Patent Application
20130291734
The present disclosure relates to a carbon canister having an integrated retainer filter/strainer with slots to facilitate vapor flow and enhanced injection molding tool life.
Carbon canisters containing activated carbon have been used on automotive vehicles to reduce or prevent fuel vapors from the fuel tank escaping to atmosphere. The vapor storage canister is coupled to the vehicle fuel tank as well as the vehicle engine with a vent valve to atmosphere. The activated carbon pellets in the canister absorb fuel vapors from the fuel tank during refueling, as well as fuel vapors associated with diurnal temperature variation. The stored fuel vapors are periodically purged from the carbon pellets by passing air from atmosphere over the pellets to desorb the fuel, with the fuel vapor inducted by the engine and combusted during engine operation.
The activated carbon pellets are added to the canister during assembly. A permanent filter, such as a foam filter, may be used at each entry/exit port to retain the pellets and any small particles that may dislodge during assembly or subsequent operation. The size of each port is determined in conjunction with the filter characteristics to maintain a desired flow rate through the filter/port while accommodating some reduction in flow rate due to anticipated filter clogging. A decreased filter/port flow rate may result in incomplete purging, or require longer time to purge the stored fuel vapors during engine operation. It is desirable to reduce the number of components of the canister assembly while providing a filter that contains the activated carbon within the canister. In addition, the filter should provide efficient flow through load, purge, and vent ports to provide acceptable purge cycle times. The present disclosure recognizes that some prior integrated filter designs are acceptable for many applications, but may impact reliability and durability of injection mold tooling, and alternative designs may improve flow for more efficient purging.
A carbon canister for use in a vapor recovery system of a vehicle having an internal combustion engine and a fuel system includes a housing defining a cavity configured to hold activated carbon including a first chamber having a purge port and a recovery port, a second chamber fluidly coupled to the first chamber and to atmosphere, and a first integrated filter of unitary construction having a cylindrical portion connected to a first spherical frustum having a first plurality of longer radial slots interposed a second plurality of shorter radial slots. The filter may extend within the first chamber of the housing and may also include a third plurality of slots disposed in a generally flat portion of the first spherical frustum. The housing may include a second integrated filter of unitary construction having a cylindrical portion connected to a second spherical frustum having a fourth plurality of longer radial slots interposed a fifth plurality of shorter radial slots, the second integrated filter extending within the second chamber. The second integrated filter may include an eighth plurality of slots disposed in a generally flat portion of the second spherical frustum. The housing may also include a third integrated filter of unitary construction extending into the first chamber and having a generally cuboid shape with a sixth plurality of slots extending from four corresponding sides to a fifth side and a seventh plurality of slots in the fifth side. The housing may also include a third chamber disposed between the first and second chambers. The housing and integrated filters may be formed from a single material to provide a unitary construction, such as by injection molding, for example.
In one embodiment, a fuel vapor recovery system for a vehicle having a fuel system and an internal combustion engine includes a carbon canister having an injection molded housing of unitary construction including a first chamber having a purge port configured for connection to the internal combustion engine and a recovery port configured for connection to the fuel system, a second chamber fluidly coupled to the first chamber, and a third chamber fluidly coupled to the second chamber and configured for connection to atmosphere, the canister including first and second integrated frustospherical filters extending into the first and third chambers, respectively, and each having a first plurality of longer radial slots and a second plurality of shorter radial slots disposed between respective ones of the longer radial slots. The housing may also include a third integrated filter having a generally cuboid shape extending into the first chamber, the third integrated filter including a plurality of slots along each of four sides extending to a connected fifth side. The third integrated filter may also include a plurality of slots within the fifth side. Similarly, the first and second integrated filters may each include a plurality of slots within a flat portion of the filter. In one embodiment, the carbon canister comprises activated carbon pellets contained within the first, second, and third chambers, and the slots of the integrated filters are sized to contain the activated carbon pellets within the housing. The carbon canister may also include a bottom plate secured to the housing.
Various embodiments according to the present disclosure include a method of making a carbon canister that includes forming a housing defining a first chamber, a second chamber, and a third chamber, each having an integrated filter extending into a respective chamber with a generally flat terminus and having a first plurality of elongated slots around a periphery and a second plurality of elongated slots in the generally flat terminus. The method may include forming at least one integrated filter having a third plurality of elongated slots disposed between respective slots of the first plurality of elongated slots. In one embodiment, the method includes forming integrated filters extending into the first chamber and the third chamber that comprise spherical frustums. In one embodiment, the method includes forming the housing with integrated filters by injection molding.
Fuel vapor recovery systems incorporating a carbon canister having one or more integrated filters according to various embodiments of the present disclosure may provide a number of associated advantages. For example, the retainer integrated filter(s) at the inlet and outlet ports of the canister function to contain the carbon bed within the canister, while allowing for the adsorption and desorption of fuel vapors for selective storing and recovery, respectively. Forming of the integrated retainer filter with three-dimensional slot feature(s) as a unitary part of the canister shell or housing provides more open area for vapor flow to facilitate efficient vapor storage or loading of the activated carbon, and subsequent purging. The three-dimensional slots provide a better flow through the canister, which prevents plugging while still keeping the carbon bed intact.
