Evaporative emissions canister with layered carbon

Abstract

An evaporative emission tank (10) is provided. The tank includes a housing (12) defining an interior volume therein, and an inlet (14) and an outlet (16) in fluid communication with the interior volume. The interior volume includes a first layer of absorbent material (26) and a second layer of absorbent material (28). The flow restriction of the first absorbent material is lower than the flow restriction of the second absorbent material. A fluid flow path is defined from the inlet through the interior volume of the housing to the outlet. The fluid flow path includes a transition region (24) that varies cross-sectional area in a direction (F) from the inlet to the outlet. The first layer of absorbent material (26) is arranged at or directly adjacent to the transition zone (24), and the first layer of absorbent material (26) is arranged adjacent to and immediately upstream of the second layer of absorbent material (28) in the direction (F).

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. patent application No. 17 / 940,389, filed on September 8, 2022, the disclosure of which is incorporated by reference in its entirety. Technical Field

[0002] The present disclosure generally relates to evaporative emissions canisters for absorbing fuel vapors in fuel-powered motor vehicles. Background Art

[0003] The evaporative loss of fuel vapor generated in the fuel tank of the fuel system of a motor vehicle powered by an internal combustion engine is a potential contributor to atmospheric air pollution by hydrocarbons. A canister system that employs activated carbon to absorb the fuel vapor discharged from the fuel system is used to limit such evaporative emissions from the fuel tank of a gasoline-fueled motor vehicle. A typical evaporative emission canister includes a housing, inside which a gas passage filled with activated carbon as a fuel vapor absorbent is formed. The charging and purging port for the fuel vapor is communicated with one end of the gas passage, while the atmospheric port (vent port) for the fuel vapor is communicated with the other end of the gas passage, thereby allowing the canister to be charged. During vehicle stop (e.g., when parked), the fuel vapor generated by the fuel in the fuel tank is introduced into the canister through the charging port and absorbed by the absorbent. During operation of the engine, atmospheric air is introduced through the atmospheric vent port to purge the fuel vapor in the canister by desorbing the fuel vapor absorbed in the absorbent. The air flow carries the purged fuel vapor to the intake system of the engine through the purge port so that the fuel vapor can be burned in the engine, thereby completing the purging of the canister. Through desorption of fuel vapors during the purge, the carbon absorbent is regenerated and the fuel vapor absorption performance of the canister is restored, thereby allowing the absorbent to repeatedly absorb fuel vapors during periods of engine non-use.

[0004] Conventional evaporative emissions canisters typically use one grade of carbon absorbent throughout the entire fill area of ​​the canister housing, or at least throughout one full chamber of the canister. However, conventional evaporative emissions canisters may suffer from poor airflow through a portion of the canister housing, which results in "dead zones" within the canister where the absorbent volume is not effectively or adequately aerated and / or purged during operation of the vehicle. Some of these dead zones are particularly prevalent in absorbent bed areas where there is significant variation in the housing cross-sectional area. Therefore, there is a need for improved flow distribution within the housing. Summary of the invention

[0005] An improved evaporative emissions canister is provided. The evaporative emissions canister includes a housing defining an internal volume therein. The housing includes an inlet and an outlet in fluid communication with the internal volume. The internal volume includes a first layer of absorbent material and a second layer of absorbent material. The flow restriction of the first absorbent material is lower than the flow restriction of the second absorbent material. A fluid flow path is defined from the inlet through the internal volume of the housing to the outlet. The fluid flow path has a cross-sectional area that changes in a direction from the inlet to the outlet, and the fluid flow path includes a transition zone that changes in cross-sectional area in a direction from the inlet to the outlet. The first layer of absorbent material is disposed at or directly adjacent to the transition zone, and the first layer of absorbent material is disposed adjacent to and immediately upstream of the second layer of absorbent material in the direction. The first layer of absorbent material diffuses the fluid flow along the fluid flow path into the second layer of absorbent material.

