Abstract:
A tire wheel having an air pressure regulator capable of immediately varying the air pressure of a tire of a vehicle in accordance with external environments is disclosed. To regulate the internal air pressure of the tire, the air pressure regulator includes a vacuum chamber, an ultra-high pressure chamber, and a generator for generating electricity to drive the air pressure regulator. The air pressure regulator is actuated by a force generated when the tire is pressed by the ground during the rolling of the tire. An electronic controller collects data obtained by various sensors, and communicates with a central processing unit in a wireless manner. The central processing unit processes the collected data. The driver can monitor all tire states, and can set a control mode associated with the air pressure of the tire. It is possible to deflate the tire in a moment in accordance with the vacuum pressure of the vacuum chamber. The tire can also be inflated in a moment in accordance with an injection of high-pressure air from the high-pressure air chamber. Accordingly, there is no inconvenience caused by a manual regulation for the air pressure of the tire. Also, it is possible to effectively cope with a sudden situation.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation application of prior International Application No. PCT/IB2006/050464, filed Feb. 13, 2006, entitled “TIRE WHEEL CAPABLE OF TWO PHASES OF AIR PRESSURE”, which claims priority to Canadian Patent Application No. 2,498,590, filed Feb. 16, 2005, entitled “TIRE WHEEL CAPABLE OF TWO PHASES OF AIR PRESSURE”, and Canadian Patent Application No. 2,524,612, filed Nov. 3, 2005, entitled “TIRE WHEEL CAPABLE OF TWO PHASES OF AIR PRESSURE”, the contents of which are incorporated herein in their entirety. 
       TECHNICAL FIELD  
       [0002]    The present invention relates to a tire wheel having an air pressure regulator capable of regulating the air pressure of a tire mounted to a vehicle, and more particularly, to a tire wheel having an air pressure regulator capable of automatically regulating the air pressure of a tire in accordance with an external environment during running of a vehicle. 
       BACKGROUND ART  
       [0003]    Generally, tires made of a rubber material are mounted to a vehicle. The tires are inflated to effectively absorb impact or the like generated during the running of the vehicle, and thus to achieve an improvement in ride quality. 
         [0004]    The air pressure of a tire mounted to a vehicle may vary depending on ambient temperature. The tire air pressure may also vary due to leakage of air from the tire. For example, when ambient temperature is high, the air in the tire expands, thereby causing the air pressure of the tire to increase. On the other hand, when ambient temperature is low, the air in the tire shrinks, thereby causing the air pressure of the tire to decrease. 
         [0005]    Since the air pressure of the tire varies depending on an external environment, the driver inflates or deflates the tire, to maintain the tire at a desired air pressure in spite of a variation in external environment, and thus to enable the vehicle to run in an optimal running state. 
         [0006]    However, the air pressure of the tire desired by the driver is not always optimal in all external environments. 
         [0007]    For example, when the air pressure of the tire is low, a degradation in fuel economy occurs, but the braking distance upon an abrupt braking operation of a brake is shortened. On the other hand, when the air pressure of the tire is high, an enhancement in fuel economy is achieved, but the braking distance upon the abrupt braking operation is lengthened. 
         [0008]    For this reason, typically, the air pressure of the tire is set to satisfy certain performances under various conditions, rather than to satisfy a maximum performance required for only one of the conditions. For example, the air pressure of the tire is set to be within a range satisfying certain performances as to fuel economy and braking distance. 
         [0009]    The driver drives a vehicle, to which the tire having the air pressure set in the above-mentioned manner is mounted. 
         [0010]    However, the tire air pressure set to a fixed level, as mentioned above, is not always advantageous for the user. 
         [0011]    For example, when the running speed of the vehicle is very high, the tire may be damaged by heat generated and accumulated due to flattening of the tire. In severe cases, the tire may puncture. In order to avoid such phenomena, it is necessary to increase the air pressure of the tire in proportion to the load and running speed of the vehicle. 
