Vaporized fuel treatment apparatus

A vaporized fuel treatment apparatus having comprising a first adsorbent having a honeycomb structure capable of adsorbing and desorbing vapor contained in fuel evaporation gas, a case configured to house the first adsorbent therein, and a holding device configured to elastically hold the first adsorbent within the case. The first adsorbent has a circumferential surface and at least one end surface intersecting with the circumferential surface at a corner portion. The holding device comprises a holding member having a first portion and a second portion configured to contact with the circumferential surface and the at least one end surface, respectively. The holding member does not contact with the corner portion of the first adsorbent. The vaporized fuel treatment apparatus can include a sealed container disposed in a canister for controlling temperature alteration in the canister.

This application claims priority to Japanese patent application serial numbers 2008-059423 and 2008-070754, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to vaporized fuel treatment apparatuses that are mainly adapted to be mounted on vehicles.

One example of known vaporized fuel treatment apparatuses will be described.FIG. 31shows a cross sectional view of one of the vaporized fuel treatment apparatus.

As shown inFIG. 31, a vaporized fuel treatment apparatus201has a molded adsorbent202with a honeycomb structure capable of adsorbing and desorbing vapor contained in a fuel evaporation gas, a case203for housing the molded adsorbent202, and a pair of holding members204and205for elastically holding the molded adsorbent202in the case203. The holding member204disposed on a front side (right side inFIG. 31) of the molded adsorbent202with respect to an insertion direction of the molded adsorbent202is formed in a ring shape and includes a circumference surface holding portion204aengaging with an outer circumference surface of the molded adsorbent202, and an end surface holding portion204bengaging with an end surface of the molded adsorbent202. On the other hand, the holding member205disposed on the other side (left side inFIG. 31) of the molded adsorbent202with respect to the insertion direction is formed in a ring shape for engaging with the outer circumference surface of the molded adsorbent202. In addition, a filter206made of a non-woven cloth is disposed to oppose to the second surface of the molded adsorbent202(left surface inFIG. 31) in order to entirely cover the second surface. This type of vaporized fuel treatment apparatus is disclosed, for example, in Japanese Laid-Open Patent Publication No. 2004-100691 (see paragraph [0082] and FIG. 17).

The molded adsorbent202generally has a low mechanical intensity, and especially a shoulder portion202aformed between the outer circumference surface and the first end surface with respect to an axial direction (the insertion direction) (hereinafter simply referred to as “front end surface”) is weak and fragile. Therefore, when the holding member204having the circumference surface204acontacting with the outer circumference surface of the molded adsorbent202and the end surface holding portion204bcontacting with the end surface of the molded adsorbent202is used, there has been a problem that the shoulder portion202aof the molded adsorbent202may be damaged during the mounting operation of the holding member204on the molded adsorbent202.

U.S. Pat. No. 5,861,050 discloses a vaporized fuel treatment apparatus including a canister filled with an adsorbent capable of adsorbing vapor generated in a fuel tank. A latent heat storage material is disposed with the canister for inhibiting change in temperature within the canister.

In this vaporized fuel treatment apparatus, the latent heat storage material utilizes latent heat that may be generated during solidification or melting for inhibiting change in temperature and is contained within a sealed container housed within the canister.

When the latent heat storage material absorbs heat and melts, the volume of the latent heat storage material generally increases, and thus a mechanism for compensating the volume increase of the latent heat storage material may be required. However, such a mechanism for compensating the volume increase of the latent heat storage material is not disclosed in U.S. Pat. No. 5,861,050.

BRIEF SUMMARY OF THE INVENTION

One aspect according to the present invention includes vaporized fuel treatment apparatuses having a first adsorbent having a honeycomb structure capable of adsorbing and desorbing vapor contained in fuel evaporation gas, a case configured to house the molded adsorbent therein, and a holding device configured to elastically hold the molded adsorbent within the case. The molded adsorbent has a circumferential surface and at least one end surface intersecting with the circumferential surface at a corner portion. The holding device includes a holding member having a first portion and a second portion configured to contact with the circumferential surface and the at least one end surface, respectively. The holding member does not contact with the corner portion of the molded adsorbent.

In accordance with the present invention, since the first portion of the holding member engages with the circumference surface of the molded adsorbent whereas the second portion engages with the at least end surface of the molded adsorbent, the molded adsorbent can be elastically held in the case. In that state, the holding member does not contact with the corner portion of the molded adsorbent, and thus potential breakage of the corner portion of the molded adsorbent due to the holding member can be prevented or reduced.

Second aspect of the present invention includes vaporized fuel treatment apparatuses further including a canister filled with a particle adsorbent capable of adsorbing and desorbing the vapor, a heat storage material capable of inhibiting alteration in temperature within the canister by producing latent heat when the heat storage material is solidified or melted, and a sealed container containing the heat storage material therein and disposed within the canister. The sealed container includes a gas capable of compensating potential increase in volume of the heat storage material due to melting.

In accordance with the present invention, since the sealed container includes the gas for compensating the volume increase of the heat storage material. Therefore, for example, when the volume of the heat storage material increases during melting, the gas can be compressed in order to compensate the volume increase of the heat storage material, thereby avoiding to exert an excess stress on the sealed container.

In this specification, the term “molded adsorbent” means a formed permeable adsorbent having a honeycomb structure (also referred to as monolith) and made from a mixture of an activated carbon and a binder, and the term “adsorbent” generally means an adsorbent in, e.g., powder or particle form.

DETAILED DESCRIPTION OF THE INVENTION

A vaporized fuel treatment apparatus according to a first embodiment will be described in reference toFIGS. 1-6. As shown inFIG. 1, a vaporized fuel treatment apparatus10includes a case assembly12that has a primary case14, a secondary case16separated from the primary case14and a communication pipe18for communicating the primary case14with the secondary case16. For the purpose of explanation, terms “front”, “rear”, “right” and “left” used in the following explanation are those as viewed inFIG. 1.

