JP2015124645A - Canister - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a size and a weight of a canister while improving adsorbing/desorbing performance by optimizing an adsorbent charged in a plurality of chambers in the canister.SOLUTION: An adsorbent is charged in each of a plurality of chambers 5-8 arranged in series along the flowing direction in a case 2. When an outer diameter of the adsorbent of a solid shape or a thickness of each portion of the adsorbent of a hollow shape is defined as a thickness of the adsorbent, and a ratio of microscopic pores of a size less than 500 nm among the microscopic pores of a size of 50 nm or more in the adsorbent is defined as a volume ratio of less than 500 nm, the thickness of the adsorbent charged in the plurality of chambers are gradually reduced, and the volume ratio of less than 500 nm is gradually increased from an inflow/outflow portion side toward an atmosphere open side.

Description

  The present invention relates to a canister that is used, for example, for the treatment of fuel vapor in an internal combustion engine for automobiles and uses activated carbon having microscopic pores and macroscopic pores as an adsorbent.

  For example, in an automobile internal combustion engine, a canister capable of adsorbing and desorbing fuel vapor is provided in order to prevent release of fuel vapor evaporated from a fuel tank of the vehicle to the outside. As is well known, the canister is filled with an adsorbent in the case, provided with an air opening at one end in the flow direction, and an inflow portion (charge) for the fuel vapor communicating with the fuel tank at the other end. Port) and a fuel vapor outflow portion (purge port) communicating with the intake passage of the internal combustion engine. Fuel vapor generated after the vehicle stops or the like is introduced from the fuel tank to the canister through the inflow portion, and is temporarily adsorbed by the adsorbent. During the subsequent operation, air flows in from the atmosphere opening port and flows out from the outflow part in the intake cycle of the internal combustion engine, and this intake flow removes the fuel components adsorbed on the adsorbent together with fresh air. The combustion treatment is performed in the combustion chamber from the outflow portion via the intake passage of the internal combustion engine.

  In such a canister, for example, in Patent Document 1, a plurality of chambers filled with an adsorbent are arranged in series along the flow direction in the canister case so that adsorption / desorption can be performed efficiently. It is disclosed that a heat storage adsorbent having a large heat capacity is disposed in the chamber on the opening side.

  Further, in Patent Document 2, as a technique for significantly reducing day and night breathing loss (DBL), an adsorbent filled in a canister is used with an n-butane concentration between 5% by volume and 50% by volume. Activated carbon (hereinafter referred to as “A charcoal”) having a difference in equilibrium adsorption amount of n-butane concentration exceeding 35 g / L and activated carbon having a difference of 35 g / L or less (hereinafter referred to as “B charcoal”). The chamber on the inflow / outflow section side is filled with an adsorbent using A charcoal, and the chamber on the atmosphere opening side is filled with an adsorbent using B charcoal. In this way, activated carbon with a small difference in equilibrium adsorption amount on the atmosphere opening side, that is, B charcoal with excellent desorption performance with a small effective adsorption amount (difference between adsorption amount after adsorption and after adsorption) is arranged. Thus, the discharge of fuel vapor to the atmosphere opening side is suppressed, and the breathing loss emission (DBL) is reduced day and night.

JP 2009-19572 A JP 2005-510654 A

  However, when the heat storage adsorbent is used as in Patent Document 1, the volume of the heat storage material is required in addition to the volume of the adsorbent, resulting in an increase in the size of the canister.

  Moreover, if the adsorbent using B charcoal with little effective adsorption amount is arrange | positioned like the patent document 2 in the atmosphere opening | mouth side, the capacity | capacitance (volume) of activated carbon required in order to ensure a predetermined effective adsorption amount will increase. However, enlargement of the canister and increase in weight are also problems.

  Therefore, the present invention is excellent in desorption performance even when an adsorbent using activated carbon with a large effective adsorption amount is disposed on the atmosphere opening side, and can sufficiently reduce day and night respiratory loss emissions (DBL). It aims to provide a possible new canister.

  The canister according to the present invention has an adsorbent filled in a plurality of chambers arranged in series along the flow direction in the case, an inflow / outflow portion of fuel vapor at one end in the flow direction, and an atmosphere at the other end. It has an open mouth.

  The adsorbent has a cylindrical or spherical solid shape or a hollow shape.

