JP2009250059A - Canister - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a canister that allows evaporation fuel which has been adsorbed by an adsorbent to be diffused into an atmosphere while a vehicle is stopped, in other words, enables effective reduction in blow-by amount. <P>SOLUTION: A canister contains adsorbents 28, 29 for adsorbing and desorbing evaporation fuel therein, and includes a tank port 13 communicating with a fuel tank, and an atmosphere port 14 communicating with the atmosphere. an adsorption chamber 18 at a tank port side at the upstream side partitioned by a partition wall 16, and an adsorption chamber 19 at an atmosphere port side at the downstream side are arrayed in series relative to a flow direction of the evaporation fuel. The canister is characterized in that at least a portion of the adsorption chamber 19 at the atmosphere port side inclines toward the atmosphere port 14, thereby gradually reducing the sectional area thereof, and an L/D ratio near the atmosphere port 14 in the adsorption chamber 19 at the atmosphere port side is larger than an L/D ratio at the upstream therefrom. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a canister for an evaporative fuel processing apparatus in which an adsorbent is housed and evaporative fuel generated from a fuel tank of an automobile is prevented from being released into the atmosphere.

  Conventionally, evaporative fuel generated by volatilization of gasoline fuel stored in the fuel tank when the vehicle is stopped is adsorbed to an adsorbent such as activated carbon stored in the adsorption chamber of the canister case, and the evaporated fuel is diffused into the atmosphere. There is a canister for the evaporative fuel processing apparatus that prevents this from happening. The canister is provided with a tank port communicating with the upper part of the fuel tank, an atmospheric port whose tip is open to the atmosphere, and a purge port through which evaporated fuel desorbed (purged) from the adsorbent flows. It has been. Evaporated fuel generated when the temperature of the fuel tank rises when the engine is driven or when the vehicle is stopped is adsorbed by the adsorbent while flowing from the tank port and flowing in the adsorption chamber toward the atmospheric port. Evaporated fuel is prevented from being released into the atmosphere. The evaporated fuel adsorbed by the adsorbent is desorbed (purged) by introducing air from the air port by an intake pipe negative pressure when the engine is driven and a suction pump that is driven and controlled independently of the engine drive. The adsorbent is regenerated.

  As described above, the canister is provided to adsorb the evaporated fuel generated from the fuel tank and prevent it from being diffused into the atmosphere, but the evaporated fuel adsorbed by the adsorbent when the vehicle is stopped is in the atmosphere. There may be a so-called blow-through phenomenon that is diffused from the port to the atmosphere. Here, the concentration distribution of the evaporated fuel adsorbed on the adsorbent tends to be highest on the tank port side and gradually lower toward the atmospheric port side. As the migration phenomenon that diffuses and moves toward the low air introduction portion progresses, the blow-through phenomenon easily occurs. Further, if the evaporated fuel remains without being desorbed from the adsorbent during the purge, the remaining evaporated fuel is pushed to the atmospheric port side by new evaporated fuel that sequentially flows from the fuel tank, and diffuses and moves. However, the blow-through phenomenon is likely to occur. Eventually, the evaporated fuel is adsorbed on the tank port side, and the evaporated fuel that cannot be adsorbed moves to the atmosphere port side, and the evaporated fuel remaining on the activated carbon on the atmosphere port side is desorbed by this evaporated fuel, causing a blow-through phenomenon. Arise. Therefore, the amount of blown-through tends to increase as the amount of remaining fuel near the atmospheric port increases. In other words, if the amount of evaporated fuel remaining in the atmospheric port can be reduced, the amount of blow-through can also be reduced.

  The diffusion of the evaporated fuel to the downstream side can be suppressed by arranging a screen member such as a nonwoven fabric at an appropriate position in the adsorption chamber. However, even if the evaporated fuel is purged from the adsorbent, it is almost impossible to completely desorb all the evaporated fuel from the adsorbent, and the remaining evaporated fuel is inevitable. However, as the ratio of the length L of the adsorption chamber along the flow direction of the evaporated fuel and the effective sectional diameter (substantial diameter of the sectional area) D of the adsorption chamber, that is, the L / D ratio is higher, the adsorption / desorption capability is higher. It is known to improve and reduce the remaining amount, and the effect has been confirmed by the present inventors (details will be described later). Patent Document 1 and Patent Document 2 are examples of canisters that reduce the blow-by amount while paying attention to the L / D ratio.

