control valve whose valve opening pressure is variable. The valve opening pressure of the evaporated fuel control valve is increased as the amount of evaporated fuel that is formed from the fuel tank to the adsorption layer increases. Further, according to the present invention, the internal combustion engine is provided with the intake air amount detecting means for detecting the intake air amount, and when the intake air amount detected by the intake air amount detecting means is high, the fuel consumption is low compared to when the intake air amount is low. The capacity of the adsorption layer interposed between the tank and the engine intake passage is reduced. Further, according to the present invention, the internal combustion engine is provided with the fuel injection action stopping means for temporarily stopping the fuel injection action according to the engine operating state, and the vapor diffusion provided between the adsorption layer and the engine intake passage is provided. The chamber is connected to the engine intake passage via the purge control valve, and when the fuel injection action is stopped by the fuel injection action stopping means, the purge action is stopped by closing the purge control valve, and the fuel injection action is stopped. Accordingly, when the purging action is stopped, the capacity of the adsorption layer interposed between the fuel tank and the vapor diffusion chamber is made larger than when the purging action is performed.

[0007]

According to the first aspect of the invention, the capacity of the adsorption layer between the fuel tank and the intake passage is increased as the amount of evaporated fuel flowing into the adsorption layer increases. As a result, the evaporated fuel is temporarily adsorbed in the adsorption layer and then gradually purged into the intake passage, so that the amount of evaporated fuel purged into the intake passage is prevented from fluctuating rapidly. On the other hand, if the amount of evaporated fuel flowing into the adsorption layer decreases, the capacity of the adsorption layer between the fuel tank and the intake passage is reduced. As a result, the adsorption / desorption action of the evaporated fuel in the adsorption layer is reduced, so that the deterioration of the adsorption layer is reduced. According to the second aspect of the present invention, the pressure in the fuel tank approaches the saturated vapor pressure of the fuel by increasing the valve opening pressure of the fuel vapor control valve and thereby increasing the pressure in the fuel tank. As a result, further generation of evaporated fuel in the fuel tank is suppressed. On the other hand, when the intake air amount is large, the air-fuel ratio is unlikely to change even if the amount of evaporated fuel purged by the engine changes. Therefore, in the invention described in claim 3, when the intake air amount is large, the capacity of the adsorption layer between the fuel tank and the intake passage is made small so that the evaporated fuel is not guided to the adsorption layer as much as possible and the adsorption layer is deteriorated. Is being reduced. Further, in the invention described in claim 4, since the capacity of the adsorption layer between the fuel tank and the intake passage is increased when the purging action is stopped due to the stop of the fuel injection action, the vapor diffusion chamber during the purging action is stopped. A large amount of vaporized fuel is prevented from flowing into. Therefore, when the purging operation is restarted, a large amount of evaporated fuel is prevented from being purged from the vapor diffusion chamber into the intake passage.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows a first embodiment of an evaporated fuel processing apparatus for an internal combustion engine of the present invention. Referring to FIG. 1, an intake passage 1a and an exhaust passage 1b are connected to the engine body 1, and a throttle valve 1c is arranged in the intake passage 1a. A canister 15 is interposed between the intake passage 1a downstream of the throttle valve 1c and the fuel tank 16. Intake passage 1a
And the canister 15 are connected by a purge passage 3 ',
The canister 15 and the fuel tank 16 are connected by a vapor passage 18. A purge control valve 2 for controlling the flow rate of the purge gas flowing in the purge passage 3'is provided in the purge passage 3 '. The purge control valve 2 is controlled based on the output signal from the electronic control unit shown in FIG. 9, for example. The canister 15 includes an adsorption layer 4'holding an adsorbent 4 made of activated carbon, a vapor diffusion chamber 3 formed on one side of the adsorption layer 4 ', and an atmosphere chamber 5 formed on the other side of the adsorption layer 4'. And an atmosphere communicating hole 9 communicating with the atmosphere. The atmosphere chamber 5 and the atmosphere communicating hole 9 are connected to each other via a buffer 17 provided in the canister 15.
The buffer 17 is provided with an adsorbent 6 made of activated carbon so that the vaporized fuel that has reached the atmosphere chamber 5 without being adsorbed in the adsorbent 4 while the purging action is stopped is not released into the atmosphere. ing.

Still referring to FIG. 1, the canister 15
Is a first vapor chamber 14 connected to each other via a diaphragm 11.
And a second vapor chamber 14 '. First vapor room 14
Is connected to the fuel tank 16 via the vapor passage 18 on the one hand, and the adsorption layer 4 ′ via the first pressure control valve 12 and the vapor guide 8 which are evaporative fuel control valves on the other hand.
It is connected to the. The first pressure control valve 12 is the spring 1
It is urged in the valve closing direction by 2c. The end portion 7 of the vapor guide 8 located on the side opposite to the first pressure control valve 12 is arranged in the substantially central portion of the adsorption layer 4 '. On the other hand, the second vapor chamber 14 'is connected to the vapor diffusion chamber 3 via the second pressure control valve 10 which is an evaporated fuel control valve. The second pressure control valve 10 is biased in the valve closing direction by a spring 10c. In the example shown in FIG. 1, the valve opening pressure of the first pressure control valve 12 is set higher than the valve opening pressure of the second pressure control valve 10. A back purge control valve 13 that can flow from the vapor diffusion chamber 3 to the first vapor chamber 14 is provided between the first vapor chamber 14 and the vapor diffusion chamber 3. The back purge control valve 13 opens when the pressure inside the first vapor chamber 14 becomes lower than the pressure inside the vapor diffusion chamber 3.

When the purge control valve 2 is opened, the negative pressure in the intake passage 1a downstream of the throttle valve 1c causes air to flow in the canister 15. That is, air first flows into the buffer 17 through the atmosphere communication hole 9, then flows into the atmosphere chamber 5, and then flows into the adsorption layer 4 ′. The air flowing into the adsorption layer 4'desorbs the evaporated fuel adsorbed in the adsorption layer 4 '. These evaporated fuel and air, that is, the purge gas, then flow into the vapor diffusion chamber 3 and are supplied into the intake passage 1a via the purge passage 3'and the purge control valve 2, thus performing the purge action.

On the other hand, the evaporated fuel generated in the fuel tank 16 during the purging action passes through the vapor passage 18 and the canister 1
5 enters the first vapor room 14. And the first vapor room 1
Since the No. 4 and the second vapor chamber 14 'are communicated with each other through the throttle 11, the evaporated fuel is also sent to the second vapor chamber 14'. Here, when the pressure in the second vapor chamber 14 'reaches the opening pressure of the second pressure control valve 10 set by the spring 10c, the diaphragm 10a is displaced and the second pressure control valve 10 is opened. After that, the evaporated fuel in the second vapor chamber 14 'flows into the vapor diffusion chamber 3. In this case, the opening pressure of the first pressure control valve 12 is set to be higher than the opening pressure of the second pressure control valve 10. Therefore, if the pressure in the first vapor chamber 14 is not so high, the first pressure control is performed. The valve 12 is kept closed. As a result, when the pressure in the first vapor chamber 14 is low, that is, from the fuel tank 16 to the canister 1
When the amount of evaporated fuel introduced into the fuel cell 5 is small, the evaporated fuel is purged into the intake passage 1a without passing through the adsorption layer 4 '. In other words, from the fuel tank 16 to the canister 1
When the amount of evaporated fuel introduced into the fuel cell 5 is small, the capacity of the adsorption layer 4'intervened between the fuel tank 16 and the intake passage 1a is zero. Therefore, when the amount of the evaporated fuel guided to the canister 15 is small, the evaporated fuel is not adsorbed in the adsorption layer 4 ', and thus the deterioration of the adsorption layer 4'can be reduced.

