60/034,438, filed December 23, 1996.

BACKGROUND OF THE INVENTION This invention relates in general to mechanisms for maintaining air pressure in pneumatic tires for motor vehicles and in particular to a system which automatically maintains a desired and predetermined air pressure.

Low pressure in pneumatic tires for motor vehicles is a primary cause of excessive fuel consumption, tire wear and impaired steerability. A normal tire may leak on the order of 25 percent of its pressure per year due to its inherent permeability. Furthermore, operation of an under-inflated tire increases the heating of the tire which may cause premature tire failure. Unfortunately, with radial bias tires, noticeable under-inflation is typically at an inflation pressure which is significantly lower than the optimal operating inflation pressure. Thus, an under-inflated tire has typically already been operated at the lower pressure before the problem is noticed.

Additionally, with the increase in popularity of four wheel drive vehicles, more vehicle operators are venturing off paved roads. The military has long recognized the enhanced mobility which can be obtained from varying the tire inflation pressure to match the road surfaces. As described in U.S. Patent No.

5,327,346, a high pressure of 60 pounds per square inch (psi) may be best for thigh speed operation of a military vehicle upon a highway. The pressure would

be reduced to approximately 35 psi for cross country operation and 25 psi for sand and mud. As the pressure is reduced, the tire "footprint" is increased to provide better traction and spread the vehicle weight over a larger surface area.

An emergency mode of operation may require further reduction to 12 psi.

Clearly, a wide range of operating pressures is desirable.

Central tire inflation systems which monitor the tire pressure and adjust the pressure as needed are well know in the prior art. Such systems typically include a pressurized air supply, such as a dedicated air compressor, which is centrally located upon the vehicle, or the vehicle air brake system. The air supply is connected to the vehicle tires through rotary seal assemblies mounted upon each of the vehicle wheels. Sensors monitor the tire pressure and the pressure may be adjusted as desired by the vehicle operator. The operator may select an operating mode corresponding the road conditions described above, and the system adjusts the tire pressure accordingly. In the above referenced patent, wheel slip is monitored and correlated to the road surface. The system then automatically adjusts the tire pressure to correspond to the specific type of road surface.

SUMMARY OF THE INVENTION This invention relates to a system which automatically maintains a desired and predetermined air pressure in pneumatic tires for motor vehicles.

As described above, it is known to provide central tire inflation systems to maintain pressure in vehicle tires at a predetermined value. However, such systems tend to be complex, requiring rotary seals to connect the supply of pressurized air to the vehicle tires. Because of the complexity and associated cost of central tire inflation systems, it would be desirable to provide a simpler system for maintaining a predetermined inflation pressure in a vehicle's tires. It

also would be desirable to provide a simpler system which includes the capability for the vehicle operator to remotely vary the tire pressure setting.

The present invention contemplates a tire pressure regulating system having an air pump adapted to mounted upon a vehicle wheel. The pump is driven by rotation of the vehicle wheel and has an outlet port adapted to be connected to a pneumatic tire mounted upon the vehicle wheel. The system also includes a pressure regulating valve coupled to the pump outlet port. The pressure regulating valve is operational to maintain the air pressure in the pneumatic tire at a predetermined pressure.

The tire pressure regulating system can also include a check valve connected between the pump outlet port and the pneumatic tire. The check valve is operational to open to allow air to flow into the pneumatic tire and to close to prevent air flow out of the pneumatic tire.

It is further contemplated that the pressure regulating valve includes a pressure relief valve connected between the pump outlet port and atmosphere.

The relief valve is set for the predetermined pressure and operational to open when pressure from the pump outlet port exceeds the predetermined pressure.

Alternately, the pressure regulating valve can include a solenoid operated proportional valve connected between the pump outlet port and the pneumatic tire. The proportional valve is operational to control the pressure in the pneumatic tire. Alternately, the proportional valve can be connected between the pump outlet port and atmosphere.