  In Patent Document 1, the higher the L / D ratio, the better the adsorption / desorption ability, but the pressure loss increases. Therefore, the adsorbent made of general granular activated carbon is disposed in the most downstream adsorption chamber facing the atmospheric port. The L / D ratio of the most downstream adsorption chamber is made smaller than the L / D ratio of the adsorption chamber on the upstream side while accommodating the honeycomb-shaped activated carbon having a higher adsorption / desorption capability than the above. Specifically, the L / D ratio in the vicinity of the atmospheric port is 1.5, and the upstream L / D ratio is 2 to 5. In the present invention, upstream and downstream are based on the direction in which the evaporated fuel generated from the fuel tank flows from the tank port to the atmosphere port. The honeycomb activated carbon is accommodated in the inner case, and the inner case is disposed in the adsorption chamber at the most downstream side. Since the inner case has a predetermined thickness, the effective cross-sectional diameter of the inner case and the effective cross-sectional diameter of the suction chamber upstream from this change stepwise. In Patent Document 2, in order to increase the L / D ratio in the vicinity of the atmospheric port, cartridges designed for various L / D ratios can be installed and replaced immediately below the atmospheric port. The cartridge is attached to a cylindrical wall provided in a step shape on the inner wall of the canister case.

JP 2003-3914 A JP 2004-1000069 A

  However, in Patent Document 1, the L / D ratio in the vicinity of the atmospheric port is made smaller than the L / D ratio on the upstream side, and there remains a problem in fundamentally reducing the blow-by amount. On the other hand, in Patent Document 2, since the L / D ratio in the vicinity of the atmospheric port is made larger than the L / D ratio on the upstream side, an effect of reducing the blow-by amount can be expected to some extent. However, in Patent Document 2, since the effective sectional diameter D of the adsorption chamber changes stepwise through the step, pressure loss due to the step occurs in addition to reducing the effective sectional diameter D. In this case, there is a concern that the amount of fuel vapor in the vicinity of the air port increases due to the decrease in the air introduction amount, and the amount of blow-through increases. In addition, desorption at a site with a large effective cross-sectional diameter D near the stepped portion becomes difficult, and there is a concern that the adsorptivity deteriorates. The same applies to Patent Document 1 in that the effective cross-sectional diameter D of the adsorption chamber changes stepwise through a step.

  In addition, the present inventors have found that the amount of blowout can be reduced by adding a new adsorption chamber to the conventional canister, and have completed the present invention. On the other hand, in Patent Document 2, various cartridges can be installed and replaced. However, this is only performed in a conventional canister and does not further add a new adsorption chamber. Patent Document 1 does not have a configuration like an additional adsorption chamber.

  Accordingly, the present invention solves the above-mentioned problems, and the object of the present invention is to effectively evaporate the evaporated fuel adsorbed by the adsorbent into the atmosphere while the vehicle is stopped, that is, to effectively reduce the amount of blow-through. A canister that can be reduced easily.

  The present invention contains an adsorbent that adsorbs and desorbs evaporated fuel inside, a tank port that communicates with a fuel tank, and an atmospheric port that communicates with the atmosphere, and an upstream tank port that is partitioned by a partition wall In the canister in which the side adsorption chamber and the downstream atmospheric port side adsorption chamber are arranged in series with respect to the flow direction of the evaporated fuel, the first mode is along the flow direction of the evaporated fuel in the atmospheric port side adsorption chamber. At least a predetermined range on the atmosphere port side is inclined toward the atmosphere port, and the sectional area gradually decreases.

  Also, an adsorbent that adsorbs and desorbs evaporated fuel is housed inside, and is equipped with a tank port that communicates with the fuel tank and an atmospheric port that communicates with the atmosphere. In the canister in which the chamber and the downstream atmospheric port side adsorption chamber are arranged in series with respect to the flow direction of the evaporated fuel, as a second form, an intermediate portion of the atmospheric port side adsorption chamber is inclined toward the atmospheric port side. However, the sectional area gradually decreases, and the sectional area on the atmospheric port side in the atmospheric port side adsorption chamber is smaller than the sectional area upstream of the intermediate portion.

  That is, when the first and second modes are combined, an adsorbent that adsorbs and desorbs the evaporated fuel is accommodated therein, and includes a tank port that communicates with the fuel tank, and an atmospheric port that communicates with the atmosphere. In the canister in which the upstream tank port side adsorption chamber and the downstream atmospheric port side adsorption chamber partitioned by the above are arranged in series with respect to the flow direction of the evaporated fuel, at least a part of the atmospheric port side adsorption chamber is In addition, the cross-sectional area gradually decreases without a step by being inclined toward the atmospheric port side, and the cross-sectional area on the atmospheric port side in the atmospheric port-side adsorption chamber is smaller than the cross-sectional area upstream thereof. It is characterized by that. In the present invention, upstream and downstream are based on the direction in which the evaporated fuel generated from the fuel tank flows from the tank port to the atmosphere port.

  It is preferable that the atmospheric port side adsorption chamber is further divided into a plurality of adsorption chambers at a cross-sectional area changing portion where the sectional area of the atmospheric port side adsorption chamber is gradually reduced.