When the amount of evaporated fuel introduced from the fuel tank 16 into the canister 15 is small, the fluctuation of the amount of evaporated fuel purged into the intake passage 1a has little effect on the air-fuel ratio. Therefore, in this case, the air-fuel ratio is prevented from becoming rough. The first vapor chamber 14 and the second vapor chamber 1
4'communicates with each other through the throttle 11, that is, the throttle 11 serves as a resistance to the flow of the evaporated fuel, so that when the second pressure control valve 10 is opened, a large amount is supplied via the second pressure control valve 10. Evaporative fuel does not flow. Further, the evaporated fuel flowing from the second pressure control valve 10 into the vapor diffusion chamber 3 is guided to a position farthest from the purge passage 3 ′ in the vapor diffusion chamber 3. As a result, the evaporated fuel flowing into the vapor diffusion chamber 3 via the second pressure control valve 10 can be mixed well with the air flowing into the vapor diffusion chamber 3 through the adsorption layer 4 '. Therefore, a region where the evaporated fuel concentration is too high is not formed in the intake air.

When the amount of evaporated fuel generated in the fuel tank 16 is large and the pressure in the first vapor chamber 14 reaches the opening pressure of the first pressure control valve 12 set by the spring 12c, the diaphragm 12a is displaced. The first pressure control valve 12 is opened. Then, the evaporated fuel is passed from the first vapor chamber 14 to the central portion of the adsorption layer 4'through the end portion 7 of the vapor guide 8 and then adsorbed by the adsorption layer 4 '. Adsorption layer 4 '
The evaporated fuel adsorbed therein is gradually separated by the air flowing in the adsorption layer 4 ', and then purged in the intake passage 1a. At this time, the fuel tank 16 and the intake passage 1
The adsorption layer 4 ′ interposed between a is the end 7 of the vapor guide 8.
Therefore, the capacity of the adsorption layer 4'located between the fuel tank 16 and the intake passage 1a is almost half of the total capacity of the adsorption layer 4 '. That is, when the amount of evaporated fuel introduced from the fuel tank 16 into the canister 15 is large, the capacity of the adsorption layer 4 ′ interposed between the fuel tank 16 and the intake passage 1a is increased. As described above, the evaporated fuel introduced into the adsorption layer 4'is temporarily adsorbed in the adsorption layer 4'and then gradually purged into the intake passage 1a. Therefore, by increasing the capacity of the adsorption layer 4'interposed between the fuel tank 16 and the intake passage 1a, it is possible to prevent the amount of evaporated fuel purged in the intake passage 1a from suddenly changing. Moreover, since the evaporated fuel is temporarily adsorbed by the adsorption layer 4'and then purged into the intake passage 1a, the intake passage 1a
Fluctuations in the amount of evaporated fuel purged inside can be reduced. Thus, it is possible to prevent the air-fuel ratio from becoming rough when the purging action is performed.

In this embodiment, the first pressure control valve 12 is fixed to the diaphragm 12a which separates the first vapor chamber 14 and the diaphragm chamber 12b from each other, and the second pressure control valve 1
0 is fixed to the diaphragm 10a which separates the second vapor chamber 14 'and the diaphragm chamber 10b from each other. In this case, since the diaphragm chambers 12b and 10b are open to the atmosphere, the valve opening pressures of the first and second pressure control valves 12 and 10 are hardly influenced by the engine operating state. Therefore, the opening / closing valve operation of the first and second pressure control valves can be performed regardless of the engine operating state. The intake passage 1a
The amount of fuel vapor to be purged inside is controlled by controlling the purge control valve 2. In this embodiment, the adsorption layer capacity varying means corresponds to the first pressure control valve 12, the second pressure control valve 10, the springs 12c and 10c, and the vapor guide 8.

FIG. 2 shows an outline of the amount of evaporated fuel generated (≈fuel temperature) and the pressure in the fuel tank 16. Figure 2
In the region where the amount of generated evaporated fuel is small as shown by point a, the valve opening pressure is controlled to be constant by the second pressure control valve 10 and the amount of generated evaporated fuel is more than point b. In this case, the valve opening pressure is controlled by the first pressure control valve 12.
That is, the evaporated fuel generated in the fuel tank 16 directly flows out to the vapor diffusion chamber 3 in the region where the amount of evaporated fuel generated up to point a is small, and passes through the vapor guide 8 in the region where the amount of evaporated fuel generated above point b is large. It flows out from the central portion of the adsorption chamber 4 '.

When the amount of evaporated fuel introduced from the fuel tank 16 into the canister 15 increases, the pressure inside the first and second vapor chambers 14 and 14 'rises. Therefore, opening and closing the first and second pressure control valves 12 and 10 in accordance with the pressures in the first and second vapor chambers 14 and 14 'as in the present embodiment is performed from the fuel tank 16 to the canister 15 inside. The capacity of the adsorption layer 4'between the fuel tank 16 and the intake passage 1a is changed in accordance with the amount of evaporated fuel introduced to.

By the way, the amount of evaporated fuel introduced from the fuel tank 16 to the canister 15 when the engine is stopped is relatively small. Therefore, the first pressure control valve 12 does not open when the engine is stopped. Therefore, the evaporated fuel guided to the canister 15 when the engine is stopped flows into the vapor diffusion chamber 3 via the second pressure control valve 10. That is, the vaporized fuel guided to the canister 15 is not guided to the central portion of the adsorption layer 4'through the first pressure control valve 12 and the vapor guide 8 but to the end portion of the adsorption layer 4 '. In this case, the purge control valve 2 is closed, and the evaporated fuel that has flowed into the vapor diffusion chamber 3 is then adsorbed on almost the entire adsorption layer 4 '. Therefore, the adsorption layer 4'can be effectively used to adsorb the evaporated fuel when the engine is stopped.

FIG. 3 shows a second embodiment of the present invention. In this example, the first pressure control valve 12 in the first embodiment described above is used.
Instead of the above, a check valve 22 is provided at the end 7 of the vapor guide 8. The check valve 22 can flow only from the first vapor chamber 14 toward the adsorption layer 4 '. The valve opening pressure of the check valve 22 is set higher than the valve opening pressure of the second pressure control valve 10.

The vaporized fuel generated in the fuel tank 16 during the purging action flows into the first vapor chamber 14 and the second vapor chamber 14 'through the vapor passage 18. Here, when the pressure in the second vapor chamber 14 'reaches the opening pressure of the second pressure control valve 10 set by the spring 10c, the diaphragm 10a is displaced and the second pressure control valve 10 is opened. After that, the evaporated fuel in the second vapor chamber 14 'flows into the vapor diffusion chamber 3. In this case, the valve opening pressure of the check valve 22 is set higher than the valve opening pressure of the second pressure control valve 10,
Therefore, if the pressure in the first vapor chamber 14 is not so high, the check valve 22 is kept closed. As a result, when the pressure in the first vapor chamber 14 is low, that is, when the amount of evaporated fuel introduced from the fuel tank 16 into the canister 15 is small, the evaporated fuel is purged into the intake passage 1a without passing through the adsorption layer 4 '. It In other words, when the amount of evaporated fuel introduced from the fuel tank 16 into the canister 15 is small, the capacity of the adsorption layer 4 ′ interposed between the fuel tank 16 and the intake passage 1a becomes zero. Therefore, when the amount of the evaporated fuel guided to the canister 15 is small, the evaporated fuel is not adsorbed in the adsorption layer 4 ', and thus the deterioration of the adsorption layer 4'can be reduced.

When the amount of vaporized fuel generated in the fuel tank 16 is large and the pressure in the first vapor chamber 14 reaches the valve opening pressure of the check valve 22 set by the spring 22c, the check valve 22 is opened. Then, the evaporated fuel is passed from the first vapor chamber 14 to the central portion of the adsorption layer 4'through the end portion 7 of the vapor guide 8 and then adsorbed by the adsorption layer 4 '. The vaporized fuel adsorbed in the adsorption layer 4'is gradually separated by the air flowing in the adsorption layer 4 ', and then purged in the intake passage 1a. At this time, the fuel tank 1
The adsorption layer 4'interposed between the fuel tank 16 and the intake passage 1a is an adsorption layer 4'located substantially above the end 7 of the vapor guide 8, and therefore the adsorption layer interposed between the fuel tank 16 and the intake passage 1a. The capacity of 4'is approximately half the total capacity of the adsorption layer 4 '. That is, when the amount of evaporated fuel introduced from the fuel tank 16 into the canister 15 is large, the capacity of the adsorption layer 4 ′ interposed between the fuel tank 16 and the intake passage 1a is increased. As a result, it is possible to prevent the amount of evaporated fuel purged in the intake passage 1a from changing rapidly. Moreover, a large amount of evaporated fuel can be prevented from being purged into the intake passage 1a by temporarily adsorbing the evaporated fuel to the adsorption layer 4'and then purging into the intake passage 1a. Therefore, it is possible to prevent the air-fuel ratio from becoming rough when the purging action is performed.