It also is contemplated that the pressure regulating valve solenoid is connected to a receiver. The receiver is capable of generating a control signal which is applied to the solenoid. The solenoid is responsive to the control signal to open the proportional valve sufficiently that the air pressure in said pneumatic tire is maintained at the desired pressure. The tire pressure regulating system can

further include a transmitter to generate an air pressure signal as selected by the vehicle operator. The air pressure signal is received by the receiver which is responsive thereto to generate the control signal.

It is further contemplated that the tire pressure regulating system can include an air pressure sensor mounted within the pneumatic tire air cavity. The sensor is responsive to the air pressure in the tire cavity to generate an air pressure reading signal which is received by the transmitter. The transmitter is, in turn, responsive to the air pressure reading signal to generate the air pressure signal.

The invention also contemplate a tire pressure regulating system having a pressure regulating valve which includes at least one normally closed solenoid valve having an inlet port connected to the pump outlet port. The solenoid valve also has an outlet port connected to a pressure relief valve which is set to relieve to atmosphere at a predetermined pressure. The solenoid valve is operable upon being actuated to connect the pressure relief valve to the pump outlet port. It is further contemplated that the solenoid valve is connected to a receiver which generates a control signal. The control signal is applied to the solenoid valve, which is responsive to the control signal to connect the pressure relief valve to the pump outlet port such that the air pressure in the pneumatic tire is maintained at the desired pressure. The receiver is responsive to signals generated by the transmitter described above to generate the control signal.

It also is contemplated that the pressure regulating valve includes a plurality of normally closed solenoid valves, each of which has an inlet port connected to the pump outlet port. Each of the solenoid valves has an outlet port connected to an associated pressure relief valve. Each of the pressure relief valves is set for a different predetermined relief pressure. The solenoid valves are connected to the receiver and responsive to the control signal to connect one

of the pressure relief valves to the pump outlet port. Accordingly, the tire pressure can be varied through the selection of a particular pressure relief valve.

Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a front view of a tire pressure regulating system in accordance with this invention mounted upon a vehicle wheel assembly.

Fig. 2 is a fragmentary sectional view taken along line 2-2 in Fig. 1.

Fig. 3 is a schematic diagram of the tire pressure regulating system illustrated in Fig. 1.

Fig. 4 is an alternate embodiment of the tire pressure regulating system shown in Fig. 3.

Fig. 5 is a schematic diagram illustrating another alternate embodiment of the tire pressure regulating system shown in Fig. 1 which includes a proportional regulator valve.

Fig. 6 is a schematic diagram illustrating an alternate embodiment of the tire pressure regulating system shown in Fig 5.

Fig. 7 is a schematic diagram another alternate embodiment of the tire pressure regulating system shown in Fig. 1 which includes valving for varying the tire pressure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, there is illustrated in Figs. 1 and 2, a tire pressure regulating system, indicated generally at 10, in accordance with this invention. The tire pressure regulating system 10 is attached to a wheel

assembly 11 which includes a pneumatic tire 12 mounted upon a vehicle wheel 13. The wheel 13 includes an annular rim 14 which supports the tire 12 and cooperates therewith to define an air chamber 15 within the tire 12. A circular wheel disc 16 extends across the outboard end ofthe wheel rim 14. The wheel disk 16 includes a central hub 17 which is supported by a plurality of radially extending spokes 18 within the wheel rim 14. A central pilot hole 19 and a plurality of lug holes 20 extend axially through the wheel hub 17. When the wheel assembly 11 is mounted upon a vehicle (not shown), wheel lugs (not shown) extend through corresponding lug holes 20 and receive wheel nuts (not shown) to secure the wheel assembly 11 to the vehicle.

The tire pressure regulating system 10 includes a housing 25 which is attached to a mounting plate 26. In the preferred embodiment, the mounting plate 26 includes a plurality of ears 27 which extend over several of the lug holes 20 in the wheel disc 16. Apertures formed through the mounting plate ears 27 are collinear with corresponding lug holes 20. Accordingly, the housing 25 and mounting plate 26 can be secured to the wheel assembly 13 with the wheel lugs and nuts (not shown).