         [0012]    On the other hand, when the air pressure of the tire is low, the braking distance is short. However, when the air pressure of the tire is low under the condition in which the vehicle runs on a wet road, a hydroplaning phenomenon may occur. In this case, the braking distance rather increases. 
         [0013]    Therefore, it is frequently required to appropriately vary the air pressure of the tire in accordance with external environments (the load of the vehicle, the road surface state, and weather) . However, to vary the air pressure of the tire before driving the vehicle, based on a prediction of external environments, is only the measure taken by the driver to cope with the external environments. Otherwise, the driver should replace the tire with a specific tire capable of exhibiting an optimal function for external environments, such as an anti-slip tire or a snow tire. 
         [0014]    However, it is impossible to immediately vary the air pressure of the tire in accordance with external environments such as the load of the vehicle, weather, and road surface state because such external environments vary from hour to hour. 
       SUMMARY OF THE INVENTION  
       [0015]    The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention is to provide a tire wheel having an air pressure regulator capable of immediately varying the air pressure of a tire of a vehicle in accordance with external environments, thereby providing optimal driving conditions for the driver. 
         [0016]    Another object of the present invention is to provide a tire wheel having an air pressure regulator capable of automatically regulating an optimal air pressure of a tire in accordance with external environments, thereby eliminating a requirement for the driver to vary the air pressure of the tire. 
         [0017]    The objects of the present invention can be achieved by providing a tire wheel comprising: at least one air pressure regulator arranged between a wheel of a vehicle and a tire, to automatically regulate an internal air pressure of the tire in accordance with external environments including a load of the vehicle, a weather, a road state. 
         [0018]    The at least one air pressure regulator may comprise a plurality of air pressure regulators symmetrically mounted in the tire. 
         [0019]    The air pressure regulator may comprise a cylinder extending along an outer peripheral surface of the wheel while communicating with an interior of the tire, an ultra-high pressure chamber storing ultra-high pressure air required to rapidly increase the air pressure of the tire, and an actuator for actuating the cylinder and elements of the ultra-high pressure chamber. 
         [0020]    The air pressure regulator may further comprise a piston arranged in the cylinder such that the piston is in contact with an inner peripheral surface of the cylinder, to push air, present in a space defined between the cylinder and one side of the piston, into the interior of the tire, while forming a vacuum in a space defined between the cylinder and the other side of the piston, and a rack gear connected to the piston, the rack gear moving in accordance with an operation of the actuator. 
         [0021]    The actuator may comprises a reciprocating bar, a first rotating gear, which rotates in accordance with a reciprocation of the bar, and a second rotating gear, which rotates in accordance with the reciprocation of the bar. 
         [0022]    The first rotating gear may comprise a first outer gear engaged with the bar, and a first inner gear engaged with the rack gear. The air pressure regulator may further comprise an electronic latch for controlling an engagement between the first outer gear and the first inner gear. 
         [0023]    The air pressure regulator may further comprise an electronic stopper for preventing the inner gear from rotating in one direction when the bar reciprocates. The air pressure regulator may further comprise vanes formed at the inner gear, and a nozzle for injecting the ultra-high pressure stored in the ultra-high pressure chamber onto the vanes. 
         [0024]    The second rotating gear may comprise a second outer gear engaged with the bar, and a second inner gear for actuating a pump for introducing the air discharged from the high-pressure chamber into the high-pressure chamber. 
         [0025]    The air pressure regulator may further comprise first and second plate springs for applying a resilience to the second outer gear and the second inner gear, respectively, such that the second outer gear and the second inner gear return to respective original positions after rotating in one direction. 
         [0026]    The pump may comprise a pump cylinder defining a space for sucking and compressing air, a piston, which reciprocates in the pump cylinder, and compresses air present in the pump cylinder, a connecting rod connecting the second inner gear and the piston, and a valve device arranged at one end of the pump cylinder, to control suction and discharge of air. 