When the check valve 22 is used in this manner, the structure is simple and the cost is relatively low. On the other hand, check valve 22
Is placed inside the adsorption layer 4 ′, the negative pressure in the adsorption layer 4 ′ acts on the check valve 22. That is, when the negative pressure in the adsorption layer 4'becomes large, the first vapor chamber 1
The check valve 22 can open even when the pressure in 4 is low. Therefore, as the negative pressure in the adsorption layer 4 ′, that is, the negative pressure in the intake passage 1 a, increases, the amount of evaporated fuel flowing into the adsorption layer 4 ′ via the check valve 22 can increase. However, if the negative pressure in the adsorption layer 4 ′ increases, the amount of air introduced into the adsorption layer 4 ′ via the atmosphere communication hole 9 also increases.
Therefore, the concentration of the evaporated fuel in the purge gas purged into the intake passage 1a is prevented from increasing. Thus, it is possible to prevent the air-fuel ratio from becoming rough.

Furthermore, by setting the valve opening pressure of the check valve 22 according to the negative pressure in the intake passage 1a,
The evaporated fuel in the fuel tank 16 can be positively released to the outside of the fuel tank 16. Therefore, there is an effect that the pressure in the fuel tank 16 is always kept low. The rest of the configuration and operation of the evaporated fuel processing device are the same as those of the first embodiment, so a description thereof will be omitted here.

FIGS. 4A and 4B show a third embodiment of the present invention. Referring to FIG. 4A, in this embodiment, a single vapor chamber 34 connected to the fuel tank 16 is provided. This vapor chamber 34 is provided on the one hand with the second pressure control valve 1
0 and a switching valve 30 which can be displaced integrally with the second pressure control valve 10 are connected to the vapor diffusion chamber 3, and on the other hand, the adsorption layer 4 ′ is connected via the vapor guide 8 and the check valve 22.
Connected to. Further, in the connecting pipe 30a connecting the vapor chamber 34 and the vapor diffusion chamber 3, there is provided a throttle 31 which serves as a flow path resistance of the evaporated fuel flowing in the connecting pipe 30a.

When the pressure in the vapor chamber 34 is relatively low, the second pressure control valve 10 is closed by abutting the upper end of the connecting pipe 30a, and the check valve 22 is also closed. When the second pressure control valve 10 is in contact with the upper end of the connecting pipe 30a, the switching valve 30 is separated from the lower end of the connecting pipe 30a. When the amount of evaporated fuel flowing from the fuel tank 16 into the vapor chamber 34 increases and the pressure in the vapor chamber 34 rises, and the opening pressure of the second pressure control valve 10 set by the spring 10c is reached, the diaphragm 10a is displaced. The second pressure control valve 10 is connected to the connecting pipe 30a.
From the upper end of the second pressure control valve 1
0 is opened. On the other hand, at this time, if the pressure in the vapor chamber 34 is relatively low, the switching valve 30 is held in a state of being separated from the lower end of the connecting pipe 30a. Therefore, the vapor chamber 34
The vaporized fuel therein flows into the vapor diffusion chamber 3 via the second pressure control valve 10 and the switching valve 30. In this case, if the pressure in the vapor chamber 34 is not so high, the check valve 2
2 is kept closed. As a result, when the pressure in the vapor chamber 34 is low, that is, when the amount of evaporated fuel introduced from the fuel tank 16 into the canister 15 is small, the evaporated fuel is purged into the intake passage 1a without passing through the adsorption layer 4 '. Become.

When the pressure in the vapor chamber 34 further rises and the second pressure control valve 10 is displaced further upward, the switching valve 30
Will rise further. Next, when the pressure in the vapor chamber 34 rises to the valve opening pressure of the check valve 22, the switching valve 30 is brought into contact with the lower end of the connecting pipe 30a as shown in FIG. The communication between the chamber 34 and the vapor diffusion chamber 3 is cut off. Therefore, in this case, all the evaporated fuel in the vapor chamber 34 is guided into the adsorption layer 4 ′ via the vapor guide 8 and the check valve 22 and adsorbed to the adsorbent 4.

In this embodiment, when the check valve 22 is opened and the fuel vapor in the vapor chamber 34 is being introduced into the adsorption layer 4 ', the switching valve 30 shuts off the connecting pipe 30a. At this time, from the vapor chamber 34 to the connecting pipe 30a
The vaporized fuel is prevented from flowing into the vapor diffusion chamber 3 via the. That is, a large amount of evaporated fuel is introduced from the fuel tank 16 into the canister 15, and as a result, the evaporated fuel is purged into the intake passage 1a via the vapor diffusion chamber 3 when the check valve 22 is open. Be blocked.
Therefore, when the amount of evaporated fuel introduced from the fuel tank 16 into the canister 15 is large, all the evaporated fuel in the vapor chamber 34 is adsorbed in the adsorption layer 4 '. As a result, the amount of evaporated fuel purged into the intake passage 1a is prevented from changing suddenly, and thus the air-fuel ratio is prevented from becoming rough. In the present embodiment, the adsorption layer capacity varying means is the second pressure control valve 10, the switching valve 30, the check valve 22, the springs 10c and 22c, and the vapor guide 8.
Equivalent to. The rest of the configuration and operation of the evaporated fuel processing device are the same as in the second embodiment, so a description thereof will be omitted here.

FIG. 5 shows a fourth embodiment of the present invention. In the example shown in FIG. 5, the evaporative fuel control valve is composed of a single pressure control valve 40, and the single vapor chamber 34 is placed in the vapor diffusion chamber 3 or the adsorption layer 4 ′ via the pressure control valve 40 and the vapor guide 48. Connected selectively. The vapor guide 48 is connected to the wall portion 42 that is fixed in the vapor chamber 34, and is fixed at this position. See also Vapor Guide 4
8 is also connected to a diaphragm 46 that defines a vapor chamber 34. Further, the vapor guide 48 between the wall portion 42 and the diaphragm 46 is provided with a stretchable bellows portion 41. On the other hand, in the vapor diffusion chamber 3 and the adsorption layer 4 ', the vapor guide 48 is slidably supported in the support tube 45 fixed in the adsorption layer 4'.

A discharge hole 45c is provided in the support pipe 45 located in the vapor diffusion chamber 3, and a communication hole 47 is provided in the vapor guide 48 located below the diaphragm 46.
Are provided, and the discharge hole 45c and the communication hole 47 can communicate with each other. Further, the discharge hole 45b is also provided in the support tube 45 located substantially in the center of the adsorption layer 4 '. Further, for example, a pair of discharge holes 45a is provided in the peripheral wall of the support pipe 45 between the discharge hole 45b and the vapor diffusion chamber 3. In the example shown in FIG. 5, the emission hole 45a is provided at a position at a height of about one third from the upper end of the adsorption layer 4 '. Further, the flow path resistance of the discharge hole 45a is made larger than that of the discharge hole 45c, and the flow path resistance of the discharge hole 45b is set to the discharge hole 45a.
Has been made larger than that. In addition, in FIG.
0a is a diaphragm connected to the pressure control valve 40,
Reference numeral b denotes a diaphragm chamber that communicates with the atmosphere, and reference numeral 40c denotes a spring that biases the pressure control valve 40 in the valve closing direction.

When the pressure in the vapor chamber 34 rises and the pressure control valve 40 opens, the displacement amount of the diaphragm 46 is relatively small unless the pressure in the vapor chamber 34 is so high. The hole 47 and the discharge hole 45c of the support tube 45 communicate with each other. As a result, most of the evaporated fuel in the vapor chamber 34 flows into the vapor diffusion chamber 3 via the communication hole 47 and the discharge hole 45c. Other vaporized fuel is discharged through the discharge holes 45a and 45b.
Flow into the adsorption layer 4'through.