[0006] In a specific embodiment, the average particle size of the first absorbent material is at least 1.2 times the average particle size of the second absorbent material.

[0007] In a particular embodiment, the first getter material is particulate carbon and the second getter material is granular carbon.

[0008] In specific embodiments, the interior volume includes a transition region where the cross-sectional area changes.

[0009] In certain embodiments, the internal volume includes a first region having a first cross-sectional area. The first region is at the inlet end of the housing. In these embodiments, the internal volume also includes a second region having a second cross-sectional area. The second region is located at the outlet end of the housing, and the second cross-sectional area is greater than the first cross-sectional area. A transition region where the cross-sectional area changes is disposed between the first region and the second region. The transition region includes a first absorbent material layer, and the second region includes a second absorbent material layer.

[0010] In certain embodiments, the first region includes a layer of a third absorbent material. The third absorbent material has a flow restriction that is higher than the flow restriction of the first absorbent material. In other embodiments, the third absorbent material is the same as the second absorbent material.

[0011] In certain embodiments, the first region includes a volume of void space.

[0012] In a particular embodiment, the height of the first layer of absorbent material in the direction from the inlet to the outlet is smaller than the height of the second layer of absorbent material in said direction.

[0013] In a specific embodiment, the change in cross-sectional area in the transition zone is step-shaped in the direction from the inlet to the outlet.

[0014] A fuel vapor storage canister is also provided for absorbing fuel evaporated in a fuel tank of a motor vehicle. The fuel vapor storage canister includes a shell forming a body, which defines at least one chamber therein. The canister also includes a ventilation port in the body. The ventilation port leads to the atmosphere. The canister also includes a purge port in the body. The purge port is on the end of the body opposite to the ventilation port, and the purge port is in fluid communication with the vehicle's intake system. At least one chamber has a cross-sectional area that changes in the direction from the ventilation port to the purge port. The at least one chamber includes a first bed of absorbent material and a second bed of absorbent material. The flow restriction of the first absorbent material is lower than the flow restriction of the second absorbent material. The first bed of absorbent material is arranged at or directly adjacent to a transition zone, and the transition zone changes the cross-sectional area of ​​at least one chamber in the direction from the ventilation port to the purge port, and the first bed of absorbent material is arranged in the direction adjacent to and immediately upstream of the second bed of absorbent material.

[0015] In a specific embodiment, the average particle size of the first absorbent material is at least 1.2 times the average particle size of the second absorbent material.

[0016] In a particular embodiment, the first getter material is particulate carbon and the second getter material is granular carbon.

[0017] In a specific embodiment, the change in cross-sectional area in the transition zone is stepped in a direction from the vent port to the purge port.

[0018] A method of manufacturing an evaporative emissions canister is also provided. The method includes providing a housing having an interior volume, an inlet and an outlet in fluid communication with the interior volume, and a fluid flow path defined from the inlet through the interior volume of the housing to the outlet. The fluid flow path has a cross-sectional area that changes in a direction from the inlet to the outlet, and the fluid flow path includes a transition zone that changes in cross-sectional area in a direction from the inlet to the outlet. The method also includes the step of disposing a first layer of absorbent material at or directly adjacent to the transition zone. The method also includes the step of disposing a second layer of absorbent material adjacent to the first layer of absorbent material in the direction and immediately downstream of the first layer of absorbent material. The first absorbent material has a flow restriction that is lower than the flow restriction of the second absorbent material, and the first layer of absorbent material diffuses the fluid flow along the fluid flow path into the second layer of absorbent material.

[0019] In a specific embodiment, the average particle size of the first absorbent material is at least 1.2 times the average particle size of the second absorbent material.

[0020] In a particular embodiment of the method, the first getter material is particulate carbon and the second getter material is granular carbon.

