JP3912048B2 - Evaporative fuel processing equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel vapor processing apparatus represented by a canister used in a vehicle.
[0002]
[Prior art]
In an automobile using gasoline as a fuel, a canister as an evaporative fuel processing device is preferably used in order to mainly prevent the evaporative fuel (HC) in the fuel tank from being released to the atmosphere. A flow path through which air and evaporative gas flow is formed inside the container of the canister, and an air introduction section for introducing air is provided at one end of the flow path, and an evaporative fuel introduction section and evaporative fuel are provided at the other end. A discharge part is provided. When the engine is stopped, etc., the adsorbed fuel adsorbs the evaporated fuel introduced from the evaporative fuel introduction part. At the time of a predetermined purge operation during engine operation, the atmosphere is introduced into the canister by the atmospheric introduction part and adsorbed. The evaporated fuel adsorbed on the body is desorbed and the evaporated fuel is sucked into the intake system of the engine via the evaporated fuel discharge portion and subjected to combustion processing.
[0003]
By the way, the concentration distribution of the evaporated fuel adsorbed on the activated carbon as the adsorbent tends to decrease toward the atmosphere introduction part. However, if the activated carbon is packed in one continuous space in the canister, the adsorption A so-called migration phenomenon occurs in which the evaporated fuel diffuses and moves toward the atmosphere introduction portion having a low concentration as time elapses due to the equilibrium, and the leakage (release) of the evaporated fuel to the atmosphere release portion progresses with time. It becomes easy to happen.
[0004]
In response to such a problem, Japanese Patent Laid-Open No. 10-37812 discloses a relatively small cylindrical second canister 102 on the air introduction part side of the cylindrical first canister 101 as shown in FIG. A structure in which both canisters 101 and 102 are connected in series by a thin pipe 103 is disclosed. In this case, since the activated carbon in both the canisters 101 and 102 is isolated by the pipe 103, the diffusion and movement of the evaporated fuel due to the adsorption equilibrium is substantially interrupted in the pipe 103, and consequently the leak of the evaporated fuel. It is described that can be suppressed.
[0005]
[Problems to be solved by the invention]
However, as in this publication, in the configuration in which two canisters 101 and 102 having different outer shapes are connected by a thin pipe 103, the number of components increases, the cost increases, and the pressure loss in the pipe 103 increases, and the longitudinal length increases. Since it becomes a long shape in the direction, vehicle mountability is not good.
[0006]
One object of the present invention is to provide a novel evaporative fuel processing apparatus capable of effectively preventing leakage of evaporative fuel from the atmosphere introduction portion with a relatively simple and inexpensive structure.
[0007]
[Means for Solving the Problems]
According to the first aspect of the present invention, there is provided an evaporative fuel introduction section and an evaporative fuel in which a flow path is formed therein, an air introduction section for introducing the air is provided at one end of the flow path, and evaporative fuel is introduced at the other end. The evaporative fuel processing apparatus is provided with an evaporative fuel discharge portion that has a cylinder portion extending along a main flow direction that is a longitudinal direction of the flow path. The first adsorbing chamber filled with the first adsorbing body to be adsorbed / desorbed is arranged in series closer to the air introduction part than the first adsorbing chamber, and has higher adsorption / desorption capability than the first adsorbent. It has the 2nd adsorption chamber filled with the 2nd adsorption body, and the isolation layer which isolates so that the 1st adsorption chamber and the 2nd adsorption chamber can flow along a channel section direction.
[0008]
Typically, the evaporative fuel introduction part is connected to a fuel tank of the vehicle, and the evaporative fuel discharge part is connected to an intake system of the internal combustion engine. Then, as the temperature in the fuel tank rises, evaporative gas is introduced into the flow path via the evaporative fuel introduction part, and evaporative fuel contained in this evaporative gas is temporarily adsorbed by the adsorbent, and the remaining air Is discharged to the outside via the air introduction part. Further, at the time of a predetermined purge operation during engine operation, due to the intake negative pressure acting from the evaporated fuel discharge part, the atmosphere is introduced from the atmosphere introduction part into the flow path, and the evaporated fuel adhering to the adsorbent is desorbed, This evaporative fuel is supplied to the intake system together with the atmosphere via the evaporative fuel introduction section, and finally burned in the combustion chamber of the engine. The amount and timing of the evaporated fuel introduced into the intake system are typically adjusted by a purge control valve that opens and closes a purge pipe that connects the evaporated fuel discharge unit and the intake system. Examples of the purge control valve include those that are electrically controlled according to the engine operating state as in the embodiments described later, and mechanical types that forcibly open and close according to the intake negative pressure.
