FUEL VAPOUR STORAGE CANISTER

Abstract: A canister (l0), adapted to store fuel vapour discharged from a fuel tank by adsorption on a bed (l2) of material such as activated carbon, has an inlet chamber (28) that forms a trap for liquid fuel. Liquid fuel is purged from the canister (l0) through a purge tube (26) that has a small liquid-purge hole (32) at the bottom of the chamber (28) and a large vapour-purge hole (34) spaced above the bottom of the chamber (28).

Description: This invention relates to control of fuel vapour released from a fuel tank. During day-to-day operation of an automotive vehicle, the temperature of the vehicle fuel tank rises and falls. As the fuel tank temperature rises, some of the fuel vapour in the space above the liquid level is displaced out of the tank. To avoid releasing the fuel vapour to the atmosphere, an existing system vents the vapour to a canister having a bed that adsorbs and stores the fuel vapour. This invention provides a canister having an inlet chamber that forms a trap for liquid fuel and that has a purge tube with a small liquid-purge hole at the bottom of the chamber and a large vapour-purge hole spaced above the bottom of the chamber. This canister protects its vapour storage bed against absorption of liquid fuel and thereby preserves the bed for adsorption of fuel vapour. The details as well as other features and advantages of several embodiments of this invention are set forth in the remainder of the specification and are shown in the accompanying drawings, in which: Figure l is a schematic view of a fuel vapour storage canister employing this invention; Figure 2 is a schematic view of a second fuel vapour storage canister employing this invention; Figure 3 is a plan view of a third fuel vapour storage canister employing this invention; Figure 4 is a sectional, elevational view of the third canister, taken along line 4-4 of Figure 3; Figure 5 is an enlarged, fragmentary, sectional view of an air vent for the third canister, taken along line 5-5 of Figure 3; Figure 6 is an enlarged elevational view of the lower portion of a fuel vapour inlet tube employed in the third canister; Figure 7 is an enlarged, sectional, elevational view of lower portions of fuel vapour inlet and purge tubes removed from the third canister; Figure 8 is an enlarged, transverse, sectional view of the fuel vapour inlet and purge tubes of Figure 7, taken along the line 8-8 of Figure 7; Figure 9 is an enlarged, elevational view of the lower portion of the purge tube of Figure 7; Figure l0 is an enlarged, bottom view of the purge tube of Figure 7; Figure ll is an enlarged, transverse, sectional view of the purge tube of Figure 7, taken along line ll-ll of Figure 7; Figure l2 is a sectional, elevational view of a bottom portion of a modification of the third canister; Figure l3 is an end elevational view of another fuel vapour storage canister employing this invention; Figure l4 is an enlarged, sectional view of the Figure l3 canister, taken along line l4-l4 of Figure l3. Referring first to Figure l, a fuel vapour storage canister l0 has a bed l2 of activated carbon adapted to adsorb fuel vapour. Bed l2 is supported between upper and lower foam screens l4 and l6 within a housing l8 closed by a top 20 and a bottom 22. A fuel vapour inlet tube 24 and a purge tube 26 are supported by top 20, extend through bed l2, and open to an inlet chamber 28 below bed l2. The upper region of canister l0 is open to the atmosphere through an air vent 30. Inlet tube 24 receives a mixture of fuel vapour and air discharged from a fuel tank (not shown). As the mixture passes into chamber 28 and rises through bed l2, the activated carbon in bed l2 adsorbs the fuel vapour and the air flows out through canister vent 30. Chamber 28 serves as a trap to capture any liquid fuel that may be present in the mixture of fuel vapour and air received through inlet tube 24. By capturing the liquid fuel