[0021] In a particular embodiment of the method, the change in cross-sectional area in the transition zone is step-shaped in the direction from the inlet to the outlet. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The various advantages and aspects of the present invention can be understood by reading the following detailed description in conjunction with the accompanying drawings, in which:

[0023] Figure 1 is a perspective schematic diagram of an evaporative emissions canister according to some embodiments of the present disclosure;

[0024] Figure 2 is through Figure 1 A side schematic diagram of fluid flow in an evaporative emissions canister; and

[0025] Figure 3 is a cross-sectional view of an evaporative emissions canister according to certain embodiments of the present disclosure. DETAILED DESCRIPTION

[0026] An evaporative emissions canister is provided. Figure 1-3 , wherein like reference numerals indicate corresponding parts throughout the several views, an evaporative emissions canister is shown and generally designated as a fuel vapor storage canister 10 for a fuel tank of a vehicle fuel system that pumps liquid fuel (such as gasoline fuel as a non-limiting example) from a fuel tank (not shown) to an internal combustion engine (not shown) that powers a motor vehicle. The fuel vapor storage canister 10 captures fuel vapor that occurs in the fuel tank during periods when the internal combustion engine is not in use due to, for example, daily changes in ambient temperature. The fuel vapor storage canister 10 exhibits improved internal fluid flow, resulting in a reduction in dead space and more efficient purging of the canister 10.

[0027] Figure 1A fuel vapor canister 10 used in a vehicle fuel system is generally depicted. The fuel vapor canister 10 includes a housing 12 that forms the body of the canister 10. The housing 12 defines an internal volume within the body. The internal volume may be a single chamber within the canister, or may be partitioned into a plurality of chambers. The housing 12 has at least one inlet and outlet that are fluidly connected to the internal volume of the housing 12. In particular, the housing 12 has an air charging port 14, a purge port 16, and a vent port 18. The air charging port 14 and the purge port 16 are disposed at one end of the internal volume of the housing 12, while the vent port 18 is disposed at the opposite end, so that there may be fluid flow between the air charging port 14 and the vent port 18 or between the vent port 18 and the purge port 16. The air charging port 14 is connected to the vehicle fuel tank via a conduit or the like and is fluidly connected to the vehicle fuel tank, while the vent port 18 is open to the atmosphere for venting the canister 10 and for allowing purge air to enter. The purge port 16 is connected to the intake system of the engine via a conduit or the like and is fluidly connected thereto. As described in more detail below, during the period when the internal combustion engine is not used when the engine is turned off, the fuel vapor generated in the fuel tank travels through the charging port 14 and enters the internal volume of the housing 12. The fuel vapor is trapped in the canister housing 12, and the air leaves the housing 12 through the ventilation port 18. During the use of the internal combustion engine when the engine is running, air is sucked into the canister 10 through the ventilation port 18, and the trapped fuel vapor is discharged from the housing 12 through the purge port 16 and enters the intake system of the internal combustion engine. Therefore, it is obvious that the charging port 14 is the inlet and the purge port 16 is the outlet, and the ventilation port 18 can be an outlet or an inlet, depending on the operation of the canister 10 (charging and purging) and the associated flow direction. Therefore, the fluid flow path extends from the charging port 14 through the internal volume of the housing 12 to the ventilation port 18 in one flow direction in one operating mode of the canister 10, and extends from the ventilation port 18 through the internal volume of the housing 12 to the purge port 16 in another operating mode of the canister 10.

