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 regulator device. The regulator device 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 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; a first and second air passageway each having an inlet end and an outlet end, each air passageway being composed of a flexible material operative to open and close when the tire rotates, wherein each air passageway outlet end is in fluid communication with the tire cavity; a regulator device having a regulator body having an interior chamber; a pressure membrane being mounted on the regulator device 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 regulator device has a first, second and third flexible duct, wherein said first, second and third flexible ducts each have an internal passageway; wherein the third flexible duct has a first end in fluid communication with the outside air, and a second end in fluid communication with the interior chamber of the regulator device, wherein the first flexible duct has a first end in fluid communication with the inlet end of the first air passageway, and a second end in fluid communication with the outlet port of the regulator device; wherein the second flexible duct has a first end in fluid communication with the inlet end of the second air passageway, and a second end in fluid communication with the outlet port of the regulator device. 
       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. 2A  is a schematic of a double pump and regulator assembly. 
           [0026]      FIG. 2B  is a front view of the tire of  FIG. 1  showing the system in operation. 
           [0027]      FIG. 3  is a front view of the regulator assembly as shown from inside the tire of  FIG. 1 . 
           [0028]      FIG. 4  is an exploded view of the regulator assembly. 
           [0029]      FIG. 5  is a top view of the regulator assembly of  FIG. 4 . 
           [0030]      FIG. 6A  is a section view of  FIG. 5  in the direction  6 A- 6 A showing the regulator in the closed position during operation. 
           [0031]      FIG. 6B  is a section view of  FIG. 5  in the direction  6 A- 6 A showing the regulator in the open position during operation. 
           [0032]      FIG. 7A  is a section view of  FIG. 5  in the direction  7 A- 7 A showing the regulator in the open position during operation when the tire is rotating in a first direction. 
           [0033]      FIG. 7B  is a section view of  FIG. 5  in the direction  7 A- 7 A showing the regulator in the open position during operation when the tire is rotating in a first direction, and flow exiting the outlet valve from the pump air passageway. 
           [0034]      FIG. 8A  is a section view of  FIG. 5  in the direction  7 A- 7 A showing the regulator in the open position during operation when the tire is rotating in a second direction opposite the first direction. 
           [0035]      FIG. 8B  is a section view of  FIG. 5  in the direction  7 A- 7 A showing the regulator in the open position during operation when the tire is rotating in a second direction opposite the first direction, and flow exiting the outlet valve of the pump air passageway. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0036]    Referring to  FIGS. 1 and 2 , a tire assembly  10  includes a tire  12 , pump assemblies  14 , and a tire rim  16 . The tire and rim enclose a tire cavity  40 . As shown in  FIGS. 1 and 3 , the pump assembly  14  is preferably mounted into the sidewall area  15  of the tire, preferably near the bead region. 
       Pump Assembly  14   
       [0037]    The first and second pump assembly  14  includes a first and second air passageway  43 ,  44  which may be molded into the sidewall of the tire during vulcanization or formed post cure. Each passageway  43 ,  44  acts as a pump. When the first and second air passageway  43 ,  44  are molded into the tire sidewall as shown in  FIG. 2B , and each the air passageway  43 ,  44  has an arc length L as measured by a respective angle Ψ 1 , Ψ 2  that is measured from the center of rotation of the tire. In a first embodiment, the angle Ψ 1 , Ψ 2  may range, and is preferably in the range of at least 150 degrees, and more preferably in the range of about 150-190 degrees, and about 160 degrees as shown. The pump air passageway  43 ,  44  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. 
         [0038]    As shown in  FIG. 2A , an inlet filter assembly  600  is connected to a regulator assembly  300  for providing inlet filtered air to the regulator assembly  300 . The regulator assembly is connected to the inlet end  42  of the first pump passageway  43  via an inlet banjo fitting  100 . The first pump passageway has an outlet end  46  that is connected to an outlet check valve  400 . The regulator assembly is connected to the inlet end  48  of a second pump passageway  44  via a banjo fitting  200 . The second pump passageway  44  has an outlet end  52  connected to an outlet check valve  500 . 
       Regulator Device 
       [0039]    A regulator device  300  is shown in  FIGS. 3-8 . The regulator device  300  functions to regulate the flow of air to the air passageways  43 ,  44 . The regulator device  300  has a central regulator 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 . 
