CA2755626A1

CA2755626A1 - Automatic tire inflation system and apparatus

Info

Publication number: CA2755626A1
Application number: CA2755626A
Authority: CA
Inventors: Derek Johns
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-10-20
Filing date: 2011-10-20
Publication date: 2013-04-20

Abstract

A tire inflation device for inflating a tire to a set pressure. The device has a compressor mountable within a tire that is in fluid communication with a pressure regulating module. The pressure regulating module is in fluid communication with the compressor and with the atmosphere outside the tire. The pressure regulator opens fluid communication between the compressor and the atmosphere when pressure within the tire drops below a set minimum, the compressor being actuated by compression of the tire on an underlying surface during rotation while driving.

Description

TITLE OF THE INVENTION

AUTOMATIC TIRE INFLATION SYSTEM AND APPARATUS

FIELD OF THE INVENTION

The present invention relates to the field of vehicle tires, and more specifically to a system and apparatus for maintaining proper inflation of a tire.

BACKGROUND OF THE INVENTION

With the number of vehicles on the road always on the increase, vehicle safety remains a significant issue. One of the known safety issues associated with vehicles is low tire pressure. Under inflated tires can make a vehicle more difficult to control and can unexpectedly go flat resulting in significant safety issues. Stopping distances are also increased by under inflated tires. In the United States alone there are hundreds of fatalities and thousands of injuries annually that are directly related to accidents caused by low tire pressure.

Under inflated tires also negatively impact a vehicle's fuel efficiency and cause increased tire wear resulting in shorter tire life ¨ both of which have a serious impact on the environment. Maintaining tires in a properly inflated condition would save millions of liters of unnecessarily burned fuel and hundreds of millions of prematurely wasted tires. Tire manufacturers and the American Automobile Association recommend checking tire pressure on passenger car, SUV and light truck tires on a monthly basis. Heavy truck and trailer tires should be checked more often.
However, very few people follow these guidelines, with most only checking their tire pressure when it is clear that the tire pressure is low. What most people do not realize is that it is very difficult to visually determine if a radial ply tire is properly inflated. In fact, the average driver is incapable of visually determining if tires are properly inflated.

In an effort to prevent tires from being left in an under inflated condition, tire pressure monitoring systems (TPMS) have been developed. These are electronic systems that continuously monitor tire pressure on a vehicle and which alert the driver with an alarm (either visual, auditory or both) when the pressure goes below a set limit.
There are several monitoring system designs. One approach has been to measure the air pressure of the tire itself, while another approach has been to make indirect measurement, such as gauging when the relative size of the tire changes due to lower air pressure. These systems are becoming mandatory in countries such as the United States.

The Transportation Recall Enhancement, Accountability and Documentation (TREAD) Act was passed in the fall of 2000 in the United States. Part of TREAD deals with TPMS; more specifically, the TREAD Act mandated a deadline after which every new car must be equipped with a TPMS. While these monitoring systems are helpful in alerting a driver to a low tire pressure situation, they do not replace the air in the tire.
The driver must still attend to filling the tire to the proper air pressure.
Often it is not convenient for a driver to do so with the result that they continue to drive their vehicle with one or more tires in an under inflated condition. In addition, the criteria for operation of a TPMS as set in the final rule proposed by the National Highways Traffic Safety Administration (NHTSA) allow vehicles to be driven with under inflated tires.
Under the rule set by the NHTSA, for a vehicle using a direct TPMS (with sensors in each tire sending a signal to the dashboard) the TPMS does not have to trigger until the tire is 25 percent below the recommended cold psi. For a vehicle equipped with an indirect TPMS (for example, one that runs off the anti-lock braking system), the TPMS does not have to trigger until the tire is 30 percent below the recommended cold psi. Even with a TPMS system, a driver might not be aware that they are driving a vehicle with tires in an under inflated condition.

In order to resolve the issue of having tires remain in an under inflated condition, a number of tire pressure maintenance systems have been developed. A number of previously designed pressure maintenance systems involve compressing air in a central location and then directing the compressed air through the axle assembly to the wheel with the under-inflated tire. Some designs, specifically directed at the loss of air in highway transport trucks and trailers, utilize the onboard compressed air system primarily used for the braking system. Another method is to compress air somewhere on the vehicle wheel using an electric compressor and then injecting the compressed air into the tire cavity. An example of such a device is taught in U.S.
Patent No. 7,237,590 issued to Loewe. Loewe teaches a device having a microprocessor, a magnetic element and a compressor. The compressor is mounted on the wheel and is in fluid communication with the atmosphere and the tire interior.
The magnetic element, which produces a magnetic field, is mounted on a stationary member of the wheel assembly. Every time the compressor passes the magnetic field it is activated. Loewe also teaches an alternative embodiment in which an electric coil is attached to the wheel to generate power upon passing the magnetic field of the magnetic element, the power being for an electrically-driven compressor.
These prior art designs are costly, involving a complicated design. In addition, these devices are subject to added wear from contact with gravel, rocks and related road debris.