[0009]
And since the 1st adsorption body and the 2nd adsorption body are isolated so that a flow may be carried out by the isolation layer, the migration phenomenon mentioned above will be interrupted substantially in the part of an isolation layer. For this reason, the amount and speed of the evaporated fuel that diffuses and moves from the first adsorption chamber to the second adsorption chamber over time is remarkably suppressed, and the adsorption / desorption of the second adsorbent near the air introduction portion is suppressed. Since the separation capability is relatively high, the leakage of the evaporated fuel to the atmosphere introduction portion can be sufficiently suppressed. In other words, since the expensive second adsorbent having high adsorption / desorption capability is locally disposed near the air introduction part, the leakage of the evaporated fuel is effectively reduced while suppressing the cost. be able to. A structure capable of obtaining such operational effects can be realized with a cylindrical portion having a uniform cross-sectional shape and extending in the main flow direction. For example, as compared with a structure in which two canisters having different shapes are connected by a thin pipe as in the above publication. Thus, the shape is sufficiently simplified and simplified, which is advantageous in terms of layout, and pressure loss is also suppressed.
[0010]
As shown in FIG. 7, in the examples a2 and a3 using two types of activated carbon (adsorbents) having different adsorption / desorption capacities as in the present invention, as compared with the example a1 using only one type of activated carbon. It was confirmed by the evaporation test that exhaust emission was sufficiently reduced. Further, as shown in FIGS. 7 and 8, it was confirmed that the adsorption / desorption capability, that is, the working capacity is increased by increasing the purge air amount introduced into the flow path from the evaporated fuel discharge portion. That is, by increasing the purge air amount together with the present invention, it is possible to further reduce the amount of evaporated fuel remaining in the adsorbent and more reliably prevent the evaporated fuel from leaking. The increase in the purge air amount can be typically realized by expanding the purge operation region using a linear air-fuel ratio sensor or the like.
[0011]
The isolation layer can be formed of, for example, ceramic foam or a simple space layer, but a screen formed of urethane or the like that can be reliably isolated at low cost, that is, a nonwoven fabric is typically used. The first adsorbent is typically composed of a large number of granular activated carbons. The second adsorbent has higher adsorption / desorption capability and higher efficiency than the first adsorbent. Typical examples include honeycomb activated carbon, ceramic adsorbent, high efficiency activated carbon, and high specific heat activated carbon. The adsorption / desorption capacity is also called working capacity or adsorption / desorption efficiency, and corresponds to the ratio of desorption capacity to adsorption capacity. In general, the higher the specific heat, the higher the adsorption / desorption ability.
[0012]
In order to increase the adsorption / desorption capability of the second adsorbent most efficiently, the second adsorbing chamber is preferably formed in a circular column shape or conical shape in the cross-sectional direction of the flow path, and particularly preferably a column shape that is easy to manufacture. To do. Specifically, an inner case is liquid-tightly fitted to the inner peripheral surface of the cylindrical portion, and the second suction chamber is defined by the inner peripheral surface having a cylindrical shape of the inner case. That is, the diameter of the second suction chamber is reduced to a cylindrical shape inside the cylindrical portion using the inner case. In this case, the second adsorbent is preferably a columnar ceramic filter (honeycomb activated carbon) fitted to the inner peripheral surface of the inner case. Further, typically, the central axis of the second adsorption chamber and the central axis of the cylindrical air introduction part are matched. In consideration of cost, adsorption / desorption efficiency, etc., the capacity of the second adsorbent is 2% to 20% or less with respect to the capacity of the remaining adsorbent other than the second adsorbent including the first adsorbent. Preferably there is.
[0013]
As shown in FIG. 9, when the length along the main flow direction of the channel is L and the substantial diameter of the channel cross-sectional area is D, the ratio of the length L to the diameter D of the adsorption chamber, that is, L The higher the / D ratio, the better the adsorption / desorption capability, while the pressure loss increases. The lower the L / D ratio, the lower the pressure loss, but the adsorption / desorption capability decreases. Therefore, while suppressing increase in pressure loss in order to effectively suppress leakage of fuel vapor from the ambient air intake part, from the L / D ratio of the first adsorption chamber L / D ratio of the second adsorption chamber Is also preferably set low. Particularly preferably, the L / D ratio of the second adsorption chamber is set in the range of 2 to 5 so that the pressure loss after the dust durability does not become excessively large, and the L / D ratio of the first adsorption chamber is substantially set. Set to 1.5. When the cross-sectional shape is a rectangle or the like, a circular diameter having the same cross-sectional area corresponds to the substantial diameter.
