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 
     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 
     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 
     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 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 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 in fluid communication with the outside air, and a second end is connected to the interior chamber of the regulator device, wherein the second flexible duct has a first end connected to the outlet port of the regulator device, and a second end in fluid communication with the inlet end of the air passageway. 
     DEFINITIONS 
     “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. 
     “Asymmetric tread” means a tread that has a tread pattern not symmetrical about the center plane or equatorial plane EP of the tire. 
     “Axial” and “axially” means lines or directions that are parallel to the axis of rotation of the tire. 
     “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. 
     “Circumferential” means lines or directions extending along the perimeter of a surface, perpendicular to the axial direction. 
     “Equatorial Centerplane (CP)” means the plane perpendicular to the tire&#39;s axis of rotation and passing through the center of the tread. 
     “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. 
     “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. 
     “Lateral” means an axial direction. 
     “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. 
     “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. 
     “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. 
     “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. 
     “Peristaltic” means operating by means of wave-like contractions that propel contained matter, such as air, along tubular pathways. 
     “Radial” and “radially” means directions radially toward or away from the axis of rotation of the tire. 
     “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. 
     “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. 
     “Tread element” or “traction element” means a rib or a block element defined by having shape adjacent grooves. 
     “Tread Arc Width” means the arc length of the tread as measured between the lateral edges of the tread. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described by way of example and with reference to the accompanying drawings in which: 
         FIG. 1  is an isometric view of tire and rim assembly showing a pump assembly. 
         FIG. 2  is a front view of the pump assembly as shown from inside the tire of  FIG. 1 . 
         FIG. 3  is a perspective view of a flow bridge assembly; 
         FIG. 4  is a cross-sectional view of the flow bridge assembly of  FIG. 4 ; 
         FIG. 5  is a perspective view of a pressure regulator assembly; 
         FIG. 6  is a cross-sectional view of the pressure regulator assembly of  FIG. 5  shown in the open position; 
         FIG. 7  is a cross-sectional view of the pressure regulator assembly of  FIG. 5  shown in the closed position; 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1 and 2 , a tire assembly  10  includes a tire  12 , a pump assembly  14 , and a wheel  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   
     As shown in  FIG. 2 , 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. 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. 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. 
     As shown in  FIG. 2 , the pump passageway  43  is connected to a flow bridge  100 , which is described in more detail, below. The inlet end  42  of the passageway  43  is connected to a first flow tee  110  of the flow bridge  100 , and an outlet end  44  of the pump passageway is connected to an outlet valve  200 . The outlet valve  200  is in fluid communication with the tire cavity  40 , and prevents back flow of cavity air into the pump system  14 . The outlet valve  200  may be any conventional check valve known to those skilled in the art. 
     Flow Bridge  100   
     The flow bridge  100  ports fluid from one location to another. As shown in  FIG. 2 , the flow bridge can port fluid from the outside air to the inlet of the pump passageway  42 . The flow bridge may also be used to port fluid from the exit of the pump to the check valve. The use of the flow bridge is not limited to the above examples, and may be used to port fluid from one location to another. The flow bridge  100  is formed of a flexible material, and has a first end  102  and a second end  104 . The flow bridge  100  is secured to the tire by first and second flow tees which are inserted through the first and second ends  102 , 104 . An internal passageway  106  extends from the first end  102  to the second end  106 . The first end  102  and the second end  106  each terminate in a flanged annular collar  107 , 109 . A first flow tee  108  and a second flow tee  110  is received through the hole of the respective annular collar  107 , 109 . The first flow tee  108  and the second flow tee  110  each have a respective enlarged head  111 , 113 . The first flow tee  108  and the second flow tee  110  each have a respective cylindrical body  115 , 117  having a respective outer threaded surface  116 , 118 . The first flow tee  108  and the second flow tee  100  may be screwed into a threaded internal bore of a cylindrical sleeve (not shown). Each sleeve is permanently inserted into the tire, preferably in the tire sidewall. Each flow tee  108 , 110  has a central duct  120 , 122 . The duct  120  of the first flow tee  108  has a first end  121  in fluid communication with the outside air (not shown). The duct  120  has opposed outlet holes  123  in fluid communication with the inlet of the internal passageway  106  of the flow bridge  100 . Surrounding the outlet holes  123  is a recessed ring  125 . The duct  122  of the second flow tee  110  has a first end  130  connected to the inlet  42  of the pump passageway  43 . The duct  122  of the second flow tee  110  has a second end having opposed inlet holes  132 . Surrounding the opposed inlet holes  132  is a recessed ring  134 . Each recessed ring  125 , 134  facilitates flow from/to the opposed holes  123 , 132  to/from the internal passageway  106  of the flow bridge. 
     Regulator Device 
     The flow bridge  100  may further include a valve mechanism to regulate the flow to the pump. The flow bridge  100  shown in  FIG. 2  may be replaced with the regulator device  300  shown in  FIGS. 3-5 . The regulator device  300  functions to regulate the flow of air to the pump  14 . 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 . 
     The pressure membrane has an upper surface  551  that has an inner depression  549 . 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. 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 leaf spring  580  is positioned in the interior chamber  320  to bias the pressure membrane  550  in the open position. The spring has an inner surface  582  wherein a plurality of extensions  584  extend radially inward. The spring has an outer annular rim  585  that is received in an annular recess  321 . The leaf spring has an inner hole  587  for receiving the pressure membrane plug  555 . 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 . 
     Extending from the central regulator housing  310  is a first and second flexible duct  400 ,  500 , positioned on either side of the central regulator housing  310 . Each flexible duct  400 ,  500  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  400 ,  500  has an internal passageway  404 ,  504  for communicating fluid. 
     The internal passageway  404  of the first flexible duct  400  has a first opening  402  that opens to the 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 the internal duct  120  of the first flow tee  108 . Outside air is communicated through the internal duct  120  of the first flow tee  108  to the inlet  406  of the internal passageway  404  of the first flexible duct  400 . 
     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 the internal duct  122  of the T fitting  110 . Flow from the internal duct  122  is communicated to the inlet  42  of the pump passageway  43 . 
     System Operation 
     As will be appreciated from  FIG. 2 , the regulator device  300  is in fluid communication with the inlet end of the pump passageway  43 . As the tire rotates, a footprint is formed against the ground surface. A compressive force 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 check valve  200 . The pumped air exits the pump outlet check valve into the tire cavity  40 . 
     The regulator device  300  controls the flow of outside air into the pump. If the tire pressure is low, the membrane  550  in the regulator device  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 first tee fitting  108  and then into the internal passageway of the first flexible duct  400 , as shown in  FIG. 6 . The flow then exits the first flexible duct and enters the regulator chamber and then into the second flexible duct, through the T fitting  110  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. 
     If the tire pressure is sufficient, the regulator device will block flow from exiting the pressure regulator, as shown in  FIG. 7 . 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 regulator device. The pressure membrane material properties are adjusted to have the desired tire pressure settings. 
     The location of the pump assembly in the tire will be understood from  FIG. 1 . In one embodiment, the pump assembly  14  is positioned in the tire sidewall, radially outward of the rim flange surface, typically in the chafer. The positioning of the pump assembly may be located at any region of the tire that undergoes cyclical compression. 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. The cross-sectional shape of the air passageway  43  may be elliptical or round. 
     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. As the length of the pump increases, the pump passageway will need to substantially open and close like a peristaltic pump. 
     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. 
     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.