[0028] The internal volume of the housing 12 has a cross-sectional area that varies in a direction from the charging port 14 to the ventilation port 18, which direction can generally be designated as the flow direction F of the fluid (air and fuel vapor) traveling from the charging port 14 to the ventilation port 18 during the charging of the tank 10. The direction F can be referred to as the absorption direction. The housing 12 is not limited to any particular geometry, and can be box-shaped and have, for example, a substantially rectangular cross-section in a direction substantially perpendicular to the flow direction. However, the housing 12 can alternatively or additionally have or include separate chambers that have any of a conical, truncated conical, and / or cylindrical shape, and thus have a substantially circular cross-section. The cross-sectional area of ​​the internal volume of the housing 12 can increase from the charging port 14 to the ventilation port 18, so that the internal volume includes a first zone 20 having a first smaller cross-sectional area adjacent to the charging port 14, a second zone 22 having a second larger cross-sectional area adjacent to the ventilation port 18 that is greater than the cross-sectional area of ​​the first zone 20, and a transition zone 24 disposed between the first zone 20 and the second zone 22. The transition zone 24 is a zone in which the cross-sectional area changes from a first cross-sectional area to a second cross-sectional area. The cross-sectional area may change rapidly in the transition zone 24, so that the area increases significantly by a large factor relative to the direction of the (inflation) flow. Figure 1 In some of the embodiments shown, the change in cross-sectional area in the transition zone 24 can be almost instantaneous in the direction of flow from the charging port 14 to the venting port 18, so that there is a step change in area from the first zone 20 to the second zone 22, and the transition zone 24 can include the volume of the shell 12 directly adjacent to the change in cross-sectional area in the downstream direction. In other words, the internal volume of the shell 12 can be stepped from the first zone 20 to the second zone 22, and in this case, the transition zone 24 is a portion of the internal volume directly adjacent to the step between the first zone 20 and the second zone 22 in the downstream direction, and the transition zone has a cross-sectional area that is substantially equal to the cross-sectional area of ​​the second zone 22.

[0029] During purging of the canister 10, fluid (air and fuel vapor) generally flows from the vent port 18 to the purge port 16 in a direction opposite to the direction F. The flow direction opposite to the direction F during purging may be referred to as an absorption direction, where the air absorbs the fuel vapor trapped in the canister 10. In the absorption direction, the cross-sectional area of ​​the interior volume of the housing 12 may decrease from the vent port 18 to the purge port 16, particularly at the transition zone 24 between the second zone 22 and the first zone 20. The cross-sectional area decreases significantly from the second zone 22 to the first zone 20.

[0030] The transition zone 24 of the internal volume includes an absorbent bed including a first absorbent material layer 26, and the second zone 22 of the internal volume includes an absorbent bed including a second absorbent material layer 28. The first absorbent material layer 26 is disposed adjacent to and immediately upstream of the second absorbent material layer 28 in the direction of flow from the vent port 18 to the purge port 16. The first absorbent material 26 has a flow restriction (i.e., a property of restricting / inhibiting fluid flow) that is lower than the flow restriction of the second absorbent material 28. In particular, the first absorbent material 26 is an absorbent having an average particle size greater than that of the second absorbent material 28. In other words, the first absorbent material 26 has a larger average particle size relative to the second absorbent material 28, and the second absorbent material 28 has a smaller average particle size relative to the first absorbent material 26. For example, the average particle size of the first absorbent material 26 having a lower flow restriction property may be at least 1.2 times the average particle size of the second absorbent material 28 having a higher flow restriction property. Furthermore, by way of example only, the absorbent materials 26, 28 may be activated carbon, and the first absorbent material 26 may be pellet carbon, while the second absorbent material 28 may be granular carbon. Alternatively, both the first and second absorbent materials 26, 28 may be granular carbon, wherein the average particle size of the granular carbon comprising the first absorbent material 26 is greater than the average particle size of the granular carbon comprising the second absorbent material 26. Similarly, both the first and second absorbent materials 26, 28 may be granular carbon, wherein the average particle size of the granular carbon comprising the first absorbent material 26 is greater than the average particle size of the particles comprising the second absorbent material 26. However, it should be understood that the absorbent can be other types or forms of absorbent, such as spherical, honeycomb, cylindrical, extruded, wound, folded, pleated, corrugated, bonded or poured form structured media, sheets, foams, etc., as long as the low flow restriction absorbent layer (e.g., absorbent with a larger average particle size) is immediately before the high flow restriction absorbent layer (e.g., absorbent with a smaller average particle size) or immediately after the transition zone where the cross-sectional area changes / has changed. The absorption bed volume of the second absorbent material layer 28 is greater than the absorption bed volume of the first absorbent material layer 26. For example, the volume of the second absorbent material 28 can be at least three times the volume of the first absorbent material 26. In addition, the height of the first absorbent material layer 26 in the flow direction is less than the height of the second absorbent material layer 28, and the height of the first absorbent material 26 can be, for example, in the range of 25 mm to 35 mm, more preferably in the range of 27.5 mm to 32.5 mm, even more preferably in the range of 29 mm to 31 mm, and even more preferably about 30 mm.