  That the cross-sectional area of the adsorption chamber is small means that the effective cross-sectional diameter (substantial diameter of the cross-sectional area) of the adsorption chamber is small, that is, the diameter is reduced. When the length of the adsorption chamber along the flow direction of the evaporated fuel is L and the effective sectional diameter of the adsorption chamber is D, the L / D ratio of the most downstream adsorption chamber facing the atmospheric port is L / D ratio of the other adsorption chambers. It is characterized by being larger than the D ratio. At this time, it is preferable to store an adsorbent having superior desorption capability, that is, having a weak adsorption holding force, in the most downstream adsorbing chamber facing the atmospheric port, compared to the adsorbing materials accommodated in other adsorbing chambers.

  As a third embodiment of the present invention, an additional adsorption chamber may be provided in communication with the outside of the most downstream adsorption chamber in the canister, and the atmospheric port may be provided in the additional adsorption chamber. At this time, it is preferable that the additional adsorption chamber has a structure having better air permeability than the other adsorption chambers.

  According to the present invention, at least a predetermined range or an intermediate portion on the atmosphere port side in the atmosphere port side adsorption chamber, that is, a cross-sectional area of at least a part of the atmosphere port side adsorption chamber gradually inclines toward the atmosphere port (downstream). The cross-sectional area changing portion has no step where the cross-sectional area changes suddenly. Therefore, the adsorption / desorption ability of the adsorbent can be improved while avoiding pressure loss due to a step. In addition, although pressure loss due to the reduction in the cross-sectional area of the adsorption chamber occurs, the portion having a small cross-sectional area is limited to only the minimum necessary portion near the atmosphere port, so that it is possible to avoid pressure loss in the entire canister.

  In addition, by setting the L / D ratio of the most downstream adsorption chamber facing the atmospheric port to be larger than the L / D ratios of the other adsorption chambers, the remaining amount of evaporated fuel in the vicinity of the atmospheric port is reduced, and the blow-through amount is also reduced. Can be reduced. This is because the cross-sectional area is small, the amount of air passing through the unit area is increased, and the flow rate of the purge air is increased. By increasing the flow rate of the purge air, the evaporated fuel adsorbed by the adsorbent is easily desorbed, and the desorption speed is increased. In addition, when the amount of air passing through the unit area increases, the amount of desorption increases and the remaining amount decreases. This is the principle that by reducing the remaining amount of evaporated fuel, the amount of evaporated fuel diffusing to the atmosphere port side is reduced and the amount of blow-through is reduced.

  If the atmospheric port side adsorption chamber is partitioned into a plurality of adsorption chambers, the diffusion and movement of the evaporated fuel from the upstream adsorption chamber to the most downstream adsorption chamber facing the atmospheric port can be suppressed, so the amount of blow-through can be further reduced. . In addition, if the air port side adsorption chamber is partitioned into a plurality of adsorption chambers in the cross-sectional area changing portion, the L / D ratio of each adsorption chamber can be designed in stages, so that the canister design that focuses on reducing the blow-by amount can be designed. This is easy, and is also advantageous when different adsorbents are accommodated in the adsorption chambers having different adsorption / desorption capabilities based on the L / D ratio. In this case, if an adsorbent having better desorption capability than the adsorbents accommodated in other adsorbing chambers, that is, an adsorbent having a weak adsorption holding force, is accommodated in the most downstream adsorbing chamber facing the atmospheric port, it faces the atmospheric port The amount of evaporated fuel remaining in the most downstream adsorption chamber can be further reduced.

  If the additional adsorption chamber is provided in the outside of the canister, the amount of blow-through can be further reduced. Further, if the additional adsorption chamber is provided outside the most downstream adsorption chamber serving as the canister outlet, there is little problem of the canister mounting space, and it is provided in communication with the outside of the most downstream adsorption chamber having a large L / D ratio. Since the additional adsorption chamber inevitably has a high L / D ratio, the effect of this is great. In addition, an increase in ventilation resistance is inevitable by providing an additional adsorption chamber, but if the ventilation of the additional adsorption chamber is better than that of other adsorption chambers, the ventilation resistance will increase significantly. Can be avoided.

<DBL test>
Hereinafter, embodiments of the present invention will be described with reference to the drawings as appropriate. However, the present invention is not limited thereto, and various modifications can be made without departing from the gist of the present invention. First, before describing specific embodiments of the present invention, the results of measuring blow-by characteristics according to the L / D ratio, which is the basic principle of the present invention, by a DBL (Diurnal Breathing Loss) test will be described. The DBL test is a test that measures the evaporation assuming that the vehicle is parked outdoors all day and night and is exposed to changes in atmospheric temperature, and is also referred to as an all-day storage discharge test. The DBL test is performed by installing a vehicle in a sealed housing for Evaporative Determination (SHED), which is a sealed measurement chamber that does not adsorb HC and does not leak out.

  In the DBL test, three types of simulated canisters in which 400 cc each of BAX-1100 activated carbon manufactured by Mead West Beco Co., Ltd. were filled in a cylindrical case made of hard vinyl chloride were measured in a horizontal position. Table 1 shows the specifications of each simulated canister.