It is therefore an object of an embodiment of the present invention to provide a tire inflation maintenance system and apparatus that is less costly and cumbersome than those taught in the prior art.
Other objects of embodiments of the invention will be apparent from the description that follows.

SUMMARY OF THE INVENTION

The Tire Inflation Maintenance System (TIMS) is designed to maintain the recommended pressure in a regularly used pneumatic tire. In a tire that loses up to 25% of its recommended tire pressure between driving intervals, it will replace this lost air in the tire within a short driving distance. In the event that the tire pressure exceeds the manufacturer's recommendations the system will bleed off the excess pressure back into the atmosphere.

to According to the present invention there is provided a tire inflation device for inflating a tire to a set pressure comprising a compressor mountable within a tire in fluid communication with a pressure regulating module. The pressure regulating module is in fluid communication with the compressor and with the atmosphere outside the tire.
The pressure regulator opening fluid communication between the compressor and the atmosphere when pressure within the tire drops below a set minimum, the compressor being actuated by compression of the tire on an underlying surface during rotation while driving.

Other aspects of the invention will be appreciated by reference to the detailed description of the preferred embodiment and to the claims that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the invention will become more apparent from the following description in which reference is made to the appended drawings and wherein:

Fig. 1 is a cross-section of a tire showing an embodiment of the tire inflation maintenance device of the present invention;

Fig. 2 is a cross-sectional view of the tire valve shown in Fig. 1;

Fig. 2a is a side view of a wheel mounted tire equipped with an alternative filter according to the invention;

Fig. 3 is a cross sectional view of the tire pressure regulator module shown in Fig. 1;

Fig. 3a is a cross sectional view of an alternative tire pressure regulator module;

Fig. 4 is a cross sectional view of the pressure module shown in Fig. 1;

Fig. 5 is a side view showing the pressure module and activating bumper shown in Fig. 1;

Fig. 6 is a cross sectional view of a tire equipped with an alternative embodiment of an automatic tire inflation apparatus; and Fig. 7 is a cross sectional view of a tire equipped with a further alternative embodiment of an automatic tire inflation apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The preferred embodiment of an automatic tire inflation system and apparatus generally referred to by reference numeral 10 is shown in Fig. 1. The tire inflation apparatus 10 is self contained in the cavity 12 of a tire 14. When a tire is under inflated the portion of the tire in contact with the ground undergoes deformation ¨ the tire wall 16 bulges. After it leaves contact with the ground the tire resumes its normal, non-bulging shape. It is this change in shape of a portion of the tire during rotation that provides the energy to work the tire inflation maintenance apparatus and draw air into the tire. This will be discussed in more detail below.

The apparatus 10 is preferably comprised of a pressure module 2, a mount 3, an activating bumper 4, and a pressure regulator 5. The components are preferably constructed of a strong, rugged, lightweight material, such as a nylon or the like, with certain parts, such as the springs and valve components constructed of metal as is known in the art. The weights of these components will be counterbalanced within the tire by placing one or more small weights elsewhere in the tire.

Air from the exterior of the tire is drawn into the tire cavity through the tire valve stem 1. The valve stem 1 is shown in greater detail in Fig. 2. Tire valve stem 1 has a first tube 20 which provides access to the tire cavity for the initial filling (or refilling) of the tire when screw cap 28 is removed from the end. The valve stem 1 also has a second tube 22 within the stem which provides the source of air for the air compressor module 2. Preferably an intake 24 to the second tube 22 is positioned along the side of the valve stem 1 and has a filter 26 directly attached.
Preferably, the filter is a porous bronze filter mounted on the valve stem as shown. Wind velocity and centrifugal force of the rotating wheel act to clear any contaminates that may attach to the filter.

As shown in Fig. 2a, it is also contemplated that the intake 24 to the second tube 22 could be connected via a tube 25 to a porous, non-metallic filter 27 mounted on the wheel 9 behind one of either the wheel cover or wheel cladding, or mounted on the backside of a cast wheel. In addition to providing the source of air intake for the compressor module 2, the second tube 22 also provides external venting in the event of over pressure within the tire. The filter 26 or 27 prevents road debris, such as gravel and dust from being drawn into the tire or otherwise blocking the air intake 24.