As shown in the schematic diagram in Fig. 3, the housing 25 includes a pump 30 for compressing air. In the preferred embodiment, a pendulum driven pump, which is described in co-pending U.S. Patent Application No. 08/904,135, which is hereby incorporated by reference, is used for the pump 30. However, it will be appreciated that other commercially available pumps may be used. The pump has an inlet port 31 which communicates through a filter 32 with the atmosphere. The pump 30 also has an outlet port 33 which communicates with a pressure regulating valve 35. As the wheel assembly 13 rotates, the pump 30 is operational to draw air through the filter 32 and inlet port 31 and into the pump 30. The pump 30 compresses the air and discharges the compressed air through

the outlet port 33. As will be explained below, the pump 30 and pressure regulating valve 35 co-operate to maintain a desired air pressure within the air chamber 15. Additionally, in certain embodiments of the invention, the pressure in the air chamber 15 can be selectively increased or decreased by the vehicle operator.

An air supply conduit 40 extends from the pump outlet port 30 to the wheel rim 14. As best seen in Fig. 2, the conduit 40 communicates with the air chamber 15. As illustrated in Figs. 1 and 2, the conduit 40 is shown as a flexible tube extending from the housing 25 to the wheel rim 14 where the end of the conduit 40 can be attached to the wheel assembly valve stem (not shown).

However, it will be appreciated that the invention can be practiced with an alternate structure for the conduit 40. For example, the conduit 40 could extend radially along the inboard surface of one of the wheel spokes 18 (not shown) to the inner surface of the wheel rim 14. Alternately, the tire pressure regulating system 10 could be mounted upon a wheel having a air channel formed within one of the spokes (not shown) which would transfer the compressed air from the pump outlet port 33 to the air chamber 15.

An optional air pressure gauge 41 is mounted upon the outboard face of the housing 25. The air pressure gauge 41 communicates with the conduit 40 to provide a visual indication of tire air pressure within the air chamber 15. The pressure gauge 41 may be color coded or have indicia means printed thereon corresponding to the tire air pressure in the air chamber 15.

An optional decorative cover 45, shown in phantom in Fig. 2, can be attached to the wheel disc 16 to cover the housing 25 and mounting bracket 26.

If needed, the cover 45 can include an aperture to allow access to the air pressure gauge 41.

The tire pressure regulating system 10 also may include an optional tire pressure sensor 46 mounted on an outer surface ofthe wheel rim 14 which measures the pressure in the air chamber 15. The tire pressure sensor 46 is operative to transmit an air pressure signal, such as by a radio transmitter (not shown), to a receiver (not shown), located in the interior of the vehicle, such as in the dashboard (not shown). The receiver is responsive to the signal to provide a visual and/or audible indication of current tire pressure. The receiver also can signal a low or high tire air pressure in the associated air chamber 15.

In the preferred embodiment, as shown in Fig. 3, the tire pressure regulating system 10 also includes a check valve 50 which is between the conduit 40 and the air chamber 15. The check valve 50 is operational to open to allow air to flow into the air chamber 15 and to close to prevent air flow out of the air chamber 15. Additionally, the check valve 50 prevents loss of air from the air chamber 15 when the vehicle is stationary.

The operation of the tire pressure regulating system 10 will now be explained. As explained above, the pump 30 is continually operative while the vehicle is in motion to supply compressed air to the conduit 40. The pressure regulating valve 35 shown in Fig. 3 includes a pressure relief valve 51 which is preset to a desired tire pressure and is vented to the atmosphere. The pump 30 is rated to compress air to a higher pressure than the maximum setting for the pressure relief valve 51. Thus, for example, if the maximum setting for the pressure relief valve is 35 psi, the pump 30 could be rated to compress air up to 40 psi. When the air pressure in the conduit 40 exceeds the preset pressure, the relief valve 51 opens to vent air from the conduit 40 to the atmosphere, thus reducing the air pressure in the conduit 40. Once the air pressure in the conduit 40 returns to the preset value, the relief valve 51 closes. Accordingly, the relief valve maintains the air pressure in the conduit 40 at the preset value. If the air