[0031] Optionally, the first zone 20 of the housing 12 may include an absorbent bed including a layer of a third absorbent material 30 having a flow restriction that is higher than the flow restriction of the first absorbent material 26. Preferably, the third absorbent material 30 is the same as the second absorbent material 28, but the third absorbent material 30 is not limited to this arrangement. The composition of the third absorbent material 30 is not particularly limited. Alternatively, the first zone 20 includes a volume of void space, in which case the flow restriction in the first zone 20 is less than the flow restriction of the first absorbent material 26.

[0032] Go to Figure 3In certain embodiments, a fuel vapor storage canister 110 includes a housing 112 having a charge port 114, a purge port 116, and a vent port 118, wherein the vent port 118 is juxtaposed with and faces the same direction as the charge port 114 and the purge port 116, but at an opposite end of a flow path through the interior volume of the canister 110 from the charge port 114 and the purge port 116 to the vent port 118. In this arrangement, a first zone 120 is adjacent to the charge port 114 and is separated from a third zone 123 adjacent to the purge port 116 by a partition 121. A transition zone 124 is disposed directly adjacent to the first zone 120 (and the third zone 123) and immediately downstream (in the fluid flow direction F' from the charge port 114 to the vent port 118) of the change in cross-sectional area of ​​the interior volume of the housing 112 caused by the partition 121. The transition zone 124 is also directly adjacent to and upstream of the second zone 122 in the flow direction F'. The transition zone 124 is filled with a first absorbent material 126, and the second zone 122 is filled with a second absorbent material 128. The first absorbent material 126 and the second absorbent material 128 have the same properties as the first and second absorbent materials 26, 28 described above, respectively. The first zone 120 may be filled with a third absorbent material 130. The properties of the third absorbent material 130 are not significantly or particularly limited, and the third absorbent material 130 may be the same as the first absorbent material 126 or the second absorbent material 128. In an alternative embodiment not shown, the first zone 120 may not be filled with an absorbent, thereby being an empty void space. In yet another alternative, a flow tube or other conduit may extend from the inflation port 114 to the first absorbent material 126 in the transition zone 124, such that the change in cross-sectional area along the fluid flow path between the inflation port 114 and the interior volume of the housing 112 is from the terminal end of the flow tube to the transition zone 124. Similarly, the third zone 123 adjacent to the purge port 116 may be filled with a fourth absorbent material 132. The properties of the fourth absorbent material 132 are also not significantly or particularly limited, and the fourth absorbent material 132 can be the same as the first absorbent material 126, the second absorbent material 128, or the third absorbent material. Alternatively, the fourth absorbent material 132 can be different from the first absorbent material 126, the second absorbent material 128, and the third absorbent material. In an alternative embodiment not shown, the third zone 123 may not be filled with an absorbent, thereby being an empty void space. In yet another alternative, a flow tube or other conduit can extend from the purge port 116 to the first absorbent material 126 in the transition zone 124. The fourth zone 134 is adjacent to the vent port 118. The fourth zone 134 is filled with a fifth absorbent material 136. The properties of the fifth absorbent material 136 are not significantly or particularly limited, and can be the same or different from the third absorbent material 130 or any other absorbent material 126, 128, 132.An empty void space 138 in the interior volume of the tank 112 extends between the second zone 122 and the fourth zone 134 along a fluid flow path through the interior volume of the tank 112 .

