Abstract:
A self-inflating tire assembly includes an air tube connected to a tire and defining an air passageway, the air tube being composed of a flexible material operative to allow an air tube segment opposite a tire footprint to flatten, closing the passageway, and resiliently unflatten into an original configuration. The air tube is sequentially flattened by the tire footprint in a direction opposite to a tire direction of rotation to pump air along the passageway to a inlet control valve. The inlet control valve regulates the inlet air flow to the air tube and the outlet air flow to the tire cavity.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates generally to self-inflating tires and, more specifically, to a pump mechanism and pressure regulator for such tires. 
       BACKGROUND OF THE INVENTION 
       [0002]    Normal air diffusion reduces tire pressure over time. The natural state of tires is under inflated. Accordingly, drivers must repeatedly act to maintain tire pressures or they will see reduced fuel economy, tire life and reduced vehicle braking and handling performance. Tire Pressure Monitoring Systems have been proposed to warn drivers when tire pressure is significantly low. Such systems, however, remain dependent upon the driver taking remedial action when warned to re-inflate a tire to recommended pressure. It is a desirable, therefore, to incorporate a self-inflating feature within a tire that will self-inflate the tire in order to compensate for any reduction in tire pressure over time without the need for driver intervention. 
       SUMMARY OF THE INVENTION 
       [0003]    The invention provides in a first aspect a self-inflating tire assembly, including a tire mounted to a rim, the tire having a tire cavity, first and second sidewalls extending respectively from first and second tire bead regions to a tire tread region; an air passageway having an inlet end and an outlet end, the air passageway being composed of a flexible material operative to open and close when the tire rotates, wherein the outlet end is in fluid communication with the tire cavity; the inlet control valve having a regulator body having an interior chamber; a pressure membrane being mounted on the inlet control valve to enclose the interior chamber, wherein the pressure membrane has a lower surface that is positioned to open and close the outlet port mounted in the interior chamber, wherein the pressure membrane is in fluid communication with the tire cavity pressure; wherein the body of the inlet control valve has a first and second flexible duct, wherein said first and second flexible ducts each have an internal passageway; wherein the first flexible duct has a first end connected to an inlet filter assembly and a second end is connected to the interior chamber of the inlet control valve, wherein the second flexible duct has a first end connected to the outlet port of the inlet control valve, and a second end in fluid communication with the inlet end of the air passageway. 
       Definitions 
       [0004]    “Aspect ratio” of the tire means the ratio of its section height (SH) to its section width (SW) multiplied by  100  percent for expression as a percentage. 
         [0005]    “Asymmetric tread” means a tread that has a tread pattern not symmetrical about the center plane or equatorial plane EP of the tire. 
         [0006]    “Axial” and “axially” means lines or directions that are parallel to the axis of rotation of the tire. 
         [0007]    “Chafer” is a narrow strip of material placed around the outside of a tire bead to protect the cord plies from wearing and cutting against the rim and distribute the flexing above the rim. 
         [0008]    “Circumferential” means lines or directions extending along the perimeter of a surface, perpendicular to the axial direction. 
         [0009]    “Equatorial Centerplane (CP)” means the plane perpendicular to the tire&#39;s axis of rotation and passing through the center of the tread. 
         [0010]    “Footprint” means the contact patch or area of contact of the tire tread with a flat surface at zero speed and under normal load and pressure. 
         [0011]    “Inboard side” means the side of the tire nearest the vehicle when the tire is mounted on a wheel and the wheel is mounted on the vehicle. 
         [0012]    “Lateral” means an axial direction. 
         [0013]    “Lateral edges” means a line tangent to the axially outermost tread contact patch or footprint as measured under normal load and tire inflation, the lines being parallel to the equatorial centerplane. 
         [0014]    “Net contact area” means the total area of ground contacting tread elements between the lateral edges around the entire circumference of the tread divided by the gross area of the entire tread between the lateral edges. 
         [0015]    “Non-directional tread” means a tread that has no preferred direction of forward travel and is not required to be positioned on a vehicle in a specific wheel position or positions to ensure that the tread pattern is aligned with the preferred direction of travel. Conversely, a directional tread pattern has a preferred direction of travel requiring specific wheel positioning. 