before it reaches bed l2, bed l2 is protected against absorption of liquid fuel, and the activated carbon is thereby preserved for adsorption of fuel vapour. Fuel is purged from canister l0 by applying vacuum to purge tube 26. Purge tube 26 has a small liquid-purge hole 32 at the lower end and a large vapour-purge hole 34 near the top of chamber 28. The vacuum applied through vapour-purge hole 34 draws air in through canister vent 30, down through bed l2, and into chamber 28. The air flow through bed l2 desorbs the fuel vapour, and the resulting mixture of air and fuel vapour is drawn out through purge tube 26. The vacuum applied through liquid-purge hole 32 gradually purges the liquid fuel from chamber 28, and the liquid fuel is drawn out through purge tube 26 along with the mixture of air and fuel vapour. Referring next to Figure 2, a fuel vapour storage canister ll0 has a bed ll2 of activated carbon adapted to adsorb fuel vapour. Bed ll2 is supported between upper and lower foam screens ll4 and ll6 within a housing ll8 closed by a top l20 and a bottom l22. A fuel vapour inlet tube l24 and a purge tube l26 are supported by top l20, extend through bed ll2, and open to an inlet chamber l28 below bed ll2. The upper region of canister ll0 is open to the atmosphere through an air vent l30. Inlet tube l24 receives a mixture of fuel vapour and air vented from a fuel tank (not shown). As the mixture passes into chamber l28 and rises through bed ll2, the activated carbon in bed ll2 adsorbs the fuel vapour and the air flows out through canister vent l30. Chamber l28 serves as a trap to capture any liquid fuel that may be present in the mixture of fuel vapour and air received through inlet tube l24. By capturing the liquid fuel before it reaches bed ll2, bed ll2 is protected against absorption of liquid fuel, and the activated carbon is preserved for adsorption of fuel vapour. Fuel is purged from canister ll0 by opening a solenoid-operated valve l3l to apply vacuum to purge tube l26. Purge tube l26 has a small liquid-purge hole l32 at the lower end and a large vapour-purge hole l34 near the top of chamber l28. The vacuum applied through vapour-purge hole l34 draws air in through canister vent l30, down through bed ll2, and into chamber l28. The air flow through bed ll2 desorbs the fuel vapour, and the resulting mixture of air and fuel vapour is drawn out through purge tube l26. The vacuum applied through liquid-purge hole l32 gradually purges the liquid fuel from chamber l28, and the liquid fuel is drawn out through purge tube l26 along with the mixture of air and fuel vapour. Referring now to Figures 3-ll, a fuel vapour storage canister 2l0 has a bed 2l2 of activated carbon adapted to adsorb fuel vapour. Bed 2l2 is supported between upper and lower foam screens 2l4 and 2l6 within a housing 2l8 closed by a top 220 and a bottom 222. A fuel vapour inlet tube 224 and a purge tube 226 are supported by top 220, extend through bed 2l2, and open to an inlet chamber 228 below bed 2l2. The upper region of canister 2l0 is open to the atmosphere through an air vent 230. Inlet tube 224 extends from an inlet fitting 233 that receives a mixture of fuel vapour and air discharged from a fuel tank (not shown). Four windows 235 open from inlet tube 224 to chamber 228; each window is covered by a screen 237 formed of monofilament mesh. As the mixture passes through inlet tube 224 and windows 235 into chamber 228 and rises through bed 2l2, the activated carbon in bed 2l2 adsorbs the fuel vapour and the air flows out through canister vent 230. Chamber 228 serves as a trap to capture any liquid fuel that may be present in the mixture of fuel vapour and air received through inlet tube 224. By capturing the liquid fuel before it reaches bed 2l2, bed 2l2 is protected against absorption of liquid fuel, and the activated carbon is thereby preserved for adsorption of fuel vapour. Purge tube 226 extends from a purge