  For each simulated canister 1 to 3, based on the §86, 90 to 133DBL test of the California Evaporation Regulations, the adsorption / desorption is repeated several times to stabilize the residual gas amount, and then the breakthrough state is established. After purging with a predetermined amount of air, the amount of blow-through when the butane was supplied at an ambient temperature of 25 ° C. after being left for 19 hours was measured. “Breakthrough” means that the adsorbed component permeates without being adsorbed because the adsorption capacity is exceeded. As the supply butane, a mixed gas of 50 vol% butane + 50 vol% nitrogen was supplied at a flow rate of 15 g / h. The air supply amount at the time of purging was set to 36.5L, 44L, and 60L, and the purge conditions for each of the simulated canisters 1 to 3 are shown in Table 2. Note that the numbers ◯ -Δ in Table 2 mean that “the L / D ratio ◯ canister × has been purged with ΔL”.

  The results of the DBL test are shown in FIG. From the comparison of 2.9-60 (♦), 6.4-60 (*), and 32.6-60 (x) in which the air supply amount is the same 60 L in the result of FIG. The larger the ratio, the smaller the blow-through amount. Conversely, the smaller the L / D ratio, the greater the amount of blow-through and the higher the rate of increase in the amount of blow-through over time. This is considered to be because the amount of purge gas (air) passing through the unit area increases as the L / D ratio increases, resulting in an increase in the amount of butane desorption and a decrease in the amount of remaining butane. Further, as the L / D ratio is larger, breakthrough in which the amount of blow-through rapidly increases is less likely to occur, and the adsorption capacity is increased. Thereby, it has also confirmed that adsorption capacity became high, so that L / D ratio was large. On the other hand, from the comparison between 6.4-60 (*) and 6.4-44 (▲) and the comparison between 32.6-60 (x) and 32.6-36.5 (■), the same L In the case of the / D ratio, the larger the purge gas supply amount, the smaller the blow-through amount, and the smaller the purge gas supply amount, the larger the blow-through amount. This is because the butane desorption amount increases as the purge gas supply amount increases. However, 6.4-44 (▲), which has a relatively small purge gas supply amount, has a smaller blow-through amount and a considerably smaller purge gas supply amount than 2.9-60 (♦), which has a smaller L / D ratio. .6-36.5 (■) also has a smaller L / D ratio than 6.4-60 (*), 6.4-44 (▲), and 2.9-60 (♦). There were few. Accordingly, it was confirmed that the effect of reducing the blow-by amount was more influenced by the L / D ratio than the purge gas supply amount. That is, it was confirmed that by increasing the L / D ratio, it was possible to efficiently reduce the blow-by amount.

<Influence test by residual amount>
Next, a measurement study was performed on the change in the amount of blow-through depending on the amount of butane remaining. The simulated canisters 1 to 3 used in the DBL test were purged under the same conditions as described above until the residual concentration of butane reached 20%, 5%, 0.1%, and 0%. The blow-through amount when butane was supplied under the same conditions as in the DBL test was measured. The result is shown in FIG.

  As can be seen from the results of FIG. 2, the higher the butane residual concentration, the greater the amount of blow-through and the faster the time to overbreak. As a result, it was found that the amount of blow-through can be reduced as the amount of evaporated fuel remaining in the vicinity of the atmospheric port is small. Further, looking at each butane residual concentration, in all the butane residual concentrations, the higher the L / D ratio, the smaller the amount of blow-through. From this, it was confirmed that if the L / D ratio is increased, the effect of reducing the blow-by amount is high. Based on these results, various embodiments of the present invention will be described below.

Example 1
FIG. 3 shows a first embodiment of the present invention. As shown in FIG. 3, the canister 1 of the first embodiment is installed in an evaporative fuel processing device generated from a fuel tank of an automobile. The canister case 10 is made of a synthetic resin and has a hollow cylindrical shape. The canister case 10 has a synthetic resin cap 11 that closes the bottom opening of the canister case 10, and an adsorbent made of activated carbon or the like capable of adsorbing and desorbing evaporated fuel is accommodated inside the canister case 10. The canister case 10 and the cap 11 are joined by, for example, vibration welding or adhesion. On the upper surface of the canister case 10, a cylindrical tank port 13 that serves as an evaporative fuel introduction portion and a cylindrical air port 14 that communicates with the atmosphere and serves as an inlet / outlet of the atmosphere (air) penetrate the inside and outside of the canister case 10. It is integrally formed. A cylindrical purge port 15 through which the desorbed evaporated fuel flows is integrally formed between the tank port 13 and the atmospheric port 14 so as to penetrate inside and outside. Although not shown, the tank port 13 communicates with the upper part of the fuel tank via an evaporation line. The purge port 15 communicates with an intake pipe of an engine (internal combustion engine) via a purge line, or communicates with a suction pump provided on the purge line and driven and controlled independently of engine driving.