The primary case14has a hollow box shape. The primary case14has a case main body20with a closed top and an open bottom, and a lid plate21for closing the open bottom of the case main body20. A tank port23, a purge port24and a connection port25are disposed at a first portion of the primary case14. The tank port23is connected with a fuel evaporation gas pathway (not shown) for communicating with a fuel tank (not shown). The fuel evaporation gas that may be generated in the fuel tank can be introduced into the primary case14via the fuel evaporation gas pathway and the tank port23. The fuel evaporation gas may be a mixture of vaporized hydrocarbon compound (hereinafter simply referred to as “vapor”) and air.

The purge port24is connected with a purge pathway (not shown) communicated with an intake air pipe of an engine (not shown). A purge control valve (not shown) is disposed in the purge pathway. During the operation of the engine, the purge control valve is regulated by a controller in order to carry out a purge control for desorption of the vapor. In addition, the connection port25is connected with one end of the communication pipe18.

The primary case14is filled with a particle adsorbent (not shown). The adsorbent can adsorb the vapor contained in the fuel evaporation gas introduced into the primary case14from the tank port23, and is made of granulated activated carbon, fractured activated carbon or the like.

The secondary case16has a cylindrical tubular portion27with a hollow cylindrical shape, and a lid portion28for closing a front opening of the cylindrical tubular portion27. A connection port30communicating within the secondary case16is provided on the lid portion28. The connection port30is connected with the other end of the communication pipe18. Accordingly, the inner space of the primary case14and the inner space of the secondary case16are communicated with each other via the communication pipe18. In addition, an atmospheric port31having a reduced open diameter is provided on a rear end portion of the secondary case16. The atmospheric port31is connected with an atmospheric pathway (not shown) communicating with the atmosphere. In addition, a cylindrical tubular cover32for covering an outer circumference of the atmospheric port31is provided at a rear end of the secondary case16. The secondary case16is attached to a side surface of the primary case14. The cylindrical tubular portion27is formed in a gradually tapered shape such that an inner diameter of a front side close to the lid portion21is larger than that of an opposite side close to the atmospheric port31.

A molded adsorbent34with a honeycomb structure is housed in the cylindrical tubular portion27of the secondary case16.FIG. 2is a perspective view of the molded adsorbent34.

As shown inFIG. 2, the molded adsorbent34has a cylindrical shape, and has a number of gas passage holes35extending in an axial direction of the molded adsorbent34(in the longitudinal direction inFIG. 1). When the fuel evaporation gas passes through the gas passage holes35, the molded adsorbent34can adsorb the vapor contained in the fuel evaporation gas. Corner portions formed between an outer circumference surface and opposite end surfaces of the molded adsorbent34will be referred to as shoulder portions34a.The molded adsorbent34may be made by the process of mixing a material having a high heat capacity, such as ceramic material, an adsorbent, such as activated carbon, and a binder at a predetermined ratio, molding the mixture into a predetermined shape, such as a cylinder shape, and then sintering the molded mixture.

As shown inFIG. 1, the molded adsorbent34is resiliently held between a pair of first and second holding members37and38within the cylindrical tubular portion27of the secondary case16. The first holding member37is close to or in contact with a gas permeable filter40disposed on a front end portion of the atmospheric port31. A ring-shaped pressing member42is concentrically placed on the second holding member38. In addition, after concentrically placing a press spring43composed of a coil spring on the pressing member42, the lid portion28is attached to the front opening of the cylindrical tubular portion27by welding or adhering. The press spring43resiliently applies a pressing force against the molded adsorbent34.

In operation, the fuel evaporation gas generated in the fuel tank may be introduced into the primary case14via the tank port23. The fuel evaporation gas flows through clearances between the adsorbent particles housed in the primary case14, and then flows into the secondary case16through the connection port25, the communication pipe18and the connection port30. The fuel evaporation gas flows through the gas passage holes35of the molded adsorbent34(shown inFIG. 2), and is then discharged into the atmosphere through the atmospheric port31. During these processes, the adsorbent in the primary case14adsorbs the vapor in the fuel evaporation gas, and the molded adsorbent34in the secondary case16adsorbs the rest of the vapor in the fuel evaporation gas. As a result, the gas that does not substantially contain the fuel component is discharged from the atmospheric port31.

On the other hand, due to the purge control during the engine operation, when the purge control valve is opened by the operation of the controller (not shown), the air outside is drawn into the secondary case16through the atmospheric port31of the secondary case16since a negative pressure within the intake air pipe is introduced into the primary case14through the purge port24. Therefore, the air is purged into the intake air pipe as it flows through the gas passage holes35of the molded adsorbent34, the communication pipe18, the clearances between the adsorbent particles contained within the primary case14, and the purge port24. During this process, the vapor is desorbed from the adsorbent particles and the molded adsorbent34and introduced into the air intake pipe.

Next, the holding structure for the molded adsorbent34according to the vaporized fuel treatment apparatus10will be described. Since the first and second holding members37and38have the substantially same structure, only the first holding member37will be described, and differences of the holding member38from the holding member37will be additionally described. As for the holding member38, the same or substantially same portions as the first holding member37are labeled with the same reference numbers as the first holding member37.

As shown inFIG. 5, the first holding member37is formed in a ring shape from an elastic material. In addition, as shown inFIG. 6, the first holding member37is configured to have a substantially L-shaped cross section and has a circumference surface holding portion45for engaging with an outer circumferential surface of the molded adsorbent34and an end surface holding portion47for engaging with an end surface of the molded adsorbent34. A relief recess49is formed in an inner circumferential portion of the holding member37and has an L-shape cross section so as to oppose to the shoulder portion34aof the molded adsorbent34when the holding member37is attached to the molded adsorbent34. The relief recess49is continuously formed over the whole circumference of the holding member38. A lip sealing portion51with a tapered cylindrical shape is formed on a free end portion of the circumference surface holding portion45(rear end inFIG. 6). The outer diameter of the lip sealing portion51increases in an opposite direction to the insertion direction of the molded adsorbent34(the opposite direction being forward inFIG. 3or rearward inFIG. 6). The first holding member37is made from a gas impermeable elastic material.