A flexible tube 6 is connected at one end to the second tube 22 of the tire stem 1 and at the other end to an inline tire pressure regulator module, generally referred to by reference numeral 5 as shown best in Fig. 3. More particularly, flexible tube connects to the input stem 30 of the pressure regulator module 5. Pressure regulator module 5 has a hard frame 7, made of nylon or the like, with an air channel 35 travelling therethrough, the air channel being formed by input valve stem 30, output valve stem 31, and a central valve tube 34. The tire pressure regulator module provides two functions: 1) it controls the atmospheric air entering the tire for compressing purposes; and 2) it relieves the tire of excess pressure in the event of over inflation, which, for example, could be caused by heat build up, elevation change, or major change in the load on the tire.

The regulation of incoming air is controlled by the action of central valve tube 34, which is preferably constructed of a short section of collapsible tubing, such as surgical tubing or the like. When the pressure inside the tire cavity is sufficiently high, a spring loaded actuator 32 overcomes the resistance of the spring 36 and pinches off central valve tube 34, thereby closing off access to the external air source. A
membrane 33 over the pressure actuator 32 is preferably a pliable material so that the pressure in the tire cavity will activate the pressure actuator. The spring 36 is preferably a compression spring with a spring rate specifically selected to correspond to the desired tire pressure. In other words, for a tire with a desired pressure of 30 PSI, once the tire pressure has reached 30 PSI, the force of the air pressure on the actuator 32 would be sufficient to overcome the resistance of the spring 36 and close central valve tube 34. Preferably, pressure regulator module 5 is also equipped with a release valve 38 that is spring loaded 40 and adapted to release pressure from the tire cavity back through the tire stem 1 through second tube 22 when the tire is over inflated.

An alternative embodiment of a pressure regulator is shown in Fig. 3a. In this embodiment, the pressure regulator is located within the valve stem. The pressure control module is connected to a shorter version of the presently used valve stem. As a valve stem has a brass core surrounded by rubber, the pressure control module is attached to the stem with a threaded connection 13 after the valve stem is pulled through the hole in the wheel 14 and set in place. Air coming through the inlet valve 7 fills the valve stem and in turn the tire cavity. The pressure within the valve stem is therefore the same as the tire cavity and it is this interior pressure which acts against pressure actuator 32A which in turn is forced outward into an open position by spring 36A. When the pressure in the valve stem is sufficiently high, it forces the pressure actuator 32A against the spring 36A, forcing it to pinch off collapsible tubing 34A
thereby blocking fluid communication of outside air by way of filter 26. A
high pressure release valve 38A is present if the pressure within the tire cavity (and therefore the valve stem) is too high. Use of such an attachment allows a user to select pressure regulator specifically calibrated for the tire pressure of that tire. It may also be easily removed should a user so choose.
Compression of the atmospheric air from outside the tire is accomplished by the air compressor or pressure module 2, which is in fluid communication with pressure regulator module 5 by way of a further flexible tube 11, and which will now be described in more detail by reference to Fig. 4. Compressor module 2 has a frame 40 defining a compression chamber 42 having an air intake 41 and an air outlet 43. A
piston 44 is seated in the compression chamber 42 for reciprocating action therein to draw air into, and expel it out of, the chamber 42. The piston 44 is spring loaded with a spring 46. A pair of in-line valves 48 seated within the air intake 41 and air outlet 43 ensures that air can only travel from the inlet to be expelled through the outlet and not in reverse.

The compressor module 2 would have about 340 degrees of the tires rotation to draw air into the compressing module and about 20 degrees of rotation to expel it into the tire cavity. When in operation the piston 44 would expel almost 100% of the air from the module's compression chamber 42. The spring 46 is preferably a compression spring encircling the piston 44 having a specific spring rate to provide the desired air pressure within the tire. In other words, the desired spring would be just strong enough to push out the piston when air is available from the pressure regulator 5, thereby drawing air into the compression chamber 42 when the pressure regulating valve is allowing air into the tire. If the tire pressure is up to the specified level, the pressure regulating module would be closed and the compressor module would eventually cease operating as a result of the ensuing vacuum created by evacuating all the remaining air from the compressor. At this point the compressor module would be inactive or dormant.
For a passenger car tire, the movement between the rim of the tire and the road surface compared to the distance between the rim and the tread of the tire when it is not being squished is approximately %" to 1 1/16" (20mm to 27mm). This would be the minimum compression distance of the compressor. The compression distance would increase for tires in an under inflated condition, as the "squish" would be greater. The average passenger vehicle tire revolves at 800 times per mile or times per kilometer.