pressure in the air chamber 15 drops below the preset pressure, the check valve 50 opens to allow additional air to flow from the conduit 40 into the air chamber 15. The additional air raises the pressure within the air chamber 15 to the preset pressure. Additionally, if there should be a pump failure, the check valve 50 closes to seal the air chamber 15 and prevent any loss of air. In the preferred embodiment, an adjustable pressure relief valve 51 is used to allow adjustment of the tire pressure; however, the invention also can be practiced with a fixed pressure relief valve.

An alternate embodiment of the tire pressure regulating system 10 is illustrated by the schematic diagram shown in Fig. 4. Components shown in Fig.

4 which are the same as shown in Fig. 3 have the same numerical designators.

As can be seen, the check valve 50 is located between the pump 30 and the relief valve 51. Accordingly, the air chamber 15 communicates directly with the relief valve 51. This allows build up of excess pressure, as could occur upon the tire being heated during extended highway driving, to be bled from the air chamber 15 by the relief valve 51.

Another embodiment of the tire pressure regulating system 10 is shown in Fig. 5. Components shown in Fig. 5 which are the same as shown in the preceding figures have the same numerical designators. The pressure regulating valve 35 includes a solenoid operated proportional valve 55. The proportional valve 55 has a variable orifice which is opened by a proportional solenoid 56.

the solenoid 56 is responsive to an applied voltage to move a solenoid armature (not shown) an axial distance which is proportional to the magnitude of the applied voltage. In the preferred embodiment, the valve 55 includes a slidable valve spool (not shown) which is coupled to the solenoid armature to adjust the variable orifice opening. As the orifice opens, the pump 30 supplies more compressed air into the conduit 40 and air chamber 15 to increase the air

pressure in the air chamber 15. The wider the orifice is opened, the greater the increase in air pressure. In the preferred embodiment, the proportional valve blocks the conduit 40 when deactuated.

The solenoid 56 is electrically connected, as shown by the dashed line, to a receiver 57. The receiver 57 receives electric power from a self-contained supply 58, such as a battery. The system 10 further includes a transmitter 59 which is mounted upon the vehicle dashboard. The transmitter 59 is operative to generate an air pressure signal which is received by the receiver 57. The receiver 57 is responsive to the air pressure signal to generate a control signal which, in the preferred embodiment, is a voltage having a magnitude proportional to the desired tire pressure. The control signal is applied to the solenoid 56. In the preferred embodiment, the transmitter 59 includes a switch (not shown) for selecting one of a plurality of desired air pressures. An air pressure signal corresponding to the switch setting is transmitted to the receiver 57. The receiver 56 then generates a control signal which corresponds to the received signal. The proportional valve 55 is responsive to the air pressure signal to open the orifice sufficiently to increase the air pressure in the conduit 40 to the desired pressure. Thus, the vehicle operator can vary the tire pressure to suit changing terrain conditions while the vehicle is in motion.

The system 10 also includes an optional pressure relief valve 60 which communicates with the conduit 40. As shown in Fig. 5, the pressure relief valve 60 is connected to the conduit 40 between the proportional valve 55 and the air chamber 15. Thus, the relief valve 60 is operative to prevent over-inflation of the tire 12 if the proportional valve 55 should malfunction and remain in an open position. Alternately, an optional pressure relief valve can be connected to the conduit 40 between the check valve 50 and the proportional valve 55 (not shown) to relieve air compressed by the pump 30 while the vehicle is in motion

and the proportional valve 55 is closed. The invention also contemplates including two relief valves (not shown), with the first relief valve connected as shown in Fig. 5 and the second relief valve connected between the check valve 50 and the proportional valve 55.

It is further contemplated that the transmitter 59 also can receive air pressure reading signals from the air pressure sensor 46 and be responsive thereto to adjust the pressure in the air chamber 15. Alternately, the air pressure reading signals can be received directly by the receiver 57. The receiver 57 would then be responsive thereto to maintain the tire pressure.