         [0040]    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 regulator 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. A rigid lid  700  is received over the pressure membrane. The lid  700  has a plurality of holes  703  on an upper surface  702  to allow the outer surface  551  of the pressure membrane to be in fluid communication with the pressure of the tire chamber  40 . The outer surface  551  of the pressure membrane is in fluid communication with the pressure of the tire chamber  40  and in contact with the rigid lid  600 . 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  as shown in  FIG. 6A . 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 . An optional first washer  586  may be received between the spring first end  582  and the pressure membrane  550 . An optional second washer  588  may be received between the spring second end  584  and the bottom of the chamber  313 . The lid  700  is made of a rigid material, and resists the spring force, thus functioning to preload the spring via the pressure membrane  550 . 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 . 
         [0041]    Extending from the central regulator housing  310  is a first, second and third flexible duct  350 ,  360 ,  370  positioned on either side of the central regulator housing  310 . Each flexible duct  350 ,  360 ,  370  may be integrally formed with the regulator housing as shown, or be a discrete part connected to the central regulator housing  310 . Each flexible duct  350 ,  360 ,  370  has an internal passageway  352 ,  362 ,  372  for communicating fluid. 
         [0042]    As shown in  FIG. 7A , the internal passageway  352  of the first flexible duct  350  has a first end  354  that is connected to the outlet port  330 . The first flexible duct  350  has a circular flanged distal end  360  having a hole  362  for receiving the body of the inlet banjo fitting  100 . The internal passageway  352  has an outlet hole  356  that is in fluid communication with inlet holes  104  of an inlet banjo fitting  100 . A circumferential groove  105  surrounds the inlet holes  104  to channel the fluid from the internal passageway  352  to an internal passageway  102 . The internal channel  102  is connected to the inlet  48  of the pump passageway  44 . The banjo fitting  100  may be replaced with an internally relieved bolt or a hollow screw with an internal passageway. The banjo fitting  100  has an outer threaded surface  106  that is received in the tire sidewall. 
         [0043]    As shown in  FIG. 7A , the internal passageway  362  of the second flexible duct  360  is shown connected to the outlet port  330  of the interior chamber  320  and the internal passageway  352  of the first flexible duct  350 . The internal passageway  362  has an outlet  364  in fluid communication with a banjo fitting  200 . The second flexible duct has a distal end formed in a circular flange  368 . The circular flange has a hole  369  for receiving the body of banjo fitting  200 . The banjo fitting  200  has an internal passageway  202  with inlet holes  204  that receive flow from the outlet hole  364  of the internal passageway  362  of the second flexible duct  360 . The internal passageway  202  communicates flow to the inlet end  42  of the first pump passageway  43 . The banjo fitting  200  may comprise a screw with an internal passageway, and has an outer threaded surface  206  that is received in the tire sidewall. 
         [0044]    As shown in  FIGS. 5 and 6A , the internal passageway  372  of the third flexible duct  370  has a first opening  374  that is connected to the outlet port  642  of the inlet filter assembly  600 . The internal passageway  372  of the first flexible duct  370  has a second end  376  that opens to the inlet chamber  320  of the regulator  300 . The third flexible duct has a circular flanged distal end  378  that has an interior hole  379  for receiving the inlet filter assembly  600 . 
       Inlet Filter Assembly 
       [0045]    The inlet filter assembly  600  is shown in  FIGS. 6A ,  6 B. The inlet filter assembly  600  includes an insert sleeve  612  that is hollow and has an internal threaded bore  614 . The first end of the insert sleeve  612  is inserted into the tire, typically in the outer surface of the sidewall  15 . The insert sleeve  612  may be inserted into the tire post cure or may be molded into the tire. An air passage screw  620  has an outer threaded body  622  that is screwed into the second end  624  of the insert sleeve. The air passage screw  620  may be a banjo screw or an internally relieved bolt. The air passage screw  620  has an internal passageway  630  in fluid communication with the bore  614  of the insert sleeve  612 . A filter  640  is received within the bore  614  of the insert sleeve  612 , and may also be located in the internal passageway  630 . The internal passageway  630  has outlet ports  642  that communicates filtered air from the internal passageway  630  to the inlet  374  of the internal passageway  372  of the third flexible duct  370 . The internal passageway  372  communicates filtered air to the inlet chamber  320 . 