         [0027]    The air pressure regulator may further comprise a displacement sensor for measuring a displacement of the bar, a first pressure sensor for measuring the internal air pressure of the tire, a second pressure sensor for measuring the internal pressure of the ultra-high pressure chamber, and a centrifugal force sensor for measuring a centrifugal force generated at the tire. The air pressure regulator may further comprise an electronic controller, which collects data obtained by the sensors, and communicates with a central processing unit mounted to the vehicle. 
     
    
     
       DESCRIPTION OF DRAWINGS  
         [0028]    The accompanying drawings, which are included to provide a further understanding of the invention, illustrate embodiments of the invention and together with the description serve to explain the principle of the invention. 
           [0029]    In the drawings: 
           [0030]      FIG. 1  is a sectional view illustrating the overall configuration of a tire wheel having an air pressure regulator according to an exemplary embodiment of the present invention. 
           [0031]      FIG. 2  is an enlarged view illustrating an actuator included in the air pressure regulator shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0032]    Reference will now be made in detail to the preferred embodiments of the present invention associated with an air pressure regulator, examples of which are illustrated in the accompanying drawings. 
         [0033]    Referring to  FIG. 1 , an air pressure regulator  10  according to an exemplary embodiment of the present invention is illustrated. The air pressure regulator  10  is arranged between a wheel  1  of a vehicle and a tire  2  fitted around the wheel  1 , to automatically regulate the air pressure of the tire  2 . Preferably, a plurality of air pressure regulators  10  are arranged between the wheel  1  and the tire  2 . In this case, it is preferred that the air pressure regulators  10  be symmetrically arranged. 
         [0034]    As shown in  FIG. 1 , the air pressure regulator  10  mainly includes a cylinder  100  extending along an outer peripheral surface of the wheel  1  while communicating with the interior of the tire  2 , an ultra-high pressure chamber  300  storing ultra-high pressure air to cope with the case in which it is necessary to rapidly increase the air pressure of the tire  2 , and an actuator  200  for actuating the cylinder  100  and various elements of the ultra-high pressure chamber  300 . 
         [0035]    The interior of the cylinder  100  communicates with the interior of the tire  2  via a connecting passage  101 . A piston  120  is arranged in the cylinder  100 . The piston  120  is connected to the actuator  200  by a rack gear  110  having the same curvature of radius as the cylinder  100 . The piston  120  functions to push air, present in a space defined between the cylinder and one side of the piston  120 , into the interior of the tire  2  via the connecting passage  101 , while forming a vacuum in a space defined between the cylinder and the other side of the piston  120 . The piston  120  is in close contact with the inner peripheral surface of the cylinder  100 . Accordingly, when the piston  120  moves in the cylinder  100 , the internal pressure of the cylinder  100  varies. The pressure variation of the cylinder  100  causes a variation in the air pressure of the tire  2  communicating with the cylinder  100 . 
         [0036]    When the piston  120  moves in a clockwise direction (right direction) in  FIG. 1 , air present in the cylinder  100  is introduced into the tire  2  via the connecting passage  101 , so that the air pressure of the tire  2  increases. On the other hand, when the piston  120  moves in a counter-clockwise direction (left direction) in  FIG. 1 , air present in the tire  2  is discharged into the cylinder  100 , so that the air pressure of the tire  2  decreases in a moment. 
         [0037]    Hereinafter, the actuator  200  briefly described above and a configuration associated therewith will be described in detail with reference to  FIG. 2 . 
         [0038]    As shown in  FIG. 2 , the actuator  200  includes a bar  210  arranged to linearly move in a radial direction when the tire  2  rolls, a first rotating gear  220 , which rotates in accordance with the linear movement of the bar  210 , to move the rack gear  110  connected to the piston  120 , and a second rotating gear  250 , which rotates in accordance with the linear movement of the bar  210 , to actuate a pump such that air discharged from the ultra-high pressure chamber  300  is again introduced into the ultra-high pressure chamber  300 . The pump will be described later. 