  A long partition wall 16 extending vertically from the upper surface of the canister case 10 to the vicinity of the cap 11 is integrally formed between the atmospheric port 14 and the purge port 15. The inside of the canister 1 is largely divided into an adsorption chamber 18 on the tank port 13 side and an adsorption chamber 19 on the atmosphere port 14 side by the partition wall 16, and the tank port 13, the purge port 15, and the atmosphere are contained in the canister 1. A U-shaped channel that communicates with the port 14 via the lower portion of the partition wall 16 is formed. Therefore, the adsorption chamber 18 on the tank port 13 side and the adsorption chamber 19 on the atmospheric port 14 side are in a series relationship with the flow direction of the evaporated fuel. Further, the atmospheric port side adsorption chamber 19 is divided into two adsorption chambers 20 and 21 through a screen 23 having air permeability. That is, in the canister 1 according to the first embodiment, the first adsorption chamber 18 on the tank port 13 side from the upstream side is based on the direction in which the evaporated fuel generated from the fuel tank flows from the tank port 13 to the atmosphere port 14 side. And a second adsorption chamber 20 upstream of the atmospheric port 14 (downward in the vertical direction) and a third adsorption chamber 21 downstream of the atmospheric port 14 (upward in the vertical direction). The lengths of the second adsorption chamber 20 and the third adsorption chamber 21 (dimensions along the flow direction of the evaporated fuel) are substantially the same, and the adsorption chamber 19 on the atmosphere port 14 side is substantially equally spaced vertically by the screen 23. It is divided in two. A short auxiliary partition wall 17 extending from the upper surface of the canister case 10 toward the cap 11 is also integrally formed between the tank port 13 and the purge port 15.

  The first and second adsorbing chambers 18 and 20 are filled with an adsorbing material 28, and the third adsorbing chamber 21 has a desorption capacity, that is, a desorption capacity that is higher than the adsorbing materials 28 in the other adsorbing chambers 18 and 20. An adsorbent 29 having a weak adsorbing and holding force is accommodated and filled. The adsorbent tends to have a stronger evaporative fuel holding power (adsorbing power) as the pore diameter is smaller, and the evaporative fuel adsorbed holding power is inversely proportional to the pore diameter of the adsorbent. On the other hand, the pore volume of the adsorbent and the remaining amount of evaporated fuel are in a proportional relationship. Using this characteristic, the adsorbent 29 having excellent desorption capability has a larger average pore diameter and pore volume than the adsorbent 28 accommodated in the first and second adsorption chambers 18 and 20. Is big. In other words, the adsorbent 28 accommodated in the first and second adsorption chambers 18 and 20 has an average pore diameter smaller than that of the adsorbent 29 accommodated in the third adsorption chamber 21. The pore volume is small and the adsorption holding force is stronger than that of the adsorbent 29. Alternatively, as the adsorbent 29, a honeycomb-like activated carbon that has better adsorption / desorption ability than granular activated carbon can be used.

  A breathable filter 24 is disposed above and below the first adsorption chamber 18 and the atmospheric port side adsorption chamber 19, and a plate or mesh having a large number of pores is provided on the lower surface of the filter 24 below. The metal plate 25 which consists of is arranged. Further, a coil spring 26 is disposed between the plate 25 and the cap 11, and the adsorbent is urged by the coil spring 26 to always upward (toward the ports 13 to 15). 28 and 29 are securely held. The same screen 23 and filter 24 that divide the second adsorption chamber 20 and the third adsorption chamber 21 on the air port 14 side can be used, and are made of, for example, a synthetic resin nonwoven fabric or urethane foam. A space between the cap 11 and the plate 25 is a communication chamber 22.

  A major feature of the first embodiment is that the outer wall of the third adsorption chamber 21 is inclined toward the atmospheric port 14, so that the downstream side of the atmospheric port side adsorption chamber 19 is substantially half (substantially upper half in the vertical direction). Is gradually reduced toward the atmospheric port 14. That is, the canister 1 of the first embodiment belongs to the first mode of the present invention, and at least a predetermined range on the atmosphere port 14 side along the flow direction of the evaporated fuel in the atmosphere port side adsorption chamber 19 is inclined toward the atmosphere port 14. The cross-sectional area gradually decreases. Therefore, the screen 23 partitioned into the second adsorption chamber 20 on the upstream side and the third adsorption chamber 21 on the most downstream side is arranged in the cross-sectional area changing portion in the atmospheric port 14 side adsorption chamber. The inside of the port side adsorption chamber 19 is partitioned into a plurality of adsorption chambers at the cross-sectional area changing portion. Thus, if the length of the adsorption chamber along the flow direction of the evaporated fuel is L, and the effective sectional diameter of the adsorption chamber is D, the L / D ratio of the third adsorption chamber 21 at the most downstream facing the atmospheric port 14 is It is larger than the L / D ratio of the other adsorption chambers 18 and 20. In addition, the level | step difference is not formed in the outer wall of the 2nd and 3rd adsorption | suction chamber 20 * 21.