[0014]
Typically, the cylindrical portion, the cylindrical anti-atmosphere side cylindrical portion arranged in parallel with the cylindrical portion, and the communication portion that integrally connects one side of both cylindrical portions are integrally formed. Have a container. The container is integrally formed of, for example, resin, and has a box shape with a simple overall outer shape. Moreover, the said flow path is extended in the substantially U shape over the inside of both the cylinder parts and a communication part, and the length of a flow path is aimed at in a compact container. A third adsorption chamber filled with a third adsorbent having a lower adsorption / desorption capacity than the second adsorbent is formed in the anti-atmosphere side cylinder. The third adsorbent is composed of a large number of granular activated carbons, for example, like the first adsorbent. Then, on one side of the container, the atmospheric introduction part is formed at the end of the cylinder part, and the evaporated fuel introduction part and the evaporated fuel discharge part are formed at the end part of the anti-atmosphere side cylinder part. Thus, by integrating the air introduction part, the evaporated fuel introduction part, and the evaporated fuel discharge part on one side of the container, the piping work is facilitated and the mounting property to a vehicle or the like is improved.
[0015]
More preferably, a partition wall portion that partitions the evaporated fuel discharge portion and the evaporated fuel introduction portion, a pair of flowable screens that define inner surfaces on both sides in the main flow direction of the third adsorption chamber, and these And a biasing means such as a torsion coil spring or a leaf spring that presses the screen and the third adsorbent against the partition wall. As a result, when evaporative gas flows from the evaporative fuel introduction part to the evaporative fuel discharge part, the evaporative gas surely passes through the third adsorption chamber, and the fuel of the evaporative gas discharged to the evaporative fuel discharge part The concentration is relaxed.
[0016]
More preferably, it extends along the main flow direction from the partition wall portion to the inside of the third adsorption chamber, and a part of the third adsorption chamber is connected to the evaporated fuel introduction portion and the evaporated fuel discharge portion. It has a baffle that divides into a continuous part. In this case, when the evaporative gas flows from the evaporative fuel introduction part to the evaporative fuel discharge part, the evaporative gas flowing through the third adsorption chamber is largely detoured in a substantially U shape by the baffle, and thus to the evaporative fuel discharge part. The fuel concentration of the discharged evaporative gas is further effectively reduced.
[0017]
【The invention's effect】
As described above, according to the present invention, it is possible to effectively prevent leakage of evaporated fuel from the air introduction portion with a relatively simple structure.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Preferred embodiments of the invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing an outline of a vehicle evaporative fuel processing system to which a canister 10 as an evaporative fuel processing apparatus according to the present invention is applied. The canister 10 is filled with adsorbents (21, 23, 31) that adsorb and desorb evaporated fuel (vapor). When the internal combustion engine is stopped, the evaporated gas in the high-temperature and high-pressure fuel tank 1 is introduced into the canister 10 via the charge pipe 2, and the evaporated fuel contained in the evaporated gas is temporarily stored in the adsorbent. It is adsorbed and the remaining air is discharged to the atmosphere via the atmosphere side pipe 3. Further, during a predetermined purge operation during engine operation, the intake negative pressure on the downstream side of the throttle valve 4 a of the intake pipe 4 is applied to the canister 10 via the purge pipe 5. Due to this negative pressure, the atmosphere is introduced from the atmosphere side pipe 3 into the canister 10, the evaporated fuel adhering to the adsorbent is desorbed, and this evaporated fuel is supplied together with the atmosphere to the intake pipe 4 through the purge pipe 5. Finally, the combustion process is performed in the combustion chamber 6. Thus, the amount and timing of the evaporated fuel introduced into the intake system are adjusted by the purge control valve 7 that opens and closes the purge pipe 5. In this embodiment, the purge control valve 7 is electrically controlled by an ECM (engine control unit) 8 according to the engine operating state. Further, this system has a simple structure in which the charge pipe 2 is not provided with a negative pressure cut valve (check valve).