         [0016]    “Outboard side” means the side of the tire farthest away from the vehicle when the tire is mounted on a wheel and the wheel is mounted on the vehicle. 
         [0017]    “Peristaltic” means operating by means of wave-like contractions that propel contained matter, such as air, along tubular pathways. 
         [0018]    “Radial” and “radially” means directions radially toward or away from the axis of rotation of the tire. 
         [0019]    “Rib” means a circumferentially extending strip of rubber on the tread which is defined by at least one circumferential groove and either a second such groove or a lateral edge, the strip being laterally undivided by full-depth grooves. 
         [0020]    “Sipe” means small slots molded into the tread elements of the tire that subdivide the tread surface and improve traction, sipes are generally narrow in width and close in the tires footprint as opposed to grooves that remain open in the tire&#39;s footprint. 
         [0021]    “Tread element” or “traction element” means a rib or a block element defined by having shape adjacent grooves. 
         [0022]    “Tread Arc Width” means the arc length of the tread as measured between the lateral edges of the tread. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    The invention will be described by way of example and with reference to the accompanying drawings in which: 
           [0024]      FIG. 1  is an isometric view of tire and rim assembly showing a pump and regulator assembly. 
           [0025]      FIG. 2  is a front view of the pump and regulator assembly as shown from inside the tire of  FIG. 1 . 
           [0026]      FIG. 3  is an exploded view of the regulator assembly. 
           [0027]      FIG. 4  is a section view of  FIG. 2  in the direction  4 - 4  showing the regulator in the open position during operation. 
           [0028]      FIG. 5  is a section view of  FIG. 2  in the direction  4 - 4  showing the regulator in the closed position during operation. 
           [0029]      FIG. 6  is a front view of a second embodiment of a regulator assembly as shown from inside the tire of  FIG. 1 . 
           [0030]      FIG. 7  is an exploded view of the second embodiment of the regulator assembly. 
           [0031]      FIG. 8  is a section view of  FIG. 6  in the direction  8 - 8  showing the regulator in the open position during operation. 
           [0032]      FIG. 8   a  is the same as  FIG. 8 , except that the coil spring has been replaced with a leaf spring. 
           [0033]      FIG. 9  is a section view of  FIG. 6  in the direction  8 - 8  showing the regulator in the closed position during operation. 
           [0034]      FIG. 10  is a view from inside the tire during operation. 
           [0035]      FIG. 11  is an exploded view of a pump outlet valve. 
           [0036]      FIG. 12   a  is a cross-sectional view of the pump outlet valve in the closed position. 
           [0037]      FIG. 12   b  is a cross-sectional view of the pump outlet valve during the cracking open position. 
           [0038]      FIG. 12   c  is a cross-sectional view of the pump outlet valve in the open position. 
           [0039]      FIG. 13  is a cross-sectional view of the lower tire sidewall. 
           [0040]      FIG. 14  is a front view of the regulator and pump assembly illustrating a pump length of about 170 degrees. 
           [0041]      FIG. 15  is a front view of the regulator and pump assembly illustrating a pump length of about 350 degrees. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0042]    Referring to  FIGS. 1 and 2 , a tire assembly  10  includes a tire  12 , a pump assembly  14 , and a tire rim  16 . The tire and rim enclose a tire cavity  40 . As shown in  FIGS. 1-2 , the pump assembly  14  is preferably mounted into the sidewall area  15  of the tire, preferably near the bead region. 
       Pump Assembly  14   
       [0043]    The pump assembly  14  includes an air passageway  43  which may be molded into the sidewall of the tire during vulcanization or formed post cure. When the air passageway is molded into the tire sidewall as shown in  FIG. 2 , the air passageway has an arc length L as measured by an angle Ψ that is measured from the center of rotation of the tire. In a first embodiment, the angle Ψ may range, and is preferably in the range of about 15-50 degrees or optionally, an angular length sufficient to extend the length of the tire footprint Z, as shown in  FIG. 10 . The air passageway has an arc length L that may extend in a circumferential direction, or any direction. The arc length L may range, and is preferably about the length of the tire footprint Z, as shown in  FIG. 10 . The length is typically about 20-40 degrees when the shorter length is used. Alternatively, the pump tube length may be any desired length, typically 20 degrees or more. The pump air passageway  43  is comprised of a tube body formed of a resilient, flexible material such as plastic, elastomer or rubber compounds, and is capable of withstanding repeated deformation cycles when the tube is deformed into a flattened condition subject to external force and, upon removal of such force, returns to an original condition generally circular in cross-section. The tube is of a diameter sufficient to operatively pass a volume of air sufficient for the purposes described herein and allowing a positioning of the tube in an operable location within the tire assembly as will be described. Preferably, the tube has a circular cross-sectional shape, although other shapes such as elliptical may be utilized. The tube may be a discrete tube that is inserted into the tire during tire manufacturing, or the tube may be molded into shape by the presence of a removable strip that forms the passageway when removed. 