  Next, the operation of the canister 1 according to the first embodiment will be described. When the temperature of the fuel tank is raised due to a high temperature atmosphere when the vehicle is stopped or engine drive heat when the vehicle is running, the temperature of gasoline stored in the fuel tank is also raised and a large amount of evaporated fuel is generated. The evaporated fuel generated in the fuel tank is introduced into the canister 1 from the tank port 13, and passes through the first adsorption chamber 18, the communication chamber 22, the second adsorption chamber 20, and the third adsorption chamber 21 in this order. It flows in a U-shape toward the atmospheric port 14 and is adsorbed by the adsorbents 28 and 29 accommodated in the adsorption chambers 18 to 21 during that time. When the inside of the canister 1 becomes negative pressure by the intake pipe negative pressure or the suction pump, the atmosphere (outside air) is sucked from the atmosphere port 14 and the evaporated fuel adsorbed by the adsorbents 28 and 29 is desorbed (purged) It flows in the opposite direction to the above and is discharged from the purge port 15. At this time, since the L / D ratio of the third adsorption chamber 21 is larger than that of the other adsorption chambers 18 and 20, the remaining amount of the evaporated fuel in the third adsorption chamber 21 is the other adsorption chambers 18 and 20. Less than. Further, since the adsorbent 29 accommodated in the third adsorption chamber 21 has a higher desorption capability than the adsorbent 28 accommodated in the other adsorption chambers 18 and 20, the remaining amount of evaporated fuel is further increased. Less. Since there is no step between the second adsorption chamber 20 and the third adsorption chamber 21, there is no significant pressure loss.

  In this way, by capturing the evaporated fuel from the fuel tank in the canister 1, the evaporated fuel is prevented from being released into the atmosphere, and after purging the evaporated fuel adsorbed on the adsorbents 28 and 29, again A series of cycles in which the evaporated fuel from the fuel tank is adsorbed by the canister 1 is repeated. However, in actuality, the evaporated fuel is not completely desorbed from the adsorbent at the time of purging, and the residual evaporated fuel causes a blow-through phenomenon in which the evaporated fuel is diffused into the atmosphere while the vehicle is stopped. However, the canister 1 of the first embodiment is designed so that the predetermined range reaching the atmospheric port 14 is gradually reduced in diameter as described above, and the L / D ratio in the vicinity of the atmospheric port 14 is designed to be the largest. The remaining amount of evaporated fuel in the vicinity of the port 14 is small. Thereby, the blow-by amount when the vehicle is stopped is also reduced.

(Example 2)
FIG. 4 shows a canister 2 according to the second embodiment of the present invention. In the canister 1 according to the first embodiment, a part of the atmospheric port 14 side adsorption chamber 19, that is, the sectional area of at least a predetermined range on the atmospheric port 14 side along the flowing direction of the evaporated fuel in the atmospheric port side adsorption chamber 19 is gradually reduced. However, the present invention is not limited to this, and the entire cross-sectional area of the atmospheric port side adsorption chamber 19 may be gradually reduced. That is, as in the canister 2 of the second embodiment shown in FIG. 4, in addition to the most downstream third adsorption chamber 21 facing the atmospheric port 14, the second adsorption chamber upstream of this in the atmospheric port side adsorption chamber 19. 20 may also be inclined to gradually reduce the cross-sectional area. The canister 2 of the second embodiment also belongs to the first form of the present invention. And like the canister 1 of Example 1, the 2nd adsorption | suction chamber 20 and the 3rd adsorption | suction chamber 21 in the atmospheric | air-port side adsorption | suction chamber 19 are in the cross-sectional area change part where the cross-sectional area becomes small gradually. It is partitioned without a step, and the L / D ratio in the vicinity of the atmospheric port 14 is the largest. The other parts are the same as those in the first embodiment, and the same members are denoted by the same reference numerals and the description thereof is omitted.