[0019]
Next, a specific structure of the canister 10 according to the first embodiment of the present invention will be described in detail with reference to FIGS. The canister 10 is mainly composed of a container 11 that is integrally formed of a resin material or the like. This container 11 is formed by integrally connecting one end of a cylindrical atmosphere side cylinder portion 12 and a non-atmosphere side cylinder portion 13 which extend in the longitudinal direction with a uniform rectangular cross section by a communication portion 14. It has a simple rectangular parallelepiped box shape. In addition, the mutually opposing side surfaces of the cylindrical portions 12 and 13 are integrally connected by a reinforcing rib 15. A flow path 16 through which air or evaporated fuel flows is formed inside the container 11, and the flow path 16 has a substantially U-shape extending over both the cylinder portions 12 and 13 and the communication portion 14. There is no. Thus, by making the flow path 16 U-shaped, the shortening and size reduction of the container 11 and the lengthening of the flow path 16 are compatible.
[0020]
As shown also in FIG. 1, at one end of the flow path 16, a cylindrical atmosphere introduction portion 17 connected to the atmosphere side pipe 3 is recessed to the inside of the container 11. Further, at the other end of the flow path 16, a cylindrical evaporated fuel introduction part 18 connected to the charge pipe 2 and a cylindrical evaporated fuel discharge part 19 connected to the purge pipe 5 protrude outside the container 11. Is formed. Since the flow path 16 is formed in a substantially U-shape, all of the air introduction part 17, the evaporated fuel introduction part 18, and the evaporated fuel discharge part 19 are on one side of the container 11 (the right side in FIG. 3). Is arranged. Accordingly, all of the pipes 2, 3, and 5 connected to these portions 17 to 19 are gathered on one side of the container 11, so that the piping work is easy and the vehicle mountability is improved.
[0021]
Referring to FIGS. 2 and 3 again, a first adsorbing chamber 22 filled with a first adsorbent 21 that adsorbs and desorbs evaporated fuel inside the atmosphere side cylinder portion 12, and the first adsorbing chamber. 2nd adsorption | suction which is arrange | positioned in series near the atmosphere introduction part 17 of the flow path 16 rather than 22 (right side of FIG. 3), and is filled with the 2nd adsorption body 23 whose adsorption / desorption capability is higher than the 1st adsorption body 21. A chamber 24 is formed. The inner peripheral surface of the first adsorption chamber 22 is defined by the inner wall surface of the atmosphere side cylinder portion 12, and the inner surfaces on both sides in the main flow direction that is the longitudinal direction of the first adsorption chamber 22 are the first screen 25 and the second screen. It is defined by the screen 26. The inner peripheral surface of the second adsorption chamber 24 is defined by a cylindrical inner peripheral surface of an inner case 27 that fits in the air-side cylinder portion 12 in a liquid-tight state, and both sides of the second adsorbent 23 in the main flow direction. The inner surface is defined by a second screen 26 and a third screen 28. A space between the outer peripheral surface of the inner case 27 and the inner peripheral surface of the atmosphere side cylinder portion 12 is sealed with a seal ring or the like. A first torsion coil spring 29 as an urging means is interposed in a compressed state between the inner surface of the container 11 on the communication portion 14 side and the first screen 25, and by this first torsion coil spring 29, The screens 25, 26, the first adsorbent 21, the inner case 27, and the like are held in a state of being pressed toward the atmosphere introduction unit 17 side. In this embodiment, the first adsorbent 21 is composed of a large number of granular activated carbons, and a cylindrical porous ceramic filter (honeycomb activated carbon) that fits as the second adsorbent 23 on the cylindrical inner wall surface of the inner case 27. ) Is used.
[0022]
Thus, the inner case 27 is used to reduce the diameter of the second adsorption chamber 24 to a cylindrical shape having the best adsorption / desorption capability, and the central axis of the second adsorption chamber 24 is set to the atmosphere introduction portion 17. Therefore, the adsorption / desorption capability of the second adsorbent 23 is effectively enhanced with a simple structure and suppressing pressure loss and the like.
