Abstract:
The present invention couples a tire pump with the wheel rim of a vehicle. The pump is activated electromagnetically to inflate the tire as desired, e.g. when tire pressure is below a required value. The pump is arranged to draw air from the atmosphere and pump into an interior portion of the tire. A magnetized plunger within the pump is biased to an initial position by a biasing element. Energizing an electromagnet generates a magnetic field. The pump is arranged to rotate in and out of the magnetic field to cause the plunger to reciprocate and inflate the tire.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to air-inflated tires of automotive vehicles. More specifically, the invention relates to an electromagnetically activated pump for inflating the tires on such vehicles.  
         BACKGROUND OF THE INVENTION  
         [0002]    Tire pressure is one of the most important elements of drivability and safety on automotive vehicles. Insufficient tire pressure may cause excessive or uneven tread wear, decreased fuel efficiency, and poor traction. Although there are several common causes of improper tire pressure, most tires will lose air pressure on a day-to-day basis with normal use. Tires may lose up to and beyond one pound per square inch (psi) of air pressure per month.  
           [0003]    It is proper practice, therefore, for an automotive vehicle operator to check and maintain tire pressure periodically to ensure adequate performance. Although it is recommended that a vehicle operator check tire pressure on a regular basis, adequate maintenance does not always occur. Furthermore, even when tire pressure is properly monitored, problems may surface. It is possible for a tire to acquire a slow leak, which an inexperienced or inattentive operator may not notice. Additionally, changes in ambient air temperature throughout the day can result in a significant change in tire pressure.  
           [0004]    It is therefore desirable to provide a means for self-inflating a tire to counteract normal tire pressure loss. Some current self-inflating tire pumps rely on the centrifugal force created by tire rotation to initiate the action of the pump. However, such an approach to self-inflation is not available at all vehicle speeds, as such pumps are designed to be activated only when the centrifugal force exceeds a specific value. Furthermore, current self-inflation systems do not actually pump the needed air into the tire until the vehicle speed is reduced. The centrifugal force must return below the value needed for pump activation in order to initiate inflation.  
           [0005]    Additionally, some pumps utilize tire pressure monitoring (TPM) systems. TPM systems communicate tire pressure status to the vehicle operator through intra-vehicular means such as a dashboard light or indicator. Vehicles equipped with a TPM system are often further equipped with a device such as an on-board compressor to correct air pressure deficiencies. When the TPM system detects a low tire pressure signal, it relays the information to the on-board compressor system, which then operates to inflate the corresponding tire. Such compressor systems are large and bulky and can be expensive to implement.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention integrates a tire pump with the wheel rim of a vehicle. The pump is activated electromagnetically to automatically inflate the tire when tire pressure is below a required value.  
           [0007]    The pump extends from the atmosphere through the wheel rim and into the interior portion of the tire. The portion of the pump which is exposed to the atmosphere contains an air inlet for allowing air into the pump. A plunger within the pump operates to provide both opened and closed positions. In the open position, air from the atmosphere is allowed into the pump through the air inlet. When the plunger moves to the closed position, air is pushed through a valve into the inflatable portion of the tire.  
           [0008]    The plunger is forced into the open position by a biasing element. The biasing element retains the plunger in the open position until an electromagnet is activated. The electromagnet, which is located on a vehicular component in close proximity with the wheel rim, reacts against the plunger, which is a permanent magnet, forcing the plunger into the closed position. The electromagnet, which is activated upon receiving a low tire signal from the vehicle&#39;s body controller, reacts with the plunger when normal wheel rotation moves the pump within close proximity to the electromagnet. The biasing element returns the plunger to the open position when wheel rotation moves the pump out of the range of the electromagnet.  
           [0009]    Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0011]    [0011]FIG. 1 is a side view of a vehicle wheel employing the integrated air pump and mounted electromagnet of the present invention.  
         [0012]    [0012]FIG. 2 is a cross-section of the vehicle wheel of FIG. 1 employing the air pump and electromagnet of the present invention.  
         [0013]    [0013]FIG. 3 is a diagram showing the pump of the present invention with the piston in the open position.  
         [0014]    [0014]FIG. 4 is a diagram showing the pump in close proximity with the electromagnet, causing the piston to be in the closed position. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0015]    Referring to FIG. 1 and FIG. 2, a vehicle wheel  10  as is used for automotive vehicles includes an inflatable tire  12  which is mounted on a wheel rim  14  having an inner annular surface  16  and an outer annular surface  18 . An inflatable region  20  is disposed between the outer annular surface  18  of the wheel rim  14  and the inner surface of the inflatable tire  12 . The wheel  10  is mounted on an automotive vehicle, bringing the wheel rim  14  in proximity with vehicle components such as the brake rotor  22  and brake caliper support  24 .  
         [0016]    An electromagnetically activated air pump  30  embodying the present invention is integrated with the wheel rim  14 . The pump  30  extends from the inner annular surface  16  to the outer annular surface  18 . As described more fully below, the pump  30  interacts with an electromagnet  32  mounted on the brake caliper support  24  to force air from the atmosphere through the wheel rim  14  and into the inflatable tire  12 .  