         [0044]    As shown in  FIG. 2 , the pump passageway  43  has an inlet end  42  connected to an inlet fitting  100 , and an outlet end  44  that is connected to an outlet valve  200 . The inlet fitting  100  is in fluid communication with an inlet control valve  300 . The inlet control valve  300  is in fluid communication with an inlet filter assembly  450 . 
       Inlet Control Valve 
       [0045]    A first embodiment of an inlet control valve  300  is shown in  FIGS. 2-5 . The inlet control valve  300  functions to regulate the flow of air to the pump  14 . The inlet control valve  300  has a central housing  310  that houses an interior chamber  320 . The interior chamber  320  has a central opening  312 . Opposite the central opening  312  is an outlet port  330 . The outlet port is raised from the bottom surface  313  and extends into the interior of the chamber  320 . The outlet port is positioned to engage a pressure membrane  550 . 
         [0046]    The pressure membrane has an upper surface  551  that is substantially planar. The pressure membrane has a lower surface  553  wherein a plug  555  extends from the lower surface. The pressure membrane further has an annular sidewall  556  which extends downwardly from the upper surface, forming a lip  557 . The lip  557  is preferably annular, and snaps in an annular cutout  559  formed on the outer housing  310 . The pressure membrane is a disk shaped member made of a flexible material such as, but not limited to, rubber, elastomer, plastic or silicone. The outer surface  551  of the pressure membrane is in fluid communication with the pressure of the tire chamber  40 . The lower surface  553  of the pressure membrane is in fluid communication with the interior chamber  320 . The plug  555  is positioned to close the outlet port  330 . A spring  580  is positioned in the interior chamber  320  to bias the pressure membrane  550  in the open position. The spring has a first end  582  that is received about the plug  555 . The spring has a second end  584  that is wrapped around the outer surface of the outlet port  330 . A first washer  586  may be received between the spring first end  582  and the pressure membrane  550 . A second washer  588  may be received between the spring second end  584  and the bottom of the chamber  313 . Thus the balance of pressure forces on each side of the pressure membrane actuates the pressure membrane plug  555  to open and close the outlet port  330 . A membrane support member  590  is received over the pressure membrane  550 . The membrane support member  590  has a plurality of holes  592  in the outer surface  591  of the lid, to allow the pressure membrane to be in fluid communication with the tire cavity  40 . The membrane support member  590  is formed of a rigid material, and the support member allows a preloading of the spring via the pressure membrane. 
         [0047]    Extending from the central housing  310  is a first and second flexible duct  400 ,  500 , positioned on either side of the central housing  310 . Each flexible duct  400 ,  500  may be integrally formed with the central housing as shown, or be a discrete part connected to the central housing  310 . Each flexible duct  400 ,  500  has an internal passageway  404 ,  504  for communicating fluid. 
         [0048]    The internal passageway  404  of the first flexible duct  400  has a first opening  402  that is located inside the interior chamber  320 . The internal passageway  404  of the first flexible duct  400  has a second end  406  that is in fluid communication with an inlet filter assembly  450 . The inlet device  450  supplies outside filtered air to the regulator via the first flexible duct  400 , and is described in more detail below. 
         [0049]    The internal passageway  504  of the second flexible duct  500  is shown integrally formed with the outlet port  330  of the interior chamber  320 . The internal passageway  504  has a second end  506  in fluid communication with an inlet fitting  100 . The inlet fitting  100  may be a hollow screw such as a banjo screw. The inlet fitting  100  has an internal passageway  102  with inlet holes  104  that communicate flow to the inlet  42  of the pump passageway  43 . The inlet fitting  100  may comprise a screw with an internal passageway, and has an outer threaded surface  106  that is received in a sleeve  110 . The sleeve  110  has a bore that extends completely therethrough. The sleeve is mounted in the tire. 