[0023]
A third adsorption chamber 32 that is filled with the third adsorbent 31 is formed inside the anti-atmosphere side cylinder portion 13. The third adsorbent 31 has a lower adsorption / desorption capability than at least the second adsorbent 23, and in this embodiment is composed of a large number of granular activated carbons, like the first adsorbent 21. The inner peripheral surface of the third adsorption chamber 32 is defined by the inner wall surface of the anti-atmosphere side cylinder 13, and the inner surfaces on both sides in the main flow direction of the third adsorption chamber 32 are the fourth screen 33 and the It is defined by five screens 34. A second torsion coil spring 35 as an urging means is interposed in a compressed state between the fourth screen 33 and the inner surface of the container 11 on the communication portion 14 side (left side in FIG. 3). The screens 33 and 34 and the third adsorbent 31 are held by the second torsion coil spring 35 in a state of being pressed against the partition wall portion 36 that partitions the evaporated fuel introduction portion 18 and the evaporated fuel discharge portion 19. The partition wall portion 36 is continuously bent from the outer wall portion of the container 11.
[0024]
Further, a thin plate-like baffle 38 that divides a part of the third adsorption chamber 32 into a part communicating with the evaporated fuel introduction part 18 and a part communicating with the evaporated fuel discharge part 19 is provided inside the third adsorption chamber 32 with the flow path 16. It extends along the main flow direction. The baffle 38 is integrally formed to protrude from the protruding end portion of the partition wall portion 36. When the baffle 38 is used in this way, the fifth screen 34 is divided into a pair of divided bodies 34 a and 34 b with the baffle 38 interposed therebetween.
[0025]
The screens 25, 26, 28, 33, and 34 are layered filters that extend in the cross-sectional direction of the flow path 16 and can hold the adsorbent while preventing the adsorbent from falling off. Typically, a nonwoven fabric such as a urethane screen that is relatively inexpensive is used. In particular, the second screen 26 functions as an isolation layer 26 that isolates the first adsorption chamber 22 and the second adsorption chamber 24 at a predetermined interval, in order to more reliably prevent the above-described migration phenomenon. Preferably, the thickness in the main flow direction is set to be longer than that of the other screens 25, 28, 33, 34 as shown in FIG.
[0026]
When the length along the main flow direction of the flow path 16 is L, and the substantial diameter of the cross-sectional area of the flow path 16 is D, the first adsorption chamber 22 and the third adsorption chamber 32 filled with the same activated carbon. Are set to substantially the same L / D ratio. That is, the length L and the diameter D of the first adsorption chamber 22 are set to be approximately half the length L and the diameter D of the third adsorption chamber 32, respectively. On the other hand, the second adsorption chamber 24 has an L / D ratio as compared with the first adsorption chamber 22 and the third adsorption chamber 32 because the diameter is reduced to a circular cross section by the inner case 27. Is set high . Thus, using the inner case 27, the first adsorption chamber 22 and the second adsorption chamber 24 having different L / D ratios can be formed inside the atmosphere-side cylindrical portion 12 having a uniform cross-sectional shape, Compared with the above-mentioned Japanese Patent Application Laid-Open No. 10-37812, the structure is remarkably simplified. More specifically, the L / D ratio of the first adsorption chamber 22 and the third adsorption chamber 32 is set to about 1.5 , and the L / D ratio of the second adsorption chamber 24 is set to a range of 2 to 5. . Further, the capacity of the second adsorbent 23 is set to 2% to 20% or less with respect to the capacity of the remaining first adsorbent 21 and third adsorbent 31.
[0027]
As the temperature in the fuel tank 1 rises, etc., as shown in FIG. 3, while the evaporated gas introduced from the evaporated fuel introducing portion 18 flows in the flow path 16 in the direction of the arrow A1, the evaporation in the evaporated gas is performed. The fuel is adsorbed by the adsorbents 31, 21, 23, and the remaining air is discharged from the air introduction unit 17. Since the evaporating gas passes through the third adsorbent 31, the first adsorbent 21 and the second adsorbent 23 in this order, the adsorption concentration of the second adsorbent 23 is generally the lowest, and this second adsorbent. Since the adsorbing / desorbing capacity 23 is set to be relatively high, the evaporated fuel is hardly discharged to the atmosphere introduction unit 17 without being adsorbed.
[0028]
Further, as described above, the concentration gradient of the evaporated fuel also tends to decrease toward the atmosphere introduction unit 17 in the adsorbent filled in one continuous adsorption chamber. Here, it is known that the evaporative fuel tends to diffuse and move toward the atmosphere introduction portion where the concentration is low due to the so-called migration phenomenon in which the fuel concentration in the adsorbent is balanced over time. However, in this embodiment, since the first adsorbent 21 and the second adsorbent 23 are separated by the second screen 26, the migration phenomenon is substantially divided at the second screen 26, and the second The amount of diffusion and movement of the evaporated fuel to the adsorbent 23 is remarkably suppressed, and as a result, the leakage of fuel to the atmosphere introduction unit 17 can be prevented more reliably.