When the pressure in the vapor chamber 34 further rises, the amount of displacement of the diaphragm 46 increases, whereby the vapor guide 48 is extended in the bellows portion 41 and displaced downward in the figure. As a result, FIG.
As shown in (A), the communication hole 47 of the vapor guide 48 is blocked by the wall surface of the support tube 45, and the discharge hole 4 of the support tube 45 is formed.
5c is blocked by the wall surface of the vapor guide 48. Therefore, in this case, most of the evaporated fuel in the vapor chamber 34 is discharged into the adsorption layer 4 ′ from the discharge hole 45 a of the support pipe 45.

When the pressure in the vapor chamber 34 further rises, the diaphragm 46 is further displaced and the vapor guide 48 is further displaced downward. As a result, FIG. 6 (B)
As shown in FIG. 5, the communication hole 47 of the vapor guide 48 and the discharge hole 45 c of the support tube 45 are blocked, while the discharge hole 45 a of the support tube 45 is blocked by the wall surface of the vapor guide 48.
Therefore, in this case, all the evaporated fuel in the vapor chamber 34 is discharged into the adsorption layer 4'from the discharge hole 45b of the support pipe 45.

According to this embodiment, when the pressure in the vapor chamber 34 is relatively low, that is, when the amount of evaporated fuel introduced from the fuel tank 16 into the canister 15 is relatively small, the evaporated fuel in the vapor chamber 34 is mainly It is discharged into the vapor diffusion chamber 3 through the communication hole 47 and the discharge hole 45c. Therefore, in this case, the fuel tank 16 and the intake passage 1
Therefore, the capacity of the adsorption layer 4'between a and n is almost zero.
When the pressure in the vapor chamber 34 rises, the vapor chamber 34
The vaporized fuel inside is discharged into the adsorption layer 4 ′ mainly through the discharge holes 45 a. Therefore, in this case, the adsorption layer 4 ′ interposed between the fuel tank 16 and the intake passage 1a is the adsorption layer 4 ′ between the discharge hole 45a and the vapor diffusion chamber 3, that is, the adsorption layer between the fuel tank 16 and the intake passage 1a. The capacity of 4'is about one-third of the total capacity.

When the pressure in the vapor chamber 34 further rises, the evaporated fuel in the vapor chamber 34 is released into the adsorption layer 4'through the release holes 45b. Therefore, in this case, the adsorption layer 4'disposed between the fuel tank 16 and the intake passage 1a.
Is an adsorption layer 4'between the discharge hole 45b and the vapor diffusion chamber 3, that is, the capacity of the adsorption layer 4'between the fuel tank 16 and the intake passage 1a is about half of the total capacity. Therefore, when the amount of evaporated fuel introduced from the fuel tank 16 into the canister 15 is large, the capacity of the adsorption layer 4'between the fuel tank 16 and the intake passage 1a is increased compared to when the amount is small. As a result, the deterioration of the adsorption layer 4'can be reduced while preventing the amount of evaporated fuel purged in the intake passage 1a from changing rapidly. In this embodiment, the adsorption layer capacity varying means corresponds to the diaphragm 46, the support tube 45, the discharge holes 45a, 45b, 45c, the vapor guide 48, the bellows portion 41, and the communication hole 47. The other structure and operation of the evaporated fuel processing device are the same as those of the first embodiment, and therefore the description thereof is omitted here.

FIG. 7 shows a fifth embodiment of the present invention. In this embodiment, the discharge hole 45a provided in the peripheral wall of the support pipe 45 of the fourth embodiment is opened only toward the purge passage 3, and the other configurations are the same as those of the fourth embodiment. . In the present embodiment, when the pressure in the vapor chamber 34 rises and the vapor guide 48 is displaced downward, and thereby the communication hole 47 of the vapor guide 48 and the discharge hole 45c of the support pipe 45 are blocked, the vapor chamber 34 inside the vapor chamber 34 is blocked. The evaporated fuel is discharged into the adsorption layer 4'from the discharge hole 45a of the support pipe 45.
At this time, since the discharge hole 45a is opened only toward the purge passage 3 ', the evaporated fuel discharged from the discharge hole 45a is adsorbed in the adsorption layer 4'located between the discharge hole 45a and the purge passage 3'. It In other words, the vapor guide 48
The adsorption layer 4'located on the opposite side of the purge passage 3'with respect to
The vaporized fuel discharged from the discharge hole 45a is not guided to. That is, in the evaporative fuel treatment control system of the present embodiment, the use range of the adsorption chamber 4'is more positively changed as compared with that of the fourth embodiment, so that the use range of the adsorption layer 4'is made as multi-stage as possible. To do. Therefore, the deterioration of the adsorption layer 4'is further suppressed. In this embodiment, the adsorption layer capacity varying means is the diaphragm 46.
A support tube 45, discharge holes 45a, 45b, 45c,
It corresponds to the vapor guide 48, the bellows portion 41, and the communication hole 47.

FIG. 8 shows a sixth embodiment of the present invention. This is an embodiment of the evaporated fuel processing apparatus for an internal combustion engine according to claim 2 of the present invention. In the evaporated fuel processing device of the sixth embodiment, as in the first embodiment, the first and second vapor chambers 14,
14 'is provided, the first pressure control valve 12 is arranged in the first vapor chamber 14, and the second pressure control valve 10 is arranged in the second vapor chamber 14'. The first pressure control valve 12 of the spring 12c for controlling the opening pressure of the first pressure control valve 12
The opposite end is fixed to the diaphragm 62d. Similarly, the end of the spring 10c that controls the opening pressure of the second pressure control valve 10 on the side opposite to the second pressure control valve 10 is fixed to the diaphragm 60d. As can be seen in FIG. 8, the diaphragm 62d defines a first back pressure chamber 62b and the diaphragm 60d defines a second back pressure chamber 60b. The first back pressure chamber 62b and the second back pressure chamber 60b are in communication with each other, and the first back pressure chamber 62b is in communication with the first vapor chamber 14 via the communication passage 69. Furthermore, FIG.
Referring to, the diaphragm chamber 1 of the first pressure control valve 12
A stopper 66 for limiting the displacement of the diaphragm 62d is provided in the 2b. In addition, the diaphragm chambers 12b, 1
Both 0b are open to the atmosphere. The other structure of the evaporated fuel processing device is the same as that of the first embodiment, and therefore its explanation is omitted.

When the pressure in the first and second vapor chambers 14 and 14 'rises to the opening pressure of the second pressure control valve 10, the second pressure control valve 10 is opened and the second vapor chamber 14' is opened. The vaporized fuel inside is flowed into the vapor diffusion chamber 3. When the pressure in the first and second vapor chambers 14 and 14 'further rises to the opening pressure of the first pressure control valve 12, the first pressure control valve 12
Is opened and the evaporated fuel in the first vapor chamber 14 is guided to almost the central portion of the adsorption layer 4 ′ via the vapor guide 8. In this case, as the pressure inside the first and second vapor chambers 14 and 14 'rises, the first and second back pressure chambers 62b and 60b.
The pressure inside also rises. For example, when the pressure in the first back pressure chamber 62b rises, the diaphragm 62d is urged downward, thereby increasing the valve opening pressure of the first pressure control valve 12. Therefore, the higher the pressure in the first and second vapor chambers 14 and 14 ', that is, the larger the amount of evaporated fuel introduced from the fuel tank 16 to the canister 15, the greater the pressure of the first and second pressure control valves 12 and 10. The valve opening pressure will be increased. As a result, the pressure in the fuel tank 16 can easily approach the saturated vapor pressure of the fuel. When the pressure in the fuel tank 16 approaches the saturated vapor pressure of the fuel, the vaporizing action of the fuel is reduced, and as a result, the amount of vaporized fuel guided from the fuel tank 16 to the canister 15 is reduced. For this reason, the amount of evaporated fuel that can be introduced into the adsorption layer 4'is reduced, so that a large amount of evaporated fuel is prevented from being purged in the intake passage 1a. As a result, the evaporated fuel concentration in the purge gas can be kept low, and therefore, the fluctuation of the evaporated fuel concentration in the purge gas or the intake air can be reduced, and thus the air-fuel ratio can be prevented from becoming rough. Further, since the amount of evaporated fuel that can be introduced to the adsorption layer 4'is reduced, deterioration of the adsorption layer 4'can be reduced.