The first and second holding members37and38are symmetrically positioned with respect to the molded adsorbent34(refer toFIGS. 3 and 4). In addition, a lip sealing portion51of the second holding member38is formed on an outer circumferential surface of the circumference surface holding portion45and has a tapered shape, in which the outer diameter increases toward the direction opposite to the insertion direction of the molded adsorbent34.

Prior to the inserting operation of the molded adsorbent34into the cylindrical tubular portion27of the secondary case16, the first holding member37is resiliently fitted to a first end (a rear end inFIG. 1) of the molded adsorbent34(refer toFIGS. 3,5and6). In addition, the second holding member38is resiliently fitted to a second end (a front end inFIG. 1) of the molded adsorbent34(refer toFIG. 4).

The molded adsorbent34having the holding members37and38attached thereto are then inserted into the cylindrical tubular portion27of the secondary case16before attachment of the lid portion28. Therefore, as shown inFIG. 3, a large diameter-side end of the lip sealing portion51of the first holding member37resiliently contacts with the inner circumferential surface of the cylindrical tubular portion27while a clearance exists between the outer circumferential surface of the circumference surface holding portion45of the first holding member37and the inner circumferential surface of the cylindrical tubular portion27. In addition, as shown inFIG. 4, a large diameter-side end of the lip sealing portion51of the second holding member38resiliently contacts with the inner circumferential surface of the cylindrical tubular portion27while a clearance exists between an outer circumferential surface of the circumference surface holding portion45of the second holding member38and the inner circumferential surface of the cylindrical tubular portion27. As a result, the molded adsorbent34is resiliently held within the cylindrical tubular portion27by the first and second holding members37and38. The first and second holding members37and38can elastically seal a space defined between the cylindrical tubular portion27and the molded adsorbent34. The end surface holding portion47of the first holding member37is close to or in contact with the filter40(refer toFIG. 3). In addition, a ring-shaped pressing portion42aformed on the pressing member42bears against the end surface holding portion47of the second holding member38(refer toFIG. 4).

According to the vaporized fuel treatment apparatus10, the circumference surface holding portions45of the first and second holding members37and38can engage with the outer circumferential surface of the molded adsorbent34. In addition, the end surface holding portions47of the holding members37and38can engage with the opposite end surfaces of the molded adsorbent34. Therefore, the molded adsorbent34can be resiliently held within the case assembly12(in particular, within the secondary case16). Since the relief recesses49are formed on the first and second holding members37and38and are opposed to the shoulder portions34aformed between the outer circumference surface and the opposite end surfaces of the molded adsorbent34, it is possible to avoid contact of the shoulder portions34awith the holding members37and38. Accordingly, potential damage of the shoulder portions34aof the molded adsorbent34due to contact with the holding members37and38can be prevented or reduced. In an alternative embodiment, the vaporized fuel treatment apparatus10may be composed of only the secondary case16having the molded adsorbent34without the primary case14and the communication pipe18.

Second to eighth embodiments will now be described with reference toFIGS. 7 to 25. These embodiments are modifications of the first embodiment. Therefore, inFIGS. 7 to 25, like members are given the same reference numbers as the first embodiment, and the description of these members will not be repeated.

A second embodiment will be described with reference toFIG. 7. A vaporized fuel treatment apparatus110of this embodiment does not include the secondary case16and the communication pipe18. In addition, a cylindrical tubular portion127having the same structure as the cylindrical tubular portion27of the first embodiment is formed on a side portion of the case main body20of the primary case14. The atmospheric port31and the cylindrical tubular cover32are oriented to be positioned on the front side of the case main body20, and an open side end portion (a rear end portion inFIG. 7) of the cylindrical tubular portion127has an opening that is spaced away from the lid plate21by a predetermined distance. Therefore, the cylindrical tubular portion127is communicated with the inner space of the case main body20through a clearance near the lid plate21.

A perforated pressing member112is provided within a portion adjacent the rear side of the center portion of the cylindrical tubular portion127instead of the pressing member42of the first embodiment. Similar to the pressing member42, the pressing member112has a ring-shaped pressing member112afor bearing against the end surface holding portion47of the second holding member38(refer toFIG. 4).

A gas permeable press plate114is perpendicularly fitted within a rear opening of the cylindrical tubular portion127such that it can move in a horizontal direction within the rear opening. A pressing spring115composed of a coil spring and resiliently pressing the press plate114forwardly is disposed between the press plate114and the lid plate21. A space defined between the pressing member112and the press plate114is filled with particle adsorbent118made of activated carbon. In addition, a gas permeable filter116is laid on the press plate114.

A third embodiment will now be described with reference toFIGS. 8 and 9. According to the third embodiment, a cross-shape rib portion53is formed on the end surface holding portion47of the first holding member37in order to reinforce the end surface holding portion47. Other than the cross shape, the rib portion53can be formed in various shapes, such as a straight shape, a three spoke shape or a mesh-like shape, as long as the end surface holding portion47can be reinforced. A reinforcing structure like the rib portion53can also be applied to the end surface holding portion47of the second holding member38.

A fourth embodiment will now be described with reference toFIGS. 10-14. In accordance with the fourth embodiment, the holding structure for the molded adsorbent34of the first embodiment is modified. For the purpose of explanation, a holding member55and a holding member56positioned on the rear side and the front side inFIG. 10will be referred to as a first holding member55and a second holding member56, respectively. In addition, since the first holding member55and the second holding member56have substantially the same configuration, only the first holding member55will be described, and differences of the second holding member56from the first holding member55will be described additionally. InFIGS. 10-14, components of the second holding member56that are the same or similar to components of the first holding member56are labeled with the same reference numbers as the first holding member56.