[0033] Reference again Figure 1 During the non-operating period of the internal combustion engine, fuel vapor generated from the liquid fuel stored in the fuel tank enters the fuel vapor storage canister 10 through the charging port 14. When the fuel vapor enters the absorbent area 20, 22, 24 in the housing 12, the fuel vapor is absorbed by the absorbent material layers 26, 28 and 30 (if present). Essentially only clean air leaves the canister 10 through the ventilation port 18, while the fuel vapor remains trapped in the canister 10. When the internal combustion engine is started and operated, outside air is sucked into the canister 10 through the ventilation port 18. When the air passes through the absorbent area 20, 22, 24, the fuel vapor is desorbed into the air and carried away from the absorbent material 26, 28 and 30 (if present) and enters the air flow. Therefore, the flow of the charging air is generally in the direction F from the charging port 14 to the ventilation port 18, wherein the charging port 14 is on the upstream side and the ventilation port 18 is on the downstream side. Importantly, the absorbent material layers 26, 28, and 30 (if present) provide uniform flow through the zones 20, 22, 24 within the housing 12. In particular, as the air flows through the transition zone 24, the more flow-restricting absorbent material layer 28 in the downstream second zone 22 forces a component of the air flow in the less flow-restricting transition zone 24 to travel laterally (approximately or nearly perpendicular to the direction from the vent port 18 to the purge port 16), as shown in FIG. Figure 2 Schematically shown in FIG. In other words, the first absorbent material 26 layer having a lower flow restriction than the downstream second absorbent material 28 layer causes the fluid flow to spread along the fluid flow path into the second absorbent material 28 layer. This lateral flow component allows the charging air to reach the edge of the transition zone 24, thereby improving the flow distribution in the transition zone 24, eliminating any "dead zones" in the corners of the transition zone 24 or along the edges of the transition zone 24, and ensuring that the fuel vapor is absorbed by the entire layer / bed of the absorbent material 26 in the transition zone 24. Therefore, during the charging period completed during the non-operation of the vehicle engine, the absorbent materials 26, 28 and 30 (if present) in the tank 10 are more completely filled with fuel vapor so that they can be purged into the intake of the engine later when the engine is next turned on. Similar but less significant flow distribution effects can be observed when the air flow is reversed during the operation of the vehicle (purging) and the air absorbs / reabsorbs the fuel vapor trapped in the absorbent materials 26, 28, 30. In this case, the air flow passes from the second zone 22 through the transition zone 24 and enters the first zone 20.

[0034] The resulting improvement in the performance and efficiency of the tank 10 allows for a reduction in the total absorbent material volume in the tank 10 to achieve the same operating capacity due to the improved flow distribution and elimination of dead zones provided by the less flow-restrictive absorbent material layer 26 present in the transition zone 24 of changed cross-sectional area, which is directly upstream of the more flow-restrictive absorbent material layer 28 in the direction of the purge flow. The reduction in the required absorbent material volume, in turn, provides cost benefits by reducing the material cost of the tank 10, and also reduces the overall weight of the tank 10. In addition, the use of less expensive, more flow-restrictive granular carbon as the absorbent material 28 in the higher cross-sectional area of ​​the second zone 22 reduces the component cost of the tank 10.

[0035] Turn again Figure 3 During the non-operating period of the internal combustion engine, fuel vapor generated from the liquid fuel stored in the fuel tank enters the fuel vapor storage canister 110 through the charging port 114. When the fuel vapor enters the first absorbent material 126 in the transition zone 124 from the charging port 114 and the first zone 120, the first absorbent material layer 126 with a larger particle size and a lower flow restriction provides a lateral uniform diffusion of the fluid flow through the first zone 120 and into the second absorbent material 128 in the second zone 122. Therefore, the flow of fuel vapor and air is generally in the direction F from the charging port 114 to the ventilation port 118, wherein the charging port 114 is on the upstream side and the ventilation port 118 is on the downstream side. The layer of the first absorbent material 126 having a lower flow restriction than the downstream layer of the second absorbent material 128 spreads the fluid flow into the layer of the second absorbent material 128 along the fluid flow path, thereby allowing the fuel vapor to be more evenly spread throughout the second zone 122, so that the second absorbent material 128 can be more completely charged with fuel vapor.