Even if the pressure in the first back pressure chamber 62b is further increased, the displacement of the diaphragm 12a is limited by the stopper 66, so that the opening pressure of the first pressure control valve 12 does not become infinitely high. Therefore, the pressure in the fuel tank 16 does not become abnormally high. In the present embodiment, the adsorbent capacity varying means corresponds to the first pressure control valve 12, which is the evaporated fuel control valve, the second pressure control valve 10, the springs 12c and 10c, and the vapor guide 8.

In the sixth embodiment, the second pressure control valve 10
Instead of the above, when the first pressure control valve 12 is opened, the communication between the second vapor chamber 14 'and the vapor diffusion chamber 3 is cut off.
A switching valve 30 as in the third embodiment may be provided.
As a result, it is possible to prevent the evaporated fuel from being discharged from the second vapor chamber 14 ′ to the vapor diffusion chamber 3 when a large amount of the evaporated fuel is being guided from the fuel tank 16 to the canister 15. For this reason, the evaporated fuel is always purged into the intake passage 1a via the adsorption layer 4 ', so that the concentration of the evaporated fuel in the purge gas can be kept even lower.

Further, a purge control valve control device for feedback-controlling the opening ratio of the purge control valve 2 so that the evaporated fuel concentration in the intake air becomes the target concentration, or fuel injection so that the air-fuel ratio becomes the target air-fuel ratio. When the evaporative fuel treatment system of the present embodiment is applied to an internal combustion engine equipped with an air-fuel ratio control device for feedback control of the amount, since the evaporative fuel concentration in the purge gas is kept low, the air-fuel ratio of the feedback control is delayed by Roughness can be reduced.

FIG. 9 shows a seventh embodiment of the present invention. In this example, as in the third embodiment, a single vapor chamber 34 connected to the fuel tank 16 via the vapor passage 18 is provided. The vapor chamber 34 is connected to the vapor diffusion chamber 3 via the second pressure control valve 10. On the other hand, the branch passage 70 branched from the vapor passage 18 is connected to the vapor guide 8 extending to almost the center of the adsorption layer 4 '. The first pressure control valve 12 is arranged in the branch passage 70, and in the present embodiment, the first pressure control valve 12 is composed of an electromagnetic valve which is controlled to open and close based on an output signal from the electronic control unit 80. . In the present embodiment, the first pressure control valve 12 is selectively controlled to either the open state or the closed state.

Further, referring to FIG. 9, the electronic control unit 80 comprises a digital computer, and a ROM (Read Only Memory) 82, a RAM (Random Access Memory) 83, which are mutually connected via a bidirectional bus 81.
It has a CPU (microprocessor) 84, an input port 85 and an output port 86. An air flow meter 87 that generates an output voltage proportional to the intake air amount is provided in the intake passage 1a upstream of the throttle valve 1c, and the output voltage of the air flow meter 87 is input to the input port 85 via the AD converter 88. . An idle switch 89 that is turned on when the throttle valve 1c is at the idling opening is connected to the throttle valve 1c, and an output signal of the idle switch 89 is input to the input port 85. Vapor passage 18
A pressure sensor 90 for generating an output voltage proportional to the pressure in the branch passage 70, that is, the pressure in the fuel tank 16, is mounted in the branch passage 70 between the first pressure control valve 12 and
The output signal of the pressure sensor 90 is input to the input port 85 via the AD converter 91. Further, the input port 85 is connected to a crank angle sensor 92 that generates an output pulse each time the crankshaft rotates, for example, 30 degrees. CP
At U54, the engine speed is calculated based on this output pulse. On the other hand, the output port 86 has a corresponding drive circuit 93.
The purge control valve 2, the first pressure control valve 12, and the fuel injection valve 1d attached to the engine body 1 are respectively connected via the.

When the pressure inside the vapor chamber 34 rises to the opening pressure of the second pressure control valve 10, the second pressure control valve 10 opens. At this time, the first pressure control valve 12 is closed,
As a result, the evaporated fuel in the vapor chamber 34 flows into the vapor diffusion chamber 3. Therefore, in this case, the capacity of the adsorption layer 4'between the fuel tank 16 and the intake passage 1a is zero, and thus the deterioration of the adsorption layer 4'can be reduced.

When the pressure in the vapor chamber 34 further rises and the pressure PT detected by the pressure sensor 90 reaches a set pressure P1 which is higher than the opening pressure of the second pressure control valve 10, the first pressure control valve 10 is opened. As a result, the vaporized fuel guided from the fuel tank 16 to the canister 15 is guided through the vapor guide 8 to almost the center of the adsorption layer 4 '.
Therefore, in this case, the fuel tank 16 and the intake passage 1a
The capacity of the adsorption layer 4'between is approximately half of the total capacity of the adsorption layer 4 '. As a result, it is possible to prevent the amount of evaporated fuel purged in the intake passage 1a from changing rapidly. That is, in the present embodiment, the fuel tank 16 to the canister 1
When the amount of evaporated fuel introduced to the fuel cell 5 is large, the capacity of the adsorption layer 4'between the fuel tank 16 and the intake passage 1a is increased as compared with the case where the amount is small.

By the way, as described above, when the amount of evaporated fuel purged in the intake passage 1a changes, the air-fuel ratio also changes. In this case, when the intake air amount is large, the influence of the fluctuation of the purged evaporated fuel amount on the air-fuel ratio is smaller than when the intake air amount is small. Therefore, in the present embodiment, when PT ≧ P1 is satisfied and the first pressure control valve 12 is to be opened, when the intake air amount Q is larger than the preset set air amount Q1, the first pressure control valve 12 is opened. The valve is closed so that the evaporated fuel is not guided into the adsorption layer 4 ′ via the vapor guide 8. As a result, the evaporated fuel is purged into the intake passage 1a via the second pressure control valve 10 and the vapor diffusion chamber 3, so that in this case, the adsorption layer 4'between the fuel tank 16 and the intake passage 1a is formed. The capacity becomes zero. Thus, the deterioration of the adsorption layer 4'can be reduced.

On the other hand, when PT <P1, Q <Q1
At this time, the first pressure control valve 12 is opened so that the evaporated fuel is guided to the adsorption layer 4 '. As a result, it is possible to prevent the amount of evaporated fuel purged in the intake passage 1a from fluctuating rapidly, and thus prevent the air-fuel ratio from fluctuating.

Further, in the internal combustion engine shown in FIG. 9, the fuel injection action from the fuel injection valve 1d is temporarily stopped according to the operating state of the engine. That is, during the engine deceleration operation, when the engine speed N is higher than the predetermined first set speed N1, the fuel injection action is stopped so that the fuel consumption amount is minimized. On the other hand, when the fuel injection action is stopped, the engine speed N is set to be lower than the first set speed N1 and the second set speed N is set.
When it becomes lower than 2, the fuel injection action is restarted, thereby preventing the engine from misfiring.

When the purging action is performed while the fuel injection action is temporarily stopped, the air-fuel mixture formed by the evaporated fuel at this time is extremely lean, so that it is not combusted well in the combustion chamber of the engine and exhausted. The gas is discharged into the passage 1b. Therefore, in the embodiment of FIG. 9, when the fuel injection action is temporarily stopped, the purge action is also temporarily stopped. As a result, the evaporated fuel can be prevented from being discharged into the exhaust passage 1b without being burned in the combustion chamber.

As described above, if the first pressure control valve 12 is closed while the purging action is stopped due to the stop of the fuel injection action, a large amount of the evaporated fuel introduced to the canister 15 is then discharged to the second position. The vapor diffusion chamber 3 via the pressure control valve 10
Be guided inside. However, since the purge control valve 2 is closed when the purging operation is stopped, the vapor diffusion chamber 3 is filled with a large amount of evaporated fuel. At this time, when the purge action is restarted and the purge control valve 2 is opened, a large amount of the evaporated fuel in the vapor diffusion chamber 3 is purged into the intake passage 1a, so that the air-fuel ratio becomes rough. Become. Therefore, in the present embodiment, the first pressure control valve 12 is provided when the purging action is stopped as the fuel injection action is stopped.
Is opened so that the evaporated fuel is guided into the adsorption layer 4 '. As a result, the vapor diffusion chamber 3 is prevented from being filled with a large amount of vaporized fuel when the purging action is stopped, and thus a large amount of vaporized fuel is prevented from being purged into the intake passage 1a when the purging action is restarted. be able to. Thus, it is possible to prevent the air-fuel ratio from becoming rough when the purging action is restarted.