Referring now to Fig. 5, the movement between the bead 53 or shoulder of the tire and the tread 8 is one source of energy within the rotating tire. The compressor module 2 is preferably positioned on mount 3 near the bead or shoulder 53 of the tire 14. A bumper 4 is mounted on the inner tread 50 of the tire 14 so that it is positioned below the compressor module so as to come into contact with the piston when the tire is in an under inflated condition. Each time the tire rotates such that the area of the tire where the apparatus is mounted is in contact with the ground, the bumper depresses the piston expelling air out of the compressor module and into the tire.

An alternative embodiment is shown in Fig. 6. In this embodiment, the compressor module 60, which is of identical construction to that described above is mounted on a bridge or hoop 64 between the two beads 53 of the tire. The piston 62 would compress when contact is made with the inner tread 50. Preferably, the bridge or hoop is sufficiently flexible to allow for the installation of the tire on the rim and for inspection or repair of the tire casing but when in place in the mounted and inflated tire would have the rigidity and positioning to be the platform for the compressor module. Tires for sports utility vehicles, light to heavy trucks and trailers would be capable of using the same technology.

A further alternative embodiment is shown in Fig. 7. In this embodiment, the compressor module 70, which is of identical construction to that described above is mounted on module mount 74 anchored between the bead and tread 4 of the tire.
Directly opposite is the compressing module actuator 72 is mounted on a module mount 76 anchored between the bead and tread 8 of the tire. Module mounts 74 and 76 are preferably curved braces arcing away from the respective tire wall 16 it is mounted adjacent to. A decrease in the distance between the bead and tread results in compression of the module mounts 74 and 76 thereby forcing compressor module 70 and compressing module actuator towards each other. The piston 62 would compress when contact is made with the inner tread 50.

The mounting and size of the compressing module would vary with the profile, size and the recommended air pressure of the tire. The pressure regulating module would be clearly marked and matched to the tire or vehicle manufacturers recommended operating pressure and maximum inflation; for example, the pressure regulating module could be marked "36/44", meaning an optimum pressure of 36 PSI and a max pressure of 44 PSI. With such a rating, the tire inflation apparatus would operate until a pressure of 36 PSI is reached at which time it would become inoperative (by closing of the pressure regulating module as described above). Should the tire pressure reach 44 PSI, the tire inflation apparatus would operate to relieve pressure as described above. When mounted in an uncompressed tire, the head of the piston of the compressor (in its open position) is in abutment with the corresponding actuator.

The tire inflation apparatus 10 could be installed in a tire at the time of initial manufacture or prior to a tire being placed on a car. For installation of the tire inflation apparatus 10 on a current tire, the apparatus 10 would be installed at the time the tire is mounted. The dual purpose valve stem would fit in the standard valve opening as it is found on current vehicle wheels. The installation or mounting of the tire on the wheel would be the same as for current tires. In the case of a sidewall mounted module, the module would be mounted on the wall of the tire facing the center of the vehicle. The compressing module would be placed as close to the valve stem location on the wheel as possible. The balancing of the tire to offset the weight of the compressing module and related components would be with weights at one or two locations in the tire cavity, preferably mounted 120 degrees apart. Once mounted and inflated to the recommended pressure, the tire would be balanced either by static or dynamic methods as currently used.

Preferably, components mounted to the tire are attached using currently available adhesives. Should the tire inflation apparatus be attached during factory production, methods more adaptable to high production or by more cost effective means can be used. It is also contemplated that certain components, such as the bridge 64 of the alternative embodiment shown in Fig. 6 could be mounted in the tire by positioning between the tire bead and the wheel rim. Although designed for a specific tire casing, it would be independent from the tire itself.

Because the tire inflation apparatus 10 can be installed as an OEM item or installed when the tires are replaced on the vehicle, the technology of the tire inflation maintenance system (TIMS) would apply to all pneumatic tires used on our roadways.
The advantage of properly maintained tire pressure could cover all vehicles on the road within four to five years as existing vehicles tires are replaced as part of their normal life span.

It will be appreciated by those skilled in the art that the preferred and alternative embodiments have been described in some detail but that certain modifications may be practiced without departing from the principles of the invention.

Claims

What is claimed is:

1. A tire inflation device for inflating a tire to a set pressure comprising:

a compressor mountable within a tire in fluid communication with a pressure regulating module, said pressure regulating module in fluid communication with said compressor and with the atmosphere outside said tire;

said pressure regulator opening fluid communication between said compressor and said atmosphere when pressure within said tire drops below a set minimum;

and wherein said compressor being actuated by compression of said tire on an underlying surface during rotation while driving.