As shown inFIGS. 13 and 14, the first holding member55of this embodiment has a circumference surface holding member58for engaging with the outer circumference surface of the molded adsorbent34and an end surface holding member60adapted to be held in contact with the end surface of the molded adsorbent34. The circumference surface holding member58is made from a gas impermeable elastic material. The end surface holding member60is made from a gas permeable elastic material, such as urethane form, and has a lower elasticity than the circumference surface holding member58. The end surface holding member60is formed in a disk shape covering the whole of the end surface of the molded adsorbent34.

The circumference surface holding member58is formed in a ring shape. The circumference surface holding member58is configured to have an L-shape cross section and includes a primary holding portion58afor engaging with the outer circumference surface of the molded adsorbent34and a secondary holding portion58bfor keeping the end surface holding member60in contact with the end surface of the molded adsorbent34. A lip sealing portion61with a tapered cylindrical shape is formed on a free end portion (a lower end portion inFIG. 14) of the primary holding member58a. The lip sealing portion61is formed in a lip shape gradually increasing its outer diameter in the opposite direction to the insertion direction of the molded adsorbent34. Thus, the outer diameter of the lip sealing portion61increases forwardly inFIG. 11or rearwardly inFIG. 14.

The circumference surface holding members58of the first holding member55and the second holding member56are disposed symmetrically with respect to the molded adsorbent34. In addition, a lip seal portion61of the circumference surface holding member58of the second holding member56is formed in a tapered shape and extends from an outer circumference surface of the circumference surface holding member58such that an outer diameter of the lip sealing portion61gradually increases forwardly inFIG. 12or in the opposite direction to the insertion direction of the molded adsorbent34.

Prior to the insertion of the molded adsorbent34into the cylindrical tubular portion27of the secondary case16, the first holding member55is attached to a first end portion (a rear end portion inFIG. 10) in the insertion direction of the molded adsorbent34. More specifically, the circumference surface holding member58of the first holding member55is resiliently fitted with the first end portion (a rear end portion inFIG. 11or a front end portion inFIG. 14) of the molded adsorbent34, while the end surface holding member60of the first holding member55is in surface contact with a first end surface of the molded adsorbent34(seeFIGS. 11,13and14).

In addition, the second holding member56is attached to a second end (a front end inFIG. 10) opposite to the first end of the molded adsorbent34such that the first holding member55and the second holding member56are symmetrically positioned with respect to the molded adsorbent34. More specifically, the circumference surface holding member58of the second holding member56is resiliently fitted with the second end portion (the front end portion inFIG. 12) of the molded adsorbent34opposite to the first end portion, while the end surface holding member60is in surface contact with a second end surface of the molded adsorbent34(refer toFIG. 12).

Thereafter, the molded adsorbent34having the first and second holding members55,56fitted thereto is inserted into the cylindrical tubular portion27of the secondary case16before attachment of the lid portion28. Accordingly, as shown inFIG. 11, a large diameter-side end portion of the lip sealing portion61of the first holding member55resiliently contacts with the inner surface of the cylindrical tubular portion27while a clearance exists between an outer circumference surface of the primary holding portion58aof the first holding member55and the inner surface of the cylindrical tubular portion27. In addition, as shown inFIG. 12, a large diameter-side end portion of the lip sealing portion61of the second holding member56resiliently contacts with the inner surface of the cylindrical tubular portion27while a clearance exists between an outer circumferential surface of the primary holding portion58aof the circumference surface holding member58of the second holding member56and the inner surface of the cylindrical tubular portion27. Therefore, the molded adsorbent34is resiliently held within the cylindrical tubular portion27by the first and second holding members55and56. A space defined between the cylindrical tubular portion27and the molded adsorbent34is elastically sealed with the circumference surface holding members58of the holding members55and56. The secondary holding portion58bof the circumference surface holding member58of the first holding member55is close to or in contact with the filter40(refer toFIG. 11). The pressing portion42aof the pressing member42bears against the secondary holding portion58bof the circumference holding member58of the second holding member56(refer toFIG. 12).

In accordance with the vaporized fuel treatment apparatus10of this embodiment, the circumference surface holding members58of the first and second holding members55and56contact with the outer circumference surface of the molded adsorbent34, and the end surface holding members60of the first and second holding members55and56contact with the opposite end surfaces of the molded adsorbent34, and thus the molded adsorbent34can be resiliently held within the case assembly12(in particular, within the secondary case16). Since the end surface holding members60have lower elasticity than the circumference surface holding members58, it is possible to reduce a force that may be applied to the shoulder portion34aof the molded adsorbent34. Therefore, potential damage of the shoulder portion34aof the molded adsorbent34due to the forces applied by the holding members55and56can be prevented or reduced.

The end surface holding members60have gas permeability and cover the entire end surfaces of the molded adsorbent34. Accordingly, the end surface holding members60can ensure flow of the gas into or out of the molded adsorbent34while protecting the entire end surfaces of the molded adsorbent34. In addition, since the end surface holding members60are opposed to the entire end surfaces of the molded adsorbent34, decrease of adsorption ability of the molded adsorbent34, which may be caused in the case that gas impermeable elements are opposed to the end surfaces of the molded adsorbent34, can be prevented.

A fifth embodiment will now be described with reference toFIG. 15. This embodiment is a modification of the second embodiment. According to this embodiment, the first holding member37of the second embodiment (refer toFIG. 7) is replaced with the first holding member55of the fourth embodiment, and the second holding member38of the second embodiment is replaced with the second holding member56of the fourth embodiment.