[0036] It should be understood that the appended claims are not limited to the expressions and specific compounds, compositions, or methods described in the detailed description, which may vary between specific embodiments falling within the scope of the appended claims. With respect to any Markush group relied upon herein to describe specific features or aspects of various embodiments, different, special, and / or unexpected results may be obtained from each member of the corresponding Markush group independent of all other Markush members. Each member of the Markush group may be relied upon individually and / or in combination and provides adequate support for specific embodiments within the scope of the appended claims.

[0037] In addition, any ranges and sub-ranges relied upon to describe various embodiments of the present invention are independently and collectively within the scope of the appended claims, and are understood to describe and contemplate all ranges including all and / or fractional values ​​therein, even if these values ​​are not explicitly written herein. It is readily recognized by those skilled in the art that the listed ranges and sub-ranges fully describe and enable various embodiments of the present invention, and these ranges and sub-ranges can be further described as the associated half, third, quarter, fifth, etc. As just one example, the range "from 0.1 to 0.9" can be further described as the lower third (i.e., from 0.1 to 0.3), the middle third (i.e., from 0.4 to 0.6), and the upper third (i.e., from 0.7 to 0.9), which are individually and collectively within the scope of the appended claims, and can be individually and / or collectively relied upon and provide sufficient support for specific embodiments within the scope of the appended claims. In addition, with respect to defining or modifying the language of ranges such as "at least", "greater than", "less than", "not more than", etc., it should be understood that such language includes sub-ranges and / or upper or lower limits. As another example, a range of "at least 10" inherently includes a subrange of at least 10 to 35, a subrange of at least 10 to 25, a subrange of 25 to 35, etc., and each subrange can be relied upon individually and / or collectively and provide sufficient support for specific embodiments within the scope of the appended claims. Finally, individual numbers within the disclosed ranges can be relied upon and provide sufficient support for specific embodiments within the scope of the appended claims. For example, a range of "from 1 to 9" includes various individual integers, such as 3, and individual numbers including decimal points (or fractions), such as 4.1, which can be relied upon and provide sufficient support for specific embodiments within the scope of the appended claims.

Claims

1. An evaporative emissions canister (10), comprising: a housing defining an interior volume therein; The housing includes an inlet (14) and an outlet (16) in fluid communication with the interior volume; The interior volume includes a first layer of absorbent material (26) and a second layer of absorbent material (28), the first absorbent material having a flow restriction that is lower than a flow restriction of the second absorbent material; a fluid flow path defined from the inlet through the interior volume of the housing to the outlet; The fluid flow path has a cross-sectional area that varies in a direction (F) from the inlet to the outlet, the fluid flow path including a transition zone (24) that varies in cross-sectional area in a direction from the inlet to the outlet; wherein the first absorbent material (26) layer is disposed at or directly adjacent to the transition zone (24), the first absorbent material layer is disposed adjacent to and immediately upstream of the second absorbent material (26) layer in the direction (F), and wherein the first absorbent material layer diffuses a fluid flow into the second absorbent material layer along the fluid flow path.

2. The evaporative emissions canister of claim 1, wherein: The average particle size of the first absorbent material (24) is at least 1.2 times the average particle size of the second absorbent material (26).

3. The evaporative emission canister of claim 1 or 2, wherein: The first getter material (24) is particulate carbon and the second getter material (26) is granular carbon.

4. The evaporative emission canister according to any one of claims 1 to 3, wherein: The interior volume includes the transition region (24) where the cross-sectional area changes.