[0029]
Next, with reference to FIG. 4 and FIG. 5, the exhaust emission impact due to the evaporated gas flowing from the evaporated fuel introduction section 18 to the evaporated fuel discharge section 19 will be described. In the configuration in which the check valve is not provided in the charge pipe 2 as in the present embodiment, the evaporated gas may flow from the evaporated fuel introduction portion 18 toward the evaporated fuel discharge portion 19 during engine operation.
[0030]
Here, as in the comparative example shown in FIG. 5, when the second torsion coil spring 35 ′ is provided on the evaporative fuel introduction part 18 or the evaporative fuel discharge part 19, contrary to the present embodiment, the evaporative fuel introduction is performed. A space portion K is formed between the partition wall portion 36 that partitions the portion 18 and the evaporated fuel discharge portion 19 and the fifth screen 34 ′. Therefore, the evaporative gas introduced from the evaporative fuel introduction part 18 hardly passes through the inside of the third adsorption chamber 32 ', and directly passes through the space part K as shown by the arrow A3. Therefore, the fuel concentration of the evaporative gas introduced into the intake system becomes high, the air-fuel ratio is inadvertently rich, and the exhaust performance called the so-called exhaust emission impact tends to be lowered.
[0031]
On the other hand, in the present embodiment, as shown in FIG. 4, the screens 33 and 34 and the third adsorbent 31 are pressed against the partition wall 36 by the second torsion coil spring 35, and the third Since a part of the adsorption chamber 32 is partitioned by the baffle 38, the vaporized gas introduced from the vaporized fuel introduction portion 18 is reliably introduced into the third adsorption chamber 32 through the fifth screen 34 as indicated by an arrow A2. At the same time, the baffle 38 largely detours in a U shape and flows to the evaporated fuel discharge portion 19. For this reason, the amount of the evaporated fuel in the evaporated gas adsorbed by the third adsorbent 31 is increased, the fuel concentration of the evaporated gas introduced into the intake system is sufficiently relaxed (suppressed), and the exhaust emission impact is sufficiently increased. Can be suppressed.
[0032]
FIG. 6 shows a second embodiment. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted. In the second embodiment, the second adsorption chamber 24 is further divided into a first divided chamber 41 and a second divided chamber 42 by a separation layer 40 that can flow, such as a urethane screen. 42 are filled with adsorbents 43 and 44 having higher adsorption / desorption capabilities than the first adsorbent 21 and the third adsorbent 31, respectively. For example, the first division chamber 41 is filled with high specific heat activated carbon, and the second division chamber 42 is filled with a cylindrical ceramic filter. Thus, by further dividing the second adsorption chamber 24 with the isolation layer 40, the above-mentioned migration phenomenon can be more reliably suppressed.
[0033]
In addition, this invention is not limited to embodiment mentioned above, A various change and deformation | transformation are included. For example, with respect to the first embodiment, the second screen 26 as the isolation layer has a thickness substantially equal to or shorter than that of the other screens 25, 28, 33, 34, the baffle 38 is omitted, or the second adsorbent 23 Alternatively, high specific heat activated carbon or high efficiency activated carbon may be used.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an evaporated fuel processing system for an internal combustion engine to which a canister as an evaporated fuel processing apparatus according to the present invention is applied.
FIG. 2 is a perspective view showing a perspective view of the inside of a canister as the evaporated fuel processing apparatus according to the first embodiment.
3 is a cross-sectional view of the canister of FIG.
4 is a cross-sectional view of the canister of FIG.
FIG. 5 is a cross-sectional view of a canister according to a comparative example.
FIG. 6 is a cross-sectional view showing a canister as an evaporative fuel processing apparatus according to a second embodiment.
FIG. 7 is a characteristic diagram showing emissions of Examples a2 and a3 using two types of activated carbons having different adsorption / desorption capacities and Example a1 using one type of activated carbon.
FIG. 8 is a characteristic diagram showing a change in working capacity with respect to the purge air amount.
FIG. 9 is a characteristic diagram showing changes in adsorption / desorption ability and pressure loss with respect to the L / D ratio.
FIG. 10 is a configuration diagram showing a fuel vapor processing apparatus as a conventional example.