A sixth embodiment will now be described with reference toFIGS. 16 and 17. This embodiment is a modification of the fourth embodiment. In accordance with the sixth embodiment, the secondary holding portion58bof the circumference surface holding member58of the first holding member55in the fourth embodiment (refer toFIGS. 13 and 14) is modified as a secondary holding portion58cwith a cross-shape rib form. It is possible to reinforce the primary holding portion58aby providing the rib shaped secondary holding portion58cin the primary holding portion58aof the circumference surface holding member58. The rib shaped secondary holding portion58cmay be modified to have various shapes, such as a straight form, a three spoke form, and a mesh-like form as long as it can reinforce the primary holding portion58aof the circumference holding member58. The rib shaped secondary holding portion58ccan be applied also to the circumference surface supporting member58of the second holding member56.

A seventh embodiment will now be described with reference toFIGS. 18-24. The seventh embodiment is a modification of the first embodiment. In accordance with the seventh embodiment, the holding structure for the molded adsorbent34in the first embodiment is modified. For the purpose of explanation, a holding member65and a holding member66disposed on the rear side and the front side inFIG. 18will be referred to as a first holding member65and a second holding member66, respectively. In this embodiment, the pressing member42and the pressing spring43in the secondary case16of the first embodiment (refer toFIG. 1) are omitted. The cylindrical tubular portion27of the secondary case16is modified to have a stepped cylindrical shape having front and rear stepped portions. Accordingly, the cylindrical tubular portion27has a first stepped portion68opposed to the first end portion (the rear end portion) of the molded adsorbent34in the insertion direction, and a second stepped portion69opposed to the second end portion (the front end portion) opposite to the first end portion of the molded adsorbent34.

As shown inFIG. 19, the first holding member65has a circumferential surface holding member71for engaging with the outer circumferential surface of the molded adsorbent34and an end surface holding member72for engaging with the first end surface of the molded adsorbent34. The circumferential surface holding member71and the end surface holding member72are separate elements from each other. The circumference surface holding member71is made from a gas impermeable elastic material.

The end surface holding member72is formed from a gas permeable elastic material, such as urethane foam, and has lower elasticity than the circumference surface holding member71. The end surface holding member72is formed in a disk shape, and is fitted within the cylindrical tubular portion27, in particular, within a cylindrical portion on the rear side (the smaller diameter side) of the first stepped portion68. The end surface holding member72is close to or in contact with the filter40. In addition, the first end surface of the molded adsorbent34is in surface contact with the end surface holding member72.

As shown inFIGS. 21 and 22, the circumference surface holding member71is formed in a ring shape. The circumference surface holding member71has a hollow cylindrical attachment base74and a tapered cylindrical lip sealing portion75formed on an inner circumference surface of the attachment base74. As shown inFIG. 19, the attachment base74is elastically fitted within the cylindrical tubular portion27, in particular, within a cylindrical portion on the front side (the larger diameter side) of the first stepped portion68. A ring-shape space is defined between the attachment base74and the outer circumferential surface of the molded adsorbent34. The lip sealing portion75is formed in a lip shape and has an inner diameter that gradually decreases in a rearward direction, so that the lip sealing portion75can elastically contact with the outer circumferential surface of the first end portion of the molded adsorbent34.

Next, the second holding member66will be described. As shown inFIG. 20, the second holding member66has a circumference surface holding member77for engaging with the outer circumferential surface of the molded adsorbent34, and an end surface holding member78for engaging with a second end surface of the molded adsorbent34. The circumference surface holding member77and the end surface holding member78are separate members from each other. The circumference surface holding member77is made from an air impermeable elastic material.

The end surface holding member78is made from a gas permeable elastic material, such as urethane foam, and has lower elasticity than the circumference surface holding member77. In addition, the end surface holding member78is formed in a disk shape, and is fitted within the cylindrical tubular portion27(more specifically, a cylindrical portion on a front side (or a larger diameter side) of the second stepped portion69). The end surface holding member78is in surface contact with the second end surface of the molded adsorbent34. In addition, an outer circumferential portion of a lid portion28is in surface contact with an outer circumferential portion of the end surface holding member78.

As shown inFIGS. 23 and 24, the circumference surface holding member77is formed in a ring shape. The circumference surface holding member77has an attachment base80having an annular plate shape, an cylindrical tubular portion81protruding rearwardly from an inner circumferential portion of the attachment base80and having an L-shape cross section, and a pair of inner and outer lip sealing portions82and83with cylindrical shapes tapered toward opposite directions to each other and bifurcating from a rear end portion of the cylindrical tubular portion81. As shown inFIG. 20, the attachment base80is resiliently fitted within the cylindrical tubular portion27(in particular, the cylindrical portion on the front side (or the larger diameter side) of the second stepped portion69) and bears against the stepped portion69. A ring shaped space is defined between an inner circumferential surface of the cylindrical tubular portion81and the outer circumferential surface of the molded adsorbent34, and also a ring shaped space is defined between an outer circumferential surface of the cylindrical tubular portion81and the inner surface of the cylindrical tubular portion27(in particular, the cylindrical tubular portion on the rear side (or the smaller diameter side) of the second stepped portion69). The inner lip sealing portion82is formed in a lip shape having an inner diameter gradually decreasing in the rearward direction, and elastically contacts with the outer circumferential surface of the second end portion of the molded adsorbent34. Whereas, the outer lip sealing portion83is formed in a lip shape having an outer diameter gradually increasing in the rearward direction, and elastically contacts with the inner circumference surface of the cylindrical tubular portion27(in particular, the cylindrical tubular portion on the rear side (or the smaller diameter side) of the second stepped portion69).

In accordance with the above vaporized fuel treatment apparatus10, the circumference surface holding members71and77(in particular, the lip sealing portions75and82) of the holding members65and66engage with the outer circumferential surface of the molded adsorbent34, and the end surface holding members72and78of the holding members65and66engage with the opposite end surfaces of the molded adsorbent34, thereby elastically holding the molded adsorbent34within the case assembly12(in particular, the secondary case16). The circumference surface holding members71and77are formed separately from the end surface holding members72and78, and the end surface holding members72and78have lower elasticity than the circumference surface holding members71and77, thereby reducing the external force that may be applied to the shoulder portions34aof the molded adsorbent34. Therefore, it is possible to prevent or reduce potential damage to the shoulder portions34aof the molded adsorbent34.