  Then, the outer diameter of the solid adsorbent or the thickness of each part of the hollow adsorbent is defined as the thickness of the adsorbent, and among the macroscopic pores having a size of 50 nm or more in the adsorbent When the ratio of the macroscopic pores having a size of less than 500 nm is defined as the volume ratio of less than 500 nm, the adsorbent filled in the plurality of chambers from the inflow / outflow portion side to the atmosphere opening side is defined. While decreasing the thickness stepwise, the volume ratio of less than 500 nm is increased stepwise.

  Preferably, the outer diameter of the adsorbent filled in the plurality of chambers is increased stepwise from the inflow / outflow side toward the atmosphere opening side.

  More preferably, the cross-sectional area of the plurality of chambers in the direction perpendicular to the passage is gradually reduced from the inflow / outflow side toward the atmosphere opening side.

  According to the present invention, the thickness of the adsorbent filled in the plurality of chambers arranged in series in the canister case from the inflow / outflow portion side to the air release port side is reduced to the air release port side. While gradually reducing the volume ratio of less than 500 nm toward the target, the adsorption / desorption performance is improved and the breathing loss emission (DBL) is greatly reduced while the adsorbent is reduced. The increase in capacity can be suppressed, and the canister can be reduced in size and weight.

  Further, the outer diameter of the adsorbent filled in the plurality of chambers is gradually increased from the inflow / outflow portion side toward the atmosphere opening side, and more preferably, the cross-sectional area of the plurality of chambers in the direction perpendicular to the passageway. By reducing the stepwise, the ventilation resistance can be suppressed while further reducing the breathing loss emission during the day and night.

1 is a cross-sectional view showing a canister according to a first embodiment of the present invention. The side view (a) and front view (b) which show a hollow adsorbent. The table | surface which shows each data of five activated carbon which can be used as an adsorbent. Sectional drawing which shows the shape of five activated carbons of FIG. The graph which shows distribution of the magnitude | size of the macroscopic pore of five activated carbons of FIG. The characteristic view which shows the day and night respiratory loss emission in the said 1st Example and a comparative example. Sectional drawing which shows the canister which concerns on 2nd Example of this invention.

  FIG. 1 shows a first embodiment of a canister 1 according to the present invention. This canister 1 has a flow path formed in a double U-turn shape by a case 2 made of synthetic resin. At one end in the flow direction, a charge port 3 serving as an inflow portion of fuel vapor, a fuel A purge port 4 serving as a steam outflow portion is provided, and an air port 5 serving as an air release port is provided at the other end in the flow direction. The charge port 3 is connected to a fuel tank of an automobile (not shown), for example, and the purge port 4 is connected to an intake system of an internal combustion engine, for example.

  In the case 2, a first chamber 6, a second chamber 7, a third chamber 8, and a fourth chamber 9 are arranged in series in order from the charge port 3 and purge port 4 side as a chamber for containing an adsorbent. Is provided. The first chamber 6 is filled with an adsorbent 10 having a relatively small particle diameter made of activated carbon A-1 described later. The second chamber 7 is filled with the adsorbent 11 using the activated carbon A-1. The third chamber 8 is filled with an adsorbent 12 using activated carbon A-2, which will be described later, and the fourth chamber 9 is an adsorbent having the largest outer diameter and having a honeycomb shape using activated carbon B-2, which will be described later. 13 is filled.

  As a result, a reduction in ventilation resistance is achieved in a portion close to the atmospheric port 5 in the flow path of the canister 1, and the detachment performance of the canister 1 as a whole is improved. The first chamber 6, the second chamber 7, the third chamber 8, and the fourth chamber 9 are separated from each other by, for example, a perforated plate or a filter having air permeability.

  The adsorbent 12 filled in the third chamber 8 has not only microscopic pores (pores having a diameter of 2 nm or more and less than 50 nm) of the activated carbon itself, but also macroscopic pores (diameter having a diameter of fuel vapor). For example, powdery activated carbon is solidified at room temperature and melted, sublimated, or decomposed at a firing temperature described later together with a binder and molded. Then, it is fired to obtain a granule having a predetermined size.