         [0039]    The bar  210  includes a head  211  having a convex surface coming into contact with the inner surface of the tire  2  when the tire  2  rolls, and a rod  212  extending from the head  211  and having rack gears  212   a  and  212   b  respectively formed at opposite sides of the rod  212  and engaged with the first and second rotating gears  220  and  250 . 
         [0040]    The first rotating gear  220  includes a first outer gear  230  engaged with the bar  210 , and a first inner gear  240  arranged inside the first outer gear  230 , and engaged with the rack gear  110 . 
         [0041]    An electronic latch  221  is arranged between the first outer gear  230  and first inner gear  240  of the first rotating gear  220 , to control the engagement between the first outer gear  230  and the first inner gear  240  such that, when the first outer gear  230  rotates, the first inner gear  240  rotates together with the first outer gear  230 , or does not rotate. The electronic latch  221  causes the first outer gear  230  and first inner gear  240  to engage with each other when the bar  210  moves toward the center of the wheel  1 , while preventing the first outer gear  230  and first inner gear  240  from engaging with each other when the bar  210  moves away from the center of the wheel  1 . 
         [0042]    Accordingly, when the first outer gear  230  rotates in the counter-clockwise direction in accordance with the movement of the bar  210  toward the center of the wheel  1 , the first outer gear  230  engages with the first inner gear  240 , thereby causing the first inner gear  240  to rotate. However, when the first outer gear  230  rotates in the clockwise direction in accordance with the movement of the bar  210  away from the center of the wheel  1 , the first outer gear  230  does not engage with the first inner gear  240 . In this case, accordingly, the first inner gear  240  does not rotate. 
         [0043]    An electronic stopper  222  is also provided to prevent the first inner gear  240  from rotating in the counter-clockwise direction when the bar  210  moves upwardly after moving downwardly to cause the first inner gear  240  to rotate together with the first outer gear  230  engaging with the first inner gear  240 . 
         [0044]    Thus, when the bar  210  reciprocates upwardly and downwardly under the condition in which first outer gear  230  and first inner gear  240  selectively engage with each other, the first inner gear  240  rotates little by little in the clockwise direction. In accordance with the clockwise rotation of the first inner gear  240 , the rack gear  110 , which engages with the first inner gear  240 , also moves in the clockwise direction. As a result, the piston  120  connected to the rack gear  110  moves right to push air present in the space defined between the cylinder and one side of the piston  120 , while forming a vacuum in the space defined between the cylinder and the other side of the piston  120 . The air pushed by the piston  120  is introduced into the interior of the tire  2 , thereby increasing the air pressure of the tire  2 . 
         [0045]    A counting sensor  223  is installed on the first rotating gear  220 . The counting sensor  223  counts the number of the teeth of the rack gear  110  shifted during the movement of the rack gear  110 , to identify the position of the piston  120 . 
         [0046]    Meanwhile, when the electronic stopper  222  releases the first inner gear  240 , the first inner gear  240  rotates in the counter-clockwise direction, thereby causing the piston  120  to return to an original position thereof. As the piston  120  returns to the original position, the air pressure of the tire  2  decreases to an initial level in a moment. 
         [0047]    The second rotating gear  250  includes a second outer gear  260  engaged with the bar  210 , and a second inner gear  270  arranged inside the second outer gear  260 , to actuate the pump  280 . 
         [0048]    The second outer gear  260  engages with the rack gear  212   b  formed on the bar  210  such that the second outer gear  260  rotates in the counter-clockwise direction when the bar  210  moves downwardly, while rotating in the clockwise direction when the bar  210  moves upwardly. 
         [0049]    In the second rotating gear  250 , an electronic latch  251  is also arranged between the second outer gear  260  and second inner gear  270 , to control the engagement between the second outer gear  260  and the second inner gear  270  such that, when the second outer gear  260  rotates, the second inner gear  270  rotates together with the second outer gear  260 , or does not rotate. 