fitting 238 and is disposed within inlet tube 224. Purge tube 226 includes a tip 239 having a flange 24l that engages ribs 243 formed on inlet tube 224 between windows 235; the engagement of flange 24l with ribs 243 provides lateral support for purge tube tip 239. Fuel is purged from canister 2l0 by applying vacuum to purge fitting 238 and purge tube 226. Purge tube tip 239 has a small liquid-purge hole 245 about 0.44mm in diameter at the lower end and a large vapour-purge hole 247 about 2.79mm in diameter near the top of chamber 228. The vacuum applied through vapour-purge hole 247 draws air through canister vent 230, down through bed 2l2, and into chamber 228. The air flow through bed 2l2 desorbs the fuel vapour, and the resulting mixture of air and fuel vapour is drawn out through purge tube 226. The vacuum applied through liquid-purge hole 245 gradually purges the liquid fuel from chamber 228, and the liquid fuel is drawn out through purge tube 226 along with the mixture of air and fuel vapour. The engagement of flange 24l with ribs 243 and screen 237 inhibits liquid fuel adjacent the bottom of purge tube 226 from being drawn within inlet tube 224 to vapour purge hole 247. The lower end of inlet tube 224 is supported laterally by a plurality of ribs 249 formed on bottom 222 and extending into chamber 228. Ribs 249 also provide support for lower screen 2l6. The upper end of housing 2l8 has a grid 25l spacing upper screen 2l4 from cover 220 and providing an air chamber between vent 230 and grid 25l. Referring now to Figure l2, a fuel vapour storage canister 2l0′ is similar in most respects to canister 2l0 and includes a bed 2l2 of activated carbon adapted to adsorb fuel vapour. Bed 2l2 is supported upon a lower foam screen 2l6′ within a housing 2l8′ closed by a bottom 222′. Fuel vapour inlet tube 224 and purge tube 226 extend through bed 2l2 and open to inlet chamber 228 below bed 2l2. Inlet tube 224 receives a mixture of fuel vapour and air and has four windows 235 opening from inlet tube 224 to chamber 228; each window is covered by a screen 237 formed of monofilament mesh. As the mixture passes through inlet tube 224 and windows 235 into chamber 228 and rises through bed 2l2, the activated carbon in bed 2l2 adsorbs the fuel vapour. Chamber 228 serves as a trap to capture any liquid fuel that may be present in the mixture of fuel vapour and air received through inlet tube 224. By capturing the liquid fuel before it reaches bed 2l2, bed 2l2 is protected against absorption of liquid fuel, and the activated carbon is preserved for adsorption of fuel vapour. Purge tube 226 is disposed within inlet tube 224. Purge tube 226 includes a tip 239 having a flange 24l that engages ribs 243 formed on inlet tube 224 between windows 235. Fuel is purged from canister 2l0′ by applying vacuum to purge tube 226. Purge tube tip 239 has a small liquid-purge hole 245′ about 0.5mm in diameter at the lower end and a large vapour-purge hole 247 about 2.79mm in diameter near the top of chamber 228. The vacuum applied through vapour-purge hole 247 draws air down through bed 2l2 and into chamber 228. The air flow through bed 2l2 desorbs the fuel vapour, and the resulting mixture of air and fuel vapour is drawn out through purge tube 226. The vacuum applied through liquid-purge hole 245′ gradually purges the liquid fuel from chamber 228, and the liquid fuel is drawn out through purge tube 226 along with the mixture of air and fuel vapour. The lower end of inlet tube 224 is supported laterally by an intermediate grid 248 disposed above ribs 249 formed on bottom 222. Grid 248 also provides support for lower screen 2l6. Referring to Figures l3-l4, a fuel vapour storage canister 3l0 with a horizontal axis has a bed 3l2 of activated carbon adapted to adsorb fuel vapour. Bed 3l2 is supported between foam screens 3l4 and 3l6 within a housing 3l8. At the left end of canister 3l0, as viewed in Figure l4, housing 3l8 