5. The evaporative emissions canister of claim 4, wherein: The internal volume includes a first region (20) having a first cross-sectional area, the first region being located at the inlet end of the housing; the internal volume also includes a second region (22) having a second cross-sectional area, the second region being located at the outlet end of the housing, and the second cross-sectional area being greater than the first cross-sectional area; and wherein the transition zone (24) of changed cross-sectional area is disposed between the first zone and the second zone; the transition zone comprises a layer of the first absorbent material (26), and the second zone comprises a layer of the second absorbent material (28).

6. The evaporative emissions canister of claim 5, wherein: The first zone (20) includes a layer of a third absorbent material (30) having a flow restriction that is higher than the flow restriction of the first absorbent material (26).

7. The evaporative emissions canister of claim 6, wherein: The third absorbent material (30) is the same as the second absorbent material (28).

8. The evaporative emission canister according to any one of claims 5-7, wherein: The first region (120) includes a volume of void space (138).

9. The evaporative emission canister according to any one of claims 1 to 8, wherein: The height of the first absorbent material (26) layer in the direction from the inlet (14) to the outlet (16) is smaller than the height of the second absorbent material (28) layer in the direction (F).

10. The evaporative emission canister of any one of claims 1-9, wherein: The change in cross-sectional area in the transition zone (24) is step-shaped in the direction from the inlet (14) to the outlet (16).

11. A fuel vapor storage canister (10) for absorbing fuel evaporated in a fuel tank of a motor vehicle, the fuel vapor storage canister comprising: a housing (12) forming a body defining at least one chamber therein; a vent port (18) in the body, the vent port venting to atmosphere; a purge port (16) in the body, the purge port being on an end of the body opposite the vent port and in fluid communication with an air intake system of the vehicle; The at least one chamber has a cross-sectional area that varies in a direction (F) from the vent port (18) to the purge port (16); and The at least one chamber includes a first bed of absorbent material (26) and a second bed of absorbent material (28), the first absorbent material having a flow restriction lower than a flow restriction of the second absorbent material; wherein the first absorbent material (26) bed is arranged at or directly adjacent to a transition zone (24), the transition zone (24) changes the cross-sectional area of ​​the at least one chamber in a direction (F) from the ventilation port (18) to the purge port (16), and the first absorbent material bed is arranged adjacent to and immediately upstream of the second absorbent material (28) bed in the direction.

12. The fuel vapor storage canister according to claim 11, wherein: The average particle size of the first absorbent material (26) is at least 1.2 times the average particle size of the second absorbent material (28).

13. The fuel vapor storage canister according to claim 11 or 12, wherein: The first getter material (26) is particulate carbon and the second getter material (28) is granular carbon.

14. The fuel vapor storage canister according to any one of claims 11 to 13, wherein: The change in cross-sectional area in the transition zone (24) is step-shaped in the direction (F) from the ventilation port (18) to the purge port (16).

15. A method of manufacturing an evaporative emissions canister (10), the method comprising the steps of: Providing a housing (12) having an interior volume, an inlet (14) and an outlet (16) in fluid communication with the interior volume, and a fluid flow path defined from the inlet through the interior volume of the housing to the outlet, the fluid flow path having a cross-sectional area that varies in a direction (F) from the inlet to the outlet, the fluid flow path including a transition zone (24) that changes cross-sectional area in a direction from the inlet to the outlet; disposing a first absorbent material (26) layer at or directly adjacent to the transition region; disposing a second layer of absorbent material (28) adjacent to and immediately downstream of the first layer of absorbent material in said direction; wherein the first absorbent material (26) has a flow restriction that is lower than the flow restriction of the second absorbent material (28), and the first absorbent material layer diffuses fluid flow along the fluid flow path into the second absorbent material layer.

16. The method according to claim 15, wherein: The average particle size of the first absorbent material (26) is at least 1.2 times the average particle size of the second absorbent material (28).

17. The method according to claim 15 or 16, wherein: The first getter material (26) is particulate carbon and the second getter material (28) is granular carbon.

18. The method according to any one of claims 15 to 17, wherein: The change in cross-sectional area in the transition zone (24) is step-shaped in the direction from the inlet (14) to the outlet (16).

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