JPH0537009Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a fuel vapor emission control device for an internal combustion engine.

[Conventional technology and problems]

The fuel vapor vaporized in the car's fuel tank is temporarily adsorbed on activated carbon in a single activated carbon container, and the fuel adsorbed on the activated carbon is separated from the activated carbon and introduced into the engine's intake system to remove harmful components. A fuel vapor emission control device is known that prevents fuel vapor containing fuel vapor from being released into the atmosphere. However, in such a device, the air-fuel ratio of the intake air supplied to the engine changes greatly between immediately before and after refueling, which may increase harmful components in the exhaust gas or reduce operating performance.

As a countermeasure to this problem, the fuel vapor emission control device disclosed in JP-A No. 55-161952 uses an activated carbon container that adsorbs the fuel vapor naturally generated in the fuel tank, and also opens a passage leading into the fuel tank only when refueling. It is equipped with an activated carbon container that adsorbs fuel vapor. However, since this device requires two activated carbon containers, there is a problem that the installation space is large and the cost is high. In addition, since the activated carbon containers are separated by purpose, one container cannot adsorb fuel vapor beyond its fuel adsorption capacity (hereinafter referred to as "breakthrough"), while the other container has sufficient fuel adsorption capacity. In other words, there was a problem that the entire fuel adsorption capacity of the activated carbon could not be effectively utilized.

[Means for solving problems]

In order to solve the above problems, the present invention
an activated carbon container that is divided into a chamber and a second chamber and stores activated carbon therein; a first vapor passage and a second vapor passage that respectively connect the first chamber and the second chamber in parallel to the same fuel tank; a vapor passage, a first purge passage and a second purge passage that respectively connect the first chamber and the second chamber in parallel to the intake system of the engine; an air inlet provided in the activated carbon container; A communication portion between the first chamber and the second chamber formed near the air inlet in the activated carbon container, and a relatively low pressure fuel vapor inserted into the first vapor passage in the fuel tank. a first check valve that opens in response to pressure; a second check valve that is inserted into the second vapor passage and opens in response to relatively high fuel vapor pressure in the fuel tank; and the second purge valve. There is provided a fuel vapor emission suppressing device characterized by comprising means for making the flow resistance of the passage larger than the flow resistance of the first purge passage.

[Effect]

Normally, relatively low-pressure fuel vapor naturally generated from the fuel tank flows into the first chamber of the activated carbon container by opening the first check valve in the first vapor passage, and is adsorbed by the activated carbon in the first chamber. However, when refueling, the fuel in the fuel tank is stirred and a large amount of fuel vapor is suddenly generated, increasing the vapor pressure of the fuel in the fuel tank. The second check valve in the vapor passage is opened to allow the vapor to flow into the second chamber, where it is also adsorbed by the activated carbon in the second chamber. When the activated carbon in the first chamber is breached by a large amount of fuel vapor, the fuel vapor flows from the first chamber into the second chamber through the communication part,
Since the fuel is adsorbed by the activated carbon in the second chamber, there is no concern that the fuel vapor will leak outside.

The fuel vapor adsorbed in the activated carbon container is generated when the air that flows in from the air inlet of the activated carbon container by suction from the engine's intake system flows through the gap between the activated carbon in the first and second chambers. The activated carbon is desorbed from the activated carbon, and at the same time, the activated carbon is regenerated. However, in the present invention, a means is provided to make the flow resistance of the second purge passage larger than that of the first purge passage. The amount of air passing through the second chamber is less than the amount of air passing through the first chamber, and the amount of fuel vapor purged from the second chamber is smaller than the amount purged from the first chamber. Since the large amount of fuel vapor adsorbed in the interior is slowly purged, the problem of the air-fuel ratio changing significantly due to a sudden increase in the amount of fuel vapor sucked into the engine immediately after refueling the fuel tank is solved.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

A substantially cylindrical activated carbon container 1 filled with activated carbon has a first chamber 3 and a second chamber 4 formed by a cylindrical partition wall 2 concentric with the activated carbon container 1 .

The first chamber 3 communicates with a fuel tank 7 via a first check valve 5 provided on the top surface 1a of the cylindrical activated carbon container 1, a first vapor passage 18, and a common vapor passage 6. Further, the second chamber 4 communicates with a common fuel tank 7 via a second check valve 8, a second vapor passage 19, and a common vapor passage 6. The check valve 5 is for a small flow rate, but since the spring force of the valve spring is set to be relatively small, it opens when the vapor pressure of the fuel in the fuel tank 7 exceeds a relatively low predetermined value. On the other hand, check valve 8
is a valve for large flow rate compared to check valve 5, but since the spring force of its valve spring is set relatively large, the vapor pressure of the fuel in fuel tank 7 exceeds a relatively high predetermined value. It won't open until

The first chamber 3 communicates with the engine intake system via a check valve 9 alongside the check valve 5, a first purge passage 10, and a common purge passage 13. Further, the second chamber 4 has a check valve 12 and a second chamber 4.
It communicates with the intake system of the same engine via a purge passage 11 and a common purge passage 13. The check valves 9 and 12 are designed to open when the pressure difference between the first chamber 3 and the second chamber 4 and the intake system exceeds a predetermined value.

An orifice 14 for flow rate control is provided in the vicinity of the check valve 9 in the purge passage 10. The orifice 14 is capable of passing a relatively large flow rate. On the other hand, an orifice 15 for controlling the flow rate is also provided near the check valve 12 in the purge passage 11. The flow passage cross-sectional area of the orifice 15 is small, and the flow rate of fuel vapor passing through the purge passage 11 is restricted to about 1/3 of the flow rate of fuel vapor passing through the purge passage 10.