Another embodiment of the system 10 is illustrated in Fig. 6. As before, components shown in Fig. 6 which are the same as shown in the preceding figures have the same numerical designators. The system shown in Fig. 6 is similar to the system shown in Fig. 5; however, the proportional valve 55 vents the conduit 40 to atmosphere. Thus, the system shown in Fig. 6 is similar in construction and operation to the system shown in Fig. 4 and described above.

The system further can include an optional relief valve 60 which vents the conduit 40 to the atmosphere to prevent overpressurization if there is a component malfunction.

Another embodiment of an adjustable tire pressure regulating system is shown generally at 65 in Fig. 7. As before, components shown in Fig. 7 which are the same as shown in the preceding figures have the same numerical designators. The pressure regulating valve 35 includes a plurality of pressure relief valves which vent to atmosphere and are calibrated in decreasing incremental steps. A first pressure relief valve 66 is connected directly to the conduit 40 and is set for the greatest relief pressure, which is shown for illustrative purposes as 40 psi. Accordingly, the first pressure relief valve 66 functions as a safety valve for the system 65. A second pressure relief valve 67

is connected through a normally closed solenoid valve 68 to the conduit 40. The second pressure relief valve 67 is set to open at an incrementally lower relief pressure, which is shown for illustrative purposes as 35 psi. Similarly, a third relief valve 69 set for a 30 psi relief pressure is connected through a corresponding normally closed solenoid valve 70 to the conduit 40 and a fourth relief valve 71 set for a 25 psi relief pressure is connected through a corresponding normally closed solenoid valve 72 to the conduit 40. The solenoid valves 68, 70 and 72 are electrically connected to the receiver 57. An appropriate air pressure signal is generated by the transmitter 59 in response to a switch setting by the vehicle operator or a signal received from the air pressure sensor 46. The receiver 57 is responsive to air pressure control signals received from the transmitter 59 to actuate one of the solenoid valves. Upon opening one of the solenoid valves 68, 70 or 72, the conduit 40 is connected to the corresponding relief valve 67,69 or 71, respectively. Accordingly, as was described above for Fig. 4, the pressure in the air chamber 15 will be maintained at the value of the relief pressure setting for the selected pressure relief valve.

When the vehicle operator selects another pressure, a different signal will be generated by the transmitter 59 which will deactuate the current solenoid, allowing the associated valve to close, and actuate a different solenoid to open the associated valve and connect the corresponding relief valve to the conduit 40.

In the preferred embodiment, each valve is responsive to a different frequency signal generated by the transmitter 59; however, other signal modulation also can be used. Thus, the pressure in the air chamber 15 and be remotely varied in discrete increments by the vehicle operator while the vehicle is in motion.

While three pressure relief valves and associated solenoid valves are shown in Fig. 7, it will be appreciated that more or less valves may be used.

Additionally, the relief pressure settings shown are meant to be illustrative and it

will be appreciated that the invention can be practiced with other pressure settings.

One advantage of this invention is that the pressure in the associated tire air chamber 16 may be selectively controlled or adjusted while the vehicle is in motion. Also, the pressure in the tire air chamber 15 may be measured and adjusted without the complexity of air lines and/or wires passing through the hub of the associated tire and wheel assembly 11. In addition, the tire pressure regulating systems 10 and 65 may be used to alert the vehicle operator of low tire air pressure, thereby indicating that a tire may be losing air. Also, the pressure gauge 41 provides the vehicle operator a convenient visual check that the tire pressure indicating system 10 is properly working.

In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope. For example, while the system has been illustrated and described for a single vehicle tire, it will be appreciated that the invention can be applied to all the vehicle tires. Additionally, structural features shown for a particular embodiment can be applied to the other embodiments.

For example, the check valve 50 which is shown in Fig. 5 as being connected between the pump 30 and the proportional valve 55 also can be connected between the proportional valve 55 and the air chamber 15.