Further, in the example shown in FIG. 9, the first pressure control valve 12 is controlled based on the deviation of the feedback correction coefficient for making the air-fuel ratio the target air-fuel ratio. The average value FAFAV of the feedback correction coefficient fluctuates around 1.0, and therefore the average value F of the feedback correction coefficient F
If the deviation amount 1-FAFAV of AFAV is within the range of -X to X, the deviation between the air-fuel ratio and the target air-fuel ratio is small, that is, the air-fuel ratio is not rough. Here, X is a constant value. Therefore, in the present embodiment, even when PT ≧ P1 is satisfied, if −X ≦ 1-FAFAV ≦ X, it is determined that the air-fuel ratio is not rough, and the first pressure control valve 12 is closed. As a result, the evaporated fuel is prevented from being guided into the adsorption layer 4 ′ via the vapor guide 8. As a result, the evaporated fuel flows into the vapor diffusion chamber 3 via the second pressure control valve 10 and is then purged into the intake passage 1a. Therefore, the deterioration of the adsorption layer 4'can be further reduced. On the other hand, -X> 1-FAFAV, or 1-
When FAFAV> X, the evaporated fuel is guided to almost the center of the adsorption layer 4'via the vapor guide 8, and as a result, a large amount of the evaporated fuel can be prevented from being purged in the intake passage 1a.

10 and 11 show a routine for executing the above-described embodiment. These routines are executed in the main routine, for example. First, referring to FIG. 10, in step 100, it is determined whether or not the idle switch 89 that is turned on during engine deceleration operation is on. When the idle switch 89 is off, the routine proceeds to step 101, where the flag set when the fuel injection action and the purge action should be temporarily stopped is reset. Next, at step 102, the fuel injection action is executed. Next, the routine proceeds to step 103, where the purge control valve 2 is opened to execute the purge action.

When the idle switch 89 is turned on in step 100, the routine proceeds to step 104, where it is judged if the flag is set or not. Since this flag is normally reset, then step 105
Then, it is determined whether the engine speed N is higher than the first set speed N1. When N <N1, the processing cycle ends. Therefore, in this case, the flag is maintained in the reset state, and the fuel injection action and the purge action are continuously executed. On the other hand, step 105
When N ≧ N1, the process proceeds to step 106 and the flag is set. Then, it proceeds to step 107 and step 108. In step 107, the fuel injection action is temporarily stopped, and in step 108, the purge action is stopped by closing the purge control valve 2.
Then, the processing cycle is ended.

If the flag is set when the idle switch 89 is on, the routine proceeds from step 104 to step 109. At step 109, it is judged if the engine speed N is higher than the second set speed N2. N
If ≧ N2, then the processing cycle is ended. Therefore, in this case, the flag is kept set, and the fuel injection action and the purge action are continuously stopped. On the other hand, when N <N2 in step 109, the process proceeds to steps 101, 102, and 103. Therefore, the fuel injection action and the purge action are restarted. Then, the processing cycle is ended.

Next, referring to FIG. 11, first, step 1
At 10, it is judged whether or not the purging operation is currently performed. When the purging action is being performed, then the routine proceeds to step 111. At step 111, it is judged if the pressure PT detected by the pressure sensor 89 is higher than the set pressure P1. When PT ≧ P1, the process proceeds to step 112, and when PT <P1, the process proceeds to step 114. At step 112, it is judged if the deviation amount 1-FAFAV of the feedback correction coefficient average value is in the range from -X to X. When -X≤1-FAFAV≤X, the routine proceeds to step 114, where -X> 1-FAF
When AV or 1-FAFAV> X, the routine proceeds to step 113. In step 113, the intake air amount Q detected by the air flow meter 87 is the set air amount Q1.
It is determined whether or not there are more than. When Q ≧ Q1, the process proceeds to step 114, and when Q <Q1, the process proceeds to step 115. In step 115, the first pressure control valve 12 is opened. Then, the processing cycle is ended.

On the other hand, when the purging action is not performed in step 110, the process proceeds to step 114. At step 114, it is judged if the flag controlled by the routine of FIG. 10 is set. The purging action is not performed when the conditions for starting the purging action are not satisfied, such as during engine warm-up operation, or
Alternatively, when the flag is set and stopped together with the fuel injection action. Therefore, the flag is reset when the process proceeds to step 114 when the condition for starting the purge action is not satisfied, and therefore the process proceeds to step 116. Also, steps 111 and 11
If the routine proceeds from 2,113 to step 114, the purging action is being performed, that is, the flag has been reset, so the routine proceeds to step 116. Step 116
Then, the first pressure control valve 12 is closed, and then the processing cycle is ended. On the other hand, if the flag is set in step 114, then the routine proceeds to step 115, where the first pressure control valve 12 is opened and then the processing cycle is ended.

Next, an eighth embodiment of the present invention will be described. In this embodiment, as the evaporated fuel processing apparatus, the same apparatus as the evaporated fuel processing apparatus in the seventh embodiment described with reference to FIG. 9 is used, and similarly to the seventh embodiment, fuel injection is performed according to the engine operating state. The action and the purging action are temporarily stopped. However, in this embodiment, the valve opening ratio of the first pressure control valve 12 is controlled based on the duty ratio.

In the embodiment of FIG. 9, when the pressure in the fuel tank 16 is high during the purging operation, the deviation amount of the average value of the feedback correction coefficient is large, and the intake air amount is small, or When the pressure in 16 is low, the deviation amount of the average value of the feedback correction coefficient is small, or the intake air amount is large, the first pressure control valve 12
Is opened so that the evaporated fuel is guided into the adsorption layer 4 ′ through the vapor guide 8. On the other hand, when the pressure in the fuel tank 16 is low, the deviation amount of the feedback correction coefficient average value is small, or the purge action is performed when the intake air amount is large, the first pressure control valve 1
2 is closed, so that the vaporized fuel is vaporized in the vapor diffusion chamber 3
I try to lead them inside. On the other hand, in this embodiment, when the condition for opening the first pressure control valve 12 in the embodiment of FIG. 9 is satisfied, the duty ratio DUTY for controlling the opening ratio of the first pressure control valve 12 is set to a constant value Y. The vapor guide 8
It is designed to be guided into the adsorption layer 4'through. As a result, a large amount of evaporated fuel can be prevented from being purged in the intake passage 1a.

On the other hand, in the embodiment of FIG. 9, when the condition for closing the first pressure control valve 12 is satisfied, the duty ratio DUTY of the first pressure control valve 12 is decreased by Y, so that the evaporated fuel is vaporized as much as possible. It is prevented from being guided to the inside of the adsorption layer 4 ′ via 8. In this case, the evaporated fuel in the fuel tank 16 is guided into the vapor chamber 34, and if the pressure in the vapor chamber 34 reaches the valve opening pressure of the second pressure control valve 10, the evaporated fuel in the vapor chamber 34 is controlled by the second pressure. It will be introduced into the vapor diffusion chamber 3 via the valve 10.
As a result, deterioration of the adsorption layer 4'can be reduced.

Next, a routine for executing the above-mentioned eighth embodiment will be described with reference to FIG. This routine includes the same parts as the routine shown in FIG. 11, and therefore, the same reference numerals are used for the steps similar to those in the routine shown in FIG. The parts different from the routine of FIG. 11 will be described below. When Q <Q1 in step 113,
Alternatively, when the flag controlled by the routine of FIG. 10 is set in step 114, the process proceeds to step 120. In step 120, the first pressure control valve 1
The duty ratio DUTY for controlling the valve opening ratio of 2 is increased by the constant value Y. Then, it proceeds to step 122. On the other hand, if the flag is not set in step 114, then the routine proceeds to step 121, where the duty ratio DUTY of the first pressure control valve 12 is decreased by a constant value Y. Then, it proceeds to step 122. In step 122, the first pressure control valve 12 is determined based on the duty ratio DUTY calculated in step 120 or step 121.
Is driven. Then, the processing cycle is ended. Other configurations and operations of the evaporated fuel processing device are similar to those of the seventh embodiment, and therefore description thereof is omitted.