An air inlet 16 is formed in the center of the bottom surface 1b opposite to the top surface 1a of the approximately cylindrical activated carbon container 1. The partition wall 2 extending from the top surface 1a is
It terminates near the bottom surface 1b, and therefore, the first chamber 3 and the second chamber 4 communicate with each other through the communication portion 17 on the bottom surface 1b side.

The second chamber 4 is set to have a volume at least twice that of the first chamber 3, for example, the first chamber 3 has a volume of 800 c.c., and the second chamber 4 has a volume of 3000 c.c.

Next, the operation of this embodiment configured as described above will be explained.

At times other than refueling, the amount of fuel vapor generated within the fuel tank 7 is small, so the pressure within the fuel tank 7 is low. Therefore, valve 8 does not open, but check valve 5, which has a weak valve spring force, opens.
The fuel vapor will be adsorbed in the first chamber 3.
When the first chamber 3 is breached, the fuel vapor is transferred to the communication section 17.
Since the fuel vapor enters the second chamber 4 through the air and is adsorbed by the second chamber 4, the fuel vapor does not leak from the air inlet 16.

When refueling, the fuel in the fuel tank 7 is stirred, so a large amount of fuel vapor is generated in a short period of time, the pressure in the fuel tank 7 increases, and the valve 8
opens. At this time, both check valve 5 and valve 8 are open, but since check valve 5 can only flow at a smaller flow rate than valve 8, most of the fuel vapor passes through valve 8 to the second valve.
It will be adsorbed into chamber 4. The reaction in which fuel vapor is adsorbed onto activated carbon is an exothermic reaction;
Since a large amount of fuel vapor is adsorbed in the second chamber 4,
The heat generated in the chamber 4 is large, and this generated heat is transferred to the first chamber 3. As a result, the fuel vapor adsorption capacity of the activated carbon in the first chamber 3 is reduced, the amount of adsorption is suppressed, and breakthrough is likely to occur. And if it breaks,
The fuel vapor is adsorbed into the second chamber 4 via the communication portion 17. Therefore, the amount of adsorption in the first chamber 3 can be suppressed, and no fuel vapor is released into the atmosphere.

When the engine is operated, negative pressure is generated in the intake system, check valves 9 and 12 are opened, air passes from the air inlet 16 to the first chamber 3 and the second chamber 4, and the fuel adsorbed on the activated carbon is removed. activated carbon is recycled. Then, the air mixed with fuel vapor is introduced into the intake system through the purge passage 13.

At times other than refueling, a relatively large amount of fuel is adsorbed in the first chamber 3 and a relatively small amount of fuel is adsorbed in the second chamber 4. Therefore, a large amount of air with a high fuel vapor concentration flows through the purge passage 10, and a small amount of air with a low fuel vapor concentration flows through the purge passage 11.

On the other hand, during refueling, the amount of fuel adsorbed in the first chamber 3 is suppressed, so the amount of fuel adsorbed does not change significantly from times other than when refueling.On the other hand, a large amount of fuel is adsorbed in the second chamber 4. Ru. Therefore, although the fuel concentration of the air flowing through the purge passage 10 does not change much compared to times other than when refueling, a small amount of air with a high fuel concentration flows through the purge passage 11. As described above, although the fuel concentration of the air flowing through the purge passage 11 changes greatly, the flow rate of the air flowing through the purge passage 11 varies greatly.
Since the flow rate is smaller than the flow rate at zero, the fuel concentration of the air flowing through the common purge passage 13 and introduced into the intake system does not change significantly.

As described above, according to this embodiment, the amount of fuel adsorbed in the first chamber 3, which is purged in a relatively large amount, does not change significantly between immediately before and after refueling, while a large amount of fuel is adsorbed immediately after refueling. Since the amount of purge of the second chamber 4 is small, the fuel concentration of the air introduced into the intake system does not change significantly between immediately before and immediately after refueling.

Further, in this embodiment, since only one activated carbon container 1 is required, it is possible to provide a compact and low-cost steam emission suppression device.

Furthermore, the first chamber 3 and the second chamber 4 are connected to each other through a communication section 17.
Even if the first chamber 3 breaks through, the fuel vapor will be adsorbed into the second chamber 4 via the communication part 17, so that the entire fuel adsorption capacity of the activated carbon container 1 can be effectively utilized. be able to.

[Effect of idea]

As described above, according to the present invention, it is possible to provide a compact steam emission suppression device at a low cost in which the air-fuel ratio does not change much between immediately before and after refueling, and also to effectively utilize the entire fuel adsorption capacity of activated carbon. It is possible to provide a vapor emission suppression device that can.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a fuel vapor emission control device according to an embodiment of the present invention. 1...Activated carbon container, 3...First chamber, 4...Second
chamber, 5...first check valve, 7...fuel tank, 8...second check valve, 10...first purge passage, 11...second purge passage, 1
4, 15... Orifice for flow rate control, 16...
Air introduction port, 17... Communication portion, 18... First vapor passage, 19... Second vapor passage.

Claims (1)

[Scope of utility model registration request] an activated carbon container that is divided into a first chamber and a second chamber and stores activated carbon therein; a first vapor passage and a first vapor passage that respectively connect the first chamber and the second chamber in parallel to the same fuel tank; a first purge passage and a second purge passage that respectively connect the first chamber and the second chamber in parallel to an intake system of the engine; and an air inlet provided in the activated carbon container; , a communication part between the first chamber and the second chamber formed near the air inlet in the activated carbon container, and a relatively low pressure part in the fuel tank inserted into the first vapor passage. a first check valve opened by fuel vapor pressure; a second check valve inserted into the second vapor passage and opened by relatively high fuel vapor pressure in the fuel tank; and means for making the flow resistance of the purge passage larger than the flow resistance of the first purge passage.