is closed by a partition 3l9 and a cover 320. A fuel vapour inlet tube 324 and a purge tube 326 are formed as part of cover 320 and open into an inlet chamber 328 between cover 320 and partition 3l9. Chamber 328 opens to bed 3l2 through an aperture 329 in partition 3l9, aperture 329 being spaced substantially above the bottom of chamber 328. The region 330 at the right end of canister 3l0 is open to the atmosphere through the vent tube 33l of a cover 33la. Inlet tube 324 receives a mixture of fuel vapour and air discharged from a fuel tank (not shown). As the mixture flows through chamber 328, aperture 329 and bed 3l2, the activated carbon in bed 3l2 adsorbs the fuel vapour and the air flows out through the region 330 and vent tube 33l. Chamber 328 serves as a trap to capture any liquid fuel that may be present in the mixture of fuel vapour and air received through inlet tube 324. By capturing the liquid fuel before it reaches bed 3l2, bed 3l2 is protected against absorption of liquid fuel, and the activated carbon is preserved for adsorption of fuel vapour. Fuel is purged from canister 3l0 by applying vacuum to purge tube 326. Purge tube 326 has a small liquid-purge hole 332 about 0.020in (0.5mm) in diameter at the lower end and a large vapour purge-hole 334 about 0.ll0in (2.79mm) in diameter near the top. The vacuum applied through vapour-purge hole 334 draws air in through the vent tube 33l and region 330, through bed 3l2, and into chamber 328. The air flow through bed 3l2 desorbs the fuel vapour, and the resulting mixture of air and fuel vapour is drawn out through purge tube 326. The vacuum applied through liquid-purge hole 332 gradually purges the liquid fuel from chamber 328, and the liquid fuel is drawn out through purge tube 326 along with the mixture of air and fuel vapour. The embodiment of the invention disclosed in Figures l3 and l4 of the accompanying drawings is also disclosed and claimed in our co-pending European patent application No. , filed on the same date.

Claims: 1. A fuel vapour storage canister (l0; ll0; 2l0; 2l0′) comprising a housing (l8; ll8; 2l8; 2l8′) having an inlet chamber (28; l28; 228), a region (30; l30; 230) vented to the atmosphere, and a bed (l2; ll2; 2l2) of material adapted to adsorb fuel vapour disposed between said chamber (28; l28; 228) and said region (30; l30; 230), a fuel vapour inlet tube (24; l24; 224) opening to said chamber (28; l28; 228) whereby fuel vapour can be introduced into said canister (l0; ll0; 2l0; 2l0′) and can flow from said chamber (28; l28; 228) into said bed (l2; ll2; 2l2) for adsorption thereby, and a purge tube (26; l26; 226) opening to said chamber (28; l28; 228) whereby vacuum applied to said purge tube (26; l26; 226) can cause air to flow from said region (30; l30; 230) through said bed (l2; ll2; 2l2) to said chamber (28; l28; 228) to desorb fuel vapour from said bed (28; l28; 228), characterised in that said purge tube (26; l26; 226) has a liquid-purge hole (32; l32; 245; 245′) disposed near the bottom of said chamber (28; l28; 228) and a vapour-purge hole (34; l34; 247) spaced substantially above the bottom of said chamber (28; l2l8; 228), whereby said chamber (28; l28; 228) serves as a trap for liquid fuel introduced through said inlet tube (24; l24; 2l4), and whereby said liquid fuel may be purged from said chamber (28; l28; 228) along with said air flow and the desorbed fuel vapour. 2. A fuel vapour storage canister (2l0; 2l0′) according to claim l, characterised in that said inlet chamber (228), bed (2l2), and region (230) are aligned with one another along a vertical axis with said inlet chamber (228) at the bottom; and said purge tube (226) is disposed concentrically within said inlet tube (224).

Inventors: COVERT, CHARLES HENRY, GIFFORD, WILLIAM ELIHU, KEMLER, CRAIG GLENN, PADDOCK, GORDON RICHARD
Applicants: GENERAL MOTORS CORPORATION
Application year: 1987
Main classification: F02M25
IPC codes: F02M25