Next, a ninth embodiment of the present invention will be described. In this embodiment, as the evaporated fuel processing apparatus, the same apparatus as the evaporated fuel processing apparatus in the seventh embodiment described with reference to FIG. 9 is used, and similarly to the seventh embodiment, fuel injection is performed according to the engine operating state. The action and the purging action are temporarily stopped. Further, in this embodiment, as in the case of the eighth embodiment, the opening ratio of the first pressure control valve 12 is controlled based on the duty ratio.

In this embodiment, when the pressure in the fuel tank 16 is high and the deviation amount of the feedback correction coefficient average value is large during the purging action, the intake air amount Q
Accordingly, the duty ratio DUTY of the first pressure control valve 12 is determined. That is, as shown in FIG. 13, the duty ratio DUTY of the first pressure control valve 12 is set to be smaller when the intake air amount Q is larger than when it is small. Therefore, when the intake air amount Q is large, the adsorption layer 4'via the vapor guide 8 as compared to when the intake air amount Q is small.
Therefore, the amount of fuel vapor introduced to the fuel cell is reduced, and therefore the deterioration of the adsorption layer 4'can be reduced. The relationship between the duty ratio DUTY of the first pressure control valve 12 and the intake air amount Q is RO in advance in the form of a map shown in FIG.
It is stored in M83.

On the other hand, whether the pressure in the fuel tank 16 is low,
When the deviation amount of the feedback correction coefficient average value is small or the intake air amount is large, the duty ratio DUTY when the purge action is stopped together with the fuel injection action.
Is set to 100% and the duty ratio DUTY is set to 0% when the purging action is performed. As a result, when the purging action is stopped, all the evaporated fuel in the fuel tank 16 is guided into the adsorption layer 4 ′ via the vapor guide 8, so that the inside of the vapor diffusion chamber 3 is stopped while the purging action is stopped. It is possible to prevent filling with a large amount of evaporated fuel. On the other hand, when the purging action is performed, the evaporated fuel is prevented from being guided into the adsorption layer 4'through the vapor guide 8, and thus the deterioration of the adsorption layer 4'can be reduced.

Next, the routine for executing the ninth embodiment will be described with reference to FIG. This routine includes the same parts as the routine shown in FIG. 11, and therefore, the same reference numerals are used for the steps similar to those in the routine shown in FIG. The parts different from the routine of FIG. 11 will be described below. In step 112, -X> 1-FAF
When AV or 1-FAFAV> X, the routine proceeds to step 130. In step 130, the duty ratio DUTY that controls the valve opening ratio of the first pressure control valve 12 is calculated from the map of FIG. Then, it proceeds to step 133. On the other hand, when the flag controlled by the routine of FIG. 10 is reset in step 114, the routine proceeds to step 131, where the duty ratio DUTY is set to 0%. Then, it proceeds to step 133. On the other hand, if the flag is set in step 114, then the routine proceeds to step 132, where the duty ratio is set to 100%.
And Then, it proceeds to step 133. Step 133
Then, the first pressure control valve 12 is driven based on the duty ratio DUTY calculated in step 130, 131, or 132. Then, the processing cycle is ended.

FIG. 15 shows a tenth embodiment of the present invention. The evaporated fuel processing device in this embodiment is almost the same as the seventh embodiment described with reference to FIG. However, in this embodiment, it is not necessary to provide the pressure sensor in the branch passage 70. A check valve 22 similar to that of the second embodiment is provided at the end 7 of the vapor guide 8. The valve opening pressure of the check valve 22 is set higher than the valve opening pressure of the second pressure control valve 10.

As the purge action continues, the amount of evaporated fuel introduced from the fuel tank 16 to the canister 15 gradually decreases, and when the purge action time reaches, for example, about 30 minutes, the evaporation introduced from the fuel tank 16 to the canister 15 evaporates. The amount of fuel is small. At this time, the adsorption layer 4 '
The amount of evaporated fuel adsorbed in the inside of the intake passage 1a also becomes small, and therefore, if the time during which the purging action is performed is lengthened to a certain extent, there is no possibility that a large amount of evaporated fuel will be purged into the intake passage 1a. Therefore, in this embodiment, the time T during which the purge action is performed
When D becomes longer than a predetermined set time T1, the first pressure control valve 12 is closed so that the evaporated fuel is not guided into the adsorption layer 4'through the vapor guide 8. As a result, the deterioration of the adsorption layer 4'can be reduced. On the other hand, when TD <T1, the vaporized fuel separated from the adsorption layer 4'and the vaporized fuel guided to the canister 15 from the fuel tank 16 are purged into the intake passage 1a, so that a large amount of the vaporized fuel is introduced into the intake passage 1a. The first pressure control valve 12 is opened on the basis that it is judged that the evaporated fuel of 10 can be purged. As a result, the evaporated fuel is introduced into the adsorption layer 4'through the vapor guide 8, and thus a large amount of the evaporated fuel can be prevented from being purged in the intake passage 1a.

Next, a routine for executing the above tenth embodiment will be described with reference to FIG. This routine includes the same parts as the routine shown in FIG. 11, and therefore, the same reference numerals are used for the steps similar to those in the routine shown in FIG. The parts different from the routine of FIG. 11 will be described below. When the purging action is being performed in step 110, the process proceeds to step 140. In step 140, when the time TD during which the purge action is performed is TD ≧ T1 longer than the set time T1, then step 114
Proceed to. On the other hand, when TD <T1, the process proceeds to step 112. Note that the time TD during which the purging action is performed
Is detected by a timer in the electronic control unit 80, for example.

In this embodiment, a check valve 22 is provided at the end 7 of the vapor guide 8. Therefore, even if the first pressure control valve 12 is opened, the pressure in the vapor guide 8, that is, the pressure in the fuel tank 16 can be increased to the valve opening pressure of the check valve 22. As a result, the pressure in the fuel tank 16 can be brought close to the saturated vapor pressure of the fuel, so that the generation of evaporated fuel can be suppressed.

FIG. 17 shows an eleventh embodiment of the present invention. In this embodiment, the vapor passage 18 is connected to the switching valve 150. The switching valve 150 causes the vapor passage 18 to pass through the first vapor guide 1 based on an output signal from the electronic control unit 80.
58 or a second vapor guide 158 '. The first vapor guide 158 extends almost to the center of the adsorption layer 4 ′, while the second vapor guide 158 ′ is opened in the vapor diffusion chamber 3. Still referring to FIG. 17, a pressure control valve 151 is provided in the vapor passage 18.

In this embodiment, when the purging action is performed for a short period of time, the feedback correction coefficient average deviation is large, and the intake air amount is small, or the purging action is performed. Have you spent a lot of time
When the deviation amount of the feedback correction coefficient average value is small or the intake air amount is large and the fuel injection action and the purge action are stopped, the switching valve 150 is controlled to connect the vapor passage 18 to the first vapor guide 158. To do. As a result, the evaporated fuel is guided through the vapor guide 8 into the adsorption layer 4 ', so that a large amount of the evaporated fuel can be prevented from being purged in the intake passage 1a. On the other hand, when the purge action is performed for a long time, the deviation amount of the feedback correction coefficient average value is small, or when the intake air amount is large, the switching valve 150 is controlled to control the vaporization. The passage 18 is connected to the second vapor guide 158 '. As a result, the evaporated fuel is guided into the vapor diffusion chamber 3, and therefore the deterioration of the adsorption layer 4'can be reduced.

Next, the routine for executing the above eleventh embodiment will be described with reference to FIG. This routine is shown in FIG.
16 and the routine shown in FIG. 16 is included. Therefore, the same reference numerals are used for the steps similar to those of the routines of FIGS. The parts different from the routines of FIGS. 11 and 16 will be described below.
When Q <Q1 in step 113, or when the flag controlled by the routine of FIG. 10 is set in step 114, the routine proceeds to step 160. In step 160, the switching valve 150 is controlled to connect the vapor passage 18 to the first vapor guide 158. On the other hand, when the flag is reset in step 114, the process proceeds to step 161. In step 161, the switching valve 150 is controlled to connect the vapor passage 18 to the second vapor guide 158 '.