The end surface holding members72and78entirely cover the opposite end surfaces of the molded adsorbent34, and have gas permeability. Accordingly, the end surface holding members72and78ensure that the gas can flow into and out of the molded adsorbent34, while entirely protecting the end surfaces of the molded adsorbent34. In addition, since the end surface holding members72and78cover the entire end surfaces of the molded adsorbent34, decrease of the adsorption ability of the molded adsorbent34, which may be caused in the case that gas impermeable elements are opposed to the end surfaces of the molded adsorbent34, can be prevented.

An eighth embodiment will now be described with reference toFIG. 18. This embodiment is a modification of the second embodiment. As shown inFIG. 25, according to the vaporized fuel treatment apparatus110of this embodiment, the first holding member37of the second embodiment (refer toFIG. 7) is replaced with the first holding member65of the seventh embodiment (refer toFIG. 18), and the second holding member38of the second embodiment (refer toFIG. 7) is replaced with the second holding member66of the seventh embodiment. In addition, the cylindrical tubular portion27with two stepped cylindrical shape of the seventh embodiment (refer toFIG. 18) is formed with the primary case14.

A ninth embodiment will now be described with reference toFIGS. 26-30. As shown inFIGS. 26-30, a vaporized fuel treatment apparatus300has a canister320filled with an adsorbent312. As shown inFIGS. 26 and 27, the canister320is composed of a case main body321divided into a plurality of chambers, and a lid portion322for closing a rear opening (positioned on the rear side inFIG. 26) of the case main body321. An inner space of the case main body321is divided into a main chamber324with a substantially rectangular horizontal cross section and an auxiliary chamber325with a substantially circular horizontal cross section by a partition wall321w as shown inFIG. 27. In addition, the auxiliary chamber325is further divided into a first auxiliary chamber325aand a second auxiliary chamber325bby a buffer plate323as shown inFIG. 26.

The case main body321includes a tank port324a, a purge port324band an atmospheric port325carranged in parallel at a front wall portion opposite to the lid portion322inFIG. 26. The atmospheric port325ccommunicates with the first auxiliary chamber325athrough a perforated plate325xhaving a number of small openings. The tank port324aand the purge port324bcommunicate with the main chamber324through a perforated plate324xhaving a plurality of small openings. A partition wall324kprotruding into the main chamber324is formed on the front wall portion of the main chamber324. The inner space of the main chamber324is divided into a first space communicating with the tank port324aand a second space communicating with the purge port324b.

With the lid portion322removed, a plurality of main sealed containers340each containing a heat storage material317therein described below are inserted into the main chamber324of the case main body321such that the main sealed containers340are spaced away from each other in the vertical direction as shown inFIG. 27. In this embodiment, three main sealed containers340are provided. Then, the spaces defined between the main sealed containers340and the spaces defined between the main sealed containers340positioned on opposite sides and an inner wall surface of the main chamber324are filled with the adsorbent312.

The adsorbent312is composed of an activated carbon or the like capable of adsorbing the vapor and also capable of desorbing the vapor when purged by air. The openings of the perforated plate324xare designed to be much smaller than the particle size of the adsorbent312in order to keep the adsorbent312within the main chamber324.

After mounting the main sealed containers340within the main chamber324of the case main body321and introducing the adsorbent312thereinto, the opening of the main chamber324is closed by an inner lid plate327as shown inFIG. 26. The inner lid plate327is a gas permeable plate and is composed of a first filter327fand a perforated plate327x.The inner lid plate327serves to hold the adsorbent312within the main chamber324. The inner lid plate327can slide in the horizontal direction along the inner wall surface of the main chamber324while closing the opening of the main chamber324. A coil spring327shas one end fitted into a center portion of a rear surface of the inner lid plate327. When the opening of the case main body321is closed by the lid portion322, the other end of the coil spring327sis pressed by an inner surface of the lid portion322. Thus, the inner lid plate327is pressed inwardly (forwardly inFIG. 26) into the main chamber324by the coil spring327s. As a result, unnecessarily large spaces may not be produced between particles of the adsorbent312, and thus the resistance of the adsorbent312against flow of gas can be kept at a constant level.

As described above, the auxiliary chamber325of the case main body321is divided into the first auxiliary chamber325aand the second auxiliary chamber325bby the buffer plate323, and a second filter323fis positioned to be opposed to the rear surface of the buffer plate323facing the second auxiliary chamber325b.

With the lid portion322removed, a plurality of auxiliary sealed containers350each filled with a heat storage material317are inserted into the second auxiliary chamber325bof the case main body321such that the auxiliary sealed containers350are spaced away from each other in the vertical direction as shown inFIG. 27. In this embodiment, two auxiliary sealed containers350are provided. Then, the adsorbent312is filled into each of the spaces between the auxiliary sealed containers350and between each of the auxiliary sealed containers350and an inner surface of the second auxiliary chamber325b.

After inserting the auxiliary sealed containers350into the second auxiliary chamber325and introducing the adsorbent312thereinto, the opening of the second auxiliary chamber325bis closed by an inner lid plate329as shown inFIG. 26. The inner lid plate329is a gas permeable plate and is composed of a third filter329fand a perforated plate329x. The inner lid plate329serves to hold the adsorbent312within the second auxiliary chamber325b.

The inner lid plate329can slide in the horizontal direction along the inner surface of the second auxiliary chamber325bwhile closing the opening of the second auxiliary chamber325b. A coil spring329shas one end fitted into a center portion of a rear surface of the inner lid plate329. Accordingly, when the opening of the case main body321is closed by the lid portion322, the inner lid plate329is pressed inwardly (forwardly inFIG. 26) into the second auxiliary chamber325bby the coil spring329s.

A diffusing space326is defined between the lid portion322and the inner lid plate329for closing the opening of the second auxiliary chamber325band between the lid portion322and the inner lid plate327for closing the opening of the main chamber324. The diffusing space326serves to communicate the main chamber324with the second auxiliary chamber325b.