To provide desired flow characteristics, the three-dimensional slot features are designed, in one embodiment, to maximize the openings on the three-dimensional surfaces to achieve the least flow restriction. As such, the integrated retainer filters include primary and secondary slot patterns on all geometries, which may include domes, cylinders, parabolas, and the like. The slots may be located on any of these geometries. Various embodiments include slots on a dome/cylindrical shape geometry with a primary pattern of slots having longer length slots spread on the overall three dimensional surface, and a secondary pattern having shorter length slots located between the longer slots nearer the wide side of the geometry to efficiently utilize all the space of the geometry for less restriction.
A carbon canister having an integrated three-dimensional filter with multiple slot patterns according to embodiments of the present disclosure may also extend tooling life. The combination of the spherical and linear geometries of the slot features according to various embodiments of the present disclosure provides a better lock-in interface between the injection molding cavity and the core of the mold tooling to facilitate improved stabilization and structure strength of the tool during the injection/filling of the mold. In particular, the primary and secondary slots through any spherical/cylindrical portions provide strength and allow more mold steel surface-to-surface contact area between the core and the cavity to better withstand the injection pressure difference that can be generated by an unbalanced filling. As a result, there is less deflection on the tool, which improves reliability and durability of the tooling.
As those of ordinary skill in the art will understand, various features of the embodiments illustrated and described with reference to any one of the Figures may be combined with features illustrated in one or more other Figures to produce alternative embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of the present disclosure may be desired for particular applications or implementations. Those of ordinary skill in the art may recognize similar applications or implementations whether or not explicitly described or illustrated.
Carbon canister 14 also has a vent port 18 fluidly coupled to atmosphere. When gases exit carbon canister 14 through vent port 18, all, or substantially all, of the fuel has been removed from the gases displaced from the fuel tank and adsorbed by the carbon pellets 50. Vent port 18 may be coupled to a vent valve and to a coarse foam or media filter (not shown). The vent valve may be implemented by a controllable valve in communication with the vehicle/engine controller 26, or may be a passive or mechanically operated valve. The vent valve as well as purge valve 24 may be selectively opened and closed during various operating modes, such as a recovery (or vapor storage or loading) mode, purge mode, or diagnostic mode, for example.
A refueling operation is generally illustrated in
Activated carbon has a limited ability to store fuel and is therefore periodically unloaded or purged as generally illustrated in
In one embodiment, a fuel vapor recovery system such as illustrated in
As generally illustrated in
As also shown in
As best illustrated in
As also illustrated in
Block 710, which may be performed simultaneously during forming of the housing and integrated filters of a unitary construction as represented by block 700, may include forming a first plurality of elongated slots around a periphery of the filters. Block 710 may optionally include forming shorter elongated radial slots between respective longer elongated radial slots as represented by block 712. Block 720, which may be performed simultaneously during forming of the housing integrated filters as represented by block 700, may include forming a second plurality of elongated slots in the generally flat terminus. As previously described, one or more integrated filters may be formed such that each extends into the housing. In one embodiment, integrated filters are formed such that integrated filters extending into the first chamber and the third chamber of the housing comprise hemispherical frustums.
As demonstrated by the previously described and illustrated representative embodiments, fuel vapor recovery systems incorporating a carbon canister having one or more integrated filters(s) at the inlet and outlet ports of the canister function to contain the carbon bed within the canister, while allowing for the adsorption and desorption of fuel vapors for selective storing and recovery, respectively. Forming of the integrated retainer filter with three-dimensional slot feature(s) as a unitary part of the canister shell or housing provides more open area for vapor flow to facilitate efficient vapor storage or loading of the activated carbon, and subsequent purging. The three-dimensional slots provide a better flow through the canister, which prevents plugging while still keeping the carbon bed intact. In addition, a carbon canister having an integrated three-dimensional filter with multiple slot patterns according to embodiments of the present disclosure may also extend tooling life. In particular, the combination of hemispherical and linear/cylindrical geometries of the slot features according to various embodiments of the present disclosure provides a better lock-in interface between the injection molding cavity and the core of the mold tooling to facilitate improved stabilization and structure strength of the tool during the injection/filling of the mold. The primary and secondary slots through the spherical/cylindrical portions provide strength and allow more mold steel surface-to-surface contact area between the core and the cavity to better withstand the injection pressure difference that can be generated by an unbalanced filling. As a result, there is less deflection on the tool, which improves reliability and durability of the tooling.
While the best mode has been described in detail with respect to particular embodiments, those familiar with the art will recognize various alternative designs and embodiments within the scope of the following claims. While various embodiments may have been described as providing advantages or being preferred over other embodiments with respect to one or more desired characteristics, as one skilled in the art is aware, one or more characteristics may be compromised to achieve desired system attributes, which may depend on the specific application and implementation. These attributes may include, but are not limited to: cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. The embodiments described herein that are characterized as less desirable than other embodiments or background art implementations with respect to one or more characteristics are not outside the scope of the disclosure and may be desirable for particular applications.