         [0050]    That is, when the second outer gear  260  and second inner gear  270  engage with each other by the electronic latch  251 , the second inner gear  270  rotates together with the second outer gear  260  during the rotation of the second outer gear  260 . However, when the second outer gear  660  and second inner gear  270  do not engage with each other, the second inner gear  270  does not rotate in spite of the rotation of the second outer gear  260 . 
         [0051]    An electronic stopper  252  is also provided to prevent the second inner gear  270  from rotating in the clockwise direction when the bar  210  moves upwardly after moving downwardly to cause the second inner gear  270  to rotate together with the second outer gear  260  engaging with the second inner gear  270 . 
         [0052]    First and second plate springs  253  and  254  are also provided to return, to respective original positions thereof, the second outer gear  260  and second inner gear  270 , rotated in the counter-clockwise direction by the bar  210  moved downwardly. 
         [0053]    The first plate spring  253  is connected to the second outer gear  260 , whereas the second plate spring  254  is connected to the second inner gear  270 . Accordingly, when the bar  210  moves downwardly, the second outer gear  260  and second inner gear  270  rotate in the counter-clockwise direction, thereby compressing the first and second plate springs  253  and  254 , respectively. 
         [0054]    When the bar  210  is spaced away from the inner surface of the tire  2  in the compressed state of the first plate spring  253 , the second outer gear  260  rotates in the clockwise direction by the resilience of the first plate spring  253 . At this time, the bar  210  engaged with the second outer gear  260  moves away from the center of the wheel  1 . When the second inner gear  270  rotates though a certain angle in the counter-clockwise direction, the electronic stopper  252  releases the second inner gear  270 . As a result, the second inner gear  270  rotates in the clockwise direction by the resilience of the second plate spring  254 . 
         [0055]    The second inner gear  270  actuates the pump  280  while rotating in the counter-clockwise and clockwise directions. 
         [0056]    The pump  280  includes a pump cylinder  281  defining a space for sucking and compressing air, a piston  282 , which reciprocates in the pump cylinder  281 , and compresses air present in the pump cylinder  281 , a connecting rod  283  connecting the second inner gear  270  and the piston  282 , and a valve device  284  arranged at one end of the pump cylinder  281 , to control suction and discharge of air. 
         [0057]    The connecting rod  283  is connected to the second inner gear  270  near the outer peripheral edge of the second inner gear  270 . Accordingly, when the second inner gear  270  rotates in the counter-clockwise direction, the connecting rod  283  downwardly pushes the piston  282 , thereby causing air present in the pump cylinder  281  to be compressed. On the other hand, when the second inner gear  270  rotates in the clockwise direction, the connecting rod  283  upwardly pulls the piston  282 , thereby causing air to be sucked into the pump cylinder  281 . 
         [0058]    Thus, when the pump  280  operates, air present outside the ultra-high pressure chamber  300  is introduced into the ultra-high pressure chamber  300 . Accordingly, high-pressure air is stored in the ultra-high pressure chamber  300 . 
         [0059]    Meanwhile, a proximity sensor  255  is provided to sense a movement of the connecting rod  283  included in the pump  280 . When the piston  282  reaches the bottom of the cylinder  281 , the proximity sensor  255  senses this state, thereby causing the electronic latch  251  to release the second inner gear  270 . In this state, accordingly, the second inner gear  270  returns to the original position thereof by the second plate spring  254 . 
         [0060]    When no pumping operation of the pump  280  is required, the electronic latch  251  operates to prevent the second inner gear  270  and second outer gear  260  from engaging with each other. In this case, accordingly, the second inner gear  270  does not rotate, so that the piston  282  does not operate. 
         [0061]    The air pressure regulator  10  according to the present invention also includes a generator (not shown), and a battery  400  for accumulating electricity generated by the generator. The electricity accumulated in the battery  400  is used to operate various sensors. These sensors will be described later. 