(Example 3)
FIG. 5 shows a canister 3 according to the third embodiment of the present invention. The characteristic point of the canister 3 of the third embodiment is that the cross-sectional area is gradually reduced while the intermediate portion of the atmospheric port side adsorption chamber 19 is inclined toward the atmospheric port 14 side. This is the second aspect of the present invention. Belongs. That is, the atmospheric port side adsorption chamber 19 includes a small-diameter vertical wall portion 31 that reaches the atmospheric port 14, an inclined wall portion 32 that gradually decreases in cross-sectional area while inclining toward the atmospheric port 14, and an upstream large diameter. The vertical wall portion 33 is integrally and continuously provided. The inclined wall portion 32 corresponds to the cross-sectional area changing portion of the present invention. The cross-sectional area of the vertical wall portion 31 on the atmosphere port 14 side is smaller than the cross-sectional area of the vertical wall portion 33 upstream of the inclined wall portion 32. Since the screen 23 is disposed at the inclined base end position of the inclined wall portion 32, the second adsorption chamber 20 and the third adsorption chamber 21 are partitioned by the inclined wall portion 32. That is, the canister 3 of the third embodiment also has a gradual cross-sectional area between the second adsorption chamber 20 and the third adsorption chamber 21 in the atmospheric port side adsorption chamber 19 as in the first and second embodiments. In the cross-sectional area changing portion that is smaller, the area is partitioned without a step, and the L / D ratio in the vicinity of the atmospheric port 14 is the largest. As a result, the remaining amount of evaporated fuel in the vicinity of the air port 14 after the purge is reduced, and the subsequent blow-through amount can be reduced. Others are the same as those in the first and second embodiments, and the same members are denoted by the same reference numerals and the description thereof is omitted.

Example 4
FIG. 6 shows a canister 4 according to a fourth embodiment of the present invention. The canister 4 of the fourth embodiment is a modification of the canister 3 of the third embodiment and belongs to the second mode of the present invention. The difference from the canister 3 of the third embodiment is that, in addition to the screen 23 arranged at the inclined base end of the inclined wall portion 32 which is the cross-sectional area changing portion, the screen 30 is also arranged at the inclined tip end of the inclined wall portion 32. The air port side adsorption chamber 19 is further finely divided. Actually, the third adsorption chamber in the third embodiment is further divided into two adsorption chambers. Specifically, the atmospheric port side adsorption chamber 19 includes, from the upstream side, a second adsorption chamber 20 in the large-diameter vertical wall portion 33, a third adsorption chamber 34 in the inclined wall portion 32, It consists of a fourth suction chamber 35 located at the small-diameter vertical wall 31 portion. In the fourth embodiment, the third and fourth adsorption chambers 34 and 35 are filled with the adsorbent 29 having a large desorption capability. The other parts are the same as those in the third embodiment, and the same members are denoted by the same reference numerals and the description thereof is omitted.

(Example 5)
FIG. 7 shows a canister 5 according to a fifth embodiment of the present invention. The canister 5 of the fifth embodiment belongs to the third mode of the present invention, and is characterized in that an additional adsorption chamber 40 is provided in a communication form outside the canister 5 as shown in FIG. The outer wall of the atmospheric port side adsorption chamber 19 in the canister 5 is not inclined. That is, the cross-sectional area of the second adsorption chamber 20 and the cross-sectional area of the third adsorption chamber 21 in the canister 5 are the same. The additional adsorption chamber 40 is integrally formed in an inner and outer through shape at a portion where the atmospheric port 14 of the canister case 10 is provided in the first to fourth embodiments, and the atmospheric port 14 is integrally formed on the upper surface thereof. Inside the additional adsorption chamber 40, an adsorbent 29 is accommodated between the filters 41 and 41 arranged vertically. The filter 41 disposed in the additional adsorption chamber 40 is the same as the filter 24 disposed in the canister 5.

  By providing the additional adsorption chamber 40 in the conventional canister, an increase in ventilation resistance is inevitable. Therefore, in order to avoid a significant increase in the ventilation resistance, the communication hole 42 between the canister 5 and the additional adsorption chamber 40 is made larger than the opening diameter of the atmospheric port 14, and the adsorbent 29 is closely packed in the canister 5. Compared to the adsorbents 28 and 29 that are accommodated, they are accommodated roughly. That is, the filling density of the adsorbent 29 accommodated in the additional adsorption chamber 40 is smaller than the filling density of the adsorbents 28 and 29 accommodated in the canister 5. As a result, the ventilation resistance is reduced to some extent, so that a significant increase in ventilation resistance due to the addition of the additional adsorption chamber 40 can be avoided. If the additional adsorption chamber 40 is provided, even if the evaporated fuel remains to some extent in the third adsorption chamber 21 in the most downstream in the canister 5, the diffusion of the remaining evaporated fuel to the atmosphere port 14 side is not performed. While being inhibited to some extent by the filter 41 of the chamber 40 and being reliably adsorbed and supplemented by the adsorbent 40 of the additional adsorption chamber 40, the blow-by amount can be reduced.

(Other variations)
The first and second embodiments of the present invention can be combined with the third embodiment. That is, each of the canisters 1 to 4 of the first to fourth embodiments is provided with the additional adsorption chamber 40 like the canister 5 of the fifth embodiment, or the canister 5 of the fifth embodiment is replaced with each of the canisters 1 to 4 of the first to fourth embodiments. The amount of blow-through can be further reduced by inclining at least a part of the atmospheric port side adsorption chamber 19 as shown in 4 and gradually reducing the cross-sectional area.