       Pump Outlet Check Valve 
       [0046]    The outlet end  46  of the pump passageway  43  is connected to a pump outlet valve  400 . The pump outlet valve is shown in  FIGS. 7A-B . The pump outlet valve  400  includes a valve body  410  having an outer threaded surface  412  that is mounted within the sidewall of the tire. The valve body  410  has a central passage  415  that has a first opening  418  that is in fluid communication with the first pump passageway  43  outlet end  46 . The central passage  415  has an outlet end  417  that communicates flow to the tire cavity  40 . The outlet end  417  is covered by a flexible sleeve  419 . The flexible member  419  opens to allow airflow to exit the pump and into the tire cavity  40  as shown in  FIG. 7   b . The flexible member is shown closed in  FIG. 7A , and prevents flow of air from the tire cavity into the pump passageway  43 . 
         [0047]    The outlet end  52  of second pump passageway  44  is also connected to a pump outlet valve  500 , as shown in  FIGS. 8A ,  8 B. The pump outlet valve  500  includes a valve body  510  having an outer threaded surface  512  that is received within the sidewall of the tire. The valve body  510  has a central passage  515  that has a first opening  518  that is in fluid communication with the pump passageway  44  outlet end  52 . The central passage  515  has an outlet end  517  that is covered by a flexible member  519 . The flexible sleeve  519  opens to allow airflow to exit the pump and into the tire cavity  40  as shown in  FIG. 8   b . The flexible member is shown closed in  FIG. 8A , and prevents back flow of air from the tire cavity into the pump passageway  44 . 
       System Operation 
       [0048]      FIGS. 1-2  illustrate the first and second pump assemblies  43 ,  44 . The system is bidirectional, so that only one pump assembly will pump for a given tire direction. Thus if the tire rotates clockwise as viewed from  FIG. 2B , pump air passageway  44  will pump air into the tire. When the tire rotates counterclockwise, pump air passageway  43  will pump air into the tire. As shown in  FIGS. 2A and 2B , the regulator device  300  is in fluid communication with each inlet end  42 ,  48  of each pump passageway  43 ,  44 . 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 ,  44 . Flattening of the pump passageway  43 ,  44  forces the compressed air towards the respective pump outlet device  400 ,  500 . Due to the increase in pressure at the pump outlet  46 ,  52 , the pressure opens the sleeve  419 ,  519  from the opening  417 ,  517  of the pump outlet valve, which allows the pumped air to exit into the tire cavity  40 . 
         [0049]    The regulator device  300  controls the inflow of outside air into the pump. If the tire pressure is above the preset threshold value, the plug  555  of the pressure membrane seals the central outlet port  330  and no air enters the pump passageway, as shown in  FIG. 6A . The pressure preset threshold value can be predetermined based upon the tire size, and the material properties of the pressure membrane, spring preloading, and spring constant can be selected to determine the pressure at the preset threshold value. If the tire pressure falls below the preset threshold value, the plug  555  of the membrane  550  will unseat from the central outlet port  330 , opening the outlet port  330  as shown in  FIG. 6B . As the chamber pressure  320  falls due to the opening of the central outlet port  330 , outside air will be sucked through the filter assembly  600  to the interior chamber  320 . If the tire rotates in a clockwise direction as shown in  FIGS. 8A and 8B , the filtered air exits the interior chamber through the outlet port  330 , and enters the first flexible duct  360 . Then the filtered air passes through the banjo fitting  100  into the pump inlet  48 , as shown in  FIG. 8A . The flow is then compressed through the pump passageway  44  and then exits the pump outlet valve  400  into the tire cavity  40  as shown in  FIG. 8B . The pump will pump air with each tire rotation. The pump passageway  44  fills with air when the pump system is not in the footprint. 
         [0050]    If the tire rotates in a counterclockwise direction as shown in  FIGS. 7A and 7B , the filtered air exits the interior chamber  320  through the outlet port  330 , and enters the second flexible duct  360  then through the banjo fitting  200  and then into the pump inlet  42 . The flow is then compressed through the pump passageway  43  and then exits the pump outlet valve  400  into the tire cavity  40 . 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. 
         [0051]    The location of the pump assembly in the tire will be understood from  FIGS. 1 ,  2 A and  3 . In one embodiment, the pump assembly  14  is positioned in the tire sidewall, radially outward of the rim flange surface. So positioned, the air passageway  43 ,  44  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 ,  44  is specifically shown in a region 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 ,  44  may be elliptical or round or any desired shape. 
         [0052]    The length as represented by the angle Ψ of each pump passageway is illustrated at about 160 degrees, the invention is not limited to same, and may be shorter or longer as desired. 
         [0053]    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. 
         [0054]    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.