         [0062]    A stopper  290  is also provide to restrain a movement of the bar  210  when any operation is not required during the rolling of the tire  2 . The stopper  290  operates to engage with the first outer gear  230 . In this case, the bar  210  is maintained at a fixed position without moving away from the center of the wheel  1  even when the bar  210  is spaced away from the inner surface of the tire  2 . 
         [0063]    Meanwhile, there are devices for abruptly increasing the air pressure of the tire  2  when such an abrupt air pressure increase is required. 
         [0064]    In the ultra-high pressure chamber  300 , air compressed in accordance with the operation of the pump  280  is stored. The ultra-high pressure chamber  300  is opened to the first rotating gear  220  via a pipe  310 . A nozzle  320  is mounted to an end of the pipe  310  facing the first rotating gear  220 . An electronic valve  330  is installed at a connection between the pipe  310  and the nozzle  320 , to control opening and closing of a passage defined in the pipe  310 , and thus to control injection of air from the ultra-high pressure chamber  300  through the nozzle  320 . 
         [0065]    Vanes  235  are formed at the first inner gear  240 , to cause the first inner gear  240  to rotate by the high-pressure air injected from the nozzle  320 . 
         [0066]    When a high-pressure air is injected from the nozzle  320 , the vanes  235  receive the pressure of the injected air. When an additional increase in the air pressure of the tire  2  is required, simultaneously with an increase in the air pressure of the tire  2  caused by the injection of the high-pressure air, the first inner gear  240  is allowed to rotate in the clockwise direction by the pressure applied to the vanes  235 . However, when it is only necessary to supply the high-pressure air, the first inner gear  240  is prevented from rotating by the pressure applied to the vanes  235 . 
         [0067]    When the first inner gear  240  rotates in the clockwise direction, the rack gear  110  engaged with the first inner gear  240  moves right. As a result, the air pressure of the tire  2  increases to a desired level in accordance with the operation of the piston  120  and the injection of the high-pressure air, which are simultaneously carried out. 
         [0068]    In order to achieve the instantaneous air pressure increase such that the air pressure of the tire  2  corresponds to a level achieved when the piston  120  is at a position where the piston  120  escapes from the cylinder  100  by a maximum distance, and thus to enable an instantaneous air pressure decrease, which may be subsequently required, the piston  120  further pushes air present in the cylinder  100  in accordance with a reciprocation of the bar  210 . At this time, air is recovered into the ultra-high pressure chamber  300 , and is compressed by the pump  280 . 
         [0069]    Meanwhile, the air pressure regulator  10  according to the present invention further includes a displacement sensor  410  for measuring a displacement of the bar  210 . The air pressure regulator  10  also includes a first pressure sensor  420  for measuring the air pressure of the tire  2 , and a second pressure sensor  430  for measuring the internal pressure of the ultra-high pressure chamber  300 . The air pressure regulator  10  further includes a centrifugal force sensor  440  for measuring a centrifugal force generated at the tire  2 . Accordingly, when an abrupt variation in centrifugal force occurs at the tire  2 , it is sensed by the centrifugal force sensor  440 . Based on the sensed centrifugal force variation, it is possible to sense the level of the braking force or the slippage of the tire  2 . 
         [0070]    An electronic controller  450  is also provided to collect data obtained by the above-described sensors. 
         [0071]    A central processing unit (not shown), which communicates with the electronic controller  450  in a wireless manner, is also provided. Also, an input unit (not shown) is provided to allow the driver to regulate the air pressure of the tire  2 . 
         [0072]    Thus, the driver can attain all information as to the air pressure of the tire  2 , and can directly regulate the air pressure of the tire  2  to an optimal level for external environments by setting an appropriate mode through the input unit. The driver can also set an operation mode for a sudden situation. 
         [0073]    Hereinafter, operation of the air pressure regulator will be described. 