  In the first to fifth embodiments, the adsorbent 29 having a high desorption capability is accommodated in the third adsorption chambers 21, 34, the third adsorption chamber 35, and the additional adsorption chamber 40 on the downstream side in the fuel vapor flow direction. However, this is not always necessary, and the adsorbing material 28 stored in the first adsorption chamber 18 may be accommodated in the adsorption chambers 21, 34, 35, and 40. Even in this case, the blow-through amount can be sufficiently reduced by providing the L / D ratio in the vicinity of the atmospheric port 14 and / or providing the additional adsorption chamber 40.

  When the sectional area of the atmospheric port side adsorption chamber 19 is gradually reduced toward the atmospheric port 14 as in the first embodiment, the inclined wall is not limited to the upper half on the downstream side. For example, it can be inclined about 10% or about 80% with respect to the length dimension of the atmospheric port side adsorption chamber 40 (length dimension along the flowing direction of the evaporated fuel). That is, the inclined wall (cross-sectional area changing portion) can be appropriately designed in the range of 10 to 100% of the length dimension of the atmospheric port side adsorption chamber 40. Similarly, as in the third and fourth embodiments, when the intermediate portion of the atmospheric port side adsorption chamber 19 is inclined to gradually reduce the cross-sectional area, the inclined wall (cross-sectional area changing portion) is It can be designed as appropriate within a range of about 10 to 90% of the length of the adsorption chamber 40.

  In each of the above-described embodiments, the screens 23 and 30 that partition the atmospheric port side adsorption chamber 19 are disposed in the cross-sectional area changing portion, but this is not always necessary, and the vertical wall portion may be divided into a plurality of adsorption chambers. .

It is a graph which shows the amount of blow-throughs in a DBL test. It is a graph which shows the relationship etc. of butane residual amount and blow-through amount. 2 is a cross-sectional view of a canister according to Embodiment 1. FIG. 6 is a cross-sectional view of a canister according to Embodiment 2. FIG. 6 is a cross-sectional view of a canister according to Embodiment 3. FIG. 6 is a cross-sectional view of a canister of Example 4. FIG. 6 is a cross-sectional view of a canister according to Embodiment 5. FIG.

Explanation of symbols

1, 2, 3, 4, 5 Canister 10 Canister case 13 Tank port 14 Air port 15 Purge port 16 Partition wall 18 First adsorption chamber (tank port side adsorption chamber)
19 Atmospheric port side adsorption chamber 20 Second adsorption chamber 21/34 Third adsorption chamber 23/30 Screen 24/41 Filter 28/29 Adsorbent 32 Inclined wall section (cross-sectional area changing section)
40 Additional adsorption chamber D Effective sectional diameter L of the adsorption chamber Length of the adsorption chamber along the flow direction of the evaporated fuel

Claims (7)

An adsorbent that adsorbs and desorbs evaporated fuel is housed therein, and includes an tank port communicating with the fuel tank and an atmosphere port communicating with the atmosphere, and an upstream tank port side adsorption chamber partitioned by a partition wall; In the canister, the downstream atmospheric port side adsorption chamber is aligned in series with the flow direction of the evaporated fuel.
A canister characterized in that at least a predetermined range on the atmosphere port side along the flow direction of the fuel vapor in the atmosphere port side adsorption chamber is gradually reduced in cross section while inclining toward the atmosphere port. An adsorbent that adsorbs and desorbs evaporated fuel is housed therein, and includes an tank port communicating with the fuel tank and an atmosphere port communicating with the atmosphere, and an upstream tank port side adsorption chamber partitioned by a partition wall; In the canister, the downstream atmospheric port side adsorption chamber is aligned in series with the flow direction of the evaporated fuel.
While the intermediate portion of the atmospheric port side adsorption chamber is inclined toward the atmospheric port side, the sectional area gradually decreases, and the sectional area of the atmospheric port side adsorption chamber on the atmospheric port side is a section upstream of the intermediate portion. A canister characterized by being smaller than the area.   The atmosphere port side adsorption chamber is further divided into a plurality of adsorption chambers in a cross-sectional area changing portion where the cross-sectional area of the atmosphere port side adsorption chamber is gradually reduced. The canister according to claim 2.   Assuming that the length of the adsorption chamber along the flow direction of the evaporated fuel is L and the effective sectional diameter of the adsorption chamber is D, the L / D ratio of the most downstream adsorption chamber facing the atmospheric port is L / D of the other adsorption chambers. The canister according to any one of claims 1 to 3, wherein the canister is larger than the ratio.   5. The adsorbent having higher desorption capability than the adsorbents accommodated in the other adsorbing chambers is accommodated in the most downstream adsorbing chamber facing the air port. Canister according to crab.   6. The additional adsorption chamber is provided in communication with the outside of the most downstream adsorption chamber in the canister, and the atmospheric port is provided in the additional adsorption chamber. The canister described. The canister according to claim 6, wherein the additional adsorption chamber has better air permeability than other adsorption chambers.

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