[Explanation of symbols]
11 ... Container 12 ... Atmosphere side cylinder part (cylinder part)
DESCRIPTION OF SYMBOLS 13 ... Anti-atmosphere side cylinder part 14 ... Communication part 16 ... Flow path 17 ... Atmosphere introduction part 18 ... Evaporated fuel introduction part 19 ... Evaporated fuel discharge part 21 ... 1st adsorption body 22 ... 1st adsorption chamber 23 ... 2nd adsorption body 24 ... second adsorption chambers 25, 28, 33, 34 ... screen 26 ... second screen (isolation layer)
27 ... Inner case 29, 35 ... Torsion coil spring (biasing means)
31 ... 3rd adsorption body 32 ... 3rd adsorption chamber 36 ... Partition wall part 38 ... Baffle

Claims (11)

A flow path is formed inside, an air introduction part for introducing air to one end of the flow path is provided, and an evaporative fuel introduction part for evaporating fuel to be introduced to the other end and an evaporative fuel discharge part for discharging the evaporative fuel In the evaporative fuel processing apparatus provided with
It has a cylindrical portion extending along the main flow direction of the flow path,
The cylindrical portion is arranged in series with a first adsorbing chamber filled with a first adsorbent for adsorbing and desorbing evaporated fuel, and closer to the air introduction portion than the first adsorbing chamber. A second adsorbing chamber filled with a second adsorbent having a high adsorption / desorption capability, an isolation layer for separating the first adsorbing chamber and the second adsorbing chamber along the flow path cross-sectional direction, have a,
The second suction chamber is defined by the inner peripheral surface of the inner case that is fitted in a liquid-tight manner to the inner peripheral surface of the cylindrical portion, and the diameter of the second suction chamber is smaller than that of the first suction chamber. The evaporative fuel processing apparatus characterized by the above-mentioned. Second adsorber above SL is, the fuel vapor processing apparatus according to claim 1, characterized in that a cylindrical ceramic filter to be fitted to the inner circumferential surface of the inner case.   The evaporative fuel processing apparatus according to claim 1, wherein the isolation layer is a urethane screen.   The evaporative fuel processing device according to claim 1, wherein the first adsorbent is made of granular activated carbon. When the length along the main flow direction of the flow path is L and the substantial diameter of the cross-sectional area of the flow path is D,
Evaporative fuel processing apparatus according to any one of claims 1 to 4, characterized in that it is set lower than the L / D ratio L / D ratio of the first adsorption chamber and the second adsorption chamber. 6. The evaporative fuel processing apparatus according to claim 5, wherein the L / D ratio of the second adsorption chamber is set to 2 to 5, and the L / D ratio of the first adsorption chamber is set to approximately 1.5. . A container in which the cylindrical portion, a cylindrical anti-atmosphere side cylindrical portion provided in parallel with the cylindrical portion, and a communication portion that integrally connects one side of both cylindrical portions are integrally formed; ,
A third adsorbent in which the flow path extends in a substantially U shape inside both the cylinder part and the communication part, and has a lower adsorption / desorption capacity than the second adsorbent in the anti-atmosphere side cylinder part A third adsorption chamber filled with
The air introduction part is formed at the end of the cylinder part on one side of the container, and the evaporated fuel introduction part and the evaporated fuel discharge part are formed at the end part of the anti-atmosphere side cylinder part. The evaporative fuel processing apparatus according to any one of claims 1 to 6.   A partition wall that partitions the evaporative fuel discharge portion and the evaporative fuel introduction portion, a pair of flowable screens that define inner surfaces on both sides in the main flow direction of the third adsorption chamber, and the screen and the third The evaporated fuel processing apparatus according to claim 7, further comprising an urging unit that presses the adsorbent against the partition wall.   Extending along the main flow direction from the partition wall to the inside of the third adsorption chamber, a part of the third adsorption chamber, a part connected to the evaporated fuel introduction part, a part connected to the evaporated fuel discharge part, The evaporative fuel processing apparatus according to claim 8, further comprising a baffle that is partitioned into two. 2. The evaporative fuel processing apparatus according to claim 1, wherein the second adsorption chamber in the inner case is divided into a first divided chamber and a second divided chamber. It has other screens defining inner surfaces on both sides in the main flow direction of the first adsorption chamber and the second adsorption chamber together with the isolation layer, and in the main flow direction of the isolation layer as compared with these other screens. The evaporative fuel processing apparatus according to claim 1, wherein the thickness is set to be long.

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