         [0074]    For example, in the case in which a number of passengers ride in the vehicle, the displacement sensor  410  senses a variation in the displacement of the bar  210  caused by a rotation of the tire  2 . Based on the sensing results of the displacement sensor  410 , it is possible to sense the fact that the load of the vehicle has increased. The centrifugal force sensor  440  also senses the rotating speed of the tire  2 . 
         [0075]    When an increase in the load of the vehicle or an increase in running speed occurs, as described above, it is advantageous to increase the air pressure of the tire  2 , in order to achieve an enhancement in fuel economy. 
         [0076]    When the electronic controller  450  controls the stopper  290  to release the bar  210 , the head  211  of the bar  210  comes into contact with the inner surface of the tire  2  during the rotation of the tire  2 . In this case, the bar  210  is upwardly pressed in accordance with a pressure applied from the ground to the bar  210  via the inner surface of the tire  2  when the head  211  comes into contact with the inner surface of the tire  2 . As the bar  210  is upwardly pressed, it moves upwardly, thereby causing the first rotating gear  220  to rotate in the clockwise direction. As the bar  210  is spaced away from the inner surface of the tire  2  in accordance with the rotation of the tire  2 , the bar  210  returns to an original position thereof. When the bar  210  subsequently comes into contact with the inner surface of the tire  2  in accordance with the rotation of the tire  2 , the bar  210  is again upwardly pressed to move upwardly. 
         [0077]    As the bar  210  repeatedly performs a linear reciprocation in the above-described manner, the piston  120  repeatedly pushes air from the cylinder  100  into the interior of tire  2 , to increase the air pressure of the tire  2 . 
         [0078]    The increasing air pressure of the tire  2  is measured by the firs pressure sensor  420 . When the air pressure of the tire  2  reaches an optimal level meeting the load and running speed of the vehicle, the electronic controller  450  controls the stopper  290  to engage with the first outer gear  230 . Accordingly, the internal pressure of the tire  2  is maintained at the optimal level. When it is subsequently necessary to increase the air pressure of the tire  2  in a moment, based on a speed variation of the tire  2  or a slippage of the tire  2  sensed by the centrifugal force sensor  440  upon a sudden braking operation, the electronic stopper  222  releases the first inner gear  240 , to return the piston  120  to the original position thereof. Accordingly, the air pressure of the tire  2  decreases in a moment, thereby increasing the ground contact area of the tire  2 . Thus, an increase in braking force is achieved. 
         [0079]    On the other hand, when the centrifugal force sensor  440  senses the fact that the driver suddenly brakes the vehicle on a wet road, it is necessary to abruptly increase the air pressure of the tire  2 , in order to prevent occurrence of a hydroplaning phenomenon. 
         [0080]    When it is required to abruptly increase the air pressure of the tire  2 , the electronic controller  450  controls the electronic valve  330  to be opened, thereby causing the high-pressure air in the ultra-high pressure chamber  300  to be injected through the nozzle  320 . 
         [0081]    When it is necessary to further increase the air pressure of the tire  2  in accordance with an operation of the piston  120  to a level achieved when the piston  120  is at a position where the piston  120  escapes from the cylinder  100  by a maximum distance, and thus to enable an instantaneous air pressure decrease, which may be subsequently required, the high-pressure air injected through the nozzle  320  applies a pressure to the vanes  235  formed at the first inner gear  240 , to rotate the first inner gear  240  in the clockwise direction. The rack gear  110  is pulled in accordance with the rotation of the first inner gear  240 . As a result, the air pressure of the tire  2  increases rapidly. 
         [0082]    Accordingly, the ground contact area of the tire  2  decreases, so that it is possible to prevent occurrence of a hydroplaning phenomenon. 
         [0083]    It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. 
         [0084]    Thus, the air pressure regulator can regulate the air pressure of the tire  2  in various modes, taking into consideration the fuel economy, the state of the road surface, weather, etc.