  The activated carbon is, for example, in the form of a powder having a particle diameter of 350 μm or less (42 mesh pass) by pulverizing commercially available activated carbon such as coal or wood. As the binder, powdered bentonite, Kibushi clay, silica sol, alumina sol or the like, or a solid content of the sol can be used. The meltable core is a powdery material (preferably having a particle size of 0.1 μm to 1 mm) that is solid at normal temperature and is vaporized, sublimated or decomposed at the firing temperature, and hardly soluble in water as a medium during production, For example, sublimable organic compounds (such as naphthalene and paradichlorobenzene), polymers having a high melting point and easily decomposable (such as polyethylene), and fibrous materials (φ0.1 μm to 100 μm × fiber length 1 mm or less), such as nylon Polyester, polypropylene, etc. can be used.

  Then, these three members are mixed with an appropriate blending ratio, and water is appropriately added. By extrusion, the diameter is 4 to 6 mm and the length is about 2 to 12 mm (preferably the length approximately equal to the diameter). Molded into a cylindrical shape. And this molded object is baked for 3 to 4 hours at 650 degreeC-1000 degreeC by inert gas atmosphere using a rotary kiln etc., and a granular adsorbent is obtained.

  The above meltable core disappears upon firing, so that in addition to the microscopic pores of the activated carbon itself (pores having a diameter of 2 nm or more and less than 50 nm), macroscopic pores (diameter of the diameter) serving as fuel vapor passages. Pores of 50 nm or more and less than 100,000 nm) are formed. That is, the obtained adsorbent 11 has a so-called macroporous structure composed of macroscopic pores, and at the same time, a so-called mesoporous structure composed of microscopic pores for capturing fuel vapor molecules.

  The size of the macroscopic pores of the adsorbent 12 is mainly determined by the activated carbon to be used, but can be adjusted by the ratio of the meltable core or the like.

  FIG. 2 shows a cross-sectional shape of the adsorbent 12 filled in the third chamber 8 as an example. The adsorbent 12 has a hollow cylindrical shape having an outer cylindrical wall 12A and a cross-shaped radial wall 12B provided at the center of the cylindrical wall 12A. And the thickness of each part exists in the range of 0.6 mm or more and 1.5 mm or less. For example, the outer diameter D1 of the cylindrical wall 12A is 4.5 mm, and the inner diameter D2 is 3.0 mm. Further, the thickness d of each of the radial walls 12B is, for example, 0.8 mm, and the thickness (radial thickness) of the cylindrical wall 12A is, for example, 0.8 mm. The axial length L is 4 mm. However, these dimensions have large variations that occur during actual cutting. In addition, the outer diameter of the adsorbent 12 may be spherical, and the radial wall 12B is a cross-shaped shape as described above, a radial shape extending in three directions, or an I-shape extending in two directions, Various shapes are possible.

  FIG. 3 is a table showing various data of five activated carbons A-1, A-2, A-3, B-1, and B-2 used for the adsorbent. As described above, in the above embodiment, the adsorbent A-1 is used as the adsorbents 10 and 11 in the first chamber 6 and the second chamber 7, and the activated carbon A-2 is used as the adsorbent 12 in the third chamber 8. Activated carbon B-2 is used as the adsorbent 13 in the fourth chamber 9.

  Activated carbon A-1, A-3, and B-1 are formed into a hollow columnar or spherical adsorbent as shown in FIG. 4 (A), and the outer diameter (particle size) thereof. Is 2 mm. The activated carbon A-2 is formed into the adsorbent 12 having a hollow cylindrical shape having a cross-shaped radial wall 12B as shown in FIGS. 2 and 4B. As shown in FIG. 4C, the activated carbon B-2 is molded as one large honeycomb-shaped adsorbent 13 inserted and arranged in the fourth chamber 9, and the outer cylindrical wall 13A and A hollow cylindrical shape having a grid-like wall 13B provided inside the cylindrical wall 13A is formed, and the inside of the cylindrical wall 13A is partitioned into a plurality of spaces extending in the longitudinal direction of the passage by the grid-like wall 13B. The outer diameter of the cylindrical wall 13A is 30 mm, and the thickness of the lattice wall 13B is 0.3 mm.

  In order to suppress the airflow resistance of the canister 1, it is advantageous that the adsorbent is large in size. However, when the thickness of the adsorbent 12 (in the case of a simple sphere, the diameter corresponds to the thickness) is increased accordingly, the adsorption / desorption performance as the adsorbent, in particular, the desorption performance is deteriorated. Therefore, in particular, the adsorbent 11 filled in the third chamber 8 and the fourth chamber 9 close to the atmosphere opening is hollow and the thickness of each part is thin.