         [0050]    A second embodiment of the inlet control valve  1100  is shown in  FIGS. 6-9 . The inlet control valve  1100  is the same as  300  except for the following differences. The membrane  1102  does not have a plug  555  on the lower surface. The membrane has a non-planar upper surface with a recessed interior portion  1104 . The recessed interior portion extends into the interior of the interior chamber and is positioned to open and close the outlet passageway  330 . A coil spring  580  is positioned to bias the pressure membrane in the open position. The coil spring  580  may be replaced with a leaf spring  583  as shown in  FIG. 8A . 
       Inlet Filter Assembly 
       [0051]    The inlet filter assembly  450  is shown in  FIG. 4 . The inlet filter assembly  450  includes an insert sleeve  452  that is hollow and has an internal threaded bore  454 . The insert sleeve  452  is inserted into the tire, typically in the sidewall  15 . The insert sleeve  452  may be inserted into the tire post cure or may be molded into the tire as shown in  FIG. 2 . An air passage screw  460  has an outer threaded body  463  that is screwed into the internal threaded bore  454  of the insert sleeve. The air passage screw  460  has an internal passageway  462  having an opening  464 . A filter  470  is inserted through opening  464  and is received in the internal passageway  462 . A filter cap  480  has a threaded end  482  that is received in the opening  464  of the air passage screw  460 . The filter cap is positioned on the outside surface of the tire, typically on the tire sidewall as shown in  FIG. 1 . The filter cap has a plurality of holes  484  for allowing the flow of air into the inlet filter  470 . Outside air enters hole  484  and then through the filter cap into and through filter  470 . The filter air exits the filter  470  into the internal passageway  462  of the air passage screw  460 . The air exits the internal passageway  462  through exit hole  490  and then into the inlet end  406  of the first flexible duct  400 . The inlet end of the flexible duct  400  has a circular flange  495  surrounding a hole  410  through which the air passage screw is inserted. The exit hole  490  is located in a circumferential groove  491  to facilitate fluid communication with inlet hole  406  of the first flexible duct  400 . The circular flange  495  functions like a sealing gasket if it is made of a flexible soft material like rubber. 
       Pump Outlet Check Valve 
       [0052]    As described above, a first end  42  of the pump is connected to a regulator and a check valve. The second end  44  of the pump is connected to a pump outlet valve  200 . The pump outlet valve is shown in  FIGS. 11 ,  12 A-C. The pump outlet valve  200  includes an insert sleeve  202  that is inserted into the tire on an interior surface, typically the inner sidewall as shown in  FIG. 2 . The insert sleeve  202  has an internal threaded bore  204 . The insert sleeve  202  may be molded into the tire  12  or inserted post cure. The insert is installed in the tire area so that the internal bore  204  is in fluid communication with the pump outlet end  44 . A valve body  210  has an outer threaded surface  212  that is received within insert  202 . The valve body  210  has a central passage  215  that has a first opening  218  that is in fluid communication with the insert sleeve bore  204  and the pump passageway  43  outlet end  44  when inserted into the tire. The central passage  215  has an outlet end  217  that is in fluid communication with the tire cavity. The valve body has a shaped head  222  such as a hexagonal shaped head bore  223  for receiving a mating tool such as an allen wrench useful for tightening the valve body  210  inside the sleeve  202 . The central passage  215  further includes a retainer slot  230  for receiving flexible stopper  240 . The flexible stopper  240  is preferably made of a resilient material such as rubber, silicone, or an elastomer. The flexible stopper  240  has a disk shaped lower end  242 , and two opposed legs  244  which extend from the lower end  242 . Each leg  244  has a shoe  250  which has a curved enlarged shape and is made of a resilient material. As shown, the shoe is a semi-circle, although other shapes would work for the invention. Although the flexible stopper  240  is shown with two legs  244 , the stopper could have a single leg  244  with a shoe thereon, and the shoe could be annular with holes that allow passage of air therethrough. 
         [0053]    The flexible stopper is mounted inside the central passage so that each shoe  250  of the flexible stopper is received in the annular retainer slot  230 , and the disk lower end  242  is positioned to open and close the pump end  44 . 