         [0017]    Referring to FIG. 2, a cross-section of the vehicle wheel  10  mounted on a vehicle axle  40  is shown. The radially inner portion  42  of the pump  30  is exposed to atmosphere. The pump  30  passes through the wheel rim  14  and terminates with the radially outer portion  44  in fluid communication with the interior of inflatable tire  12 . An electromagnet  32  is mounted on a vehicular component within the perimeter defined by the inner annular surface  16  of the wheel rim  14 . Although the electromagnet  32  as shown is mounted on the brake caliper support  24 , those skilled in the art will anticipate that the electromagnet  32  may be mounted on other proximate vehicular components. Likewise, the pump  30  may be mounted elsewhere on the annular portion of the wheel rim  14 . In one possible alternative arrangement, the pump  30  is mounted parallel to the axis of the wheel  10 . In this arrangement, the centrifugal force created by tire rotation has a minimized effect on the performance of the pump  30 .  
         [0018]    As shown in FIG. 3, the pump  30  includes an air inlet  50 . The air inlet  50  is disposed on the radially inner portion  42  of the pump body  52 . A plunger  54  having a magnet integrated therewith is disposed within the pump body  52 . The plunger  54  may be magnetic, or include a magnetic component fixedly attached thereto. The plunger  54  is shown in the open position, which allows air from the atmosphere to enter the pump body  52  through the air inlet  50 . A biasing element  56  retains the plunger  54  in the open position. As shown, the biasing element  56  is illustrated as a spring. In one possible alternative embodiment, the biasing element  56  may be a permanent magnet disposed within the pump body  52  which retains the magnetic plunger  54  in the open position. The air inlet  50  can be a one-way valve which allows air from the atmosphere through the air inlet  50  into the pump body  52 , but prevents air from within the pump body  52  from entering the atmosphere.  
         [0019]    Referring to FIG. 3 and FIG. 4, the radially outer portion  44  communicates with the inflatable tire  12 . Air within the pump body  52  is forced through the radially outer portion  44  as the magnetic plunger  54  moves into the closed position, as shown in FIG. 4. In the exemplary embodiment shown, the radially outer portion  44  includes a one-way valve  58  which allows air to enter the inflatable tire  12  but prevents air from entering the pump body  52  from the inflatable tire  12 . The shape of the plunger  54  is substantially equivalent to that of the pump body  52  so as to allow the plunger  54  to reciprocate within the pump body  52 . In one embodiment, the plunger  54  and the pump body  52  are cylindrical.  
         [0020]    The electromagnet  32  is fixedly located so that normal rotation of the wheel rim  14  will move the pump  30 , and therefore the magnetic plunger  54 , within proximity of the electromagnet  32 . When the magnetic plunger  54  is within a predetermined range of the electromagnet  32 , if the electromagnet  32  is energized a force is exerted on the plunger  54  of sufficient strength to overcome the biasing element  56 , causing the plunger  54  to move to the closed position as shown in FIG. 4. When normal rotation of the wheel rim  14  moves the plunger  54  out of proximity with the electromagnet  32 , the resulting absence of magnetic force upon the plunger  54  from the electromagnet  32  allows the biasing element  56  to return the plunger  54  to the open position as shown in FIG. 3.  
         [0021]    The electromagnet  32  includes an electric coil  60 . When the electric coil  60  is selectively energized, it provides the magnetic field of the electromagnet  32 . When the electric coil  60  is not energized, no magnetic field is produced, regardless of whether the plunger  54  and electromagnet  32  are in proximity. In an alternative embodiment, the electromagnet  32  is a permanent magnet which is enhanced by the electric coil  60 . When the electric coil  60  is energized, the strength of the resulting magnetic field is added to the strength of the permanent magnet. With this arrangement, the relative size of the electromagnet  32  and the electric coil  60  may be reduced while maintaining sufficient strength to overcome the biasing element  56 . Correspondingly, the power delivered to the electric coil  60  may be reduced.  
         [0022]    When pressure in the inflatable tire  12  is low due to insufficient air such as detected by a tire pressure monitoring arrangement, the electric coil  60  receives an activation command from a vehicle controller (not shown). When the coil is activated, the electromagnet  32  and biasing element  56  exert off-step opposing forces upon the plunger  54  due to normal rotation of the wheel rim  14 . The subsequent reciprocating motion of the plunger  54  causes air to be drawn into the pump body  52  through the air inlet  50  and then pumped into the inflatable tire  12 . When pressure within the inflatable tire  12  returns to a sufficient level, the electric coil  60  is deactivated, and the plunger  54  returns to the open position.  
         [0023]    It is to be understood that the configuration of the pump  30  may be implemented in ways other than those illustrated. In one embodiment, the electromagnet  32  forces the plunger  54  into the open position, and the biasing element  56  returns the plunger  54  to the closed position. Alternatively, the radially outer portion  44  of the pump  30  further comprises a valve which allows air to enter the pump body  52  from the inflatable tire  12  when pressure within the inflatable tire  12  is excessive. Such a situation may arise due to ambient temperature changes.  
         [0024]    It is also to be understood that the activation of the electric coil  60  may be achieved using different methods. In one embodiment, the electric coil  60  is activated by a controller. Alternatively, the electric coil  60  can be selectively activated by a vehicle operator from within the vehicle. Additionally, the tire pressure at which the electric coil  60  is activated may be varied according to operator preference, tire specifications, and environmental conditions. In the case of a leak in the inflatable tire  12 , the electric coil  60  will experience near-continuous activation. In this circumstance, a feedback or other suitable detection arrangement capable of detecting such constant, or near constant, activation of the pump could be provided to notify the operator that such a leak is present.  
         [0025]    The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.