The heat storage material317can reduce alteration in temperature within the canister320by using latent heat that may be produced during solidification or melting of the heat storage material317. For example, hexadecane (C16H34) having a melting point of 18° C. may be used as the heat storage material317. Accordingly, when the temperature within the canister320becomes equal to or higher than 18° C., the heat storage material317melts and absorbs heat within the canister320, thereby inhibiting increase in temperature within the canister320. If the temperature within the canister320becomes lower than 18° C., the heat storage material317emits heat during solidification, thereby inhibiting further temperature decrease within the canister320.

Each of the main sealed containers340containing the heat storage material317therein is formed by joining a flange portion342eof an upper panel342with a flange portion344eof a lower panel344. The upper panel342has a lid-like shape, and the lower panel344has a shallow open box-like shape as shown inFIGS. 28A,28B and29. For example, the upper panel342may be made of a rectangular stainless plate that is formed to have a circumference edge with a uniform width as the flange portion342eas shown inFIG. 28A. The upper panel342has linear groove portions342mand linear raised portions342peach extending in a longitudinal direction of the upper panel342and having a rectangular cross section. The linear groove portions342mand the linear raised portions342pare formed in an area surrounded by the flange portion342eand have a uniform width. The groove portions342mand the raised portions342pare arranged alternately along a widthwise direction of the upper panel342. In the case that the upper panel342is formed by a press molding process of a stainless plate, the raised portions342pon an upper side of the upper panel342may be formed as groove portions as viewed from the lower side, and the groove portions342mon the upper side of the upper panel342may be formed as raised portions as viewed from the lower side (seeFIG. 28B).

The lower panel344has a rectangular shallow box shape and may be formed from a stainless plate to have a circumference edge that has a uniform width as the flange portion344e. The lower panel344has linear groove portions344mand linear raised portions344peach extending in a longitudinal direction of the lower panel344and having a rectangular cross section. The linear groove portions344mand the linear raised portions344pare formed in an area surrounded by the flange portion344eand have a uniform width. The groove portions344mand the raised portions344pare arranged alternately along a widthwise direction of the lower panel344. Similar to the upper panel342, the lower panel344may be formed by a press molding process of a stainless plate. In such a case, the raised portions344pon the lower side of the lower panel344(the outer side of the main sealed container340, refer toFIG. 29) may be formed as groove portions as viewed from the upper side (the inner side of the main sealed container340), and the groove portions344mon the lower side may be formed as raised portions as viewed from the upper side (seeFIG. 28B).

The width and the length of the lower panel344is set to be equal to the width and the length of the upper panel342, and the width of the groove portions344mand the raised portions344pof the lower panel344are set to be equal to the width of the groove portions342mand the raised portions342pof the upper panel342.

With the heat storage material317filled within the main sealed container340, the flange portion344eof the lower panel344and the flange portion342eof the upper panel342are joined to each other, for example, by laser welding, as shown inFIG. 28B. A space S defined within the main sealed container340is filled with helium gas.

As shown inFIG. 27, opposite edges in the widthwise direction of the flange portions342eand344eof each of the main sealed containers340engage with corresponding one of three pairs of rail-shape grooves324gformed on opposite sides in the widthwise direction of an inner surface of the main chamber324of the canister320. Accordingly, the main sealed containers340are mounted within the main chamber324in substantially horizontal manner. The three pairs of the rail-shape grooves324gare arranged at the same intervals in the vertical direction.

Similar to the main sealed containers340, each of the auxiliary sealed containers350contains the heat storage material317and has the substantially same structure as the main sealed container340. However, the size of the auxiliary sealed container350is smaller than the size of the main sealed container340as shown inFIGS. 30A,30B and30C. Therefore, components of the auxiliary sealed container350that are the same or similar to the components of the main sealed container340are labeled with the same reference numbers, and the description of these components will not be repeated.

As shown inFIG. 27, opposite edges in the widthwise direction of the flange portions342eand344eof each auxiliary sealed container350engage with corresponding one of two pairs of rail-shape grooves325gformed in opposite sides in the widthwise direction of an inner surface of the buffer plate323disposed within the second auxiliary chamber325b. Thus, the auxiliary sealed containers350are disposed within the second auxiliary chamber325bin substantially horizontal manner. The two pairs of the rail-shape groove portions325gare spaced away from each other by a predetermined distance in the vertical direction as viewed inFIG. 27.

When a vehicle engine (not shown) is stopped, vapor contained in fuel evaporation gas that may be generated in a fuel tank (not shown) can be introduced into the main chamber324from the tank port324aof the canister320through a vaporized fuel pathway (not shown) as indicated by an outline arrow inFIG. 26. Therefore, the vapor may be adsorbed by the adsorbent312contained within the main chamber324. A part of the vapor, which has not been adsorbed by the adsorbent312within the main chamber324, is introduced into the second auxiliary chamber325bthrough the diffusing space326. As the adsorbent312adsorbs the vapor, the temperature of the adsorbent312gradually increases and thus the adsorptive ability of the adsorbent312gradually decreases. However, each of the main sealed containers340and the auxiliary sealed containers350disposed within the canister320contains the heat storage material317(e.g., hexadecane). Therefore, when the temperature within the canister320exceeds 18° C., the heat storage material317can melt and absorb heat within the canister320, thereby inhibiting temperature increase within the canister320. Accordingly, it is possible to prevent the adsorptive ability of the adsorbent312from being lowered.

As the heat storage material317melts, the volume of the heat storage material317may increase. However, each of the main sealed containers340and the auxiliary sealed containers350has the space S, and thus the volume increase of the heat storage material317can be compensated by the compression of the helium gas contained within the space S. Therefore, no excess force may be applied to the main sealed containers340and the auxiliary sealed containers350.