         [0054]      FIGS. 12A-C  illustrate the pump outlet valve  200  installed and operational.  FIG. 12C  illustrates flow from the pump outlet  44  to the pump outlet valve  200 . The disk lower end  242  of the flexible stopper  240  does not seal the pump outlet  44  when the flow direction is towards the pump outlet valve  200 . The flow travels through the central passage  215 , around and through the legs  244  and exits the passage outlet  217  to the tire cavity.  FIG. 12A  illustrates the disk lower end  142  of the flexible stopper  140  sealing the pump end  44  so that flow is blocked from flowing to the tire cavity  40 .  FIG. 12B  illustrates the disk lower end  142  of the flexible stopper  140  being lifted by the valve cracking pressure when the pump starts pumping. 
         [0055]    An additional check valve like the check valve  200  may be optionally used between the pump inlet passageway  42  and the outlet of the regulator. 
       System Operation 
       [0056]    As will be appreciated from  FIG. 2 , the inlet control valve  300  is in fluid communication with the inlet end of the pump passageway  43 . As shown in  FIG. 10 , as the tire rotates, a footprint is formed against the ground surface. A compressive force F is directed into the tire from the footprint and acts to flatten the pump passageway  43 . Flattening of the pump passageway  43  forces the compressed air towards the pump outlet device  200 . Due to the increase in pressure at the pump outlet  44 , the pressure unseats the disk  242  from the opening of the pump outlet  44 , which allows the pumped air to exit the pump outlet device through passage  215  into the tire cavity  40 , as shown in  FIG. 12C . 
         [0057]    The inlet control valve  300  controls the flow of outside air into the pump. If the tire pressure is low, the membrane  550  in the inlet control valve  300  is responsive to the tire pressure in the tire cavity  40 . If the tire cavity pressure falls below a preset threshold value, the plug of the membrane will unseat from the central outlet port  330 . Outside air will enter the filter assembly  450 , exit through the filter and enter the first flexible duct  400 , as shown in  FIGS. 4 and 8 . The flow then exits the first flexible duct and enters the chamber and then into the second flexible duct, through the inlet fitting  100  and then into the pump inlet. The flow is then compressed through the pump and then exits the pump outlet valve into the tire cavity. The pump will pump air with each tire rotation. The pump passageway  43  fills with air when the pump system is not in the footprint. 
         [0058]    If the tire pressure is sufficient, the inlet control valve will block flow from exiting the inlet control valve, as shown in  FIGS. 5 and 9 . The pressure membrane is responsive to the cavity tire pressure and engages the central port  330  forming a seal which prevents air flow from passing through the inlet control valve. The pressure membrane material properties are adjusted to have the desired tire pressure settings. 
         [0059]    The location of the pump assembly in the tire will be understood from  FIGS. 1 and 13 . In one embodiment, the pump assembly  14  is positioned in the tire sidewall, radially outward of the rim flange surface in the chafer  600 . So positioned, the air passageway  43  is radially inward from the tire footprint and is thus positioned to be flattened by forces directed from the tire footprint as described above. Although the positioning of the air passageway  43  is specifically shown in a chafer  600  of the tire near the bead region, it is not limited to same, and may be located at any region of the tire that undergoes cyclical compression. The cross-sectional shape of the air passageway  43  may be elliptical or round. 
         [0060]    As described above, the length L of the pump passageway may be about the size of the tire&#39;s footprint length Z. However, the invention is not limited to same, and may be shorter or longer as desired. See  FIG. 14  which illustrates an approximate 170 degree length,  FIG. 15  which illustrates an approximate 340 degree length. As the length of the pump increases, the pump passageway will need to substantially open and close like a peristaltic pump. 
         [0061]    The pump assembly  14  may also be used with a secondary tire pressure monitoring system (TPMS) (not shown) of conventional configuration that serves as a system fault detector. The TPMS may be used to detect any fault in the self-inflation system of the tire assembly and alert the user of such a condition. 
         [0062]    Variations in the present invention are possible in light of the description of it provided herein. While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention. It is, therefore, to be understood that changes can be made in the particular embodiments described which will be within the full intended scope of the invention as defined by the following appended claims.