  In FIG. 3, the volume ratio (%) indicated by the macroscopic pores having a size of less than 500 nm among the macroscopic pores having a diameter of 50 nm or more and less than 100,000 nm in the adsorbents 12 and 13 is, for example, “ISO 15901- It can be measured by the mercury intrusion method specified in “1”. FIG. 5 shows a graph showing the volume ratio of the size of macroscopic pores (macropores) of 50 nm or more and less than 100,000 nm, that is, the size distribution.

Here, the outer diameter of the solid-shaped adsorbent or the thickness of each part of the hollow adsorbent is defined as the thickness of the adsorbent, and among the macroscopic pores having a size of 50 nm or more in the adsorbent, 500 nm If the ratio of the macroscopic pores having a size less than 500 nm is defined as a volume ratio of less than 500 nm, the atmospheric port 5 is formed from the inflow / outflow part side where the charge / purge ports 3 and 4 are provided as shown in FIG. The adsorbent (activated carbon) filled in the plurality of chambers 6 to 9 and the outer diameter and thickness, and the volume ratio of less than 500 nm are as follows toward the open side of the atmosphere.
Adsorbent (activated carbon): A-1 → A-1 → A-2 → B-2
・ Outer diameter (mm): 2 → 2 → 4.5 → 30
・ Thickness (mm): 2.0 → 2.0 → 0.8 → 0.3
-Volume ratio: 27->27->54-> 82
As described above, in this example, the thickness of the adsorbent is gradually reduced from the inflow / outflow side to the atmosphere opening side, and the volume ratio occupied by macroscopic pores of less than 500 nm is increased stepwise. doing. In particular, since the same activated carbon A-1 is used for the first chamber 6 and the second chamber 7 on the inflow / outflow portion side, the thickness of the adsorbent and the volume ratio of less than 500 nm do not change. From the fourth chamber 9 to the fourth chamber 9, the volume ratio of less than 500 nm is gradually increased while gradually reducing the thickness of the adsorbent. As a result, the ventilation resistance is gradually reduced and the desorption performance is improved as it goes to the atmosphere opening side, and as a result, day and night respiratory loss emission can be greatly reduced. Moreover, while increasing the thickness of the adsorbent stepwise toward the inflow / outflow portion, and reducing the volume ratio of less than 500 nm, the adsorbent capacity is ensured while ensuring the desired adsorption performance. The canister can be reduced in size and weight.

  Furthermore, in this embodiment, the outer diameter of the adsorbent filled in the plurality of chambers is increased stepwise from the inflow / outflow portion side to the atmosphere opening side, and the cross-sectional area of the plurality of chambers in the direction perpendicular to the passageway is increased. Is gradually reduced. That is, as shown in FIG. 1, the passage cross-sectional area of the first chamber 6 and the second chamber 7 on the inflow / outflow side is substantially the same, but the passage cross-sectional area of the third chamber 8 is the same as that of the first chamber 6. It is made smaller than the second chamber 7, and the passage sectional area of the fourth chamber 9 is made smaller than that of the third chamber 8. Thus, by gradually reducing the passage cross-sectional area while gradually increasing the outer diameter of the adsorbent toward the atmosphere opening side, the desorption performance is gradually improved toward the atmosphere opening side, Reducing the breathing loss during the day and night, and reducing the outer diameter of the adsorbent stepwise toward the inflow / outflow side, while increasing the cross-sectional area of the chamber toward the atmosphere opening side Thus, the desorption performance can be improved stepwise to further reduce day and night respiratory loss emissions, and the canister can be made more compact by suppressing the capacity of the adsorbent.

FIG. 6 is a characteristic diagram showing day and night respiratory loss emissions (DBL) in the above-described embodiment and the comparative example. The above comparative example is the same as the above example except that the third chamber 8 is filled with an adsorbent using activated carbon B-1. That is, the adsorbent filled in the plurality of chambers 6 to 9 of the comparative example and the outer diameter, thickness, and the volume ratio of less than 500 nm change as follows from the inflow / outflow side to the atmosphere opening side. To do.
Adsorbent (activated carbon): A-1 → A-1 → B-1 → B-2
・ Outer diameter (mm): 2 → 2 → 2 → 30
・ Thickness (mm): 2.0 → 2.0 → 2.0 → 0.3
-Volume ratio: 27->27->20-> 82
In this comparative example, the volume ratio of less than 500 nm is not gradually reduced toward the atmosphere opening side, and the thickness also changes rapidly only between the third chamber 8 and the fourth chamber 9. ing. In such a comparative example, between the third chamber 8 and the fourth chamber 9, since the thickness of the adsorbent is sharply reduced and the volume ratio increases below 500 nm, as shown in FIG. It was confirmed that DBL was significantly deteriorated (increased) as compared with.