During the operation of the vehicle engine, a negative pressure produced within an intake air pathway (not shown) may be introduced into the purge port324bof the canister320via a purge pathway (not shown) and further into the main chamber324, the diffusing space326, the second auxiliary chamber325band the first auxiliary chamber325a. Therefore, as indicated by bold arrows inFIG. 26, the ambient air may flow into the first auxiliary chamber325aof the canister320through the ambient port325cand further into the intake air pathway through the second auxiliary chamber325b, the diffusing space326, the main chamber324, the purge port324band the purge pathway. As a result, the vapor adsorbed by the adsorbent312within the canister320can be desorbed, and can be introduced into the intake air pathway along with the flow of air.

As the vapor adsorbed by the adsorbent312is desorbed by the purging operation, the temperature of the adsorbent312decreases to gradually lower the desorptive ability for the vapor. However, when the temperature in the canister320has become equal to or lower than 18° C., the heat storage material317emits heat during solidification, thereby inhibiting temperature decrease within the canister320. Accordingly, it is possible to inhibit decrease in the desorptive efficiency of the adsorbent312for the vapor.

In accordance with the vaporized fuel treatment apparatus300of the present embodiment, each of the sealed containers340and350has the space S that is capable of compensating the volume increase of the heat storage material317and is defined between the inner surface of each of the sealed containers340and350and the surface of the heat storage material317. Thus, in the case that the volume of the heat storage material317has increased during melting of the heat storage material317, such increase in volume can be compensated by the compression of the gas contained within the corresponding space S, and thus no excess stress may be applied to the sealed containers340and350.

In addition, the groove portions344mand the raised portions344pformed on the outer surface of each of the sealed containers340and350may increase the heat exchange efficiency between the corresponding heat storage material317and the adsorbent312contained within the canister320.

Furthermore, the groove portions344mand the raised portions344pare formed on the inner surface of each of the sealed containers340and350, and therefore, even in the case that the sealed containers340and350each containing the heat storage material317in liquid phase have been tilted, the heat storage material317can be prevented from concentrating in one end of each of the sealed containers340and350.

The sealed containers340and350are each formed to have a flattened shape, and disposed within the canister320in substantially horizontal manner. The lower panel344of each of the sealed containers340and350has a surface area larger than that of the upper panel342. The lower panel344has a contact area, with which the heat storage material317in liquid phase contacts, larger than that of the upper panel342, thereby increasing the heat exchange efficiency.

Since each of the spaces S defined within the sealed containers340and350is filled with inert gas such as helium gas, it is possible to prevent potential deterioration of the heat storage material317. In addition, it is possible to check the sealed condition of the sealed containers340and350by detecting leakage of the inert gas.

The plurality of the sealed containers340and350are disposed in the canister320and the second auxiliary chamber325b, respectively. Therefore, although the heat exchange efficiencies of the upper panel342and the lower panel344are different from each other, since most of the adsorbent312are placed close to the lower panel344having higher heat exchange efficiency, the adsorbent312in this embodiment can more efficiently carry out heat exchange with the heat storage material317in the sealed containers340and350than the case that each one of the sealed containers340and350is disposed in the canister320and the second auxiliary chamber325b, respectively.

The above embodiment can be modified in various ways. For example, although hexadecane having a melting point of 18° C. was exemplified as the heat storage material317, the material for the heat storage material317can be changed depending on a necessary or desired control temperature within the canister320. For example, heptadecane (C17H36) having a melting point of 22° C. or any other suitable materials can be used.

In addition, although each of the sealed containers340and350has the groove portions344mand the raised portions344p, the groove portions344mand the raised portions344pmay be replaced with any other depressions and projections as long as they form a concave-convex structure. Furthermore, it is possible to form fins or the like on the surfaces of the sealed containers340and350.

Although the sealed container340and350each having a flattened box shape were exemplified, these sealed containers may have any other suitable shapes.

Although the helium gas was exemplified as the inert gas contained within the sealed containers40and50, argon gas, nitrogen or the like can be used instead of the helium gas.

The above embodiments can be combined with each other. For example, the vaporized fuel treatment apparatus110in the second embodiment can additionally have the main sealed containers340and the auxiliary sealed containers350filled with the heat storage material317and the inert gas in the ninth embodiment. In particular, the whole structures of the vaporized fuel treatment apparatuses110and300in the second and ninth embodiments are similar to each other. One of major differences between the vaporized fuel treatment apparatuses110and300is that the vaporized fuel treatment apparatus300includes the main sealed containers340and the rail-shape grooves324gin the main chamber324and the auxiliary sealed containers350and the rail-shaped grooves325gin the second auxiliary chamber325b. The main sealed containers340and the auxiliary sealed containers350are filled with the heat storage material317and the inert gas, such as helium gas. In addition, the main chamber324including the main sealed containers340and the second auxiliary chamber325bincluding the auxiliary sealed containers350are filled with the adsorbent312. Whereas the case main body20and a rear half of the cylindrical tubular portion127, which correspond to the main chamber324and the second auxiliary chamber325b, respectively, of the second embodiment are merely filled with the particle adsorbent. With respect to the other major differences between the vaporized fuel treatment apparatuses110and300, the vaporized fuel treatment apparatus110has the molded adsorbent34, the first and second holding members37and38in the cylindrical tubular portion127for elastically holding the molded adsorbent34. Accordingly, the vaporized fuel treatment apparatus110having the molded adsorbent34, the first and second holding members37and38can additionally include the main sealed containers340and the rail-shaped grooves324gin the case main body20and the auxiliary sealed containers350and the rail-shaped grooves325gin the rear half of the cylindrical tubular portion127. In the same way, other vaporized fuel treatment apparatuses described above such as the vaporized fuel treatment apparatus10of the first embodiment can include the main and auxiliary sealed containers340and350filled with the heat storage material317and the inert gas and the rail shaped grooves324gand325gfor holding the sealed containers340and350in the main case body20and the cylindrical tubular portion27and127.