The pressure control valve 151 is kept closed until the pressure in the fuel tank 16 reaches the valve opening pressure set by the spring 151c. Therefore fuel tank 1
The pressure in 6 can rise to the valve opening pressure of the pressure control valve 151. As a result, the pressure in the fuel tank 16 can be brought close to the saturated vapor pressure of the fuel, so that the generation of evaporated fuel can be suppressed.

In this embodiment, the switching valve 150 selectively connects the vapor passage 18 to either the first vapor guide 158 or the second vapor guide 158 '. However, the switching valve 150 is composed of a duty control valve, and the vapor passage 18 is connected to the first vapor guide 158 for the time corresponding to the duty ratio of the cycle time, and the vapor passage 18 is connected to the second vapor guide 158 'for the remaining time. You can also choose to do so. In this case, the duty ratio DUTY in the embodiment with reference to FIG. 12 or 14 can be used as the duty ratio of the switching valve 150.

In the embodiment described with reference to FIGS. 9 to 18, the evaporated fuel processing apparatus of the present invention temporarily stops the fuel injection action and the purge action according to the engine speed N during engine deceleration operation. It is applied to an internal combustion engine that is designed to do so. However, the evaporated fuel processing device of the present invention is applied to an internal combustion engine in which the fuel injection action is temporarily stopped in order to prevent the engine speed N from further increasing when the engine speed N becomes excessively high. It can also be applied. on the other hand,
If fuel injection is performed when the required fuel injection amount becomes extremely small, the fuel amount injected from the fuel injection valve 1d easily deviates from the regular fuel amount. Therefore, there is also known an internal combustion engine in which the fuel injection action is temporarily stopped when the required fuel injection amount becomes extremely small. The evaporated fuel processing device of the present invention can be applied to such an internal combustion engine.

[0073]

According to the invention described in claim 1, the capacity of the adsorption layer between the fuel tank and the intake passage is increased as the amount of the evaporated fuel introduced from the fuel tank to the adsorption layer is increased. Is temporarily adsorbed in the adsorption layer and then gradually purged into the intake passage, so that it is possible to prevent the amount of evaporated fuel purged into the intake passage from fluctuating rapidly. That is, the concentration of the evaporated fuel in the purge gas can be stabilized regardless of the amount of the evaporated fuel introduced from the fuel tank to the adsorption layer, and thus the air-fuel ratio can be prevented from becoming rough. On the other hand, if the amount of evaporated fuel flowing into the adsorption layer decreases, the capacity of the adsorption layer between the fuel tank and the intake passage is reduced, and as a result, the adsorption / desorption action of the evaporated fuel in the adsorption layer can be reduced. Therefore, deterioration of the adsorption layer can be reduced, that is, the life of the adsorption layer can be extended.

According to the second aspect of the present invention, the valve opening pressure of the evaporated fuel control valve can be increased, thereby increasing the pressure in the fuel tank. Therefore, the pressure in the fuel tank is set to the saturated vapor pressure of fuel. You can get closer. As a result, it is possible to suppress further generation of evaporated fuel in the fuel tank. Therefore, the amount of evaporated fuel purged into the intake passage can be reduced, so that the concentration of evaporated fuel in the purge gas can be further stabilized.

According to the third aspect of the invention, when the intake air amount is large, the fluctuation of the purged evaporated fuel amount has a small effect on the air-fuel ratio. Therefore, when the intake air amount is large, there is a difference between the fuel tank and the intake passage. Reduce the capacity of the adsorption layer,
Thereby, the evaporated fuel is prevented from being introduced into the adsorption layer as much as possible, so that the deterioration of the adsorption layer can be further reduced.

According to the fourth aspect of the invention, since the capacity of the adsorption layer between the fuel tank and the intake passage is increased when the purging action is stopped as the fuel injection action is stopped, the purging action is stopped during the purging action. It is possible to prevent a large amount of evaporated fuel from flowing into the vapor diffusion chamber. Therefore, when the purging action is restarted, a large amount of evaporated fuel can be prevented from being purged from the vapor diffusion chamber into the intake passage, and thus the air-fuel ratio can be further prevented from becoming rough.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of an evaporated fuel processing apparatus for an internal combustion engine.

FIG. 2 is a diagram showing a relationship between an evaporated fuel generation amount (≈fuel temperature) and a tank pressure.

FIG. 3 is a diagram showing a second embodiment of an evaporated fuel processing apparatus for an internal combustion engine.

FIG. 4 is a diagram showing a third embodiment of an evaporated fuel processing apparatus for an internal combustion engine.

FIG. 5 is a diagram showing a fourth embodiment of an evaporated fuel processing apparatus for an internal combustion engine.

FIG. 6 is a diagram showing a fifth embodiment of an evaporated fuel processing apparatus for an internal combustion engine.

FIG. 7 is a diagram showing a fifth embodiment of an evaporated fuel processing apparatus for an internal combustion engine.

FIG. 8 is a diagram showing a sixth embodiment of an evaporated fuel processing apparatus for an internal combustion engine.

FIG. 9 is a diagram showing a seventh embodiment of an evaporated fuel processing apparatus for an internal combustion engine.

FIG. 10 is a diagram showing a flowchart for executing the seventh embodiment.

FIG. 11 is a view showing a flowchart for executing the seventh embodiment.

FIG. 12 is a diagram showing a flowchart for executing the eighth embodiment.

FIG. 13 is a diagram showing a relationship between a duty ratio for driving a first pressure control valve and an intake air amount.

FIG. 14 is a view showing a flowchart for executing the ninth embodiment.

FIG. 15 is a diagram showing a tenth embodiment of an evaporated fuel processing apparatus for an internal combustion engine.

FIG. 16 is a diagram showing a flowchart for executing the tenth embodiment.

FIG. 17 is a diagram showing an eleventh embodiment of an evaporated fuel processing apparatus for an internal combustion engine.

FIG. 18 is a diagram showing a flowchart for executing the eleventh embodiment.

[Explanation of symbols]

1a ... Intake passage 2 ... Purge control valve 4 '... adsorption layer 10 ... Second pressure control valve 12 ... First pressure control valve 14 ... First vapor room 14 '... second vapor room 15 ... Canister 16 ... Fuel tank 34 ... Vapor room 40 ... Pressure control valve

Claims (4)

(57) [Claims] 1. An evaporative fuel for an internal combustion engine in which an adsorption layer for temporarily storing evaporative fuel is interposed between a fuel tank and an engine intake passage, and the evaporative fuel in the adsorption layer is purged into the engine intake passage. In the processing equipment, engine intake from the adsorption layer
When the purge action of fuel vapor in the passageway are purged from the fuel tank than when less when often amount of fuel vapor is guided to the adsorption layer, increasing the volume of the adsorbing layer interposed between the fuel tank and the engine intake passage Evaporative fuel treatment apparatus for internal combustion engine, which is provided with an adsorption layer capacity changing means. 2. A vaporized fuel control valve for controlling the amount of vaporized fuel introduced from the fuel tank to the adsorption layer is provided between the fuel tank and the adsorption layer, and the vaporized fuel control valve is formed of a control valve having a variable valve opening pressure. 2. The evaporative fuel treatment apparatus for an internal combustion engine according to claim 1, wherein the valve opening pressure of the evaporative fuel control valve is increased as the amount of evaporative fuel introduced from the fuel tank to the adsorption layer is larger. 3. An internal combustion engine is provided with intake air amount detecting means for detecting an intake air amount, and when the intake air amount detected by the intake air amount detecting means is large, it is compared with a fuel tank when it is small. The evaporated fuel processing apparatus for an internal combustion engine according to claim 1, wherein the capacity of the adsorption layer interposed between the engine intake passages is reduced. 4. The internal combustion engine is provided with fuel injection action stopping means for temporarily stopping the fuel injection action according to the engine operating state, and a vapor diffusion chamber provided between the adsorption layer and the engine intake passage is provided. It is connected to the engine intake passage via the purge control valve, and when the fuel injection action is stopped by the fuel injection action stopping means, the purge action is stopped by closing the purge control valve. The evaporation of the internal combustion engine according to claim 1, wherein the capacity of the adsorption layer interposed between the fuel tank and the vapor diffusion chamber is made larger when the purging action is stopped than when the purging action is performed. Fuel processor.