FIG. 7 shows a second embodiment of the present invention. This second embodiment differs from the first embodiment only in that an adsorbent 10A using activated carbon A-3 is used for the first chamber 6A. In the second embodiment, the adsorbent filled in the plurality of chambers 6A, 7, 8, 9 and the outer diameter, thickness, and volume ratio of less than 500 nm are from the inflow / outflow side to the atmosphere opening side. It is as follows.
Adsorbent (activated carbon): A-3 → A-1 → A-2 → B-2
・ Outer diameter (mm): 2 → 2 → 4.5 → 30
・ Thickness (mm): 2.0 → 2.0 → 0.8 → 0.3
・ Volume ratio: 52 → 27 → 54 → 82
In the second embodiment, except that the volume ratio of activated carbon A-3 used for the adsorbent 10A filled in the first chamber 6A closest to the inflow / outflow portion side is as high as 52%, less than 500%, As in the first embodiment, the thickness of the adsorbent is gradually reduced from the inflow / outflow portion side to the atmosphere opening side, and the volume ratio occupied by macroscopic pores less than 500 nm is stepwise. It is getting bigger. Since the first chamber 6A is located farthest from the atmospheric port 5 and has little influence on the breathing loss emission during the day and night, the volume ratio of less than 500 nm is added to the first chamber 6A on the inflow / outflow portion side as in the second embodiment. Even when the relatively high adsorbent 10A is used, the DBL performance can be greatly improved as in the first embodiment.

As a modification of the second embodiment, an adsorbent using activated carbon A-3 may also be used in the second chamber 7. In this case, the adsorbent filled in the plurality of chambers 6A, 7, 8, 9 and the outer diameter, thickness, and volume ratio of less than 500 nm are as follows from the inflow / outflow side to the atmosphere opening side. It is.
Adsorbent (activated carbon): A-3 → A-3 → A-2 → B-2
・ Outer diameter (mm): 2 → 2 → 4.5 → 30
・ Thickness (mm): 2.0 → 2.0 → 0.8 → 0.3
-Volume ratio: 52->52->54-> 82
As described above, the present invention has been described based on the specific embodiments. However, the present invention is not limited to the above-described embodiments, and includes various modifications and changes. For example, in the above embodiment, the inside of the canister is divided into four chambers, and the thickness of the activated carbon is gradually reduced from the inflow / outflow side to the atmosphere opening side, and the volume is less than 500 nm. If the ratio is increased stepwise, it may be divided into three or five or more chambers.

1 ... canister 2 ... case 3 ... charge port (inflow part)
4 ... Purge port (outflow part)
5… Atmosphere port (atmosphere opening)
6, 7, 8, 9 ... Chambers 10, 11, 12, 13 ... Adsorbent

Claims (3)

In a canister in which a plurality of chambers arranged in series along a flow direction in a case are filled with an adsorbent, and an inflow / outflow portion of fuel vapor is provided at one end of the flow direction, and an air opening is provided at the other end. ,
The adsorbent has a cylindrical or spherical solid shape or hollow shape,
The outer diameter of the solid adsorbent, or the thickness of each part of the hollow adsorbent is the thickness of the adsorbent,
Among the macroscopic pores having a size of 50 nm or more in the adsorbent, when the ratio occupied by macroscopic pores having a size of less than 500 nm is a volume ratio of less than 500 nm,
From the inflow / outflow side to the atmosphere opening side, the thickness of the adsorbent filled in the plurality of chambers is decreased stepwise, and the volume ratio of less than 500 nm is increased stepwise. A characteristic canister.   2. The canister according to claim 1, wherein an outer diameter of the adsorbent filled in the plurality of chambers is increased stepwise from the inlet / outlet side toward the atmosphere opening side.   3. The canister according to claim 1, wherein a cross-sectional area of the plurality of chambers in a direction perpendicular to the passage is gradually reduced from the inflow / outflow side toward the atmosphere opening side.

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